Hybrid Control Strategies For Discrete Variable Structure Control Systems Via Extension Control

Variable structure control (VSC) is well known for its robustness to system parameter variations and external disturbances developed in the late 1950's. VSC has been widely used in many applications, such as robots, 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 its 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 dissertation, on the basis of the variable rate reaching law, exponential rate and extension control, a new control strategy is formed. The contents in this dissertation are as follows:1. Review the developing of DVSC and extension control. And tell of the necessary of combine the two algorithms as a new algorithm named hybrid control strategies for discrete variable structure control systems via extension control.2. The related definitions of DVSC are proposed. The arrival condition, the existence condition and stabilization of sliding mode in DVSC are analyzed.3. Present the related basic concepts of extension control, the structure of canonical extension control, extension set of character status of basic extension controller, and general extension control algorithm.4. In chapter four, apply extension control into the DVSC and present a new hybrid control strategies for discrete variable structure control systems. The simulations are made between variable rate reaching law, exponential rate and extension control for DVSC. The results show that the new hybrid control strategies are effective in reducing the chattering and improving dynamic performances of system effectively.5. In the end, a conclusion is made and the future researches are prospected.