Study On Sliding Mode Control Theory And Application For Uncertain System

Control of uncertain systems is an important research topic in automatic control field. At present, robust control, adaptive control, sliding mode control and intelligent control are main classes of control methods for uncertain systems. Sliding mode control theory is known to be an efficient alternative way to tackle uncertain system because ideal sliding mode is whole robust for matched parameter uncertainties and external disturbances. The aim of this dissertation is to study sliding mode control design approaches of feasibility for uncertain system by combining robust control, adaptive control, T-S fuzzy model control theory and sliding mode control theory. The following are main results: Sliding mode control problem of a class of uncertain systems is discussed. The main character of design for a class sliding mode hyperplane is specified. Following this idea, it is shown that the design of robust sliding mode hyperplane is obtained easily from the corresponding conclusions of robust control for a class of linear systems with unmatched uncertainties. In addition, suppose the motions of practical sliding mode are only uniformly restricted to a certain region containing the original point. In this case, sliding mode dynamics deviated form ideal sliding mode motion is studied; and the estimate of the global closed-loop dynamics is given. A novel sliding mode strategy with virtual state feedback control is presented for a class of uncertain time-delay system. A delay-independent sufficient condition for design of sliding mode hyperplane is developed. Simple sliding mode controller is constructed, and the global robust stability of the closed-loop system is guaranteed. In addition, this strategy is extended to a class of neutral time-delay system with unmatched uncertainties. The obtained sufficient condition for design of sliding mode hyperplane is considerable simple owing to the role of virtual feedback control. Based on global sliding mode scheme, an adaptive sliding mode controller for a class of uncertain time-delay system is investigated. The main aim of adaptive sliding mode controller is to drive the system states to ideal sliding mode hyperplane. The design of sliding mode hyperplane is obtained through the delay-dependent robust stable conclusions of nominal time-delay system based on state transformation model with free-weighting matrices, which leads less conservative for the design of sliding mode hyperplane. Fuzzy sliding mode controller for a class of nonlinear time-delay system in presence of both parameter uncertainties and external disturbance is discussed. The T-S fuzzy model is employed to represent the uncertain nonlinear time-delay system. Sufficient conditions for design of robust sliding mode hyperplane are given by using virtual state feedback control. The global asymptotic stability of the closed-loop control system is guaranteed. A novel discrete reaching law with dynamic disturbance compensator is presented for a class of uncertain systems. Measure of parameter uncertainties and external disturbances is obtained online through the deviations between the practical reaching law and the desired reaching law. The robust stability of the closed-loop system is guaranteed. System dynamics in the vicinity of the sliding mode hyperplane is examined in detail. It is shown that the dynamic features and robustness of the closed-loop system are improved effectively and all advantages of the reaching law are retained. The applications of sliding mode controller are discussed. The sliding mode controller for an inverted pendulum system on a cart is investigated based on virtual state feedback strategy, the experiment results are given in detail. Based on active control techniques, a active sliding mode control approach is presented for synchronization of two uncertain chaotic system. A fuzzy sliding mode controller is presented to stabilize uncertain Chen's chaotic system based on T-S fuzzy model. The difficulty of constructing a robust sliding mode plane is alleviated by using virtual state feedback. Meanwhile, high gain to suppress the parameter uncertainties and external disturbances is avoided by tradeoff of T-S fuzzy control. In addition, discrete reaching law with dynamic disturbance compensator is applied to achieve accurate servo tracking to BLDC control system in the presence of load disturbance and plant parameter variations.