| 1. |
- Andersson, Magnus, et al.
(författare)
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A Simulation and Animation Tool for Studying Multivariable Control
- 2002
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Ingår i: Proceedings of the 15th IFAC World Congress. - 9783902661746 ; , s. 1432-1432
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 2. |
- Glad, Torkel, 1947-, et al.
(författare)
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The Gröbner Basis Method in Control Theory : An Overview
- 2002
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Ingår i: Proceedings of the 15th IFAC World Congress. - 9783902661746 ; , s. 906-906
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Konferensbidrag (refereegranskat)abstract
- The paper discusses the usefulness of Gröbner bases methods in a variety of control problems for a class of polynomial systems. Polynomial systems are described by difference or differential equations in which the transition map or vectorfield are polynomials. Gröbner bases methods are useful in both the analysis and the design of polynomial control systems.
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| 3. |
- Gustafsson, Fredrik, et al.
(författare)
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Power Control in Wireless Communications Networks - from a Control Theory Perspective
- 2002
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Ingår i: Proceedings of the 15th IFAC World Congress. - Linköping : Linköping University Electronic Press. - 9783902661746 ; , s. 935-935
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Konferensbidrag (refereegranskat)abstract
- The global communications systems critically relyon control algorithms of various kinds. In wireless communications systems, power control algorithms play an important role for efficient resource utilization. This survey article discusses relevant aspects of power control with emphasis on practical issues, using an automatic control framework. Generally, power control of each connection is distributedly implemented as cascade control, with an inner loop to compensate for fast variations and an outerloop focusing on longer term statistics. These control loops are interrelated via complex connections, which affect important issues such as capacity, load and stability. Therefore, both local and global properties are important. The concepts and algorithms are illustrated by simple examples and simulations.
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| 4. |
- Gustafsson, Fredrik
(författare)
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Stochastic Fault Diagnosability in Parity Spaces
- 2002
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Ingår i: Proceedings of the 15th IFAC World Congress. - 9783902661746 ; , s. 736-736
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Konferensbidrag (refereegranskat)abstract
- We here analyze the parity space approach to fault detection and isolation in a stochastic setting. Using a state space model with both deterministic and stochastic unmeasurable inputs we show a formal relationship between the Kalman filter and the parity space. Based on a statistical fault detection and diagnosis algorithm, the probability for incorrect diagnosis is computed explicitly, given that only a single fault with known time profile has occurred. An example illustrates how the matrix of diagnosis probabilities can be used as a design tool for performance optimization with respect to, for instance, design variables and sensor placement and quality.
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| 5. |
- Hansson, Anders, et al.
(författare)
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Efficient Solution of Second Order Cone Program for Model Predictive Control
- 2002
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Ingår i: Proceedings of the 15th IFAC World Congress. - Linköping : Linköping University Electronic Press. - 9783902661746 ; , s. 296-296
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Konferensbidrag (refereegranskat)abstract
- In this paper it is shown how to efficiently solve an optimal control problem with applications to model predictive control. The objective is quadratic and the constraints can be both linear and quadratic. The key to an efficient implementation is to rewrite the optimization problem as a second order cone program. This can be done in many different ways. However, done carefully, it is possible to use both very efficient scalings as well as Riccati recursions for computing the search directions.
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| 6. |
- Hansson, Anders, et al.
(författare)
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On Methods for Gradient Estimation in IFT for MIMO Systems
- 2002
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Ingår i: Proceedings of 15th IFAC World Congress. - 9783902661746 ; , s. 1047-1047
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Konferensbidrag (refereegranskat)abstract
- Iterative feedback tuning (IFT) is a model free control tuning method using closed loop experiments. For single-input single-output (SISO) systems only 2 or 3, depending on the controller structure, closed loop experiments are required. However for multivariable systems the number of experiments increase to a maximum of 1 + m times p, where m times p is the dimension of the controller. In this contribution several methods are proposed to reduce the experimental time by approximating the gradient of the cost function. The local convergence for a method which uses the same technique as in IFT for SISO systems is analyzed. It is shown that even if there are commutation errors due to the approximation method, the numerical optimization may still converge to the true optimum.
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| 7. |
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| 8. |
- Lind, Ingela
(författare)
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Regressor Selection with the Analysis of Variance Method
- 2002
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Ingår i: Proceedings of the 15th IFAC World Congress. - Linköping : Linköping University Electronic Press. - 9783902661746 ; , s. 428-428
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Konferensbidrag (refereegranskat)abstract
- Identification of non-linear finite impulse response (N-FIR) models is studied. In particular the selection of model structure, i.e., to find the best regressors, is examined.In this report it is shown that a statistical method, the analysis of variance, is a better alternative than exhaustive search among all possible regressors, in the identification of the structure of non-linear FIR-models. The method is evaluated for different conditions on the input signal to the system. The results will serve as a foundation for the extension of the ideas to non-linear autoregressive processes.
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| 9. |
- Ljung, Lennart, 1946-, et al.
(författare)
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Asymptotically Optimal Smoothing of Averaged LMS for Regression Parameter Tracking
- 2002
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Ingår i: Proceedings of the 15th IFAC Congress. - 9783902661746 ; , s. 436-436
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Konferensbidrag (refereegranskat)abstract
- The sequence of estimates formed by the LMS algorithm for a standard linear regression estimation problem is considered. It is known since earlier that smoothing these estimates by simple averaging will lead to, asymptotically, the recursive least squares algorithm. In thi spaper it is first shown that smoothing the LMS estimates using amatrix updating will lead to smoothed estimates with optimal tracking properties, also in the case the true parameters are slowly changing as a random walk. The choice of smoothing matrix should be tailored to theproperties of the random walk. Second, it is shown that the same accuracy can be obtained also for a modified algorithm, SLAMS, which is based on averages and requires much less computations.
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| 10. |
- Löfberg, Johan
(författare)
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Minimax MPC for Systems with Uncertain Input Gain
- 2002
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Ingår i: Proceedings of the 15th IFAC World Congress. - 9783902661746 ; , s. 614-614
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Konferensbidrag (refereegranskat)abstract
- Robust synthesis is one of the remaining challenges in model predictive control (MPC). One way to robustify an MPC controller is to formulate a minimax problem, i.e., optimize a worst-case performance measure. For systems modeled with an uncertain gain, there are many results available. Typically, the minimax formulations have given intractable problems, or unorthodox performance measures have been used to obtain tractable problems. In this paper, we show how the standard quadratic performance measure can be used in a computationally tractable minimax MPC controller. The controller is developed in a linear matrix inequality framework that easily allows extensions and generalizations.
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| 11. |
- Löfberg, Johan, 1974-
(författare)
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Towards Joint State Estimation and Control in Minimax MPC
- 2002
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Ingår i: Proceedings of the 15th IFAC World Congress. - 9783902661746 ; , s. 612-612
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Konferensbidrag (refereegranskat)abstract
- A new approach to minimax MPC for systems with bounded external system disturbances and measurement errors is introduced. It is shown that joint deterministic state estimation and minimax MPC can be written as an optimization problem with linear and quadratic matrix inequalities. By linearizing the quadratic matrix inequality, a semidefinite program is obtained. A simulation study indicates that solving the joint problem can improve performance
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| 12. |
- Norrlöf, Mikael, 1971-, et al.
(författare)
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A General Framework for Iterative Learning Control
- 2002
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Ingår i: Proceedings of the 15th IFAC World Congress. - Linköping : Linköping University Electronic Press. - 9783902661746 ; , s. 224-224
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Konferensbidrag (refereegranskat)abstract
- In this contribution we place ILC in the realm of numerical optimization. This clarifies the role played by the design variables and how they affect e.g. convergence properties. We give a model based interpretation of these design variables and also a sufficient condition for convergence of ILC which is similar in spirit to the sufficient and necessary condition previously derived for linear systems. This condition shows that the desired performance has to be traded against modelling accuracy. Finally, one of the main benefits of ILC when non-minimum phase systems are concerned, the possibility of non-causal control, is given a comprehensive coverage.
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| 13. |
- Norrlöf, Mikael, 1971-, et al.
(författare)
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Disturbance Aspects of High Order Iterative Learning Control
- 2002
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Ingår i: Proceedings of the 15th IFAC World Congress. - Linköping : Linköping University Electronic Press. - 9783902661746 ; , s. 986-986
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Konferensbidrag (refereegranskat)abstract
- Some initial results on the disturbance properties of high order iterative learning control (ILC) algorithms are presented. Of particular interest is to investigate how high order ILC algorithms cope with measurement and load disturbances of different character. Some results are obtained by assuming statistical properties of the involved disturbances and deriving equations for the covariance matrix of the control error vector. The results are illustrated by analytic derivation of the covariance matrix for a second order ILC algorithm with a particular choice of design variables.
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| 14. |
- Norrlöf, Mikael, 1971-, et al.
(författare)
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Modeling and Identification of a Mechanical Industrial Manipulator
- 2002
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Ingår i: Proceedings of the 15th IFAC World Congress. - Linköping : Linköping University Electronic Press. - 9783902661746 ; , s. 852-852, s. 250-255
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This paper covers modeling and identification of one joint of an industrial robot manipulator including flexibilities. It is shown how models can be built in the Modelica graphical environment and how these models can be transformed into a mathematical state space description which directly can be used for identification. A motivation to use linear models for modeling of the robot arm is given. This includes an analysis of the nonlinearities in the input/output data from the actual robot using a special kind of input signal. Identification and validation of the physically parameterized models are also covered.
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| 15. |
- Roll, Jacob
(författare)
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Robust Verification of Piecewise Affine Systems
- 2002
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Ingår i: Proceedings of the 15th IFAC World Congress. - 9783902661746 ; , s. 221-221
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Konferensbidrag (refereegranskat)abstract
- Piecewise affine systems is an important class of hybrid systems. They consist of several affine dynamic subsystems, between which switchings occur at different occasions. In this paper, a verification method for piecewise affine systems is considered, and a method to determine how sensitive the verified properties are to changes in the dynamics and the locations of the switching surfaces is proposed. This information can then be used for robustness analysis or control design.
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| 16. |
- Tjärnström, Fredrik
(författare)
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Variance Aspects of L2 Model Reduction when Undermodeling - the Output Error Case
- 2002
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Ingår i: Proceedings of the 15th IFAC World Congress. - Linköping : Linköping University Electronic Press. - 9783902661746 ; , s. 453-453
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Konferensbidrag (refereegranskat)abstract
- In this contribution, variance properties of L2 model reduction are studied. That is, given an estimated model of high order we study the resulting variance of an L2 reduced approximation. The main result of the paper is showing that estimating a low order output error (OE) model via L2 model reduction of a high order model gives a smaller variance compared to estimating a low order model directly from data in the case of undermodeling. This has previously been shown to hold for FIR (Finite Impulse Response) models, but is in this paper extended to general linear OE models.
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