Ultrasonic Motor Using a Plate Vibrator with Projections.

In our previous paper, we have reported an ultrasonic motor using a plate vibrator with displacement amplification mechanism. But the maximum linear speed and the efficiency of the ultrasonic motor are only 0.075m/s and 1.58% respectively. And any optimum design of plate vibrator has not been shown yet. In this paper, by means of the finite element method, the vibration characteristics of a plate piezoelectric vibrator with projections for displacement amplification are analyzed. Some basic relations between structural dimensions and vibration state are given to obtain an optimum structure, and a new plate piezoelectric vibrator and ultrasonic motor are designed and manufactured. Through experiment, it is verified that the optimum design is appropriate and the resonance of the projection itself increases the displacement amplification effect. Measured maximum revolution, linear speed and efficiency are 900rpm, 0.65m/s and 8%, respectively.