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  • 1.
    Andersson, Magnus
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Svante
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Norrlöf, Mikael
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    A Simulation and Animation Tool for Studying Multivariable Control2002In: Proceedings of the 15th IFAC World Congress, 2002, p. 1432-1432Conference paper (Refereed)
    Abstract [en]

    A simulation and animation tool for education in multivariable control is presented. The purpose of the tool is to support studies of various aspects of multivariable dynamical systems and design of multivariable feedback control systems. Different ways to use this kind of tool in control education are also presented and discussed.

  • 2.
    Axelsson, Patrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Axehill, Daniel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Norrlöf, Mikael
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Controllability Aspects for Iterative Learning ControlManuscript (preprint) (Other academic)
    Abstract [en]

    This paper discusses the aspects of controllability in the iteration domain for systems that are controlled using iterative learning control (ILC). The focus is on controllability for a proposed state space model in the iteration domain and it relates to an assumption often used to prove convergence of ILC algorithms. It is shown that instead of investigating controllability it is more suitable to use the concept of target path controllability (TPC), where it is investigated if a system can follow a trajectory instead of the ability to control the system to an arbitrary point in the state space. Finally, a simulation study is performed to show how the ILC algorithm can be designed using the LQ-method, if the state space model in the iteration domain is output controllable. The LQ-method is compared to the standard norm-optimal ILC algorithm, where it is shown that the control error can be reduced significantly using the LQ-method compared to the norm-optimal approach.

  • 3.
    Axelsson, Patrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Axehill, Daniel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Norrlöf, Mikael
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Iterative Learning Control - From a Controllability Point of View2014In: Proceedings of Reglermöte 2014, 2014Conference paper (Other academic)
  • 4.
    Brannmark, Cecilia
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
    Palmer, Robert
    Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Cedersund, Gunnar
    Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
    Strålfors, Peter
    Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
    Mass and Information Feedbacks through Receptor Endocytosis Govern Insulin Signaling as Revealed Using a Parameter-free Modeling Framework2010In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 285, no 26, p. 20171-20179Article in journal (Refereed)
    Abstract [en]

    Insulin and other hormones control target cells through a network of signal-mediating molecules. Such networks are extremely complex due to multiple feedback loops in combination with redundancy, shared signal mediators, and cross-talk between signal pathways. We present a novel framework that integrates experimental work and mathematical modeling to quantitatively characterize the role and relation between coexisting submechanisms in complex signaling networks. The approach is independent of knowing or uniquely estimating model parameters because it only relies on (i) rejections and (ii) core predictions (uniquely identified properties in unidentifiable models). The power of our approach is demonstrated through numerous iterations between experiments, model-based data analyses, and theoretical predictions to characterize the relative role of co-existing feedbacks governing insulin signaling. We examined phosphorylation of the insulin receptor and insulin receptor substrate-1 and endocytosis of the receptor in response to various different experimental perturbations in primary human adipocytes. The analysis revealed that receptor endocytosis is necessary for two identified feedback mechanisms involving mass and information transfer, respectively. Experimental findings indicate that interfering with the feedback may substantially increase overall signaling strength, suggesting novel therapeutic targets for insulin resistance and type 2 diabetes. Because the central observations are present in other signaling networks, our results may indicate a general mechanism in hormonal control.

  • 5.
    Chen, Ke Wang
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Estimation of the Primary Current in a Saturated Transformer1991In: Proceedings of the 30th IEEE Conference on Decision and Control, 1991, p. 2363-2365 vol.3Conference paper (Refereed)
    Abstract [en]

    It is pointed out that, when a current in a power system is measured using a transformer, the measurement can be distorted by transformer saturation. The authors examine two methods of estimating the primary current from the secondary in the presence of saturation. The first is based on an extended Kalman filter, while the second is based on an off-line Gauss-Newton method

  • 6.
    Chen, Ke Wang
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Estimation of the Primary Current in a Saturated Transformer1991Report (Other academic)
    Abstract [en]

    It is pointed out that, when a current in a power system is measured using a transformer, the measurement can be distorted by transformer saturation. The authors examine two methods of estimating the primary current from the secondary in the presence of saturation. The first is based on an extended Kalman filter, while the second is based on an off-line Gauss-Newton method

  • 7.
    Edström, Krister
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Algorithmic, Physically based Mode Initialization when Simulating Hybrid Systems2002In: Proceedings of the Institution of mechanical engineers. Part I, journal of systems and control engineering, ISSN 0959-6518, E-ISSN 2041-3041, Vol. 216, no I1, p. 65-72Article in journal (Refereed)
    Abstract [en]

    In the simulation of hybrid systems, discontinuities can appear at mode changes. An algorithm is presented that gives initial values for the continuous state variables in a new mode. The algorithm is based on a switched bond graph representation of the system, and it handles discontinuities introduced by a changed number of state variables at a mode change. The algorithm is obtained by integrating the bond graph relations over the mode change and assuming that the physical variables are bounded. This gives a relation between the variables before and after the mode change. It is proved here that the equations for the new initial conditions are solvable. The algorithm is related to a singular perturbation theory by replacing the discontinuity by a fast continuous change. The action is considered of a single switch and the corresponding continuous change, tuned by a single parameter. By letting this parameter tend to zero, the same initial state values are achieved as those derived by the presented algorithm. The algorithm is also related to physical principles such as charge conservation.

  • 8.
    Einarsson, Valur
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Verification of Piecewise Linear Switched Systems using Abstractions1999Report (Other academic)
    Abstract [en]

    A modeling framework for the class of piecewise linear switched systems is presented. Methods for abstraction using conservative discrete approximations are introduced and model checking is used for verifying specifications. A fairly complex example is treated, the main result being that abstraction is a promising tool for fully automated verification.

  • 9.
    Fliess, M
    et al.
    Laboratoire des Signaux et Systemes, France.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    An Algebraic Approach to Linear and Nonlinear Control1993In: Essays on Control: Perspectives in the Theory and its Application / [ed] H. L. Trentelman and J. C. Willems, Boston ; Basel: Birkhäuser , 1993, p. 223--267Chapter in book (Refereed)
    Abstract [en]

    The analysis and design of control systems has been greatly influenced by the mathematical tools being used. Maxwell introduced linear differential equations in the 1860’s. Nyquist, Bode and others started the systematic use of tranfer functions, utilizing complex analysis in the 1930’s. Kalman brought forward state space analysis around 1960. For nonlinear systems, differential geometric concepts have been of great value recently. We will argue here that algebraic methods can be very useful for both linear and nonlinear systems. To give some motivation we will begin by looking at a few examples.

  • 10.
    Fliess, Michel
    et al.
    Laboratoire des Signaux et Systemes, France.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    An Algebraic Approach to Linear and Nonlinear Control1994Report (Other academic)
    Abstract [en]

    The analysis and design of control systems has been greatly influenced by the mathematical tools being used. Maxwell introduced linear differential equations in the 1860’s. Nyquist, Bode and others started the systematic use of tranfer functions, utilizing complex analysis in the 1930’s. Kalman brought forward state space analysis around 1960. For nonlinear systems, differential geometric concepts have been of great value recently. We will argue here that algebraic methods can be very useful for both linear and nonlinear systems. To give some motivation we will begin by looking at a few examples.

  • 11.
    Forsman, Krister
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Constructive Algebra and Control Theory1993In: Proceedings of the 1993 International Symposium on The Mathematical Theory of Networks and Systems, 1993, Vol. II, p. 149-152Conference paper (Refereed)
  • 12.
    Forsman, Krister
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Constructive Algebra and Control Theory1993Report (Other academic)
  • 13.
    Forsman, Krister
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gröbnes Bases: A New Tool in Nonlinear Control Theory1990Report (Other academic)
  • 14.
    Gerdin, Markus
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    On Identifiability of Object-Oriented Models2006In: Proceedings of the 14th IFAC Symposium on System Identification, 2006, p. 820-825Conference paper (Refereed)
    Abstract [en]

    When estimating unknown parameters, it is important that the model is identifiable so that the parameters can be estimated uniquely. For nonlinear differential-algebraic equation models with polynomial equations, a differential algebra approach to examine identifiability is available. This approach can be slow, so the present paper describes how this method can be modularized for object-oriented models. A characteristic set of equations is computed for components in model libraries, and stored together with the components. When an object-oriented model is built using such models, identifiability can be examined using the stored equations.

  • 15.
    Gerdin, Markus
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    On Identifiability of Object-Oriented Models2005Report (Other academic)
    Abstract [en]

    When estimating unknown parameters, it is important that the model is identifiable so that the parameters can be estimated uniquely. For nonlinear differential-algebraic equation models with polynomial equations, a differential algebra approach to examine identifiability is available. This approach can be slow, so the present paper describes how this method can be modularized for object-oriented models. A characteristic set of equations is computed for components in model libraries, and stored together with the components. When an object-oriented model is built using such models, identifiability can be examined using the stored equations.

  • 16.
    Gerdin, Markus
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Ljung, Lennart
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Global Identifiability of Complex Models, Constructed from Simple Submodels2007In: Modeling, Estimation and Control: Festschrift in Honor of Giorgio Picci on the Occasion of his Sixty-Fifth Birthday / [ed] Alessandro Chiuso, Stefano Pinzoni, Augusto Ferrante, Springer Berlin/Heidelberg, 2007, p. 123-133Chapter in book (Other academic)
    Abstract [en]

    It is a typical situation in modern modeling that a total model is built up from simpler submodels, or modules, for example residing in a model library. The total model could be quite complex, while the modules are well understood and analysed. A procedure to decide global parameter identifiability for such a collection of model equations of differential-algebraic nature is suggested. It is shown how to make use of the natural modularization of the model structure. Basically, global identifiability is obtained if and only if each module is identifiable, and the connecting signals can be retrieved from the external signals, without knowledge of the values of the parameters.

  • 17.
    Gerdin, Markus
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Ljung, Lennart
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Global Identifiability of Complex Models, Constructed from Simple Submodels2007Report (Other academic)
    Abstract [en]

    It is a typical situation in modern modeling that a total model is built up from simpler submodels, or modules, for example residing in a model library. The total model could be quite complex, while the modules are well understood and analysed. A procedure to decide global parameter identifiability for such a collection of model equations of differential-algebraic nature is suggested. It is shown how to make use of the natural modularization of the model structure. Basically, global identifiability is obtained if and only if each module is identifiable, and the connecting signals can be retrieved from the external signals, without knowledge of the values of the parameters.

  • 18.
    Gerdin, Markus
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Ljung, Lennart
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Parameter Estimation in Linear Differential-Algebraic Equations2003In: Proceedings of the 13th IFAC Symposium on System Identification, 2003, p. 1530-Conference paper (Refereed)
    Abstract [en]

    This report describes how parameter estimation can be performed in linear DAE systems. Both time domain and frequency domain identification are examined. The results are exemplified on a small system. A potential application for the algorithms is to make parameter estimation in models generated by a modeling language like Modelica.

  • 19.
    Gerdin, Markus
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Ljung, Lennart
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Parameter Estimation in Linear Differential-Algebraic Equations2003Report (Other academic)
    Abstract [en]

    This report describes how parameter estimation can be performed in linear DAE systems. Both time domain and frequency domain identification are examined. The results are exemplified on a small system. A potential application for the algorithms is to make parameter estimation in models generated by a modeling language like Modelica.

  • 20.
    Gerdin, Markus
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Ljung, Lennart
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Well-Posedness of Filtering Problems for Stochastic Linear DAE Models2005In: Proceedings of the 44th IEEE Conference on Decision and Control and European Control Conference, 2005, p. 350-355Conference paper (Refereed)
    Abstract [en]

    Modern modeling tools often give descriptor or DAE models, i.e., models consisting of a mixture of differential and algebraic relationships. The introduction of stochastic signals into such models in connection with filtering problems raises several questions of well-posedness. The main problem is that the system equations may contain hidden relationships affecting variables defined as white noise. The result might be that certain physical variables get infinite variance or contain formal differentiations of white noise. The paper gives conditions for well-posedness in terms of certain subspaces defined by the system matrices.

  • 21.
    Gerdin, Markus
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Ljung, Lennart
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Well-Posedness of Filtering Problems for Stochastic Linear DAE Models2005Report (Other academic)
    Abstract [en]

    Modern modeling tools often give descriptor or DAE models, i.e., models consisting of a mixture of differential and algebraic relationships. The introduction of stochastic signals into such models in connection with filtering problems raises several questions of well-posedness. The main problem is that the system equations may contain hidden relationships affecting variables defined as white noise. The result might be that certain physical variables get infinite variance or contain formal differentiations of white noise. The paper gives conditions for well-posedness in terms of certain subspaces defined by the system matrices.

  • 22.
    Gerdin, Markus
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Schön, Thomas
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gustafsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Ljung, Lennart
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    On Parameter and State Estimation for Linear Differential-Algebraic Equations2007Report (Other academic)
    Abstract [en]

    The current demand for more complex models has initiated a shift away from state-space models towards models described by differential-algebraic equations (DAEs). These models arise as the natural product of object-oriented modeling languages, such as Modelica. However, the mathematics of DAEs is somewhat more involved than the standard state-space theory. The aim of this work is to present a well-posed description of a linear stochastic differential-algebraic equation and more importantly explain how well-posed estimation problems can be formed. We will consider both the system identification problem and the state estimation problem. Besides providing the necessary theory we will also explain how the procedures can be implemented by means of efficient numerical methods.

  • 23.
    Gerdin, Markus
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Schön, Thomas
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gustafsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Ljung, Lennart
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    On Parameter and State Estimation for Linear Differential-Algebraic Equations2007In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 43, no 3, p. 416-425Article in journal (Refereed)
    Abstract [en]

    The current demand for more complex models has initiated a shift away from state-space models towards models described by differential-algebraic equations (DAEs). These models arise as the natural product of object-oriented modeling languages, such as Modelica. However, the mathematics of DAEs is somewhat more involved than the standard state-space theory. The aim of this work is to present a well-posed description of a linear stochastic differential-algebraic equation and more importantly explain how well-posed estimation problems can be formed. We will consider both the system identification problem and the state estimation problem. Besides providing the necessary theory we will also explain how the procedures can be implemented by means of efficient numerical methods.

  • 24.
    Germundsson, Roger
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    A Unified Constructive Study of Linear, Nonlinear and Discrete Event Systems1995Report (Other academic)
    Abstract [en]

    Starting from the behavioral point of view a system is defined by its set of behaviors. In discrete time this is a relation over D N and hence a very infinite object. A model is a relation over D N for some finite N that can be extended to a behavior. Furthermore properties of a system is defined in terms of its behavior. Starting from a constructive point of view we need to be able to represent and manipulate systems. A natural choice is to use some a constructive model, i.e. one that can be finitely represented and manipulated. We will consider four such classes of models: polynomial and linear relations over finite and infinite fields. There are a number of restrictions on the geometric (or behavioral) operations that are possible for each of these classes and still remain within the class. If we want to interpret our models as systems and analyze system properties, then several properties become impossible to compute. Some examples: The set of reachable states for a polynomial model over an infinite field is in general impossible to compute. It may converge to be fractal. The set of reacable states ik steps or less in a linear model cannot be represented as a linear set in general.

  • 25.
    Glad, S. T.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    A Differential Algebra Representation of the RGA2000Report (Other academic)
    Abstract [en]

    Extentions of the RGA (relative gain array) technique to nonlinear systems are considered. The steady-state properties are given by an array of nonlinear functions. It is shown that the corresponding dynamic description can be calculated using a reduction algorithm from differential algebra.

  • 26.
    Glad, S.T
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Extensions of the RGA Concept to Nonlinear Systems2000Report (Other academic)
    Abstract [en]

    Extentions of the RGA (relative gain array) technique to nonlinear systems are considered. The steady-state properties are given by an array of nonlinear functions. The high frequency properties are characterized by forming the conventional RGA of the decoupling matrix.

  • 27.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    A Differential Algebra Representation of the RGA2000In: Proceedings of the 14th International Symposium on Mathematical Theory of Networks and Systems, 2000, p. 169-178Conference paper (Refereed)
    Abstract [en]

    Extentions of the RGA (relative gain array) technique to nonlinear systems are considered. The steady-state properties are given by an array of nonlinear functions. It is shown that the corresponding dynamic description can be calculated using a reduction algorithm from differential algebra.

  • 28.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    An Algebraic Approach to Bang-Bang Control1995In: Proceedings of the 3rd European Control Conference, 1995, Vol. 4, p. 2892-2895Conference paper (Refereed)
  • 29.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    An Algebraic Approach to Bang-Bang Control1994Report (Other academic)
  • 30.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    An Algorithm for Nondifferentiable Optimization with Applications to Constrained Problems1980Report (Other academic)
  • 31.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Analysis of Actuator Cross Coupling in Aircraft1998In: Proceedings of the 1998 Conference on Mathematical Theory of Networks and Systems, 1998, p. 1019-1022Conference paper (Refereed)
    Abstract [en]

    When several control signals share the same physical actuators, actuator saturation has the effect of giving coupling between control loops which are otherwise decoupled. This effect occurs e.g. in aircraft control where the elevator and aileron functions often use the same physical control surfaces. The effect is particularly important when one of the loops is open loop unstable. The paper consider the effects on the stabilizable region of cross coupling with another control loop. To give further insight simple optimal control problems are considered.

  • 32.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Analysis of Actuator Cross Coupling in Aircraft1999Report (Other academic)
    Abstract [en]

    When several control signals share the same physical actuators, actuator saturation has the effect of giving coupling between control loops which are otherwise decoupled. This effect occurs e.g. in aircraft control where the elevator and aileron functions often use the same physical control surfaces. The effect is particularly important when one of the loops is open loop unstable. The paper consider the effects on the stabilizable region of cross coupling with another control loop. To give further insight simple optimal control problems are considered.

  • 33.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Computing the Settling Time for Nonlinear Step Responses2007In: Proceedings of the 7th IFAC Symposium on Nonlinear Control Systems, 2007, p. 119-122Conference paper (Refereed)
    Abstract [en]

    The settling time for the step response of a nonlinear system can be computed using the Poincaré-Dulac normal form. It is then possible to use a simple approximate formula, whose error can be estimated. The data needed can all be calculated from the leading coefficients of series expansions of the Poincaré-Dulac transformation and the equilibrium curve.

  • 34.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Deadbeat Control for Nonlinear Systems1988In: Analysis and Control of Nonlinear Systems / [ed] Christopher I. Byrnes, Clyde Martin, Richard Saeks, Amsterdam: North-Holland , 1988Chapter in book (Other academic)
  • 35.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Deadbeat Control for Nonlinear Systems1987Report (Other academic)
  • 36.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Dealing with Inequalities in Polynomial Models2012In: Proceedings of the 16th IFAC Symposium on System Identification, 2012, p. 936-940Conference paper (Refereed)
    Abstract [en]

    It is described how set membership identification and model rejection for polynomial models can be described using polynomial inequalities and inequations. Using difference algebra methods these problems can be reduced to a form based on so called autoreduced sets. It is shown that these descriptions generalize state space descriptions. It is also discussed how special forms of autoreduced sets can make calculations based on interval methods easier to implement.

  • 37.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Differential Algebraic Computation of Regulators1991Report (Other academic)
  • 38.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Differential Algebraic Modelling of Nonlinear Systems1990In: Realization and Modelling in System Theory: Proceedings of the International Symposium MTNS-89, Volume 1 / [ed] M. A. Kaashoek, J. H. van Schuppen, A. C. M. Ran, Boston ; Basel: Birkhäuser Verlag, 1990, p. 97-105Chapter in book (Other academic)
    Abstract [en]

    This paper discusses how the concepts of differential algebra can be used in the modelling of physical systems. In particular it is shown that the concepts of ranking and characteristic set can be used to give a structure to the set of physical equations. The characteristic set makes it easy to find the number of inputs and the order of the system. The question of observability can also be investigated using the characteristic set. In particular one can see that the order of an input output differential equation will be the same as the system order if and only if all variables are observable from the output.

  • 39.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Differential Algebraic Modelling of Nonlinear Systems1990Report (Other academic)
    Abstract [en]

    This paper discusses how the concepts of differential algebra can be used in the modelling of physical systems. In particular it is shown that the concepts of ranking and characteristic set can be used to give a structure to the set of physical equations. The characteristic set makes it easy to find the number of inputs and the order of the system. The question of observability can also be investigated using the characteristic set. In particular one can see that the order of an input output differential equation will be the same as the system order if and only if all variables are observable from the output.

  • 40.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Differential Algebraic Modelling of Nonlinear Systems1989Report (Other academic)
    Abstract [en]

    This paper discusses how the concepts of differential algebra can be used in the modelling of physical systems. In particular it is shown that the concepts of ranking and characteristic set can be used to give a structure to the set of physical equations. The characteristic set makes it easy to find the number of inputs and the order of the system. The question of observability can also be investigated using the characteristic set. In particular one can see that the order of an input output differential equation will be the same as the system order if and only if all variables are observable from the output.

  • 41.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Extensions of the RGA Concept to Nonlinear Systems1999In: Proceedings of the 5th European Control Conference, 1999, p. 332-Conference paper (Refereed)
    Abstract [en]

    Extentions of the RGA (relative gain array) technique to nonlinear systems are considered. The steady-state properties are given by an array of nonlinear functions. The high frequency properties are characterized by forming the conventional RGA of the decoupling matrix.

  • 42.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Generalized State Space Descriptions and Digital Implementation1992Report (Other academic)
  • 43.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Generalized State Space Representations and Digital Implementation1992In: Proceedings of the 2nd IFAC Symposium on Control Systems Design, 1992, p. 398-401Conference paper (Refereed)
  • 44.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Harmonic Balancing using a Volterra Input Output Description1990Report (Other academic)
  • 45.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Implementing Ritt's Algorithm of Differential Algebra1992In: Proceedings of the 2nd IFAC Symposium on Control Systems Design, 1992, p. 610-614Conference paper (Refereed)
  • 46.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Implementing Ritt's Algorithm of Differential Algebra1992Report (Other academic)
  • 47.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Input Output Representations from Characteristic Sets1991In: Proceedings of the 30th IEEE Conference on Decision and Control, 1991, p. 726-730 vol.1Conference paper (Refereed)
    Abstract [en]

    The authors present an algorithm for computation of input-output descriptions. Characteristic sets can be considered as generalization of state space descriptions. Input-output descriptions can also be regarded as characteristic sets under a different ranking. This forms the basis of the differential algebraic algorithm for computation of input-output relations. For polynomial state-space descriptions the calculations are easier than the general computations of characteristic sets.

  • 48.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Input Output Representations from Characteristic Sets1991Report (Other academic)
    Abstract [en]

    The authors present an algorithm for computation of input-output descriptions. Characteristic sets can be considered as generalization of state space descriptions. Input-output descriptions can also be regarded as characteristic sets under a different ranking. This forms the basis of the differential algebraic algorithm for computation of input-output relations. For polynomial state-space descriptions the calculations are easier than the general computations of characteristic sets.

  • 49.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Nonlinear Control Theory1994Report (Other academic)
  • 50.
    Glad, Torkel
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Nonlinear Control Theory, Preliminary Version1990Report (Other academic)
1234 1 - 50 of 182
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