Robust precision control for a class of electro-hydraulic actuator system based on disturbance observer

This paper presents a new robust control scheme for a class of electro-hydraulic actuator using dynamic sliding mode control associated with nonlinear disturbance observer. Switching-gain of the sliding mode is designed to be adaptable on the estimated disturbance. A switching-gain adaptation mechanism is proposed to obtain as small as possible switching-gain to minimize chattering effect. The scheme is developed to guarantee the tracking precision of the system with robust and smooth control actions in the existence of uncertainties and the changes of external disturbance. Capability of the proposed scheme is enhanced by varying boundary layers algorithm to assist the scheme to return to its ability in a larger change of external disturbance. Capability and effectiveness of the proposed scheme are validated through experiment, where the results indicate that the proposed scheme ensures the tracking precision of the system with robust and smooth control actions in a large change of external load disturbance. Moreover, smooth control actions that are produced by the proposed control scheme offer a significant efficiency of energy in the control of electro-hydraulic actuator systems.