A hollow cylindrical linear nut-type ultrasonic motor

A hollow, linear, nut-type, ultrasonic motor based on two degenerate, 3rd-order bending modes in the section plane of cylinders is presented in this paper. The stator and rotor of the motor are both cylindrical and hollow, making the motor appropriate for applications where a light path, electric wire or optic fiber is required to pass through the motor. A new structure with four PZT plates bonded on the stator is proposed here. and the other had all eight sides bonded with PZT plates. The results show that the new design with four PZT plates has a higher mechanical quality factor, vibrates with larger amplitude, and has comparable performance to the stator with eight PZT plates. The motor with four PZT plates reached an upward speed of 0.95 mm/s when the load force was 3 g, and the maximum thrust force was 0.35 N. Two stators were fabricated and studied.