Study On The New Algorithm Of Sliding Mode Control For Uncertain System

Domestic and overseas scholars attach great importance to the sliding mode variable structure control which has compelte robustness to the perturbation of the system parameters, the external disturbance and the uncertainty of the system. When the sliding mode variable structure control system of the state trajectory's speed is limited and the moving point arrives the switching surface, the moving point passes through the switching surface because of the inertia which forms the chattering. Chattering is one of the main hazards in the sliding mode variable structure control. Based on the exponent reaching law solution of the sliding mode variable structure control, a new reaching sliding mode variable structure control algorithm was researched which reduces the chattering of the sliding mode variable structure control uncertainty system effectively in the premise of ensuring robustness.This paper includes the following aspects:Based on the present literatures, this paper summarized the origin, development, the domestic and international research present condition and application of the sliding mode variable structure control; described the definition, features and the design method of the sliding mode variable structure control; analyzed the production principle of sliding mode variable structure control chattering; compared the main methods which can alleviate chattering in the world at present.Reaching law is one of the main methods which can alleviate the chattering of the sliding mode variable structure control, it includes constant reaching law, power reaching law, general reaching law and exponent reaching law solution which is often used in the sliding mode variable structure control. Based on the of the four reaching laws, this paper build the model and give a simulation of the exponent reaching law solution of the sliding mode variable structure control. According to the simulation results, we know that the effect of weaken chattering is obvious when the uncertainty of the system is smaller, but the effect would become unsatisfactory when the uncertainty of the system increases.When researching the sliding mode variable structure control of the uncertain systerm, based on the original exponent reaching law solution to research a new algorithm which can alleviate the chattering effectively of the more uncertain sliding mode variable structure control system has an pratical significance. According to analysis the application of the Lyapunov method in the uncertain sliding sode control, this paper use the liapunov function to evaluate the distance between the state trajectory and hyperplane and judge whether the state trajectory shrinks down to the origin point at last, this method can solve the chattering problem in more uncertain systerm. According to the limitations of the exponent reaching law solution, this paper rebuilds the mathematic modeling, uses the Lyapunov method to analyse and give a new reaching law control algorithm. The simulation result shows: the state trajectory can rapidly reach switching surface. When the motion segment tends to the switching surface, the reaching speed will slow down rapidly and the transiting time will cut down obviously.Compared with the traditional exponent reaching law solution, the chattering of the uncertain system decreases furtherly.