An ultrasonic step motor is provided with a stator and rotor. The rotor has a plurality of projections extending in the direction of the stator so that contact is made between the rotor and the stator creating a frictional force to drive the rotor. Vibrators are formed from a piezoelectric material directly...http://www.google.com/patents/US5247220?utm_source=gb-gplus-sharePatent US5247220 - Ultrasonic motor