Rotary ultrasonic motor using longitudinal and bending modes and its analysis

A rotary ultrasonic motor using longitudinal and bending vibration modes is proposed in this study. The proposed motor contains two exponential shape horns located on two ends, and the end tips of the horns are used as the driving feet. Two groups of PZT elements (Longitudinal PZT and Bending PZT) are clamped in the middle of the motor by a double head flange bolt to excite the longitudinal vibration mode and bending vibration mode of the motor, respectively. By the composing of the longitudinal and bending vibration modes, elliptical trajectory vibrations can be generated on the end tips of the horns, which have the same rotation directions and can driving the rotor together by frictional force. After the introducing of the working principle, modal analysis is developed to tune the resonant frequencies of the longitudinal and bending vibration modes to be close with each other. At last, transient analysis is developed to gain the vibration characteristics of the motor, and the gained elliptical trajectory motions of particles on the driving parts verify the feasibility of the proposed design.