Abstract: The piezoelectric ceramic(PZT) is one of the key elements of the ultrasonic motor stator, its performance greatly affects the output characteristics of the ultrasonic motor. In order to research the effects of PZT on the output characteristics of ultrasonic motor, the electromechanical coupling dynamics model of the free stator is built by using finite element method . Based on the model, the effects of the thickness, polarization partition format and polarization inhomogeneity of the PZT on the stator dynamic performance are studied. And the energy evaluation method of the effects of the PZT on the stator dynamic characteristics is proposed. Meanwhile, The theoretical model of temperature characteristics of the ultrasonic motor stator is built by using Newton cooling law and heat capacity theory. Based on the model, the effect of dielectric loss of PZT material on the temperature characteristics of the stator is researched. The results show that the stator modal frequency increases with the enhancement of PZT thickness, while the vibration amplitude of the stator surface particle decreases with the increase of PZT thickness. Meanwhile, the stator modal frequency when PZT is in open circuit condition is greater than that when PZT is in short circuit condition. Based on the research results, a prototype of traveling-wave type ultrasonic motor with 10.4 mm diameter is produced, experiments show that the maximum torque of the motor is 9.5 mN•m, the no-load speed is about 1 000 r/min. The research results are helpful to the industrialization of the ultrasonic motor.

Key words: Energy, Finite element model, Piezoelectric ceramic, Stator performances, Temperature, Ultrasonic motor