Position control of an electro-hydrostatic asymmetric actuator operating in all quadrants

Abstract

Pump-controlled actuators generally use single-rod cylinders in order to provide high output forces and reduce the installation space. According to the working principle of such systems, there are four possible circuit configurations, corresponding to four operational quadrants. This paper presents the design and experimental validation of a robust, fixed-gain, linear position controller for a newly developed single-rod pump-controlled actuator, i.e., electro-hydrostatic actuator (EHA) that operates in all quadrants. The actuator operates under different loading, being subjected to an alternating resistive-assistive load force. The controller has been built upon the quantitative feedback theory (QFT), and is designed to satisfy tracking, stability and disturbance rejection specifications, considering a wide range of parametric uncertainties. The ability of the proposed controller to maintain the actuator position within acceptable response envelopes, has been examined with the aid of an instrumented John Deere JD-48 backhoe. The experimental results show that oscillations in position responses are not observed during quadrant switch up to a load mass of 367 kg.