A Differential Pulse-Length Modulated Pneumatic Servo Utilizing Floating-Flapper-Disk Switching Valves

A novel approach to gas servo design is presented which provides closed-center operation while eliminating close clearance sliding seals and elastic members. Pulse-length modulated pressure waves having zero quiescent pulse width are used to actuate a new type of switching valve termed a “floating flapper disk.” Signal generation and modulation as well as power-level flow control are shown to be possible using this novel valve. System performance is discussed and compared with that of an equivalent linear servo. A prototype system fabricated to demonstrate feasibility is described. The valving concepts described are adaptable to digital, bang-bang, and optimally switched fluid control systems.