Design of a low-bandwidth position controller based on system identification for an electro-hydrostatic actuator

Abstract

In order to design a controller, mathematical model is usually derived first, either from physical laws or by employing a system identification technique. Physical laws may not fully define the system because of the existing uncertainties and/or difficulty to accurately model certain phenomenon. Therefore, the resulting controller may be too conservative. In this article, we design a low-bandwidth controller for an electro-hydrostatic actuator positioning system based on a system identification technique. The designed controller is also linear, fixed-gain and robust to system uncertainties. A set of offline parametric linear identifications are performed under different conditions, including various environmental stiffnesses, levels of actuator internal leakage, viscous dampings and load masses. The obtained family of identified models is then used to design a quantitative feedback theory controller that satisfies given tracking and stability specifications. In addition, the performance of the controller is examined against another quantitative feedback theory controller that is designed for the same system using physical laws. The performances of two controllers are examined on a test rig. Experimental results show that both quantitative feedback theory controllers are capable of maintaining actuator position within acceptable response envelope. However, the controller designed based on physical laws has higher bandwidth and therefore is more conservative.