In this paper, the characteristics of the electromagnetic noise radiated by an external rotor in-wheel motor (IWM) are investigated with the Doppler effect taken into consideration. First, Maxwell stress tensor method is employed to derive electromagnetic forces on the magnet surface. The effect of common current harmonics is also analyzed. Then, a structural model of the rotor is built and modal test is conducted to validate the model. Nodal forces, which are calculated by finite element method, are transferred from the electromagnetic mesh to the structural model for further vibration prediction. Finally, boundary element method is used to calculate the noise radiated by the rotor. In particular, the Doppler effect is considered. The calculated results are validated by the noise test. It is found that the end cap contributes more to the overall noise than the shell, and obvious sound directivity appears in the noise of the IWM. The noise measured perpendicular to the outer end cap is larger than that measured in other directions. In addition, the Doppler effect would induce additional side-frequency components around high-frequency peaks in the external rotor motor.

中文翻译：

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考虑多普勒效应的外转子轮毂电机噪声建模与分析


本文研究了考虑多普勒效应的外转子轮毂电机（IWM）辐射的电磁噪声特性。首先，采用麦克斯韦应力张量法导出磁体表面上的电磁力。还分析了常见电流谐波的影响。然后建立转子的结构模型并进行模态试验以验证模型。通过有限元方法计算的节点力从电磁网格传输到结构模型以进行进一步的振动预测。最后采用边界元法计算转子辐射的噪声。特别地，考虑多普勒效应。计算结果通过噪声测试进行了验证。结果发现，端盖对整体噪声的贡献大于壳体，IWM噪声中出现明显的声音指向性。垂直于外端盖测得的噪声比其他方向测得的噪声大。此外，多普勒效应会在外转子电机的高频峰值周围引起额外的旁频分量。