Study On Sampled-Data Controller Design For Two Classes Of Control Systems

In practical control systems, many control systems consist of continuous-time processes (or plants) and discrete-time controllers (which can be implemented by digital computer, etc.), i.e. sampled-data control systems. In fact, uncertainties always appear in the controlled plants, such as parameter uncertainties, time-delay uncertainties, nonlinear perturbation, etc. so it is important to analysis robust stability of sampled-data control systems and design robust sampled-data controller. Furthermore, when the controlled plants are modeled by fuzzy systems, to design a sampled-data controller is converted to design a fuzzy sampled-data controller. Considering the modeling error between fuzzy model and practical plant, it is a challenging issue to design fuzzy sampled-data controller for uncertain fuzzy systems.The main results in the dissertation are as follows.(1) The significance of this paper is introduced, not only in theory but also in applications. And the related development is retrospected briefly.(2) The delay-dependent sampled-data control problems for linear time-delay systems for two different cases of time-varying delay are studied. Firstly, by using descriptor system model technique and input delay approach, some existent conditions of delay-dependent sampled-data controller for linear time-delay systems are presented in linear matrix inequality (LMI) form, and some parameterized design formulas of such controller are given. When every sampling-time interval is less than or equal to a positive number h>0 (i.e., sampling interval upper-bound) satisfying the above existent conditions, the designed sampled-data controller can stabilize such time-delay systems. Especially, when h approximates to zero, the above existent conditions can be reduced to the other existing delay-dependent stabilization conditions. Furthermore, the design methods of sampled-data controller for time-delay systems with uncertainty areproposed. Finally, two design examples are given to demonstrate the effectiveness and superiority of our proposed methods over the existing ones.(3) The fuzzy sampled-data control problem for T-S continuous-time fuzzy systems is discussed. A linear matrix inequalities (LMIs) condition for fuzzy sampled-data stabilization of T-S fuzzy systems is established via descriptor approach, Lyapunov-Krasovikii function, and LMI approach. The design method of fuzzy sampled-data controller is given simultaneously. Moreover, when a continuous-time fuzzy controller can stabilize the T-S fuzzy systems, the corresponding fuzzy sampled-data controller with the same gain matrices can stabilize such T-S fuzzy systems for any small enough sampling intervals. Two design examples are given to demonstrate the effectiveness of the suggested method.(4) Our obtained results of the thesis are concluded, and some research directions on sampled-data control in future are proposed.