Sliding mode control of an electrohydraulic servo motor using a gain scheduling type observer and controller

Abstract

Abstract

The present paper is concerned with the enhancement of robustness of an electrohydraulic servo motor operated using a sliding mode control scheme. A sliding mode control scheme combined with an asymptotic observer is useful as a means to depress chattering, but the mismatch of the parameters between the actual system and its observer model makes the transient estimation errors of states great, and the robustness is lowered. In this investigation, paying attention to the fact that the most dominant parameter of an electrohydraulic servo system is the inertia, an on-line inertia estimation method utilizing pressure sensors is developed. A new, gain scheduling type of observer, which is constructed using two linear observers and an estimate of the inertia, is presented. It is demonstrated that the robustness of an electrohydraulic servo motor is improved by using the proposed observer and that the robustness is more enhanced by varying the controller parameters according to the value of the estimate of the inertia.