Direct optical actuation for hydraulic systems

A description and results of an experiment that demonstrate an electrically passive hydraulic actuator under closed-loop control are presented. The control system demonstration hardware consisted of a control computer, an optohydraulic interface, fluidic amplifiers, and a position sensor. The control computer compared the actuator position as obtained from the hydraulic ram position sensor with the position command signal. The difference produced an error signal for driving the ram to the desired position. The error signal was converted to an optical signal and transmitted to the actuator servovalve via a multimode fiber-optic cable. The optohydraulic interface, located at the servovalve, converted the signal to a fluidic pressure signal. The fluidic pressure signal was amplified to provide sufficient power for driving the hydraulic servovalve. The hydraulic section of the servovalve operated the hydraulic ram with conventional hardware