Cylindrical micro ultrasonic motor utilizing bulk lead zirconate titanate (PZT)

Ultrasonic motors are expected to be used as microactuators because of their high torque, low speed and simple construction. We have already reported cylindrical-shaped micro ultrasonic motors which utilized a lead zirconate titanate (PZT) thin film. In this paper, we discuss a micro ultrasonic motor composed of bulk PZT. The stator transducer had dimensions of 2.4 mm in diameter and 10 mm length. The maximum revolution speed was 650 rpm and the maximum output torque was 0.22 mNm with the condition of 100 Vp-p input voltage. The driving frequency was 85 kHz. The comparison between the bulk PZT stator transducer and the previous PZT thin film transducer was considered. From this consideration, the e(31) piezoelectric factor was determined to be the main factor for different output torques. The bulk PZT motor was applied to robot hands which was a simple procedure. A two axes hands application was successfully operated with a step motion and carried up to a 10g load.