中文摘要：

压电陶瓷（Piezoelectric ceramic,PZT）是组成超声波电动机定子的核心元件,其性能的优劣将直接影响超声波电动机的输出性能。为了研究PZT对超声波电动机定子特性的影响,利用有限元法建立超声波电动机自由定子的机电耦合动力学模型,利用该模型重点研究PZT厚度、极化分区形式、极化不均匀性以及PZT开路和短路条件时对定子动态特性的影响,并提出基于能量的PZT极化分区形式、极化不均匀性对定子动态特性影响程度的评价方法。采用自然对流传热问题的牛顿冷却定律和热容理论,建立超声波电机定子的温度特性理论模型,基于该模型研究PZT材料介电损耗对电动机定子的温度特性影响。研究结果表明：电动机定子模态频率随PZT厚度的增大而增加,而定子表面质点的振动幅值则随PZT厚度的增加而减小;PZT开路时的定子模态频率比短路时的模态频率大;改进PZT极化分区形式和极化不均匀性均可以提高超声波电动机自由定子的动态特性。基于该研究结果制作的直径10.4mm行波型超声波电动机性能稳定,堵转力矩达到9.5mN·m,空载转速1000r/min,研究结果有助于超声波电动机的产业化。

英文摘要：

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.