Design and experimental study of electromagnet-type variable pre-pressure ultrasonic motor

The unique friction drive mode of the traveling-wave rotary ultrasonic motor (TRUM) endows it with the advantages of low speed and large torque, fast response, and self-locking for power failure. Appropriate pre-pressure is conducive to the smooth operation of TRUM and ensures its good output performance. Meanwhile, it can effectively alleviate the wear and tear of the contact surface and reduce the noise. However, the adjustment and setting of pre-pressure can be realized only in the manufacturing and assembly of TRUM rather than the operation process of TRUM. Hence, this paper designs an electromagnet-type variable pre-pressure ultrasonic motor by changing the applying mode of pre-pressure, which can adjust the pre-pressure by controlling the driving voltage of the coil. Furthermore, force and motion analysis of the core components is performed, and the basic parameters of an electromagnetic mechanism are calculated according to the design requirements. The feasibility of the motor is verified through experiments, and its voltage and frequency characteristics are analyzed. The proposed scheme has the advantages of direct transmission and fast response.