Research On Variable Structure Control For Uncertain System With Dead-Time And Chattering Phenomenon

Variable structure control (VSC) that is brought in 50's is attention-getting because of its ideal robustness. The sliding mode movement of variable structure system holds the invariance for the change of system parameters, outside disturbance, uncertain mode and model uncertainty of the system. It has been broadly used in the field of control with the development of computer technology and produce of high-speed switch circuit. Its flaw is that after the system state getting to the sliding plane, it will produce high frequency chattering around the sliding plane and the control variable of the system will also produce high frequency chattering. The process of time-delay and uncertainty system is one class complicated industrial process that extensively lies in petroleum, chemical industry, brewing field etc. The problems of control system in time-delay and uncertainty are always puzzling automation school. Many experts have researched on variable structure control for uncertain system with dead time while the application of VSC is more and more wide. At the same time, how to eliminate the chattering phenomenon of VSC is becoming the interesting question to the experts.The dissertation mainly contains three parts. Firstly, the dissertation refers to comparatively full literatures in the field of VSC, and the development history and characteristics of VSC are summarized, and the elementary concepts, elementary definitions, elementary properties, elementary principles and design methods are particularly introduced. Then the causes of the chattering phenomenon are systematically analyzed, and the study of the chattering phenomenon is elaborated. Secondly, aiming at the uncertain process with dead-time, the paper proposes a kind of simple variable structure controller. The design of controller is based on the object reference parameter adaptive dead time compensator. A group of models are used to simulate the uncertain process with dead time and the compensator has good track capability. As a result, the dead time is excluded from the closed loop control system and the design of controller is simplified. Thirdly, for the deficiencies of traditional methods, a kind of improved exponent reaching law solution is proposed. Then the results of simulation prove that the methods are feasible and effective.At the last, the works of the dissertation are summarized and the problems to be solved are introduced.