Numerical study of the stator motion in a piezoelectric ultrasonic motor

This paper presents mathematical modeling and numerical simulation results that are part of a study concerning the dynamics of the stator of piezoelectric (PZ) traveling wave (TW) rotating ultrasonic motor. The stator is a PZ composite ring, and the rotor is a metallic ring. The rotational torque is produced by exciting the stator into a flexural traveling wave, transmitted to the rotor through the stator-rotor friction. A modal analysis provides for the structural eigenfrequencies of the stator. When the AC powering stage providing for two voltages of same amplitude and shifted in quadrature is adapted to a frequency close to the flexural resonance of the stator, the TW reaches higher amplitudes that result in higher rotational velocities because the rotor speed is proportional to the stator TW amplitude.