Miniature piezoelectric ultrasonic rotary motors

This thesis presents the design, modeling and prototype fabrication of a new class of piezoelectric resonance devices that include ultrasonic motors and transformers.; The stator in the proposed motor consists of a piezoelectric ring poled in its thickness direction and bonded to a metal ring, having four arms located 90° apart on its inner circumference. The length and cross-sectional area of the arms on each metal ring are designed so that their bending or flextensional mode resonance frequencies match the radial mode resonance frequency of the stator. When a stator is driven at its first radial resonance frequency, the displacement in the radial direction is converted to one that is tangential. Since the bending or flextensional mode of the arms matches to the radial mode resonance, an elliptical motion is generated at the tips of each arm. The rotor with a truncated cone shape at the end is placed at the center of the stator. A rotation is generated due to the frictional force between the tips of the arms and the rotor surface.; The motor's stators were fabricated using commercially available piezoelectric rings. The metal couplers were cut using Electrolyte Discharge Machining (EDM). The structure of the motor is also highly scalable and driven with a single source. The size of the miniature motor, including the housing unit, is one of the smallest motors in the world. These motors were made using bulk piezoelectric ceramic materials. A motor 3.0 mm in diameter can generate a maximum torque of 50 μNm at 15.7 V when driven at approximately 468 kHz.; The high torque miniature piezoelectric ultrasonic motors presented in this thesis could initiate a new high-tech device technology in medical and information equipment as well as robotics.