Ultrasonic motor is a new-type

special motor

which can be applied widely in many fields such as aeronautic and astronautic field. Because ultrasonic motor is driven by friction，With the ultrasonic motor working for a long time its temperature rises continually

its resonance frequency drifts and speed will fluctuate. Especially in vacuum abstract air convection and heat conduction the ultrasonic motor’s temperature rises highly than in normal condition. This paper develops a system to test and control the speed of ultrasonic motor mainly made of SCM .Base the relation between the ultrasonic motor’s speed and its driving frequency

using Fuzzy PI control strategy control the speed of ultrasonic motor working in vacuum. Test proves that using the system the ultrasonic motor can work steadily in design speed in vacuum (the high vacuum degree up to 0.003pa)

and the speed deviation don’t exceed 1 rpm.