A type of ultrasonic motor whose stator is composed of a torsional vibrator and multilayered piezoelectric actuators is proposed and has been fabricated for trial. The stator is operated at the resonance frequency of the torsional vibration. The vibrator generates the mechanical output force and the actuators control the frictional force. The construction provides for arbitrary Lissajous's figures at the contacting surface and contributes to large mechanical output power with high efficiency and bidirectional motion. It also gives greater freedom of design. The prototype motor produced a maximum torque of 7 kg-cm and a maximum efficiency of 33%.
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