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.