Pulse-Width-Modulated Servo Valve Enabled by Single-Crystal Piezoelectric Stack

Active Signal, Moog, and Cornell University propose to develop and demonstrate a full-scale, benchtop-integrated, high-speed digital servovalve for use in adaptive structural control schemes that employ distributed actuation. Today’s servovalves are expensive and low bandwidth because the mechanism and its labor-intensive fabrication processes remain largely unchanged since the product was introduced in 1951. A digitally controlled valve has long been sought but is still unrealized because of shortcomings in candidate pilot stage actuators. Using the single crystal PMN-PT pulse width modulated pilot flapper developed in Phase I, the team demonstrated a 5X bandwidth improvement in the pilot-stage thereby paving the way to a truly digital valve. In Phase II Active Signal and Moog will refine the mechanical/hydraulic design, fabricate an improved pilot-stage and integrate it with an instrumented, as-machined industrial servovalve. The team will measure transfer functions within this integrated valve to enable Cornell University to develop control code to rapidly and precisely adjust spool position to meter flow and eliminate deadband. The performance of the new valve will be compared to an equivalent-size, high end aerospace servovalve. The new servo valve will not only be smaller and far lower in cost, but will integrate readily with digital control.