A Square-type rotary ultrasonic motor using longitudinal modes

This study proposes and studies a new rotary ultrasonic motor, which consists of one square-type metal frame and eight pieces of PZT ceramics. Four metal beams with exponential shape horns are located in square-type to form the enclosed frame. The PZT ceramics are bonded on the upper and lower surfaces of the four beams respectively. By applying sine and cosine signals on the PZT ceramics, the longitudinal vibrations of the piezoelectric-metal composite beams can be generated alternately, which can produce circular movements on the four feet located at the corners of the square-type metal frame. The structure, working principle, design, and analysis of the proposed ultrasonic motor are introduced. Vibration characteristics and mechanical output performance of a prototype are measured to verify the feasibility of the proposed design. Maximum speed and torque of 106 rpm and 0.29 N · m are achieved by the prototype.