Adaptive Tracking Control For T-S Fuzzy Systems With Actuator Dead-Zone

In practical control systems,the dead-zone phenomena often take place in the actuators due to the limit and actual significance of physics performances of composed components,even the parameters of the actuators vary along with the work conditions and environment changing,which make the parameters of existent dead-zone are time-varying.The dead-zone results in stability error of controlled systems,and badly restricts performances of systems.So it is important to study the systems with actuator dead-zone,not only in theory but also in applications.Furthermore,in the research domain of nonlinear systems,when controlled plants are modeled by fuzzy systems, the design problem of an adaptive controller is converted to that of an adaptive fuzzy controller.Since the dead-zone phenomena often occur in the actuators,it is a hotspot issue to study the analysis and synthesis of nonlinear systems with actuator dead-zone in the control domain.The main results in the thesis are as follows:(1) The significance of this thesis is introduced,not only in theory but also in applications.And the corresponding development both abroad and at home is recalled briefly.(2) For Takagi and Sugeno(T-S) fuzzy systems representing the nonlinear systems,the problem of adaptive tracking control for systems with actuator non-symmetric dead-zone is studied in this thesis.Non-symmetric dead-zone is assumed that the output signal is piecewise linear about the input signal,and the bandwidth of the dead-zone is unknown positive constant but bounded.First,T-S fuzzy system is employed to represent the nonlinear system.Then,the output of the non-symmetric dead-zone can be represented as a linear input and a bounded disturbance.For a given n-differentiable bounded reference trajectory y_r(t) and a given precision of tracking errorε₀,the existent conditions and design methods of adaptive fuzzy controller are given for the systems with actuator non-symmetric dead-zone by the Lyapunov stability theory and the LMI approach.The designed controller ensures that tracking errors of the system meets‖e‖＜ε₀, and all the signals in the closed loop are bounded.In order to improve the precision of tracking error,according to adjustable parameters we propose designed steps of adaptive tracking controller.The efficiency of our design method is finally illustrated by simulation.(3) An adaptive tracking control method which combines fuzzy-model-based control is presented for a class of nonlinear systems with actuator time-varying dead-zone.The output signal of time-varying dead-zone is piecewise nonlinear about the input signal(if the input signal exceeds given constants),and the slopes of the dead-zone are unknown positive function but bounded and the bandwidth of the dead-zone is unknown positive constant but bounded.The T-S fuzzy model is adopted for representing the nonlinear system with actuator time-varying dead-zone,and fuzzy-model-based adaptive control laws are designed by means of the Lyapunov stability theory and the LMI approach.For a given n-differentiable bounded reference trajectory y_r(t) and a given precision of tracking errorε₀,the designed controller ensures that tracking errors of the system meets‖e‖＜ε₀,and all the signals in the closed loop are bounded by tuning the designed parameters of such controllers.In order to improve the precision of tracking error,according to adjustable parameters we propose designed steps of adaptive tracking controller.The efficiency of our design method is finally illustrated by simulation on a mass-spring-damper system.(4) The main results of the thesis are concluded,and some research issues in future are proposed.