Ring-type traveling wave ultrasonic motor using a radial bending mode [Correspondence]

A traveling wave ultrasonic motor utilizing a radial bending mode of a thick ring is proposed. Twenty PZT stacks and 20 block springs are nested alternately into 40 slots cut in the ring's outer surface to produce a traveling wave. The prototype achieves maximum speed and torque of 146 r/min and 1.0 N·m, respectively.