Position tracking control of electro-hydraulic single-rod actuator based on an extended disturbance observer

This paper presents a nonlinear cascade controller based on an extended disturbance observer to track desired position trajectory for electro-hydraulic single-rod actuators in the presence of both external disturbances and parameter uncertainties. The proposed extended disturbance observer accounts for external perturbations and parameter uncertainties separately. In addition, the outer position tracking loop uses sliding mode control to compensate for disturbance estimation error with desired cylinder load pressure as control output; the inner pressure control loop is designed using the backstepping technique. The stability of the overall closed-loop system is proved based on Lyapunov theory. The controller performance is verified through simulations and experiments. The results show that the proposed nonlinear cascade controller, together with the extended disturbance observer, provide excellent tracking performance in the presence of parameter uncertainties and external disturbances such as hysteresis and friction.