Performance of ultrasonic motor under vacuum and high temperature condition

The performance of ultrasonic motor under abnormal conditions are researched, with five kinds of engineering plastics chosen as the rotor friction materials of traveling wave ultrasonic motor (TWUSM). By means of contrast test methods, effects of pre-load,degree of vacuum and surrounding temperature on friction driving properties of TWUSM are studied by using vacuum equipment and simulative TWUSM tester suitable. The results show that stalling torque increases and no load speed decreases with the increase of the pre-load and degree of vacuum. The no load speed decreases with the increase of surrounding temperature. Effects of degree of vacuum on contact states are analyzed by acoustics theory. The conclusion is that action of acoustic levitation makes dynamic contact force between stator and rotor reduce. The major reason the stalling torque in vacuum is higher than that in normal is that the effects of acoustic levitation decrease and the dynamic contact force increases.