A Convex Shaped Radial-Torsional Ultrasonic Motor with Built-in Galaxy Wave Transmission

A plate type standing wave ultrasonic motor which uses built-in galaxy wave transmission mechanism to realize radial-torsional mode conversion is proposed in this paper. Operating principle of the motor is demonstrated, appropriate resonance frequency has been found, and the geometric parameters have been optimized by finite element model analysis. A prototype motor was assembled and a dedicated driver was designed for the purpose of portability, ministration and integration. Dual pulse width modulation (PWM) structure circuit of the driver was designed to achieve the independent control of output voltage amplitude and frequency, which has advantages of control agility and large dynamic adjustment range. Experimental studies were carried out for ultrasonic motor prototype. Maximum no-load speed was measured of 1500 r/min and a maximum output torque of 0.2N $\cdot m$ under the exciting voltage of 150V PP and the frequency of 38.1 kHz. The experimental investigations revealed that the motor has good mechanical output performance under lower driving voltage.