In order to improve the output performance, two novel TRUSMs (traveling wave rotary ultrasonic motor) with combined structures were designed and implemented. One was the TRUSM with two stators and single rotor, the other was the TRUSM with two stators and two rotors. Based on the structural characteristics, the mechanism that the stator/rotor contact state affected the output performance of these TRUSMs was qualitatively analyzed. In the comparative experiments，it was tested that the TRUSMs with combined structures had incomparable features to the single-stator-rotor TRUSMs. Experimental results indicate that the structural combination is an effective way to greatly improve the output performance, and the stator/rotor contact states are very important for the TRUSM performance. 

traveling wave rotary ultrasonic motor, combined structure, large torque, high energy density

为了进一步提高超声电机的输出性能，设计并实现了两种组合结构的行波型旋转超声电机(TRUSM)——双定子单转子结构和双定转子结构，并依据结构特征，定性分析了定转子接触状态对两种组合方式输出性能的影响。参照单定转子TRUSM，用对比实验检验了两种组合结构TRUSM的特点。实验结果表明，组合结构是大幅度提高TRUSM输出性能的一种有效方法，而且组合结构中的定转子接触状态对输出性能意义重大。

行波型旋转超声电机, 组合结构, 大转矩, 高能量密度