A cylindrical micro-ultrasonic motor (stator transducer size: 1.4 mm in diameter and 5.0 mm long)

Ultrasonic motors are suitable for a micro-actuator because of a direct dri ve, no brake and their simple construction; In order to fabricate micro-ult rasonic motors, a piezoelectric thin film is essential. In this study, a hy drothermal method was adopted to deposit a PZT thin film. The dimensions of the stator transducer were: outer diameter, 1.4 mm; inner diameter, 1.2 mm ; and length, 5.0 mm. The resonance frequency of the stator transducer was 227 kKz, and the vibration amplitude was 58 nm(p-p) at an input voltage of 4.0 Vp-p. The maximum revolution speed was 680 rpm, and the maximum startin g torque was 0.67 mu Nm. The experimental conditions were 20 Vp-p and 5.3 m N pre-load. The motor property versus scale was investigated using an equiv alent circuit. The calculated results indicated that the output torque of t he 100 mu M diameter motor was 27 nNm. (C) 2000 Published by Elsevier Scien ce B.V. All rights reserved.