Ultrasonic clutch using piezoelectric vibrators

This paper investigates the design, fabrication and test of an ultrasonic clutch with two piezoelectric vibrators, which is driven by the phenomenon of ultrasonic levitation. For the vibrators, one is used as a driving member connected to a shaft of a driving motor, and the other is used as a slave member connected to a shaft of a mechanical load. The operating principle of the clutch is expressed first. Then, the mechanism of the clutch is designed and constructed, and thus mounted between the driving motor and the mechanical load. Moreover, a full-bridge switching resonant inverter, including a DC chopper, a resonant tank and an equivalent circuit of the vibrator, is used to generate a sinusoidal voltage source at the input terminals of each vibrator. Furthermore, a set of speed measuring system is required to detect the rotational speeds of the slave shaft. As anticipated, the radiation surfaces of the vibrators can be coupled when both vibrators are not energized electrically. These radiation surfaces can also be separated when at least one of the vibrators is energized with high AC power.