Position Control of an Electrohydrostatic Actuator With Tolerance to Internal Leakage

This brief presents design and experimental evaluation of a fixed-gain position controller for the class of electrohydrostatic actuator that is tolerant to actuator internal leakage fault and robust to various environmental stiffnesses and system parametric uncertainties. Built upon quantitative feedback theory, the proposed controller is designed according to stability and tracking specifications, considering actuator internal leakage as one of the uncertain phenomena. The controller is also augmented with a friction compensator to alleviate the parasitic effect of dry friction in the hydraulic cylinder and further improve the tracking performance. The ability of the augmented controller in maintaining the actuator position within acceptable response envelopes is demonstrated in both simulations and experiments. More specifically, the experimental results show that the steady-state error of various step input responses remains within 0.1 mm despite an internal leakage flow rate as high as 8.5 L/min.