SBIR-STTR Award

Active Signal Technologies and Moog propose to demonstrate a solid state pulse width modulated pilot stage for a servo valve enabled by single crystal PMN-PT. The basic mechanism and labor intensive fabrication processes used to build conventional servo valves remain largely unchanged since the device was launched in 1951, resulting in high cost and limited bandwidth. A digitally controlled valve has been long sought but has not materialized because of the limitations of available drivers -- low frequency capability of magnetic torque motors and solenoids, and stroke limitations of "high strain" solid state materials such as Terfenol and PMN. However, the advent of single crystal PMN-PT with over 2 times the strain of conventional solid state materials and low hysteresis can supply the 10X bandwidth improvement needed to realize a truly digital valve. The new servo valve will not only be smaller and low cost, but will be more readily integrated with digital control, especially for adaptive structural control using distributed actuation. In Phase I we will build a working pilot stage valve and demonstrate its switching speed capability, and in Phase II we will develop a fully integrated high speed servo valve using this technology.

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.

Keywords:
SPOOL, FLUID METERING, SERVO VALVE, HIGH FREQUENCY CONTROL, PILOT STAGE, FLUID AMPLIFIER, SINGLE CRYSTAL PIEZOELECTRICS, HYDRAULICS