Abstract: It is difficult for exponential reaching law variable structure consideration to both control performance and the chattering in electro-hydraulic position servo system, a new type of variable rate exponent reaching law of sliding mode controller is designed. The state space model on the deviation variable is established for electro-hydraulic position servo system, derive the structure of the exponential reaching law sliding mode controller, to further determine the switching function and its derivatives containing the deviation variable, by defining lyapunov function of the system, prove the stability of system under reaching law control. By real-time analysis the distance of moving point with sliding surface and reaching rate, the arrival speed is dynamically adjusted by fuzzy parameter optimization, the purpose for speeding up response and overcoming the perturbation and external disturbance out of the sliding surface and weakening control to eliminate chattering near the sliding surface. The square wave tracking dynamic response, steady-state error and control chattering indicators on the strategy are studied between variable rate reaching law and traditional exponential reaching law by experiment, the results show that the variable rate reaching law strategy not only guarantees the arrival movement speed, but also effectively reduces the steady-state chattering, has good steady-state performance.

Key words: Chattering, Electro-hydraulic position system, Sliding mode, Variable rate reaching law