| 1. |
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| 2. |
- Barros, P R, et al.
(författare)
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Frequency domain sensitivity shaping in pole placement control
- 1998
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Konferensbidrag (refereegranskat)abstract
- In this paper the frequency domain sensitivity shaping of pole placement controllers is discussed. The sensitivity function is shaped in order to improve robustness and disturbance attenuation, and it is done with the use of controller overparametrization. A design example shows the capabilities of the method. The computation is done by a weighted least squares procedure which is suitable for adaptive control.
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| 3. |
- Barros, P. R., et al.
(författare)
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Frequency domain sensitivity shaping using overparametrized controllers
- 1997
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Ingår i: IEEE Xplore : Proceedings of the 36th IEEE Conference on Decision and Control - Proceedings of the 36th IEEE Conference on Decision and Control. - 0780341872 ; , s. 2716-2721
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Konferensbidrag (refereegranskat)abstract
- A frequency domain, weighted least squares, sensitivity function shaping procedure is presented. Pole placement is used as the basic servo design procedure. Controller overparametrization gives the degree of freedom for shaping the sensitivity function. A benchmark design example shows the capabilities of the method. The computation is simple making the design suitable for adaptive control.
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| 4. |
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| 5. |
- Li, Zheng, et al.
(författare)
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Minimum Variance Prediction for Linear Time-Varying Systems
- 1997
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Ingår i: Automatica. - 0005-1098. ; 33:4, s. 607-618
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Tidskriftsartikel (refereegranskat)abstract
- A minimum variance predictor is developed using pseudocommutation for linear time-varying systems described by an autoregressive moving average model.
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| 6. |
- Lindoff, Bengt, et al.
(författare)
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Analysis of Approximations to Dual Control
- 1999
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Ingår i: International Journal of Adaptive Control and Signal Processing. - 0890-6327. ; 13, s. 593-620
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Tidskriftsartikel (refereegranskat)abstract
- The dual control problem for time-varying or non-linear systems is inherently analytically and computationally untractable due to the demand of alternating minimizations and mean value computations. Hence, it has to be approached using approximations leading to suboptimal dual control. The core of the successful approximative controller is its ability to be able to consider future changes in the development of the parameters. This paper presents an analysis of the dual-control concept, and a comparison between a number of suboptimal controllers. The analytical comparisons are based on a reformulation of the dual-control problem. The reformulation makes it possible to interpret and understand the nature of the different approximations to dual control, in particular the Adaptive Predictive Controller (APC) and the Active Suboptimal Dual Controller (ASOD). Furthermore, it makes the origin of the computational problems encountered more clear, and suggests new alternatives for approximation. The analysis is carried through on relatively simple examples and is illustrated with simulations. The performance of the controllers when applied to more complicated time-varying systems is illustrated with simulations as well.
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| 7. |
- Lindoff, Bengt, et al.
(författare)
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Analysis of suboptimal dual control
- 1998
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Konferensbidrag (refereegranskat)abstract
- A reformulation of the dual control problem makes it possible to interpret and understand the nature of different approximations to dual control, in particular the Adaptive Predictive Controller (APC) and the Active Suboptimal Dual Controller (ASOD). The analysis makes the origin of the computational problems more clear, and suggests new alternatives for approximations.
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| 8. |
- Nilsson, Johan, et al.
(författare)
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Some Topics in Real-time Control
- 1998
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Ingår i: IEEE Xplore : Proceedings of the 1998 American Control Conference. ACC - Proceedings of the 1998 American Control Conference. ACC. - 0780345304
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Konferensbidrag (refereegranskat)abstract
- This paper discusses some problems that can arise in distributed real-time control systems, for instance, sampling- interval jitter, timeout, and asynchronous loops.
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| 9. |
- Nilsson, Johan, et al.
(författare)
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Stochastic Analysis and Control of Real-Time Systems with Random Time Delays
- 1996
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Ingår i: IFAC Proceedings Volumes. ; 29
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Konferensbidrag (refereegranskat)abstract
- The paper discusses modeling and analysis of real-time systems subject to random time delays in the communication network. A new method for analysis of existing schemes is presented. The method is used to evaluate different suggested schemes from the literature. A new scheme for handling the random time delays is then developed and successfully compared with previous schems. The new scheme is
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| 10. |
- Nilsson, Johan, et al.
(författare)
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Stochastic Analysis and Control of Real-Time Systems with Random Time Delays
- 1998
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Ingår i: Automatica. - 0005-1098. ; 34:1, s. 57-64
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Tidskriftsartikel (refereegranskat)abstract
- The paper discusses modeling and analysis of real-time systems subject to random time delays in the communication network. A new method for analysis of different control schemes is presented. The method is used to evaluate different suggested schemes from the literature. A new scheme, using so called timestamps, for handling the random time delays is then developed and successfully compared with previous schemes. The new scheme is based on stochastic control theory and a separation property is shown to hold for the optimal controller.
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| 11. |
- Nilsson, Johan, et al.
(författare)
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Timing Problems in Real-Time Systems
- 1997
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Konferensbidrag (refereegranskat)abstract
- The article describes and analyzes how random time delays effect control loops that are closed over a communication network. Analysis as well as LQG-design are presented. The optimal controller is using timestamps to determine the timedelay between the sensor and the controller.
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| 12. |
- Pedersen, Lars Malcolm, et al.
(författare)
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Multivariable controller design for hot rolling mill
- 1998
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Ingår i: IEEE Trans. on Control Systems Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 1063-6536. ; 6:2, s. 304-312
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a controller design for a hot rolling mill. The main purpose of the algorithm is to improve the control of the cross-width thickness profile of the plates. This is obtained by designing a controller which makes independent thickness control possible at the two sides of the rolling mill. This is obtained by first linearizing the positioning systems using feedback linearization and then using linear quadratic eigenspace design on the linearized multivariable system. Integral control is included to ensure zero stationary thickness error. The design is done using derived dynamical multivariabl models. To ensure that the design is stable, the stability of the system is investigated using the small gain theorem. The performance of the controller is evaluated using models estimated from data from the hot plate mill at The Danish Steel Works Ltd.
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| 13. |
- Pedersen, Lars Malcolm, et al.
(författare)
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Multivariable Controller Design for Hot Rolling Mill
- 1996
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Ingår i: IFAC Proceedings Volumes. ; 29:1
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Konferensbidrag (refereegranskat)abstract
- This paper concerns the controller design for the hot rolling mill at the Danish Steel Works Ltd. The design is done using derived dynamical multivariable models. The main objective of the design is to separate the two sides of the rolling mill. This is obtained by first linearizing the positioning system using feedback linearization and then using eigenspace design on the linearized multivariable system. To ensure that the design is stable, the stability of the system is investigated using the small gain theorem. The performance of the controller is evaluated using estimated models based on data from the plate mill.
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| 14. |
- Pedersen, Lars Malcolm, et al.
(författare)
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On the reheat furnace control problem
- 1998
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Ingår i: IEEE Xplore : Proceedings of the 1998 American Control Conference. ACC - Proceedings of the 1998 American Control Conference. ACC. - 0780345304
-
Konferensbidrag (refereegranskat)abstract
- The purpose of this paper is to develop a model and control algorithm for the slab temperature control problem, which is the control of a number of steel blocks (slabs) passing through a furnace burner zone. The slab temperature is controlled by varying the zone temperatrure. First a model for a single slab passing through the furnace is developed and the parameters are estimated. Data from the reheat furnace no. 2 at The Danish Steel Work Ltd. is used for the identification. Based on the slingle slab model a model for all slabs in a burner zone is constructed. The controllability of this model is analyzed and it is concluded that problems can arise if the temperature of two or more slabs are equal. A quadratic error function for the slab temperature is defined. From this error function and the constructed model a nonlinear controller is designed to minimize the vlaue of the error function. The stability of the control law is analyzed and it is concluded that the controlled system is stable.
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| 15. |
- Pedersen, Lars Malcolm, et al.
(författare)
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Optimization of Plate Thickness Controller
- 1998
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Konferensbidrag (refereegranskat)abstract
- The purpose of this paper is to describe the optimization of the thickness control system on the hot rolling mill at The Danish Steel Work Ltd. The optimization is done by replacing the existing linear analog thickness controller with a nonlinear digital controller.
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| 16. |
- Pedersen, Lars Malcolm, et al.
(författare)
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Thickness control for a plate mill
- 1998
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Ingår i: IFAC Proceedings Volumes : 9th IFAC Symposium on Automation in Mining, Mineral and Metal Processing (MMM 98) - 9th IFAC Symposium on Automation in Mining, Mineral and Metal Processing (MMM 98). ; 21:23, s. 331-336
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Konferensbidrag (refereegranskat)abstract
- The purpose of this paper is to describe the design of a multivariable control law for a hot plate mill. The design is performed on models adapted to the plate mill at The Danish Steel Work Ltd. The model for the rolling mill is divided into nonlinear models for the hydraulic systems performing the thickness control and a multivariable linear model for the rolling stand. The parameters of the models are found using measurements from the rolling mill at The Danish Steel Work Ltd. Most of the measurements are collected during rolling, but plate thickness measurements are performed after rolling using special equipment. In general, good agreement is obtained between measurements and model outputs. The multivariable nonlinaer model is used for designing a multivarialbe thickness control law which can be seen as an unified approach to control mean thickness and plate wedge. The result is a second order nonlinear controller with rolling forces and roll positions as inputs and control signal to the servo valves as outputs. Since it is not possible to implement the multivariable control law for the time being, the multivariable control law is simplified with the purpose of using it as a basis for an optimization of the existing thickness control equipment at The Danish Steel Works Ltd. This optimization can be seen as the first step in the practical verification of the multivariable control law.
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| 17. |
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| 18. |
- Savaresi, Sergio, et al.
(författare)
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Robust Narrow-Band Disturbance Rejection Using Overparameterized Pole-Assignment Control
- 1996
-
Konferensbidrag (refereegranskat)abstract
- In this work the problem of designing feedback controllers for the rejection of narrow-band disturbances is considered. The design technique proposed herein is based upon a well-suited overparameterization of a standard model-based minimum-variance controller; the extra-degrees-of-freedom so introduced are used to improve the performence of the basic controller. In particular, the problem of improving the robustness of the system, when the time delay of the system is subject to uncertainties, is considered, and an innovative solution proposed.
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| 19. |
- Savaresi, Sergio, et al.
(författare)
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Robust Narrow-Band Disturbances Rejection Using Overparametrized Pole-Assignment Control
- 1995
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this work the problem of designing feedback controllers for the rejection of narrow-band disturbances is considered. The design technique proposed herein is based upon a well-suited overparameterization of a standard model-based minimum-variance controller; the extra-degrees-of-freedom so introduced are used to improve the performence of the basic controller. In particular, the problem of improving the robustness of the system, when the time delay of the system is subject to uncertainties, is considered, and an innovative solution proposed.
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| 20. |
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| 21. |
-
The Åström Symposium on Control
- 1999
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Samlingsverk (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
- This book commemorates the 65th birthday of Karl Johan Åström, who is professor in Automatic Control at Lund Institute of Technology. Karl Johan Åström is one of the leading researchers of the world in automatic control. The contributions are chosen to illustrate some of the areas where Karl Johan Åström has been active in his research. The idea of the papers is also to point out new directions within the different fields. The ten contributions are written by well-known researchers in automatic control from all over the world. The topics includes modeling, stochastic control, identification, adaptation, robustness, nonlinearities, and applications. The papers in the book were presented at the Åström Symposium on Control in Lund, August 28, 1999, by Roger Brockett, John Doyle, Guy Dumont, Katsuhisa Furuta Graham Goodwin, Alberto Isidori, P. R. Kumar, Lennart Ljung, Richard Murray, M. Vidyasagar.
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| 22. |
- Wittenmark, Björn
(författare)
-
A survey of adaptive control applicatins
- 1997
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Ingår i: IEEE Industry Applications Society Dynamic Modeling Control Applications for Industry Workshop.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The paper gives examples of industrial adaptive controllers and industrial applications of adaptive control. Adaptive control algorithms are found in single-loop controllers as well as in distributed control systems. Several commercial systems are available today. The given applications are mainly from the process control area. Adaptive control has many good aspects, but it also requires a good understanding of the underlying ideas and potential problems to make a good application.
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| 23. |
- Wittenmark, Björn
(författare)
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Adaptive Dual Control Methods: An Overview
- 1995
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Ingår i: IFAC Proceedings Volumes. ; 28:13
-
Konferensbidrag (refereegranskat)abstract
- This paper gives an overview of different techniques for solving the dual control problem. The optimal solution can quite straightforwardly be characterized. The solution is, however, numerically demanding. A large number of suboptimal dual controllers have been developed over the years and the paper gives an overview and discussion of different approaches.
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| 24. |
- Wittenmark, Björn, et al.
(författare)
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Adaptive extremal control
- 1995
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Ingår i: Proceedings of 1995 34th IEEE Conference on Decision and Control.
-
Konferensbidrag (refereegranskat)abstract
- In this paper extrema1 control of a simple nonlinear stochastic system is analyzed. The process is modeled as a generalized Hammerstein model. Different problem formulations are discussed and the performances of the resulting nonlinear adaptive controllers are investigated. The adaptive controllers are based on on-line estimation of the parameters of the process and the certainty equivalence principle.
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| 25. |
- Wittenmark, Björn, et al.
(författare)
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Analysis of time delays in synchronous and asynchronous control loops
- 1998
-
Ingår i: IEEE Xplore : Proceedings of the 37th IEEE Conference on Decision and Control - Proceedings of the 37th IEEE Conference on Decision and Control.
-
Konferensbidrag (refereegranskat)abstract
- In this paper we describe how to determine the time delays caused by synchronous and asynchronous control loops. These time delays can vary in a quite irregular way and can cause problems for the control loops closed over a communication network of, for instance, field-buses. Different setups allowing an arbitrary number of communication layers are analyzed. The theoretical derivations are illustrated with a simple, although realistic, example.
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| 26. |
- Wittenmark, Björn
(författare)
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Datorstyrning
- 1996
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Ingår i: Nationalencyklopedin (NE.se).
-
Bokkapitel (populärvet., debatt m.m.)
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| 27. |
- Wittenmark, Björn, et al.
(författare)
-
Development of Advanced Furnace Control Algorithm
- 1999
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Ingår i: Steel Technology International. - 0953-2412. ; , s. 149-152
-
Tidskriftsartikel (refereegranskat)abstract
- In the continuous work on improving product quality and reducing energy consumption at The Danish Steel Works Ltd. the importance of optimal furnace operation has been recognised in many different contexts. Therefore a joint project with the Department of Automatic Control at Lund Institute of Technology has been started with the purpose of developing a novel slab temperature control algorithm for the reheat furnace control system. The article describes the results of this work so far by giving a short description of the ideas behind the new algorithm and presenting simulations where the peerformance of the new algorithm is compared to the performance of a conventional PI-controller. The model for the simulations is found from data collected from one of the reheat furnaces on The Danish Steel Works Ltd. The simulations show that the new algorithm is able to reduce the standard deviation from the final temperature with more than 15% compared to the temperature deviation obtained with the PI-control algorithm.
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| 28. |
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| 29. |
- Wittenmark, Björn, et al.
(författare)
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Dynamic pictures and interactive learning
- 1998
-
Ingår i: Control Systems Magazine. - : Institute of Electrical and Electronics Engineers (IEEE). - 0272-1708 .- 1066-033X .- 1941-000X. ; 18:3, s. 26-32
-
Tidskriftsartikel (refereegranskat)abstract
- The paper presents interactive learning tools used in courses in automatic control at Lund Institute of Technology. The learning tools are aimed at improving the understanding of and intuition for the abstract parts of the control courses. The paper presents dynamic interactive modules for a course in sampled-data systems. The tools are implemented in Matlab and used over the Internet.
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| 30. |
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| 31. |
- Wittenmark, Björn, et al.
(författare)
-
Robust Adaptive Control Based on Frequency Domain Analysis
- 1995
-
Konferensbidrag (refereegranskat)abstract
- Adaptive controllers are traditionally based on the principle of separation of estimation and control. Many design methods can be interpreted as pole-placement design. One drawback with this approach is that the controllers often are of the same order as the order of the process to be controlled. In this paper an adaptive controller based on a frequency domain method is presented. The idea is to obtain robustness by getting a good model of the process over a wide frequency range. This is done by estimating points of the Nyquist curve of the open loop system. The estimation is done using a bank of bandpass filters. An approximation method is then used to design low order controllers. Especially the startup procedure and modifications of the desired closed loop bandwidth are discussed. Through analysis of the sensitivity function we discuss how it is possible to increase the robustness of the closed loop system.
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| 32. |
- Wittenmark, Björn, et al.
(författare)
-
Self-tuning Regulators
- 1998
-
Ingår i: Encyclopedia of Electrical and Electronics Engineering.
-
Bokkapitel (refereegranskat)abstract
- A self-tuning regulator (STR) is a controller that automatically finds its parameters in the control law. Another name or synonym is self-adjusting controllers. The self-tuning regulators is a class of adaptive controllers which is used when it is assumed that the process to be controlled has constant but unknown parameters. However, the self-tuning regulators can also be used in an adaptive context.
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| 33. |
- Wittenmark, Björn
(författare)
-
Tillämpningar av adaptiv reglering
- 1996
-
Konferensbidrag (refereegranskat)abstract
- The paper describes different ways of using adaptive control in industrial applications. Many practical issues must, however, be considered when implementing an adaptive control algorithm. There is a large discrepancy between simulation or academic algorithms and practical algorithms. Several applications an case studies are presented and the advantages of adaptive control are discussed.
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| 34. |
- Wittenmark, Björn, et al.
(författare)
-
Timing Problems in Real-Time Control Systems
- 1995
-
Ingår i: <em>Proceedings of the 1995 American Control Conference</em>. ; , s. 2000-2004-- Vol.3
-
Konferensbidrag (refereegranskat)abstract
- The paper formulates and discusses timing problems in real-time systems. Different ways to eliminate the effects of communication delays are considered.
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| 35. |
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| 36. |
- Åström, Karl Johan, et al.
(författare)
-
A Survey of Adaptive Control Applications
- 1995
-
Ingår i: Proceedings of 1995 34th IEEE Conference on Decision and Control. - 0780326857
-
Konferensbidrag (refereegranskat)abstract
- This paper gives examples of industrial adaptive controllers and of true industrial applications of adaptive control. Adaptive control algorithms are found in single-loop controllers as well as in distributed control systems. The applications are from a wide range of industries, from process control to engine control in cars.
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| 37. |
- Åström, Karl Johan, et al.
(författare)
-
Adaptive Control (2 ed.)
- 1995
-
Bok (övrigt vetenskapligt/konstnärligt)abstract
- Introduces theoretical and practical aspects of adaptive control. Starting with a broad overview, the text explores real-time estimation, self-tuning regulators and model-reference adaptive systems, stochastic adaptive control, and automatic tuning of regulators. Additional topics include gain scheduling, robust high-gain control and self-oscillating controllers, and suggestions for implementing adaptive controllers. Concluding chapters feature a summary of applications and a brief review of additional areas closely related to adaptive control.
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| 38. |
- Åström, Karl Johan, et al.
(författare)
-
Computer-controlled systems : theory and design (3 ed.)
- 1997
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Practically all modern control systems are based upon microprocessors and complex microcontrollers that yield high performance and functionality. This volume focuses on the design of computer-controlled systems, featuring computational tools that can be applied directly and are explained with simple paper-and-pencil calculations. The use of computational tools is balanced by a strong emphasis on control system principles and ideas. Extensive pedagogical aids include worked examples, MATLAB macros, and a solutions manual. The initial chapter presents a broad outline of computer-controlled systems, followed by a computer-oriented view based on the behavior of the system at sampling instants. An introduction to the design of control systems leads to a process-related view and coverage of methods of translating analog designs to digital control. Concluding chapters explore implementation issues and advanced design methods.
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