2010-03-20T12:02:37Z http://www.duo.uio.no/sok/oai-pmh.xml

oai:mic.1980.1.1 2010-03-20

eng Journal article 1980-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1980-1-1.asp Fulltext http://www.mic-journal.no/PDF/1980/MIC-1980-1-1.pdf Estimation of Synchronous Machine Parameters Hallingstad, Oddvar The present paper gives a short description of an interactive estimation program based on the maximum likelihood (ML) method. The program may also perform identifiability analysis by calculating sensitivity functions and the Hessian matrix. For the short circuit test the ML method is able to estimate the q-axis subtransient reactance x''q, which is not possible by means of the conventional graphical method (another set of measurements has to be used). By means of the synchronization and close test, the ML program can estimate the inertial constant (M), the d-axis transient open circuit time constant (T'do), the d-axis subtransient o.c.t.c (T''do) and the q-axis subtransient o.c.t.c (T''qo). In particular, T''qo is difficult to estimate by any of the methods at present in use. Parameter identifiability is thoroughly examined both analytically and by numerical methods. Measurements from a small laboratory machine are used. Maximum likelihood estimation, identifiability, short circuit measurement, transient stability model,

oai:mic.1980.1.2 2010-03-20

eng Journal article 1980-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1980-1-2.asp Fulltext http://www.mic-journal.no/PDF/1980/MIC-1980-1-2.pdf Stochastic Modelling and Self Tuning Control of a Continuous Cement Raw Material Mixing System Westerlund, T. Toivonen, Hannu T. Nyman, K-E The control of a continuously operating system for cement raw material mixing is studied. The purpose of the mixing system is to maintain a constant composition of the cement raw meal for the kiln despite variations of the raw material compositions. Experimental knowledge of the process dynamics and the characteristics of the various disturbances is used for deriving a stochastic model of the system. The optimal control strategy is then obtained as a minimum variance strategy. The control problem is finally solved using a self-tuning minimum variance regulator, and results from a successful implementation of the regulator are given. Stochastic modelling, self-tuning control, adaptive control, computer control, stochastic control, self-adjusting systems, cement industry,

oai:mic.1980.1.3 2010-03-20

eng Journal article 1980-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1980-1-3.asp Fulltext http://www.mic-journal.no/PDF/1980/MIC-1980-1-3.pdf Real-Time Failure-Detection and Identification Applied to Supervision of Oil Transport in Pipelines Digernes, Tørris In this paper methods for real-time failure detection and identification are discussed. The methods apply parallel filters of the Kalman type based on plant models that describe the different failure situations as well as normal operation. A failure is determined by identifying the filter having the highest probability of representing the plant. The tests are based on the innovation sequence produced each of the filters. The last section presents simulations from a system designed for supervision of oil transport in pipelines. Failure detection, failure identification, leakage detection and estimation, multiple hypothesis testing, chi-square test, likelihood ratio tests,

oai:mic.1980.1.4 2010-03-20

eng Journal article 1980-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1980-1-4.asp Fulltext http://www.mic-journal.no/PDF/1980/MIC-1980-1-4.pdf VOR - Calibration by an Airborne Integrated Navigation System Smestad, Tore A simulation study of a possible application of modern control theory is presented. The problem is to check and calibrate a VOR-station from a circling aircraft. An accurate position estimate of the circling aircraft is needed in order to calculate the errors in the received VOR-signals. The position estimate is here obtained from an integrated navigation system using an inertial navigation system (INS), a laser range-finder, angle measurements on the laser line-of-sight, and barometer readings. The range and angle measurements are fed to a Kalman filter which estimates errors in the navigation system. Simulation results show that satisfactory accuracy is obtained by this method. The paper presents a description of the proposed system, the simulation model used, simulation results and some sensitivity analysis. Avionics, VOR, calibration, inertial navigation, integrated navigation, Kalman filtering, sensitivity analysis,

oai:mic.1980.2.1 2010-03-20

eng Journal article 1980-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1980-2-1.asp Fulltext http://www.mic-journal.no/PDF/1980/MIC-1980-2-1.pdf Modeling and Identification of Marine Ecological Systems with Applications in Management of Fish Resources and Planning of Fisheries Operations Balchen, Jens G. No abstract

oai:mic.1980.2.2 2010-03-20

eng Journal article 1980-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1980-2-2.asp Fulltext http://www.mic-journal.no/PDF/1980/MIC-1980-2-2.pdf A Model of the Dynamics of Plankton Patchiness Ebenhöh, Wolfgang A mathematical model of the dynamics of plankton patchiness in the intermediate scale (1 km-10 km) was developed. Mechanisms that may be important in the creation and destruction of patches were selected and modelled. Such mechanisms are: horizontal turbulent diffusion, noise in the vertical turbulence, vertical migration of the zooplankton combined with a velocity profile and consumption of zooplankton by fish in schools. Patchiness is described by thc usc of the moments of density distributions, coherence lengths and correlations of phytoplankton and zooplankton. These parameters are investigated as functions of time and, also, for their dependence on the parameters of the patch creation mechanisms. Modelling, phytoplankton, zooplankton, patchiness, simulation, ecosystem, density distribution,

oai:mic.1980.2.3 2010-03-20

eng Journal article 1980-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1980-2-3.asp Fulltext http://www.mic-journal.no/PDF/1980/MIC-1980-2-3.pdf On the Problem of Identification in Compartment Analysis Aarnæs, Erik The present paper discusses how the impulse response of an unknown linear multi-compartment system can be used to identify the system and points out some of the problems associated with a unique identification. A method for system identification has been implemented in a computer program. Simulated data have been used to study the accuracy of the identification from the impulse response. Linear compartment system, identification, realization theory, Newton-Raphson method,

oai:mic.1980.2.4 2010-03-20

eng Journal article 1980-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1980-2-4.asp Fulltext http://www.mic-journal.no/PDF/1980/MIC-1980-2-4.pdf A Finite-Element Solution of the Navier-Stokes Equations for Two-Dimensional and Axis-Symmetric Flow Wille, Sven Ø. The finite element formulation of the Navier-Stokes equations is derived for two-dimensional and axis-symmetric flow. The simple triangular, T6, isoparametric element is used. The velocities are interpolated by quadratic polynomials and the pressure is interpolated by linear polynomials. The non-linear simultaneous equations are solved iteratively by the Newton-Raphson method and the element matrix is given in the Newton-Raphson form. The finite element domain is organized in substructures and an equation solver which works on each substructure is specially designed. This equation solver needs less storage in the computer and is faster than the traditional banded equation solver. To reduce the amount of input data an automatic mesh generator is designed. The input consists of the coordinates of eight points defining each substructure with the corresponding boundary conditions. In order to interpret the results they are plotted on a calcomp plotter. Examples of plots of the velocities, the streamlines and the pressure inside a two-dimensional flow divider and an axis-symmetric expansion of a tube are shown for various Reynolds numbers. Finite element method, blood flow,

oai:mic.1980.2.5 2010-03-20

eng Journal article 1980-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1980-2-5.asp Fulltext http://www.mic-journal.no/PDF/1980/MIC-1980-2-5.pdf Nuclear-Reaction Control by Multistage Mathematical-Programming Haugset, K. Leikkonen, I. The method of Multistage Mathematical Programming (MMP) has been adapted for optimal control of the spatial power distribution in nuclear reactors. Changes in power distribution arise from variations in the operational conditions of the reactor, and excite oscillations which in large reactors may approach the stability limit. Pressurized water reactor, optimal control, power distribution,

oai:mic.1980.3.1 2010-03-20

eng Journal article 1980-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1980-3-1.asp Fulltext http://www.mic-journal.no/PDF/1980/MIC-1980-3-1.pdf A Dynamic Positioning System Based on Kalman Filtering and Optimal Control Balchen, Jens G. Jenssen, Nils A. Mathisen, Eldar Sælid, Steinar This paper describes a computer-based, dynamic positioning system for floating vessels. The system is based on a detailed mathematical model of vessel motion in response to forces from thrusters, wind, waves and water current. The system uses a Kalman filter for optimal estimation of vessel motions and environmental forces from wind, waves and current. The control system is based on feedback from the motion variables where the oscillatory, wave-induced component is removed by the estimator. Feedback from the water current estimate provides the integral action of the system and feed forward from the wind force estimates are implemented. Simulation results and recordings from actual operation of the system indicate an excellent system performance. Dynamic positioning, Kalman filtering,

oai:mic.1980.3.2 2010-03-20

eng Journal article 1980-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1980-3-2.asp Fulltext http://www.mic-journal.no/PDF/1980/MIC-1980-3-2.pdf Analysis of Motion in Single-Point Mooring Systems Sørheim, Hans R. A mathematical model of the slow motions of ships in single-point moorings is described. The model is used for analysis of stability of equilibrium positions. An analytical criterion for stability relating main system parameters is derived under simplifying assumptions. A numerical example with a 100 000 dwt tanker showed that the effect of wind and current are of equal importance with respect to system stability, and astern propulsion is generally required to avoid stable oscillations. Stability problems in waves have not been found. The effects of time varying excitations are discussed and illustrated by simulation. Modelling, stability analysis, ship hydrodynamics, simulation,

oai:mic.1980.3.3 2010-03-20

eng Journal article 1980-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1980-3-3.asp Fulltext http://www.mic-journal.no/PDF/1980/MIC-1980-3-3.pdf A correction of a common error in truncated second order nonlinear filters Henriksen, Rolf A rederivation of the truncated second-order non-linear filter reveals that a significant error appears in previous derivations of this filter. What has previously been termed the modified truncated second-order filter will be shown to be, provided a small correction is made in the discrete-time case, the correct form of the truncated second-order filter. Estimation, non-linear filtering,

oai:mic.1980.4.1 2010-03-20

eng Journal article 1980-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1980-4-1.asp Fulltext http://www.mic-journal.no/PDF/1980/MIC-1980-4-1.pdf Slow Drift-Oscillations of a Ship in Irregular Waves Faltinsen, Odd M. Løken, Arne E. A procedure to calculate horizontal slow drift excitation forces on an infinitely long horizontal cylinder in irregular beam sea waves is presented. The hydrodynamic boundary-value problem is solved correctly to second order in wave amplitude. Results in the form of second order transfer functions are presented for different, two-dimensional shapes. It is concluded that Newman's approximative method is a practical way to calculate slow drift excitation forces on a ship in beam sea and it is suggested that it may be used in a more general case. Applications of the results for moored ships are discussed. Hydrodynamics, slowly varying wave forces, wave drift forces, strip theory, mooring,

oai:mic.1980.4.2 2010-03-20

eng Journal article 1980-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1980-4-2.asp Fulltext http://www.mic-journal.no/PDF/1980/MIC-1980-4-2.pdf CYPROS - Cybernetic Program Packages Tyssø, Arne CYPROS is an interactive program system consisting of a number of special purpose packages for simulation, identification, parameter estimation and control system design. The programming language is standard FORTRAN IV and the system is implemented on a medium size computer system (Nord-10). The system is interactive and program control is obtained by the use of numeric terminals. Output is rapidly examined by extensive use of video colour graphics. The subroutines included in the packages are designed and documented according to standardization rules given by the SCL (Scandinavian Control Library) organization. This simplifies the exchange of subroutines throughout the SCL system. Also, this makes the packages attractive for implementation by industrial users. In the simulation package, different integration methods are available and it can be easily used for off-line, as well as real time, simulation problems. The identification package consists of programs for single-input/single-output and multivariablc problems. Both transfer function models and state space models can be handled. Optimal test signals can be designed. The control package consists of programs based on multivariable time domain and frequency domain methods for analysis and design. In addition, there is a package for matrix and time series manipulation. CYPROS has been applied successfully to industrial problems of various kinds, and parts of the system have already been implemented on different computers in industry. This paper will, in some detail, describe the use and the contents of the packages and some examples of application will be discussed. Computer aided design, computer programming, interactive program,

oai:mic.1980.4.3 2010-03-20

eng Journal article 1980-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1980-4-3.asp Fulltext http://www.mic-journal.no/PDF/1980/MIC-1980-4-3.pdf On the Use of Low-Order Riccati-Equations in the Design of a Class of Feedback Controllers and State Estimators Solheim, Ole A. This paper describes a method for designing optimal feedback controllers with stability requirements using low-order Riccati equations. For originally stable systems the Riccati equation will be of first or second order, depending upon whether the eigenvalues are real or complex. For originally unstable systems the order of the Riccati equation will be equal to the number of eigenvalues with positive real part. Riccati equation, optimal control, pole placement,

oai:mic.1980.4.4 2010-03-20

eng Journal article 1980-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1980-4-4.asp Fulltext http://www.mic-journal.no/PDF/1980/MIC-1980-4-4.pdf A Multivariable Control in Aluminum Reduction Cells Gran, Erik The paper presents a multivariable control system for an aluminium reduction cell. The system is based on a dynamic model for the energy and mass balance. This model gives an optimal stationary state (or behavior) of the cell and is the basis of a reduced model which is used in calculation of the feedback control. Aluminium reduction cells, multivariable control, nonlinear model,

oai:mic.1981.1.1 2010-03-20

eng Journal article 1981-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1981-1-1.asp Fulltext http://www.mic-journal.no/PDF/1981/MIC-1981-1-1.pdf A Small Econometric-Model of Norway Henriksen, Rolf Thunem, Aage J. This paper presents a small model of the Norwegian economy which has been developed by the Division of Engineering Cybernetics at the Norwegian Institute of Technology. It was primarily designed to perform ex-post simulations of the overall behaviour of the economy during the period 1968 77. The experiments show that a cut in central government income taxes might have strengthened the economy significantly without increasing inflation. They thus indicate that a high level of personal income taxation, as in Norway today, may be highly inflationary, as opposed to what is asserted in many textbooks. Econometrics, mathematical modelling, identification,

oai:mic.1981.1.2 2010-03-20

eng Journal article 1981-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1981-1-2.asp Fulltext http://www.mic-journal.no/PDF/1981/MIC-1981-1-2.pdf ENOR - An Energy-Model for Norway Ek, A. Kolberg, T. Sira, Terje The Energy model for Norway, ENOR, is a dynamic, multisectoral economic stimulation model to be used for long term energy analyses. Energy sectors and energy carriers are in principle treated in the same way as other sectors and economic commodities and integrated in the same general framework. The model has a two-level structure - a central coordination module ensures economic consistency, while the behaviour of each production and consumption sector is modelled in separate sector models. The model framework is thus capable of handling both engineering and economic knowledge. Energy, econometrics, dynamic stimulation model,

oai:mic.1981.1.3 2010-03-20

eng Journal article 1981-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1981-1-3.asp Fulltext http://www.mic-journal.no/PDF/1981/MIC-1981-1-3.pdf An Implementation of Estimation Techniques to a Hydrological Model for Prediction of Runoff to a Hydroelectric Power-Station Fjeld, Magne Aam, Sverre Parameter and state estimation algorithms have been applied to a hydrological model of a catchment area in southern Norway to yield improved control of the household of water resources and better economy and efficiency in the running of the power station, as experience proves since the system was installed on-line in the summer of 1978. State estimation, parameter estimation, Nordic hydrological model, run-off prediction,

oai:mic.1981.2.1 2010-03-20

eng Journal article 1981-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1981-2-1.asp Fulltext http://www.mic-journal.no/PDF/1981/MIC-1981-2-1.pdf On Ultrasonic MTI Measurement of Velocity Profiles in Blood-Flow Angelsen, Bjørn A.J. Kristoffersen, Kjell A theoretical analysis of Doppler frequency estimators proposed to be used in ultrasonic MTI measurements of velocity profiles in blood flow, is given. The estimators give an output in form of a single analogue voltage and the relation of the output to the Doppler spectrum is discussed. Three new estimators are also proposed. All estimators work fairly well for narrow-band Doppler spectra, but errors are found when broad-band spectra are present. Ultrasound, doppler effect, blood flow,

oai:mic.1981.2.2 2010-03-20

eng Journal article 1981-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1981-2-2.asp Fulltext http://www.mic-journal.no/PDF/1981/MIC-1981-2-2.pdf Pressure and flow in arterial aneurysms simulated in mathematical models Wille, Sven Ø. In this work pressure and flow patterns inside two kinds of axis symmetric aneurysms are presented under steady flow conditions. The results are obtained by solving the axi-symmetric formulation of the non-linear Navier-Stokes equations. Finite element method, blood flow, aneurysms,

oai:mic.1981.2.3 2010-03-20

eng Journal article 1981-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1981-2-3.asp Fulltext http://www.mic-journal.no/PDF/1981/MIC-1981-2-3.pdf Instability of a Uniform Plankton Distribution Ebenhöh, Wolfgang For a plankton model system, a horizontally uniform distribution becomes unstable if the zooplankton component carries out diurnal vertical migrations in an ocean with a speed difference between the currents in upper and lower waterlaycrs. With turbulent diffusion included in the model, the instability occurs beyond a threshold speed difference. A numerical estimation of the threshold and of the critical patch size gives reasonable values. Modelling, phytoplankton, zooplankton, patchiness, spatial distribution, stability, turbulent diffusion,

oai:mic.1981.2.4 2010-03-20

eng Journal article 1981-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1981-2-4.asp Fulltext http://www.mic-journal.no/PDF/1981/MIC-1981-2-4.pdf Pressure Transients and Control in Liquid Propane Caverns Asbjørnsen, O.A. Aas, P.H. Hancke, J. This paper shows how a very simple model of the process dynamics of a LPG cavern may be developed, and demonstrates the applicability of this model. The model is used to simulate the consequences of malfunctioning control equipment during loading of the cavern, to design a simple feed forward control strategy for the feed temperature and to estimate the model parameters from real plant experiments. From these experiments the heat transfer from the vapor phase to the rock and the heat conductivity of the rock itself are estimated. The parameters so obtained are plausible and may be used for further simulations or design and evaluation of similar caverns. The results of the model fitting show that the material balance is accurate within less than 1% while the energy balance is accurate to withon 0.07oC or about 3% of the peak value of the temperature transient during loading. Process modelling, process simulation, parameter estimation,

oai:mic.1981.2.5 2010-03-20

eng Journal article 1981-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1981-2-5.asp Fulltext http://www.mic-journal.no/PDF/1981/MIC-1981-2-5.pdf On the Use of a Block Analog of the Gerschgorin Circle-Theorem in the Design of Decentralized Control of a Class of Large-Scale Systems Solheim, Ole A. The paper deals with the design of decentralized control of interconnected dynamic systems. It is assumed that each subsystem has its own control input and that the interconnections are through the states of the other subsystems. The purpose of the present paper is to investigate the possibility of using the so-called block Gerschgorin theorem to evaluate the stability of the total system, given the local controllers. This theorem enables us to determine inclusion regions for the eigenvalues of the total system and these regions are usually sharper than those obtained by the usual Gerschgorin circle theorem. Decentralized control, decentralized estimation, eigenvalues, stability,

oai:mic.1981.3.1 2010-03-20

eng Journal article 1981-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1981-3-1.asp Fulltext http://www.mic-journal.no/PDF/1981/MIC-1981-3-1.pdf Modeling and Simulation of Physiology and Population-Dynamics of Copepods - Effects of Physical and Biological Parameters Slagstad, Dag A detailed model of the physiology and vertical migration behaviour of marine copepods of the ca/anus is developed. A two-dimensional population model calculates the size and developmental structure of the population in relation to its own dynamics and the environment. Examination of the effect on the population dynamics and production of copepods by changing the physical and biological parameters is performed. Modeling, phytoplankton, zooplankton, copepods, ecosystem, population dynamics,

oai:mic.1981.3.2 2010-03-20

eng Journal article 1981-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1981-3-2.asp Fulltext http://www.mic-journal.no/PDF/1981/MIC-1981-3-2.pdf The Impact of Phosphorus Load and Water Through-Flow on Phytoplankton Standing Crop in a Dimitic Lake Seip, Knut L. A mathematical model has been developed for the mesotrophic Lake Mjesa (365 x 106 m2, 61' N, 11° E). Emphasis has been made on the interaction between biological and hydrodynamic variables. Simulation results for phytoplankton and nutrient concentrations in both the epilimnion and the hypolimnion compare fairly well with observations. Investigative simulations have been made to study the effects of injecting nutrients at different depths assuming three alternative schemes for diffusion across the thermoclinc. The overall results indicate that the phytoplankton standing crop is less sensitive to nutrient injection depths when diffusion increases, and that the high efficiency of hypolimnetic injection reported for some lakes in the literature will not be obtained in the present lake. Simulation studies of changes in river flow indicate that changes in peak flow time (inside the domain of natural variability) have a greater impact on the phytoplankton standing crop ( less than 20%) than changes in flow volume ( less than 6%). Simulations also indicate that light extinction caused by suspended particles associated with river flow may be important in sections of the lake. Phosphorus, phytoplankton, eutrophication, ecosystem, lake, management, modelling,

oai:mic.1981.4.1 2010-03-20

eng Journal article 1981-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1981-4-1.asp Fulltext http://www.mic-journal.no/PDF/1981/MIC-1981-4-1.pdf Efficient numerical simulation of ocean hydrodynamics by a splitting procedure Berntsen, Hans Kowalik, Zygmunt Sælid, Steinar Sørli, Karstein A splitting algorithm for fast and slow modes of ocean hydrodynamics is presented. The purpose of the splitting is to reduce the large amount of computational work needed for simulating long real-time periods. The essential point of the splitting is that the external gravity wave terms are extracted from the fully three-dimensional equations of horizontal motion, allowing the reduced equations to be integrated with a larger time step than the original model. The fast external gravity waves are traced by a depth integrated system which is weakly coupled to the reduced three-dimensional momentum equations. The split model shows a radical decrease in computational time and the accuracy is of the same order as in the non-split case. Physical oceanography, numerical modeling, fast and slow modes, splitting, efficiency, accuracy,

oai:mic.1981.4.2 2010-03-20

eng Journal article 1981-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1981-4-2.asp Fulltext http://www.mic-journal.no/PDF/1981/MIC-1981-4-2.pdf A Study of the M-2 Tide in the Ice-Covered Arctic Ocean Kowalik, Zygmunt A model to study M2 tide propagation in the Arctic Ocean based on the equation of motion of the water and the pack ice, is considered. The mechanics of the ice floe interaction is described by the non-linear viscous constitutive loaw. Various empirical parameters entering the constitutive law are checked against the tide-induced motion of the pack ice. The distribution of the amplitude, phase, current ellipse in the ice-free and the ice-covered Arctic Ocean is computed and presented in figures. Special attention is given to clarifying the distribution and peculiarities of tide propagation in the Barents Sea. The tide-induced motion of the pack ice has been studied carefully; numerous experiments show that residual (over tidal period) ice drift is observed due to the non-linear ice floe interaction. It is found that both residual ice drift and periodical ice motion may lead to ice redistribution, setting the areas of ice convergence and divergence. Hydrodynamics, M2 tide, ice mechanics, numerical methods, Arctic ocean,

oai:mic.1981.4.3 2010-03-20

eng Journal article 1981-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1981-4-3.asp Fulltext http://www.mic-journal.no/PDF/1981/MIC-1981-4-3.pdf A Theoretical-Study of the Scattering of Ultrasound from Blood Angelsen, Bjørn A.J. A theoretical treatment of the scattering of ultrasound from blood is given, assuming that the blood behaves essentially as a continuum. The scattering then arises from fluctuations in the mass density and compressibility of the blood, which is caused by a fluctuation in the red cell concentration. An expression for the received signal in ultrasonic blood velocity measurements is given. The stochastic properties of the signal are discussed with reference the information content about the velocity field in the blood. Since the signal is Gaussian, all available information is contained in the power spectrum, which is a blurred approximation to the velocity distribution in the region of observation. Ultrasound scattering, Doppler effect,

oai:mic.1982.1.1 2010-03-20

eng Journal article 1982-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1982-1-1.asp Fulltext http://www.mic-journal.no/PDF/1982/MIC-1982-1-1.pdf The Defense of a Valuable Target - A Control Theoretical Analysis Mjelde, Kåre M. A problem is considered of the defence of a valuable target against enemy attacks, such as to minimize the total number of successful attacks during a given period of time. Defence weapons are allocated to: Control theory, defence analysis,

oai:mic.1982.1.2 2010-03-20

eng Journal article 1982-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1982-1-2.asp Fulltext http://www.mic-journal.no/PDF/1982/MIC-1982-1-2.pdf Optimal Co-Generation in an Integrated Kraft Mill Suh, S. Olsen, T.O. An optimal control system designed to minimize the consumption of high pressure steam (and thus minimizing energy costs) while meeting the paper mill's demand for process steam and electric power is developed. An installation example is described and system performance and benefits are discussed. It should be noted that the theories developed in this paper can be readily extended to the design of an optimal control system which maximizes the electric generation under the given inlet steam flow. Optimization, cogeneration, kraft, modeling, identification, control, linear programming, recursive, turbine-generators,

oai:mic.1982.1.3 2010-03-20

eng Journal article 1982-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1982-1-3.asp Fulltext http://www.mic-journal.no/PDF/1982/MIC-1982-1-3.pdf Real-Time Simulation of Oil Drilling Operations Opdal, Jørgen This paper contains the basic numeric model for the oil drilling simulator WELLSIM. As a case study it presents an example from well pressure control. Figure 1 shows a picture of the simulator. Oil drilling, numeric modeling,

oai:mic.1982.1.4 2010-03-20

eng Journal article 1982-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1982-1-4.asp Fulltext http://www.mic-journal.no/PDF/1982/MIC-1982-1-4.pdf A Liquid Cargo Handling Training Simulator Villabø, Malvin This paper describes a computer-based, real-time training simulator for liquid cargo handling. The mathematical model description is modular and emphasizes the flow generating part. The flow model applies network theory to describe the logical piping connections and the overall flow system performance, while Bernoulli's equation is used for the description of the piping elements. Numerically the Newton-Raphson method is applied for computation of the non-linear flow model. The programming language is HP-FORTRAN IV and the simulator is implemented on an HP minicomputer system. The instructor part of the system is interactive and controlled by the use of a standard ASCII terminal. The simulation part of the system is running in real-time or scaled real-time, and is controlled from the trainee's panel. Simulator, training, liquid cargo handling,

oai:mic.1982.1.5 2010-03-20

eng Journal article 1982-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1982-1-5.asp Fulltext http://www.mic-journal.no/PDF/1982/MIC-1982-1-5.pdf The Cost Problem According to Standard Theory - A Critical Note Nilsson, Jan-Evert Kalgraf, Kjell This paper examines and criticizes the standard theoretical basis for the argument that a cost-oriented government policy is necessary if a country with a high-cost problem is to improve its competitive powers. According to theory, a firm can only deal with a long-term high-cost problem by increasing its productivity. In attempting to increase productivity, the firm will encounter two problems: Economic theory, international competition,

oai:mic.1982.2.1 2010-03-20

eng Journal article 1982-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1982-2-1.asp Fulltext http://www.mic-journal.no/PDF/1982/MIC-1982-2-1.pdf A Multidimensional Continuum Model of Fish Population Dynamics and Behaviour: Application to the Barents Sea Capelin (Mallotus Villosus) Reed, Mark Balchen, Jens G. The theoretical basis for a fishery model continuous in physical, temporal, and biological dimensions is discussed. A concrete application, constructed as one component of a larger system of physical and biological dynamic models descriptive of the Barents Sea ecosystem, is presented. Some of the potentials of such an approach are demonstrated through an example simulation of population dynamics. Simple parameterizations of other components of the ecosystem (ocean currents, temperature, sea ice, cod, marine mammals, the fishing fleet, copepods, and krill) are used to provide an ersatz environment in which to perform simulation tests. Capelin, fishery dynamics, fish populations, population dynamics, ecosystem modeling, fish migration, fish behaviour,

oai:mic.1982.2.2 2010-03-20

eng Journal article 1982-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1982-2-2.asp Fulltext http://www.mic-journal.no/PDF/1982/MIC-1982-2-2.pdf A Model of Phytoplankton Growth - Effects of Vertical Mixing and Adaptation to Light Slagstad, Dag The OCEAN BIO-MODELS Project is a long term research and development programme whose goal is to establish the capability of producing mathematical/numerical models of a marine ecosystem of the Barents Sea, north of Norway. The system is modeled by a set of submodels describing the physical oceanography, chemical oceanography and production and distribution of phytoplankton, zooplankton and fish. In this paper, a phytoplankton model containing light adaptation properties is developed. Modeling, phytoplankton, adaptation, ecosystem, simulation,

oai:mic.1982.3.1 2010-03-20

eng Journal article 1982-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1982-3-1.asp Fulltext http://www.mic-journal.no/PDF/1982/MIC-1982-3-1.pdf Stochastic Seasonal Planning in Multireservoir Hydroelectric Power Systems by Differential Dynamic Programming Gjelsvik, Anders A first-order differential dynamic programming (DDP) algorithm is used for computing optimal control for a five-reservoir system, where the stochastic inflow process has been approximated by a few discrete disturbance values in each time step. The method is found to be faster than linear programming, previously tried on the same system model. Power system, water resources, stochastic optimization, incremental water value, differential dynamic programming,

oai:mic.1982.3.2 2010-03-20

eng Journal article 1982-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1982-3-2.asp Fulltext http://www.mic-journal.no/PDF/1982/MIC-1982-3-2.pdf Implementation of a Load Prediction Program System for the Norwegian Power Pool Aam, Sverre Skarstein, Øyvin Gagnat, L. A model for short-term load prediction (24 hours) has been developed. It is implemented as a part of an interactive program system for load prediction within the different areas of the Norwegian Power Pool. The model consists of two parts, describing the slow, seasonal variations (normal conditions), and short-term deviations from normal conditions, respectively. Kalman filtering techniques are used for updating the states of the models, and the parameters are estimated with a maximum likelihood method. The model has been tested with load data from various areas in Norway, and the system has been in on-line use at the Norwegian Power Pool since October 1979. Better control of the power system has been obtained through improved prediction and production planning. Power system control, load prediction, parameter estimation, Kalman filters,

oai:mic.1982.3.3 2010-03-20

eng Journal article 1982-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1982-3-3.asp Fulltext http://www.mic-journal.no/PDF/1982/MIC-1982-3-3.pdf Multivariable Feedback Control of Nuclear Reactors Moen, Rune Multivariable feedback control has been adapted for optimal control of the spatial power distribution in nuclear reactor cores. Two design techniques, based on the theory of automatic control, were developed: the State Variable Feedback (SVF) is an application of the linear optimal control theory, and the Multivariable Frequency Response (MFR) is based on a generalization of the traditional frequency response approach to control system design. Nuclear reactor, multivariable feedback control,

oai:mic.1982.4.1 2010-03-20

eng Journal article 1982-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1982-4-1.asp Fulltext http://www.mic-journal.no/PDF/1982/MIC-1982-4-1.pdf A Mathematical Model for Dynamic Analysis of a Flexible Marine Riser Connected to a Floating Vessel Otteren, Audun A mathematical model for simulation of a flexible marine riser connected to a floating vessel is presented. The model is used for dynamic analysis of marine operations which include a riser and a floating vessel. The riser can be freely hanging from the vessel or fixed at the bottom. The vessel can be freely floating, moored by anchors or dynamically positioned. The performance of the riser model is evaluated by a comparison with results from a simulation study published by the American Petroleum Institute. Finally, a complete three dimensional, irregular sea-state analysis is presented to illustrate some of the capabilities of the simulation concept. Mathematical modeling, hydrodynamics, flexible riser, floating vessel, marine operations,

oai:mic.1982.4.2 2010-03-20

eng Journal article 1982-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1982-4-2.asp Fulltext http://www.mic-journal.no/PDF/1982/MIC-1982-4-2.pdf Optimal Evasive Maneuver for a Ship in an Environment of Fixed Installations and Other Ships Skjong, Rolf Mjelde, Kåre M. Collision avoidance for encounters between several ships and installations in the open sea, is treated as a problem of optimal control, using the theory of differential games. Each ship is, in this idealized model, assumed to have two controls corresponding to rudder angle and engine setting. The objective function, which the shipmasters try to minimize in an optimal evasive manoeuvre, is defined as the collision risk. Numerical solutions for the M-ships and I-installations optimal evasive manoeuvre problem, can be found by the ping-pong algorithm. Numerical examples are given for up to five ships and two installations. Optimal control, differential game, offshore, ship, collision,

oai:mic.1982.4.3 2010-03-20

eng Journal article 1982-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1982-4-3.asp Fulltext http://www.mic-journal.no/PDF/1982/MIC-1982-4-3.pdf Compounding the Losses of Convoyed Ships Attacked by Tactical Submarines Mjelde, Kåre M. It is demonstrated that a time dependent stochastic model for the losses of convoyed ships attacked by submarines can be applied in the determination of the losses in terms of the results of two submodels: Defense analysis, differential games,

oai:mic.1982.4.4 2010-03-20

eng Journal article 1982-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1982-4-4.asp Fulltext http://www.mic-journal.no/PDF/1982/MIC-1982-4-4.pdf A Model for Solving the Maxwell Quasi Stationary Equations in a 3-Phase Electric Reduction Furnace Ekrann, S. Sira, Terje A computer code has been developed for the approximate computation of electric and magnetic fields within an electric reduction furnace. The paper describes the numerical methods used to solve Maxwell's quasi-stationary equations, which are the governing equations for this problem. The equations are discretized by a staggered grid finite difference technique. The resulting algebraic equations are solved by iterating between computations of electric and magnetic quantities. This 'outer' iteration converges only when the skin depth is larger or of about the same magnitude as the linear dimensions of the computational domain. In solving for electric quantities with magnetic quantities being regarded as known, and vice versa, the central computational task is the solution of a Poisson equation for a scalar potential. These equations are solved by line successive overrelaxation combined with a rebalancing technique. Maxwells quasi-stationary equations, electric and magnetic fields, three-dimensional, numerical methods, finite differences, staggered grid,

oai:mic.1983.1.1 2010-03-20

eng Journal article 1983-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1983-1-1.asp Fulltext http://www.mic-journal.no/PDF/1983/MIC-1983-1-1.pdf GPS Performance in Marine Applications Bardal, Johnny Ørpen, Ole This paper presents simulations of Global Positioning System (GPS) receiver performance for marine applications. An overview of the GPS system along with a detailed description of the GPS receiver Kalman filter implementation is given. Also presented is a description of ship behaviour in a seaway. The end of the paper presents a few selected simulation results giving the performance of a GPS receiver for marine applications. Satellite navigation, Kalman filters, digital simulation,

oai:mic.1983.1.2 2010-03-20

eng Journal article 1983-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1983-1-2.asp Fulltext http://www.mic-journal.no/PDF/1983/MIC-1983-1-2.pdf Resource Allocation by Convex Monotonous Programming Application to an Otec Energy Production Platform Mjelde, Kåre M. Fjeld, S. A problem is considered of the minimization of a convex and monotonically increasing cost function subject to an upper bound of a convex and monotonically decreasing failure probability function. An algorithm is defined for the parametrical solution of the problem with respect to the selected failure probability level; the algorithm is applicable to problems with cost and failure probability functions that are not necessarily separable, thus extending a previously given algorithm for separable functions. A condition is given for the relaxation of the convexity assumption on the functions, and it is observed that the problem of the minimization of the failure probability subject to an upper bound on the total cost is solved simultaneously with the given problem. An anlytically solvable numerical example is given and an application to the optimization of an OTEC energy production platform is briefly described, with reference to a complete description; it is concluded that the given extension of the algorithm to non-convex functions is important in this application. Resource allocation, non-linear programming, convex programming,

oai:mic.1983.1.3 2010-03-20

eng Journal article 1983-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1983-1-3.asp Fulltext http://www.mic-journal.no/PDF/1983/MIC-1983-1-3.pdf Adaptive ship autopilot with wave filter Sælid, Steinar Jenssen, Nils A. This paper is concerned with analysis and design of an adaptive autopilot for ships. The design is based on a low and high frequency model of the vessel motion adequate to ship steering. The low frequency model describes the vessel response to rudder control and slowly varying environmental forces. The high frequency model represents the wave induced oscillatory part of the yaw motion. The models are used in a Kalman filter and the rudder control is computed from linear quadratic theory based on the low frequency part of the vector. This yields a very effective filtering of the wave component of the yaw motion. Proper operation of this filter/controller structure requires knowledge of the vessel model parameters and the dominating wave frequency. The vessel parameters are estimated on line by a recursive prediction error method. In order to reduce the computing requirements, the state estimator is operated using scheduled gains. This results in an easy and robust design. The convergence properties are investigated by using the method of Ljung. The performance is confirmed by simulation experiments. Adaptive control, wave filter, convergence analysis,

oai:mic.1983.1.4 2010-03-20

eng Journal article 1983-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1983-1-4.asp Fulltext http://www.mic-journal.no/PDF/1983/MIC-1983-1-4.pdf Disturbance Error Reduction in Multivariable Optimal Control Systems Solheim, Ole A. Stenhaug, Ulf The paper deals with the design of optimal multivariable controllers, using a modified LQR approach. All controllers discussed contain proportional feedback and, in addition, there may be feedforward, integral action or state estimation. Multivariable control systems, optimal control, state estimation, feedback, feedforward,

oai:mic.1983.2.1 2010-03-20

eng Journal article 1983-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1983-2-1.asp Fulltext http://www.mic-journal.no/PDF/1983/MIC-1983-2-1.pdf An Adaptive Multivariable Control System for Hydroelectric Generating Units Hegglid, Gunne J. This paper describes an adaptive multivariable control system for hydroelectric generating units. The system is based on a detailed mathematical model of the synchronous generator, the water turbine, the exiter system and turbine control servo. The models of the water penstock and the connected power system are static. These assumptions are not considered crucial. The system uses a Kalman filter for optimal estimation of the state variables and the parameters of the electric grid equivalent. The multivariable control law is computed from a Riccatti equation and is made adaptive to the generators running condition by means of a least square technique. Adaptive control, multivariable systems, hydroelectric generating units,

oai:mic.1983.2.2 2010-03-20

eng Journal article 1983-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1983-2-2.asp Fulltext http://www.mic-journal.no/PDF/1983/MIC-1983-2-2.pdf Multivariable controller for discrete stochastic amplitude-constrained systems Toivonen, Hannu T. A sub-optimal multivariable controller for discrete stochastic amplitude-constrained systems is presented. In the approach the regulator structure is restricted to the class of linear saturated feedback laws. The stationary covariances of the controlled system are evaluated by approximating the stationary probability distribution of the state by a gaussian distribution. An algorithm for minimizing a quadratic loss function is given, and examples are presented to illustrate the performance of the sub-optimal controller. Control non-linearities, discrete-time systems, non-linear systems, optimal control, saturation,

oai:mic.1983.2.3 2010-03-20

eng Journal article 1983-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1983-2-3.asp Fulltext http://www.mic-journal.no/PDF/1983/MIC-1983-2-3.pdf How to Drive a Delayed Response, Stochastic System Close to Equilibrium Flåm, Sjur D. We consider a continuous system that, in the absence of random perturbations and external forcing, is uniformly, asymptotically stable in a global sense. The system evolution is governed by a retarded differential equation. To this equation is added unidentified, time- and state-dependent noise. However, in each instance the noise is bounded over the probability space. We demonstrate that approximate stability is obtainable by a deterministic approach based on worst case analysis. Stability, control, stochastic system,

oai:mic.1983.2.4 2010-03-20

eng Journal article 1983-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1983-2-4.asp Fulltext http://www.mic-journal.no/PDF/1983/MIC-1983-2-4.pdf A War of Area Attrition and Aimed Attack Properties of Optimal Strategies Mjelde, Kåre M. A war is considered of the attrition of the enemy's weapons supply system or the attack of his forces in the battle area. The rate of weapons supply of each side depends on the total number of successful attrition allocations of the other side; this dependency is described by a decreasing and differentiable function. The attack allocations are aimed at specific targets, while the attrition allocations are randomly distributed over the area in which the supply operations take place. The theory of differential games is applied to derive properties of optimal solutions. Defence analysis,

oai:mic.1983.2.5 2010-03-20

eng Journal article 1983-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1983-2-5.asp Fulltext http://www.mic-journal.no/PDF/1983/MIC-1983-2-5.pdf Optimal Load Allocation Andreassen, Ø. Olsen, Thor O. An algorithm for optimal boiler load allocation is compared with a sub-optimal algorithm and with equal load distribution. Advantages and disadvantages of the optimal and sub-optimal algorithms are discussed, and by a practical example it is demonstrated that the optimal algorithm may give substantial cost reductions. Boiler load allocation, optimization, sub-optimal solutions,

oai:mic.1983.2.6 2010-03-20

eng Journal article 1983-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1983-2-6.asp Fulltext http://www.mic-journal.no/PDF/1983/MIC-1983-2-6.pdf Componentwise Fractional Programming with Application to Resource Allocation Mjelde, Kåre M. A fractional programming problem is considered of the maximization of the ratio of a concave and a convex function, with each variable occurring in a single convex component constraint. A componentwise solution algorithm is given; each component-problem being defined by a weighted difference of thc,concave and the convex functions of the given fractional objective function; the relative weight being recalculated after each componentwise optimization. Fractional programming, non-linear programming, componentwise programming, resource allocation,

oai:mic.1983.3.1 2010-03-20

eng Journal article 1983-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1983-3-1.asp Fulltext http://www.mic-journal.no/PDF/1983/MIC-1983-3-1.pdf Simulation of a Sponge Iron Production Process Onshus, Tor A model for reduction of FeO with hydrogen in a countercurrent moving bed reactor is summarized. This model is a special case of a mor ecomplete model which also includes reduction of the higher oxides, hematite and magnetite, with a mixture of reducing gases, thus describing the production of direct-reduced iron from iron ores. Equations governing the heat and mass transfer between the gas and solid phase are not given here, but play an important role in the dynamic bahviour of the model. Sponge iron, shaft furnace, simulation,

oai:mic.1983.3.2 2010-03-20

eng Journal article 1983-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1983-3-2.asp Fulltext http://www.mic-journal.no/PDF/1983/MIC-1983-3-2.pdf Partitioning and Tearing of Networks Applied to Process Flowsheeting Gundersen, Truls Hertzberg, Terje A review of the methods available for identification of the computational sequence in modular process simulators (partitioning and tearing) is followed by the presentation of a new very efficient and close-to-optimal routine for tearing. The problem of partitioning can be solved in computer times that are linear functions of the number of unit modules (vertices in the graph). The algorithm of Johns has been found to execute faster than the later and far better known algorithm of Tarjan. These methods are almost identical in idea but use different techniques in the book-keeping. Decomposition, graph theory, process flowsheeting,

oai:mic.1983.3.3 2010-03-20

eng Journal article 1983-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1983-3-3.asp Fulltext http://www.mic-journal.no/PDF/1983/MIC-1983-3-3.pdf Properties of Pareto Optimal Allocations of Resources to Activities Mjelde, Kåre M. A linear multi-objective decision problem is considered, of the maximization of the effect of allocations of resources to activities. Necessary and sufficient conditions for a feasible solution to the problem to be Pareto-optimal are derived, in terms of properties of the allocation matrix and a certain matrix of efficiency coefficients of the allocations. A condition is given for all optimal solutions to be simple in the sense that they contain a small number of non-zero allocations. A feasible change of the positive allocations of an optimal solution produces a new optimal solution. Resource allocation,

oai:mic.1983.3.4 2010-03-20

eng Journal article 1983-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1983-3-4.asp Fulltext http://www.mic-journal.no/PDF/1983/MIC-1983-3-4.pdf Parameter Estimation of Ship Manoeuvring Equations Flobakk, Tore Model tests performed at the Norwegian Hydrodynamic Laboratories (NHL), to identify ship manoeuvring equations, are described. Parameter estimation techniques are used to determine the mathematical model. Parameter estimation, hydrodynamics,

oai:mic.1983.4.1 2010-03-20

eng Journal article 1983-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1983-4-1.asp Fulltext http://www.mic-journal.no/PDF/1983/MIC-1983-4-1.pdf Composition control of a binary distillation column using multivariable optimal control Foss, Bjarne A. This article discusses dual composition control of binary distillation columns subjected to feed disturbances. A simulation model is established and some of its characteristics are discussed. Binary distillation columns, modeling, dual composition control,

oai:mic.1983.4.2 2010-03-20

eng Journal article 1983-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1983-4-2.asp Fulltext http://www.mic-journal.no/PDF/1983/MIC-1983-4-2.pdf Optimality in Infinite Horizon Discrete Time Models of Resource Management Flåm, Sjur D. We study an infinite horizon discrete time optimization problem of the Bolza type. It is argued that this problem arises frequently in models of resource management. We obtain a characterization of optimality which is an analog to the Euler equation. The results extend those of Rockafellar and Wets (1981). Furthermore, we make no assumption about free disposal and absorbing states. Optimization,

oai:mic.1983.4.3 2010-03-20

eng Journal article 1983-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1983-4-3.asp Fulltext http://www.mic-journal.no/PDF/1983/MIC-1983-4-3.pdf Robustness Analysis of a Class of Optimal Control Systems Solheim, Ole A. This paper deals with a class of optimal control systems, where the controller. in addition to minimizing a quadratic criterion, also shall give the closed-loop system prescribed eigenvalues. Three methods for analysing the robustness of such systems under parameter perturbations are discussed: Eigenvalue sensitivity, singular values and the block Gerschgorin theorem. Numerical examples are presented to illustrate the different methods. Optimal control systems,

oai:mic.1983.4.4 2010-03-20

eng Journal article 1983-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1983-4-4.asp Fulltext http://www.mic-journal.no/PDF/1983/MIC-1983-4-4.pdf Project Evaluation and Cash Flow Forecasting by Stochastic Simulation Asbjørnsen, Odd A. The net present value of a discounted cash flow is used to evaluate projects. It is shown that the LaPlace transform of the cash flow time function is particularly useful when the cash flow profiles may be approximately described by ordinary linear differential equations in time. However, real cash flows are stochastic variables due to the stochastic nature of the disturbances during production. Stochastic, cash flow, simulation, project evaluation,

oai:mic.1984.1.1 2010-03-20

eng Journal article 1984-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1984-1-1.asp Fulltext http://www.mic-journal.no/PDF/1984/MIC-1984-1-1.pdf Design and Implementation of an Online Estimation for a Rougher Flotation Process Henriksen, Rolf Olsen, Thor O. The problem of estimating grades and flotation parameters in a bank of flotation cells is investigated. From extensive simulation studies with both single-cell and multi-cell processes, an estimator based on an aggregate model of the bank is developed to estimate concentrate grades and aggregate flotation parameters. Specific results from the estimator's performance in a real flotation plant are reported. Flotation processes, on-line estimation, non-linear filtering, identification,

oai:mic.1984.1.2 2010-03-20

eng Journal article 1984-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1984-1-2.asp Fulltext http://www.mic-journal.no/PDF/1984/MIC-1984-1-2.pdf Multivariable adaptive control Toivonen, Hannu T. In recent years there has been an extensive interest in adaptive and self-tuning controllers, and there is a vast literature on various adaptive algorithms. The purpose of the present paper is to review some common approaches for multi-variable adaptive control. The presentation concentrates on procedures which are based on stochastic controller design methods, but some close connections with other design techniques are also indicated.

oai:mic.1984.1.3 2010-03-20

eng Journal article 1984-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1984-1-3.asp Fulltext http://www.mic-journal.no/PDF/1984/MIC-1984-1-3.pdf General Analysis of Directional Ocean Wave Data from Heave Pitch Roll Buoys Barstow, Stephen F. Krogstad, Harald E. Directional ocean wave data is usually analysed using the so-called linear model of the sea surface, but experience has shown that the results may deviate substantially from the predictions of the theory, in particular in the high frequency range. A general theory is presented here which includes the linear model as a special case. Properties of commonly used parameters under the influence of currents and non-linearities are easily explained within the general theory. Some results from the NORWAVE heave/pitch/roll data buoy operated offshore Norway are also presented. Ocean waves, wave analysis, buoy measurements,

oai:mic.1984.2.1 2010-03-20

eng Journal article 1984-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1984-2-1.asp Fulltext http://www.mic-journal.no/PDF/1984/MIC-1984-2-1.pdf General Analysis of Directional Ocean Wave Data from Heave Pitch Roll Buoys Wiberg, Donald M. Baskin, Fred Lindsay, R.D. There are many practical applications of lattice form recursive linear least square algorithms (called lattices for short) in signal processing, communications, and control systems. The goal of this tutorial is to help practicing engineers to decide if lattices are appropriate for their particular projects. Lattices, least squares, recursive estimation, digital filtering, signal processing, communications, control systems, noise cancelling, spectral estimation, signal identification, channel equalization,

oai:mic.1984.2.2 2010-03-20

eng Journal article 1984-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1984-2-2.asp Fulltext http://www.mic-journal.no/PDF/1984/MIC-1984-2-2.pdf A Boundary Element Solution to the Problem of Interacting AC Fields in Parallel Conductors Rønquist, Einar M. Sira, Terje The ac fields in electrically insulated conductors will interact through the surrounding electromagnetic fields. The pertinent field equations reduce to the Helmholtz equation inside each conductor (interior problem), and to the Laplace equation outside the conductors (exterior problem). These equations are transformed to integral equations, with the magnetic vector potential and its normal derivative on the boundaries as unknowns. The integral equations are then approximated by sets of algebraic equations. The interior problem involves only unknowns on the boundary of each conductor, while the exterior problem couples unknowns from several conductors. The interior and the exterior problem are coupled through the field continuity conditions. The full set of equations is solved by standard Gaussian elimination. We also show how the total current and the dissipated power within each conductor can be expressed as boundary integrals. Finally, computational results for a sample problem are compared with a finite difference solution.

oai:mic.1984.2.3 2010-03-20

eng Journal article 1984-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1984-2-3.asp Fulltext http://www.mic-journal.no/PDF/1984/MIC-1984-2-3.pdf Recent Progress in the Control of Fish Behavior Balchen, Jens G. The paper gives a survey of recent activities in developing techniques for controlling fish behaviour over short and medium distances. The bases for control are described with reference to the sensory system of the fish and a simple model of fish behaviour. It is suggested that an effective way of controlling fish behaviour is by means of conditioning, in which reward or punishment is used in connection with an acoustical or visual signal. A number of possible applications which have been tested in practice are described. Fish behaviour, control, conditioning, control stimuli, acoustical repulsion, long term storage, fish farming,

oai:mic.1984.2.4 2010-03-20

eng Journal article 1984-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1984-2-4.asp Fulltext http://www.mic-journal.no/PDF/1984/MIC-1984-2-4.pdf Optimal Control of an Offshore Lifting Operation Mjelde, Kåre M. Lee, P.C.S. Qvam, W. Jacobsen, H.P. Rooney, P. Tegn, F. The optimal control of an offshore operation is analysed: a hideck which is at rest on a barge is lifted from the barge by means of a partly submerged frame that receives buoyancy by pumping water out of three cylinders connected to the frame. Air is pumped into the cylinders in order to maintain a positive difference between the internal air-pressure and the external water-pressure: for any cylinder, this pressure-difference is possibly critical at certain regions located on the cylinder and on a spherical cupola on the top of it. Optimal pumping rates of water and air as a function of time are determined, such as to minimize the maximum of certain weighted pressure differences at the critical regions, and such as to satisfy given geometrical and dynamical boundary conditions.

oai:mic.1984.3.1 2010-03-20

eng Journal article 1984-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1984-3-1.asp Fulltext http://www.mic-journal.no/PDF/1984/MIC-1984-3-1.pdf A Model of Phytoplankton Production in the Marginal Sea Ice Zone of the Barents Sea Slagstad, Dag The primary production in the Barents Sea must be high since it can sustain large stocks of fish. The factors controlling the primary production is not well understood. This paper takes the physical conditions (as far as we know them) in some of the ice-covered areas of the Barents Sea as an input to a plankton model. Simulations with different combinations of vertical turbulence and ice cover indicate that the ice concentration is important in shallow areas with strong tidal mixing, whereas the date of the start of melting of the ice and the resulting stabilization of the water column are more important in deeper parts of the Arctic waters. Where the Atlantic waters flow towards the ice border, the primary production starts early in the spring. High phytoplankton concentration is always found in this area. Study of the model results shows that the following mechanism could he responsible for the elevated biomass: turbulent Atlantic water, relatively rich in nutrients, stabilizes when meeting the ice or brackish water from the melting process and allows a high growth rate as soon as there is enough light early in the spring. High production may last for 2-3 months in this area. Modeling, phytoplankton, ecosystem,

oai:mic.1984.3.2 2010-03-20

eng Journal article 1984-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1984-3-2.asp Fulltext http://www.mic-journal.no/PDF/1984/MIC-1984-3-2.pdf Long Range Transport of Air Pollution Into Norway - A Transfer Function Approach Damsleth, Eivind The daily and monthly concentration of sulphate in the air at Birkcnes in the southern part of Norway is analysed within an intervention analysis and transfer function framework. As input to the model we use the prevailing wind direction. It is shown that when the wind comes mainly from the South, that is from Central Europe and England, this gives a significant increase in the sulphate concentration, while a northern wind leads to a decrease. Time series, environmental studies,

oai:mic.1984.3.3 2010-03-20

eng Journal article 1984-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1984-3-3.asp Fulltext http://www.mic-journal.no/PDF/1984/MIC-1984-3-3.pdf Robotics Research in Norway Hølpødt, J.R. Wetlesen, T. Håkonsen, H. Except for some districts and industries, the population of industrial robots in Norway is low. Trallfa AS is definitely the largest producer of robots in Norway. Jonas Oglænd A/S formerly produced handling manipulators, but they are now produced abroad. New companies such as NORKYB are developing. In addition to Trallfa and Oglænd, the development of robot systems is done by different research institutes such as the Center for Industrial Research (SI), SINTEF and the Rogaland Research Center (RF). These institutes do research work both for the robot manufacturers and directly for end users. Robotics, industrial robots, automation,

oai:mic.1984.3.4 2010-03-20

eng Journal article 1984-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1984-3-4.asp Fulltext http://www.mic-journal.no/PDF/1984/MIC-1984-3-4.pdf Norwegian Research and Development in the Field of Ship Automation Höivold, Ibb This survey paper briefly describes how ship automation was developed in Norway as a joint effort of research institutes, industrial companies and the shipping companies and organizations. The survey does not cover all industrial activities but mainly those which have been the result of grants from The Royal Norwegian Council for Scientific and Industrial Research (NTNF). The survey covers these activities, beginning with the efforts to obtain unmanned machinery space operation by means of conventional instrumentation and ending up with sophisticated computer-based systems for navigation and engine room applications. Ship automation, computer applications,

oai:mic.1984.4.1 2010-03-20

eng Journal article 1984-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1984-4-1.asp Fulltext http://www.mic-journal.no/PDF/1984/MIC-1984-4-1.pdf A Gyrocompass for Maritime Applications Based Upon Multivariable Control Theory Egeland, Olav A gyrocompass is designed using multivariable control theory. The compass can be implemented with an inertial platform or as a strap-down system. Measurement noise caused by vessel acceleration is modeled and feedforward is taken from vessel speed. Though the model is of order 9, it has only three unknown parameters of which one can be chosen a priori. Parameter estimation is discussed. For simulation of the compass, a non-linear surface vessel model with 6 degrees of freedom and wave excitation is used. Gyrocompass, maritime navigation, Kalman filtering,

oai:mic.1984.4.2 2010-03-20

eng Journal article 1984-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1984-4-2.asp Fulltext http://www.mic-journal.no/PDF/1984/MIC-1984-4-2.pdf A Quasi-Dynamic Optimal Control Strategy for Non-Linear Multivariable Processes Based upon Non-Quadratic Objective Functions Balchen, Jens G. The problem of systematic derivation of a quasi-dynamic optimal control strategy for a non-linear dynamic process based upon a non-quadratic objective function is investigated. The wellknown LQG-control algorithm does not lead to an optimal solution when the process disturbances have non-zero mean. The relationships between the proposed control algorithm and LQG-control are presented. The problem of how to constrain process variables by means of 'penalty' - terms in the objective function is dealt with separately. Optimal control, steady state optimization, non-quadratic objective functions,

oai:mic.1984.4.3 2010-03-20

eng Journal article 1984-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1984-4-3.asp Fulltext http://www.mic-journal.no/PDF/1984/MIC-1984-4-3.pdf Computer Simulation of Turbulent Reactive Gas Dynamics Hjertager, Bjørn H. A simulation procedure capable of handling transient compressible flows involving combustion is presented. The method uses the velocity components and pressure as primary flow variables. The differential equations governing the flow are discretized by integration over control volumes. The integration is performed by application of up-wind differencing in a staggered grid system. The solution procedure is an extension of the SIMPLE-algorithm accounting for compressibility effects. Gas explosion, fluid dynamics,

oai:mic.1985.1.1 2010-03-20

eng Journal article 1985-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1985-1-1.asp Fulltext http://www.mic-journal.no/PDF/1985/MIC-1985-1-1.pdf Estimation of Large-Scale Implicit Models Using 2-Stage Methods Henriksen, Rolf The problem of estimating large scale implicit (non-recursive) models by two- stage methods is considered. The first stage of the methods is used to construct or estimate an explicit form of the total model, by constructing a minimal stochastic realization of the system. This model is then subsequently used in the second stage to generate instrumental variables for the purpose of estimating each sub-model separately. This latter stage can be carried out by utilizing a generalized least squares method, but most emphasis is put on utilizing decentralized filtering algorithms and a prediction error formulation. A note about the connection between the original TSLS-method (two-stage least squares method) and stochastic realization is also made. Parameter estimation, large scale systems, two-stage methods, decentralized filtering, prediction error methods,

oai:mic.1985.1.2 2010-03-20

eng Journal article 1985-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1985-1-2.asp Fulltext http://www.mic-journal.no/PDF/1985/MIC-1985-1-2.pdf Frequency Response Analysis of Hydroelectric Power Plants with Influence From a Non-Linearized Frictional Damping and the Turbine Characteristics Brekke, H. The main purpose of the dissertation has been to establish a complete stability analysis of a hydroelectric power plant. The most important part in this study has been to establish a theory for the damping of oscillatory flow in tunnels and pipes. The influence of the turbine characteristics is also important and has been included by differentiation of the turbine equation. The partial derivative values can be found by means of the characteristic diagram of the turbine. Special attention is paid to establishing an empirical friction function for tunnels with rough walls. The author has based his theory on experimental tests carried out for damping of sea waves on rough beds, and the friction factor is a function of both frequency, amplitudes, cross section area and roughness of the wall (Jonsson 1978). Further, the damping of oscillations in shafts leading to tunnels taking into account the mean velocity in the tunnel has been established. Frequency response, hydroelectric power plant control,

oai:mic.1985.1.3 2010-03-20

eng Journal article 1985-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1985-1-3.asp Fulltext http://www.mic-journal.no/PDF/1985/MIC-1985-1-3.pdf A solution to the blow-up problem in adaptive controllers Sælid, Steinar Egeland, Olav Foss, Bjarne A. This paper addresses the blow-up problem associated with the parameter estimation part of an adaptive controller. A partial solution to the problem has been devised by the introduction of a variable forgetting factor. However, this does not eliminate the blow-up possibility. This is shown by simulation experiments on two different models. Adaptive control, blow-up problems,

oai:mic.1985.2.1 2010-03-20

eng Journal article 1985-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1985-2-1.asp Fulltext http://www.mic-journal.no/PDF/1985/MIC-1985-2-1.pdf Maximum Likelihood Estimation of Seismic Impulse Response Ursin, B. Holberg, O. A seismic trace is assumed to consist of a known signal pulse convolved with a reflection coefficient series plus a moving average noise process (colored noise). Multiple reflections and reverberations are assumed to be removed from the trace by conventional means. The method of maximum likelihood (ML) is used to estimate the reflection coefficients and the unknown noise parameters. If the reflection coefficients are known from well logs, the seismic pulse and the noise parameters can be estimated. Maximum-likelihood estimation, seismic data processing,

oai:mic.1985.2.2 2010-03-20

eng Journal article 1985-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1985-2-2.asp Fulltext http://www.mic-journal.no/PDF/1985/MIC-1985-2-2.pdf Docking Control of the Flexible Riser End in an Offshore Loading System Sælid, Steinar The SUBLOAD system for offshore loading of oil directly from a seafloor terminal by a flexible riser deployed from a dynamically positioned shuttle tanker is briefly described. Kalman filtering, marine operations,

oai:mic.1985.2.3 2010-03-20

eng Journal article 1985-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1985-2-3.asp Fulltext http://www.mic-journal.no/PDF/1985/MIC-1985-2-3.pdf Task Space Tracking for Manipulators Egeland, Olav For the purpose of controlling a manipulator in the task space, a linear model with task space position and velocity as state variables can be developed. This is done by means of exact compensation of the state-space model non-linearities using non-linear feedback. In this paper, feedback control for this linear state space model is developed using optimal control theory. Integral action is included to compensate for unmodeled forces and torques. In the resulting control system, the problem of transforming the task space trajectory to the joint space is avoided, and the controller parameters can be chosen to satisfy requirements specified in the task space. Simulation experiments show promising results. Robots,

oai:mic.1985.3.1 2010-03-20

eng Journal article 1985-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1985-3-1.asp Fulltext http://www.mic-journal.no/PDF/1985/MIC-1985-3-1.pdf Modeling Techniques: Theory and Practice Asbjørnsen, Odd A. A survey is given of some crucial concepts in chemical process modeling. Those are the concepts of physical unit invariance, of reaction invariance and stoichiometry, the chromatographic effect in heterogeneous systems, the conservation and balance principles and the fundamental structures of cause and effect relationships. As an example, it is shown how the concept of reaction invariance may simplify the homogeneous reactor modeling to a large extent by an orthogonal decomposition of the process variables. This allows residence time distribution function parameters to be estimated with the reaction in situ, but without any correlation between the estimated residence time distribution parameters and the estimated reaction kinetic parameters. A general word of warning is given to the choice of wrong mathematical structure of models. Systems engineering, model structure, model variables, chemical processes, orthogonal decomposition, conservation principle, invariance,

oai:mic.1985.3.2 2010-03-20

eng Journal article 1985-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1985-3-2.asp Fulltext http://www.mic-journal.no/PDF/1985/MIC-1985-3-2.pdf Simulation as a Tool in Operational Safety, Reliability and Control Tyssø, Arne Dynamic simulation has long been considered indispensable for the understanding of process dynamics and for control system design. There has been a tremendous increase in the number of computer based simulation tools, and considerable improvements have been made in the development of complex plants with advanced automatic control. Monte Carlo simulation, operator training, safety shutdown systems, modeling, computer-aided modeling, error detection, fault diagnosis,

oai:mic.1985.3.3 2010-03-20

eng Journal article 1985-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1985-3-3.asp Fulltext http://www.mic-journal.no/PDF/1985/MIC-1985-3-3.pdf The Numerical Solution of Differential and Differential-Algebraic Systems Nørsett, Syvert P. Systems of ordinary differential equations (ODE) or ordinary differential/algebraic equations (DAE) are well-known mathematical models. The numerical solution of such systems are discussed. For (ODE) we mention some available codes and stress the need of type insensitive versions. Further the term stiffness is redefined, and ideas on handling discontinuities are presented. The paper ends with a discussion of index for DAE. Initial value systems, algebraic constraints, stiff systems, discontinuities,

oai:mic.1985.3.4 2010-03-20

eng Journal article 1985-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1985-3-4.asp Fulltext http://www.mic-journal.no/PDF/1985/MIC-1985-3-4.pdf Modular Integration Methods for Simulation of Large-Scale Dynamic Systems Brosilow, Coleman B. Liu, Yin-Chang Cook, Jeffrey Klatt, John Modular simulation of dynamic systems offers the possibility of computational speed through parallel processing of individual sub-systems and through the use of the best integration algorithms for each sub-system. Such simulation needs co-ordination algorithms to keep the various sub-systems in time synchronization and to compute the interconnection between the sub-systems. A mathematical description of the co-ordination problem leads to the development of several new algorithms. These new algorithms are shown to have desirable convergence and stability properties. In particular a new Newton type algorithm is A-stable in a sense similar to that defined for ordinary integration algorithms. Modular, simulation, dynamic, parallel processing, coordination,

oai:mic.1985.4.1 2010-03-20

eng Journal article 1985-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1985-4-1.asp Fulltext http://www.mic-journal.no/PDF/1985/MIC-1985-4-1.pdf Evolution and Perspectives of Simulation Languages Following the CSSL Standard Rimvall, Magnus Cellier, Francois Since its publication in 1967 the CSSL specification has served as a successful standard for continuous simulation languages. However, recent advantages in modeling techniques, simulation methodologies and computer languages has motivated the simulation community to spur several standardization committees. In this paper the 1967 standard as well as several modern CSSL languages are reviewed, some current trends and developments are discussed and the status of present standardization efforts is presented. An outlook on some of the facilities we can expect to find in future simulation packages (with or without standardization) is given. digital simulation, continuous simulation languages, CSSL'67, combined continuous/discrete simulation,

oai:mic.1985.4.2 2010-03-20

eng Journal article 1985-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1985-4-2.asp Fulltext http://www.mic-journal.no/PDF/1985/MIC-1985-4-2.pdf Dynamic Simulation in the Processing Industries: Case Studies from Mobil Experience Womack, J.W. This paper provides an overview of Mobil's recent use of dynamic simulation. It provides examples of applications to capital projects, to operator training, and to existing facilities. Techniques and methodology of dynamic simulation are considered. Desirable future developments for dynamic simulation software are discussed. Dynamic simulation, petrochemical simulation, training simulators,

oai:mic.1985.4.3 2010-03-20

eng Journal article 1985-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1985-4-3.asp Fulltext http://www.mic-journal.no/PDF/1985/MIC-1985-4-3.pdf Perspectives in Software Design for Dynamic Process Simulation Divakaruni, S.M. The process simulation analysts have a wide range of options for simulation packages today. It is often difficult to choose one simulation software package to meet all the requirements of the process industry. The revolutions in computer hardware and software combined with increased knowledge of the users makes it a challenge to design a single simulation software package that meets all of their demands. Software design, process simulation, integration schemes, steady state solvers,

oai:mic.1985.4.4 2010-03-20

eng Journal article 1985-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1985-4-4.asp Fulltext http://www.mic-journal.no/PDF/1985/MIC-1985-4-4.pdf The Application of Simulation in Large Energy System Analysis Divakaruni, S.M. The Modular Modeling System (MMS) developed by the Electric Power Research Institute (EPRI) provides an efficient, economical, and user friendly computer code to engineers involved in the analysis of nuclear and fossil power plants. MMS will complement existing codes in the areas of nuclear and fossil power plant systems simulation. This paper provides a synopsis of MMS code features, development objectives, usage and results of fossil and nuclear plant simulation. Power plant simulation, MMS, modeling, nuclear and fossil plant transients,

oai:mic.1985.4.5 2010-03-20

eng Journal article 1985-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1985-4-5.asp Fulltext http://www.mic-journal.no/PDF/1985/MIC-1985-4-5.pdf Perspectives in Simulation Hardware and Software Architecture Grierson, W.O. Historically, analog and hybrid computer systems have provided effective real-time solutions for the simulation of large dynamic systems. In the mid 1970s, ADI concluded that these systems were no longer adequate to meet the demands of larger, more complex models and the demand for greater simulation accuracy. The decision was to design an all-digital system to satisfy these growing requirements (see Gilbert and Howe, (1978)). This all-digital approach was called the SYSTEM 10. The SYSTEM 10 has been effective in solving time-critical simulation problems and in replacing the previous approach of utilizing hybrid computers. Recent advances in 100 K emitter coupled logic (ECL) now make it possible to support a new generation of equipment that expands modeling capabilities to serve simulation needs. The hardware and software concepts of this system, called the SYSTEM 100, are the subject of this paper. ADSIM, SYSTEM 100, SYSTEM 10, hybrid computers, time-critical simulation,

oai:mic.1985.4.6 2010-03-20

eng Journal article 1985-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1985-4-6.asp Fulltext http://www.mic-journal.no/PDF/1985/MIC-1985-4-6.pdf Interactive Modeling and Simulation Using Distributed Computers and Graphical Aids Sælid, Steinar This paper describes a concept for high level configuration and parametrization of process simulators. The simulator is an integral part of a distributed process control system. This system can be switched from a control mode to a simulation mode where i/o signals are generated by/supplied to a process simulator when the system is set in simulation mode. The system is supported by a set of configuration tools. Modeling, computer aided configuration, simulation,

oai:mic.1986.1.1 2010-03-20

eng Journal article 1986-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1986-1-1.asp Fulltext http://www.mic-journal.no/PDF/1986/MIC-1986-1-1.pdf Identification of Seismic Reflections Using Singular Value Decomposition Ursin, Bjørn Zheng, Yuying Singular value decomposition (SVD) is applied to the identification of seismic reflections by using two different models: the impulse response model where a seismic trace is assumed to consist of a known signal pulse convolved with a reflection coefficient series plus noise, and the delayed pulse model where the seismic signal is assumed to consist of a small number of delayed pulses of known shape and with unknown amplitudes and arrival times. Seismic reflections, singular value decomposition,

oai:mic.1986.1.2 2010-03-20

eng Journal article 1986-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1986-1-2.asp Fulltext http://www.mic-journal.no/PDF/1986/MIC-1986-1-2.pdf Compositional Simulation of a Refinery Coker Furnace - An Industrial Example of Two-Phase Flow with Chemical Reaction Skogestad, Sigurd Gundersen, Truls Johnsen, Oddvar A computer program (KOKSOVN) has been developed for compositional steady-state simulation of a refinery delayed coker furnace. The main objective of this work has been to establish a tool for studying the effects that influence the deposition of coke on the inside walls of the tubes in order to maximize the time of operation (cycle time) between each cleaning of the tubes with a resulting stop in production. The program basically consists of a standard integration package which steps along the reactor (or pipeline) while solving the vapour-liquid equilibrium (VLE) and estimating physical properties for each step. Using a modular approach in the development, the resulting computer program has some general features which make it a possible simulation tool for any non-adiabatic plug flow reactor with two-phase flow. Depending on the chemical system, the routines for thermophysical and transport properties, phase equilibria and chemical reaction may be replaced by other methods. The program may also be used to simulate a pipeline with one or two-phase flow. Since, however, the total composition in this case is constant, it would probably be more efficient to use tables based on the pressure values, instead of performing tedious VLE calculations along the pipeline as is done in the present program. Simulation, numerical integration, phase equilibria, coke deposition,

oai:mic.1986.1.3 2010-03-20

eng Journal article 1986-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1986-1-3.asp Fulltext http://www.mic-journal.no/PDF/1986/MIC-1986-1-3.pdf Adaptive Control of Alumina Reduction Cells with Point Feeders Borg, Peter Moen, Tom Aalbu, Johannes To obtain optimum operation of an alumina reduction cell, it is important to keep the alumina concentration in the cell within a certain range. This will reduce anode effect frequency and stabilize the cell operation. However, it is not possible to measure this concentration directly. In the system presented here, the characteristic nonlinear relation between the alumina concentration and the cell resistance is modelled by an adaptive linear model where the estimated parameters give information about the concentration. This information is then used to control the alumina supply to the cell. In addition, the system controls the energy input to the cell by keeping the average resistance close to a reference value. Adaptive control, alumina reduction,

oai:mic.1986.2.1 2010-03-20

eng Journal article 1986-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1986-2-1.asp Fulltext http://www.mic-journal.no/PDF/1986/MIC-1986-2-1.pdf Adaptive Control of Alumina Reduction Cells with Point Feeders Perkins, John D. Howell, J.M. Wong, M.P.F. Reasons for considering the dynamics of a new or existing plant are illustrated through a number of industrial examples. Recent work aimed at assessing the effects of process dynamics on plant operability is presented. Two aspects are considered - the ability to maintain a given steady state in the face of disturbances (controllability) and the ability to move between steady states (switchability). Case studies are used to illustrate these concepts, and to demonstrate what is possible with a modern simulation system. Process dynamics, controllability, switchability,

oai:mic.1986.2.2 2010-03-20

eng Journal article 1986-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1986-2-2.asp Fulltext http://www.mic-journal.no/PDF/1986/MIC-1986-2-2.pdf Survey of Existing Systems for the Dynamic Simulation of Industrial Processes Perkins, John D. Dynamic simulation has the reputation of being a costly exercise. Tools to help reduce the development costs of dynamic models are discussed in this paper. Mathematical software libraries and CSSLs are briefly discussed from a user's point of view. Dynamic flowsheeting packages are classified, and one particular equation oriented package, SPEEDUP (Sargent, Perkins and Thomas (1982)) is discussed in detail. Dynamic simulation, mathematical software, CSSLs,

oai:mic.1986.2.3 2010-03-20

eng Journal article 1986-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1986-2-3.asp Fulltext http://www.mic-journal.no/PDF/1986/MIC-1986-2-3.pdf Diversifying the Risk Associated with Exploration Flåm, Sjur D. Storøy, Sverre This paper is concerned with the allocation of exploratory efforts under the limitation of a fixed budget. A chance constrained problem is formulated. To solve this problem an algorithm is developed which is based on the entropic penalty approach recently presented by Ben-Tal. Stochastic models, entalpic pentalty,

oai:mic.1986.2.4 2010-03-20

eng Journal article 1986-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1986-2-4.asp Fulltext http://www.mic-journal.no/PDF/1986/MIC-1986-2-4.pdf Variable Quotas, Irreversible Investment and Optimal Capacity in the Fisheries Flåm, Sjur D. We study the adaptation of a fishing fleet to a situation involving variable quotas of catch and irreversible investment. The theoretical results obtained here are applied to Norwegian industrial fisheries. Fisheries economics, control theory,

oai:mic.1986.3.1 2010-03-20

eng Journal article 1986-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1986-3-1.asp Fulltext http://www.mic-journal.no/PDF/1986/MIC-1986-3-1.pdf Dynamic Simulation of Chemical Engineering Systems by the Sequential Modular Approach Hillestad, Magne Hertzberg, Terje An algorithm for dynamic simulation of chemical engineering systems, using the sequential modular approach, is proposed. The modules are independent simulators, and are integrated over a common time horizon. Interpolation polynomials are used to approximate input variables. These input polynomials are updated before modules are intergrated in order to interpolate output from preceding module(s) and thereby increase coupling and stabilize the computation. Tear stream variables have to be predicted at future time tn+1 and various prediction methods are proposed. Modular integration, sequential, coordinational algorithm, prediction of tear variables, interpolation,

oai:mic.1986.3.2 2010-03-20

eng Journal article 1986-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1986-3-2.asp Fulltext http://www.mic-journal.no/PDF/1986/MIC-1986-3-2.pdf Man-Machine Interface Design for Modeling and Simulation Software Borstad, Arnstein J. Computer aided design (CAD) systems, or more generally interactive software, are today being developed for various application areas like VLSI-design, mechanical structure design, avionics design, cartographic design, architectual design, office automation, publishing, etc. Such tools are becoming more and more important in order to be productive and to be able to design quality products. One important part of CAD-software development is the man-machine interface (MMI) design. Computer aided design, interactive software, man-machine interaction, software prototyping, modeling,

oai:mic.1986.3.3 2010-03-20

eng Journal article 1986-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1986-3-3.asp Fulltext http://www.mic-journal.no/PDF/1986/MIC-1986-3-3.pdf Robustness Analysis of a Class of Decentralized Control Systems Solheim, Ole A. The paper presents a method for analysing the robustness properties of a class of decentralized control systems. Perturbations both in local and in interconnection parameters are dealt with. The method is based on the use of singular values. Several numerical examples are presented to illustrate the method. Robustness, decentralized control, decentralized estimation, singular values,

oai:mic.1986.3.4 2010-03-20

eng Journal article 1986-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1986-3-4.asp Fulltext http://www.mic-journal.no/PDF/1986/MIC-1986-3-4.pdf Stability of Pareto-Optimal Allocations of Resources to Activities Mjelde, Kåre M. A concept of stability is introduced for the Pareto-optimal solutions of a vector-valued problem of the allocation of resources to activities, and characterized by a property which is independent of uncertainties in the efficiency matrix of the allocations. Any feasible solution can be improved by cyclic shifts to give a stable Pareto-optimal solution. The resource allocation problem of the maximization of the sum of the utility returns from the activities and a problem with fuzzy resources and activities are shown to have stable Pareto-optimal solutions.

oai:mic.1986.4.1 2010-03-20

eng Journal article 1986-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1986-4-1.asp Fulltext http://www.mic-journal.no/PDF/1986/MIC-1986-4-1.pdf Bridging the gap between aquaculture and the information sciences Balchen, Jens G. The aquaculture industry is traditionally a low technology industry. But as demands on productivity, quality and availability are increasing the application of modern industrial technology is inevitable. After the fundamental problems of biology and of civil, mechanical and chemical engineering have been resolved, major progress may be expected through the application of the tools of the information sciences. Aquaculture, information sciences, modeling, control, instrumentation,

oai:mic.1986.4.2 2010-03-20

eng Journal article 1986-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1986-4-2.asp Fulltext http://www.mic-journal.no/PDF/1986/MIC-1986-4-2.pdf Modeling the Environmental Impact of Aquacultural Facilities - A Foundation for Future Management Licata, Dale M. A numerical model for computing the oxygen consumption and leakage of nutrients and organic matter from an aquacultural facility has been implemented. It is based upon the energy equation for fish and accounts for metabolism and growth over a range of temperatures and fish weight classes. Aquaculture, modeling,

oai:mic.1986.4.3 2010-03-20

eng Journal article 1986-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1986-4-3.asp Fulltext http://www.mic-journal.no/PDF/1986/MIC-1986-4-3.pdf Computer Aided Modeling of Aquaculture Plants Tyssø, Arne Mathematical modeling of dynamic processes is often considered an intricate and time consuming task. Program packages for simulation, time series analysis and identification in combination with modern data logging equipment allow the task to be handled in a simpler and more efficient way. Modeling, simulation, data processing,

oai:mic.1986.4.4 2010-03-20

eng Journal article 1986-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1986-4-4.asp Fulltext http://www.mic-journal.no/PDF/1986/MIC-1986-4-4.pdf On the problem of optimal timing of slaughtering in fish farming Lillestøl, J. Various issues concerning optimal feeding and optimal slaughtering are studied, following different formulations of the problem. We discuss separate and joint modeling, 'one-step look-ahead' and global procedures, deterministic and stochastic models. The price functions involved typically have jumps going from one weight category to the next. Special emphasis is given to two models, one with simplifying assumptions on the weight distribution, the other with a linear price approximation. Optimization, stochastic systems, control theory,

oai:mic.1986.4.5 2010-03-20

eng Journal article 1986-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1986-4-5.asp Fulltext http://www.mic-journal.no/PDF/1986/MIC-1986-4-5.pdf Use of Acoustics in Studies of Fish Reaction to Imposed Stimuli Bjordal, Å. Floen, S. Fosseidengen, J.E. Totland, B. Øvredal, J.T. Fernø, A. Huse, I. This paper describes a system for monitoring the behaviour of salmon in culture in relation to environmental factors and different rearing conditions. The main objective of this work is to minimize the stress level of the fish by optimizing critical factors in order to avoid disease and increase growth and fish quality. Aquaculture, monitoring system, data acquisition, behavioural sciences, stress control, signal processing,

oai:mic.1986.4.6 2010-03-20

eng Journal article 1986-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1986-4-6.asp Fulltext http://www.mic-journal.no/PDF/1986/MIC-1986-4-6.pdf Use of Acoustics in Studies of Fish Reaction to Imposed Stimuli Ona, E. Beltestad, A.K. The general distribution pattern of fish in a large pen is described through essentially simultaneous measurements of the integrated echo intensity in each of six separate cells using transducers mounted below the pen. The reaction of fish to various stimuli imposed in one of the cells is quantified by the change in frequency distribution of the echo intensity relative to the undisturbed situation. The experiment was part of a small-scale test of equipment to be used for observations of the attraction-effect of fish to oil-rig structures. The method seems to be suitable both for general fish behaviour studies, including attraction and avoidance effect, and for monitoring feeding systems in aquaculture based on fish conditioning. Acoustic transducers, fish, biocontrol, behavioural sciences,

oai:mic.1987.1.1 2010-03-20

eng Journal article 1987-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1987-1-1.asp Fulltext http://www.mic-journal.no/PDF/1987/MIC-1987-1-1.pdf Biomass Estimation in Aquaculture Facilities Løvik, A. This paper discusses the problem of size determination of fish without any handling requirements. Specially acoustical remote sensing based on resonance of the swimbladder is shown theoretically and experimentally. Acoustics, fish, length distribution,

oai:mic.1987.1.2 2010-03-20

eng Journal article 1987-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1987-1-2.asp Fulltext http://www.mic-journal.no/PDF/1987/MIC-1987-1-2.pdf Underwater Telemetry as a Tool in Aquaculture Research and Development Holand, B.A. Small acoustical transmitters may be used to obtain data from free swimming fish. The main principles behind this technique are described together with some of the equipment developed. Some examples are briefly discussed where heart beats, depth and temperature are measured to describe fish behaviour. Automatic fish tracking equipment that has been used to track fish within an enclosed area is also described. Fish telemetry, underwater acoustics, biology, behavioural sciences,

oai:mic.1987.1.3 2010-03-20

eng Journal article 1987-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1987-1-3.asp Fulltext http://www.mic-journal.no/PDF/1987/MIC-1987-1-3.pdf The Application of a Free Swimming Remotely Operated Vehicle in Aquaculture Klepaker, R. Vestgård, K. Hallset, J.O. Balchen, Jens G. In 1985, SINTEF and SIMRAD Subsea A/S started to develop an autonomous free swimming vehicle. The project was to develop a prototype of a small vehicle, in order to obtain knowledge and experience in designing, controlling and operating such vehicles. This was ready for testing at the end of 1985. The vehicle is controlled by an acoustic data telemetry system. The vehicle has a built-in television camera and containers for other sensors. It is suitable for inspection purposes. This paper describes the vehicle and some of the principles used. Freeswimming ROV, acoustic command telemetry link,

oai:mic.1987.1.4 2010-03-20

eng Journal article 1987-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1987-1-4.asp Fulltext http://www.mic-journal.no/PDF/1987/MIC-1987-1-4.pdf Computer Aided Control and Monitoring of Aquaculture Plants Hansen, Erik A computer system for control and monitoring of aquaculture plants has been developed by the Norwegian company NODEC. The system is based on a local area network which interfaces a computer system to the primary instruments located at various sites in the plant. Special software modules have been developed to handle different tasks such as data gathering, automatic control, alarming, logging, trend analysis and reporting. Special effort has been made to develop a user-friendly high level man-machine interface. A software library is available for monitoring and control of water quality, water distribution, heating systems, biomass and feeding systems. Data acquisition, automatic control, monitoring, logging, trend analysis, interactive dynamic colour display,

oai:mic.1987.1.5 2010-03-20

eng Journal article 1987-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1987-1-5.asp Fulltext http://www.mic-journal.no/PDF/1987/MIC-1987-1-5.pdf Automatic feeding and Harvesting of Juvenile Atlantic Cod (Gadus Morhua L.) in a Pond Øiestad, V. Pedersen, T. Folkvord, A. Bjordal, Å. Kvenseth, P.G. Large scale production of juvenile Atlantic cod has been carried out since 1980 in a saltwater pond. A break-through was obtained in 1983 with high survival rates of cod larvae to metamorphosis. In 1985 we made progress in two fiels, reduced cannibalism and automatic harvesting. Juvenile cod formed large schools while fed dry pellets in the currents set up by five propellers. An underwater loudspeaker was programmed to give sound pulses just before feeding. During harvesting dry pellets were released inside a fish trap while giving the sound signals the cod juveniles were conditioned to. The cod readily entered the trap and a computer-controlled fish pump transported the fish from the fish trap into a storing tank and grading grids. The trap gradually emptied the pond of fish and more than 80 Aquaculture, biocontrol, computer control,

oai:mic.1987.1.6 2010-03-20

eng Journal article 1987-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1987-1-6.asp Fulltext http://www.mic-journal.no/PDF/1987/MIC-1987-1-6.pdf An Automated System for Incubation of Pelagic Fish Eggs Jørgensen, Leif An automated system for incubation of pelagic fish eggs is described. The system has an internal air driven water circulation which separates healthy and dead or strongly infected eggs. A processor controlled, pulsed water exchange provides a strongly reduced water requirement. The equipment has also an automated temperature and salinity control and adjustment. Aquaculture, fish, egg incubation,

oai:mic.1987.1.7 2010-03-20

eng Journal article 1987-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1987-1-7.asp Fulltext http://www.mic-journal.no/PDF/1987/MIC-1987-1-7.pdf A Model Based System for Control of Live Feed Level for Larval Fish Slagstad, Dag Olsen, Y. Tilseth, S. A mathematical model of the production process of live feed to fish larvae is presented. The model is used as a design tool to construct a control system which ensures stable and controllable conditions for live feed organisms (rotifers). The simulation results demonstrate the effect of possible changes in the biological parameters and different operational routines. Biocybernetics, aquaculture, fish larvae, plankton, modeling,

oai:mic.1987.1.8 2010-03-20

eng Journal article 1987-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1987-1-8.asp Fulltext http://www.mic-journal.no/PDF/1987/MIC-1987-1-8.pdf Aspects of Automation in a Lobster Farming Plant Grimsen, Steinar Jaques, Robert N. Erenst, Vincent Balchen, Jens G. This paper describes the automation aspects of rearing juvenile lobsters for sea ranching. It gives an outline of rearing techniques and presents specifications for a feeding system. A description is given of the equipment that has been developed. Other automation and instrumentation tasks are briefly discussed. Aquaculture, lobster farming, automation, instrumentation,

oai:mic.1987.2.1 2010-03-20

eng Journal article 1987-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1987-2-1.asp Fulltext http://www.mic-journal.no/PDF/1987/MIC-1987-2-1.pdf Pressurised Water Reactor Control by the Hierarchical Method Leikkonen, Ilkka A simple version of the hierarchical optimization method is used to solve the control problem for the power distribution of a pressurized water reactor. The control period is about twenty hours. The control objectives include the total power, power distribution and use of boron. The controllers are a rod bank, soluble boron in the coolant and the coolant temperature deviation. A one-dimensional non-linear core model is used, with full xenon-iodine dynamics. Pressurized water reactor, optimal control, power distribution,

oai:mic.1987.2.2 2010-03-20

eng Journal article 1987-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1987-2-2.asp Fulltext http://www.mic-journal.no/PDF/1987/MIC-1987-2-2.pdf The core surveillance system SCORPIO and its validation against measured pressurised-water reactor plant data Berg, Øivind Hval, Sverre Jørgensen, Uffe S. The computerised core surveillance system SCORPIO is described. Main modules in the system arc an interactive communication system with a function keyboard and a fully graphic colour screen; a strategy generator which proposes how to operate the reactor in the near future; a fast core simulator with predictive capability; a data base and a limit check module which calculates margins to the operational limits. The predictive part of the system is completed, and is already installed at a pressurised-water reactor plant. The core follow module is under development, and installation of this module will take place in 1987. Results from the validation of the strategy generator and the simulator are also described. PWR type reactors, in-core instruments, reactor control systems, reactor instrumentation, reactor cores, reactor simulators, computerised control systems, on-line control systems,

oai:mic.1987.2.3 2010-03-20

eng Journal article 1987-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1987-2-3.asp Fulltext http://www.mic-journal.no/PDF/1987/MIC-1987-2-3.pdf 3-Dimensional Calculations on Smelting Electrodes Innvær, Reidar Fidje, Knut Sira, Terje Søderberg selfbaking electrodes are used to conduct electric current into the electric reduction furnace. Two-dimensional computer models for the computation of temperatures, electric currents and thermal stresses have been used for a long time in the R&D effort to improve the construction and operation of the electrode. Smelting electrode, mathematical model,

oai:mic.1987.2.4 2010-03-20

eng Journal article 1987-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1987-2-4.asp Fulltext http://www.mic-journal.no/PDF/1987/MIC-1987-2-4.pdf Finite State Approximations for Countable State Infinite Horizon Discounted Markov Decision Processes Flåm, Sjur D. It is proved that the optimal policy of a Markov decision process where the state space is truncated, will approximate the policy in case of no truncation. Markov decision processes, approximation,

oai:mic.1987.3.1 2010-03-20

eng Journal article 1987-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1987-3-1.asp Fulltext http://www.mic-journal.no/PDF/1987/MIC-1987-3-1.pdf The Planning of Straight Line Trajectory in Robotics Using Interactive Graphics Wang, Kesheng Lien, Terje K. The planning of straight line trajectory using the interactive computer graphics simulation of robot manipulator movement is discussed. This new approach to straight line motion planning improves the 'bound deviation joint paths' developed by R. M. Taylor (1979). The new approach has three characteristics: (1) linear interpolation in joint space; (2) unequal intervals for interpolating knot points; (3) using interactive computer graphics to assure that the maximum deviation in the whole segment is less than the pre-specified values. The structure and mathematical basis of a computer program developed for this purpose are presented. Robotics, trajectory planning, robot motion,

oai:mic.1987.3.2 2010-03-20

eng Journal article 1987-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1987-3-2.asp Fulltext http://www.mic-journal.no/PDF/1987/MIC-1987-3-2.pdf Cartesian Trajectory Tracking for Manipulators Using Optimal Control Theory Egeland, Olav A Cartesian trajectory tracking system for manipulators is developed using optimal control theory. By including the Cartesian position in the state vector, transformation of the trajectory from Cartesian space to manipulator joint space is avoided, and the Jacobian matrix need not be inverted. The tracking system may also be applied to kinematically redundant manipulators. For this type of manipulator, singularities are avoided by choosing a suitable performance index in the optimal control problem. Simulation using a simple kinematically redundant manipulator shows that a small tracking error can be achieved with low motor torques. Robots, kinematically redundant manipulators, optimal control,

oai:mic.1987.3.3 2010-03-20

eng Journal article 1987-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1987-3-3.asp Fulltext http://www.mic-journal.no/PDF/1987/MIC-1987-3-3.pdf On the Robustness of the Computed Torque Technique in Manipulator Control Egeland, Olav In this paper, the robustness of the computed torque technique for manipulator control is investigated in the presence of model errors. The robustness analysis is performed in the frequency domain by means of the block Gerschgorin theorem. This theorem gives inclusion regions for the eigenvalues of the linearized state space model. The stability of the system close to a trajectory can then be investigated. The results indicate that relatively large errors in the non-linear feedback compensation of system non-lincarities may be tolerated without affecting system stability. However, even small errors in the computed inertia matrix may result in instability. Robots,

oai:mic.1987.3.4 2010-03-20

eng Journal article 1987-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1987-3-4.asp Fulltext http://www.mic-journal.no/PDF/1987/MIC-1987-3-4.pdf Dynamic Control of Kinematically Redundant Robotic Manipulators Lunde, Erling Egeland, Olav Balchen, Jens G. Several methods for task space control of kinematically redundant manipulators have been proposed in the literature. Most of these methods are based on a kinematic analysis of the manipulator. In this paper we propose a control algorithm in which we are especially concerned with the manipulator dynamics. The algorithm is particularly well suited for the class of redundant manipulators consisting of a relatively small manipulator mounted on a larger positioning part. Robotics, kinematically redundant manipulators, non-linear control,

oai:mic.1987.3.5 2010-03-20

eng Journal article 1987-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1987-3-5.asp Fulltext http://www.mic-journal.no/PDF/1987/MIC-1987-3-5.pdf Coordinating Control of a Special Joint Structure with More Servos than Degrees of Freedom Dessen, Fredrik A joint mechanism for use as a general building block in manipulators with a very high number of degrees of freedom is introduced. It consists of 3 servos driving a 2 d.o.f. universal joint by means of wire. A coordinate transformation set is developed, which includes positional, velocity and force transformations. Both direct and inverse transformations are presented. Special attention is given to the inverse force transformation which is obtained using linear optimization. The solution in this case is also shown to be valid for a more general class of constrained non-linear optimization problems. An example is given of the use of the coordinate transformation set; a joint control system including servos under internal force control. Robot manipulators, redundancy, coordinate transformation, force control,

oai:mic.1987.4.1 2010-03-20

eng Journal article 1987-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1987-4-1.asp Fulltext http://www.mic-journal.no/PDF/1987/MIC-1987-4-1.pdf Cartesian Control of a Spray-Painting Robot with Redundant Degrees of Freedom Egeland, Olav Balchen, Jens G. A controller for redundant manipulators with a small, fast manipulator mounted on a positioning part has been developed. The controller distributes the fast motion to the small, fast manipulator and the slow, gross motion to the positioning part. A position reference is generated on-line to the positioning part to avoid singularities and the loss of degrees of freedom. This reference is selected according to an ad hoc procedure which makes the small, fast manipulator work around the centre of its working range. In the control system, the task space position vector is augmented with the generalized coordinates of the positioning part. The resulting augmented task space vector contains a set of generalized coordinates for the manipulator. Feedback linearization and decoupling are applied in the augmented task space to obtain a model consisting of decoupled double integrators. The low and high frequency motion is distributed by controlling the double integrators associated with the end effector with a high bandwidth, while the double integrators associated with the positioning part are controlled with a low bandwidth. Robots, kinematically redundant manipulators, non-linear control,

oai:mic.1987.4.2 2010-03-20

eng Journal article 1987-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1987-4-2.asp Fulltext http://www.mic-journal.no/PDF/1987/MIC-1987-4-2.pdf A Truly Distributed Process Control System with Online Configuration and Expansion Capabilities Sælid, Steinar The process control system described in this paper, is a very flexible system equipped with a range of computer-aided configuration tools. These are tools for the configuration and reconfiguration of control loops, computing blocks, logic control modules, i/o connections or graphics, and presentation elements such as reports, trend curves, flowsheets, free graphical pictures etc., while the system is operational and in control. Documentation of system topology, system parametrization and the i/o configuration/connection etc., can be extracted from the system at any time. The system can also be configured for training and simulation applications as well as for process control. The paper describes the system hardware architecture, the distributed database and the configuration and operation tools. Process control system,

oai:mic.1987.4.3 2010-03-20

eng Journal article 1987-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1987-4-3.asp Fulltext http://www.mic-journal.no/PDF/1987/MIC-1987-4-3.pdf An Adaptive Controller Based upon Continuous Estimation of the Closed Loop Frequency Response Balchen, Jens G. Lie, Bernt An adaptive control algorithm based upon on-line estimation of the -180 degree shift frequency and the gain margin is investigated. The estimates are found by perturbing the system with a small signal and then correlating the system deviation with the excitation. As only two parameters are estimated, the algorithm is robust. Moreover, the estimator can be applied to non-minimum phase systems, including systems with a varying time-delay. The control algorithm can be of any form as long as there is a functional relationship between the estimated parameters and the control algorithm parameters. To avoid an excessive perturbation signal, the square of the amplitude of this signal is automatically adjusted to a certain ratio of the variance of the error signal. A mathematical analysis of convergence is presented and the theory is confirmed by experimental results. Adaptive control, frequency response, correlation methods, parameter estimation,

oai:mic.1988.1.1 2010-03-20

eng Journal article 1988-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1988-1-1.asp Fulltext http://www.mic-journal.no/PDF/1988/MIC-1988-1-1.pdf On-Line Component Estimation and Analyser Claibration for a Complex Industrial Processing Plant using Kalman-Filtering Norderhaug, Ola Balchen, Jens G. Onshus, Tor The paper presents an on-line analyser system based on a Kalman filtering technique. The system is implemented on a computer, and tested against an analyser simulator. A mathematical model for the analyser is also determined since an extended Kalman filter can perform both component estimation and analyser calibration, accuracy in the analysis is improved. Kalman filtering, estimation, calibration,

oai:mic.1988.1.2 2010-03-20

eng Journal article 1988-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1988-1-2.asp Fulltext http://www.mic-journal.no/PDF/1988/MIC-1988-1-2.pdf Identification of Layers in Oil-Tanks Using a Reflectometer Bøifot, Anton M. This paper treats the possibilities of analysing layers in oil-tanks using a reflectometer. First some basic principles and expressions are presented. After that examples of commonly used windows are shown and a new generation of windows developed. These are called Hammingfolded windows, and can have side lobe levels below -85 dB. Frequency domain analyses, time domain analyses, windows, dielectrical properties, attenuation, methods of detection, simulations,

oai:mic.1988.1.3 2010-03-20

eng Journal article 1988-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1988-1-3.asp Fulltext http://www.mic-journal.no/PDF/1988/MIC-1988-1-3.pdf Estimating the Condition of the Heat Resistant Lining in an Electrical Reduction Furnace Waalmann, Jan G. This paper presents a system for estimating the condition of the heat resistant lining in an electrical reduction furnace for ferrosilicon. The system uses temperature measured with thermocouples placed on the outside of the furnace-pot. These measurements are used together with a mathematical model of the temperature distribution in the lining in a recursive least squares algorithm to estimate the position of 'the transformation front'. The system is part of a monitoring system which is being developed in the AIP-project: 'Condition monitoring of strongly exposed process equipment in thc ferroalloy industry'. The estimator runs on-line, and results arc presented in colour-graphics on a display unit. The goal is to locate the transformation front with an accuracy of +- 5cm. Modeling, estimation, condition monitoring, heat resistant materials, process equipment,

oai:mic.1988.2.1 2010-03-20

eng Journal article 1988-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1988-2-1.asp Fulltext http://www.mic-journal.no/PDF/1988/MIC-1988-2-1.pdf Adaptive control of a manipulator when the mass of the load is unknown Egeland, Olav An adaptive controller for a robotic manipulator is presented. In the control system, the computed torque technique is used to linearize and decouple the dynamic model. The computed torque technique requires that the complete dynamic model is known. Normally, this model is known except perhaps for a few parameters, e.g. load inertia and centre of gravity and friction co-efficients. In this paper, the unknown parameters, which all represent physical quantities, are estimated using a recursive prediction error method. The most recent parameter estimate is then used in the computed torque technique. The control system is applied to the positioning part of an industrial robot in a simulation experiment where the unknown parameter is the mass of the load. The controller performed well, and the mass of the load can even be estimated when the manipulator is accelerating and there is a large control deviation. Robotics, adaptive control,

oai:mic.1988.2.2 2010-03-20

eng Journal article 1988-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1988-2-2.asp Fulltext http://www.mic-journal.no/PDF/1988/MIC-1988-2-2.pdf Introduction of b-splines to trajectory planning for robot manipulators Koch, Per E. Wang, Kesheng This paper describes how B-splines can be used to construct joint trajectories for robot manipulators. The motion is specified by a sequence of Cartesian knots, i.e., positions and orientations of the end effector of a robot manipulator. For a six joint robot manipulator, these Cartesian knots are transformed into six sets of joint variables, with each set corresponding to a joint. Splines, represented as linear combinations of B-splines, are used to fit the sequence of joint variables for each of the six joints. A computationally very simple, recurrence formula is used to generate the 8-splines. This approach is used for the first time to establish the mathematical model of trajectory generation for robot manipulators, and offers flexibility, computational efficiency, and a compact representation. Robotics, trajectory planning,

oai:mic.1988.2.3 2010-03-20

eng Journal article 1988-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1988-2-3.asp Fulltext http://www.mic-journal.no/PDF/1988/MIC-1988-2-3.pdf Maximum likelihood estimation of ocean wave spectra from general arrays of wave gauges Krogstad, Harald E. The paper discusses estimation of directional ocean wave spectra from a spatial array of sensors by means of the Maximum Likelihood (ML) method. An iterative improvement of the ML estimate is proposed and illustrated on synthetic and real data. The wave data was obtained by an acoustic Doppler current meter in the Current Measurement Experiment (CUMEX) carried out by Esso Norge a.s at the Odin platform in the Norwegian Sea. Maximum Likelihood Method (MLM), wave spectra,

oai:mic.1988.2.4 2010-03-20

eng Journal article 1988-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1988-2-4.asp Fulltext http://www.mic-journal.no/PDF/1988/MIC-1988-2-4.pdf A Positional Deviation Sensor for Training of Robots Dessen, Fredrik Balchen, Jens G. A device for physically guiding a robot manipulator through its task is described. It consists of inductive, contact-free positional deviation sensors. The sensor will be used in high performance sensory control systems. The paper describes problems concerning multi-dimensional, non-linear measurement functions and the design of the servo control system. Robot manipulators, direct training,

oai:mic.1988.3.1 2010-03-20

eng Journal article 1988-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1988-3-1.asp Fulltext http://www.mic-journal.no/PDF/1988/MIC-1988-3-1.pdf Observability analysis and bad date processing of state estimation using Hachtel's augmented matrix method Wu, Felix F. Liu, Wen-Hsiung E. Holten, Lars Gjelsvik, Anders Aam, Sverre The triangular-factorization-based observability analysis and the normalized residual-based bad data processing are extended to state estimation using Hachtel's augmented matrix method. This method is numerically robust, computationally efficient, and has a reasonable extra storage requirement. In this paper it is shown that the observability analysis can be carried out in the process of triangular factorization of the augmented coefficient matrix used in Hachtel's method. Moreover, the normalized residuals are shown to be obtainable using the sparse inverse of this augmented matrix. The algorithms have been successfully incorporated in the state estimation program developed at Norwegian State Power Board (Statkraft). Test results on the IEEE 14 bus system and a 99-bus system consisting of the main grid of southern Norway are presented. Hachtel's approach to state estimation provides an attractive alternative to the standard normal equations approach. Electric power system, static state estimation, error covariance sparse matrices, least squares,

oai:mic.1988.3.2 2010-03-20

eng Journal article 1988-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1988-3-2.asp Fulltext http://www.mic-journal.no/PDF/1988/MIC-1988-3-2.pdf A Note on the bottom shear stress in oscillatory planetary boundary layer flow Myrhaug, Dag A simple analytical theory is presented, which describes the motion in a turbulent oscillatory planetary boundary layer near a rough seabed using a two-layer, time-invariant eddy viscosity model. The bottom shear stress is outlined, and comparison is made with Pingree and Griffiths' (1974) measurements of turbulent tidal planetary boundary layer flow on the continental shelf south-west of Lands End, England. Oscillatory planetary flow, boundary layer, eddy viscosity,

oai:mic.1988.3.3 2010-03-20

eng Journal article 1988-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1988-3-3.asp Fulltext http://www.mic-journal.no/PDF/1988/MIC-1988-3-3.pdf Internal Decoupling in Nonlinear Process Control Balchen, Jens G. Lie, Bernt Solberg, Ingar A simple method has been investigated for the total or partial removal of the effect of non-linear process phenomena in multi-variable feedback control systems. The method is based upon computing the control variables which will drive the process at desired rates. It is shown that the effect of model errors in the linearization of the process can be partly removed through the use of large feedback gains. In practice there will be limits on how large gains can he used. The sensitivity to parameter errors is less pronounced and the transient behaviour is superior to that of ordinary PI controllers. Non-linear control, linearization by transformation, multi-variable control, stability,

oai:mic.1988.3.4 2010-03-20

eng Journal article 1988-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1988-3-4.asp Fulltext http://www.mic-journal.no/PDF/1988/MIC-1988-3-4.pdf Condition monitoring of power plants using extended Kalman filtering Skarstein, Øyvin Extended Kalman Filtering (EKF) is applied to the condition monitoring of hydro-power production plants. This method is well suited to real-time failure detection and identification. This paper presents one important application: monitoring of hydraulic performance of hydro-power plants. Condition monitoring, Extended Kalman Filtering, hydro power plant, fault detection,

oai:mic.1988.4.1 2010-03-20

eng Journal article 1988-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1988-4-1.asp Fulltext http://www.mic-journal.no/PDF/1988/MIC-1988-4-1.pdf Modeling and Non-Linear Self-Tuning Robust Trajectory Control of an Autonomous Underwater Vehicle Fossen, Thor Inge Balchen, Jens G. A non-linear self-tuning algorithm is demonstrated for an autonomous underwater vehicle. Tighter control is achieved by a non-linear parameter identification algorithm which reduces the parameter uncertainty bounds. Expensive hydrodynamic tests for parameter determination can thus be avoided. Excellent tracking performance and robustness to parameter uncertainty are guaranteed through a robust control strategy based on the estimated parameters. The nonlinear control law is highly robust for imprecise models and the neglected dynamics. The non-linear self-tuning control strategy is simulated for the horizontal positioning of an underwater vehicle. Non-linear identification, non-linear control, robust control, self-tuning,

oai:mic.1988.4.2 2010-03-20

eng Journal article 1988-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1988-4-2.asp Fulltext http://www.mic-journal.no/PDF/1988/MIC-1988-4-2.pdf Data and Program Structure for a Modular Extended Kalman Filter Solberg, Ingar The paper presents a data and program structure that makes it easier to implement a nonlinear process or measurement model when using the extended Kalman filter. This is achieved by a composite data type containing both the estimated value and covariance information. The basic operators ( +, -, *, /) and common functions are implemented for this data type. These enable a model for the extended Kalman filter to be implemented as easily as a discrete-time simulation model. Extended Kalman filter, nonlinear filtering, state space methods,

oai:mic.1988.4.3 2010-03-20

eng Journal article 1988-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1988-4-3.asp Fulltext http://www.mic-journal.no/PDF/1988/MIC-1988-4-3.pdf Applying parameter identification and optimal input design in well-testing Foss, Bjarne A. This article discusses the use of optimal input design and parameter identification methods in reservoir evaluation. A new optimal input design criterion is presented which in addition to the uncertainty in the parameter estimates accounts for the curvature of the parameter space. Reservoir, well-testing, parameter identification,

oai:mic.1988.4.4 2010-03-20

eng Journal article 1988-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1988-4-4.asp Fulltext http://www.mic-journal.no/PDF/1988/MIC-1988-4-4.pdf Learning Control of Redundant DOF Robots by Optimization of Parameterized Control Space Lunde, Erling Balchen, Jens G. A framework for the learning control of robots based on a parameterized control space is doscussed. Emphasis is put on how to utilize stored motion knowledge. The principles are applied to an example of redundancy resolution for a simple manipulator. Global sub-optimal solutions for feedforward control are achieved using a simple optimization algorithm. A time-integral performance criterion is used. Robots, learning control,

oai:mic.1989.1.1 2010-03-20

eng Journal article 1989-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1989-1-1.asp Fulltext http://www.mic-journal.no/PDF/1989/MIC-1989-1-1.pdf Frequency Response Adaptive Control of a Refrigeration Cycle Balchen, Jens G. Telnes, Kåre Di Ruscio, David A technique for the adaptation of controller parameters in a single control loop based upon the estimation of frequency response parameters has been presented in an earlier paper. This paper contains an extension and a generalization of the first method and results in a more versatile solution which is applicable to a wider range of process characteristics. The application of this adaptive control technique is illustrated by a laboratory refrigeration cycle in which the evaporator pressure controls the speed of the compressor. Adaptive control, self tuning, frequency response,

oai:mic.1989.1.2 2010-03-20

eng Journal article 1989-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1989-1-2.asp Fulltext http://www.mic-journal.no/PDF/1989/MIC-1989-1-2.pdf Convergence analysis of some decentralized parameter estimators Henriksen, Rolf Parameter estimators based upon standard estimation techniques, viz, least squares (LS) methods, instrumental variable methods, etc. may occasionally have difficulties with systems having a somewhat ill-conditioned nature, e.g., stiff systems. The robustness of the estimator can, however, be significantly improved by employing some kind of decentralized estimation techniques. The method presented here utilizes certain moving average filters and a system of parallel estimators, where the moving average filters are used to prefilter the input-output data. The form of these filters depends upon the estimated model, and the decentralized estimator will therefore usually have to be employed in a bootstrap fashion. The convergence properties of this bootstrap estimator are analysed, and necessary and sufficient conditions for local convergence of some decentralized estimators based upon LS or IV techniques are derived. Decentralized estimation, least squares method, instrumental variable methods, bootstrap estimators, convergence analysis,

oai:mic.1989.1.3 2010-03-20

eng Journal article 1989-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1989-1-3.asp Fulltext http://www.mic-journal.no/PDF/1989/MIC-1989-1-3.pdf State Space Model Predictive Control of a Multi Stage Electro-metallurgical Process Balchen, Jens G. Ljungquist, Dag Strand, Stig The paper deals with the proposed application of a novel technique for Model Predictive Control to a multistage electrometallurgical process. The novel control technique is based upon high speed repetitive simulation of a non-linear state space model of the process including relevant constraints, and searching in a parameterized control space by an efficient optimization routine until an optimal set of control actions has been found. This MPC-technique is not limited to linear processes with quadratic objective functionals and is therefore believed to offer a major improvement to the control of many industrial processes where the standard, linear control solutions fail because of non-linearities and constraints in the process system. Optimal control, predictive control, non-linear control system, state-space methods, iterative methods,

oai:mic.1989.1.4 2010-03-20

eng Journal article 1989-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1989-1-4.asp Fulltext http://www.mic-journal.no/PDF/1989/MIC-1989-1-4.pdf Man-machine interface in a submarine command and weapon control system: features and design experience Aas, Johan H. Brathen, Karsten Nordo, Erik Ørpen, Ole Ø. Important man-machine interface (MMI) issues concerning a submarine command and weapon control system (CWCS) such as crew organization, automation level and decision support are discussed in this paper. Generic submarine CWCS functions and operating conditions are outlined. Detailed, dynamic and real-time prototypes were used to support the MMI design. The prototypes are described and experience with detailed prototyping is discussed. Some of the main interaction principles are summarized and a restricted example of the resulting design is given. Our design experience and current work have been used to outline future perspectives of MMI design in naval CWCSs. The need for both formal and experimental approaches is emphasized. Man-machine systems, human factors, underseas systems, prototyping, system analysis, guidance systems,

oai:mic.1989.2.1 2010-03-20

eng Journal article 1989-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1989-2-1.asp Fulltext http://www.mic-journal.no/PDF/1989/MIC-1989-2-1.pdf Predictive Control Based upon State Space Models Balchen, Jens G. Ljungquist, Dag Strand, Stig Repetitive online computation of the control vector by solving the optimal control problem of a non-linear multivariable process with arbitrary performance indices is investigated. Two different methods are considered in the search for an optimal, parameterized control vector: Pontryagin's Maximum Principle and optimization by using the performance index and its gradient directly. Unfortunately, solving this optimization problem has turned out to be a rather time-consuming task which has resulted in a time delay that cannot be accepted when the actual process is exposed to rapidly-varying disturbances. However, an instantaneous feedback strategy operating in parallel with the original control aogorithm was found to be able to cope with this problem. Optimal control, predictive control, non-linear control system, state-space models, iterative methods,

oai:mic.1989.2.2 2010-03-20

eng Journal article 1989-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1989-2-2.asp Fulltext http://www.mic-journal.no/PDF/1989/MIC-1989-2-2.pdf Optimal continuous-path control for manipulators with redundant degrees of freedom Egeland, Olav Sagli, Jan R. Jansen, Bård A control system for macro-mini manipulators is presented. A position transformation from the end-effector reference to joint coordinates is found using kinematic optimization. Decoupling and optimal control is used to coordinate the motion of the macro and micro part. The redundant manipulator will then have the speed of the micro manipulator and the large workspace of the macro manipulator. When optimal control is used, the redundant manipulator may be even faster than the micro manipulator provided that a suitable performance index is used. The performance of the manipulator is optimized over the whole reference, and this will give better results than the purely kinematic instantaneous optimization which is the dominating technique in research literature. Robots, optimal control,

oai:mic.1989.2.3 2010-03-20

eng Journal article 1989-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1989-2-3.asp Fulltext http://www.mic-journal.no/PDF/1989/MIC-1989-2-3.pdf Limit cycles and Hopf bifurcations in a Kolmogorov type system Muratori, Simona Rinaldi, Sergio The paper is devoted to the study of a class of Kolmogorov type systems which can be used to represent the dynamic behaviour of prey and predators. The model is an extension of the classical prey-predator model since it allows intra-specific competition for the predator's species. The analysis shows that the system can only have Kolmogorov's two modes of behaviour: a globally stable equilibrium or a globally stable limit cycle. Moreover, the transition from one of these two modes to the other is a non-catastrophic Hopf bifurcation which can be specified analytically. Non-linear systems, limit cycle, Hopf bifurcation, Poincare index, stability,

oai:mic.1989.2.4 2010-03-20

eng Journal article 1989-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1989-2-4.asp Fulltext http://www.mic-journal.no/PDF/1989/MIC-1989-2-4.pdf Efficient inverse position transformation for TR 4000S robot manipulator Wang, Kesheng An efficient method is developed for computing the inverse kinematic position solution with a closed form for the TR 4000S spray painting robot manipulator with five degrees of freedom and non-spherical wrist construction. The inverse kinematic problem is defined as the transformation from Cartesian space to the joint space. The solution is based on the geometrical separation of the arm and wrist of a robot manipulator and shows that it is very systematic, efficient and easily derived. Inverse kinematics, robot control, robot manipulator,

oai:mic.1989.2.5 2010-03-20

eng Journal article 1989-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1989-2-5.asp Fulltext http://www.mic-journal.no/PDF/1989/MIC-1989-2-5.pdf Trajectory generation for manipulators using linear quadratic optimal tracking Egeland, Olav Lunde, Erling The reference trajectory is normally known in advance in manipulator control which makes it possible to apply linear quadratic optimal tracking. This gives a control system which rounds corners and generates optimal feedforward. The method may be used for references consisting of straight-line segments as an alternative to the two-step method of using splines to smooth the reference and then applying feedforward. In addition, the method can be used for more complex trajectories. The actual dynamics of the manipulator are taken into account, and this results in smooth and accurate tracking. The method has been applied in combination with the computed torque technique and excellent performance was demonstrated in a simulation study. The method has also been applied experimentally to an industrial spray-painting robot where a saw-tooth reference was tracked. The corner was rounded extremely well, and the steady-state tracking error was eliminated by the optimal feedforward. Robots, path planning,

oai:mic.1989.3.1 2010-03-20

eng Journal article 1989-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1989-3-1.asp Fulltext http://www.mic-journal.no/PDF/1989/MIC-1989-3-1.pdf Performance evaluation of positive regulators for population control Muratori, Simona Rinaldi, Sergio Trinchera, Bruno This paper deals with real time control of age-structured populations described by Leslie models with positive inputs. The classical industrial and pole-assignment regulators are adapted to this class of positive systems and their performance is evaluated through simulation. The influence of noise on cost and robustness of the controlled system and the role of the information structure are discussed in some detail. Pole assignment, industrial regulators, Leslie systems, population control,

oai:mic.1989.3.2 2010-03-20

eng Journal article 1989-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1989-3-2.asp Fulltext http://www.mic-journal.no/PDF/1989/MIC-1989-3-2.pdf Role of computational efficiency in process simulation Strand, Kurt Nordhus, Håvard Singstad, Peter Hillestad, Magne It is demonstrated how efficient numerical algorithms may be combined to yield a powerful environment for analysing and simulating dynamic systems. The importance of using efficient numerical algorithms is emphasized and demonstrated through examples from the petrochemical industry. Dynamic simulation, integration algorithms, steady state solvers,

oai:mic.1989.3.3 2010-03-20

eng Journal article 1989-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1989-3-3.asp Fulltext http://www.mic-journal.no/PDF/1989/MIC-1989-3-3.pdf SIMLAB. A training simulator for emergency preparedness decisions Drager, Harald K. Soma, Helge Gulliksen, Roy The paper describes an EDP-simulation program package SIMLAB (Simulation Laboratory) which is under development for Esso Norge A/S by A/S Quasar Consultants. SIMLAB is a simulation training course for personnel involved in safety and contingency planning and/or personnel who have operative responsibility for such matters. In order to perform a simulation an offshore platform is modeled with respect to accident development, escapeways etc. Also its surrounding fields and platforms with their rescue resources are included. SIMLAB containts the following program modules: Simulator, emergency,

oai:mic.1989.3.4 2010-03-20

eng Journal article 1989-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1989-3-4.asp Fulltext http://www.mic-journal.no/PDF/1989/MIC-1989-3-4.pdf HVAC-DYNAMIC: a training simulator for dynamic analysis of HVAC plants Heintz, Morten Novakovic, Vojislav Øgård, Ommund Brustad, Georg HVAC-DYNAMIC is a software tool for the dynamic simulation of Heating, Ventilation and Air Conditioning (HVAC) plants. The program is designed to be used by HVAC engineers during design or troubleshooting of plants and by plant operators in their training. The program is based on a set of the most-used HVAC plant configurations and requires only a minimum of knowledge in numeric methods and programming. A brief presentation of the program structure and examples showing some of the application of the program are given. Air conditioning, modeling, dynamic analysis,

oai:mic.1989.3.5 2010-03-20

eng Journal article 1989-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1989-3-5.asp Fulltext http://www.mic-journal.no/PDF/1989/MIC-1989-3-5.pdf Control elements in mechanism simulation Iversen, Torleif The work reported in this paper is a step towards a system for multidisciplinary simulation of structure, mechanism and control elements. The control part of the system is implemented as a subroutine called from the mechanism/FEM package. While Newmark's/beta-method is used to integrate the second order mechanism/FEM part, the Lobatto IIIC algorithm is applied to the first order control elements. Preliminary experiments show that this is a workable solution. The package will be further developed to include more elements, improve the performance and add enhanced graphics. The control part can easily be used as a stand alone simulator for the integration of first order differential/algebraic equations. Initial value problem, dynamic simulation, mechanism,

oai:mic.1989.3.6 2010-03-20

eng Journal article 1989-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1989-3-6.asp Fulltext http://www.mic-journal.no/PDF/1989/MIC-1989-3-6.pdf User experience with on-line predictive river flow regulation Foss, Bjarne A. Haug, J.E. Alne, J. Aam, Sverre A control strategy based on adaptive prediction and a receding horizon controller is used to regulate the river flow-rate in Suldalslågen in the Ulla-Førre production system on the south-west coast of Norway. The adaptive prediction of the unregulated inflow used precipitation data and flow-rate data from a stream in the catchment area. In addition, a recursive estimation algorithm is used to estimate the stationary gains of the parallel transfer function models which have the catchment area data as input and the unregulated inflow as output. River flow regulation, control, adaptive prediction,

oai:mic.1989.4.1 2010-03-20

eng Journal article 1989-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1989-4-1.asp Fulltext http://www.mic-journal.no/PDF/1989/MIC-1989-4-1.pdf Effective use of full scale simulators for training Malik, Tahir I. A full scale process simulator is a type of simulator which is comprehensive in the details of the plant simulated, emulated or replicated. The experience of use of non-nuclear, full scale process simulators is relatively fresh. There is enormous scope for increased or more effective utilization through rationalized analysis carried out from different perspectives or points of view. It is argued that the chemical engineering perspective is of fundamental importance for process plants and may not have been given its due importance so far. The effective use of these, usually large investment, simulators for training is analysed from a chemical engineering view-point and resulting ideas and recommendations presented. Another perspective investigated is that of the simulator designer. The maximum utilization of the simulators will depend upon optimal use of the functions and facilities built in by the designer. The possible use by the instructor or the trainee of the simulator development tools and utilities is discussed. Two examples of full scale simulators are the Gullfaks and Oseberg Production Platform Simulators, operated presently be Statoil and Norsk Hydro respectively and designed and built by NorControl Simulation. These simulators are referred to in the paper as appropriate examples. The most obvious perspectives, that of the instructor and the trainee, are also touched upon. It is argued that human teachers or instructors remain critically important elements in training sessions carried out in the presence of full scale simulators. The effective use of the simulator will depend heavily on the proficiency of the instructors. Speculations are made into the future developments in the methodology of use of simulators. Dynamic process simulators, operator training,

oai:mic.1989.4.2 2010-03-20

eng Journal article 1989-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1989-4-2.asp Fulltext http://www.mic-journal.no/PDF/1989/MIC-1989-4-2.pdf Simultaneous computation within a sequential process simulation tool Endrestøl, G. Sira, Terje Østenstad, Monica Malik, Tahir I. Meeg, M. Thrane, J. The paper describes an equation solver superstructure developed for a sequential modular dynamic process simulation system as part of a Eureka project with Norwegian and British participation. The purpose of the development was combining some of the advantages of equation based and purely sequential systems, enabling implicit treatment of key variables independent of module boundaries, and use of numerical integration techniques suitable for each individual type of variable. For training simulator applications the main advantages are gains in speed due to increased stability limits on time steps and improved consistency of simulation results. The system is split into an off-line analysis phase and an on-line equation solver. The off-line processing consists of automatic determination of the topological structure of the system connectivity from standard process description files and derivation of an optimized sparse matrix solution procedure for the resulting set of equations. The on-line routine collects equation coefficients from involved modules, solves the combined sets of structured equations, and stores the results appropriately. This method minimizes the processing cost during the actual simulation. The solver has been applied in the Veslefrikk training simulator project. Dynamic process simulation, sequential modular simulator,

oai:mic.1989.4.3 2010-03-20

eng Journal article 1989-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1989-4-3.asp Fulltext http://www.mic-journal.no/PDF/1989/MIC-1989-4-3.pdf Simulation of gas kicks during oil well drilling Rommetveit, Rolv Blyberg, Anette A computer simulator is needed to calculate expected development of gas kicks. Such a simulator is presented, and some simulation examples are shown. The model is flexible, and can be used for research studies, well planning and training purposes. Several simulation examples are shown which illustrate some of the differences between kicks in WBM and OBM. Computer simulator, gas kicks,

oai:mic.1989.4.4 2010-03-20

eng Journal article 1989-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1989-4-4.asp Fulltext http://www.mic-journal.no/PDF/1989/MIC-1989-4-4.pdf Simulation of gas explosions Hjertager, Bjørn H. Gas explosion hazard assessments in flammable gas handling operations both offshore and onshore are crucial in order to obtain an acceptable level of safety. In order to perform such assessments good predictive tools are needed, which take account of the relevant parameters, such as geometrical design variables and gas cloud type and distribution. A theoretical simulation model must therefore be tested against sufficient experimental evidence prior to becoming a useful tool. The experimental data should include both variations in geometry and gas cloud composition and the model should give reasonable predictions without use of geometry or case dependent constants. Fluid dynamics, combustion,

oai:mic.1990.1.1 2010-03-20

eng Journal article 1990-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1990-1-1.asp Fulltext http://www.mic-journal.no/PDF/1990/MIC-1990-1-1.pdf Structural Solution of Highly Redundant Sensing in Robotic Systems Balchen, Jens G. Dessen, Fredrik Reasons for and problems concerning the integration of large number of sensors in robotic systems are discussed. These include data collection, coordination and integration by means of state estimation. The need for unified approaches in handling highly redundant sensory systems is stated and solutions suggested. Robots, sensory systems,

oai:mic.1990.1.2 2010-03-20

eng Journal article 1990-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1990-1-2.asp Fulltext http://www.mic-journal.no/PDF/1990/MIC-1990-1-2.pdf Improved heuristic algorithm for selection of tear streams and precedence ordering in process flowsheeting computations Lien, Kristian M. Hertzberg, Terje This paper presents a new algorithm based on the heuristic tearing algorithm by Gundersen and Hertzberg (1983). The basic idea in both the original and the proposed algorithm is sequential tearing of strong components which have been identified by an algorithm proposed by Targan (1972). The new algorithm has two alternative options for selection of tear streams, and alternative precedence orderings may be generated for the selected set of tear streams. The algorithm has been tested on several problems. It has identified minimal (optimal) tear sets for all of them, including the four problems presented in Gundersen and Hertzberg (1983) where the original algorithm could not find a minimal tear set. A Lisp implementation of the algorithm is described, and example problems arc presented. Tearing, decomposition, precedence ordering,

oai:mic.1990.1.3 2010-03-20

eng Journal article 1990-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1990-1-3.asp Fulltext http://www.mic-journal.no/PDF/1990/MIC-1990-1-3.pdf Analysis of manufacturing based on object oriented discrete event simulation Borgen, Eirik Neerland, Henning Strandhagen, Jan O. This paper describes SIMMEK, a computer-based tool for performing analysis of manufacturing systems, developed at the Production Engineering Laboratory, NTH-SINTEF. Its main use will be in analysis of job shop type of manufacturing. But certain facilities make it suitable for FMS as well as a production line manufacturing. This type of simulation is very useful in analysis of any types of changes that occur in a manufacturing system. These changes may be investments in new machines or equipment, a change in layout, a change in product mix, use of late shifts, etc. The effects these changes have on for instance the throughput, the amount of VIP, the costs or the net profit, can be analysed. And this can be done before the changes are made, and without disturbing the real system. Simulation takes into consideration, unlike other tools for analysis of manufacturing systems, uncertainty in arrival rates, process and operation times, and machine availability. It also shows the interaction effects a job which is late in one machine, has on the remaining machines in its route through the layout. It is these effects that cause every production plan not to be fulfilled completely. SIMMEK is based on discrete event simulation, and the modeling environment is object oriented. The object oriented models are transformed by an object linker into data structures executable by the simulation kernel. The processes of the entity objects, i.e. the products, are broken down to events and put into an event list. The user friendly graphical modeling environment makes it possible for end users to build models in a quick and reliable way, using terms from manufacturing. Various tests and a check of model logic are helpful functions when testing validity of the models. Integration with software packages, with business graphics and statistical functions, is convenient in the result presentation phase. Discrete event simulation, economical analysis, graphical modeling,

oai:mic.1990.1.4 2010-03-20

eng Journal article 1990-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1990-1-4.asp Fulltext http://www.mic-journal.no/PDF/1990/MIC-1990-1-4.pdf Improvements in metallurgical processes by simulation Solberg, Kjell O. The metallurgical industry is very important to Norway. Traditionally cheap hydro-power has been the basis for this energy-intensive industry. This advantage is now gradually disappearing. To be competitive in the future, a superior technology has to be developed. For this purpose simulation has been taken into extensive use. Close cooperation is established between the industry and research institutes. This is vital for success. Simulation has proved to be an important tool in two areas: the optimum design of processes and the continuous supervision to keep them running at optimum. This paper gives examples of how substantial improvements have been obtained in the production of aluminium and ferro-alloys. Based on this experience the author draws some general conclusions on how to utilize simulation to increase industrial productivity. In the future a new area is envisaged; simulation in the development of advanced materials and products. Metallurgy, simulation, process design,

oai:mic.1990.1.5 2010-03-20

eng Journal article 1990-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1990-1-5.asp Fulltext http://www.mic-journal.no/PDF/1990/MIC-1990-1-5.pdf A Schur Method for Designing LQ-optimal Systems with Prescribed Eigenvalues Di Ruscio, David Balchen, Jens G. In this paper a new algorithm for solving the LQ-optimal pole placement problem is presented. The method studied is a variant of the classical eigenvector approach and instead uses a set of Schur vectors, thereby gaining substantial numerical advantages. An important task in this method is the LQ-optimal pole placement problem for a second order (sub) system. The paper presents a detailed analytical solution to this problem. This part is not only important for solving the general n-dimensional problem but also provides an understanding of the behaviour of an optimal system: The paper shows that in some cases it is an infinite number; in others a finite number, and in still others, non state weighting matrices Q that give the system a set of prescribed eigenvalues. Equations are presented that uniquely determine these state weight matrices as a function of the new prescribed eigcnvalues. From this result we have been able to derive the maximum possible imaginary part of the eigenvalues in an LQ-optimal system, irrespective of how the state weight matrix is chosen. Linear optimal regulator, pole placement, multivariable control systems, control system design, computer-aided design,

oai:mic.1990.2.1 2010-03-20

eng Journal article 1990-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1990-2-1.asp Fulltext http://www.mic-journal.no/PDF/1990/MIC-1990-2-1.pdf Multivariable robust adaptive controller using reduced-order model Hillestad, Magne Sørlie, C. Anderson, T.F. Olsen, I. Hertzberg, Terje A general method is developed for predicting the deviation between local and rigorous thermodynamic property models. The method is based on a quadratic error structure. The curvature matrix is updated after each parameter revision. The updating scheme utilizes the observed deviation as a measure for correcting the matrix and thus does not require any additional rigorous model evaluations. A recursive least squares procedure with variable forgetting is adopted for the parameter updating. A local model structure for K-value evaluations is applied in a dynamic simulation model of a batch distillation column. The efficiency and accuracy of the proposed method are tested for two different mixtures; a nearly ideal and a strongly non-ideal mixture. Local models, adaptive error estimation, dynamic simulation,

oai:mic.1990.2.2 2010-03-20

eng Journal article 1990-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1990-2-2.asp Fulltext http://www.mic-journal.no/PDF/1990/MIC-1990-2-2.pdf Multivariable robust adaptive controller using reduced-order model Wang, Wei In this paper a multivariable robust adaptive controller is presented for a plant with bounded disturbances and unmodeled dynamics due to plant-model order mismatches. The robust stability of the closed-loop system is achieved by using the normalization technique and the least squares parameter estimation scheme with dead zones. The weighting polynomial matrices are incorporated into the control law, so that the open-loop unstable or/and nonminimum phase plants can be handled. Adaptive control, multivariable systems, stability,

oai:mic.1990.2.3 2010-03-20

eng Journal article 1990-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1990-2-3.asp Fulltext http://www.mic-journal.no/PDF/1990/MIC-1990-2-3.pdf The Stability of 2x2 Multivariable Control Systems Balchen, Jens G. The paper develops simple but powerful expressions for the investigation of stability and response of 2x2 multivariable control systems. The analytical results can be given convenient graphical representations. This provides a helpful tool for obtaining deep insight into the behaviour of this type of system which is particularly important in process control. Two simple examples illustrate the application of the method. Stability,

oai:mic.1990.2.4 2010-03-20

eng Journal article 1990-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1990-2-4.asp Fulltext http://www.mic-journal.no/PDF/1990/MIC-1990-2-4.pdf Practical Trajectory Learning Algorithms for Robot Manipulators Lunde, Erling Balchen, Jens G. Several alternative learning control algorithms are discussed, both from an inverse dynamics and an optimization point of view. The learning laws are derived in discrete time and do not need acceleration measurements. A simple algorithm using a constant learning operator is proposed to run in addition to a simple (PD) feedback controller. Its performance is comparable to other algorithms, and it works under non-ideal conditions where the others fail. Two simulation examples on (1) learning dynamic control, and (2) learning optimal redundancy resolution, are presented.

oai:mic.1990.2.5 2010-03-20

eng Journal article 1990-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1990-2-5.asp Fulltext http://www.mic-journal.no/PDF/1990/MIC-1990-2-5.pdf A Note on a necessary condition for optimality Di Ruscio, David A necessary condition is derived for the optimality of a linear multivariable feedback control system with respect to a quadratic performance index of infinite settling time. Linear optimal control, multivariable systems, pole placements, eigenvalues,

oai:mic.1990.3.1 2010-03-20

eng Journal article 1990-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1990-3-1.asp Fulltext http://www.mic-journal.no/PDF/1990/MIC-1990-3-1.pdf Rational Transfer Function Approximations to Transport Delay Balchen, Jens G. A method is presented for determining a rational transfer function approximation to transport delay which has the property that the error in the frequency response phase shift is zero at certain frequencies. This new approximation is particularly suitable for the determination of stability conditions for feedback systems containing transport delay. Transport delay approximation,

oai:mic.1990.3.2 2010-03-20

eng Journal article 1990-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1990-3-2.asp Fulltext http://www.mic-journal.no/PDF/1990/MIC-1990-3-2.pdf Mechanical networks model for the truss system in structural engineering Wang, Kesheng Bjørke, Øyvind This paper demonstrates how to use a mechanical networks model to analyse a three-dimensional truss system in structural engineering. A three-dimensional numerical example with a complete program written in the APL programming language is presented. The principles and concepts of this method are easily understood, and the formulation and computation of the problem can be carried out systematically and consistently. The main purpose is to develop a uniform, systematic theory and method which can be employed in the design process to analyse and synthesise a great number of engineering or non-engineering systems, such as mechanical, electrical, economic systems. The mechanical networks model presented in this paper has proved to be ideal for this type of analysis. Graph theory, system theory, networks, design theory, truss system,

oai:mic.1990.3.3 2010-03-20

eng Journal article 1990-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1990-3-3.asp Fulltext http://www.mic-journal.no/PDF/1990/MIC-1990-3-3.pdf An Algorithm for Design of Decentralized Suboptimal Controllers with Specified Structure Di Ruscio, David Balchen, Jens G. In this paper we present a method for the design of controllers with a specified arbitrary structure for linear multivariable time invariant systems. Both decentralized controllers as well as feedback from a reduced state vector can be designed by this method. The controller will become optimal in the sense that it yields a minimum of a quadratic cost criterion and suboptimal in the sense that it yields a higher value of this criterion than a controller without restrictions. The algorithm makes it possible to specify a stability margin on the feedback system. This means that the feedback system will have eigenvalues located to the left of a certain line (-alpha) in the complex plane. The unknown parameters of the controller are collected in a parameter vector. The algorithm is based upon a modified Newton-method for searching towards the 'optimal' parameter vector. The algorithm ensures that the closed loop system is stable at any iteration in the case of an initially stable plant, and after the final iteration in the case of an initially unstable plant. Control system design, decentralized control, linear optimal control,

oai:mic.1990.3.4 2010-03-20

eng Journal article 1990-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1990-3-4.asp Fulltext http://www.mic-journal.no/PDF/1990/MIC-1990-3-4.pdf Adaptive feedback linearization of non-linear systems with significant actuator dynamics Fossen, Thor I. When applying feedback linearization techniques actuator dynamics is usually neglected. This is crucial for actuators with large time constants. A large class of systems, e.g. chemical processes, belong to this category. In such cases conventional feedback linearization techniques based on adaptive control or sliding control perform poorly. This paper discusses an approach which allows the inclusion of the actuator dynamics in the controller design. The design methodology has validation both for adaptive feedback linearization as well as sliding control. An augmented Lyapunov-like function candidate including the actuator states was used to prove global stability. This is done by applying Barbalat's Lyapunov-like lemma for non-autonomous systems. The control law is simulated for both the nominal and adaptive cases. In the adaptive case both the plant parameters and the actuator time constant are assumed to be unknown. Actuator dynamics, non-linear control, Lyapunov stability theory, adaptive feedback linearization,

oai:mic.1990.4.1 2010-03-20

eng Journal article 1990-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1990-4-1.asp Fulltext http://www.mic-journal.no/PDF/1990/MIC-1990-4-1.pdf Density driven currents in the Barents Sea calculated by a numerical model Slagstad, Dag Støle-Hansen, Kjell Loeng, Harald A baroclinic, 3-D model is described. It is adapted to a Barents Sea situation in order to simulate the currents in this area. The model is of a so-called level type which contains fixed, but permeable levels. It also includes thermodynamics which allow freezing and melting of ice. Using density data obtained during the autumn of 1988, a current pattern, driven by density and bottom topography is simulated. No wind is applied. The simulated current pattern gives an overall picture which is similar to what is observed through the few measurements that are available. Good agreements with the observations is found on the Svalbard bank, Tromsøflaket and along the Novaya Zemlya Coast. In the Bear Island/Hopen depth the model predicts a large eddy which has not been observed. Several smaller, topographical steared eddies are seen in the eastern part of the model area. Hydrodynamical model, simulation,

oai:mic.1990.4.2 2010-03-20

eng Journal article 1990-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1990-4-2.asp Fulltext http://www.mic-journal.no/PDF/1990/MIC-1990-4-2.pdf A Combined Network Architecture Using Art2 and Back Propagation for Adaptive Estimation of Dynamic Processes Sørheim, Einar A neural network architecture called ART2/BP is proposed. Thc goal has been to construct an artificial neural network that learns incrementally an unknown mapping, and is motivated by the instability found in back propagation (BP) networks: after first learning pattern A and then pattern B, a BP network often has completely 'forgotten' pattern A. A network using both supervised and unsupervised training is proposed, consisting of a combination of ART2 and BP. ART2 is used to build and focus a supervised backpropagation network consisting of many small subnetworks each specialized on a particular domain of the input space. The ART2/BP network has the advantage of being able to dynamically expand itself in response to input patterns containing new information. Simulation results show that the ART2/BP network outperforms a classical maximum likelihood method for the estimation of a discrete dynamic and nonlinear transfer function. System identification, nonlinear systems, adaptive control, artificial neural networks, back propagation,

oai:mic.1990.4.3 2010-03-20

eng Journal article 1990-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1990-4-3.asp Fulltext http://www.mic-journal.no/PDF/1990/MIC-1990-4-3.pdf An Efficient Pseudo-Inverse Solution to the Inverse Kinematic Problem for 6-Joint Manipulators Chiaverini, Stefano Egeland, Olav The use of the pseudo-inverse Jacobian matrix makes the solution of the inverse kinematic problem well-defined even at singular configurations of the robot arm, in the neighbourhood of a singularity, however, the computed solution often results in high joint velocities which may not be feasible to the real manipulator. Furthermore, the pseudo-inverse solution is computationally expensive, thus preventing real-time applications. Robotics, inverse kinematics,

oai:mic.1990.4.4 2010-03-20

eng Journal article 1990-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1990-4-4.asp Fulltext http://www.mic-journal.no/PDF/1990/MIC-1990-4-4.pdf Convergence Aspects of Some Robust Estimators Based Upon Prefiltering of the Input-Output Data Henriksen, Rolf Weyer, Erik By prefiltering the input/output data and employing certain decentralized estimation techniques, it is possible to improve the robustness of some estimators significantly. Earlier papers on these techniques have been focused on local convergence properties of certain bootstrap estimators based upon these techniques. This paper is devoted to (1) global convergence properties, and (2) convergence rates when the underlying system is stiff. Decentralized estimation, least squares method, instrumental variable methods, bootstrap estimators, robust estimation, global convergence, convergence rates,

oai:mic.1991.1.1 2010-03-20

eng Journal article 1991-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1991-1-1.asp Fulltext http://www.mic-journal.no/PDF/1991/MIC-1991-1-1.pdf Estimation of Regurgitant Volume and Orifice in Aortic Regurgitation Combining CW Doppler and Parameter Estimation in a Windkessel Like Model Angelsen, Bjørn A.J. Slørdahl, S.A. Solbakken, J.E. Samstad, S.O. Linker, D.T. Torp, H. Piene, H. A method for noninvasive estimation of regurgitant orifice and volume in aortic regurgitation is proposed and tested in anaesthesized open chested pigs. The method can be used with noninvasive measurement of regurgitant jet velocity with continuous wave ultrasound Doppler measurements together with cuff measurements of systolic and diastolic systemic pressure in the arm. These measurements are then used for parameter estimation in a Windkessel-like model which include the regurgitant orifice as a parameter. The aortic volume compliance and the peripheral resistance are also included as parameters and estimated in the same process. For the test of the method, invasive measurements in the open chest pigs are used. Electromagnetic flow measurements in the ascending aorta and pulmonary artery are used for control, and a correlation between regurgitant volume obtained from parameter estimation and electromagnetic flow measurements of 0.95 over a range from 2.1 to 17.8 mL is obtained. Regurgitant orifice, noninvasive estimation, ultrasound,

oai:mic.1991.1.2 2010-03-20

eng Journal article 1991-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1991-1-2.asp Fulltext http://www.mic-journal.no/PDF/1991/MIC-1991-1-2.pdf Using Momentum Conservation to Control Kinematically Redundant Manipulators Sagli, Jan R. Egeland, Olav A control scheme for the coordination of motion in a macro-micro manipulator system is presented. The motion of the end-effector is decoupled from the rest of the system using resolved acceleration control, while a slow, gross positioning is used for the macro part. To avoid saturated inputs and excessive use of energy for systems with limited fuel, the end effector is not decoupled from macro part motion, but from selected directions of the linear momentum of the total system. For the vehicle-manipulator case, the end-effector is decoupled also from the angular momentum. This leads to lower force and torque peaks in the actuators, and control force is used on the macro part only when it is necessary to reposition this to keep the micro part inside its workspace. Robotics, momentum conservation,

oai:mic.1991.1.3 2010-03-20

eng Journal article 1991-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1991-1-3.asp Fulltext http://www.mic-journal.no/PDF/1991/MIC-1991-1-3.pdf Transient Simulations of Gas-Oil-Water Separation Plants Schei, Tor S. Singstad, Peter Thunem, Aage J. A set of mathematical models for the dynamic simulation of offshore processing plants is developed. Each process unit is modeled separately, and the various models are integrated into a system for the simulation of an entire plant. The purpose of the simulation system is to study the effects of various disturbances and investigate appropriate control strategies. Important variables subject to control are pressure, flow rate, temperature, vessel liquid level and compressor speed. In separators the rate of interfacial mass transfer between the liquid and vapour phases at non-equilibrium is modeled as a first order time lag. The vapour liquid equilibrium ratio is linearized with respect to variations in pressure and temperature for each separator stage. A realistic scenario is chosen in order to demonstrate the capabilities of the simulation system. Dynamic simulation, oil processing,

oai:mic.1991.1.4 2010-03-20

eng Journal article 1991-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1991-1-4.asp Fulltext http://www.mic-journal.no/PDF/1991/MIC-1991-1-4.pdf A Recursive Algorithm for the Reduction of Block Diagrams Andresen, Trond A recursive algorithm to compute input-output relationships in a network of rational transfer functions (a block diagram) is derived. Initially all transfer functions are disconnected. For each step in the algorithm, a new transfer function in the network is connected to the system. One application of the algorithm is to find the transfer matrix of a linear multivariable system given on state space form. The algorithm is advantageous when one needs repeated computations of a transfer matrix in a multivariable system for successive changes in one or a few parameters in the system. The transfer matrix for a multivariable linear system with one time delay, and the exact frequency response in the case of several time delays, are derived. Block diagram reduction, recursive algorithm, transfer matrix,

oai:mic.1991.2.1 2010-03-20

eng Journal article 1991-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1991-2-1.asp Fulltext http://www.mic-journal.no/PDF/1991/MIC-1991-2-1.pdf The Norwegian research programme on advanced robotic systems Egeland, Olav The Norwegian research programme on advanced robot systems has been focused on sensory control of robots for industrial applications and telerobotics for underwater operations. This paper gives an overview of experimental work and ongoing research. An exciting area in sensory control is visual servoing where camera images at video rate are used to grasp moving objects. Also compliant motion in partially unknown environments is a research topic. New robot control systems have been developed to apply sensory control to robotic manipulators at an acceptable sampling rate. In telerobotics the main work has been on the combination of remote control and local sensory loops in the manipulator. Also in this case visual servoing anti force control are important. The generation and updating of a world model used in a graphic display of the worksite using sensory information has been tested in combination with large delay times in the communication channel. The use of visual and acoustic data for the control of remotely operated vehicles and autonomous underwater vehicles is studied for use in robotic systems. Light-weight robot manipulators with redundant degrees of freedom and high performance joints are being designed for mobile robot applications. Robotics, ROV, telerobotics, sensory robot control, subsea robotics,

oai:mic.1991.2.2 2010-03-20

eng Journal article 1991-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1991-2-2.asp Fulltext http://www.mic-journal.no/PDF/1991/MIC-1991-2-2.pdf Sensor Integration Using State Estimators Balchen, Jens G. Dessen, F. Skofteland, G. Means for including very different types of sensors using one single unit are described. Accumulated data are represented using an updatable dynamic model, a Kalman filter. The scheme handles common phenomena such as skewed sampling, finite resolution measurements and information delays. Included is an example where 3D motion information is collected by one or more vision sensors. Sensor integration, Kalman filter, 3-D motion estimation,

oai:mic.1991.2.3 2010-03-20

eng Journal article 1991-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1991-2-3.asp Fulltext http://www.mic-journal.no/PDF/1991/MIC-1991-2-3.pdf Nonlinear Decoupling in Process Control Balchen, Jens G. The principle of nonlinear decoupling as a general approach to the control of nonlinear processes is reviewed. A novel technique is introduced for resolving the inverse problem in case the nonlinear process function does not have a closed-form inverse. The paper also indicates the relationships between nonlinear decoupling, 'cascade control' and 'sliding mode control'. Nonlinearity, decoupling, inverse dynamics,

oai:mic.1991.2.4 2010-03-20

eng Journal article 1991-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1991-2-4.asp Fulltext http://www.mic-journal.no/PDF/1991/MIC-1991-2-4.pdf Adaptive control of nonlinear underwater robotic systems Fossen, Thor I. Sagatun, Svein I. The problem of controlling underwater mobile robots in 6 degrees of freedom (DOF) is addressed. Uncertainties in the input matrix due to partly known nonlinear thruster characteristics are modeled as multiplicative input uncertainty. This paper proposes two methods to compensate for the model uncertainties: (1) an adaptive passivity-based control scheme and (2) deriving a hybrid (adaptive and sliding) controller. The hybrid controller consists of a switching term which compensates for uncertainties in the input matrix and an on-line parameter estimation algorithm. Global stability is ensured by applying Barbalat's Lyapunovlike lemma. The hybrid controller is simulated for the horizontal motion of the Norwegian Experimental Remotely Operated Vehicle (NEROV). AUV, ROV, adaptive control,

oai:mic.1991.3.1 2010-03-20

eng Journal article 1991-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1991-3-1.asp Fulltext http://www.mic-journal.no/PDF/1991/MIC-1991-3-1.pdf A simplified algorithm of weighted generalized predictive adaptive control Wang, Wei Henriksen, Rolf In this paper a weighted generalized predictive controller and a simplified adaptive control algorithm using a multi-step cost-function with polynomial weighting are presented. A simulation example and a comparison of computational loads are also given in order to show the performance of the controller. Predictive control,

oai:mic.1991.3.2 2010-03-20

eng Journal article 1991-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1991-3-2.asp Fulltext http://www.mic-journal.no/PDF/1991/MIC-1991-3-2.pdf The Stability of mxm Multivariable Process Control Systems Balchen, Jens G. A technique is described for the investigation of conditions of stability of a mxm multivariable process controlled by m independent controllers in terms of the parameters of the m uncoupled control systems and the transfer functions of the cross-coupling elements. The method is an extension of a similar result for 2 x 2 systems (Balchen 1990). The analytical results are given convenient graphical representations by means of standard frequency response techniques yielding a simple, but powerful tool for synthesis of multiple controllers for multivariable processes. Stability,

oai:mic.1991.3.3 2010-03-20

eng Journal article 1991-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1991-3-3.asp Fulltext http://www.mic-journal.no/PDF/1991/MIC-1991-3-3.pdf Sliding control of MIMO nonlinear systems Fossen, Thor I. Foss, Bjarne A. Sliding control of MIMO (multivariable input multivariable output) nonlinear minimum phase systems is discussed. Stability conditions related to model errors are emphasized. Global asymptotic stability is guaranteed by applying Barbalat's Lyapunov-like lemma. The control law is applied to a simulator of a polymerization reactor. Feedback linearization, sliding control, Lyapunov stability theory,

oai:mic.1991.3.4 2010-03-20

eng Journal article 1991-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1991-3-4.asp Fulltext http://www.mic-journal.no/PDF/1991/MIC-1991-3-4.pdf Globally convergent generalized pole-placement adaptive control algorithm Wang, Wei Henriksen, Rolf A complete proof of global convergence of a generalized pole-placement adaptive control algorithm for linear discrete-time plants with an unmeasured bounded disturbance is given in this paper. The analysis shows that the difficulty encountered in the convergence analysis is circumvented by fixing the parameters which enter nonlinearly into the control law to some constant value. This allows us to use the standard analysis techniques for adaptive control in the analysis of our control algorithm. Predictive control, adaptive control, pole-placement, convergence,

oai:mic.1991.3.5 2010-03-20

eng Journal article 1991-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1991-3-5.asp Fulltext http://www.mic-journal.no/PDF/1991/MIC-1991-3-5.pdf Maximal imaginery eigenvalues in optimal systems Di Ruscio, David In this note we present equations that uniquely determine the maximum possible imaginary value of the closed loop eigenvalues in an LQ-optimal system, irrespective of how the state weight matrix is chosen, provided a real symmetric solution of the algebraic Riccati equation exists. In addition, the corresponding state weight matrix and the solution to the algebraic Riccati equation are derived for a class of linear systems. A fundamental lemma for the existence of a real symmetric solution to the algebraic Riccati equation is derived for this class of linear systems. Linear optimal control, pole placement, eigenvalues, multivariable control systems,

oai:mic.1991.4.1 2010-03-20

eng Journal article 1991-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1991-4-1.asp Fulltext http://www.mic-journal.no/PDF/1991/MIC-1991-4-1.pdf Simple frequency-dependent tools for analysis of inherent control limitations Skogestad, Sigurd Hovd, Morten Lundström, Petter By a plant's inherent control limitations we mean the characteristics of the plant which will cause poor control performance irrespective of what controller is used. Another frequently used term is 'dynamic resilience' which is the best closed-loop performance achievable using any controller. Since a plant's dynamic resilience cannot be altered by change of the control algorithm, but only by design modifications, it follows that the term controllability provides a link between process design and process control. In this paper we focus on two aspects of controllability. The plants' sensitivity to disturbances and the limitations imposed by interactions when using decentralized control. We use simple tools such as the RGA, the PRGA (Performance RGA) and the closely related Closed Loop Disturbance Gain (CLDG). For example, if kth column of the CLDG is large, then this indicates that disturbance k will be difficult to reject. This may pinpoint the need for modifying the process. The PRGA provides a measure of interaction which also includes one-way coupling. In the paper we apply these measures to distillation column control and fluid catalytic cracker (FCC) control. Dynamic resilience, relative gain array, disturbance rejection,

oai:mic.1991.4.2 2010-03-20

eng Journal article 1991-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1991-4-2.asp Fulltext http://www.mic-journal.no/PDF/1991/MIC-1991-4-2.pdf On unsteady reacting flow in a channel with a cavity Sand, Ivar Ø. The problem investigated is the stability of a flame anchored by recirculation within a channel with a cavity, acting as a two-dimensional approximation to a gas turbine combustion chamber. This is related to experiments of Vaneveld, Hom and Oppenheim (1982). The hypothesis studied is that hydrodynamic oscillations within the cavity can lead to flashback. Unsteady reacting flow, vortex method, simple line interface calculation,

oai:mic.1991.4.3 2010-03-20

eng Journal article 1991-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1991-4-3.asp Fulltext http://www.mic-journal.no/PDF/1991/MIC-1991-4-3.pdf Possible roles of remotely operated underwater vehicles (ROV) and robotics in mariculture of the future Balchen, Jens G. The paper surveys some possible future trends in mariculture technology emphasizing new principles for controlling animal motion. Against this background possible applications of remotely operated underwater vehicles and robotics are reviewed. Mariculture, Aquaculture, Robotics, ROV, Control,

oai:mic.1992.1.1 2010-03-20

eng Journal article 1992-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1992-1-1.asp Fulltext http://www.mic-journal.no/PDF/1992/MIC-1992-1-1.pdf On the location of LQ-optimal closed-loop poles Canudas de Wit, Carlos Sørdalen, Ole J. This paper represents an exponentially stable controller for-a-two-degree-of freedom robot with nonholonomic constraints. Although this type of system is open loop controllable, this system has been shown to be nonstabilizable via pure smooth feedback (Brockett 1983, Samson and Ait-Abderrahim 1991). In this paper, a particular class of piecewise continuous controller is shown to stabilize the system exponentially. This controller has the feature that it does not require infinitely fast switching, as required, for example, by sliding controllers. Control of mobile robots, piecewise continuous controller, non-holonomic constraints,

oai:mic.1992.1.2 2010-03-20

eng Journal article 1992-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1992-1-2.asp Fulltext http://www.mic-journal.no/PDF/1992/MIC-1992-1-2.pdf On the location of LQ-optimal closed-loop poles Di Ruscio, David Inequalities which bound the closed-loop eigenvalues in an LQ-optimal system are presented. It is shown that the eigenvalues are bounded by two half circles with radii r1 and r2 and centre at -alpha less than or equal to 0, where alpha=0 is the imaginary axis, and that the imaginary parts of these eigenvalues are bounded from up and below by two lines parallel to the real axis. Linear optimal control, eigenvalues, inequalities,

oai:mic.1992.1.3 2010-03-20

eng Journal article 1992-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1992-1-3.asp Fulltext http://www.mic-journal.no/PDF/1992/MIC-1992-1-3.pdf A NARMAX model representation for adaptive control based on local models Johansen, Tor A. Foss, Bjarne A. Here we address the problem of representing NARMAX (nonlinear ARMAX) models with application to adaptive control. We propose a nonlinear model representation where a number of simple local models are combined. The local models are valid in specific operation regimes of the process. Explicitly defined model validity functions make it possible to combine the local models by interpolation. During online identification, only the local models corresponding to the current process operation regime are updated. It is therefore not necessary to relearn the model each time there is a change in the operation regime of the process. The concept is illustrated by a simulation example of a nonlinear pH-neutralization process. Nonlinear systems, adaptive control, model representation, system identification,

oai:mic.1992.1.4 2010-03-20

eng Journal article 1992-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1992-1-4.asp Fulltext http://www.mic-journal.no/PDF/1992/MIC-1992-1-4.pdf A method for the control of alumina concentration in aluminum reduction cells Balchen, Jens G. The paper presents a new method for the control of the concentration of the alumina in electrolysis cells for the production of aluminium. The method is based upon the well known fact that apparent resistivity of the cell is a function of the alumina concentration so that the resistivity has the lowest value around the concentration of three per cent and increases in both directions. The method uses the cross correlation between a perturbation of the feed flow of alumina into the cell and the resulting response in measured voltage across the cell. The cross-correlation is proportional to the slope of the resistivity against concentration curve, making it possible to control the alumina flow, to achieve a desired slope. The method has much in common with other methods presently in use which require a much more complicated computation scheme. Experimenting control, aluminium reduction cell,

oai:mic.1992.1.5 2010-03-20

eng Journal article 1992-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1992-1-5.asp Fulltext http://www.mic-journal.no/PDF/1992/MIC-1992-1-5.pdf The realization of a permanent magnet synchronous motor drive with flux weakening Norum, Lars Ådnanes, Alf K. Sulkowski, Waldemar Aga, Lars A. This paper presents the realization and performance of a fully digital permanent magnet synchronous motor drive. A new control algorithm gives maximum torque to current ratio in both the constant torque region and in flux weakening. Inner loop current control and vector modulation with short calculation time are obtained by thc use of look-up tables. The controller is implemented in a singleboard control computer for power electronics systems, which is based on a 16 bit microcontroller. PMSM drives, flux weakening, digital control,

oai:mic.1992.2.1 2010-03-20

eng Journal article 1992-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1992-2-1.asp Fulltext http://www.mic-journal.no/PDF/1992/MIC-1992-2-1.pdf Multiphase flow metering using capacitance transducer and multivariate calibration Midttveit, Øyvind Berge, Viktor Dykesteen, Eivind The method of multivariate calibration is experimentally investigated to establish estimators of the required pertinent flow parameters in multiphase pipe flow. The unfiltered primary signals, provided by a capacitance sensor, are analysed as discrete time series and the signal characteristics are extracted. The multivariate model that is generated estimates the flow composition based on the extracted information existing in the broad-band capacitance signal. The data analysis and test results are presented. Process measurements, signal processing, feature extraction, chemometrics,

oai:mic.1992.2.2 2010-03-20

eng Journal article 1992-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1992-2-2.asp Fulltext http://www.mic-journal.no/PDF/1992/MIC-1992-2-2.pdf State-space predictive control Balchen, Jens G. Ljungqvist, Dag Strand, Stig This paper deals with a predictive control strategy based on state-space models. Important issues concerning inherent model identification and optimal control computation are briefly discussed. Predictive control relies heavily on a model with satisfactory predictive capabilities. An off-line identification procedure must be accomplished to obtain a proper model structure and a parameter set, which is required for on-line adjustment. The control calculation is based on a general performance index and parameterization of the control variables in a nonlinear model, which includes the relevant constraints. This results in a finite-dimensional optimization problem which can be repetitively solved on-line. Simulation studies on two very different, typical industrial processes are presented. The simulations show that this MPC technique offers a major improvement in the control of many industrial processes. Predictive control, state-space methods, non-linear control system, optimal control, iterative methods, on-line operation,

oai:mic.1992.2.3 2010-03-20

eng Journal article 1992-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1992-2-3.asp Fulltext http://www.mic-journal.no/PDF/1992/MIC-1992-2-3.pdf Variable selection for decentralized control Skogestad, Sigurd Morari, Manfred Decentralized controllers (single-loop controllers applied to multivariable plants) are often preferred in practice because they are robust and relatively simple to understand and to change. The design of such a control system starts with pairing inputs (manipulated variables) and outputs (controlled variables). For a nxn plant there are n! possible pairings, and there is a great need for screening techniques to quickly eliminate undesirable pairings. In this paper we present several tests for eliminating pairings which are not decentralized integral controllable (DIC). A system is DIC if there exists a stabilizing decentralized controller with integral action such that the gains of the individual loops may be reduced independently without introducing instability. Note that the DIC is a property of the plant and the chosen pairings. The tests presented are in terms of different measures of the sign of the steady state gain matrix; including the RGA, the determinant and eigenvalues. The relationship to previously presented results is discussed in detail. DIC, relative gain array (RGA), steady-state, integral control,

oai:mic.1992.3.1 2010-03-20

eng Journal article 1992-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1992-3-1.asp Fulltext http://www.mic-journal.no/PDF/1992/MIC-1992-3-1.pdf Multiple model estimation with inter-residual distance feedback Lund, Eivind J. Balchen, Jens G. Foss, Bjarne A. This paper presents a modification of the Multiple Model Adaptive Estimation concept. A trade-off problem between tracking the process and distinguishing the models is pointed out and an adaption of the elemental filters is proposed. The adaption scheme modifies the filters such that the predicted measurements do not become too close in some sense. This has considerable influence on the distinguishability of the filters and thereby the properties of the Multiple Model Adaptive Estimation algorithm. Stability of the method is considered, and a simulated example demonstrates the method. Adaptive systems, estimation, Kalman filters, parameter estimation, state estimation,

oai:mic.1992.3.2 2010-03-20

eng Journal article 1992-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1992-3-2.asp Fulltext http://www.mic-journal.no/PDF/1992/MIC-1992-3-2.pdf Accuracy of some robust estimators based upon prefiltering of the input/output data Henriksen, Rolf By prefiltering the input/output data and employing certain decentralized estimation techniques, it is possible to improve the robustness of some estimators significantly. Earlier papers on these techniques have been focused on local convergence properties of four bootstrap estimators, a IS variant and three IV variants, global convergence properties of the LS variant, and convergence rates of the LS variant and two of the IV variants when the underlying system is stiff. This paper is devoted to the accuracy properties of the LS variant and one of the IV variants. Parameter estimation, estimation accuracy,

oai:mic.1992.3.3 2010-03-20

eng Journal article 1992-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1992-3-3.asp Fulltext http://www.mic-journal.no/PDF/1992/MIC-1992-3-3.pdf A method for closed loop automatic tuning of PID controllers Schei, Tor S. A simple method for the automatic tuning of PID controllers in closed loop is proposed. A limit cycle is generated through a nonlinear feedback path from the process output to the controller reference signal. The frequency of this oscillation is above the crossover frequency and below the critical frequency of the loop transfer function. The amplitude and frequency of the oscillation are estimated and the control parameters are adjusted iteratively such that the closed loop transfer function from the controller reference to the process output attains a specified amplitude at the oscillation frequency. Adaptive control, closed-loop systems, describing functions, identification, industrial control, limit cycles, Nyquist criterion, PID control,

oai:mic.1992.3.4 2010-03-20

eng Journal article 1992-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1992-3-4.asp Fulltext http://www.mic-journal.no/PDF/1992/MIC-1992-3-4.pdf Computing energy-optimal trajectories for an autonomous underwater vehicle using direct shooting Spangelo, Inge Egeland, Olav Energy-optimal trajectories for an autonomous underwater vehicle can be computed using a numerical solution of the optimal control problem. The vehicle is modeled with the six dimensional nonlinear and coupled equations of motion, controlled with DC-motors in all degrees of freedom. The actuators are modeled and controlled with velocity loops. The dissipated energy is expressed in terms of the control variables as a nonquadratic function. Direct shooting methods, including control vector parameterization (CVP) arc used in this study. Numerical calculations are performed and good results are achieved. ROV, optimal control, nonlinear programming,

oai:mic.1992.3.5 2010-03-20

eng Journal article 1992-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1992-3-5.asp Fulltext http://www.mic-journal.no/PDF/1992/MIC-1992-3-5.pdf Adaptive control of ROVs with actuator dynamics and saturation Fjellstad, Ola-Erik Fossen, Thor I. Egeland, Olav A direct model reference adaptive controller (MRAC) is derived for an underwater vehicle with significant thruster dynamics and limited thruster power. The reference model decomposition (RMD) technique is used to compensate for the thruster dynamics. A reference model adjustment (RMA) technique modifying the reference model acceleration is used to avoid thruster saturation. The design methods are simulated for the yawing motion of an underwater vehicle. ROV, model reference adaptive control,

oai:mic.1992.4.1 2010-03-20

eng Journal article 1992-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1992-4-1.asp Fulltext http://www.mic-journal.no/PDF/1992/MIC-1992-4-1.pdf Adjustment of PID control parameters Di Ruscio, David Methods are presented for the adjustment of PID control parameters, so that the loop transfer function, the sensitivity transfer function or the complementary sensitivity transfer function is tuned to a prescribed amplitude and phase. PID control parameters,

oai:mic.1992.4.2 2010-03-20

eng Journal article 1992-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1992-4-2.asp Fulltext http://www.mic-journal.no/PDF/1992/MIC-1992-4-2.pdf Control of a resonant d.c.-link converter for a.c. motor drives Petterteig, Astrid This paper presents the control of the resonant d.c.-link converter for a.c. motor drives. This is a low loss converter with higher efficiency than a conventional PWM converter, but it requires complex control. It needs a special control of the resonant d.c.-link voltage in addition to the discrete control of the a.c. side currents. Simulations show how the control of the a.c. currents, the modulation principle, influences the overall performance of the converter. Converter, modulation, switching,

oai:mic.1992.4.3 2010-03-20

eng Journal article 1992-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1992-4-3.asp Fulltext http://www.mic-journal.no/PDF/1992/MIC-1992-4-3.pdf Multidiscipline simulation of elastic manipulators Rølvåg, T. Hildre, Hans P. Sivertsen, O.I. Waløen, Å.O. This paper contributes to multidiscipline simulation of elastic robot manipulators in FEDEM. All developments presented in this paper are based on the formulations in FEDEM, a simulation system developed by the authors which combines finite element, mechanism and control analysis. In order to establish this general simulation system as an efficient multidiscipline robot design tool a robot control system including a high level robot programming language, interpolation algorithms, path generation algorithms, forward and inverse kinematics, control systems, gear and transmission models are implemented. These new features provide a high level of integration between traditionally separate design disciplines from the very beginning of the design and optimization process. Several simulations have shown that high fidelity mathematical models can be derived and used as a basis for dynamic analysis and controller design in FEDEM. Finite Element Method, kinematics, dynamics, control,

oai:mic.1993.1.1 2010-03-20

eng Journal article 1993-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1993-1-1.asp Fulltext http://www.mic-journal.no/PDF/1993/MIC-1993-1-1.pdf Structured modeling of fish physiology Olsen, Odd A. Balchen, Jens G. The use of models in simulation and state estimation has proved useful in diverse applications, especially in industrial process control. The project presented here looked into the modeling of fish physiology for applications in fish physiology research and aquaculture. The models deal with gastric evacuation, metabolism, kidneys, gills, the cardiovascular system, and feeding behaviour and are based on data from the literature. Model responses are mostly in accord with real responses in principle, but, as with most models of complex biological systems, the numerical accuracy is low in several cases. However, these structured models enable researchers to test hypotheses by altering the submodels and parameters. Metabolism, respiration, feeding behaviour, gills, kidneys, gastric evacutation, fish physiology,

oai:mic.1993.1.2 2010-03-20

eng Journal article 1993-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1993-1-2.asp Fulltext http://www.mic-journal.no/PDF/1993/MIC-1993-1-2.pdf Early fault detection and on-line diagnosis in real-time environments Bye, Andreas Ness, Eyvind This paper describes an approach to fault detection and diagnosis involving the simultaneous employment of quantitative and qualitative reasoning techniques. We show that early identification of process anomalies by means of a separate fault detection module paves the way for a fast and accuratc follow-up diagnosis. The diagnosis task is dramatically simplified because the diagnostic inferences can be performed at the soonest possible time: when the detection module first spots deviations between its calculated reference points and the corresponding measurements from the process. Operator support systems, fault detection, fault diagnosis, quantitation modeling,

oai:mic.1993.1.3 2010-03-20

eng Journal article 1993-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1993-1-3.asp Fulltext http://www.mic-journal.no/PDF/1993/MIC-1993-1-3.pdf On the Use of Constitutive Internal Variable Equations for Thermal Stress Predictions in Aluminium Casting Mo, Asbjørn Holm, Erik J. The report discusses the use of constitutive equations with internal variables in mathematical calculations of the thermally induced strains and stresses that arise during casting of aluminium. Application of the so-called MATMOD (MATerials MODel) constitutive relations for the viscoplastic deformation of the material is first discussed in relation to the specific characteristics of the casting process. Some numerical time integrations of the one-dimensional version of the MATMOD equations that are relevant for aluminium casting are then presented. The evolution of temperature and total strain are here chosen to be close to values experienced in the direct chill (D.C.) casting process, and values for thermally induced strains and stresses are calculated. The results are compared with predictions based on the traditional approach, in which a set of representative stress-strain curves at different constant temperatures and strain rates constitute the complete description of the viscoplastic deformation. Internal variables, constitutive equations, thermal stresses,

oai:mic.1993.2.1 2010-03-20

eng Journal article 1993-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1993-2-1.asp Fulltext http://www.mic-journal.no/PDF/1993/MIC-1993-2-1.pdf Dynamics and control of unstable distillation columns Jacobsen, Elling W. Skogestad, Sigurd The fact that ideal two-product distillation columns may have multiple steady states and unstable operating points has only recently been recognized. This paper discusses the dynamics and control implications. It is shown that columns operating with reflux and boilup as independent variables become unstable if the internal flows are sufficiently large. An open-loop unstable operating point may be stabilized by use of one-point control, i.e., feedback control of a column composition or temperature. If the control is not sufficiently tight, the column may go into a stable limit cycle. Finally, it is shown that with distillate flow and boilup as independent variables the operating points may become unstable if the level control is not sufficiently tight. The column may also in this case go into a stable limit cycle. Distillation, multiple steady states, instability,

oai:mic.1993.2.2 2010-03-20

eng Journal article 1993-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1993-2-2.asp Fulltext http://www.mic-journal.no/PDF/1993/MIC-1993-2-2.pdf Catalytic cracking models developed for predictive control purposes Ljungqvist, Dag Strand, Stig Balchen, Jens G. The paper deals with state-space modeling issues in the context of model-predictive control, with application to catalytic cracking. Emphasis is placed on model establishment, verification and online adjustment. Both the Fluid Catalytic Cracking (FCC) and the Residual Catalytic Cracking (RCC) units are discussed. Catalytic cracking units involve complex interactive processes which are difficult to operate and control in an economically optimal way. The strong nonlinearities of the FCC process mean that the control calculation should be based on a nonlinear model with the relevant constraints included. However, the model can be simple compared to the complexity of the catalytic cracking plant. Model validity is ensured by a robust online model adjustment strategy. Model-predictive control schemes based on linear convolution models have been successfully applied to the supervisory dynamic control of catalytic cracking units, and the control can be further improved by the SSPC scheme. State-space methods, catalytic cracking, predictive control, modeling,

oai:mic.1993.2.3 2010-03-20

eng Journal article 1993-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1993-2-3.asp Fulltext http://www.mic-journal.no/PDF/1993/MIC-1993-2-3.pdf ISACS, an integrated surveillance and control system Kvalem, Jon Grini, Rolf-Einar Haugset, Kjell In this paper we report about application requirements and design principles used in the development of an integrated surveillance and control system, intended to be used by the operator of a nuclear power plant. The system, for its own nature, is an example of a class of applications normally referred to as critical applications, and involve the use of both expert system and database technologies in a real-time process control environment. System integration, control room systems, expert systems,

oai:mic.1993.2.4 2010-03-20

eng Journal article 1993-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1993-2-4.asp Fulltext http://www.mic-journal.no/PDF/1993/MIC-1993-2-4.pdf Automatic programming of grinding robot Thomessen, Trygve Elle, Ole J. Lund Larsen, Jon Andersen, Torgrim Pedersen, Jahn E. Lien, Terje K. A new programming method is developed for grinding robots. Instead of using the conventional jog-and-teach method, the workpiecc geometry is automatically scanned by a contour tracking system. During tracking of the workpiece contour, the robot position is continuously logged. Finally a robot program is automatically generated. Robotic grinding, force control, speed control, automatic contour tracking,

oai:mic.1993.2.5 2010-03-20

eng Journal article 1993-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1993-2-5.asp Fulltext http://www.mic-journal.no/PDF/1993/MIC-1993-2-5.pdf Resolving redundancy through a weighted damped least-squares solution Sagli, Jan R. Spangelo, Inge Egeland, Olav Singularity robust redundancy resolution with task priority can be implemented using the extended Jacobian technique with weighted damped least-squares. The resulting scheme is simple to implement and involves less computation than the task priority scheme. The minimum singular value of the Jacobian can be estimated reliably and accurately with little computation, and this estimate was used to calculate an appropriate damping factor. A constant damping factor was also used with good results. The scheme was successfully implemented in a simulation study with a seven-joint manipulator with a kinematic design derived from the PUMA geometry. Robotics, redundant degrees of freedom, singularities,

oai:mic.1993.3.1 2010-03-20

eng Journal article 1993-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1993-3-1.asp Fulltext http://www.mic-journal.no/PDF/1993/MIC-1993-3-1.pdf A Comparison of Strategies for the Control of a Polypropene Reactor Lie, Bernt Balchen, Jens G. Several controller structures for a polypropene reactor system are evaluated, and it is shown that the present controller structure with retuned controller parameters yields very good performance with regards to set point tracking, and suppression of disturbances and model uncertainty. Multivariable LQG control with integral action shows even better results, and would have given excellent performance without some observed limitation in the estimator. Process control, control structures,

oai:mic.1993.3.2 2010-03-20

eng Journal article 1993-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1993-3-2.asp Fulltext http://www.mic-journal.no/PDF/1993/MIC-1993-3-2.pdf Navigation by images Hagen, Espen Heyerdahl, Eilert A new navigation method based on measurements of image tokens and Kalman filtering is presented. An image token is the central projection of a landmark, a point on the terrain surface. This surface being described by an elevation map, a Kalman filter processes the measurements to update estimates of camera position and orientation, and landmarks. The method has been implemented for off-line simulations of aeroplane navigation. Preliminary tests indicate a performance at least comparable to that of satellite navigation systems. The implemented algorithm also seems to have high tolerance against noise and modeling errors. Autonomous navigation, computer vision, optical flow,

oai:mic.1993.3.3 2010-03-20

eng Journal article 1993-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1993-3-3.asp Fulltext http://www.mic-journal.no/PDF/1993/MIC-1993-3-3.pdf Finite Element Modelling of the Hydrodynamic Environment of a Small ROV Guang, Ren Balchen, Jens G. This paper addresses a practical problem, namely, modeling the hydrodynamic environment of a small ROV. This has become the problem of solving time-dependent incompressible Navier-Stokes equations with moving boundaries and a new method is developed to solve it. Navier-Stokes equations expressed in a moving-body-fixed coordinate frame with moving boundaries are derived and solved by a proposed finite element method which is a modified velocity correction procedure (Ren and Utnes 1993). The present method is implemented in the C language on a SUN/Sparc Station. The algorithm and program are demonstrated by solving a classic driven cavity flow problem and a simplified model of the hydrodynamic environment of a small ROV, which is a moving boundary problem. The results from the driven cavity flow problem are compared to previous work. A definition is also given of the moving boundary problem (MBP) related to the solution of Navier-Stokes equations. Moving boundary, finite element, hydrodynamic model,

oai:mic.1993.3.4 2010-03-20

eng Journal article 1993-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1993-3-4.asp Fulltext http://www.mic-journal.no/PDF/1993/MIC-1993-3-4.pdf Frequency domain synthesis of trajectory learning controllers for robot manipulators Kavli, Tom Trajectory learning control is a method for generating near to optimal feedforward control for systems that are controlled along a reference trajectory in repeated cycles. Iterative refinements of a stored feedforward control sequence corresponding to one cycle of the control trajectory is computed based upon the recorded trajectory error from the previous cycle. Several learning operators have been proposed in earlier work, and convergence proofs are developed for certain classes of systems, but no satisfactory method for design and analysis of learning operators under the presence of uncertainties in the system model have been presented. This article presents frequency domain methods for analysing the convergence properties and performance of the learning controller when the amplitude and phase of the system transfer function is assumed to be within specified windows. Experimental results with an industrial robot manipulator confirm the theoretical results.

oai:mic.1993.3.5 2010-03-20

eng Journal article 1993-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1993-3-5.asp Fulltext http://www.mic-journal.no/PDF/1993/MIC-1993-3-5.pdf A Modified LQG Algorithm (MLQG) for Robust Control of Nonlinear Multivariable Systems Balchen, Jens G. The original LQG algorithm is often characterized for its lack of robustness. This is because in the design of the estimator (Kalman filter) the process disturbance is assumed to be white noise. If the estimator is to give good estimates, the Kalman gain is increased which means that the estimator fails to become robust. A solution to this problem is to replace the proportional Kalman gain matrix by a dynamic PI algorithm and the proportional LQ feedback gain matrix by a PI algorithm. A tuning method is developed which facilitates the tuning of a modified LQG control system (MLQG) by only two tuning parameters. Multivariable control, robustness,

oai:mic.1993.4.1 2010-03-20

eng Journal article 1993-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1993-4-1.asp Fulltext http://www.mic-journal.no/PDF/1993/MIC-1993-4-1.pdf Direct adaptive generalized predictive control Wang, Wei Henriksen, Rolf This paper is concerned with the direct approach of adaptive generalized predictive control. An implicit model with control law parameters is developed. A direct adaptive generalized predictive control algorithm and an improved variant are suggested. Global convergence of the algorithms is analysed under some assumptions. Predictive control, adaptive control,

oai:mic.1993.4.2 2010-03-20

eng Journal article 1993-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1993-4-2.asp Fulltext http://www.mic-journal.no/PDF/1993/MIC-1993-4-2.pdf ALSPEN: a mathematical model for thermal stresses in direct chill casting of aluminium billets Fjær, Hallvard G. Mo, Asbjørn This paper presents the mathematical model ALSPEN, in which the thermally induced strains and stresses which develop during direct chill (DC) semicontinuous casting of aluminium billets are calculated by a finite-element method. The metal is assumed to be an isotropic elastic-viscoplastic material with strongly temperature-dependent properties. In the material description, the viscoplastic strain is treated in a 'unified' manner, in which low-temperature (approximately) time-independent plasticity and creep at high temperatures occur as special cases. Furthermore, in the numerical time stepping procedure, all of these plastic material properties which are present simultaneously in the solution domain as a result of the large temperature differences, are treated in a similar way. To demonstrate some of the capabilities of ALSPEN, we have modeled the casting of an AlMgSi alloy, AA6063. The material properties of this alloy have been studied in parallel with the development of the mathematical model. DC casting, aluminium,

oai:mic.1993.4.3 2010-03-20

eng Journal article 1993-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1993-4-3.asp Fulltext http://www.mic-journal.no/PDF/1993/MIC-1993-4-3.pdf Design of the Property Transformation in Elementary Nonlinear Decoupling of Multivariable Processes Balchen, Jens G. In elementary nonlinear decoupling theory a property space (z) is defined as a transformation of the state space (x). Elementary nonlinear decoupling has the purpose of generating the control vector u which drives the system in such a way that the property vector has a desired rate of change. A method is described in this paper for the design of this property transformation which makes the nonlinear decoupling realizable and at the same time makes the system satisfy certain dynamic specifications. Nonlinear control, nonlinear decoupling, multivariable process,

oai:mic.1993.4.4 2010-03-20

eng Journal article 1993-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1993-4-4.asp Fulltext http://www.mic-journal.no/PDF/1993/MIC-1993-4-4.pdf Adaptive feedback linearization applied to steering of ships Fossen, Thor I. Paulsen, Marit J. This paper describes the application of feedback linearization to automatic steering of ships. The flexibility of the design procedure allows the autopilot to be optimized for both course-keeping and course-changing manoeuvres. Direct adaptive versions of both the course-keeping and turning controller are derived. The advantages of the adaptive controllers are improved performance and reduced fuel consumption. The application of nonlinear control theory also allows the designer in a systematic manner to compensate for nonlinearities in the control design. Ship autopilot, ship steering, nonlinear control,

oai:mic.1994.1.1 2010-03-20

eng Journal article 1994-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1994-1-1.asp Fulltext http://www.mic-journal.no/PDF/1994/MIC-1994-1-1.pdf Sophus Lie Baas, Nils A. (No abstract) Account of work,

oai:mic.1994.1.2 2010-03-20

eng Journal article 1994-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1994-1-2.asp Fulltext http://www.mic-journal.no/PDF/1994/MIC-1994-1-2.pdf A new recontruction algorithm for use with capacitance-based tomography Isaksen, Ø. Nordtvedt, J.E. A new reconstruction algorithm for use with capacitance-based process tomography is proposed. A numerical simulator, capable of calculating the capacitances for a particular sensor configuration and flow regime is used together with a parameter representation of the dielectric distribution and an optimization algorithm. The algorithm calculates these parameters and hence the dielectric distribution, by minimizing a function defined as a weighted sum of square differences between the measured and estimated capacitances. The method is tested by using both synthetic and experimental data, and the results are compared with results from the commonly used Linear Back Projection (LBP) algorithm. The method is capable of obtaining the correct parameter values for all the flow regimes tested, and does provide a better estimate than the LBP method. The method proves to be very promising, and is a step towards quantitative capacitance tomography. Process measurements, multiphase flow,

oai:mic.1994.1.3 2010-03-20

eng Journal article 1994-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1994-1-3.asp Fulltext http://www.mic-journal.no/PDF/1994/MIC-1994-1-3.pdf A direct adaptive generalized predictive controllers and some of its global convergence properties Wang, Wei Henriksen, Rolf This paper is concerned with the direct approach of adaptive generalized predictive control. Optimality of generalized predictive control is analyzed and an implicit model with control law parameters is developed. A direct adaptive generalized predictive control algorithm is suggested and some sufficient conditions for its global convergence are also derived. Predictive control, adaptive control,

oai:mic.1994.1.4 2010-03-20

eng Journal article 1994-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1994-1-4.asp Fulltext http://www.mic-journal.no/PDF/1994/MIC-1994-1-4.pdf Modeling and simulation of the mass flow and reaction kinetics in a continuous Kamyr steam/liquor phase digester Michelsen, Finn Are Foss, Bjarne A. The motion of the mass in a continuous digester can be described by the Navier-Stokes equations together with mass balances for the chip plug and the free liquor. The component balances for the wood and liquor materials fulfil the mass balances. These equations are solved to help understanding the dynamics connected to motion and chemical reactions taking place in the digester. Simulated profiles are shown in this paper. First principles modeling, distributed process, chemical pulping continuous process, flow dynamics,

oai:mic.1994.1.5 2010-03-20

eng Journal article 1994-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1994-1-5.asp Fulltext http://www.mic-journal.no/PDF/1994/MIC-1994-1-5.pdf A solution to the problem of constructing a state space model from time series Ruscio, David Di Henriksen, Rolf Balchen, Jens G. The problem of constructing minimal realizations from arbitrary input-output time series which are only covariance stationary (not necessarily stationary) is considered. An algorithm which solves this problem for a fairly nonrestrictive class of exogenous (input) signals is presented. The algorithm is based upon modeling nonzero exogenous signals by linear models and including these in the total system model. Combined determinstic-stochastic systems, identification, minimal realization, state-space modeling,

oai:mic.1994.2.1 2010-03-20

eng Journal article 1994-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1994-2-1.asp Fulltext http://www.mic-journal.no/PDF/1994/MIC-1994-2-1.pdf Ride control of surface effect ships using distributed control Sørensen, Asgeir J. Egeland, Olav A ride control system for active damping of heave and pitch accelerations of Surface Effect Ships (SES) is presented. It is demonstrated that distributed effects that are due to a spatially varying pressure in the air cushion result in significant vertical vibrations in low and moderate sea states. In order to achieve a high quality human comfort and crew workability it is necessary to reduce these vibrations using a control system which accounts for distributed effects due to spatial pressure variations in the air cushion. A mathematical model of the process is presented, and collocated sensor and actuator pairs are used. The process stability is ensured using a controller with appropriate passivity properties. Sensor and actuator location is also discussed. The performance of the ride control system is shown by power spectra of the vertical accelerations obtained from full scale experiments with a 35 m SES. SES, acoustic, ride control, passivity,

oai:mic.1994.2.2 2010-03-20

eng Journal article 1994-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1994-2-2.asp Fulltext http://www.mic-journal.no/PDF/1994/MIC-1994-2-2.pdf Cascaded adaptive control of ocean vehicles with significant actuator dynamics Fossen, Thor I. Fjellstad, Ola-Erik This paper presents a cascade adaptive control scheme for marine vehicles where the non-linear equations of motion include a model of the actuator dynamics. The adaptive controller does not require the parameters of the vehicle dynamics and the actuator time constants to be known a priori. Both the velocity and position tracking errors are shown to converge to zero by applying Barbalat's lemma. Global asymptotic stability is proven for the velocity scheme while the position/attitude controller is only proven to be convergent. Furthermore, all parameter estimates are shown to be bounded. Computer simulations of an ROV speed control system and an autopilot for automatic ship steering are used to illustrate the design methodology. Adaptive control, actuator dynamics, ship steering,

oai:mic.1994.2.3 2010-03-20

eng Journal article 1994-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1994-2-3.asp Fulltext http://www.mic-journal.no/PDF/1994/MIC-1994-2-3.pdf Improved independent design of robust decentralized controllers Hovd, Morten Skogestad, Sigurd The procedure for independent design of robust decentralized controllers proposed by Skogestad and Morari is improved by requiring that each individual controller is of the internal model control (IMC) type. It is shown how to find bounds on the magnitude of the IMC filter time constants such that robust stability or performance is guaranteed. In contrast, Skogestad and Morari found bounds on the sensitivity functions and complementary sensitivity functions for the individual loops, and therefore allowed a much larger class of designs, resulting in more conservative conditions. A property called robust decentralized detunability (RDD) is introduced. If a system has this property, any subset of the loops can be detuned independently and to an arbitrary degree without endangering robust stability. A simple test for RDD is developed for systems controlled by decentralized IMC controllers. Decentralized control, internal model control,

oai:mic.1994.2.4 2010-03-20

eng Journal article 1994-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1994-2-4.asp Fulltext http://www.mic-journal.no/PDF/1994/MIC-1994-2-4.pdf Recursive prediction error methods for online estimation in nonlinear state-space models Ljungquist, Dag Balchen, Jens G. Several recursive algorithms for online, combined state and parameter estimation in nonlinear state-space models are discussed in this paper. Well-known algorithms such as the extended Kalman filter and alternative formulations of the recursive prediction error method are included, as well as a new method based on a line-search strategy. A comparison of the algorithms illustrates that they are very similar although the differences can be important for the online tracking capabilities and robustness. Simulation experiments on a simple nonlinear process show that the performance under certain conditions can be improved by including a line-search strategy. Recursive estimation, line-search methods, recursive prediction error methods,

oai:mic.1994.3.1 2010-03-20

eng Journal article 1994-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1994-3-1.asp Fulltext http://www.mic-journal.no/PDF/1994/MIC-1994-3-1.pdf The future of control Åström, Karl J. This paper gives a personal view of the emergence, development and future of automatic control. The assessment is that automatic control has been very successful, but that we are now at a crossroads where we have to decide if we want to take an holistic view with full systems responsibility or if we want the field to fracture into a collection of subspecialities. Automatic control, history, theory,

oai:mic.1994.3.2 2010-03-20

eng Journal article 1994-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1994-3-2.asp Fulltext http://www.mic-journal.no/PDF/1994/MIC-1994-3-2.pdf Every good regulator of a system must be a model of that system Eykhoff, Pieter A model for the process under control - do or don't we really need it? Some elementary philosophical considerations confirming such a need, are well supported by examples of various 'optimal' control schemes. How does this affirmation influence the requirements to identification and the implemcntation of control using such a model? Modeling, identification,

oai:mic.1994.3.3 2010-03-20

eng Journal article 1994-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1994-3-3.asp Fulltext http://www.mic-journal.no/PDF/1994/MIC-1994-3-3.pdf Randomness reexamined Kalman, Rudolf E. "Roughly speaking, what we know is science and what we don't know is philosophy' - Bertrand Russel, ca. 1968.

oai:mic.1994.3.4 2010-03-20

eng Journal article 1994-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1994-3-4.asp Fulltext http://www.mic-journal.no/PDF/1994/MIC-1994-3-4.pdf System Identification in a MIC perspective Ljung, Lennart The paper describes some sibjective aspects on some current research topics in system identification. A 'classical' standpoint is taken regarding complexity models. The need for specific tools for 'semi-physical-modeling' is also pointed out, and a discussion on different disturbance models is also included. Identification, modeling, model errors,

oai:mic.1994.3.5 2010-03-20

eng Journal article 1994-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1994-3-5.asp Fulltext http://www.mic-journal.no/PDF/1994/MIC-1994-3-5.pdf The Past and the Next Fifteen Years Morari, Manfred The scope of MIC defined by the title Modeling, Identification and Control is broad and it is impossible to do justice to all these areas in a discussion which is limited to a few pages. Therefore, in the following paragraphs I will concentrate on control and leave the treatment of the other topics to the other contributors. Model predictive control, optimal control,

oai:mic.1994.3.6 2010-03-20

eng Journal article 1994-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1994-3-6.asp Fulltext http://www.mic-journal.no/PDF/1994/MIC-1994-3-6.pdf Modeling sustainable development Jacques C.J., Nihoul Some of the difficulties of extending economic and ecosystem models to allow for long term forecasting applications to the problem of sustainable development are discussed. Sustainable development,

oai:mic.1994.3.7 2010-03-20

eng Journal article 1994-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1994-3-7.asp Fulltext http://www.mic-journal.no/PDF/1994/MIC-1994-3-7.pdf Trends in process systems engineering Perkins, John (No abstract) Process industries, design, operation, control,

oai:mic.1994.3.8 2010-03-20

eng Journal article 1994-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1994-3-8.asp Fulltext http://www.mic-journal.no/PDF/1994/MIC-1994-3-8.pdf A perspective on advanced strategies for process control Seborg, Dale E. This paper provides a personal perspective on the current status of advanced process control strategies. First, these strategies are classified according to the degree which they have been used in industry. Then the most prominent methods are discussed critically with emphasis placed on key design issues and unresolved research problems. Process control, advanced control strategies,

oai:mic.1994.3.9 2010-03-20

eng Journal article 1994-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1994-3-9.asp Fulltext http://www.mic-journal.no/PDF/1994/MIC-1994-3-9.pdf The role of fuzzy logic in modeling, identification and control Zadeh, Lotfi A. In the nearly four decades which have passed since the launching of the Sputnik, great progress has been achieved in our understanding of how to model, identify and control complex systems. However, to be able to design systems having high MIQ (Machine Intelligence Quotient), a profound change in the orientation of control theory may be required. More specifically, what may be needed is the employment of soft computing - rather than hard computing - in systems analysis and design. Soft computing - unlike hard computing - is tolerant of imprecision, uncertainty and partial truth. Fuzzy logic, fuzzy contol,

oai:mic.1994.4.1 2010-03-20

eng Journal article 1994-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1994-4-1.asp Fulltext http://www.mic-journal.no/PDF/1994/MIC-1994-4-1.pdf Chaotic time series. Part I. Estimation of some invariant properties in state-space Kugiumtzis, Dimitris Lillekjendlie, Bjørn Christophersen, Nils Certain deterministic non-linear systems may show chaotic behaviour. Time series derived from such systems seem stochastic when analyzed with linear techniques. However, uncovering the deterministic structure is important because it allows for construction of more realistic and better models and thus improved predictive capabilities. This paper describes key features of chaotic systems including strange attractors and Lyapunov exponents. The emphasis is on state space reconstruction techniques that are used to estimate these properties, given scalar observations. Data generated from equations known to display chaotic behaviour are used for illustration. A compilation of applications to real data from widely different fields is given. If chaos is found to be present, one may proceed to build non-linear models, which is the topic of the second paper in this series. Time series, non-linear systems, chaos, noise, reconstruction, dimension of attractor,

oai:mic.1994.4.2 2010-03-20

eng Journal article 1994-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1994-4-2.asp Fulltext http://www.mic-journal.no/PDF/1994/MIC-1994-4-2.pdf Chaotic time series. Part II. System Identification and Prediction Lillekjendlie, Bjørn Kugiumtzis, Dimitris Christophersen, Nils This paper is the second in a series of two, and describes the current state of the art in modeling and prediction of chaotic time series. Sample data from deterministic non-linear systems may look stochastic when analysed with linear methods. However, the deterministic structure may be uncovered and non-linear models constructed that allow improved prediction. We give the background for such methods from a geometrical point of view, and briefly describe the following types of methods: global polynomials, local polynomials, multilayer perceptrons and semi-local methods including radial basis functions. Some illustrative examples from known chaotic systems are presented, emphasising the increase in prediction error with time. We compare some of the algorithms with respect to prediction accuracy and storage requirements, and list applications of these methods to real data from widely different areas. Nonlinear systems, chaos, prediction, time series,

oai:mic.1994.4.3 2010-03-20

eng Journal article 1994-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1994-4-3.asp Fulltext http://www.mic-journal.no/PDF/1994/MIC-1994-4-3.pdf Optimal and adaptive control of underwater vehicles Sagatun, Svein I. Johansson, Rolf This article contains a continuous-time optimal and adaptive control scheme for underwater vehicles moving in six degrees of freedom. The control scheme is an extension of the algorithm ofJohansson (1990) and a modification of the algorithm found in Sagatun (1992). The algorithm is optimal in the sense that it minimizes the state errors and the forces which contribute to the vehicle's kinetic energy that is spent to correct these errors. The performance measure does also contain a term which penalizes the quadratic tracking errors proportional to the rate of energy which dissipates from the system due to damping. Optimal control, adaptive control,

oai:mic.1994.4.4 2010-03-20

eng Journal article 1994-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1994-4-4.asp Fulltext http://www.mic-journal.no/PDF/1994/MIC-1994-4-4.pdf Generalized predictive control of nonlinear systems of the Hammerstein form Wang, Wei Henriksen, Rolf A nonlinear generalized predictive control algorithm based upon a Hammerstein model is presented. Stability of the closed-loop system is analyzed with a control horizon equal to one. An adaptive nonlinear generalized predictive control algorithm with a linear estimator is then proposed. Finally, some results from simulation experiments are presented in order to show the algorithm's ability. Nonlinear systems, Hammerstein models, predictive control, adaptive control,

oai:mic.1995.1.1 2010-03-20

eng Journal article 1995-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1995-1-1.asp Fulltext http://www.mic-journal.no/PDF/1995/MIC-1995-1-1.pdf Modeling and simulation of an anode carbon baking furnace Gundersen, Ø. Balchen, Jens G. The anode temperature profile in a Hydro Aluminium baking furnace is obtained by solving the three dimensional heat equation. The main heat transfer and chemical processes are taken into account. Due to symmetry, one half of a pit is modeled. Along the gas path, submodels are derived for the under-pit area, pit area and under-lid area. For the gas flow, a stationary model is derived, whereas the heat equations are dynamically solved. The numerical model is derived from the control volume formulation. First principles modeling, distributed thermal batch process, heat transfer, combustion,

oai:mic.1995.1.2 2010-03-20

eng Journal article 1995-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1995-1-2.asp Fulltext http://www.mic-journal.no/PDF/1995/MIC-1995-1-2.pdf Robust control and analysis of a wind-diesel hybrid power plant Uhlen, K. Foss, Bjarne A. Gjøsæter, O.B. The aim of this paper is twofold. First to present multivariable frequency domain techniques as a tool for controller design and dynamic analysis of an autonomous wind-diesel power system. Secondly to study how robust model based controllers can be designed for such systems. Autonomous power systems, wind-diesel systems, robust control, multivariable frequency analysis, decoupling,

oai:mic.1995.1.3 2010-03-20

eng Journal article 1995-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1995-1-3.asp Fulltext http://www.mic-journal.no/PDF/1995/MIC-1995-1-3.pdf Elementary Decoupling control of composition in binary distillation columns Balchen, Jens G. Sandrib, Bjarne Elemenatary nonlinear decoupling (END) is a model based control algorithm which intends to decouple and linearize a nonlinear multivariable process in order to achieve better control than can be obtained by conventional decentralized linear feedback control. The application of END to the composition control of a theoretical binary distillation column illustrates that the achievable quality is very high. Nonlinear control, decoupling, distillation,

oai:mic.1995.2.1 2010-03-20

eng Journal article 1995-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1995-2-1.asp Fulltext http://www.mic-journal.no/PDF/1995/MIC-1995-2-1.pdf Approaches for Stereo Matching Ozanian, Takouhi This review focuses on the last decade's development of the computational stereopsis for recovering three-dimensional information. The main components of the stereo analysis are exposed: image acquisition and camera modeling, feature selection, feature matching and disparity interpretation. A brief survey is given of the well known feature selection approaches and the estimation parameters for this selection are mentioned. The difficulties in identifying correspondent locations in the two images are explained. Methods as to how effectively to constrain the search for correct solution of the correspondence problem are discussed, as are strategies for the whole matching process. Reasons for the occurrence of matching errors are considered. Some recently proposed approaches, employing new ideas in the modeling of stereo matching in terms of energy minimization, are described. Acknowledging the importance of computation time for real-time applications, special attention is paid to parallelism as a way to achieve the required level of performance. The development of trinocular stereo analysis as an alternative to the conventional binocular one, is described. Finally a classification based on the test images for verification of the stereo matching algorithms, is supplied. Computer vision, binocular stereo, feature selection, correspondence, constraints, matching, energy minimization, parallelism,

oai:mic.1995.2.2 2010-03-20

eng Journal article 1995-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1995-2-2.asp Fulltext http://www.mic-journal.no/PDF/1995/MIC-1995-2-2.pdf Input saturation in nonlinear multivariable processes resolved by nonlinear decoupling Balchen, Jens G. Sandrib, Bjarne A new method is presented for the resolution of the problem of input saturation in nonlinear multivariable process control by means of elementary nonlinear decoupling (END). Input saturation can have serious consequences particularly in multivariable control because it may lead to very undesirable system behaviour and quite often system instability. Many authors have searched for systematic techniques for designing multivariable control systems in which saturation may occur in any of the control variables (inputs, manipulated variables). No generally accepted method seems to have been presented so far which gives a solution in closed form. The method of elementary nonlinear decoupling (END) can be applied directly to the case of saturation control variables by deriving as many control strategies as there are combinations of saturating control variables. The method is demonstrated by the multivariable control of a simulated Fluidized Catalytic Cracker (FCC) with very convincing results. Multivariable control, saturation,

oai:mic.1995.2.3 2010-03-20

eng Journal article 1995-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1995-2-3.asp Fulltext http://www.mic-journal.no/PDF/1995/MIC-1995-2-3.pdf The control system of an autonomous underwater vehicle Jalving, Bjørn Størkersen, Nils This paper presents the flight control system of an Autonomous Underwater Vehicle (AUV) developed at the Norwegian Defence Research Establishment. A mathematical model of the vehicle is derived and discussed. The system is separated into lightly interacting subsystems and three autopilots are designed for steering, diving and speed control. The design of the separate controllers is based on PID techniques. Results from sea trials show robust performance and stability for the autopilot. Autonomous underwater vehicle, flight control system,

oai:mic.1995.3.1 2010-03-20

eng Journal article 1995-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1995-3-1.asp Fulltext http://www.mic-journal.no/PDF/1995/MIC-1995-3-1.pdf Temperature and flow distribution in planar SOFC stacks Østenstad, Monica Sira, Terje Simulation of a planar Solid Oxide Fuel Cell stack requires the solution of the mass balances of the chemical species, the energy balances, the charge balance and the channel flow equations in order to compute the species concentrations, the temperature distributions, the current density and the channel flows. The unit cell geometry can be taken into account by combining detailed modeling of a unit cell with a homogenized model of a whole stack. In this study the effect of the asymmetric temperature distribution on the channel flows in a conventional cross-flow design has been investigated. The bidirectional cross-flow design is introduced, for which we can show more directional temperature and flow distributions. SOFC, numerical model, design,

oai:mic.1995.3.2 2010-03-20

eng Journal article 1995-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1995-3-2.asp Fulltext http://www.mic-journal.no/PDF/1995/MIC-1995-3-2.pdf A method for the identification of state space models from input and output measurements Di Ruscio, David In this paper we present a simple and general algorithm for the combined deterministic stochastic realization problem directly from known input and output time series. The solution to the pure deterministic as well as the pure stochastic realization problem are special cases of the method presented. System identification, combined deterministic and stochastic systems, minimal realization, modeling, state-space methods,

oai:mic.1995.3.3 2010-03-20

eng Journal article 1995-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1995-3-3.asp Fulltext http://www.mic-journal.no/PDF/1995/MIC-1995-3-3.pdf Automatic programming of grinding robot restoration of contours Willersrud, Are Godtliebsen, Fred Thomessen, Trygve A new programming method has been developed for grinding robots. Instead of using the conventional jog-and-teach method, the workpiece contour is automatically tracked by the robot. During the tracking, the robot position is stored in the robot control system every 8th millisecond. After filtering and reducing this contour data, a robot program is automatically generated. Filtering, robot, grinding,

oai:mic.1995.3.4 2010-03-20

eng Journal article 1995-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1995-3-4.asp Fulltext http://www.mic-journal.no/PDF/1995/MIC-1995-3-4.pdf Analytical generation of the dynamical equations for mechanical manipulators Horn, Geir Linge, Svein A package to generate the symbolic dynamic equations describing the relation between forces and movements for serial mechanical linkages with rigid constituents is presented. The relative movement between the rigid parts is assumed to be either a rotation about an axis or a translation along an axis. Two algorithms are implemented, a Lagrange-Euler method and a Newton-Euler method. The former can be used to solve both the inverse and the forward dynamics problems, while the latter requires fewer arithmetical operations but only allows solution of the inverse dynamics problem. Two test examples are presented, the double pendulum and the modified Stanford manipulator. Wind power, terrain models,

oai:mic.1995.3.5 2010-03-20

eng Journal article 1995-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1995-3-5.asp Fulltext http://www.mic-journal.no/PDF/1995/MIC-1995-3-5.pdf Flow over complex terrain estimated by a general purpose Navier-Stokes solver Alm, L.K. Nygaard, T.A. A general purpose Navier - Stokes solver has been applied to atmospheric flow on microscale. For flat terrain the model produces the well known logarithmic profile in the surface layer and describes the effect of roughness change. At Askervein Hill, good agreement between model results and measurements is observed also behind the hilltop, where linearized models overpredict the wind speed. Wind power, terrain models,

oai:mic.1995.4.1 2010-03-20

eng Journal article 1995-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1995-4-1.asp Fulltext http://www.mic-journal.no/PDF/1995/MIC-1995-4-1.pdf Computational fluid dynamics simulation of bioreactors Hjertager, Bjørn H. Morud, K. Multi-dimensional models of flow processes in bioreactors are presented. Particular emphasis is given to models that use the two-fluid technique. The models use a two-equation turbuluence model and a Monod type kinetic reaction model. Predictions are given for both bubble column and mechanically stirred reactors. Bioprocess, modeling, multiphase,

oai:mic.1995.4.2 2010-03-20

eng Journal article 1995-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1995-4-2.asp Fulltext http://www.mic-journal.no/PDF/1995/MIC-1995-4-2.pdf Mathematical modeling of a rotary hearth coke calciner Meisingset, Hilde C. Balchen, Jens G. A mathematical model of a rotary hearth coke calciner is developed. The model is based on first principles including the most important dynamic phenomena. The model is a thermodynamic model involving heat and mass transfer and chemical reactions. Fundamental mass and energy balance equations for the coke phase, the gas phase and the lining are formulated. For the gas phase, a stationary model is used. The equations are solved numerically, and simulated temperature profiles are shown in this paper. First principles modeling, distributed process, coke calcination, combustion,

oai:mic.1995.4.3 2010-03-20

eng Journal article 1995-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1995-4-3.asp Fulltext http://www.mic-journal.no/PDF/1995/MIC-1995-4-3.pdf Semi-empirical modeling of non-linear dynamic systems through identification of operating regimes and local models Johansen, Tor A. Foss, Bjarne A. An off-line algorithm for semi-empirical modeling of nonlinear dynamic systems is presented. The model representation is based on the interpolation of a number of simple local models, where the validity of each local model is restricted to an operating regime, but where the local models yield a complete global model when interpolated. The input to the algorithm is a sequence of empirical data and a set of candidate local model structures. The algorithm searches for an optimal decomposition into operating regimes, and local model structures. The method is illustrated using simulated and real data. The transparency of the resulting model and the exibility with respect to incorporation of prior knowledge is discussed. Non-linear systems, system identification, fuzzy modeling,

oai:mic.1995.4.4 2010-03-20

eng Journal article 1995-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1995-4-4.asp Fulltext http://www.mic-journal.no/PDF/1995/MIC-1995-4-4.pdf Mechanical Analysis of high precision manipulator Elle, O.J. Johnsen, K. Lien, Terje K. It is of great importance that high precision manipulators are well designed from a mechanical point of view. A thorough analysis of all mechanical aspects concerning an accurate manipulator will make a good basis for further design. This paper presents a new approach to mechanical analysis of high-precision manipulators. A typical six axis anthropomorphic manipulator configuration is chosen as a model for the analysis. The paper is divided into two main parts; static deformation analysis and dynamic analysis. The static deformation analysis consists of three sub-parts; link deformation, joint deformation and total mechanical deformation. A simple fixed beam deformation model is used to simulate every link. Both specific gravity and a load attached at the end of the beam is considered. By varying material, outer dimensions and wall thickness it is possible to determine optimal values. Looking at the whole structure with an attacking force at the end, it is possible to select appropriate motor/transmission combinations. Each combination represents compliance and combined with the arm compliance the total deformation can be found. The result shows that deformation due to compliance in the joints represents 97 Manipulator, mechanism analysis, deflection, dynamics,

oai:mic.1996.1.1 2010-03-20

eng Journal article 1996-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1996-1-1.asp Fulltext http://www.mic-journal.no/PDF/1996/MIC-1996-1-1.pdf Advances in Inertial Measurement Technology for Marine Motion Control Håndlykken, Mathias This paper describes the function of an inertial "strap down" attitude sensor based on solid state Coriolis force rate gyros, accelerometers and magnetic sensor. Performance is analyzed taking into account the typical excitations in attitude and linear motion seen in marine applications. The use is for control of fast crafts, ROV and AUV heading, roll, pitch and heave control. The influence on performance given by utilization of external information from velocity log and more accurate heading devices is also analyzed. Typical performance of this low cost type of technology is shown. Attitude sensor, roll control, pitch control,

oai:mic.1996.1.2 2010-03-20

eng Journal article 1996-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1996-1-2.asp Fulltext http://www.mic-journal.no/PDF/1996/MIC-1996-1-2.pdf Motion Control of underwater vehicle-manipulator systems using feedback linearization Schjølberg, Ingrid Egeland, Olav In this paper control of underwater vehicle-manipulator systems using feedback linearization has been studied. Performance, robustness and energy consumption of the system depend on the choice of output variables, these output variables can be chosen in several ways. In this paper two alternatives have been analysed by simulations, decoupling of the manipulator end-effector velocities from the vehicle velocities and from the total system momentum. The performance is almost the same for the two choices of decoupling schemes while robustness and energy consumption of the system depend on the accuracy of the dynamic model. Underwater robotics,

oai:mic.1996.1.3 2010-03-20

eng Journal article 1996-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1996-1-3.asp Fulltext http://www.mic-journal.no/PDF/1996/MIC-1996-1-3.pdf Minesniper Smestad, B. The flight control system of a minehunting ROV-type weapon developed by SIMRAD is presented. The system is separated into lightly interacting subsystems, and autopilots are designed for steering, diving and speed control. The design of the separate controllers is based on PI, forward loop and sliding mode techniques. The diving control system, using the battery-packet as actuator, is specially examined. Results from sea testing show performance and stability for the autopilots. Minehunting ROV, autopilot-design,

oai:mic.1996.1.4 2010-03-20

eng Journal article 1996-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1996-1-4.asp Fulltext http://www.mic-journal.no/PDF/1996/MIC-1996-1-4.pdf Model based teleoperation of untethered underwater vehicles with manipulators Balchen, Jens G. Model based teleoperation of underwater vehicles and manipulators is a way to solve the problem introduced by the very long delay caused by the narrow band sonic communication link between the vehicle and the surface vessel. The MOBATEL project is described. Model based, teleoperation,

oai:mic.1996.1.5 2010-03-20

eng Journal article 1996-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1996-1-5.asp Fulltext http://www.mic-journal.no/PDF/1996/MIC-1996-1-5.pdf Robust adaptive control of underwater vehicles: A comparative study Fossen, Thor I. Fjellstad, Ola-Erik Robust adaptive control of underwater vehicles in 6 DOF is analysed in the context of measurement noise. The performance of the adaptive control laws of Sadegh and Harowitz (1990) and Slotine and Benedetto (1990) are compared. Both these schemes require that all states are measured, that is the velocities and positions in surge, sway, heave, roll, pitch and yaw. However, for underwater vehicles it is difficult to measure the linear velocities whereas angular velocity measurements can be obtained by using a 3 axes angular rate sensor. This problem is addressed by designing a nonlinear observer for linear velocity state estimation. The proposed observer requires that the position and the attitude are measured, e.g. by using a hydroacoustic positioning system for linear positions, two gyros for roll and pitch and a compass for yaw. In addition angular rate measurements will be assumed available from a 3-axes rate sensor or a state estimator. It is also assumed that the measurement rate is limited to 2 Hz for all the sensors. Simulation studies with a 3 DOF AUV model are used to demonstrate the convergence and robustness of the adaptive control laws and the velocity state observer. ROV, AUV, adaptive control, nonlinear velocity observer,

oai:mic.1996.1.6 2010-03-20

eng Journal article 1996-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1996-1-6.asp Fulltext http://www.mic-journal.no/PDF/1996/MIC-1996-1-6.pdf Ideas for underwater 3D sonar range sensing and environmental modeling Auran, Per G. Silven, Olli A 3D spatial grid for exploiting the range and direction information inherent in sonar range data is presented. Special attention is given to the realtime performance of this representation, i.e. it should be a feasible way of representing the 3D range data acquired by an operating AUV. 3D sonar range sensing,

oai:mic.1996.2.1 2010-03-20

eng Journal article 1996-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1996-2-1.asp Fulltext http://www.mic-journal.no/PDF/1996/MIC-1996-2-1.pdf Robust performance in dynamic positioning systems Johannessen, Erling Egeland, Olav Robust performance of dynamic positioning of surface vessels is considered. The structured singular value, mu, is used as a robustness measure. A tight uncertainty description of the wave disturbance model and performance weight matrices based on physical insight is presented. Two controllers are analysed: a decentralized PD controller with notch filters and an LGQ based controller. Performance of the control systems is shown to be sensitive with respect to changes in the dominating wave frequency, omega_0. Dynamic positioning, surface vessels, robust performance, structured singular value,

oai:mic.1996.2.2 2010-03-20

eng Journal article 1996-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1996-2-2.asp Fulltext http://www.mic-journal.no/PDF/1996/MIC-1996-2-2.pdf Wave disturbance filtering in dynamic positioning systems Schei, Tor S. Three different approaches to wave disturbance filtering in dynamic positioning systems are studied in this paper. It is shown that a conventional design based on notch filters leads to approximately the same achievable performance of the total control system as can be achieved with an observer based design. It is also shown that a proposed passivity based design leads to a conventional filter with PD-controller. However, there is a relation between the parameters in the filter and the PD-controller, which ensures the passivity properties of the control system. Marine systems, ship control, navigation, filtering,

oai:mic.1996.2.3 2010-03-20

eng Journal article 1996-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1996-2-3.asp Fulltext http://www.mic-journal.no/PDF/1996/MIC-1996-2-3.pdf An output feedback tracking controller for ships with nonlinear damping terms Paulsen, Marit Egeland, Olav A tracking controller with wave filter for ships with nonlinear manoeuvring characteristics is derived. Only measurement of the yaw angle is needed to assure global asymptotic stability of the yaw angle and yaw rate of the ship about the desired yaw angle and yaw rate. A case study finally shows that the influence from the wave disturbances on the rudder is attenuated in some frequency range. Nonlinear ship control, tracking,

oai:mic.1996.2.4 2010-03-20

eng Journal article 1996-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1996-2-4.asp Fulltext http://www.mic-journal.no/PDF/1996/MIC-1996-2-4.pdf A globally stable autopilot with wave filter using only yaw angle measurements Lauvdal, Trygve Fossen, Thor I. A stable minimum phase transfer function from rudder angle to yaw angle is used to design a globally stable adaptive ship autopilot. First-order wave disturbances in yaw are filtered by applying a notch filter. Integral action is introduced by using a reference model technique. Global stability is proven for the total system which include the yaw rate observer, the parameter update law, the feedback controller, the notch filter and the integral part of the controller. The simulation results showed that the performance is excellent, even with no a priori knowledge of the ship parameters. Global stability, adaptive ship autopilot, output feedback, notch filtering, integral action,

oai:mic.1996.2.5 2010-03-20

eng Journal article 1996-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1996-2-5.asp Fulltext http://www.mic-journal.no/PDF/1996/MIC-1996-2-5.pdf Passive output feedback and observer based autopilots: A comparative study Paulsen, Marit Egeland, Olav Two methods for course-keeping of a ship are studied where no measurements of the yaw rate are available. The two methods are a passive output feedback controller and a controller-observer structure. A comparison with special attention to stability and wave filtering properties, is provided. Finally, a case study of a ship autopilot is included. Comparative study, ship autopilots, passive controllers, observer based controllers,

oai:mic.1996.2.6 2010-03-20

eng Journal article 1996-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1996-2-6.asp Fulltext http://www.mic-journal.no/PDF/1996/MIC-1996-2-6.pdf Design of a dynamic positioning system using model-based control Sørensen, Asgeir J. Sagatun, Svein I. Fossen, Thor I. A dynamic positioning (DP) system includes different control functions for automatic positioning and guidance of marine vessels by means of thruster and propeller actions. This paper describes the control functions which provide station-keeping and tracking. The DP controller is designed using model-based control, where a new modified LQG feedback controller and a model reference feedforward controller are applied. A reference model calculates appropriate reference trajectories. Since it is not desirable nor even possible to counteract the wave-frequency movement caused by first-order wave loads, the control action of the propulsion system should be produced by the low frequency part of the vessel movement caused by current, wind and second-order mean and slowly varying wave loads. A Kalman filter based state estimator and a Luenberger observer are used to compute the low-frequency feedback and feedforward control signals. Full-scale experiments with a supply vessel demonstrate the performance of the proposed controller. Dynamic positioning, model-based control, hydrodynamics, sea trials,

oai:mic.1996.2.7 2010-03-20

eng Journal article 1996-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1996-2-7.asp Fulltext http://www.mic-journal.no/PDF/1996/MIC-1996-2-7.pdf Identification of Dynamically Positioned Ships Fossen, Thor I. Sagatun, Svein I. Sørensen, Asgeir J. Todays model-based dynamic positioning (DP) systems require that the ship and thruster dynamics are known with some accuracy in order to use linear quadratic optical control theory. However, it is difficult to identify the mathematical model of a dynamically posititmed (DP) ship since the ship is not persistently excited under DP. In addition the ship parameter estimation problem is nonlinear and multivariable with only position and thruster state measurements available for parameter estimation. The process and measurement noise must also be modeled in order to avoid parameter drift due to environmental disturbances and sensor failure. This article discusses an off-line parallel extended Kalman filter (EKF) algorithm utilizing two measurement series in parallel to estimate the parameters in the DP ship model. Full-scale experiments with a supply vessel are used to demonstrate the convergence and robustness of the proposed parameter estimator. Dynamic positioning, identification, full-scale sea trials, Kalman filtering, self-tuning control,

oai:mic.1996.3.1 2010-03-20

eng Journal article 1996-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1996-3-1.asp Fulltext http://www.mic-journal.no/PDF/1996/MIC-1996-3-1.pdf Controllability measures for disturbance rejection Skogestad, Sigurd Wolff, Erik A. Some plants have better "built-in" disturbance rejection capabilities than others, that is, their dynamic resilience (controllability) with respect to disturbance rejection is better. In the paper we consider controller independent disturbance measures for six classes of problems: Input-output controllability, control structure design, relative gain array,

oai:mic.1996.3.2 2010-03-20

eng Journal article 1996-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1996-3-2.asp Fulltext http://www.mic-journal.no/PDF/1996/MIC-1996-3-2.pdf Norwegian Residential Energy Demand: Coordinated use of a System Engineering and a Macroeconomic Model Johnsen, Tor A Unander, Fridtjof F. In Norway, the system engineering model MARKAL and the macroeconomic model MSG-EE are both used in studies of national CO2 controlling strategies. MARKAL is a linear programming model that calculates a composite set of technologies necessary to meet demand and environmental constraints at minimised total energy expenditure. MSG-EE is an applied general equilibrium model including the link between economic activity, energy demand and emissions to air. MSG-EE has a theory consistent description of the link between income, prices and energy demand, but the representation of technological improvements is simple. MARKAL has a sophisticated description of future energy technology options, but includes no feedback to the general economy. A project for studying the potential for a coordinated use of these two models was initiated and funded by the Norwegian Research Council (NFR). This paper gives a brief presentation of the two models. Results from independent model calculations show that MARKAL gives a signficant lower residential energy demand than MSG-EE does. This is explained by major differences in modelling approach. A first attempt of coordinating the residential energy demand in the models is reported. This attempt shows that implementing results from MARKAL, in MSG-EE for the residential sector alone gives little impact on the general economy. A further development of an iteration procedure between the models should include all energy using sectors. Energy, Economy, General equilibrium model,

oai:mic.1996.3.3 2010-03-20

eng Journal article 1996-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1996-3-3.asp Fulltext http://www.mic-journal.no/PDF/1996/MIC-1996-3-3.pdf Combined Deterministic and Stochastic System Identification and Realization: DSR - A Subspace Approach Based on Observations Di Ruscio, David A numerically stable and general algorithm for identification and realization of a complete dynamic linear state space model, including the system order, for combined deterministic and stochastic systems from time series is presented. A special property of this algorithm is that the innovations covariance matrix and the Markov parameters for the stochastic sub-system are determined directly from a projection of known data matrices, without e.g. recursions of non-linear matrix Riccatti equations. A realization of the Kalman filter gain matrix is determined from the estimated extended observability matrix and the Markov parameters. Monte Carlo simulations are used to analyze the statistical properties of the algorithm as well as comparing with existing algorithms. System identification, subspace methods, stochastic and deterministic systems, state-space methods,

oai:mic.1996.4.1 2010-03-20

eng Journal article 1996-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1996-4-1.asp Fulltext http://www.mic-journal.no/PDF/1996/MIC-1996-4-1.pdf Identification of Vibration Parameters in a Spacecraft using Nonparametric and Parametric Methods Skullestad, Åge This article describes identification of vibration frequencies in a spacecraft. A mathematical model of a simple spacecraft is built in MATLAG code, and after a theoretical overview, this spacecraft model is simulated, using a torque excitation, to generate time series measurements. These measurements are subsequently used in the identification experiments. Parametric methods, here represented by AR, ARX, ARMA and ARMAX, are the main concern, but nonparametric methods are also discussed. " Parameter identification, spectral estimation, linear systems,

oai:mic.1996.4.2 2010-03-20

eng Journal article 1996-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1996-4-2.asp Fulltext http://www.mic-journal.no/PDF/1996/MIC-1996-4-2.pdf Process Identification in On-line Optimizing Control, an Application to a Heat Pump Svensson, Morten C. The objective of this paper is to focus on on-line state and parameter estimation in connection with on-line model-based optimizing control of continuous processes. A nonlinear programming approach is used to estimate unmeasured state variables and parameters in systems modelled by nonlinear differential-algebraic equations. The nonlinear dynamic model is discretized by orthogonal collocation on finite elements, and the moving-horizon approach is used to reduce the dimension of the final optimization problem. System identification, dynamic optimization,

oai:mic.1996.4.3 2010-03-20

eng Journal article 1996-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1996-4-3.asp Fulltext http://www.mic-journal.no/PDF/1996/MIC-1996-4-3.pdf Model-based Optimizing Control of a Water-to-Water Heat Pump Unit Svensson, Morten C. This paper outlines the basic principles of on-line model-based steady-state optimizing control of continuous processes, and illustrates how this control approach can be used to optimize the operating conditions of heat pumps. Dynamic optimization, heat pumps,

oai:mic.1997.1.1 2010-03-20

eng Journal article 1997-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1997-1-1.asp Fulltext http://www.mic-journal.no/PDF/1997/MIC-1997-1-1.pdf Control, Operator Support and Safety System of PVC-reactors Ytreeide, Jens I. Aaker, Olav Kristoffersen, Vidar Moe, Geir Naustdal, Christian In modern petrochemical plants the corporate and societal demands to plant safety and minimum environmental effects are high. These demands rise high performance requirements to the technical systems, specially the process control and safety systems including an effective operator support system with fault detection capability. The systems must have high reliability also against erroneous operations which may cause shutdown situations or quality deviations. Parallel control, fault detection, extended Kalman filter,

oai:mic.1997.1.2 2010-03-20

eng Journal article 1997-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1997-1-2.asp Fulltext http://www.mic-journal.no/PDF/1997/MIC-1997-1-2.pdf Process Modelling of Chemical Reactors: Zero- versus Multi-dimensional Models Hjertager, Bjørn H. Trends in modelling of flow processes in the chemical reactors are presented. Particular emphasis is given to models that use the multi-dimensional multi-fluid techniques. Examples are given for both gas/liquid as well as gas/particle reators. Multiphase, multidimensional, gas/liquid, gas/particle, bioreactor,

oai:mic.1997.1.3 2010-03-20

eng Journal article 1997-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1997-1-3.asp Fulltext http://www.mic-journal.no/PDF/1997/MIC-1997-1-3.pdf Simulations of severe slugging during depressurization of an oil/gas pipeline Nordsveen, M. Hærdig, A. Dynamic simulators for pipelines with multiphase flow have proved to be important computational tools for both design and operational support of oil and gas production systems. One important aim of such simulators is to predict the arrival time and magnitude of outlet liquid transients after production changes made by an operator of a pipeline. A multiphase flow simulator (OLGA-94.1) with a two-fluid model has been applied to simulate depressurization of a pipeline during a shutdown procedure. During depressurization liquid slugs may form and propagate towards the outlet. The importance of the numerical method for predictions of such transients is demonstrated by using an Eulerian, finite difference, implicit, upwind scheme both with and without a front tracking scheme. First the initial conditions for the depressurization is established from a shut-down simulation where the production at the inlet is closed down, and the liquid comes to rest at low points along the pipeline. A realistic depressurization is simulated by opening a choke at the outlet of the pressurized pipeline. The numerical scheme without front tracking (standard scheme) gives outlet gas and liquid flow rates which are smeared out in time due to numerical diffusion. Simulations with the front tracking scheme give intermittent gas-liquid flow arriving as sharp fronts at the outlet. The total remaining fluid in the pipeline after the depressurization is larger when using the standard scheme. Depressurization, severe slugging,

oai:mic.1997.1.4 2010-03-20

eng Journal article 1997-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1997-1-4.asp Fulltext http://www.mic-journal.no/PDF/1997/MIC-1997-1-4.pdf Simulation of ordinary differential equations on manifolds: some numerical experiments and verifications Marthinsen, Arne Munthe-Kaas, Hans Owren, Brynjulf During the last few years, different approaches for integrating ordinary differential equations on manifolds have been published. In this work, we consider two of these approaches. We present some numerical experiments showing benefits and some pitfalls when using the new methods. To demonstrate how they work, we compare with well known classical methods, e.g. Newmark and Runge-Kutta methods. Ordinary differential equations, manifolds, numerical analysis,

oai:mic.1997.2.1 2010-03-20

eng Journal article 1997-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1997-2-1.asp Fulltext http://www.mic-journal.no/PDF/1997/MIC-1997-2-1.pdf Multi-purpose process simulators Øgård, Ommund Eikaas, Tor Ivar The first part of this paper describes a multi-purpose dynamic simulator for the Heidrun oil production plant. The simulator integrates a commercial dynamic simulation model with the actual process control system to enable dynamic simulation, control system verification and operator training within the same framework and based on the same models and configuration data. The control system configuration can be imported directly into the simulator. This simplifies simulator maintenance and ensure consistency between the simulator and the real plant. The entire system runs on standard Unix work stations. The simulator has so far been used for initial operator training, control system verification and controller tuning. Dynamic simulation, operator training,

oai:mic.1997.2.2 2010-03-20

eng Journal article 1997-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1997-2-2.asp Fulltext http://www.mic-journal.no/PDF/1997/MIC-1997-2-2.pdf Applications of computational fluid dynamics in optimisation and design of metallurgical processes Johansen, Stein T. During the last two decades computational fluid dynamics (CFD) has become a powerful tool for analysing and designing metallurgical processes. In this paper we give examples on how these techniques can be applied to a large variety of processes and also how CFD can be used to predict heat and mass transfer from fundamental principles. The paper is restricted to the applications of CFD at SINTEF Materials Technology. The examples given in the paper will range from treatment of raw materials, environmental issues, furnace processes and combustion, magnetohydrodynamics, melt treatment to casting. Computational fluid dynamics, process technology, turbulence, granular flows,

oai:mic.1997.2.3 2010-03-20

eng Journal article 1997-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1997-2-3.asp Fulltext http://www.mic-journal.no/PDF/1997/MIC-1997-2-3.pdf Simulation and visualization of coupled hydrodynamical, chemical and biological models Slagstad, Dag Iversen, T. This paper briefly describes the principles of hydrodynamical and ecological modelling of marine systems and how model results are presented by use of MATLAB. Two application examples are shown. One refers to modelling and simulation of the carbon vertical transport in the Greenland Sea and the other is a study on the effect of wind pattern for the invasion success of zooplankton from the Norwegian Sea into the North Sea by use of particle tracking. Modelling, simulation, carbon cycle, hydrodynamics,

oai:mic.1997.2.4 2010-03-20

eng Journal article 1997-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1997-2-4.asp Fulltext http://www.mic-journal.no/PDF/1997/MIC-1997-2-4.pdf Modelling and simulation of phase equilibrium in dynamic systems Dahl, T. Hashemi-Ahmady, A. Lie, Bernt The article reports an investigation on how to efficiently describe phase equilibrium in dynamic systems, and how to solve the resulting equations numerically. An overview of possible solution strategies is given. Different thermodynamic models are briefly reviewed, and important algorithms like PT flash are described. A flash tank with a mixture of propane and propylene is simulated to illustrate some different solution strategies. Process dynamics, phase equilibrium, process simulation,

oai:mic.1997.2.5 2010-03-20

eng Journal article 1997-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1997-2-5.asp Fulltext http://www.mic-journal.no/PDF/1997/MIC-1997-2-5.pdf Model-predictive control and real-time optimization of a cat cracker unit Strand, Stig Veland, Lars Håkon A project for control and optimization of the Residual Catalytic Cracking Process at the Mongstad refinery is near completion. Four model-predictive control applications have been successfully implemented, using the IDCOM control software from Setpoint Inc. The most attractive feature of the controller is the well-defined control prioritizing hierarchy, and the linear impulse-response models have proved to give satisfactory performance on this process. Excitation and identification of the dynamic models proved to be a difficult task, and careful design and monitoring of the tests was mandatory in order to produce good results. Multi-variable Pseudo Random Binary Test Sequences were used for the excitation. Technical performance and operator acceptance of the new control functions have been good, but it is realized that a continuing effort is needed to fine-tune and maintain such functions. Model predictive control, on-line optimization,

oai:mic.1997.3.1 2010-03-20

eng Journal article 1997-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1997-3-1.asp Fulltext http://www.mic-journal.no/PDF/1997/MIC-1997-3-1.pdf Dynamics and Control of Distillation Columns - A Critical Survey Skogestad, Sigurd Distillation column dynamics and control have been viewed by many as a very mature or even dead field. However, as is discussed in this paper significant new results have appeared over the last 5-10 years. These results include multiple steady states and instability in simple columns with ideal thermodynamics (which was believed to be impossible), the understanding of the difference between various control configurations and the systematic transformation between these, the feasibility of using the distillate-bottom structure, for control (which was believed to be impossible), the importance of flow dynamics for control studies, the fundamental problems in identifying models from open-loops responses, the use of simple regression estimators to estimate composition from temperatures, and an improved general understanding of the dynamic behavior of distillation columns which includes a better understanding of the fundamental difference between internal and external flow, simple formulas for estimating the dominant time constant, and a derivation of the linearizing effect of logarithmic transformations. These issues apply to all columns, even for ideal mixtures and simple columns with only two products. In addition, there have been significant advances for cases with complex thermodynamics and complex column configurations. These include the behavior and control of azeotropic distillation columns, and the possible complex dynamics of nonideal mixtures and of interlinked columns. However, both for the simple and more complex cases there are still a number of areas where further research is needed. Distillation, process control, process dynamics, control configuration, simulation, low-order model,

oai:mic.1997.3.2 2010-03-20

eng Journal article 1997-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1997-3-2.asp Fulltext http://www.mic-journal.no/PDF/1997/MIC-1997-3-2.pdf A State Space Model for the Wood Chip Refining Model Ruscio, David Di Balchen, Jens G. A detailed dynamic model of the fibre size distribution between the refiner discs, distributed along the refiner radius, is presented. Both one- and two-dimensional descriptions for the fibre or shive geometry are given. It is shown that this model may be simplified and that analytic solutions exist under non-restrictive assumptions. A direct method for the recursive estimation of unknown parameters is presented. This method is applicable to linear or linearized systems which have a triangular structure. Mathematical models, fibers, distribution, disk refiners, time, radius,

oai:mic.1997.3.3 2010-03-20

eng Journal article 1997-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1997-3-3.asp Fulltext http://www.mic-journal.no/PDF/1997/MIC-1997-3-3.pdf Exponential Stabilization of an Underactuated Surface Vessel Pettersen, Kristin Y. Egeland, Olav The paper shows that a large class of underactuated vehicles cannot be asymptotically stabilized by either continuous or discontinuous state feedback. Furthermore, stabilization of an underactuated surface vessel is considered. Controllability properties of the surface vessels is presented, and a continuous periodic time-varying feedback law is proposed. It is shown that this feedback law exponentially stabilizes the surface vessel to the origin, and this is illustrated by simulations. Nonlinear control, underactuated vehicles,

oai:mic.1997.4.1 2010-03-20

eng Journal article 1997-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1997-4-1.asp Fulltext http://www.mic-journal.no/PDF/1997/MIC-1997-4-1.pdf Object-oriented Ferromanganese Furnace Model Wasbø, Stein O. Foss, Bjarne A. Tronstad, Ragnar The high-carbon ferromanganese furnace is a semi-continuous unit process, with a number of complex, and partly unknown mechanisms taking place inside it. The furnace operation has been characterized by fluctuations in vital process variables. Many of the operational problems are caused by the lack of information about the internal conditions. This paper presents an object-oriented model of the furnace and its future application in monitoring the furnace conditions. The object-orientation ensures that the model becomes easy to modify as new process knowledge is collected. Object-oriented programming, industrial furnace, metallurgy,

oai:mic.1997.4.2 2010-03-20

eng Journal article 1997-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1997-4-2.asp Fulltext http://www.mic-journal.no/PDF/1997/MIC-1997-4-2.pdf Controlling pH in a Precipitation Plant Støle-Hansen, Kjell Foss, Bjarne A. This paper deals with pH control in a precipitation and dissolution process. The process is a part of the electrolyte purification plant at Falconbridge Nikkelverk in Kristiansand, Norway. The process including the present strategy for pH control are presented, and experienced weaknesses with this strategy are described. A rigorous dynamic model of the process is briefly summarized. This model was developed in earlier work with the purpose of being a tool for control design. Because of the precipitation in form of hydroxides and the limited dissolution rate of nickel carbonate, the process is approximately linear in pH. Therefore, an alternative strategy for pH control based on adding derivative and feed forward action is suggested. The alternative control strategy is by simulations shown to give severe improvements in performance. The robustness of the proposed controller is briefly analysed. pH control, metals, chemical industry,

oai:mic.1997.4.3 2010-03-20

eng Journal article 1997-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1997-4-3.asp Fulltext http://www.mic-journal.no/PDF/1997/MIC-1997-4-3.pdf Passivity-Based Control of a Class of Blondel-Park Transformable Electric Machines Nicklasson, Per J. Ortega, Romeo Espinosa-Perez, Gerardo In this paper we study the viability of extending, to the general rotating electric machine's model, the passivity-based controller method that we have developed for induction motors. In this approach the passivity (energy dissipation) properties of the motor are taken advantage of at two different levels. First, we prove that the motor model can be decomposed as the feedback interconnection of two passive subsystems, which can essentially be identified with the electrical and mechanical dynamics. Then, we design a torque tracking controller that preserves passivity for the electrical subsystem, and leave the mechanical part as a "passive disturbance". In position or speed control applications this procedure naturally leads to the well known cascaded controller structure which is typically analyzed invoking time-scale separation assumptions. A key feature of the new cascaded control paradigm is that the latter arguments are obviated in the stability analysis. Our objective in this paper is to characterize a class of machines for which such a passivity-based controller solves the output feedback torque tracking problem. Roughly speaking, the class consists of machines whose nonactuated dynamics are well damped and whose electrical and mechanical dynamics can be suitably decoupled via a coordinate transformation. The first condition translates into the requirement of approximate knowledge of the rotor resistances to avoid the need of injecting high gain into the loop. The latter condition is known in the electric machines literature as Blondel-Park transformability, and in practical terms it requires that the air-gap magnetomotive force must be suitably approximated by the first harmonic in its Fourier expansion. These conditions, stemming from the construction of the machine, have a clear physical interpretation in terms of the couplings between its electrical, magnetic and mechanical dynamics, and are satisfied by a large number of practical machines. The passivity-based controller presented here reduces to the well known indirect vector controller for current-fed induction machines. Our developments constitute an extension, to voltage-fed machines, of this de facto standard in industrial applications. Furthermore, our analysis provides it with a solid theoretical foundation. Passivity-based control, electric machines,

oai:mic.1998.1.1 2010-03-20

eng Journal article 1998-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1998-1-1.asp Fulltext http://www.mic-journal.no/PDF/1998/MIC-1998-1-1.pdf Hard constraints in control state variables of multivariable nonlinear processes resolved by elementary nonlinear decoupling Balchen, Jens G. Sandrib, Bjarne A model based control strategy for nonlinear multivariable processes having hard constraints on both control and state variables, is derived based upon the concept of Elementary Nonlinear Decoupling (END). In END a property space is defined which has the same dimension as the control space and which permits inverse control. An optimization procedure is used to design a property transformation that gives the best solution in terms of performance, stability, robustness, etc. This control strategy is shown to be convenient when control and state variables are subject to hard constraints. When constraint limits are reached, new property variables are introduced which approximate the variables to be constrained and thereby achieving fast and accurate control on constraint boundaries. Multivariable control, nonlinear control, nonlinear decoupling,

oai:mic.1998.1.2 2010-03-20

eng Journal article 1998-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1998-1-2.asp Fulltext http://www.mic-journal.no/PDF/1998/MIC-1998-1-2.pdf Speed and surge control for a lower order centrifugal compressor model Gravdahl, Jan T. Egeland, Olav A model of a variable speed centrifugal compression system is presented. The model is based on the work of Greitzer (1976), but the compressor characteristic is developed by modelling the losses in the compressor. For surge control, a close coupled valve is employed. This valve is placed immediately downstream of the compressor, and the pressure drop over the valve is used as the control variable. This makes it possible to manipulate the shape of the equivalent compressor, consisting of compressor and valve. The speed of the compressor is controlled with a PI-controller. Semi-global exponential stability of the model with the proposed controllers is proven by the use of Lyapunovs theorem. Centrifugal compressor, modelling, surge control,

oai:mic.1998.1.3 2010-03-20

eng Journal article 1998-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1998-1-3.asp Fulltext http://www.mic-journal.no/PDF/1998/MIC-1998-1-3.pdf On the AlF3 and temperature control of an aluminium electrolysis cell Drengstig, Tormod Ljungquist, Dag Foss, Bjarne A. In this paper we propose a control strategy for excess AlF3 and bath temperature of a prebake aluminum electrolysis cell based on analyzes of measured data and studies of a simple dynamic model. Model validation indicates that there are dynamics that the model does not capture, and hence, we use real data of excess AlF3 and bath temperature to estimate AlF3 and energy disturbances respectively. The estimation results show that the energy disturbance is the dominating disturbance. Hence, the proposed control strategy is based on an almost constant AlF3 input close to average consumption and energy manipulations to compensate for the disturbances. This requires the possibility tor the resistance reference to be reduced without decreasing the current efficiency. Compared to present control strategies, this introduces an additional degree of freedom in the controller. The proposed control strategy may imply a significant economic potential through increased and stabilized current efficiency, reduced and stabilized energy consumption, reduced consumption of expensive additives and prolongation of cell life. Modeling, metals industry, temperature control, electromechanical processes,

oai:mic.1998.2.1 2010-03-20

eng Journal article 1998-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1998-2-1.asp Fulltext http://www.mic-journal.no/PDF/1998/MIC-1998-2-1.pdf Design of automatic thruster assisted mooring systems for ships Strand, Jan P. Sørensen, Asgeir J. Fossen, Thor I. This paper addresses the mathematical modelling and controller design of an automatic thruster assisted position mooring system. Such control systems are applied to anchored floating production offloading and storage vessels and semi-subs. The controller is designed using model based control with a LQG feedback controller in conjunction with a Kalman filter. The controller design is in addition to the environmental loads accounting for the mooring forces acting on the vessel. This is reflected in the model structure and in the inclusion of new functionality. Position mooring, model-based control, hydrodynamics,

oai:mic.1998.2.2 2010-03-20

eng Journal article 1998-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1998-2-2.asp Fulltext http://www.mic-journal.no/PDF/1998/MIC-1998-2-2.pdf Dynamic system multivariate calibration by system identification methods Ergon, Rolf In the first part of the paper, the optimal estimator for normally nonmeasured primary outputs from a linear and time invariant dynamic system is developed. The estimator is based on an underlying Kalman filter, utilizing all available information in known inputs and measured secondary outputs. Assuming sufficient experimental data, the optimal estimator can be identified by specifying an output error model in a standard prediction error identification method. It is further shown that static estimators found by the ordinary least squares method or multivariate calibration by means of principal component regression (PCR) or partial least squares regression (PLSR) can be seen as special cases of the optimal dynamic estimator. Finally, it is shown that dynamic system PCR and PLSR solutions can be developed as special cases of the general estimator for dynamic systems. Estimation, system identification,

oai:mic.1998.2.3 2010-03-20

eng Journal article 1998-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1998-2-3.asp Fulltext http://www.mic-journal.no/PDF/1998/MIC-1998-2-3.pdf Dynamic system calibration: the low primary output sampling rate case Ergon, Rolf In many industrial cases it is not feasible to measure primary outputs, e.g. product quality, from production processes on-line. It is thus of interest to estimate such outputs from known process inputs and secondary process measurements. In an earlier paper it is shown that optimal estimators can be identified from data recorded during an informative experiment, with the primary outputs sampled at the same high rate as the inputs and secondary outputs. In the present paper it is shown that optimal estimators can also be found from data where the primary outputs are sampled at a low and possibly irregular rate. Product quality, estimation,

oai:mic.1998.2.4 2010-03-20

eng Journal article 1998-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1998-2-4.asp Fulltext http://www.mic-journal.no/PDF/1998/MIC-1998-2-4.pdf Constrained and regularized system identification Johansen, Tor A. Prior knowledge can be introduced into system identification problems in terms of constraints on the parameter space, or regularizing penalty functions in a prediction error criterion. The contribution of this work is mainly an extension of the well known FPE (Final Production Error) statistic to the case when the system identification problem is constrained and contains a regularization penalty. The FPECR statistic (Final Production Error with Constraints and Regularization) is of potential interest as a criterion for selection of both regularization parameters and structural parameters such as order. Regularization, Optimization, Parameter Estimation,

oai:mic.1998.3.1 2010-03-20

eng Journal article 1998-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1998-3-1.asp Fulltext http://www.mic-journal.no/PDF/1998/MIC-1998-3-1.pdf The partial least squares algorithm: a truncated Cayley-Hamilton series approximation used to solve the regression problem Di Ruscio, David In this paper it is shown that the PLS algorithm for univariate data is equivalent to using a truncated Cayley-Hamilton polynomial expression of degree 1 less than a less than r for the matrix inverse inv(X'X) in R^(rxr) used to compute the LS solution. Furthermore, the a coefficients in this polynomial are computed as the LS optimal solution (minimizing parameters) to the prediction error. The resulting solution is non-iterative. The solution can be expressed in terms of one matrix inverse and is given by BPLS = Ka * inv(Ka'*X'*X*Ka)*Ka'*X'*Y where Ka in R^(rxr) is the controllability (Krylov) matrix for the pair (X'X,X'Y).

oai:mic.1998.3.2 2010-03-20

eng Journal article 1998-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1998-3-2.asp Fulltext http://www.mic-journal.no/PDF/1998/MIC-1998-3-2.pdf A finite-difference method for linearization in nonlinear estimation algorithms Schei, Tor S. Linearizations of nonlinear functions that are based on Jacobian matrices often cannot be applied in practical applications of nonlinear estimation techniques. An alternative linearization method is presented in this paper. The method assumes that covariance matrices are determined on a square root factored form. A factorization of the output covariance from a nonlinear vector function is directly determined by "perturbing" the nonlinear function with the columns of the factored input covariance, without explicitly calculating the linearization and with no differentiations involved. The output covariance is more accurate than that obtained with the ordinary Jacobian linearization method. It also has an advantage that Jacobian matrices do not have to be derived symbolically. Covariance matrices, estimation algorithms, extended Kalman filters, factorization methods, nonlinear filters, Jacobian matrices, linearization, parameter estimation, recursive estimation,

oai:mic.1998.3.3 2010-03-20

eng Journal article 1998-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1998-3-3.asp Fulltext http://www.mic-journal.no/PDF/1998/MIC-1998-3-3.pdf A field study of the industrial modeling process Foss, Bjarne A. Lohmann, B. Marquardt, W. This paper analyzes the modeling process by means of a field study in the chemical industries. A diversified set of experienced modelers from two different countries have been interviewed using a case study approach. The interviews focussed on the modeling process. Other issues like life-cycle perspectives and the use of modeling in the process industries were treated as well. The information has been summarized and presented in a structured manner imposing the least possible bias from the authors. Based on the interview information the modeling process is discussed in detail. Further, fundamental research issues are identified, and a research agenda is proposed. Predictive control, hybrid control,

oai:mic.1998.4.1 2010-03-20

eng Journal article 1998-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1998-4-1.asp Fulltext http://www.mic-journal.no/PDF/1998/MIC-1998-4-1.pdf MPC in systems with continuous and discrete control inputs Slupphaug, Olav Vada, Jostein Foss, Bjarne A. In this paper we point out potential problems in systems where both logic and continuous control influence a continuous plant. We also propose model predictive control (MPC) based approaches for handling the problems. Simulations on a simple but nontrivial plant support the discussion. Predictive control, hybrid control,

oai:mic.1998.4.2 2010-03-20

eng Journal article 1998-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1998-4-2.asp Fulltext http://www.mic-journal.no/PDF/1998/MIC-1998-4-2.pdf A software environment for gain scheduled controller design Johansen, Tor A. Hunt, K. J. Fritz, H. Recent theoretical developments have improved the understanding of gain scheduled control and suggested new methods for design, analysis and implementation of such nonlinear control systems. An integrated software environment for gain scheduled local controller network design and analysis, including computer-aided modelling and system identification, is described. Sonic background theory is included, and a speed control design problem for an experimental vehicle illustrates the application of the approach. Nonlinear control, gain scheduling,

oai:mic.1998.4.3 2010-03-20

eng Journal article 1998-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1998-4-3.asp Fulltext http://www.mic-journal.no/PDF/1998/MIC-1998-4-3.pdf The Macroeconomy as a Network of Money-Flow Transfer Functions Andresen, Trond An introduction on A.W. Phillips’ "hydraulic" macroeconomic models is given. His (and others economists’) notion that a macroeconomy may reasonably be considered to have dynamics corresponding to a first order time lag transfer function, is justified in this paper by aggregation of individual micro agents. In connection with this economic application, we derive and discuss a theorem and some rules for general networks of time lagged blocks. Numerical simulations of networks of agents are undertaken, supporting the validity of the first order time lag aggregate model. Finally, an application is presented—a model of financial accumulation and possible collapse. Macroeconomics, network, block diagram, time lag,

oai:mic.1999.1.1 2010-03-20

eng Journal article 1999-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1999-1-1.asp Fulltext http://www.mic-journal.no/PDF/1999/MIC-1999-1-1.pdf Modeling and control of a gravity gradient stabilised satellite Skullestad, Aage This paper describes attitude control, i.e., 3-axes stabilisation and pointing, of a proposed Norwegian small gravity gradient stabilized satellite to be launched into low earth orbit. Generally, a gravity gradient stabilised system has limited stability and pointing capabilities, and wheels and/or magnetic coils are added in order to improve the attitude control. The best attitude accuracy is achieved using wheels, which can give accuracies down to less than one degree, but wheels increase the complexity and cost of the satellite. Magnetic coils allow cheaper satellites, and are an attractive solution to small, inexpensive satellites in low earth orbits and may provide an attitude control accuracy of a few degrees. Scientific measurements often require accurate attitude control in one or two axes only. Combining wheel and coil control may, in these cases, provide the best solutions. The simulation results are based on a linearised mathematical model of the satellite. 3-axes stabilisation, satellite, multivariable control,

oai:mic.1999.1.2 2010-03-20

eng Journal article 1999-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1999-1-2.asp Fulltext http://www.mic-journal.no/PDF/1999/MIC-1999-1-2.pdf Nonlinear oscillations in coriolis based gyroscopes Kristiansen, Dag Egeland, Olav In this paper we model and analyze nonlinear oscillations which are known to exist in some Coriolis based gyroscopes due to large amplitude excitation in the drive loop. A detailed derivation of a dynamic model for a cylinder gyroscope which includes geometric nonlinearities is given, and energy transfer between the system's modes are analyzed using perturbation theory and by proposing a simplified model. The model is also simulated, and the results are shown to give an accurate description of the experimental results. This work is done in order to gain a better understanding of the gyroscope's dynamics, and is intended to be a starting point for designing nonlinear observers and vibration controllers for the gyroscope in order to increase the performance. Cylinder gyroscopes, nonlinear vibrations,

oai:mic.1999.2.1 2010-03-20

eng Journal article 1999-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1999-2-1.asp Fulltext http://www.mic-journal.no/PDF/1999/MIC-1999-2-1.pdf How have we arrived at the present state of knowledge in process control? Is there a lesson to be learned? Balchen, Jens G. The utilization of the results of control theory in the process control field has been lagginig behind other application fields such as aerospace for many years. It is argued that the availability of high capacity computing at low price will change this situation and that new powerful control techniques can now be implemented in process control. Control theory, process control, computer technology, model-based control,

oai:mic.1999.2.2 2010-03-20

eng Journal article 1999-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1999-2-2.asp Fulltext http://www.mic-journal.no/PDF/1999/MIC-1999-2-2.pdf Model predictive control of a crude oil distillation column Hovd, Morten Michaelsen, Rune Montin, Tomas The project of designing and implementing model based predictive control on the vacuum distillation column at the Nynäshamn Refinery of Nynäs AB is described in this paper. The paper describes in detail the modeling for the model based control, covers the controller implementation, and documents the benefits gained from the model based controller. Modelling, model updating, TBP curve,

oai:mic.1999.2.3 2010-03-20

eng Journal article 1999-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1999-2-3.asp Fulltext http://www.mic-journal.no/PDF/1999/MIC-1999-2-3.pdf Tutorial on nonlinear backstepping: Applications to ship control Fossen, Thor I. Strand, Jan P. The theoretical foundation of nonlinear backstepping designs is presented in a tutorial setting. This includes a brief review of integral backstepping, extensions to SISO and MIMO systems in strict feedback form and physical motivated case studies. Parallels and differences to feedback linearization where it is shown how so-called "good nonlincarities" can be exploited in the design are also made. Nonlinear control, backstepping,

oai:mic.1999.3.1 2010-03-20

eng Journal article 1999-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1999-3-1.asp Fulltext http://www.mic-journal.no/PDF/1999/MIC-1999-3-1.pdf Constrained quadratic stabilization of discrete-time uncertain nonlinear multi-model systems using piecewise affine state-feedback Slupphaug, Olav Foss, Bjarne A. In this paper a method for nonlinear robust stabilization based on solving a bilinear matrix inequality (BMI) feasibility problem is developed. Robustness against model uncertainty is handled. In different non-overlapping regions of the state-space called clusters the plant is assumed to be an element in a polytope which vertices (local models) are affine systems. In the clusters containing the origin in their closure, the local models are restricted to be linear systems. The clusters cover the region of interest in the state-space. An affine state-feedback is associated with each cluster. By utilizing the affinity of the local models and the state-feedback, a set of linear matrix inequalities (LMIs) combined with a single nonconvex BMI are obtained which, if feasible, guarantee quadratic stability of the origin of the closed-loop. The feasibility problem is attacked by a branch-and-bound based global approach. If the feasibility check is successful, the Liapunov matrix and the piecewise affine state-feedback are given directly by the feasible solution. Control constraints are shown to be representable by LMIs or BMIs, and an application of the control design method to robustify constrained nonlinear model predictive control is presented. Also, the control design method is applied to a simple example. Constrained control, nonlinear control, robust control, multi-model systems, BMI control, MPC, receeding horizon control,

oai:mic.1999.3.2 2010-03-20

eng Journal article 1999-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1999-3-2.asp Fulltext http://www.mic-journal.no/PDF/1999/MIC-1999-3-2.pdf An aided navigation post processing filter for detailed seabed mapping UUVs Gade, Kenneth Jalving, Bjørn HUGIN is an untethered underwater vehicle (UUV) intended for bathymetric data collection for detailed seabed surveying. The HUGIN sensor suite, consisting of standard commercially available navigation sensors and a multibeam echosounder, is briefly presented. A Kalman filter based post processing integration of UUV sensors and survey vessel sensors is discussed. Resulting UUV position and heading accuracy and important characteristics of the post processing filter is shown with simulation results and results from a commercial survey operation. Finally, we briefly show how the claimed position and heading accuracy has been verified. Aided navigation, Kalman filter, Smoothing, Untethered Underwater Vehicle (UUV),

oai:mic.1999.3.3 2010-03-20

eng Journal article 1999-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1999-3-3.asp Fulltext http://www.mic-journal.no/PDF/1999/MIC-1999-3-3.pdf Nonlinear control of ships minimizing the position tracking errors Berge, Svein P. Ohtsu, Kohei Fossen, Thor I. In this paper, a nonlinear tracking controller with integral action for ships is presented. The controller is based on state feedback linearization. Exponential convergence of the vessel-fixed position and velocity errors are proven by using Lyapunov stability theory. Since we only have two control devices, a rudder and a propeller, we choose to control the longship and the sideship position errors to zero while the heading is stabilized indirectly. A Virtual Reference Point (VRP) is defined at the bow or ahead of the ship. The VRP is used for tracking control. It is shown that the distance from the center of rotation to the VRP will influence on the stability of the zero dynamics. By selecting the VRP at the bow or even ahead of the bow, the damping in yaw can be increased and the zero dynamics is stabilized. Hence, the heading angle will be less sensitive to wind, currents and waves. The control law is simulated by using a nonlinear model of the Japanese training ship Shiojimaru with excellent results. Wind forces are added to demonstrate the robustness and performance of the integral controller. Nonlinear control, Lyapunov stability, ship control,

oai:mic.1999.4.1 2010-03-20

eng Journal article 1999-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1999-4-1.asp Fulltext http://www.mic-journal.no/PDF/1999/MIC-1999-4-1.pdf Global Practical Stabilization and Tracking for an Underactuated Ship - A Combined Averaging and Backstepping Approach Pettersen, Kristin Y. Nijmeijer, Henk We solve both the global practical stabilization and tracking problem for an underactuated ship, using a combined integrator backstepping and averaging approach. Exponential convergence to an arbitrarily small neighbourhood of the origin and of the reference trajectory, respectively, is proved. Simulation results are included. Time-varying control, exponential convergence,

oai:mic.1999.4.2 2010-03-20

eng Journal article 1999-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1999-4-2.asp Fulltext http://www.mic-journal.no/PDF/1999/MIC-1999-4-2.pdf Hidden Markov Models as a Process Monitor in Robotic Assembly Hovland, Geir E. McCarragher, Brenan J. A process monitor for robotic assembly based on hidden Markov models (HMMs) is presented. The HMM process monitor is based on the dynamic force/torque signals arising from interaction between the workpiece and the environment. The HMMs represent a stochastic, knowledge-based system in which the models are trained off-line with the Baum-Welch reestimation algorithm. The assembly task is modeled as a discrete event dynamic system in which a discrete event is defined as a change in contact state between the workpiece and the environment. Our method (1) allows for dynamic motions of the workpiece, (2) accounts for sensor noise and friction, and (3) exploits the fact that the amount of force information is large when there is a sudden change of discrete state in robotic assembly. After the HMMs have been trained, the authors use them on-line in a 2D experimental setup to recognize discrete events as they occur. Successful event recognition with an accuracy as high as 97with a training set size of only 20 examples for each discrete event. Discrete event systems, sensory perception,

oai:mic.1999.4.3 2010-03-20

eng Journal article 1999-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-1999-4-3.asp Fulltext http://www.mic-journal.no/PDF/1999/MIC-1999-4-3.pdf Stabilization of a Pitch Axis Flight Control Experiment with Input Rate Saturation Lauvdal, Trygve Murray, Richard M. Motivated by some specific problems in flight control and roll stabilization of ships, we present a technique for stabilizing a chain of integrators in the presence of rate limitations on the input. Our technique improves on several existing techniques in the literature and has a number of interesting features. The controller is evaluated experimentally on a pitch axis flight control experiment at Caltech. The experimental results show that even in the presence of rate limits that cause a linear controller to go unstable, the time-varying controller stabilizes the system with minimal loss in performance. Rate saturation, nonlinear control,

oai:mic.2000.1.1 2010-03-20

eng Journal article 2000-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2000-1-1.asp Fulltext http://www.mic-journal.no/PDF/2000/MIC-2000-1-1.pdf Thirty Years of Research on the Application of Cybernetic Methods in Fisheries and Aquaculture Technology Balchen, Jens G. The paper surveys the research activities at the Department of Engineering Cybernetics, Norwegian University of Science and Technology, Trondheim, Norway, in the application of cybernetic principles in fisheries technology, aqua-culture technology and ocean ranching during the period 1969-1999. It is believed that the results obtained in these activities will have an impact upon the future developments in one of the most important sectors of the Norwegian economy. Numerous reports and publications are listed in the comprehensive bibliography. Cybernetics, Fisheries technology, Aquaculture, Ocean ranching, Mathematical modeling, Ocean systems, Model identification, Fish behavior, Control of fish behavior, Instrumentation and biotelemetry,

oai:mic.2000.2.1 2010-03-20

eng Journal article 2000-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2000-2-1.asp Fulltext http://www.mic-journal.no/PDF/2000/MIC-2000-2-1.pdf Identification of Vibration Parameters in a Spacecraft using Kalman Filters, Numerical Search and Phase-Locked Loops Skullestad, Aage Communication in space requires antennas that are accurately pointed. Often antennas are mounted on lightly damped space structures, that are easily set into vibration, which decreases the pointing accuracy of the antennas. Knowing the vibration frequencies simplifies the control tasks and may also improve the pointing accuracy. This paper describes identification of vibration frequencies in a space structure, based on frequency weighted Kalman filters, a Gauss-Newton numerical search method and phase-locked loops. Space structures, parameter idenfication, Kalman filters,

oai:mic.2000.2.2 2010-03-20

eng Journal article 2000-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2000-2-2.asp Fulltext http://www.mic-journal.no/PDF/2000/MIC-2000-2-2.pdf Evaluation of Dynamic Models of Distillation Columns with Emphasis on the Initial Response Wittgens, Bernd Skogestad, Sigurd The flow dynamics (tray hydraulics) are of key importance for the initial dynamic response of distillation columns. The most important parameters are the liquid holdup, the liquid hydraulic time constant and the vapor constant representing the initial effect of a change in vapor flow on liquid flow. In the paper we present methods for determining these parameters experimentally, and compare the results with estimates from available correlations such as the Francis Weir formula. Distillation dynamics, tray hydraulics,

oai:mic.2000.2.3 2010-03-20

eng Journal article 2000-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2000-2-3.asp Fulltext http://www.mic-journal.no/PDF/2000/MIC-2000-2-3.pdf Convergence Properties of an Extended Least Squares (ELS) Variant Henriksen, Rolf By factorizing the A- and B-polynomials in an ARMAX model and filtering the input/output data with the appropriate factors thereof, the parameters of the model can be estimated in a decentralized fashion. This may improve the robustness of sonic estimators significantly, e.g., when applied to very stiff systems. Earlier work on these techniques has established both local and global properties for some LS, IV, and PE variants. An ELS variant has, however, never been considered, and a variant of this type is introduced. Local and global convergence properties of this variant are analyzed. ELS methods, convergence analysis,

oai:mic.2000.3.1 2010-03-20

eng Journal article 2000-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2000-3-1.asp Fulltext http://www.mic-journal.no/PDF/2000/MIC-2000-3-1.pdf Nonlinear Passive Control and Observer Design for Ships Fossen, Thor Inge Starting with passivity of the ambient water-ship system this article proceeds with nonlinear observer design, design of dynamic ship positioning systems and weather optimal positioning control systems exploiting the passivity properties of the vessel and the surrounding water. The article gives an overview of methods for passive ship control and observer design. Passivity, nonlinear control, observers, ship control,

oai:mic.2000.4.1 2010-03-20

eng Journal article 2000-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2000-4-1.asp Fulltext http://www.mic-journal.no/PDF/2000/MIC-2000-4-1.pdf A Nonlinear Observer for Integration of GPS and Inertial Navigation Systems Vik, Bjørnar Fossen, Thor Inge GPS and INS have complementary properties and they are therefore well suited for integration. The integrated solution offers better long term accuracy than a stand-alone INS, and better integrity, availability and continuity than a stand-alone GPS receiver, making it suitable for demanding applications. The integrated filter is nonlinear both in state and measurements, and the extended Kalman-filter has been used with good results, but it has not been proven globally stable, and it is also computationally intensive, especially within a direct integration architecture. In this work a nonlinear observer suitable for direct integration is presented. Global exponent ial stability of the origin of the combined attitude and velocity error systems is proven along with robust stability in the presence of noise and unmodelled dynamics.

oai:mic.2000.4.2 2010-03-20

eng Journal article 2000-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2000-4-2.asp Fulltext http://www.mic-journal.no/PDF/2000/MIC-2000-4-2.pdf Plantwide control - A review and a new design procedure Larsson, Truls Skogestad, Sigurd Most (if not all) available control theories assume that a control structure is given at the outset. They therefore fail to answer some basic questions that a control engineer regularly meets in practice (Foss 1973): "Which variables should be controlled, which variables should be measured, which inputs should be manipulated, and which links should be made between them?" These are the questions that plantwide control tries to answer. There are two main approaches to the problem, a mathematically oriented approach (control structure design) and a process oriented approach. Both approaches are reviewed in the paper. We also provide some definitions of terms used within the area of plantwide control. Process control, control structure, control strategy,

oai:mic.2000.4.3 2010-03-20

eng Journal article 2000-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2000-4-3.asp Fulltext http://www.mic-journal.no/PDF/2000/MIC-2000-4-3.pdf Catalyst Deactivation: Control Relevance of Model Assumptions Lie, Bernt Himmelblau, David M. Two principles for describing catalyst deactivation are discussed, one based on the deactivation mechanism, the other based on the activity and catalyst age distribution. When the model is based upon activity decay, it is common to use a mean activity developed from the steady-state residence time distribution. We compare control-relevant properties of such an approach with those of a model based upon the deactivation mechanism. Using a continuous stirred tank reactor as an example, we show that the mechanistic approach and the population balance approach lead to identical models. However, common additional assumptions used for activity-based models lead to model properties that may deviate considerably from the correct one. Catalyst deactivation, dynamic models, population balance, activity model,

oai:mic.2001.1.1 2010-03-20

eng Journal article 2001-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2001-1-1.asp Fulltext http://www.mic-journal.no/PDF/2001/MIC-2001-1-1.pdf Stabilization of Stable Manifold of Upright Position of the Spherical Pendulum Ludvigsen, Hallgeir Shiriaev, Anton Egeland, Olav The stabilization problem of the upright position of the sherical pendulum is treated in detail. This problem is reduced to the stabilization of the stable manifold Omega_st of the upright position of the unforced spherical pendulum. It is shown that for any smooth feedback control derived by the speed-gradient algorithm with the objective to stabilize Omega_st the closed loop system has a limit cycle Gamma, which does not belong to the desired attractor Omega_st. It is shown that Gamma is hyperbolic. Passivity,

oai:mic.2001.1.2 2010-03-20

eng Journal article 2001-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2001-1-2.asp Fulltext http://www.mic-journal.no/PDF/2001/MIC-2001-1-2.pdf Computational Performance Analysis of Nonlinear Dynamic Systems using Semi-infinite Programming Johansen, Tor A. For nonlinear systems that satisfy certain regularity conditions it is shown that upper and lower bounds on the performance (cost function) can be computed using linear or quadratic programming. The performance conditions derived from Hamilton-Jacobi inequalities are formulated as linear inequalities defined pointwise by discretizing the state-space when assuming a linearly parameterized class of functions representing the candidate performance bounds. Uncertainty with respect to some system parameters can be incorporated by also gridding the parameter set. In addition to performance analysis, the method can also be used to compute Lyapunov functions that guarantees uniform exponential stability. Hamilton-Jacobi inequality, stability, Lyapunov functions, convex optimization,

oai:mic.2001.1.3 2010-03-20

eng Journal article 2001-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2001-1-3.asp Fulltext http://www.mic-journal.no/PDF/2001/MIC-2001-1-3.pdf Uncertainty Modeling and Robust Output Feedback Control of Nonlinear Discrete Systems: A Mathematical Programming Approach Slupphaug, Olav Imsland, Lars Foss, Bjarne A. We present a mathematical programming approach to robust control of nonlinear systems with uncertain, possibly time-varying, parameters. The uncertain system is given by different local affine parameter dependent models in different parts of the state space. It is shown how this representation can be obtained from a nonlinear uncertain system by solving a set of continuous linear semi-infinite programming problems, and how each of these problems can be solved as a (finite) series of ordinary linear programs. Additionally, the system representation includes control- and state constraints. The controller design method is derived from Lyapunov stability arguments and utilizes an affine parameter dependent quadratic Lyapunov function. The controller has a piecewise affine output feedback structure, and the design amounts to finding a feasible solution to a set of linear matrix inequalities combined with one spectral radius constraint on the product of two positive definite matrices. A local solution approach to this nonconvex feasibility problem is proposed. Complexity of the design method and some special cases such as state- feedback are discussed. Finally, an application of the results is given by proposing an on-line computationally feasible algorithm for constrained nonlinear state- feedback model predictive control with robust stability. Robust control, Constrained control, Affine parameter-dependent models, Bilinear matrix inequalities, Semi-infinite programming,

oai:mic.2001.2.1 2010-03-20

eng Journal article 2001-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2001-2-1.asp Fulltext http://www.mic-journal.no/PDF/2001/MIC-2001-2-1.pdf A Logarithmic-Amplitude Polar Diagram Andresen, Trond A polar diagram where the amplitude of the transfer function is on a logarithmic scale, is presented. This gives a one-size-fits-all diagram with no need for zooming in and out, and no need for additional reasoning about infinite-radius encirclements when there are poles on the imaginary axis - as opposed to what is usually neccessary with the standard polar (Nyquist-) diagram. All properties needed for stability considerations are upheld, such as encirclements, gain and phase margins. The path for s in the loop transfer function is carefully chosen with regard to possible poles on the imaginary axis. Small excursions into the right half plane in the form of arcs of different-sized logarithmic spirals result in corresponding large but finite arcs that do not overlap in the logarithmic polar plots. Logarithmic polar diagram, Nyquist criterion, stability,

oai:mic.2001.2.2 2010-03-20

eng Journal article 2001-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2001-2-2.asp Fulltext http://www.mic-journal.no/PDF/2001/MIC-2001-2-2.pdf Dynamic system multivariate calibration based on multirate sampling data Ergon, Rolf Halstensen, Maths The statistical principal component regression (PCR) and chemometric partial least squares regression (PLSR) algorithms based on latent variables (LV) modeling are effective tools for handling ill-conditioned regression data. In many process related cases the data form time series, and it may then be possible to improve the prediction/estimation results by utilizing the autocorrelation in the observations. This can be done by use of estimators found from experimental data by use of a combination of statistical/chemometric and system identification methods. In important industrial cases, the response variables arc product qualities which also in the experimental data are sampled at a low and possibly irregular rate, while the regressor variables are sampled at a higher rate. After a discussion of the options available, the paper shows how the autocorrelation of the regressor variables in such multirate sampling cases may be utilized by identification of latent variables based output error (LV + OE) estimators. An example using acoustic power spectrum regressor data is finally presented. Dynamic system, latent variables,

oai:mic.2001.2.3 2010-03-20

eng Journal article 2001-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2001-2-3.asp Fulltext http://www.mic-journal.no/PDF/2001/MIC-2001-2-3.pdf Semi-Global Practical Stabilization and Disturbance Adaptation for an Underactuated Ship Pettersen, Kristin Y. Nijmeijer, Henk We consider the problem of stabilizing the position and orientation of a ship to constant desired values, when the ship has only two independent controls and also the ship is subject to an environmental force of unknown magnitude. We propose a time-varying feedback control law and a disturbance adaptation law, and show that this provides semi-global practical asymptotic stability. The control and adaptation laws are derived using a combined integrator backstepping and averaging approach. Simulation results are presented. Nonlinear control, underactuated vehicles, disturbance adaptation,

oai:mic.2001.2.4 2010-03-20

eng Journal article 2001-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2001-2-4.asp Fulltext http://www.mic-journal.no/PDF/2001/MIC-2001-2-4.pdf An integration scheme for stiff solid-gas reactor models Foss, Bjarne A. Wasbø, Stein O. Many dynamic models encounter numerical integration problems because of a large span in the dynamic modes. In this paper we develop a numerical integration scheme for systems that include a gas phase, and solid and liquid phases, such as a gas-solid reactor. The method is based on neglecting fast dynamic modes and exploiting the structure of the algebraic equations. The integration method is suitable for a large class of industrially relevant systems. The methodology has proven remarkably efficient. It has in practice performed excellent and been a key factor for the success of the industrial simulator for electrochemical furnaces for ferro-alloy production. Stiff systems, numerical integration,

oai:mic.2001.3.1 2010-03-20

eng Journal article 2001-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2001-3-1.asp Fulltext http://www.mic-journal.no/PDF/2001/MIC-2001-3-1.pdf A didactically motivated PLS prediction algorithm Ergon, Rolf Esbensen, Kim H. The intention of this paper is to develop an easily understood PLS prediction algorithm, especially for the control community. The algorithm is based on an explicit latent variables model, and is otherwise a combination of the previously published Martens and Helland algorithms. A didactic connection to Kalman filtering theory is provided for a methodological overview. Latent variables models, PLS prediction,

oai:mic.2001.3.2 2010-03-20

eng Journal article 2001-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2001-3-2.asp Fulltext http://www.mic-journal.no/PDF/2001/MIC-2001-3-2.pdf Control of a gravity gradient stabilised satellite using fuzzy logic Skullestad, Aage Olsen, Kjetil Rennehvammen, Stein Fløystad, Håvard This paper describes attitude control of a small gravity gradient stabilised satellite. A gravity gradient stabilised satellite has limited stability and pointing capabilities, and magnetic coils are added in order to improve the accuracy of the attitude control. The magnetic coils are controlled using a fuzzy logic controller, based on a combination of membership functions and rules. The control of the pitch axis is separated from the roll and azimuth axes and excellent pitch angle accuracy is achieved. The roll and azimuth axes are controlled using a common magnetic coil, that has a non-linear and time-varying torque characteristic and, therefore, accurate roll and azimuth angular control become much more difficult to achieve. However, combining one roll controller and two azimuth controllers result in an acceptable roll and azimuth angular accuracy after a few orbital periods. 3-axes stabilisation, satellite, Fuzzy control,

oai:mic.2001.3.3 2010-03-20

eng Journal article 2001-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2001-3-3.asp Fulltext http://www.mic-journal.no/PDF/2001/MIC-2001-3-3.pdf Optimal operation of Petlyuk distillation: Steady-state behavior Halvorsen, Ivar J. Skogestad, Sigurd The "Petlyuk" or "dividing-wall" or "fully thermally coupled" distillation column is an interesting alternative to the conventional cascaded binary columns for separation of multi-component mixtures. However, the industrial use has been limited, and difficulties in operation have been reported as one reason. With three product compositions controlled, the system has two degrees of freedom left for on-line optimization. We show that the steady-state optimal solution surface is quite narrow, and depends strongly on disturbances and design parameters. Thus it seems difficult to achieve the potential energy savings compared to conventional approaches without a good control strategy. We discuss candidate variables which may be used as feedback variables in order to keep the column operation close to optimal in a "self-optimizing" control scheme. self optimizing control,

oai:mic.2001.4.1 2010-03-20

eng Journal article 2001-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2001-4-1.asp Fulltext http://www.mic-journal.no/PDF/2001/MIC-2001-4-1.pdf Modelling and Simulation of Variable Speed Thruster Drives with Full-Scale Verification Hansen, Jan F. Lauvdal, Trygve Ådnanes, Alf K. In this paper considerations about modelling and simulation of variable speed thruster drives are made with comparison to full scale measurements from Varg FPSO. For special purpose vessels with electric propulsion operating in DP (Dynamic Positioning) mode the thruster drives are essential for the vessel operation. Different model strategies of thruster drives are discussed. An advanced thruster drive model with a dynamic motor model and field vector control principle is shown. Simulations are performed with both the advanced model and a simplified model. These are compared with full-scale measurements from Varg FPSO. The simulation results correspond well with the measurements, for both the simplified model and the advanced model. Marine systems, modelling, simulation, verification, electrical machines,

oai:mic.2001.4.2 2010-03-20

eng Journal article 2001-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2001-4-2.asp Fulltext http://www.mic-journal.no/PDF/2001/MIC-2001-4-2.pdf Piecewise affine observer-based robust controllers for constrained nonlinear systems Imsland, Lars Slupphaug, Olav Foss, Bjarne A. For a general class of constrained uncertain nonlinear discrete-time systems, and a general class of observers, it is developed bilinear matrix inequalities whose solution gives gain matrices used in a piecewise afline observer/controller structure. The closed-loop system is robustly quadratically stable with a region of attraction larger than a prescribed ellipsoidal region. It is also developed a second-order algorithm for solving these inequalities locally. output feedback, robust nonlinear control, observer design, constrained systems,

oai:mic.2001.4.3 2010-03-20

eng Journal article 2001-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2001-4-3.asp Fulltext http://www.mic-journal.no/PDF/2001/MIC-2001-4-3.pdf Bayesian 2D Deconvolution: A Model for Diffuse Ultrasound Scattering Husby, Oddvar Lie, Torgrim Langø, Thomas Hokland, Jørn Rue, Håvard Observed medical ultrasound images are degraded representations of the true acoustic tissue reflectance. The degradation is due to blur and speckle, and significantly reduces the diagnostic value of the images. In order to remove both blur and speckle we have developed a new statistical model for diffuse scattering in 2D ultrasound radio-frequency images, incorporating both spatial smoothness constraints and a physical model for diffuse scattering. The modeling approach is Bayesian in nature, and we use Markov chain Monte Carlo methods to obtain the restorations. The results from restorations of some real and simulated radio-frequency ultrasound images are presented and compared with results produced by Wiener filtering. Medical ultrasound, restoration, Markov random fields, diffuse scattering,

oai:mic.2001.4.4 2010-03-20

eng Journal article 2001-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2001-4-4.asp Fulltext http://www.mic-journal.no/PDF/2001/MIC-2001-4-4.pdf Linear MPC with Optimal Prioritized Infeasibility Handling: Application, Computational Issues and Stability Vada, Jostein Slupphaug, Olav Johansen, Tor A. Foss, Bjarne A. All practical MPC implementations should have a means to recover from infeasibility. We present a recently developed infeasibility handler which computes optimal relaxations of the relaxable constraints subject to a user-defined prioritization, by solving only a single linear program on-line in addition to the standard quadratic programming problem on-line. A stability result for this infeasibility handler combined with the Rawlings-Muske MPC controller is provided, and various practical and computational issues are discussed. From a simulated FCCU main fractionator case study, we conclude that the proposed strategy for designing the proposed infeasibility handler is applicable on problems of realistic size.

oai:mic.2002.1.1 2010-03-20

eng Journal article 2002-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2002-1-1.asp Fulltext http://www.mic-journal.no/PDF/2002/MIC-2002-1-1.pdf Fluid Flow Simulations of a Vane Separator Jøsang, Aage I. Melaaen, Morten Chr. In this work, the fluid flow in a vane separator is simulated by Computational Fluid Dynamics (CFD). Detailed measurements of air flow inside a single passage in a vane separator have earlier been presented (Josang and Melaaen 2000). The simulations cover various turbulence models (k-epsilon and RSM turbulence models), near wall treatments, numerical schemes and structured grid as well as un-structured grid simulations. Earlier simulations show that a proper matching between the grid and the near wall treatment is important. However, most important is the effect of the two different numerical schemes together with the turbulence models. The selected numerical schemes are two different first order schemes (the power law scheme and the first order upwind scheme) and the higher order QUICK scheme. Normally, the highest order scheme is asssumed to produce the most accurate result, but in the present work the combination of the best turbulence model (RSM) and QUICK gave the worst result. Most of the other combinations gave good predicted flow fields, although some deviations exist for the prediction of the recirculation zones. CFD, vanes, measurement, verification,

oai:mic.2002.1.2 2010-03-20

eng Journal article 2002-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2002-1-2.asp Fulltext http://www.mic-journal.no/PDF/2002/MIC-2002-1-2.pdf Paper Machine Modeling at Norske Skog Saugbrugs: A Mechanistic Approach Hauge, Tor A. Lie, Bernt In this paper a mechanistic model of a paper machine is presented. The model is developed as a foundation for the control of three selected variables; the basis weight, the paper ash content, and the white water total concentration (or wire tray total concentration). The model is of high order and reduced order models are developed and fitted to experimental and operational mill data. The fitted models are validated with historical operational data. Paper machine, mechanistic model, model reduction,

oai:mic.2002.1.3 2010-03-20

eng Journal article 2002-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2002-1-3.asp Fulltext http://www.mic-journal.no/PDF/2002/MIC-2002-1-3.pdf A Computational and Experimental Study of Fluid Flow in a De-duster Wang, Qianpu Melaaen, Morten Chr. de Silva, Sunil R. A three-dimensional computational fluid dynamics model with an RNG k-epsilon model and second upwind scheme in the Fluent package was used to simulate the flowpattern in a de-duster. The model predictions for the flow field inside the dispersion device were compared with LDA measurements. The primary objectives are to understand such complex flow fields and to guide the development and optimisation of this de-duster. CFD, air classifier. de-dusting,

oai:mic.2002.2.1 2010-03-20

eng Journal article 2002-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2002-2-1.asp Fulltext http://www.mic-journal.no/PDF/2002/MIC-2002-2-1.pdf Multi-phase Flow Modeling applied to Metallurgical Processes Johansen, Stein T. Multiphase flow models have been improved significantly during the last two decades. Together with the development of more advanced numerical techniques and faster and cheaper computers we now see that computational fluid dynamics (CFD) becomes a powerful tool in predicting the performance of complex industrial processes. In particular the processes faced by the metallurgical industries may serve as examples of such complexity. Multi-phase, multi-scale, flow modeling, metallurgy, dispersed systems, interface tracking,

oai:mic.2002.2.2 2010-03-20

eng Journal article 2002-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2002-2-2.asp Fulltext http://www.mic-journal.no/PDF/2002/MIC-2002-2-2.pdf Simulation of a Hydrometallurgical Leaching Reactor modeled as a DAE system Duenas Diez, Marta Ausland, G. Fjeld, M. Lie, Bernt An existing dynamic model of the main reactor in the Silgrain process for the production of Si from FeSi has been extended here in order to resemble more closely the behavior of the real reactor. The previous model was based on the application of macroscopic mass conservation law, the population balance equation and the assumptions of complete mixing and isothermic conditions. The major modifications are the inclusion of the condition governing the entrainment of particles in the outflow, and the formulation of the energy balance. The extended model consists of 1 integrodifferential equation, 4 implicit ordinary differential equations, 7 algebraic equations and 3 integral equations. After discretization in the particle size space, a system of differential and algebraic equations (DAE) is obtained. DAEs are not ODEs and they require analysis and characterization and may require reformulation. After such analysis, it was concluded that the system is implicit index-one for the usual range of operation and that a method based on the Backward Differentiation formulas (BDF) can be used for its solution. The model was implemented in Matlab and the ode15s code was used for solving the system of equations. The simulation results are satisfactory and seem to match qualitatively with the known operation of the reactor. The model is suitable for further use in designing a model-based control scheme. Population Balance Equation, Differential and Algebraic Equations, leaching, dynamic modeling,

oai:mic.2002.2.3 2010-03-20

eng Journal article 2002-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2002-2-3.asp Fulltext http://www.mic-journal.no/PDF/2002/MIC-2002-2-3.pdf Modeling and Simulation of a lab-scale Fluidised Bed Halvorsen, Britt Mathiesen, Vidar The flow behaviour of a lab-scale fluidised bed with a central jet has been simulated. The study has been performed with an in-house computational fluid dynamics (CFD) model named FLOTRACS-MP-3D. The CFD model is based on a multi-fluid Eulerian description of the phases, where the kinetic theory for granular flow forms the basis for turbulence modelling of the solid phases. A two-dimensional Cartesian co-ordinate system is used to describe the geometry. This paper discusses whether bubble formation and bed height are influenced by coefficient of restitution, drag model and number of solid phases. Measurements of the same fluidised bed with a digital video camera are performed. Computational results are compared with the experimental results, and the discrepancies are discussed. CFD, gas/particle flow, bubble formation,

oai:mic.2002.2.4 2010-03-20

eng Journal article 2002-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2002-2-4.asp Fulltext http://www.mic-journal.no/PDF/2002/MIC-2002-2-4.pdf One-Dimensional Simulation of Clay Drying Siljan, Siljan Melaaen, Morten Chr Drying of clay is simulated by a one-dimensional model. The background of the work is to form a better basis for investigation of the drying process in production of clay-based building materials. A model of one-dimensional heat and mass transfer in porous material is used and modified to simulate drying of clay particles. The convective terms are discretized by first-order upwinding, and the diffusive terms are discretized by central differencing. DASSL was used to solve the set of algebraic and differential equations. The different simulations show the effect of permeability, initial moisture content and different boundary conditions. Both drying of a flat plate and a spherical particle are modelled. Clay, drying, simulation, LECA, LWA, porous,

oai:mic.2002.3.1 2010-03-20

eng Journal article 2002-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2002-3-1.asp Fulltext http://www.mic-journal.no/PDF/2002/MIC-2002-3-1.pdf Tutorial on Feedback Control of Flows, Part I: Stabilization of Fluid Flows in Channels and Pipes Aamo, Ole M. Fossen, Thor I. The field of flow control has picked up pace over the past decade or so, on the promise of real-time distributed control on turbulent scales being realizable in the near future. This promise is due to the micromachining technology that emerged in the 1980s and developed at an amazing speed through the 1990s. In lab experiments, so called micro-electro-mechanical systems (MEMS) that incorporate the entire detection-decision-actuation process on a single chip, have been batch processed in large numbers and assembled into flexible skins for gluing onto body-fluid interfaces for drag reduction purposes. Control of fluid flows span a wide variety of specialities. In Part I of this tutorial, we focus on the problem of reducing drag in channel and pipe flows by stabilizing the parabolic equilibrium profile using boundary feedback control. The control strategics used for this problem include classical control, based on the Nyquist criteria, and various optimal control techniques (H2, H-Infinity), as well as applications of Lyapunov stability theory. Flow control stabilization,

oai:mic.2002.4.1 2010-03-20

eng Journal article 2002-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2002-4-1.asp Fulltext http://www.mic-journal.no/PDF/2002/MIC-2002-4-1.pdf Passivity Analysis of Nonlinear Euler-Bernoulli Beams Fard, Mehrdad P. The Lagrangian equations for distributed-parameter systems based on Hamilton's principle are developed. These equations are subsequently used to derive nonlinear models for beams. The passivity properties of the flexible mechanical systems based on their distributed-parameter models are then investigated and direct output feedback control laws for control purposes are proposed. Finite gain L2 stability and passivity of closed-loop systems are proven. Illustrative cases with simulation of the nonlinear beams and stabilizing feedback control laws are included in the text. Vibration control, distributed parameter systems,

oai:mic.2002.4.2 2010-03-20

eng Journal article 2002-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2002-4-2.asp Fulltext http://www.mic-journal.no/PDF/2002/MIC-2002-4-2.pdf Noise Handling Capabilities of Multivariate Calibration Methods Ergon, Rolf The noise handling capabilities of principal component regression (PCR) and partial least squares regression (PLSR) are somewhat disputed issues, especially regarding regressor noise. In an attempt to indicate an answer to the question, this article presents results from Monte Carlo simulations assuming a multivariate mixing problem with spectroscopic data. Comparisons with the best linear unbiased estimator (BLUE) based on Kalman filtering theory are included. The simulations indicate that both PCR and PLSR perform comparatively well even at a considerable regressor noise level. The results are also discussed in relation to estimation of pure spectra for the mixing constituents, i.e. to identification of the data generating system. In this respect solutions to well-posed least squares problems serve as references. PCR, PLSR, noise, prediction,

oai:mic.2002.4.3 2010-03-20

eng Journal article 2002-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2002-4-3.asp Fulltext http://www.mic-journal.no/PDF/2002/MIC-2002-4-3.pdf Tutorial on Feedback Control of Flows, Part II: Diagnostics and Feedback Control of Mixing Aamo, Ole M. Fossen, Thor I. Control of fluid flows span a wide variety of specialities. In Part II of this tutorial, we focus on diagnostics of mixing and the problem of enhancing mixing by boundary feedback control. Diagnostic tools from dynamical systems theory are presented that enable detection and quantification of chaotic transport in periodically perturbed systems. However, real systems are generally not periodic, and available measurements or simulations are finite in time. A method for quantifying mixing in finite-time velocity fields is discussed, and applied to data obtained from simulations of the 2D controlled channel flow. Mixing has traditionally been brought on by open-loop control strategies, such as stirring, jet injection or mixing valves. Applications of active feedback to mixing problems are scarce in the literature, but the idea is currently drawing attention from various research groups. Feedback laws for the purpose of mixing enhancement in 2D and 3D pipe flow are presented, and simulations show that they induce strong mixing. Flow control, feedback,

oai:mic.2003.1.1 2010-03-20

eng Journal article 2003-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2003-1-1.asp Fulltext http://www.mic-journal.no/PDF/2003/MIC-2003-1-1.pdf Wave Detection and Characterization from Current and Voltage Signals of an Aluminium Smelting Cell Solberg, Ingar In aluminium electrolysis cell there is a layer of 10-20 cm of liquid aluminium. On top of this there is a layer of a melted salt electrolyte with a number of carbon anode blocks partially submerged. The density difference of the two liquids is small and low frequency waves can occur in the interface. The waves cause variation in the current distribution between the individual anode carbon blocks. These variations are in this article analysed and visualised with MATLAB to show information of the temporal variations, frequencies and spatial modes of the waves. Wave analysis, aluminium production, signal processing, visualisation, anode current,

oai:mic.2003.1.2 2010-03-20

eng Journal article 2003-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2003-1-2.asp Fulltext http://www.mic-journal.no/PDF/2003/MIC-2003-1-2.pdf The Ski Base Structure Analyser (SSA) Moldestad, Dag A. Løset, Sveinung A Ski base Structure Analyser (SSA) utilising laser technology has been developed to analyse the detailed structure of a stone-ground ski base. The SSA displays the measured surface as an image with 739 x 570 pixels, where each pixel can have a grey level value from 0 to 255. The value of each pixel is proportional to the height at the corresponding point of the measured surface. Various roughness parameters can be calculated from the measured surface image in order to characterise the surface topography. Some of these parameters are described in this paper. Further the paper contains examples of calculated SSA parameters from a typically measured surface image using MATLAB. Image processing, tribology, roughness, ski,

oai:mic.2003.1.3 2010-03-20

eng Journal article 2003-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2003-1-3.asp Fulltext http://www.mic-journal.no/PDF/2003/MIC-2003-1-3.pdf Modeling Logic Systems with Structured Array-based Logic Hussein, Bassam Davidrajuh, Reggie First this paper introduces an efficient tool called array-based logic for modeling complex logic systems. The main concepts of array-based logic are explained. Second, the logic functions of this tool are presented with the help of six definitions. Finally, an application example on manufacturing system is worked out. Array-based logic, logic modeling,

oai:mic.2003.1.4 2010-03-20

eng Journal article 2003-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2003-1-4.asp Fulltext http://www.mic-journal.no/PDF/2003/MIC-2003-1-4.pdf Storfjorden (Svalbard): Modeling of the Polynya Development and the Sea Ice Ridging Process Zyryanov, Denis Haarpaintner, Jörg Korsnes, Reinert Remote sensing observations of Storfjorden ice cover described the persistence and evolution of latent heat polynyas during winter 1997/1998. The induced important ice production was quantitatively estimated by simple modeling of the sea ice dynamics and growth. In the present work we used mathematical modeling to qualitatively simulate the polynya open and developing. First, we estimate the values of internal stresses appeared in Storfjorden ice sheet due to the wind stress and used them in the model calibration algorithm. Then, we model the polynya open and developing in simple quasi-static approach. The sea ice ridging process is modeled last and the maximum of ice ridges height is estimated. The results of the simulations are compared to satellite observations from ERS-2. They show that the equilibrium stages of the model developing coincide in common with in-situ data of satellite observations. From another side, the estimations show that the ice ridge keel can achieve height up to 8m along the eastern shore of Spitsbergen. Plasticity sea ice,

oai:mic.2003.1.5 2010-03-20

eng Journal article 2003-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2003-1-5.asp Fulltext http://www.mic-journal.no/PDF/2003/MIC-2003-1-5.pdf Utilizing MATPOWER in Optimal Power Flow Kristiansen, Tarjei This paper shows how MATPOWER, a MATLAB Power System Simulation Package can be used for optimal power flow (OPF) simulations. MATPOWER is a package of MATLAB files for solving power flow and optimal power flow problems. It is a simulation tool for researchers and educators which is easy to use and modify. An OPF simulation gives the active/reactive power generated and purchased at each bus and the nodal prices. The nodal prices are of special interest because they reflect the marginal generation and load at each bus (node). These prices are also called locational prices and are found to be the optimal prices, maximizing social welfare and taking transmission constraints into account. They can provide the right incentives to market players and to society. When transmission congestion is present this creates market inefficiency, since cheap distant generation may be replaced with more expensive local generation. We are especially interested in OPF as utilized by a centralized dispatcher, and we also describe the features relevant for the Norwegian and Nordic markets. We optimize three cases and analyze the economic consequences of different network topologies and transmission congestion. MATPOWER, optimal power flow, nodal prices,

oai:mic.2003.2.1 2010-03-20

eng Journal article 2003-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2003-2-1.asp Fulltext http://www.mic-journal.no/PDF/2003/MIC-2003-2-1.pdf Analysis of Vortex Induced Vibrations of Marine Risers Kaasen, Karl E. Lie, Halvor Vortex induced vibrations (VIV) can be a severe problem to marine risers with regard to fatigue damage and drag loading. In order to design marine risers, therefore, it is necessary to have good theoretical and numerical models for prediction of VIV. Full-scale data are needed for verification of the models. To this end, three drilling risers were instrumented with accelerometers and rotation-rate devices for measurement of VIV. Also, sea current was measured at number of depths for reference. A large quantity of data was collected during the time the instrument system was in operation. In order to choose data records for further investigation and comparison with theoretical models the raw data had to be conditioned and converted to a suitable form. The paper describes how the riser lateral displacements were derived from the measurements. A major task has been to rid the acceleration measurements of the influence of gravity due to the riser's rotations out of the vertical and include the measurements of angular motion in a consistent way. This has been done using modal decomposition and a least-squares method combined with frequency-domain calculation to estimate the modal weights. MATLAB was used for the calculations and the presentation of results. An example of results is given. Vortex Induced Vibration. Marine Risers, Modal Analysis, Least Squares Estimation,

oai:mic.2003.2.2 2010-03-20

eng Journal article 2003-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2003-2-2.asp Fulltext http://www.mic-journal.no/PDF/2003/MIC-2003-2-2.pdf Fusion of Radar Tracks, Reports and Plans Mevassvik, O. M. Løkka, A. This paper suggests a method that utilizes non-real time information as an aid to improve maritime surveillance. Under certain conditions vessels move in accordance with preplanned routes and possibly also report their own position at certain positions or at certain times during the voyage. The method proposed consists of a statistical route model that describes the movement of the vessel, and includes refinement of the estimated movement based upon reports on the vessel. The estimated movement is then associated with radar tracks using multiple hypothesis techniques. This is due to the fact that the number of vessels with known route plans is small compared to the total number of vessels in an area. The associated radar tracks are also used to improve the estimated movement of the vessels. The problem of generating possible solutions and selecting the best hypothesis is formulated as a constraint satisfaction problem and implemented using a constraint programming technique. Maritime surveillance, multiple hypothesis testing,

oai:mic.2003.2.3 2010-03-20

eng Journal article 2003-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2003-2-3.asp Fulltext http://www.mic-journal.no/PDF/2003/MIC-2003-2-3.pdf Dynamic Optimization and Production Planning of Thermal Cracking Operation Edwin, Emil H. Balchen, Jens G. This work addresses the dynamic optimization of the production period of thermal crackers with respect to coke formation in the cracking coil and transfer line exchanger. Optimal time dependent trajectories of feed rate, steam to hydrocarbon ratio, and reaction severity are calculated. The net earnings based on the price of hydrocarbons, kid, steam, decoking, and maintenance cost are maximized. All important operational constraints are included and the optimization problem is solved using parameterized free variable trajectories (piece wise constant) and a standard SQP package. Rigorous distributed physical models are used and calculation show that dynamic optimization gives up to 2( earnings - expenses) than conventional steady state optimization performed on the same models. This is in the same range as earnings reported from steady state optimization implementations alone. Steam cracker, coke, dynamic simulation, modelling, economics,

oai:mic.2003.3.1 2010-03-20

eng Journal article 2003-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2003-3-1.asp Fulltext http://www.mic-journal.no/PDF/2003/MIC-2003-3-1.pdf Subspace System Identification of the Kalman Filter Di Ruscio, David Some proofs concerning a subspace identification algorithm are presented. It is proved that the Kalman filter gain and the noise innovations process can be identified directly from known input and output data without explicitly solving the Riccati equation. Furthermore, it is in general and for colored inputs, proved that the subspace identification of the states only is possible if the deterministic part of the system is known or identified beforehand. However, if the inputs are white, then, it is proved that the states can be identified directly. Some alternative projection matrices which can be used to compute the extended observability matrix directly from the data are presented. Furthermore, an efficient method for computing the deterministic part of the system is presented. The closed loop subspace identification problem is also addressed and it is shown that this problem is solved and unbiased estimates are obtained by simply including a filter in the feedback. Furthermore, an algorithm for consistent closed loop subspace estimation is presented. This algorithm is using the controller parameters in order to overcome the bias problem. Identification methods, Subspace methods Stochastic systems, Sampled data systems,

oai:mic.2003.3.2 2010-03-20

eng Journal article 2003-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2003-3-2.asp Fulltext http://www.mic-journal.no/PDF/2003/MIC-2003-3-2.pdf A Global Remote Laboratory Experimentation Network and the Experiment Service Provider Business Model and Plans Eikaas, Tor Ivar Schmid, Christian Foss, Bjarne A. Gillet, Denis This paper presents results from the IST KAII Trial project ReLAX - Remote LAboratory eXperimentation trial (IST 1999-20827), and contributes with a framework for a global remote laboratory experimentation network supported by a new business model. The paper presents this new Experiment Service Provider business model that aims at bringing physical experimentation back into the learning arena, where remotely operable laboratory experiments used in advanced education and training schemes are made available to a global education and training market in industry and academia. The business model is based on an approach where individual experiment owners offer remote access to their high-quality laboratory facilities to users around the world. The usage can be for research, education, on-the-job training etc. The access to these facilities is offered via an independent operating company - the Experiment Service Provider. The Experiment Service Provider offers eCommerce services like booking, access control, invoicing, dispute resolution, quality control, customer evaluation services and a unified Lab Portal. Remote experimentation, education, training,

oai:mic.2003.3.3 2010-03-20

eng Journal article 2003-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2003-3-3.asp Fulltext http://www.mic-journal.no/PDF/2003/MIC-2003-3-3.pdf Output Feedback Stabilization with Nonlinear Predictive Control: Asymptotic properties Imsland, Lars Findeisen, Rolf Allgöwer, Frank Foss, Bjarne A. State space based nonlinear model predictive control (NM PC) needs the state for the prediction of the system behaviour. Unfortunately, for most applications, not all states are directly measurable. To recover the unmeasured states, typically a stable state observer is used. However, this implies that the stability of the closed-loop should be examined carefully, since no general nonlinear separation principle exists. Recently semi-global practical stability results for output feedback NMPC using a high-gain observer for state estimation have been established. One drawback of this result is that (in general) the observer gain must be increased, if the desired set the state should converge to is made smaller. We show that under slightly stronger assumptions, not only practical stability, but also convergence of the system states and observer error to the origin for a sufficiently large but bounded observer gain can be achieved. nonlinear model, predictive control, output feedback, high-gain observers,

oai:mic.2003.4.1 2010-03-20

eng Journal article 2003-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2003-4-1.asp Fulltext http://www.mic-journal.no/PDF/2003/MIC-2003-4-1.pdf Control of the Amplitude in a Surging Balling Drum Circuit, a New Approach to an Old Problem Rapp, Knut Nyman, Per-Ole In this paper we suggest a new method for controlling the balling drums used in the iron ore industry. We suggest that a cluster of drums are controlled collectively rather than individually. Further, we investigate the possibility of using an extended Kalman filter for estimating the amplitude and frequency of the oscillations in such drums. The filters thresholding point is identified, and the area for which the filter is usable is given. Finally a simulation of the proposed control scheme, based on a simple nonlinear model, is presented. Balling drums, surging, estimation, extended Kalman filter,

oai:mic.2003.4.2 2010-03-20

eng Journal article 2003-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2003-4-2.asp Fulltext http://www.mic-journal.no/PDF/2003/MIC-2003-4-2.pdf The Impact of Varying Conductivity on the Control of Aluminium Electrolysis Cells Drengstig, Tormod Kolås, Steinar Støre, Trond In this paper we investigate from a theoretical point of view the impact of varying bath temperature, excess AlF3 and alumina concentration on cell resistance and cell control. The results are interpreted using knowledge of the behavior of general resistance and anode beam controllers to study the influence on the anode cathode distance. This again leads to the proposal of a new control strategy for bath temperature and excess AlF3. The theoretical results obtained are supported using real data. Aluminium electrolysis, excess AlF3, control,

oai:mic.2003.4.3 2010-03-20

eng Journal article 2003-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2003-4-3.asp Fulltext http://www.mic-journal.no/PDF/2003/MIC-2003-4-3.pdf Adaptive Tracking Control of an Electro-Pneumatic Clutch Actuator Kaasa, Glenn-Ole Takahashi, Masanori This paper deals with the application of a simple adaptive algorithm for robust tracking control of an electro-pneumatic clutch actuator with output feedback. We present a mathematical model of the strongly nonlinear system, and implement an adaptive algorithm, based on a parallel feedforward compensator (PFC) to remove the relative-degree-1 restriction. We propose a practical method of constructing the PFC, and introduce a simple modification that removes an inherent restriction on bandwidth of the nonlinear system. We show that the adaptive algorithm deals well with nonlinearities, and we achieve tracking corresponding to a settling-time of 150 ms. adaptive tracking control, high-gain feedback,

oai:mic.2003.4.4 2010-03-20

eng Journal article 2003-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2003-4-4.asp Fulltext http://www.mic-journal.no/PDF/2003/MIC-2003-4-4.pdf State Space Realization of Model Predictive Controllers Without Active Constraints Skogestad, Sigurd Faanes, Audun To enable the use of traditional tools for analysis of multivariable controllers such as model predictive control (MPC), we develop a state space formulation for the resulting controller for MPC without constraints or assuming that the constraints are not active. Such a derivation was not found in the literature. The formulation includes a state estimator. The MPC algorithm used is a receding horizon controller with infinite horizon based on a state space process model. When no constraints are active, we obtain a state feedback controller, which is modified to achieve either output tracking, or a combination of input and output tracking. When the states are not available, they need to be estimated from the measurements. It is often recommended to achieve integral action in a MPC by estimating input disturbances and include their effect in the model. We show that to obtain offset free steady state the number of estimated disturbances must equal the number of measurements. The estimator is included in the controller equation, and we obtain a formulation of the overall controller with the set-points and measurements as inputs, and the manipulated variables as outputs. One application of the state space formulation is in combination with the process model to obtain a closed loop model. This can for example be used to check the steady-state solution and see whether integral action is obtained or not. MPC, reference tracking, state estimation,

oai:mic.2004.1.1 2010-03-20

eng Journal article 2004-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2004-1-1.asp Fulltext http://www.mic-journal.no/PDF/2004/MIC-2004-1-1.pdf A Nonlinear Ship Manoeuvering Model: Identification and adaptive control with experiments for a model ship Skjetne, Roger Smogeli, Øyvind N. Fossen, Thor I. Complete nonlinear dynamic manoeuvering models of ships, with numerical values, are hard to find in the literature. This paper presents a modeling, identification, and control design where the objective is to manoeuver a ship along desired paths at different velocities. Material from a variety of references have been used to describe the ship model, its difficulties, limitations, and possible simplifications for the purpose of automatic control design. The numerical values of the parameters in the model is identified in towing tests and adaptive manoeuvering experiments for a small ship in a marine control laboratory. Ship control; manoeuvering; nonlinear ship model; system identification,

oai:mic.2004.1.2 2010-03-20

eng Journal article 2004-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2004-1-2.asp Fulltext http://www.mic-journal.no/PDF/2004/MIC-2004-1-2.pdf Wave Synchronizing Crane Control during Water Entry in Offshore Moonpool Operations - Experimental Results Johansen, Tor A. Fossen, Thor I. Sagatun, Svein I. Nielsen, Finn G. A new strategy for active control in heavy-lift offshore crane operations is suggested, by introducing a new concept referred to as wave synchronization. Wave synchronization reduces the hydrodynamic forces by minimization of variations in the relative vertical velocity between payload and water using a wave amplitude measurement. Wave synchronization is combined with conventional active heave compensation to obtain accurate control. Experimental results using a scale model of a semi-submerged vessel with a moonpool shows that wave synchronization leads to significant improvements in performance. Depending on the sea state and payload, the results indicate that the reduction in the standard deviation of the wire tension may be up to 50 crane control,

oai:mic.2004.1.3 2010-03-20

eng Journal article 2004-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2004-1-3.asp Fulltext http://www.mic-journal.no/PDF/2004/MIC-2004-1-3.pdf On the Computation of Disturbance Rejection Measures Hovd, Morten Ma, David L. Braatz, Richard D. In any process plant design, a central question is whether it is possible to achieve acceptable control with the available manipulated variables, while taking into account the disturbances that can be expected. Some little known controllability measures have been proposed to address such issues (Wolff, 1994; Skogestad and Wolff, 1992). The main reason these controllability measures have received little attention is probably that, while, their mathematical formulation was defined, no algorithms were provided to solve the mathematical problems. This paper shows how to calculate these controllability measures, and applies the algorithms to some process examples.

oai:mic.2004.2.1 2010-03-20

eng Journal article 2004-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2004-2-1.asp Fulltext http://www.mic-journal.no/PDF/2004/MIC-2004-2-1.pdf Handling State and Output Constraints in MPC Using Time-dependent Weights Hovd, Morten Braatz, Richard D. A popular method for handling state and output constraints in a model predictive control (MPC) algorithm is to use 'soft constraints', in which penalty terms are added directly to the objective function. Improved closed loop performance can be obtained for plants with nontninimum phase zeros by modifying the MPC formulation to include suitably-designed time-dependent weights on the penalty terms associated with the state and output constraints. When the penalty terms are written in terms of the 'worst-ease' l-infinity norm, incorporating the appropriate time dependence into the weights provides much better closed loop performance. The approach is illustrated using two multivariable plants with nonminimum phase transmission zeros, where the time-dependent weights cause the open loop predictions to coincide with closed loop predictions, which results in a reduction of output constraint violations.

oai:mic.2004.2.2 2010-03-20

eng Journal article 2004-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2004-2-2.asp Fulltext http://www.mic-journal.no/PDF/2004/MIC-2004-2-2.pdf Simple analytic rules for model reduction and PID controller tuning Skogestad, Sigurd The aim of this paper is to present analytic rules for PID controller tuning that are simple and still result in good closed-loop behavior. The starting point has been the IMC-PID tuning rules that have achieved widespread industrial acceptance. The rule for the integral term has been modified to improve disturbance rejection for integrating processes. Furthermore, rather than deriving separate rules for each transfer function model, there is a just a single tuning rule for a first-order or second-order time delay model. Simple analytic rules for model reduction are presented to obtain a model in this form, including the 'half rule' for obtaining the effective time delay. Process control. feedback control, IMC, PI-control, integrating process,

oai:mic.2004.3.1 2010-03-20

eng Journal article 2004-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2004-3-1.asp Fulltext http://www.mic-journal.no/PDF/2004/MIC-2004-3-1.pdf Explicit Approaches to Constrained Model Predictive Control: A Survey Grancharova, Alexandra Johansen, Tor A. This paper presents a review of the explicit approaches to constrained model predictive control. The main motivation behind the explicit solution is that it avoids the need for real-time optimization, and thus allows implementation at high sampling frequencies in real-time systems with high reliability and low software complexity. The paper is organized as follows. Section 1 includes formulation of the constrained linear quadratic regulation (LQR) problem, summary of the implicit approaches, and the basics of the model predictive control (MPC). Sections 2 and 3 consider respectively the exact and the approximate approaches to explicit solution of constrained MPC problems, together with several examples. Model predictive control, constraints, multi-parametric quadratic programming,

oai:mic.2004.3.2 2010-03-20

eng Journal article 2004-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2004-3-2.asp Fulltext http://www.mic-journal.no/PDF/2004/MIC-2004-3-2.pdf Nonlinear Observer Design for a Nonlinear Cable/String FEM Model using Contraction Theory Türkyilmaz, Yilmaz Egeland, Olav Contraction theory is a recently developed nonlinear analysis tool which may be useful for solving a variety of nonlinear control problems. In this paper, using Contraction theory, a nonlinear observer is designed for a general nonlinear cable/ string FEM (Finite Element Method) model. The cable model is presented in the form of partial differential equations (PDE). Galerkin's method is then applied to obtain a set of ordinary differential equations such that the cable model is approximated by a FEM model. Based on the FEM model, a nonlinear observer is designed to estimate the cable configuration. It is shown that the estimated configuration converges exponentially to the actual configuration. Numerical results and simulations are shown to be in agreement with the theoretical results. Cables, nonlinear models, finite element method, observers,

oai:mic.2004.3.3 2010-03-20

eng Journal article 2004-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2004-3-3.asp Fulltext http://www.mic-journal.no/PDF/2004/MIC-2004-3-3.pdf A Toolbox of Aiding Techniques for the HUGIN AUV Integrated Inertial Navigation System Jalving, Bjørn Gade, Kenneth Hagen, Ove K. Vestgård, Karsten Modern AUV designs must handle submerged autonomous operation for long periods of time. The state of the art solution embedded in the HUGIN AUVs is a Doppler Velocity Log (DVL) aided Inertial Navigation System (INS) that can integrate various forms of position measurement updates. In autonomous operations, position updates are only available in limited periods of time or space, thus the core velocity aided inertial navigation system must exhibit high accuracy However, position uncertainty of a DVL aided inertial navigation system will eventually drift off, compromising either mission operation or requirements for accurate positioning of payload data. To meet the requirements for a range of military and civilian AUV applications, the HUGIN vehicles come with a flexible and powerful set of navigation techniques. Methods for position updates include GPS surface fix, DGPS-USBL, Underwater Transponder Positioning (UTP) and bathymetric terrain navigation. Based on synthetic aperture sonar technology, a potentially revolutionary accurate velocity measurement is under development. HUGIN also comes with a navigation post-processing system (NavLab), which can be applied to increase navigational integrity and maximize position accuracy. Autonomous underwater vehicle, aided inertial navigation, Kalman filter, Doppler velocity log, synthetic aperture sonar, GPS. USBL, transponder navigation,

oai:mic.2004.4.1 2010-03-20

eng Journal article 2004-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2004-4-1.asp Fulltext http://www.mic-journal.no/PDF/2004/MIC-2004-4-1.pdf Nonlinear Time-Domain Strip Theory Formulation for Low-Speed Manoeuvering and Station-Keeping Fossen, Thor I. Smogeli, Øyvind N. This paper presents a computer effective nonlinear time-domain strip theory formulation for dynamic positioning (DP) and low-speed manoeuvring. Strip theory or 2D potential theory, where the ship is divided in 20 to 30 cross sections, can be used to compute the potential coefficients (added mass and potential damping) and the exciting wave loads (Froude-Krylov and diffraction forces). Commercially available programs are ShipX (VERES) by Marintek (Fathi, 2004) and SEAWAY by Amarcon (Journée & Adegeest, 2003), for instance. The proposed method can easily be extended to utilize other strip theory formulations or 3-D potential programs like WAMIT (2004). The frequency dependent potential damping, which in classic theory results in a convolution integral not suited for real-time simulation, is compactly represented by using the state-space formulation of Kristiansen & Egeland (2003). The separation of the vessel model into a low-frequency model (represented by zerofrequency added mass and damping) and a wave-frequency model (represented by motion transfer functions or RAOs), which is commonly used for simulation, is hence made superfluous. Transformations of motions and coefficients between different coordinate systems and origins, i.e. data frame, hydrodynamic frame, body frame, inertial frame etc., are put into the rigid framework of Fossen (1994, 2002). The kinematic equations of motion are formulated in a compact nonlinear vector representation and the classical kinematic assumption that the Euler angles are small is removed. This is important for computation of accurate control forces at higher roll and pitch angles. The hydrodynamic forces in the steadily translating hydrodynamic reference frame (equilibrium axes) are, however, assumed tobe linear. Recipes for computation of retardation functions are presented and frequency dependent viscous damping is included. Emphasis is placed on numerical computations and representation of the data from VERES and SEAWAY in Matlab/Simulink. For this purpose a Simulink add-in to the Marine Systems Simulator (MSS) at the Norwegian University of Science and Technology has been developed (Fossen et al., 2004). Ship, rig, modeling, strip theory,

oai:mic.2004.4.2 2010-03-20

eng Journal article 2004-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2004-4-2.asp Fulltext http://www.mic-journal.no/PDF/2004/MIC-2004-4-2.pdf DVL Velocity Aiding in the HUGIN 1000 Integrated Inertial Navigation System Jalving, Bjørn Gade, Kenneth Svartveit, Kristian Willumsen, Are Sørhagen, Robert The RDI WHN-600 Doppler Velocity Log (DVL) is a key navigation sensor for the HUG1N 1000 Autonomous Underwater Vehicle (AUV). HUGIN 1000 is designed for autonomous submerged operation for long periods of time. This is facilitated by a low drift velocity aided Inertial Navigation System (INS). Major factors determining the position error growth are the IMU and DVL error characteristics and the mission plan pattern_ For instance, low frequency DVL errors cause an approximately linear drift in a straight-line trajectory, while these errors tend to be cancelled out by a lawn mower pattern_ The paper focuses on the accuracy offered by the DVL. HUGIN 1000 is a permanent organic mine countermeasure (MCM) capacity on the Royal Norwegian Navy MCM vessel KNM Karmoy. HUGIN 1000 will be part of the NATO force MCMFORNORTH in fall 2004. Autonomous underwater vehicle, aided inertial navigation, Kalman filter, Inertial measurement unit,

oai:mic.2004.4.3 2010-03-20

eng Journal article 2004-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2004-4-3.asp Fulltext http://www.mic-journal.no/PDF/2004/MIC-2004-4-3.pdf Development of an in vivo method for determining material properties of passive myocardium Remme, Espen Hunter, Peter J. Smiseth, Otto Stevens, Carey Rabben, Stein I. Skulstad, Helge Angelsen, Bjørn Calculation of mechanical stresses and strains in the left ventricular (LV) myocardium by the finite element (FE) method relies on adequate knowledge of the material properties of myocardial tissue. In this paper we present a model-based estimation procedure to characterize the stress-strain relationship in passive LV myocardium. A 3D FE model of the LV myocardium was used, which included morphological fiber and sheet structure and a nonlinear orthotropic constitutive law with different stiffness in the fiber, sheet and sheet-normal directions. The estimation method was based on measured wall strains. We analyzed the method's ability to estimate the material parameters by generating a set of synthetic strain data by simulating the LV inflation phase with known material parameters. In this way we were able to verify the correctness of the solution and to analyze the effects of measurement and model error on the solution accuracy and stability. A sensitivity analysis was performed to investigate the observability of the material parameters and to determine which parameters to estimate. The results showed a high degree of coupling between the parameters governing the stiffness in each direction. Thus, only one parameter in each of the three directions was estimated. For the tested magnitudes of added noise and introduced model errors, the resulting estimated stress-strain characteristics in the fiber and sheet directions converged with good accuracy to the known relationship. The sheet-normal stress-strain relationship had a higher degree of uncertainty as more noise was added and model error was introduced.

oai:mic.2005.1.1 2010-03-20

eng Journal article 2005-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2005-1-1.asp Fulltext http://www.mic-journal.no/PDF/2005/MIC-2005-1-1.pdf A new optimization algotithm with application to nonlinear MPC Martinsen, Frode Biegler, Lorentz T. Foss, Bjarne A. This paper investigates application of SQP optimization algorithm to nonlinear model predictive control. It considers feasible vs. infeasible path methods, sequential vs. simultaneous methods and reduced vs full space methods. A new optimization algorithm coined rFOPT which remains feasibile with respect to inequality constraints is introduced. The suitable choices between these various strategies are assessed informally through a small CSTR case study. The case study also considers the effect various discretization methods have on the optimization problem. Model predictive control, optimization,

oai:mic.2005.1.2 2010-03-20

eng Journal article 2005-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2005-1-2.asp Fulltext http://www.mic-journal.no/PDF/2005/MIC-2005-1-2.pdf Informative PLS score-loading plots for process understanding and monitoring Ergon, Rolf Principal component regression (PCR) based on principal component analysis (PCA) and partial least squares regression (PLSR) are well known projection methods for analysis of multivariate data. They result in scores and loadings that may be visualized in a score-loading plot (biplot) and used for process monitoring. The difficulty with this is that often more than two principal or PLS components have to be used, resulting in a need to monitor more than one such plot. However, it has recently been shown that for a scalar response variable all PLSR/PCR models can be compressed into equivalent PLSR models with two components only. After a summary of the underlying theory, the. present paper shows how such two-component PLS (2PLS) models can be utilized in informative score-loading biplots for process understanding and monitoring. The possible utilization of known projection model monitoring statistics and variable contribution plots is also discussed, and a new method for visualization of contributions directly in the biplot is presented. An industrial data example is included. PLS, score-loading correspondence, biplot,

oai:mic.2005.1.3 2010-03-20

eng Journal article 2005-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2005-1-3.asp Fulltext http://www.mic-journal.no/PDF/2005/MIC-2005-1-3.pdf A comparison of implementation strategies for MPC Lie, Bernt Díez, Marta D. Hauge, Tor A. Four quadratic programming (QP) formulations of model predictive control (MPC) are compared with regards to ease of formulation, memory requirement, and numerical properties. The comparison is based on two example processes: a paper machine model, and a model of the Tennessee Eastman challenge process; the number of free variables range from 150-1400. Five commercial QP solvers are compared. Preliminary results indicate that dense solvers still are the most efficient, but sparse solvers hold great promise.

oai:mic.2005.2.1 2010-03-20

eng Journal article 2005-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2005-2-1.asp Fulltext http://www.mic-journal.no/PDF/2005/MIC-2005-2-1.pdf Observer Design for Multiphase Flow in Vertical Pipes with Gas Lift - Theory and Experiments Aamo, Ole M. Eikrem, G.O. Siahaan, H.B. Foss, Bjarne A. Unstable regimes occurring for multiphase flow in vertical risers have successfully been stabilized using conventional linear control techniques. However, these control systems rely on downhole measurements which are at best unreliable, if at available. In this paper, we design a nonlinear observer for the states of the multiphase flow that relies on topside measurements only, and apply it to estimate downhole pressure for feedback control. A key feature of the design is that it exploits the structure of the model to obtain robustness with respect to the internal flows in the system. Combining the nonlinear observer with conventional PI control of the downhole pressure, we demonstrate in laboratory experiments the potential for increasing production from gas-lift wells by stabilizing the multiphase flow. Nonlinear observer design, Multiphase flow,

oai:mic.2005.2.2 2010-03-20

eng Journal article 2005-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2005-2-2.asp Fulltext http://www.mic-journal.no/PDF/2005/MIC-2005-2-2.pdf Active Feedback Control of Unstable Wells at the Brage Field Dalsmo, Morten Halvorsen, E. Slupphaug, Olav In this paper we will present new results on stabilization of horizontal wells with gas lift. The stabilization is achieved by a novel dynamic feedback control solution using the production choke at the wellhead. The primary input to the dynamic feedback controller is a measurement of the downhole pressure. The field results to be presented are from the Brage field operated by Norsk Hydro in the North sea. Production at Brage began in 1993 and the field went off plateau in 1998. As the production has decreased, the problems related to unstable production from some of the wells have escalated steadily. The results from the extensive field tests on the Brage wells arc very promising. The tests have confirmed the stabilization feature of the control solution. The pressure and flow variations have been dramatically reduced, and it is possible to produce the wells at a lower downhole pressure leading to increased production. Unstable wells, active feedback control, oil production, gas lift,

oai:mic.2005.2.3 2010-03-20

eng Journal article 2005-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2005-2-3.asp Fulltext http://www.mic-journal.no/PDF/2005/MIC-2005-2-3.pdf Riser slugging - a mathematical model and the practical consequences Sagatun, Svein I. This article presents a novel approach to estimate severe riser slug build up time and consequently the slug period. The slug model is based on a simplified mechanical model. This information has subsequently been used to illustrate the effects of the traditional actions to prevent severe riser slugging. New field data from an offshore floating production platform and large scale experimental data are included. The experimental set up is described in detail. The estimate on the slug built up time provided by the simplified model matches data from the experiments, the full scale data and data in relevant references. Multiphase, slug,

oai:mic.2005.3.1 2010-03-20

eng Journal article 2005-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2005-3-1.asp Fulltext http://www.mic-journal.no/PDF/2005/MIC-2005-3-1.pdf Application of seeding and automatic differentiation in a large scale ocean circulation model Martinsen, Frode Slagstad, Dag Computation of the Jacobian in a 3-dimensional general ocean circulation model is considered in this paper. The Jacobian matrix considered in this paper is square, large and sparse. When a large and sparse Jacobian is being computed, proper seeding is essential to reduce computational times. This paper presents a manually designed seeding motivated by the Arakawa-C staggered grid, and gives results for the manually designed seeding as compated to identity seeding and optimal seeding. Finite differences are computed for reference. Jacobian, automatic differentiation,

oai:mic.2005.3.2 2010-03-20

eng Journal article 2005-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2005-3-2.asp Fulltext http://www.mic-journal.no/PDF/2005/MIC-2005-3-2.pdf NavLab, a Generic Simulation and Post-processing Tool for Navigation Gade, Kenneth The ambition of getting one common tool for a great variety of navigation tasks was the background for the development of NavLab (Navigation Laboratory). The main emphasis during the development has been a solid theoretical foundation with a stringent mathematical representation to ensure that statistical optimality is maintained throughout the entire system_ NavLab is implemented in Matlab. and consists of a simulator and an estimator. Navigation Software, Simulation, Estimation, Analysis. Post-processing, Aided Inertial Navigation System, Kalman Filtering,

oai:mic.2005.3.3 2010-03-20

eng Journal article 2005-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2005-3-3.asp Fulltext http://www.mic-journal.no/PDF/2005/MIC-2005-3-3.pdf Closed Loop Subspace Identification Nilsen, Geir W. Di Ruscio, David A new three step closed loop subspace identifications algorithm based on an already existing algorithm and the Kalman filter properties is presented. The Kalman filter contains noise free states which implies that the states and innovation are uneorre lated. The idea is that a Kalman filter found by a good subspace identification algorithm will give an output which is sufficiently uncorrelated with the noise on the output of the actual process. Using feedback from the output of the estimated Kalman filter in the closed loop system a subspace identification algorithm can be used to estimate an unbiased model. Closed loop, subspace system identification, Kalman filter,

oai:mic.2005.3.4 2010-03-20

eng Journal article 2005-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2005-3-4.asp Fulltext http://www.mic-journal.no/PDF/2005/MIC-2005-3-4.pdf Interaction between control and estimation in nonlinear MPC Hovd, Morten Bitmead, Robert R. This paper shows how to take the quality of the state estimation into account in the formulation of the optimization criterion for model predictive control (MPC). This is relevant for the control of nonlinear plants, for which the separation principle in general does not apply. The method is illustrated on an example which is locally weakly unobservable at the reference state. Nonlinear MPC,

oai:mic.2005.4.1 2010-03-20

eng Journal article 2005-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2005-4-1.asp Fulltext http://www.mic-journal.no/PDF/2005/MIC-2005-4-1.pdf Optimal Statistical Operations for 3-Dimensional Rotational Data: Geometric Interpretations and Application to Prosthesis Kinematics Stavdahl, Øyvind Bondhus, Anne K. Pettersen, Kristin Y. Malvig, Kjell E. Rotational data in the form of measured three-dimensional rotations or orientations arise naturally in many fields of science, including biomechanics, orthopaedics and robotics. The cyclic topology of rotation spaces calls for special care and considerations when performing statistical analysis of rotational data. Relevant theory has been developed during the last three decades, and has become a standard tool in some areas. In relation to the study of human kinematics and motion however, these concepts have hardly been put to use. This paper gives an introduction to the intricacies of three-dimensional rotations, and provides a thorough geometric interpretation of several approaches to averaging rotational data A set of novel, simple operators is presented. Simulations and a prosthetics-related real-world example involving wrist kinematics illuminate important aspects of the results. Finally generalizations and related subjects for further research are suggested. Orientation statistics, rotational data, rotation matrix, quaternion, Euler parameter, Euler angle, orientation vector, attitude vector kinematics, orthopaedics, prosthetics,

oai:mic.2005.4.2 2010-03-20

eng Journal article 2005-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2005-4-2.asp Fulltext http://www.mic-journal.no/PDF/2005/MIC-2005-4-2.pdf A Comparative Study of Actuator Configurations for Satellite Attitude Control Kristiansen, Raymond Egeland, Olav Nicklasson, Per Johan In this paper a controllability study of different actuator configurations consisting of magnetic torquers, reaction wheels and a gravity boom is presented. The theoretical analysis is performed with use of controllability gramians, and simulation results with the different configurations are presented and compared regarding settling time and power consumption to substantiate the theoretical analysis. A reference model is also introduced to show how the power consumption can he lowered to the same magnitude as when magnetic torquers are used, without degrading the satellite response significantly. Reaction wheels, magnetic torquers, controllability,

oai:mic.2005.4.3 2010-03-20

eng Journal article 2005-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2005-4-3.asp Fulltext http://www.mic-journal.no/PDF/2005/MIC-2005-4-3.pdf Advanced life support therapy and on out-of-hospital cardiac arrest patients: Applying signal processing and pattern recognition methods Eftestøl, Trygve Risdal, Martin Eilevstjønn, Joar Steen, Petter A. In the US alone, several hundred thousands die of sudden cardiac arrests each year. Basic life support defined as chest compressions and ventilations and early defibrillation are the only factors proven to increase the survival of patients with out-of-hospital cardiac arrest, and are key elements in the chain of survival defined by the American Heart Association. The current cardiopulmonary resuscitation guidelines treat all patients the same, but studies show need for more individualiza- tion of treatment. This review will focus on ideas on how to strengthen the weak parts of the chain of survival including the ability to measure the effects of therapy, improve time efficiency, and optimize the sequence and quality of the various components of cardiopulmonary resuscitation. Cardiac arrest, ventricular fibrillation, cardiopulmonary resuscitation, ECG analysis, decision support, defibrillation,

oai:mic.2006.1.1 2010-03-20

eng Journal article 2006-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2006-1-1.asp Fulltext http://www.mic-journal.no/PDF/2006/MIC-2006-1-1.pdf The Riccati Equation - An Economic Fundamental Equation which Describes Marginal Movement in Time Lystad, Lars P. Nyman, Per-Ole Høybakk, Ralph The objective of this article is to demonstrate that the Riccati equation is an economic fundamental equation, which is marginally descriptive in time for the large majority of economic systems. It is also an objective to interpret the Riccati equation and the corresponding relations in terms of economics. The article shows that there is a close relationship between the marginal Hamiltonian function and the Riccati equation. The marginal Hamiltonian function will be an expression of the accounts based on optimal behaviour including both the change in result and the change in balance. Riccati equation, marginal time movement, economic interpretation,

oai:mic.2006.1.2 2010-03-20

eng Journal article 2006-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2006-1-2.asp Fulltext http://www.mic-journal.no/PDF/2006/MIC-2006-1-2.pdf State-space representation of radiation forces in time-domain vessel models Kristiansen, Erlend Hjulstad, Åsmund Egeland, Olav The paper presents a method for generating a new and efficient time-domain formulation of the equations of motion for a vessel with frequency-dependent hydrodynamic coefficients. Previous work on this topic has relied on the use of convolution terms, whereas in this work state-space models are used. This leads to a model formulation that is well suited for controller design and simulation. State-space realization, Frequency-dependent characteristics, Time-domain, Convolution integral,

oai:mic.2006.1.3 2010-03-20

eng Journal article 2006-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2006-1-3.asp Fulltext http://www.mic-journal.no/PDF/2006/MIC-2006-1-3.pdf Optimizing nonlinear adaptive control allocation Tjønnås, Johannes Johansen, Tor A. A control-Lyapunov approach is used to develop an adaptive optimizing control allocation algorithm for over-actuated mechanical systems where the actuator model is affine in the uncertain parameters. Uniform global (asymptotic) stability is guaranteed by the control allocation defined by the dynamic update laws in combination with an exponentially stable controller. Nonlinear systems, adaptive control,

oai:mic.2006.1.4 2010-03-20

eng Journal article 2006-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2006-1-4.asp Fulltext http://www.mic-journal.no/PDF/2006/MIC-2006-1-4.pdf Control design for Gas Turbine Cycle with CO2 Capture Capabilities Snarheim, Dagfinn Imsland, Lars Foss, Bjarne A Ulfsnes, Ragnhild Bolland, Olav The semi-closed oxy-fuel gas turbine cycle has been suggested in (Ulizar and Pilidis, 1997) as an alternative for power production with CO2 capture capabilities. This article is concerned with two critical design decisions for a similar process. Optimizations are used on a simulation model to evaluate part load performance for four different control structures. Finally a model predictive controller is implemented for each of the structures, and closed loop simulations are used to assess the different control structures. Control structure, integrated process design, power production,

oai:mic.2006.2.1 2010-03-20

eng Journal article 2006-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2006-2-1.asp Fulltext http://www.mic-journal.no/PDF/2006/MIC-2006-2-1.pdf A reduced basis element method for the steady Stokes problem: Application to hierarchical flow systems Løvgren, Alf E. Maday, Yvon Rønquist, Einar M. The reduced basis element method is a new approach for approximating the solution of problems described by partial differential equations. The method takes its roots in domain decomposition methods and reduced basis discretizations (Fink & Rheinboldt (1983), Noor & Peters (1980), Prud’homme et al. (2002)), and its applications extend to, for example, control and optimization problems. The basic idea is to first decompose the computational domain into a series of subdomains that are similar to a few reference domains (or generic computational parts). Associated with each reference domain are precomputed solutions corresponding to the same governing partial differential equation, but solved for different choices of some underlying parameter. In this work, the parameters are representing the geometric shape associated with a computational part. The approximation corresponding to a new shape is then taken to be a linear combination of the precomputed solutions, mapped from the reference domain for the part to the actual domain. We extend earlier work (Maday & Rønquist (2002), Maday & Rønquist (2004)) in this direction to solve incompressible fluid flow problems governed by the steady Stokes equations. Particular focus is given to constructing the basis functions, to the mapping of the velocity fields, to satisfying the inf-sup condition, and to 'gluing' the local solutions together in the multidomain case (Belgacem et al. (2000)). We also demonstrate an algorithm for choosing the most efficient precomputed solutions. Two-dimensional examples are presented for pipes, bifurcations, and couplings of pipes and bifurcations in order to simulate hierarchical flow systems. Stokes flow, reduced basis, reduced order model, domain decomposition, mortar method, output bounds,

oai:mic.2006.2.2 2010-03-20

eng Journal article 2006-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2006-2-2.asp Fulltext http://www.mic-journal.no/PDF/2006/MIC-2006-2-2.pdf A symmetric splitting method for rigid body dynamics Celledoni, E. Säfström, N. It has been known since the time of Jacobi that the solution to the free rigid body (FRB) equations of motion is given in terms of a certain type of elliptic functions. Using the Arithmetic-Geometric mean algorithm, (1), these functions can be calculated efficiently and accurately. The overall approach yields a faster and more accurate numerical solution to the FRB equations compared to standard numerical ODE and symplectic solvers. In this paper we investigate the possibility of extending this approach to the case of rigid bodies subject to external forces. By using a splitting strategy similar to the one proposed in (14), we decompose the vector field of our problem in a FRB problem and another completely integrable vector field. We apply the method to the simulation of the heavy top. Rigid bodies, symmetric methods, symplectic methods,

oai:mic.2006.2.3 2010-03-20

eng Journal article 2006-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2006-2-3.asp Fulltext http://www.mic-journal.no/PDF/2006/MIC-2006-2-3.pdf Preconditioning of fully implicit Runge-Kutta schemes for parabolic PDEs Staff, Gunnar A. Mardal, Kent-Andre Nilssen, Trygve K. Recently, the authors introduced a preconditioner for the linear systems that arise from fully implicit Runge-Kutta time stepping schemes applied to parabolic PDEs (9). The preconditioner was a block Jacobi preconditioner, where each of the blocks were based on standard preconditioners for low-order time discretizations like implicit Euler or Crank-Nicolson. It was proven that the preconditioner is optimal with respect to the timestep and the discretization parameter in space. In this paper we will improve the convergence by considering other preconditioners like the upper and the lower block Gauss-Seidel preconditioners, both in a left and right preconditioning setting. Finally, we improve the condition number by using a generalized Gauss-Seidel preconditioner. Runge-Kutta methods, PDEs, preconditioning,

oai:mic.2006.2.4 2010-03-20

eng Journal article 2006-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2006-2-4.asp Fulltext http://www.mic-journal.no/PDF/2006/MIC-2006-2-4.pdf Real time hardware-in-loop simulation of ESMO satellite attitude control system Finnset, Rune K. Rao, Sudhakara Antonsen, Jøran This paper studies attitude control of the ESMO satellite using six reaction thrusters. Bang-bang control with dead-zone and Pulse-Width Modulation (PWM) for the modulation of the on-time of the thrusters are treated. Closed loop hardware-in-loop simulations, using themicrocontroller unit (MCU) Microchip PIC18F452 for implementation of attitude control and MatLab in a standard PC for simulating satellite dynamics, are carried out. Results for real time simulation are compared with autonomous simulations. The controller gives a satisfactory performance in the real time environment. Attitude Control, real time simulations,

oai:mic.2006.3.1 2010-03-20

eng Journal article 2006-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2006-3-1.asp Fulltext http://www.mic-journal.no/PDF/2006/MIC-2006-3-1.pdf Control-relevant modeling and simulation of a SOFC-GT hybrid system Kandepu, Rambabu Imsland, Lars Stiller, Christoph Foss, Bjarne A. Kariwala, Vinay In this paper, control-relevant models of the most important components in a SOFC-GT hybrid system are described. Dynamic simulations are performed on the overall hybrid system. The model is used to develop a simple control structure, but the simulations show that more elaborate control is needed. SOFC, GT, control relevant, fuel cells, modeling,

oai:mic.2006.3.2 2010-03-20

eng Journal article 2006-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2006-3-2.asp Fulltext http://www.mic-journal.no/PDF/2006/MIC-2006-3-2.pdf Modelling and control of growing slugs in horizontal multiphase pipe flows Elgsæter, Steinar M. In this paper, the use of active control to restrict the length of growing slugs in horizontal pipelines is investigated. Specifically, the paper attempts to determine if such control can be attained with realistic measurements and actuators. Simulations in OLGA2000 show that a feedback controller can use measurements or estimates of slug length to control the growth of a slug in a horizontal pipeline by partially closing inlet or outlet chokes. A control-volume approach is used to develop a low-order model of inlet choke-slug growth dynamics based on mass- and impulse balances. The resulting model is a system of nonlinear differential-algebraic equations, which is suitable for observer-design. The tuned model is found to be in good agreement with experiments and OLGA2000-simulations. Linearizations of the model are found to be observable around realistic trajectories when rates and pressures at the inlet and outlet are measured. An extended Luenberger-observer is shown to give good estimates of slug length and -position in simulations even under model uncertainty. Active slug control, growing slugs, slugs in horizontal pipelines, slug length observer, multiphase flow,

oai:mic.2006.3.3 2010-03-20

eng Journal article 2006-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2006-3-3.asp Fulltext http://www.mic-journal.no/PDF/2006/MIC-2006-3-3.pdf Stabilizing a CFD model of an unstable system through model reduction Hovland, Svein Gravdahl, Jan T. We demonstate stabilization of a computational fluid dynamics model of an unstable system. The unstable heating of a two-dimensional plate is used as a case study. Active control is introduced by cooling parts of the boundaries of the plate. The high order of the original model is reduced by proper orthogonal decomposition, giving an unstable reduced order model with a state space structure convenient for controller design. A stabilizing controller based on pole placement is designed for the reduced order model and integral action is included to enhance performance. The controller is then applied to the full model, where it is shown through simulations to stabilize the system. The demonstrated procedure makes it possible to analyze stability properties and design control systems for a class of systems that would otherwise be very computationally demanding. Computational fluid dynamics, model-order reduction,

oai:mic.2006.3.4 2010-03-20

eng Journal article 2006-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2006-3-4.asp Fulltext http://www.mic-journal.no/PDF/2006/MIC-2006-3-4.pdf Forward propagation of acoustic pressure pulses in 3D soft biological tissue Varslot, Trond Måsøy, Svein-Erik A simulation method for forward propagation of acoustic pressure pulses in a medium with three-dimensional (3D) spatially-variable acoustic properties is presented. The intended application is to study aspects of ultrasound imaging of soft biological tissue. The forward wave propagation is modelled by a one-way wave equation. The equation describes tissue exhibiting nonlinear elasticity and arbitrary frequency-dependent attenuation. A numerical solution to the equation is found by means of first-order accurate operator splitting and propagation along the spatial depth coordinate. Thus diffraction, nonlinearity and attenuation are solved independently at each propagation step, rendering their relative importance easy to monitor. The method is seen to yield an accurate simulation of the wave propagation when compared to numerical solutions of the full wave equation and experiments in a water tank. By this approach it is possible to simulate wave propagation over relatively large distances - typically several hundred wavelengths - at a modest computational complexity compared to solution of the full wave equation. It furthermore facilitates a high degree of parallelism, thus enabling efficient distribution of the required computations over multiple processors. Medical ultrasound, nonlinear acoustics, parabolic approximation, numerical simulation,

oai:mic.2006.4.1 2010-03-20

eng Journal article 2006-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2006-4-1.asp Fulltext http://www.mic-journal.no/PDF/2006/MIC-2006-4-1.pdf Solving the nonlinear Schrödinger equation using exponential integrators Berland, Håvard Owren, Brynjulf Skaflestad, Bård Using the notion of integrating factors, Lawson developed a class of numerical methods for solving stiff systems of ordinary differential equations. However, the performance of these "Generalized Runge - Kutta processes" was demonstrably poorer when compared to the ETD schemes of Certaine and Nørsett, recently rediscovered by Cox and Matthews. The deficit is particularly pronounced when the schemes are applied to parabolic problems. In this paper we compare a fourth order Lawson scheme and a fourth order ETD scheme due to Cox and Matthews, using the nonlinear Schro¨dinger equation as the test problem. The primary testing parameters are degree of regularity of the potential function and the initial condition, and numerical performance is heavily dependent upon these values. The Lawson and ETD schemes exhibit significant performance differences in our tests, and we present some analysis on this. Exponential integrators, nonlinear Schro¨dinger equation, regularity requirements,

oai:mic.2006.4.2 2010-03-20

eng Journal article 2006-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2006-4-2.asp Fulltext http://www.mic-journal.no/PDF/2006/MIC-2006-4-2.pdf Systematic Analysis of Parameter Identifiability for Improved Fitting of a Biological Wastewater Model to Experimental Data Sarmiento, Cristina Ferrero Chai, Qian Díez, Marta D. Amrani, Sverre H. Lie, Bernt In this paper, a general description of wastewater treatment based on activated sludge is given, with emphasis on the ASM2d model. Particular emphasis has been given to make the presentation readable without a too detailed prior knowledge of wastewater treatment. Next, a method for experimental parameter identifiability analysis is described. After a presentation of the wastewater treatment plant at Duvbacken in Gävle, Sweden, the experimental identifiability of the dynamic model is analyzed. Out of the 45 original parameters in the model, the analysis indicates that with the given experimental conditions, 12 parameters can be identified. ASM2d, identifiability analysis, parameter estimation,

oai:mic.2006.4.3 2010-03-20

eng Journal article 2006-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2006-4-3.asp Fulltext http://www.mic-journal.no/PDF/2006/MIC-2006-4-3.pdf Hardware-in-the-loop testing of marine control system Skjetne, Roger Egeland, Olav Hardware-in-the-Loop (HIL) testing is proposed as a new methodology for verification and certification of marine control systems. Formalizing such testing necessitates the development of a vocabulary and set of definitions. This paper treats these issues by constructing a framework suitable for industrial HIL test applications and certification of marine systems. Hardware-in-the-loop simulation, black box testing, functional testing, marine control systems, failure modes, testability, IEC 61508,

oai:mic.2006.4.4 2010-03-20

eng Journal article 2006-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2006-4-4.asp Fulltext http://www.mic-journal.no/PDF/2006/MIC-2006-4-4.pdf An Overview of the Marine Systems Simulator (MSS): A Simulink Toolbox for Marine Control Systems Perez, Tristan Smogeli, Øyvind N. Fossen, Thor I. Sørensen, Asgeir J. The Marine Systems Simulator (MSS) is an environment which provides the necessary resources for rapid implementation of mathematical models of marine systems with focus on control system design. The simulator targets models¡Xand provides examples ready to simulate¡Xof different floating structures and its systems performing various operations. The platform adopted for the development of MSS is Matlab/Simulink. This allows a modular simulator structure, and the possibility of distributed development. Openness and modularity of software components have been the prioritized design principles, which enables a systematic reuse of knowledge and results in efficient tools for research and education. This paper provides an overview of the structure of the MSS, its features, current accessability, and plans for future development. Marine system dynamics, models,

oai:mic.2007.1.1 2010-03-20

eng Journal article 2007-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2007-1-1.asp Fulltext http://www.mic-journal.no/PDF/2007/MIC-2007-1-1.pdf A model of relative translation and rotation in leader-follower spacecraft formations Kristiansen, Raymond Grøtli, Esten I. Nicklasson, Per J. Gravdahl, Jan T. In this paper, a model of a leader-follower spacecraft formation in six degrees of freedom is derived and presented. The nonlinear model describes the relative translational and rotationalmotion of the spacecraft, and extends previous work by providing a more complete factorization, together with detailed information about the matrices in the model. The resulting model shows many similarities with models for systems such as robot manipulators and marine vehicles. In addition, mathematical models of orbital perturbations due to gravitational variations, atmospheric drag, solar radiation and third-body effects are presented for completeness. Results from simulations are presented to visualize the properties of the model and to show the impact of the different orbital perturbations on the flight path. Spacecraft formation, relative motion, 3D general orbits,

oai:mic.2007.1.2 2010-03-20

eng Journal article 2007-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2007-1-2.asp Fulltext http://www.mic-journal.no/PDF/2007/MIC-2007-1-2.pdf Modified Smith-predictor multirate control utilizing secondary process measurements Ergon, Rolf The Smith-predictor is a well-known control structure for industrial time delay systems, where the basic idea is to estimate the non-delayed process output by use of a process model, and to use this estimate in an inner feedback control loop combined with an outer feedback loop based on the delayed estimation error. The model used may be either mechanistic or identified from input-output data. The paper discusses improvements of the Smith-predictor for systems where also secondary process measurements without time delay are available as a basis for the primary output estimation. The estimator may then be identified also in the common case with primary outputs sampled at a lower rate than the secondary outputs. A simulation example demonstrates the feasibility and advantages of the suggested control structure. Smith-predictor, secondary outputs,

oai:mic.2007.1.3 2010-03-20

eng Journal article 2007-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2007-1-3.asp Fulltext http://www.mic-journal.no/PDF/2007/MIC-2007-1-3.pdf Kinematic Models for Manoeuvring and Seakeeping of Marine Vessels Perez, Tristan Fossen, Thor Inge The motion of marine vessels has traditionally been studied using two different approaches: manoeuvring and seakeeping. These two approaches use different reference frames and coordinate systems to describe the motion. This paper derives the kinematic models that characterize the transformation of motion variables (position, velocity, accelerations) and forces between the different coordinate systems used in these theories. The derivations hereby presented are done in terms of the formalism adopted in robotics. The advantage of this formulation is the use of matrix notation and operations. As an application, the transformation of linear equations of motion used in seakeeping into body-fixed coordinates is considered for both zero and forward speed. Kinematics, ship motion, seakeeping,

oai:mic.2007.2.1 2010-03-20

eng Journal article 2007-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2007-2-1.asp Fulltext http://www.mic-journal.no/PDF/2007/MIC-2007-2-1.pdf Game play in vocational training and engineering education Foss, Bjarne A. Solbjørg, Ole K. Eikaas, Tor I. Jakobsen, Frank Educational games may create a new and improved learning culture by drawing advantage of the new knowledge and skills of today’s students obtained from extensive use of interactive game software. This paper presents a design basis and online learning resources taking advantage of game-related features like a high degree of interactivity, attractive graphics, a dynamical virtual universe, and an incentive system to promote prolonged and more advanced use. The educational resources, denoted PIDstop, are targeted towards the engineering domain. Feedback from over 2000 users clearly indicates that PIDstop has a positive learning effect. Training packages for vocational training of Automation Technicians is emphasized in this paper. Such learning resources must have a limited mathematical complexity; hence, the representation should be rather descriptive. Evaluation of learning resources to assess the actual learning effect is important, and a two-step procedure based on formative and summative evaluation is proposed for this purpose. Dynamic simulation, games, technical education,

oai:mic.2007.2.2 2010-03-20

eng Journal article 2007-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2007-2-2.asp Fulltext http://www.mic-journal.no/PDF/2007/MIC-2007-2-2.pdf New Undergraduate Courses in Control Gravdahl, Jan T. Egeland, Olav In this paper we describe the motivation behind and the contents of two new control courses, Introduction to Computerized Control and Modeling and Simulation developed at the Department of Engineering Cybernetics, Norwegian University of Science and Technology. Control education, modeling,

oai:mic.2007.2.3 2010-03-20

eng Journal article 2007-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2007-2-3.asp Fulltext http://www.mic-journal.no/PDF/2007/MIC-2007-2-3.pdf A simulation game for nonlinear control theory education Haugom, Rune Solbjørg, Ole K. Pettersen, Kristin Y. Eikaas, Tor I. In this paper a computer game implemented as an applet for use in a graduate course in nonlinear control theory is described, and the learning value of the game is substantiated using different learning theories and theories related to ICT. The case study of the applet is a mass-damper-spring system with a nonlinear spring characteristic, and a game with a highscore list has been made out of the system to stimulate student competition and motivation. Learning theories, simulation, linear/nonlinear control, computer game,

oai:mic.2007.3.1 2010-03-20

eng Journal article 2007-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2007-3-1.asp Fulltext http://www.mic-journal.no/PDF/2007/MIC-2007-3-1.pdf New Schemes for Positive Real Truncation Unneland, Kari Van Dooren, Paul Egeland, Olav Model reduction, based on balanced truncation, of stable and of positive real systems are considered. An overview over some of the already existing techniques are given: Lyapunov balancing and stochastic balancing, which includes Riccati balancing. A novel scheme for positive real balanced truncation is then proposed, which is a combination of the already existing Lyapunov balancing and Riccati balancing. Using Riccati balancing, the solution of two Riccati equations are needed to obtain positive real reduced order systems. For the suggested method, only one Lyapunov equation and one Riccati equation are solved in order to obtain positive real reduced order systems, which is less computationally demanding. Further it is shown, that in order to get positive real reduced order systems, only one Riccati equation needs to be solved. Finally, this is used to obtain positive real frequency weighted balanced truncation. Model Reduction, Balanced Truncation, Positive Realness,

oai:mic.2007.3.2 2010-03-20

eng Journal article 2007-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2007-3-2.asp Fulltext http://www.mic-journal.no/PDF/2007/MIC-2007-3-2.pdf Nonlinear Model-Based Control of Unstable Wells Kaasa, Glenn-Ole Alstad, Vidar Zhou, Jing Aamo, Ole M. This paper illustrates the potential of nonlinear model-based control applied for stabilization of unstable flow in oil wells. A simple empirical model is developed that describes the qualitative behavior of the downhole pressure during severe riser slugging. A nonlinear controller is designed by an integrator backstepping approach, and stabilization for open-loop unstable pressure setpoints is demonstrated. The proposed backstepping controller is shown in simulations to perform better than PI and PD controllers for low pressure setpoints, and is in addition easier to tune. Operation at a low pressure setpoint is desirable since it corresponds to a high production flow rate. The simulation results are presented to illustrate the effectiveness of proposed control scheme. Nonlinear control, slugging, backstepping,

oai:mic.2007.3.3 2010-03-20

eng Journal article 2007-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2007-3-3.asp Fulltext http://www.mic-journal.no/PDF/2007/MIC-2007-3-3.pdf Improved Target Calculation for Model Predictive Control Hovd, Morten In industrial Model Predictive Control (MPC) applications, it is common to perform target calculation at each sample instant. The purpose of the target calculation is to translate operational targets supplied by higher level optimization functions into control targets that are feasible in the face of current disturbances. This paper shows that the commonly used target calculation formulation is flawed, and that this can lead to significant economic loss. A method for dealing with the identi¯ed problem is proposed. Model predictive control, target calculation,

oai:mic.2007.4.1 2010-03-20

eng Journal article 2007-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2007-4-1.asp Fulltext http://www.mic-journal.no/PDF/2007/MIC-2007-4-1.pdf Nonlinear Container Ship Model for the Study of Parametric Roll Resonance Holden, Christian Galeazzi, Roberto Rodríguez, Claudio Perez, Tristan Fossen, Thor Inge Blanke, Mogens de Almeida, Marcelo Neves, Santos Parametric roll is a critical phenomenon for ships, whose onset may cause roll oscillations up to +-40 degrees, leading to very dangerous situations and possibly capsizing. Container ships have been shown to be particularly prone to parametric roll resonance when they are sailing in moderate to heavy head seas. A Matlab/Simulink parametric roll benchmark model for a large container ship has been implemented and validated against a wide set of experimental data. The model is a part of a Matlab/Simulink Toolbox (MSS, 2007). The benchmark implements a 3rd-order nonlinear model where the dynamics of roll is strongly coupled with the heave and pitch dynamics. The implemented model has shown good accuracy in predicting the container ship motions, both in the vertical plane and in the transversal one. Parametric roll has been reproduced for all the data sets in which it happened, and the model provides realistic results which are in good agreement with the model tank experiments.

oai:mic.2007.4.2 2010-03-20

eng Journal article 2007-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2007-4-2.asp Fulltext http://www.mic-journal.no/PDF/2007/MIC-2007-4-2.pdf Experimental Validation of a Marine Propeller Thrust Estimation Scheme Pivano, Luca Smogeli, Øyvind N. Johansen, Tor A. Fossen, Thor Inge A thrust estimation scheme for a marine propeller has been experimentally tested in waves and with a device that simulates the influence of a vessel hull. The scheme is formed by a nonlinear propeller torque observer and a mapping to generate the thrust from the observed torque. The mapping includes the estimation of the advance number. This is utilized to improve the performance when the propeller is lightly loaded. The advance speed is assumed to be unknown, and only measurements of shaft speed and motor torque have been used. Accurate results have been obtained in experimental tests. Propulsion, state estimation, nonlinear,

oai:mic.2007.4.3 2010-03-20

eng Journal article 2007-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2007-4-3.asp Fulltext http://www.mic-journal.no/PDF/2007/MIC-2007-4-3.pdf Towards Model-Aided Navigation of Underwater Vehicles Hegrenæs, Øyvind Hallingstad, Oddvar Gade, Kenneth This paper reports the development and preliminary experimental evaluation of a model-aided inertial navigation system (INS) for underwater vehicles. The implemented navigation system exploits accurate knowledge of the vehicle dynamics through an experimentally validated mathematical model, relating the water-relative velocity of the vehicle to the forces and moments acting upon it. Together with online current estimation, the model output is integrated in the navigation system. The proposed approach is of practical interest both for underwater navigation when lacking disparate velocity measurements, typically from a Doppler velocity log (DVL), and for systems where the need for redundancy and integrity is important, e.g. during sensor dropouts or failures, or in case of emergency navigation. The presented results verify the concept that with merely an addition of software and no added instrumentation, it is possible to considerably improve the accuracy and robustness of an INS by utilizing the output from a kinetic vehicle model. To the best of our knowledge, this paper is the first report on the implementation and experimental evaluation of model-aided INS for underwater vehicle navigation.

oai:mic.2008.1.1 2010-03-20

eng Journal article 2008-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2008-1-1.asp Fulltext http://www.mic-journal.no/PDF/2008/MIC-2008-1-1.pdf Time- vs. Frequency-domain Identification of Parametric Radiation Force Models for Marine Structures at Zero Speed Perez, Tristan Fossen, Thor I. The dynamics describing the motion response of a marine structure in waves can be represented within a linear framework by the Cummins Equation. This equation contains a convolution term that represents the component of the radiation forces associated with fluid memory effects. Several methods have been proposed in the literature for the identification of parametric models to approximate and replace this convolution term. This replacement can facilitate the model implementation in simulators and the analysis of motion control designs. Some of the reported identification methods consider the problem in the time domain while other methods consider the problem in the frequency domain. This paper compares the application of these identification methods. The comparison is based not only on the quality of the estimated models, but also on the ease of implementation, ease of use, and the flexibility of the identification method to incorporate prior information related to the model being identified. To illustrate the main points arising from the comparison, a particular example based on the coupled vertical motion of a modern containership vessel is presented. Identification, Frequency-domain, Time-domain,

oai:mic.2008.1.2 2010-03-20

eng Journal article 2008-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2008-1-2.asp Fulltext http://www.mic-journal.no/PDF/2008/MIC-2008-1-2.pdf Modular Pneumatic Snake Robot: 3D Modelling, Implementation And Control Liljebäck, Pål Stavdahl, Øyvind Pettersen, Kristin Y. This paper gives a treatment of various aspects related to snake locomotion. A mathematical model and a physical implementation of a modular snake robot are presented. A control strategy is also developed, yielding a general expression for different gait patterns. Two forms of locomotion have been simulated with the mathematical model, and experiments with the physical snake robot have been conducted. The simulation results revealed the parameter through which directional control may be achieved for each gait pattern. Experiments with the physical snake robot gave a crude qualitative verification of these findings. Snake robot, kinematics,

oai:mic.2008.1.3 2010-03-20

eng Journal article 2008-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2008-1-3.asp Fulltext http://www.mic-journal.no/PDF/2008/MIC-2008-1-3.pdf A new perspective on stable inversion of non-minimum phase nonlinear systems Pavlov, Alexey Pettersen, Kristin Y. We present a new perspective on the problem of stable inversion of nonlinear non-minimum phase systems. It is based on the notion of convergent systems. The machinery of convergent systems allows us to obtain novel qualitative and quantitative conditions for solving this problem. These conditions provide insight into the dynamics behind the stable inversion problem and make it possible to treat this problem in a non-local way. Qualitatively, they cover the conditions for the stable inversion of non-minimum phase nonlinear systems previously reported in literature and allow us to solve this problem for a broader class of systems. The proposed approach is supported with a novel computational method. Stable inversion, non-minimum phase systems, nonlinear systems,

oai:mic.2008.2.1 2010-03-20

eng Journal article 2008-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2008-2-1.asp Fulltext http://www.mic-journal.no/PDF/2008/MIC-2008-2-1.pdf General Solutions to Functional and Kinematic Redundancy From, Pål J. Gravdahl, Jan T. A systematic and general approach to represent functional redundancy is presented. It is shown how this approach allows the freedom provided by functional redundancy to be integrated into the inverse geometric problem for real-time applications and how it can be utilised to improve performance. A set of new iterative solutions to the inverse geometric problem, well suited for kinematically redundant manipulators, is also presented. Robotics, Kinematics,

oai:mic.2008.2.2 2010-03-20

eng Journal article 2008-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2008-2-2.asp Fulltext http://www.mic-journal.no/PDF/2008/MIC-2008-2-2.pdf Observer Design for Second-Order Distributed Parameter Systems in R2 Nguyen, Tu Duc Observer design for second-order distributed parameter systems in R2 is addressed. Particularly, second order distributed parameter systems without distributed damping are studied. Based on finite number of measurements, exponentially stable observer is designed. The existence, uniqueness and stability of solutions of the observer are based on semigroup theory.

oai:mic.2008.2.3 2010-03-20

eng Journal article 2008-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2008-2-3.asp Fulltext http://www.mic-journal.no/PDF/2008/MIC-2008-2-3.pdf Operational space synchronization of two robot manipulators through a virtual velocity estimate Kyrkjebø, Erik Pettersen, Kristin Y. Two robot manipulators are synchronized in a leader-follower scheme where only joint position measurements of the leader are available. A virtual manipulator is designed to provide a velocity estimate of the unknown leader velocity to the control law of the follower. The closed-loop errors are shown to be uniformly globally practically asymptotically stable. Robot manipulator, synchronization, observer, nonlinear,

oai:mic.2008.2.4 2010-03-20

eng Journal article 2008-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2008-2-4.asp Fulltext http://www.mic-journal.no/PDF/2008/MIC-2008-2-4.pdf Optimizing Adaptive Control Allocation With Actuator Dynamics Tjønnås, Johannes Johansen, Tor A. In this work we address the optimizing control allocation problem for an over-actuated nonlinear time- varying system with actuator dynamic where parameters affine in the actuator and effector model may be assumed unknown. Instead of optimizing the control allocation at each time instant, a dynamic approach is considered by constructing actuator reference update-laws that represent an asymptotically optimal allocation search. By using Lyapunov analysis for cascaded set-stable systems, uniform global/local asymptotic stability is guaranteed for the optimal equilibrium sets described by the system, the control allocation update-law and the adaptive update-law, if some persistence of exitation condition holds. Simulations of a scaled-model ship, manoeuvred at low-speed, demonstrate the performance of the proposed allocation scheme.

oai:mic.2008.3.1 2010-03-20

eng Journal article 2008-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2008-3-1.asp Fulltext http://www.mic-journal.no/PDF/2008/MIC-2008-3-1.pdf Iterative Solutions to the Inverse Geometric Problem for Manipulators with no Closed Form Solution From, Pål Johan Gravdahl, Jan Tommy A set of new iterative solutions to the inverse geometric problem is presented. The approach is general and does not depend on intersecting axes or calculation of the Jacobian. The solution can be applied to any manipulator and is well suited for manipulators for which convergence is poor for conventional Jacobian-based iterative algorithms. For kinematically redundant manipulators, weights can be applied to each joint to introduce stiffness and for collision avoidance. The algorithm uses the unit quaternion to represent the position of each joint and calculates analytically the optimal position of the joint when only the respective joint is considered. This sub-problem is computationally very efficient due to the analytical solution. Several algorithms based on the solution of this sub-problem are presented. For difficult problems, for which the initial condition is far from a solution or the geometry of the manipulator makes the solution hard to reach, it is shown that the algorithm finds a solution fairly close to the solution in only a few iterations. Robotics, Kinematics,

oai:mic.2008.3.2 2010-03-20

eng Journal article 2008-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2008-3-2.asp Fulltext http://www.mic-journal.no/PDF/2008/MIC-2008-3-2.pdf Joint Identification of Infinite-Frequency Added Mass and Fluid-Memory Models of Marine Structures Perez, Tristan Fossen, Thor I. This paper addresses the problem of joint identification of infinite-frequency added mass and fluid memory models of marine structures from finite frequency data. This problem is relevant for cases where the code used to compute the hydrodynamic coefficients of the marine structure does not give the infinite-frequency added mass. This case is typical of codes based on 2D-potential theory since most 3D-potential-theory codes solve the boundary value associated with the infinite frequency. The method proposed in this paper presents a simpler alternative approach to other methods previously presented in the literature. The advantage of the proposed method is that the same identification procedure can be used to identify the fluid-memory models with or without having access to the infinite-frequency added mass coefficient. Therefore, it provides an extension that puts the two identification problems into the same framework. The method also exploits the constraints related to relative degree and low-frequency asymptotic values of the hydrodynamic coefficients derived from the physics of the problem, which are used as prior information to refine the obtained models. Identification, Frequency-domain,

oai:mic.2008.3.3 2010-03-20

eng Journal article 2008-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2008-3-3.asp Fulltext http://www.mic-journal.no/PDF/2008/MIC-2008-3-3.pdf Coordinator MPC for maximizing plant throughput Aske, Elvira M.B. Strand, Stig Skogestad, Sigurd In many cases economic optimal operation is the same as maximum plant throughput, which is the same as maximum flow through the bottleneck(s). This insight may greatly simplify implementation. In this paper, we consider the case where the bottlenecks may move, with parallel flows that give rise to multiple bottlenecks and with crossover flows as extra degrees of freedom. With the assumption that the flow through the network is represented by a set of units with linear flow connections, the maximum throughput problem is then a linear programming (LP) problem. We propose to implement maximum throughput by using a coordinator model predictive controller (MPC). Use of MPC to solve the LP has the benefit of allowing for a coordinated dynamic implementation. The constraints for the coordinator MPC are the maximum flows through the individual units. These may change with time and a key idea is that they can be obtained with almost no extra effort using the models in the existing local MPCs. The coordinator MPC has been tested on a dynamic simulator for parts of the Kårstø gas plant and performs well for the simulated challenges. bottleneck, maximize throughput,

oai:mic.2008.4.1 2010-03-20

eng Journal article 2008-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2008-4-1.asp Fulltext http://www.mic-journal.no/PDF/2008/MIC-2008-4-1.pdf Data reconciliation and optimal operation of a Catalytic naphtha reformer Lid, Tore Skogestad, Sigurd The naphtha reforming process converts low-octane gasoline blending components to high-octane components for use in high-performance gasoline fuels. The reformer also has an important function as the producer of hydrogen to the refinery hydrotreaters. A process model based on a unit model structure, is used for estimation of the process condition using data reconciliation. Measurements are classified as redundant or non redundant and the model variables are classified as observable, barely observable or unobservable. The computed uncertainty of the measured and unmeasured variables shows that even if a variable is observable it may have a very large uncertainty and may thereby be practically unobservable. The process condition at 21 data points, sampled from two years of operation, was reconciled and used to optimize the process operation. There are large seasonal variations in the reformer product price and two operational cases are studied. In case 1, the product price is high and throughput is maximized with respect to process and product quality constraints. In case 2, the product price is low and the throughput is minimized with respect to a low constraint on the hydrogen production. Based on the characteristics of the optimal operation, a "self optimizing" control structure is suggested for each of the two operational cases. Optimization, Data Reconciliation, Simulation, Unit Models,

oai:mic.2008.4.2 2010-03-20

eng Journal article 2008-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2008-4-2.asp Fulltext http://www.mic-journal.no/PDF/2008/MIC-2008-4-2.pdf Straight-Line Target Tracking for Unmanned Surface Vehicles Breivik, Morten Hovstein, Vegard E. Fossen, Thor I. This paper considers the subject of straight-line target tracking for unmanned surface vehicles (USVs). Target-tracking represents motion control scenarios where no information about the target behavior is known in advance, i.e., the path that the target traverses is not defined apriori. Specifically, this work presents the design of a motion control system which enables an underactuated USV to track a target that moves in a straight line at high speed. The motion control system employs a guidance principle originally developed for interceptor missiles, as well as a novel velocity controller inspired by maneuverability and agility concepts found in fighter aircraft literature. The performance of the suggested design is illustrated through full-scale USV experiments in the Trondheimsfjord. Target Tracking, Unmanned Surface Vehicles, High Speed Motion, Underactuation, Constant Bearing Guidance, Velocity Control System,

oai:mic.2008.4.3 2010-03-20

eng Journal article 2008-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2008-4-3.asp Fulltext http://www.mic-journal.no/PDF/2008/MIC-2008-4-3.pdf On the Mobility and Fault Tolerance of Closed Chain Manipulators with Passive Joints From, Pål J. Gravdahl, Jan T. A systematic analysis of the mobility of closed chain manipulators with passive joints is presented. The main observation in this paper is that the mobility of the manipulator, considering the passive joints only, should always be zero. Further, for the manipulator to be fault tolerant, the mobility should remain zero when actuator failure occurs for an arbitrary joint. We present a simple and rigorous approach to the problem of finding the smallest set of active joints for which the manipulator remains equilibrated with respect to free swinging joint failure in any joint. Several examples of how to choose the active joints for different mechanisms to guarantee that the manipulator is equilibrated and fault tolerant are presented. Robotics, kinematics, mobility,

oai:mic.2009.1.1 2010-03-20

eng Journal article 2009-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2009-1-1.asp Fulltext http://www.mic-journal.no/PDF/2009/MIC-2009-1-1.pdf A Matlab Toolbox for Parametric Identification of Radiation-Force Models of Ships and Offshore Structures Perez, Tristan Fossen, Thor Inge This article describes a Matlab toolbox for parametric identification of fluid-memory models associated with the radiation forces ships and offshore structures. Radiation forces are a key component of force-to- motion models used in simulators, motion control designs, and also for initial performance evaluation of wave-energy converters. The software described provides tools for preparing non-parmatric data and for identification with automatic model-order detection. The identification problem is considered in the frequency domain. Frequency-Domain Identification, Models of Ships and Offshore Structures,

oai:mic.2009.1.2 2010-03-20

eng Journal article 2009-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2009-1-2.asp Fulltext http://www.mic-journal.no/PDF/2009/MIC-2009-1-2.pdf Robust Explicit Moving Horizon Control and Estimation: A Batch Polymerization Case Study Sui, Dan Feng, Le Hovd, Morten This paper focuses on the design and evaluation of a robust explicit moving horizon controller and a robust explicit moving horizon estimator for a batch polymerization process. It is of particular interest since there are currently no reported case studies or implementations of the explicit parametric controller/estimator for batch and polymerization processes. In this paper we aim at achieving tight offset-free tracking of a desired reactor temperature profile, making accurate states estimation despite of the possible perturbations, and demonstrating the practical applicability to a case with industrially relevant complexity. batch polymerization reactor, explicit moving horizon control, explicit moving horizon estimation,

oai:mic.2009.1.3 2010-03-20

eng Journal article 2009-01-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2009-1-3.asp Fulltext http://www.mic-journal.no/PDF/2009/MIC-2009-1-3.pdf Robust H-Infinity Filter Design for Uncertain Linear Systems Over Network with Network-Induced Delays and Output Quantization Karimi, Hamid Reza This paper investigates a convex optimization approach to the problem of robust H-Infinity filtering for uncertain linear systems connected over a common digital communication network. We consider the case where quantizers are static and the parameter uncertainties are norm bounded. Firstly, we propose a new model to investigate the effect of both the output quantization levels and the network conditions. Secondly, by introducing a descriptor technique, using Lyapunov-Krasovskii functional and a suitable change of variables, new required sufficient conditions are established in terms of delay-dependent linear matrix inequalities (LMIs) for the existence of the desired network-based quantized filters with simultaneous consideration of network induced delays and measurement quantization. The explicit expression of the filters is derived to satisfy both asymptotic stability and a prescribed level of disturbance attenuation for all admissible norm bounded uncertainties. Filter design, network, output quantization,

oai:mic.2009.2.1 2010-03-20

eng Journal article 2009-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2009-2-1.asp Fulltext http://www.mic-journal.no/PDF/2009/MIC-2009-2-1.pdf Kinematic and Elastostatic Design Optimisation of the 3-DOF Gantry-Tau Parallel Kinematic Manipulator Tyapin, Ilya Hovland, Geir One of the main advantages of the Gantry-Tau machine is a large accessible workspace/footprint ratio compared to many other parallel machines. The Gantry-Tau improves this ration further by allowing a change of assembly mode without internal link collisions or collisions between the links and end-effector. The reconfigurable Gantry-Tau kinematic design obtained by multi-objective optimisation according to this paper gives the following features: 3-D workspace/footprint ratio is more than 3.19, lowest Cartesian stiffness in the workspace is $5N/\mu m$ and no link collisions detected. The optimisation parameters are the support frame lengths, the actuator positions and the robot's arm lengths. The results comparison between the evolutionary complex search algorithm and gradient-based method used for the Gantry-Tau design in the past is also presented in this paper. The detailed statics model analysis of the Gantry-Tau based on a functionally dependency is presented in this paper for the first time. Both the statics model and complex search algorithm may be applied for other 3-DOF Hexapods without major changes. The existing lab prototype of the Gantry-Tau was assembled and completed at the University of Agder, Norway. parallel manipulator, statics,

oai:mic.2009.2.2 2010-03-20

eng Journal article 2009-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2009-2-2.asp Fulltext http://www.mic-journal.no/PDF/2009/MIC-2009-2-2.pdf Constrained Control Design for Dynamic Positioning of Marine Vehicles with Control Allocation Perez, Tristan Donaire, Alejandro In this paper, we address the control design problem of positioning of over-actuated marine vehicles with control allocation. The proposed design is based on a combined position and velocity loops in a multi-variable anti-windup implementation together with a control allocation mapping. The vehicle modelling is considered with appropriate simplifications related to low-speed manoeuvring hydrodynamics and vehicle symmetry. The control design is considered together with a control allocation mapping. We derive analytical tuning rules based on requirements of closed-loop stability and performance. The anti- windup implementation of the controller is obtained by mapping the actuator-force constraint set into a constraint set for the generalized forces. This approach ensures that actuation capacity is not violated by constraining the generalized control forces; thus, the control allocation is simplified since it can be formulated as an unconstrained problem. The mapping can also be modified on-line based on actuator availability to provide actuator-failure accommodation. We provide a proof of the closed-loop stability and illustrate the performance using simulation scenarios for an open-frame underwater vehicle. Marine control systems, dynamic positioning, control allocation, anti-windup,

oai:mic.2009.2.3 2010-03-20

eng Journal article 2009-04-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2009-2-3.asp Fulltext http://www.mic-journal.no/PDF/2009/MIC-2009-2-3.pdf Closed and Open Loop Subspace System Identification of the Kalman Filter Di Ruscio, David Some methods for consistent closed loop subspace system identification presented in the literature are analyzed and compared to a recently published subspace algorithm for both open as well as for closed loop data, the DSR_e algorithm. Some new variants of this algorithm are presented and discussed. Simulation experiments are included in order to illustrate if the algorithms are variance efficient or not. Subspace, Identification, Closed loop, Linear Systems,

oai:mic.2009.3.1 2010-03-20

eng Journal article 2009-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2009-3-1.asp Fulltext http://www.mic-journal.no/PDF/2009/MIC-2009-3-1.pdf Hooked on a New Technology: The Automation Pioneers in Post-War Norway Kvaal, Stig This paper presents the initial activities in servo engineering in Norway originating in the early 1950s based on contacts at the Massachusets Institute of Technology. The activities were initiated by a small group of servo enthusiasts who, through the Feedback Control Committee in the research council, managed to coordinate national activities and establish strong research groups in Trondheim, Bergen and Oslo. After the initial phase of establishing the research groups, there was a continuous strong focus on connections with industry and industrial applications. In the mid-1960s the committee was strengthened and became the Automation and Data Processing Committee. The initial group of automation pioneers have left a lasting impact on the academic and industrial fields of servo engineering and automation in Norway. Automation Pioneers, Feedback Control Committee, NTNF, Norway, 1950s,

oai:mic.2009.3.2 2010-03-20

eng Journal article 2009-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2009-3-2.asp Fulltext http://www.mic-journal.no/PDF/2009/MIC-2009-3-2.pdf Jens Glad Balchen: A Norwegian Pioneer in Engineering Cybernetics Breivik, Morten Sand, Gunnar This paper tells the story of Jens Glad Balchen (1926-2009), a Norwegian research scientist and engineer who is widely regarded as the father of Engineering Cybernetics in Norway. In 1954, he founded what would later become the Department of Automatic Control at the Norwegian Institute of Technology in Trondheim. This name was changed to the Department of Engineering Cybernetics in 1972 to reflect the broader efforts being made, not only within the purely technical disciplines, but also within biology, oceanography and medicine. Balchen established an advanced research community in cybernetics in postwar Norway, whose applications span everything from the process industry and positioning of ships to control of fish and lobster farming. He was a chief among the tribe of Norwegian cybernetics engineers and made a strong impact on his colleagues worldwide. He planted the seeds of a whole generation of Norwegian industrial companies through his efforts of seeking applications for every scientific breakthrough. His strength and his wisdom in combination with his remarkable stubbornness gave extraordinary results. Jens Glad Balchen, Servo Engineering, Automatic Control, Engineering Cybernetics, IFAC, NFA, DIANA, Ship Automation, DP, Cyberfish, Lobster Farming,

oai:mic.2009.3.3 2010-03-20

eng Journal article 2009-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2009-3-3.asp Fulltext http://www.mic-journal.no/PDF/2009/MIC-2009-3-3.pdf The Department of Engineering Cybernetics at NTNU: From 1994 Into the Future Johansen, Tor A. Hovd, Morten A short overview of the developments at the Department of Engineering Cybernetics at NTNU over the last 15 years is given. The vision of the department is to stay among Europe's most well recognized universities in control engineering, both with respect to education and research. It is discussed how this is achieved, and will continue to be strengthened in the future. Engineering Cybernetics, Control Engineering, ITK,

oai:mic.2009.3.4 2010-03-20

eng Journal article 2009-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2009-3-4.asp Fulltext http://www.mic-journal.no/PDF/2009/MIC-2009-3-4.pdf Modeling, Identification and Control at Telemark University College Lie, Bernt Di Ruscio, David Ergon, Rolf Glemmestad, Bjørn Halstensen, Maths Haugen, Finn Mylvaganam, Saba Skeie, Nils-Olav Winkler, Dietmar Master studies in process automation started in 1989 at what soon became Telemark University College, and the 20 year anniversary marks the start of our own PhD degree in Process, Energy and Automation Engineering. The paper gives an overview of research activities related to control engineering at Department of Electrical Engineering, Information Technology and Cybernetics. modeling, simulation, identification, control,

oai:mic.2009.3.5 2010-03-20

eng Journal article 2009-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2009-3-5.asp Fulltext http://www.mic-journal.no/PDF/2009/MIC-2009-3-5.pdf Feedback: Still the Simplest and Best Solution Skogestad, S. Most engineers are (indirectly) trained to be "feedforward thinkers" and they immediately think of "model inversion" when it comes to doing control. Thus, they prefer to rely on models instead of data, although feedback solutions in most cases are much simpler and more robust. Classical control, stabilizing control, fundamental limitations, self-optimizing control,

oai:mic.2009.3.6 2010-03-20

eng Journal article 2009-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2009-3-6.asp Fulltext http://www.mic-journal.no/PDF/2009/MIC-2009-3-6.pdf Past, Present and Future of Process Control at Xstrata Nikkelverk Hauge, T.A. Løkling, R. Haga, S. MIC celebrates its 30th anniversary in 2009 and Xstrata Nikkelverk celebrates its 100th anniversary in 2010. Both anniversaries are certainly worth celebrating and with this article Xstrata Nikkelverk salutes MIC at this special occasion. Xstrata Nikkelverk, Process Control, DCS,

oai:mic.2009.3.7 2010-03-20

eng Journal article 2009-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2009-3-7.asp Fulltext http://www.mic-journal.no/PDF/2009/MIC-2009-3-7.pdf Robot Control Overview: An Industrial Perspective Brogårdh, T. One key competence for robot manufacturers is robot control, defined as all the technologies needed to control the electromechanical system of an industrial robot. By means of modeling, identification, optimization, and model-based control it is possible to reduce robot cost, increase robot performance, and solve requirements from new automation concepts and new application processes. Model-based control, including kinematics error compensation, optimal servo reference- and feed-forward generation, and servo design, tuning, and scheduling, has meant a breakthrough for the use of robots in industry. Relying on this breakthrough, new automation concepts such as high performance multi robot collaboration and human robot collaboration can be introduced. Robot manufacturers can build robots with more compliant components and mechanical structures without loosing performance and robots can be used also in applications with very high performance requirements, e.g., in assembly, machining, and laser cutting. In the future it is expected that the importance of sensor control will increase, both with respect to sensors in the robot structure to increase the control performance of the robot itself and sensors outside the robot related to the applications and the automation systems. In this connection sensor fusion and learning functionalities will be needed together with the robot control for easy and intuitive installation, programming, and maintenance of industrial robots. Robotics, control, models, learning, sensors, identification, diagnosis, assembly,

oai:mic.2009.3.8 2010-03-20

eng Journal article 2009-07-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2009-3-8.asp Fulltext http://www.mic-journal.no/PDF/2009/MIC-2009-3-8.pdf Trends in Research and Publication: Science 2.0 and Open Access Breivik, Morten Hovland, Geir From, Pål Johan This paper considers current trends in academic research and publication, in particular as seen from the control community. The introduction of Web 2.0 applications for scientists and engineers is currently changing the way research is being conducted. In the near future, participants in the research community will be able to share ideas, data and results like never before. They will also be able to manage the rapidly increasing amount of scientific information much more effectively than today through collaborative efforts enabled by the new Internet tools. However, an important premise for such a development is the availability of research material. Many research results are currently shielded behind expensive subscription schemes that impede the sharing of information. At the same time, an increasing amount of research is being published through open access channels with unrestricted availability. Interestingly, recent studies show that such policies contribute to an increased number of citations compared to the pay-based alternatives. In sum, the parallel development of new tools for research collaboration and an increased access to research material may help spur a revolution in the way research is going to be conducted in the future. Web 2.0, Science 2.0, Open Access, Journal Ranking, Print On Demand,

oai:mic.2009.4.1 2010-03-20

eng Journal article 2009-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2009-4-1.asp Fulltext http://www.mic-journal.no/PDF/2009/MIC-2009-4-1.pdf Oxygen Effects in Anaerobic Digestion Botheju, Deshai Lie, Bernt Bakke, Rune Free oxygen effects in bio-gasification are not well known, apart from the common understanding of oxygen being toxic and inhibitory for anaerobic micro-organisms. Some studies have, however, revealed increased solubilisation of organic matter in the presence of some free oxygen in anaerobic digestion. This article analyses these counterbalancing phenomena with a mathematical modelling approach using the widely accepted biochemical model ADM 1. Aerobic oxidation of soluble carbon and inhibition of obligatory anaerobic organisms are modelled using standard saturation type kinetics. Biomass dependent first order hydrolysis kinetics is used to relate the increased hydrolysis rate with oxygen induced increase in biomass growth. The amended model, ADM 1-Ox (oxygen), has 25 state variables and 22 biochemical processes, presented in matrix form. The computer aided simulation tool AQUASIM 2.1 is used to simulate the developed model. Simulation predictions are evaluated against experimental data obtained using a laboratory batch test array comprising miniature anaerobic bio-reactors of 100 ml total volume each, operated under different initial air headspaces giving rise to the different oxygen loading conditions. The reactors were initially fed with a glucose solution and incubated at 35 Celsius, for 563 hours. Under the oxygen load conditions of 22, 44 and 88 mg/L, the ADM1-Ox model simulations predicted the experimental methane potentials quite adequately. Both the experimental data and the simulations suggest a linear reduction of methane potential with respect to the increase in oxygen load within this range. anaerobic digestion, ADM 1, modelling, oxygen,

oai:mic.2009.4.2 2010-03-20

eng Journal article 2009-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2009-4-2.asp Fulltext http://www.mic-journal.no/PDF/2009/MIC-2009-4-2.pdf A Bootstrap Subspace Identification Method: Comparing Methods for Closed Loop Subspace Identification by Monte Carlo Simulations Di Ruscio, David A novel promising bootstrap subspace system identification algorithm for both open and closed loop systems is presented. An outline of the SSARX algorithm by Jansson (2003) is given and a modified SSARX algorithm is presented. Some methods which are consistent for closed loop subspace system identification presented in the literature are discussed and compared to a recently published subspace algorithm which works for both open as well as for closed loop data, i.e., the DSR_e algorithm as well as the new bootstrap subspace method presented in this paper. Experimental comparisons are performed by Monte Carlo simulations. Subspace, Identification, Closed loop, Linear Systems, Kalman filter,

oai:mic.2009.4.3 2010-03-20

eng Journal article 2009-10-01 Norwegian Society of Automatic Control http://www.mic-journal.no/ABS/MIC-2009-4-3.asp Fulltext http://www.mic-journal.no/PDF/2009/MIC-2009-4-3.pdf A Rudimentary History of Dynamics Ross, Andrew This article presents a condensed overview of the development of dynamics from Ancient Greece through to the late 18th century. Its purpose is to bring an often neglected topic to the control community in as interesting a fashion as the author can achieve. History of science, dynamics, mechanics, kinematics, Newtonian equations,