High gain observer based nonlinear position control for electro-hydraulic servo systems

We present a high gain observer-based nonlinear position control for electro-hydraulic servo systems. We design passivity based control for improve tracking performance. The passivity based control needs the full states information. Since the electro-hydraulic servo system has nonlinearities, we designed a modified high gain observer to estimate its states without the transformation for normal form. To reduce the effect of nonlinear terms, we use a high gain technique. We analyze the stability of the closed-loop system using the singular perturbation method. Simulations show that the proposed controller has better position tracking performance than a standard PI controller.