A discrete variable structure control scheme based on combined switching surfaces for position control systems

A scheme based on combined switching surfaces is introduced. Based on the characters of shifting switching surface (SSS) and conventional switching surface (CSS), modified exponent reaching law is adopted. The state of system is designed initially staying at the SSS, and then moves to stable point. As soon as the state moves into the converge range of the CSS, the parameters of the CSS are determined by the state, and the state turn to stay at the CSS and move to zero state. By using the scheme of combined switching surfaces, the state always stays on the switching surfaces, and so the robustness of systems are guaranteed. Moreover, this scheme is used in two-order position control system. The simulation results show that the scheme is effective.