Design of thin cross type ultrasonic motor

Abstract

This paper proposes a newly designed structure for a thin ultrasonic rotary motor. A thin brass plate is used as a cross-shaped vibrator and sixteen ceramic plates are attached to the top and bottom sides of the brass plate. To find the optimum size for the prototype motor, the stator motions were simulated using ATILA by changing the length and thickness of the ceramics. In the results, the stators commonly had three resonance peaks on the admittance curve; the contact tips of the stator moved at trajectories tangential or normal to these resonance peaks. Elliptical displacements of the tips were obtained at off-resonance frequencies. The maximum displacements at the resonance peaks were compared and the maximum displacements of the contact tips were obtained at a length, width, and thickness of 18, 3, and 1.8 mm respectively. With the fabricated prototype motor, high rotational speeds were obtained by applying relatively low voltages. Speed and torque were increased linearly by increasing the voltage. However, torque decreased when the input voltage went over 24 V.