A disc-type high speed rotary ultrasonic motor with internal contact teeth

Abstract

This paper presents a disc-type ultrasonic piezoelectric motor, which is designed for micro flying vehicles. It provides a high output rotation speed under low operating voltage, compared with common piezoelectric devices, by employing a “contact teeth” wave transmission structure. The ultrasonic motor (USM) consists of a trimorph disc stator, with triple internal contact teeth, a shaft and two hemispheric hard-wearing rotors. The operating principle of the USM is based on the superposition of the in-plane B03 vibration mode of the trimorph disc, and the first longitudinal vibration of the contact teeth. An optimization method of the stator structure parameters was proposed and validated by numerical modeling. The diameter and thickness of the stator are 20 mm and 1 mm, respectively. A prototype with the weight of 2 g was made for this experimental test. The optimal frequency of the excitation signal and the preload force are 98.5 kHz and 0.5 N, respectively. The minimum operating voltage was tested under 7.5 V and reached the speed of 225 rpm, and the maximum unloaded rotational speed of the USM reached 5172 rpm when 30 V driving voltage was applied. The maximum lifting force generated by this USM was measured as 46.1 mN, which is 2.35 times bigger than its weight.