In this paper, the robust optimal model matching control design method is applied to a flexible b... more In this paper, the robust optimal model matching control design method is applied to a flexible beam Quanser experiment. The neglected nonlinearities of the real experiment in the controller design step lead to important differences between the simulation and experimental results, including vibrations of the real beam and/or stationary errors due to insensibility zone. In order to eliminate these tracking errors and reduce the vibrations of the beam we proposed an improved control law by using some blocks with variable structure. Because some of the model's parameters are imprecisely known, an identification procedure is needed. The paper presents a subspace identification method, which is a relatively new approach used for the state space model identification. Finally, the performance of the proposed controller is illustrated by some experimental results. The flexible beams dynamic is described by partial differential equations that are obtained based on Euler-Lagrange theory. ...
The stabilization by feedback control of systems with input delays may be considered in various f... more The stabilization by feedback control of systems with input delays may be considered in various frameworks. An approach to stabilize a such system, based on the Artstein transform, is the so-called finite spectrum assignment. In this case the control law that stabilize the system is a distributed delay control law. A difficulty in applying a control law of this form consists in the practical implementation of the integral term, which needs to be calculated on-line. Some recent papers outlined an instability mechanism when the distributed delay in the control law is approximated with a sum of point-wise delays, despite the asymptotic stability of the ideal closed-loop system. In this paper, we use a suitable discretization rule based on piecewise constant control signals. Then, we analyze and illustrate by some numerical examples the robustness/fragility of this control law.
In this paper there is presented a rather straightforward application of the absolute stability f... more In this paper there is presented a rather straightforward application of the absolute stability frequency domain inequalities to the practical problem of PIO (Pilot In-the-loop Oscillations) proneness of aircrafts. An extended to critical cases version of the Yakubovich criterion for the case of slope restricted nonlinearities is applied to the benchmark case of the X15 landing flare incident.
Control of Systems with Input Delay—An Elementary Approach
Lecture Notes in Computational Science and Engineering, 2004
Control of Systems with Input DelayAn Elementary Approach Vladimir Rasvan1 and Dan Popescu2 1 De... more Control of Systems with Input DelayAn Elementary Approach Vladimir Rasvan1 and Dan Popescu2 1 Department of Automatic Control, University of Craiova, AI Cuza Str. No. 13, RO 1100 Craiova, ROMANIA vrasvan@ automation. ucv. ro 2 dpopescu@ automation. ucv. ro ...
In the last years the problem of fragile controllers (high sensitivity of closed-loop stability a... more In the last years the problem of fragile controllers (high sensitivity of closed-loop stability and/or performance against small changes in controller coefficients) designed by using robust and optimal control methods has generated some controversial discussions. In this paper, we analyse the parametric stability margins for some optimal controllers by using different measures. So, we show that the normalized l^2 parametric stability margin is not suitable when the controller coefficients lie in very different ranges and, in this case, we propose a new measure to appreciate the parametric stability margin. Also, we propose some reformulations of optimization problem such that to increase the parametric stability margins around the coefficients of the designed optimal controller. An algorithm to determine an extended range of robust stability is presented. Also, an iterative algorithm that allows computing controllers with increased parametric stability margins is proposed. We illust...
This paper focuses on evaluation of the performance characteristics of workflows in constructions... more This paper focuses on evaluation of the performance characteristics of workflows in constructions modeled with stochastic Petri nets (SPN). This goal is achieved by focusing on a new model for Artificial Social Systems (ASS) behaviors. ASS exists in practically every multi-agent system, and play a major role in the performance and effectiveness of the agents. This is the reason why we introduce a more suggestive model for ASS. To model these systems, a class of Petri nets is adopted, and briefly introduced in the paper. This class allows representing the flow of physical resources and control information data of the ASS's components. In the analysis of SPN we use simulations in respect to timing parameters in a generalized semi-Markov process (GSMP). By using existing results on perturbation (e.g., delays in supply with raw materials, derangements of equipments, etc.) analysis and by extending them to new physical interpretations we address unbiased sensitivity estimators correlated with practical solutions in order to attenuate the perturbations. An important advantage of this approach is that one simulation is needed for evaluating the stochastic Petri nets and the perturbation analysis and to take advantage of the state of the art.
Applications of stability criteria to time delay systems
Proceedings of The 7'th Colloquium on the Qualitative Theory of Differential Equations (July 14--18, 2003, Szeged, Hungary) edited by: L. Hatvani and T. Krisztin, 2003
In this paper, the robust optimal model matching control design method is applied to a flexible b... more In this paper, the robust optimal model matching control design method is applied to a flexible beam Quanser experiment. The neglected nonlinearities of the real experiment in the controller design step lead to important differences between the simulation and experimental results, including vibrations of the real beam and/or stationary errors due to insensibility zone. In order to eliminate these tracking errors and reduce the vibrations of the beam we proposed an improved control law by using some blocks with variable structure. Because some of the model's parameters are imprecisely known, an identification procedure is needed. The paper presents a subspace identification method, which is a relatively new approach used for the state space model identification. Finally, the performance of the proposed controller is illustrated by some experimental results. The flexible beams dynamic is described by partial differential equations that are obtained based on Euler-Lagrange theory. ...
The stabilization by feedback control of systems with input delays may be considered in various f... more The stabilization by feedback control of systems with input delays may be considered in various frameworks. An approach to stabilize a such system, based on the Artstein transform, is the so-called finite spectrum assignment. In this case the control law that stabilize the system is a distributed delay control law. A difficulty in applying a control law of this form consists in the practical implementation of the integral term, which needs to be calculated on-line. Some recent papers outlined an instability mechanism when the distributed delay in the control law is approximated with a sum of point-wise delays, despite the asymptotic stability of the ideal closed-loop system. In this paper, we use a suitable discretization rule based on piecewise constant control signals. Then, we analyze and illustrate by some numerical examples the robustness/fragility of this control law.
In this paper there is presented a rather straightforward application of the absolute stability f... more In this paper there is presented a rather straightforward application of the absolute stability frequency domain inequalities to the practical problem of PIO (Pilot In-the-loop Oscillations) proneness of aircrafts. An extended to critical cases version of the Yakubovich criterion for the case of slope restricted nonlinearities is applied to the benchmark case of the X15 landing flare incident.
Control of Systems with Input Delay—An Elementary Approach
Lecture Notes in Computational Science and Engineering, 2004
Control of Systems with Input DelayAn Elementary Approach Vladimir Rasvan1 and Dan Popescu2 1 De... more Control of Systems with Input DelayAn Elementary Approach Vladimir Rasvan1 and Dan Popescu2 1 Department of Automatic Control, University of Craiova, AI Cuza Str. No. 13, RO 1100 Craiova, ROMANIA vrasvan@ automation. ucv. ro 2 dpopescu@ automation. ucv. ro ...
In the last years the problem of fragile controllers (high sensitivity of closed-loop stability a... more In the last years the problem of fragile controllers (high sensitivity of closed-loop stability and/or performance against small changes in controller coefficients) designed by using robust and optimal control methods has generated some controversial discussions. In this paper, we analyse the parametric stability margins for some optimal controllers by using different measures. So, we show that the normalized l^2 parametric stability margin is not suitable when the controller coefficients lie in very different ranges and, in this case, we propose a new measure to appreciate the parametric stability margin. Also, we propose some reformulations of optimization problem such that to increase the parametric stability margins around the coefficients of the designed optimal controller. An algorithm to determine an extended range of robust stability is presented. Also, an iterative algorithm that allows computing controllers with increased parametric stability margins is proposed. We illust...
This paper focuses on evaluation of the performance characteristics of workflows in constructions... more This paper focuses on evaluation of the performance characteristics of workflows in constructions modeled with stochastic Petri nets (SPN). This goal is achieved by focusing on a new model for Artificial Social Systems (ASS) behaviors. ASS exists in practically every multi-agent system, and play a major role in the performance and effectiveness of the agents. This is the reason why we introduce a more suggestive model for ASS. To model these systems, a class of Petri nets is adopted, and briefly introduced in the paper. This class allows representing the flow of physical resources and control information data of the ASS's components. In the analysis of SPN we use simulations in respect to timing parameters in a generalized semi-Markov process (GSMP). By using existing results on perturbation (e.g., delays in supply with raw materials, derangements of equipments, etc.) analysis and by extending them to new physical interpretations we address unbiased sensitivity estimators correlated with practical solutions in order to attenuate the perturbations. An important advantage of this approach is that one simulation is needed for evaluating the stochastic Petri nets and the perturbation analysis and to take advantage of the state of the art.
Applications of stability criteria to time delay systems
Proceedings of The 7'th Colloquium on the Qualitative Theory of Differential Equations (July 14--18, 2003, Szeged, Hungary) edited by: L. Hatvani and T. Krisztin, 2003
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