An analysis of a noncontact ultrasonic motor with an ultrasonically levitated rotor

The authors have proposed a noncontact ultrasonic motor whose rotor is levitated ultrasonically and revolved at a very high speed. This paper presents the theoretical calculations and the experimental discussions to improve the revolution characteristics and the stability of the rotor axial position. Being based on the theory of near-boundary acoustic streaming, a theoretical model for the calculation is developed. Following this, the effects of the velocity and the mode number of the stator vibration, the driving frequency and the width of the gap between the stator and the rotor are estimated numerically. Ten motors with different dimensions are made to verify the calculated results. The numerical and experimental results give us a lot of useful guidelines for designing this motor. (C) 1997 Elsevier Science B.V.