Discrete-time Variable Structure Control And Its Simulation Study

Variable structure control(VSC) are well known for their robustness to system parameter variations and external disturbances. VSC have been widely used in many applications, such as robots, aircrafts, power generator and DC and AC motors and so on. In the recent years, with the development of microcomputer technology and the needs of industrial automation. We use computer to realize the control algorithm. But during the time of realizing the VSC, because of the limits of sampling, the ideal sliding mode does not exist. The state trajectory of system is chattering, which restrict it's actual applications. In the circumstances, the arrival condition and the existence condition have been changed. It is significant to study discrete-time VSC (DVSC) to reduce chattering of sliding mode.In this thesis, a detailed analysis of the current situation of study on variable structure and a discussion about the discrete-time systems VSC are stressed. The main contents in this thesis are as follows.1. The background related to the subject is summarized2. The related definitions of DVSC are proposed. After analyzing the arrival condition, the existence condition and stabilization of sliding mode in DVSC.3. Detailed analyzing the reason for the discrete reaching law to cause system chattering is given and three improved discrete reaching law is developed. At last, several simple examples are given to illustrate the proposed methods, simulation results are compared with those of some other design methods, which justifies the conclusion obtained.4. The design of VSC for uncertain discrete time systems is discussed. A grey estimating model is built for the uncertain part and thus values of parameters are obtained. Simulation results are presented to illustrate that the method in the thesis is rational.