Control performance of hydraulic servo valves utilising electrorheological fluids

Abstract

This paper presents pressure control of a hydraulic servo valve activated by an electrorheological (ER) fluid. A cylindrical type of ER valve is devised and its field-dependent pressure drop is investigated through the step response. Then, in order to evaluate the pressure controllability of the ER valve, a bridge circuit is constructed and its governing equation is derived. A sliding mode controller is then designed to accurately track various pressure trajectories such as sinusoidal and trapezoidal trajectories and experimentally realised. In addition, a hydraulic booster is developed in order to amplify the field-dependent pressure drop obtained from the ER valve. After observing pressure amplification at various electric fields, pressure controllability of the ER servo valve associated with the hydraulic booster is demonstrated in time domain.