Abstract: A system for positioning a device such as a valve with a mechanical input using a fluid operated actuator, a mechanical position feedback member coupled to a feedback element of the fluid operated actuator and an activation fluid valve. The fluid operated actuator has an output coupled to the mechanical input of the valve, a feedback element for mechanically indicating a position of the valve, and inputs for actuating fluid, such that fluid at the inputs causes the fluid operated actuator to move in opposing directions. The activation fluid valve has outputs coupled to the inputs of the fluid operated actuator, a first opposing force input coupled to the mechanical position feedback member and a second opposing force input coupled to a control input force. The position of the activation fluid valve is controlled by a balance between the force from the mechanical feedback member and the control input force.

Abstract: A servo control system comprising a hydraulic actuator, a position sensor and a hydraulic control valve. The hydraulic actuator is coupled to a gas controlled valve. The position sensor measures the position of the hydraulic actuator and sends the position of the actuator as an input to an engine control unit (ECU). The hydraulic control valve is coupled to a proportional solenoid coupled to the ECU. When the ECU senses the position of the hydraulic actuator and in response to a control input, the ECU commands the position of the hydraulic control valve by controlling the force of the proportional solenoid and the hydraulic fluid sent to the hydraulic actuator, actuating the hydraulic actuator to move to a desired position and actuate the gas controlled valve.