Analysis And Optimization Of NVH Performance Of Electric Power Train

The comfort of driving is related to the electric power train which is the core part of electric vehicle,the NVH performance of electric vehicle is directly affected by the performance of vibration and noise of electric power train.With the promotion of the global electric vehicle boom,the NVH performance of electric power train has been paid more and more attention and gradually become the research focus of scholars.The theoretical analysis of the driving motor is carried out,and the mathematical expressions of the air-gap magnetic flux density and air-gap electromagnetic force of driving motor are obtained.The two-dimensional electromagnetic field analysis model of the driving motor was established by Maxwell,and the output torque fluctuation of the driving motor was obtained through simulation calculation by using the ideal three-phase sinusoidal current as excitation.The magnetic flux density and electromagnetic force of the air-gap magnetic field of the driving motor are calculated,then the spatial and spectral characteristics of magnetic field density and electromagnetic force of air-gap magnetic field are analyzed by Fourier transform.It turned out that the analysis results are consistent with the theoretical derivation results.Considering the stacking effect of stator core and winding mass,the structural finite element model of electric power train was established to perform the constraint modal analysis of the test bench installation status.Then,the dynamic analysis model of electric power train gear shaft system was established based on AVL EXCITE PU.The output speed and torque fluctuations obtained from the electromagnetic field analysis of the driving motor were used as the input of this dynamic analysis model.And the bearing force of each bearing in the gear shaft system was obtained through simulation analysis.Based on LMS Virtual Lab,the vibration response of the electric power train was calculated by the modal superposition method,and on the basis of this,the acoustic radiation noise analysis of the electric power train was carried out using the acoustic transfer vector method.The noise test of the electric power train was conducted in the semi-anechoic room,then the noise of the transient operating conditions was analyzed according to the order analysis method to obtain the noise characteristics of the electric power train.The accuracy of the simulation model was verified by comparing the A-weighted sound pressure level spectrum of the noise experiment with the noise simulation results.Taking the noise collected from the electric power train noise experiment as a sample,the subjective evaluation and analysis of the electric power train noise irritability was performed by using the grade scoring method,and the objective sound quality evaluation parameters of each noise sample were also calculated.Then the correlation and regression analysis of the results of subjective evaluation and objective evaluation parameters were conducted to establish a noise quality evaluation model of subjective evaluation and objective parameters.The noise of electric power train was analyzed based on 1/3 octave,and according to the sensitivity of psychoacoustic objective evaluation parameters to each frequency band,the gears were modified and the optimized excitation force was obtained.Then the optimized excitation force was reintroduced into the model for acoustic radiation analysis,and the objective evaluation parameters of sound pressure level spectrum calculation were obtained.The analysis finds that the noise quality is optimized.