Piezoelectric ultrasonic motors using bulk PZT and utilizing two orthogonal bending modes of a hollow cylinder (part 2)

Our main objective was to design, fabricate and characterize piezoelectric ultrasonic motors for micromechatronic devices. Three different prototypes were fabricated. The stator part of the motors was composed of a composite structure; metal and piezoelectric ceramic plates. Owing to the partially square/partially circular outside surface, the stator had two degenerated bending modes that were orthogonal to each other. First stator was 10 mm in length. The outer and inner diameters were 2.4 mm and 1.6 mm, respectively. Dimensions of the second stator had been reduced by 50%. In the final design, length of the stator had reached to 4 mm and the rotor part of the motor had been changed from a solid rod to a spring. In addition, an optimization process was conducted on improving the displacement range of the stator of the piezoelectric micro-motor. When both modes were excited at a single resonance frequency, the resultant wobbling motion will provide higher displacement values, which in turn will provide higher torque.