Comparison of Robust Stability for Electrohydraulic Steering Control System Based on LQG and H-infinity Controller

Abstract

The paper compares the robust stability of two embedded controllers applied in electrohydraulic steering systems - linear-quadratic Gaussian (LQG) controller and H-infinity controller. Both controllers are synthesized on the base of state-space system model obtained with identification. To investigate robust stability of the closed-loop system 30% parametric uncertainty is introduced into B matrix of the model which describes the observed hysteresis of the electrohydraulic actuator. The closed-loop system is represented as M-$\Delta$ interconnection which allows calculation of its structured singular value ($\mu$) with both controllers. The H-infinity controller achieves smaller singular value than the LQG controller which asserts that loop stability in presence of bounded variations in the model characteristics is increased in the case of H-infinity controller. The performance of both controllers is experimentally verified on laboratory test bench.