A Position Adaptive Control Associated with High Gain Observer for Electro-Hydraulic Servo System

For manipulating electro-hydraulic servo systems (EHSSs), an adaptive control scheme is proposed to realize the position tracking of electro-hydraulic actuator piston, with consideration of nonlinearity, immeasurable system state, and especially model parameter uncertainties. To cope with the problem of describing immeasurable system states, a high gain observer (HGO) is constructed. The adaptive control is composed of two parts, the parameter adaptive law and the control law. The part of parameter adaptive law is designed to alleviate the influences of parameter uncertainties and external disturbances via Lyapunov function formulation. The control law depends on the back-stepping control method combined with parameter adaptive law aiming to guarantee high-accuracy tracking performance. The closed-loop asymptotic stability of the proposed control method is proved according to Lyapunov stability theory. Finally, to emphasize the merits of the proposed method, a traditional PI controller is used to be compared. The simulation results show that the proposed adaptive control with HGO has precise and rapid response under model parameter changing conditions.