Abstract: A variable gain control apparatus for a servo assist system includes a position sensor, a valve, a controller and an actuator. The valve has an actuated member and a variable flow orifice to communicate hydraulic fluid between the high pressure supply line and a reservoir of hydraulic fluid. The position of the actuated member determines the cross sectional area of the variable flow orifice. The position sensor determines the present position of the actuated member. The controller determines a position error between the present position of the actuated member and a varying predetermined position of the actuated member. The actuator in response to the position error actuates the actuated member to eliminate the position error so that assist pressure to the servo assist system is varied as a function of the varying predetermined position.

Abstract: An active hydraulic pressure control system includes a sensor, a valve, a controller and an actuator. In accordance with a broad aspect of the present invention, the controller determines a pressure differential between the pressure sensed by the sensor in a high pressure supply line of a hydraulic system and a predetermined pressure. In response to such pressure differential, the actuator drives the valve which has a variable flow orifice to communicate hydraulic fluid between the high pressure supply line and a reservoir of hydraulic fluid to eliminate the pressure differential.