Study on the exciting mode of ultrasonic motor using bending vibration transducer

Ultrasonic motors (USM) are new type actuators that exhibit merits such as simple structure, high torque at low speed, compact size, quick response, quiet operation, self-locking when power off, no electromagnetic radiation and higher position accuracy. In the previous study, the authors proposed a new type USM using bending vibration mode. In that new design, elliptical trajectory vibrations are formed on the two driving feet by composing two orthogonal bending vibration modes of a piezoelectric-metal beam, that avoid the mode degeneration problem in the design process. In this paper, our research focuses on the exciting mode of bending vibration ceramics of the proposed motor. Firstly, the vibration characteristics of the proposed motor under different exciting modes by changing the imposed position of the electrode are obtained by transient analysis. Then, the exciting mode is adjusted by changing the imposed area of the electrode, and the vibration strengths of the driving feet are analyzed. Analysis results show that the PZT ceramic away from the neutral plane of the bending mode shape offers more contributions to the bending vibration of the motor under the same exciting voltage, while the PZT ceramic that near to the neutral plane give very few contribution. The study results of this paper can guide the design of general bending vibration transducer.