A new low voltage piezoelectric micromotor based on stator precessional motion

In this work a piezoelectric motor is described whose stator is composed of a cylindrical steel axle fitted at the center of a thin piezoelectric membrane. The rotor consists of a cylindrical permanent magnet, pressed in contact with the top surface of the axle, by means of magnetic forces. A travelling wave, at the natural flexural vibration of the thin piezoelectric membrane, is excited via the piezoelectric effect. The vertical displacement of the membrane is geometrically amplified by the central axle, obtaining a wide precessional motion of the axle. On this motion is based the transmission mechanism of the proposed motor. The motor is able to give a relatively high speed (/spl ap/3500 rpm) and torque (1.8/spl middot/10/sup -5/ N/spl middot/m) by using a commercial piezoelectric membrane (diameter 32 mm, thickness 0.2 mm), driven at relatively low voltage (18 V P-P). The very small thickness of the stator makes this motor suitable for microsystem applications. A simple analytical model of the transmission mechanism is discussed, and the predicted results are compared with experimental measurements, with a satisfactory agreement.