MODELING OF A PIEZOELECTRIC ROTARY ULTRASONIC MOTOR

A piezoelectric rotary ultrasonic motor is modeled for the purpose of predicting, a priori, motor performance as a function of design parame ters. The Rayleigh-Ritz assumed mode energy method is used to model th e distributed piezoceramics and the traveling wave dynamics of the sta tor. Natural frequencies and modeshapes are obtained for a generally c onfigured motor. Nonlinear normal and tangential interface forces betw een the rotor and stator are incorporated into the forcing function al ong with the linear piezoelectric forcing. Given the applied torque, a pplied axial Loading, and piezo drive voltages as inputs to the model, general motor performance measures are obtained-namely speed, input p ower, output power, and efficiency. The approach presented here provid es a general framework for modeling these motors as well as a design t ool for optimizing prototypes with the added flexibility of allowing f or a wide variety of geometries and materials.