Adaptive Robust Motion Control of Electra-Hydraulic Servo Systems Driven by Single-Rod Actuators

Abstract

This paper studies the high performance robust motion control of electro-hydraulic servo systems driven by single-rod actuators. In contrast to the double-rod hydraulic actuators studied previously, the two chambers of a single-rod hydraulic actuator have different areas. As a result, the dynamic equations describing the pressure changes in the two chambers cannot be combined into a single load pressure equation. This complicates the controller design since it not only increases the dimension of the system to be dealt with but also brings in the stability issue of the added internal dynamics. An adaptive robust controller based on discontinuous projection method is constructed. The resulting controller is able to take into account not only the effect of parametric uncertainties coming from the inertia load and various hydraulic parameters but also the effect of uncertain nonlinearities such as uncompensated friction forces and external disturbances. Non-differentiability of the inherent nonlinearities associated with hydraulic dynamics is carefully examined and addressing strategies are provided. The controller guarantees a prescribed transient performance and final tracking accuracy in the presence of both parametric uncertainties and uncertain nonlinearities while achieving asymptotic tracking in the presence of parametric uncertainties.