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August 2007, Sept. 2007, Oct. 2007, Nov. 2007, Dec. 2007, 2008


Issue 8, Volume 2, August 2007
Print ISSN: 1991-8763
E-ISSN: 2224-2856







Title of the Paper:  Sampled tracking for linear delayed plants using piecewise functioning controller


Authors: Wang Haoping, Vasseur Christian, Chamroo Afzal And Koncar Vladan

Abstract: This article presents a control method to realize tracking of linear plants that deliver a delayed and sampled state. To do so, we make use of a class of piecewise functioning controller (PFC): bi-sampled controller. The use of this type of controller allows sampled tracking with a delay twice as much as that on the state’s output. Thus, we propose an optimal mathematical approach of the dynamics of our controller. We then give an adaptation of this mathematical approach, using only the delayed and sampled state. Computer simulation results are given so as to enhance the theoretical aspect of our method.

Keywords: sampled tracking, bi-sampled controller, delayed sampled state

Title of the Paper: Decentralized Adaptive Fuzzy Control for a class of Nonlinear Systems


Authors: A.Errahmani, H.Ouakka, M.Benyakhlef and I.Boumhidi

Abstract: In this paper, stable direct and indirect decentralized adaptive fuzzy controls are proposed for a class of large-scale nonlinear systems with the strong interconnected. The feedback and adaptive mechanisms for each subsystem depend only upon local measurements to provide asymptotic tracking of a reference trajectory. In both approaches, the proposed controllers are used to approximate the unknown subsystems. In addition, each subsystem is able to adaptively compensate for interconnections without known bounds. Simulation results are given to illustrate the tracking performance of the proposed methods.

Keywords: Decentralized Control, Fuzzy Controller, Interconnected Nonlinear System.

Title of the Paper: Adaptive Inverse Control of Excitation System with Actuator Uncertainty


Authors: Xiaofang Yuan, Yaonan Wang, Lianghong Wu

Abstract: This paper addresses an inverse controller design for excitation system with changing parameters and nonsmooth nonlinearities in the actuator. The existence of such nonlinearities and uncertainty imposes a great challenge for the controller development. To address such a challenge, support vector machines (SVM) will be adopted to model the process and the controller is constructed using SVM. The SVM, used to approximate nonlinearities in the plant as well as the actuator, are adjusted by an adaptive law via back propagation (BP) algorithms. To guarantee convergence and for faster learning, adaptive learning rates and convergence theorems are developed. Simulations show that the proposed inverse controller has better performance in system damping and transient improvement.

Keywords: nonlnear control, inverse system, support vector machines, adaptive control, model identification, actuator uncertainty

Title of the Paper: On robustness of suboptimal min-max model predictive control


Authors: De-Feng He, Hai-Bo Ji, Tao Zheng

Abstract: With the hard computation of an exact solution to non-convex optimization problem in a limited time, we propose a suboptimal min-max model predictive control (MPC) scheme for nonlinear discrete-time systems subjected to constraints and disturbances. The idea of input-to-state stability (ISS) is introduced and a Lyapunov-like sufficient condition for ISS is presented. Based on this, we show that the suboptimal predictive controller obtained here holds back the disturbance robustly in the present of constraints on states and inputs.

Keywords: Nonlinear predictive control; Suboptimal control; Input-to-state stability; Constraints

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