| Summary: | 碩士 === 國立中正大學 === 機械系 === 89 === ABSTRACT
An ultrasonic motor is a type of actuator that uses mechanical vibrations in the ultrasonic range as its drive source. Human ears are capable of detecting sound waves from 50 Hz to 20kHz.This is called the audible frequency range. Ultrasonic waves are sound waves or mechanical vibrations with frequencies above 20kHz.The use of ultrasonic waves is a direct outcome of using piezo-electric ceramics, which expand or contract in accordance with an applied electric field, as the vibration source. In the ultrasonic motor, a voltage is applied to the piezoelectric ceramic element to generate alternating expansions and contractions, either in the ceramic body itself or in an attached metal piece. The magnitude of these oscillations is extremely small, of the order of 1µm. In order to obtain a higher gain, the resonance effect of the ceramics in the ultrasonic range is utilized.
The oscillations are mechanically rectified in the motor to obtain unidirectional movement. Although the magnitude of an individual cycle of the movement is of the order of mircometres, it is possible to obtain high speeds, owing to the high frequency(tens of kilohertz).
In office equipment such as printers and floppy disk drives, market research indicates that tiny motors smaller than 1cm would be in large demand over the next ten years, however using the conventional electromagnetic motor structure, it is rather difficult to produce a motor with sufficient energy efficiency. Piezoelectric ultrasonic motors, whose efficiency is insensitive to size, are superior in the mm-size motor area.
|
|---|
