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The three-in-one electric drive system assembly of new energy vehicles plays a key technical role in the development planning of China's new energy vehicle industry, so more stringent requirements are put forward for the noise, vibration and harshness (NVH) level of the three-in-one electric drive assembly for vehicles. The noise source and transmission path of the three-in-one electric drive assembly are analyzed, and the relation between the modal frequency and stiffness of the motor controller cover plate and the noise of the electric drive assembly is studied. The modal frequencies of the upper controller and the controller cover plate in the electric drive assembly and the relation between them and noise are investigated. The modal optimization solution model of the electronic control cover plate is established, and the Optistruct module of Hyperwork software is used to obtain the best topology. This includes increasing the thickness of the electronic control cover plate, increasing the circumferential solar rib to increase the modal frequency and stiffness, and also increasing the acoustic wrap to optimize the vibration and noise of the electric drive assembly. After the stiffening treatment, the free mode frequency of the first-order assembly is increased by 209Hz, the increase is 22.9%, and the amplitude is significantly reduced. According to the relationship between stiffness and natural frequency, it can be seen that the stiffness of the optimized rear cover plate is significantly increased. Finally, we carry out experiments to verify the remarkable optimization effect of this scheme on the vibration and noise of the electric drive assembly. Through the comparison of the order slices of typical order noise, we observed that the 22th order of the first gear of the reducer, the 5.94th order of the second gear, and the 24th and 48th order of the motor noise, the amplitude of the corresponding vibration acceleration of the cover plate was reduced by 6 ~ 17dB, and the noise level of the electric drive assembly was effectively reduced.
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