Hydraulic servos incorporating a high-speed hydraulic-amplifier actuated valve

Electrohydraulic systems have certain advantages over pure electromechanical systems, which make them particularly suitable as an adjunct to electronic control for high-power level actuation. The main factor which has limited the application of hydraulic actuators until recently has been the awkardness of the control systems required. However, developments in the technique of controlling hydraulic flow electrically now permit the flexibility of electronic control to be applied to the linear operation of hydraulic valves at high speeds.