Optimum design for stress type hybrid ultrasonic motor using longitudinal and torsional vibration modes

A kind of stress type hybrid ultrasonic motor using longitudinal and torsional vibration modes (LTUM) was developed. Structure optimum designs were carried out to the stress-type LTUM. It was put forward that the longitudinal PZT should be placed on the end surface of the stator, and the operating mechanism of the motor was analyzed. The FEA software ANSYS was used to analyze the structure parameters which affect the first order torsional vibration mode and the second order longitudinal vibration mode. The method to realize the frequency coherence between the first order torsional vibration mode and the second order longitudinal vibration mode was put forward. The experiments for the stress-type LTUM with double rotors show that when the non-linear spring is used for applying pre-pressure, the load characteristics of the motor is better and the stalling torque of the motor with diameter in 20mm has reached 1.28N·m, and the torque/diameter ratio has reached 64N.