ULTRASONIC PIEZOMOTOR WITH A PIEZOELECTRIC ANGLE DETECTOR

An ultrasonic piezomotor with a piezoelectric angle detector has been developed. For a piezomotor control unit, a simple rotating angle detector is required, as well as increased reliability. To meet this requirement, a piezomotor with a piezoelectric angle detector, using single piezoelectric ceramic ring plate, has been developed. The rotor in this piezomotor is composed of a lining ring plate, a spring and a piezoelectric angle detector. The angle detector is held between the lining ring plate and the metal base disk in the rotor. The phase difference, between vibration in the stator and vibration detected by the piezoelectric angle detector, is in proportion to the rotation angle. Using this proportional relation, the piezomotor is able to detect the rotation angle. Incremental pulses are generated with interpolating the phase difference. Using a formula examination, one of the factors leading to the angle detection errors has been analyzed. In spite of the small size (15 mm x phi-30 mm) and light weight (50 g), this piezomotor has great performance, that is, rotation angle detection (360 pulse per rotation) with only a few parts, well controlled ability, and high torque. Applying this piezomotor to printer-scanner systems, great reductions in thickness have been achieved, while not detracting from reliability.