Abstract: The asymmetric cylinder electro-hydraulic servo system is widely applied to the hydraulically driven 6-DOF motion simulator used as actuator at present, and its controller design is also noticeable. Firstly, a general nonlinear model of the asymmetric cylinder actuator controlled by servo-valve is derived. Then a cascade load pressure control strategy, which gives the hydraulic actuator the character of a force generator, is presented. So this establishes a basis for realizing the hierarchical control of the motion simulator. Taking account of the model uncertainties and external disturbances, the sliding mode control scheme is used to the design of the outer-loop stabilized controller in the actuator level which realizes the stabilization of the hydraulic actuator and the disturbance rejection. Finally, a state feedback controller is designed to compare with the sliding mode-cascade load pressure controller. Simulation results indicate the control strategy presented in this paper is effective and reasonable.

Key words: 6-DOF motion simulator, Asymmetric cylinder electro-hydraulic servo, Cascade load pressure control strategy, Sliding mode control