Frictional Noise and Noise Restraint of the Piezoelectric–Ultrasonic Motor

Some factors that notably affect the noise of the piezoelectric ultrasonic motor operating in circular bending vibration mode were examined experimentally in this paper. The experimental results and analyses showed that the operational noise was related not only to frictional materials but also many other factors such as the pre-pressing force on the rotor, the contact area and interface condition between the rotor and the stator, and the operational frequency. Moreover, it was firstly reported that both the intensity and the main frequency of the operational noise of the motor greatly varied with the pre-pressing force between the rotor and the stator.