Zhang Dongsheng, Wang Shiyu, Xiu Jie
School of Mechanical Engineering, Tianjin University, Tianjin 300072, PR China; College of Aeronautical Engineering, Civil Aviation University of China, Tianjin 300300, PR China.
School of Mechanical Engineering, Tianjin University, Tianjin 300072, PR China; Tianjin Key Laboratory of Nonlinear Dynamics and Control, Tianjin 300072, PR China.
Ultrasonics. 2017 Nov;81:118-126. doi: 10.1016/j.ultras.2017.05.013. Epub 2017 May 25.
Elastic wave quality determines the operating performance of traveling wave ultrasonic motor (TWUM). The time-variant circumferential force from the shrink of piezoelectric ceramic is one of the factors that distort the elastic wave. The distorted waveshape deviates from the ideal standard sinusoidal fashion and affects the contact mechanics and driving performance. An analytical dynamic model of ring ultrasonic motor is developed. Based on this model, the piezoelectric parametric effects on the wave distortion and contact mechanics are examined. Multi-scale method is employed to obtain unstable regions and distorted wave response. The unstable region is verified by Floquét theory. Since the waveshape affects the contact mechanism, a contact model involving the distorted waveshape and normal stiffness of the contact layer is established. The contact model is solved by numerical calculation. The results verify that the deformation of the contact layer deviates from sinusoidal waveshape and the pressure distribution is changed, which influences the output characteristics directly. The surface speed within the contact region is averaged such that the rotor speed decreases for lower torque and increases for larger torque. The effects from different parametric strengths, excitation frequencies and pre-pressures on pressure distribution and torque-speed relation are compared.
弹性波质量决定了行波超声电机（TWUM）的运行性能。压电陶瓷收缩产生的时变圆周力是使弹性波发生畸变的因素之一。畸变后的波形偏离了理想的标准正弦形式，影响了接触力学和驱动性能。建立了环形超声电机的解析动力学模型。基于该模型，研究了压电参数对波畸变和接触力学的影响。采用多尺度方法获得不稳定区域和畸变波响应。通过弗洛凯理论验证了不稳定区域。由于波形影响接触机制，建立了一个涉及畸变波形和接触层法向刚度的接触模型。通过数值计算求解该接触模型。结果验证了接触层的变形偏离正弦波形且压力分布发生变化，这直接影响了输出特性。对接触区域内的表面速度进行平均，使得转子速度在较低扭矩时降低，在较大扭矩时增加。比较了不同参数强度、激励频率和预压力对压力分布和扭矩 - 速度关系的影响。
