Contact model of a novel longitudinal and torsional ultrasonic motor

Abstract

A novel bonded type longitudinal-torsional piezoelectric motor was presented, including the stator, the rotor, the preloading system, etc. The stator was particularly slotted to form a structure with multi vibrators. The vibrator was constituted by a metal substrate and piezoelectric ceramics, pasted on the outer surface of the metal substrate to simplify the motor structure. Through the reasonable adjustment of design parameters, the resonant frequencies of the first longitudinal vibration mode and the second torsional vibration mode of the stator were adjusted to be as close as possible. Meanwhile, all the vibrators were regulated to the resonance state, which is beneficial to improve the efficiency of the motor. To evaluate the overall performances of the designed motor, a finite element contact model was established to research the contact characteristics of the stator and the rotor. By analysing the static and transient contact process, the pressure distribution on contact areas, contact state, sliding distance, and etc. were all obtained under load free condition. Besides, the speed curve and the output performance of the motor were both acquired. The results of contact analysis show that the longitudinal-torsional motor is working in a multi-surface contact mode actually. The analysis results also show that the contact pressure does not locally concentrate and sliding happens at the contact areas. Finally, according to the design parameters, a prototype motor was fabricated and then the theoretical analysis was verified by experiments.