Force Transfer Model and Characteristics of Traveling-Wave Type Ultrasonic Motors

This work intends to Introduce a new type of motor - traveling-wave type ultrasonic motor (TWUSM). The structure and the operation principle of the TWUSM were introduced in this paper at first. Then the force transfer model of the contact surface between the stator and the rotor was deduced based on the elastic contact theory and the Hooke´s law. The relationships between the preload, the contact angle and the physical parameters of the frictional material were given. According to the direct piezoelectric effect, the input current of the TWUSM was determined, and the output efficiency of the TWUSM was derived with the ratio of the output power of the contact surface and the input electric power of the TWUSM. Finally, all factors that affect the mechanical characteristics were analyzed, and the accuracy and the suitability of the analytical model were verified by comparison with the experimental results.