Ultrasonic piezoelectric motors are distinguished by high torque at low speeds, short start-stop times and their inhibiting action in the off state. They consist of a metal resonator, which is stimulated by piezoelectric ceramics to produce oscillations with frequencies in the ultrasonic region, and a rotor that is driven by the resonator via a friction contact. The motor concept presented here is based on the transformation of the longitudinal oscillations of a rod-shaped resonator into continuous motion by arranging the resonator diagonally to a drum. The efficiency of the motor was enhanced by increasing the amplitude of motion at the point of motion transfer by tapering the resonator. To optimize the resonator design, the validity of the predictions derived from the one-dimensional analytical theory for longitudinal ultrasonic resonators was tested with respect to this application by means of finite-element calculations. The one-dimensional (1-D) calculation turned out to be hardly applicable at all to real resonators. The finite-element calculations showed that maximum final amplitude is attained when the resonator tapers as steeply as possible, no preference being shown for any special mathematical form of cross-sectional reduction. Efficiencies of 35 percent and torques of 25 Ncm were attained at 150 r/min.
|Number of pages||7|
|Journal||IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control|
|Publication status||Published - Nov 1989|
ASJC Scopus subject areas
- Acoustics and Ultrasonics
- Electrical and Electronic Engineering