Development of a miniature foil type ultrasonic motor

In this paper, a traveling wave type miniature ultrasonic motor using a foil type stator is proposed. The developed motor has a simple mechanism without being a piezoelectric vibrator in itself. Traveling waves from the vibrator source propagate to the foil type stator through the long-length waveguide. Unlike an ordinary ultrasonic motor, the developed motor rotates in the same direction as the traveling wave. To clarify the reverse rotational phenomenon, transient response analysis was executed. The result showed that the foil type motor driving principal was different from that of the general ultrasonic motor which was driven by elliptical motion of the elastic body surface, the main driving force was the generated symmetric lamb wave which rotates the coil surface forward direction. A rotation experiment using the developed prototype motor was executed. Rotational speed was found to be 6,380 rpm and starting torque was 698.8 µNm when the ideal gap between rotor and stator was realized.