Experimental investigation of an electro-hydrostatic actuator based on the novel active compensation method

For electro-hydrostatic actuators (EHAs), how to estimate and compensate for the combined effects of the severe nonlinearity caused by inner leakage and friction, the parametric uncertainties of the hydraulic components due to the environment and the external disturbance remain the primary issues. In this paper, a novel four-loop cascade control based on the active disturbance compensation method was proposed to address the abovementioned problem. First, by dividing the model of an EHA, two low-order estimators were obtained rather than a high-order estimator, which are easier to be implemented. Further, pressure information of two chambers of the EHA was applied in the proposed controller to compensate for the mismatching disturbances directly. Finally, the experimental results proved that the proposed method improved the robustness and static state error by approximately 35% and 33%, respectively.