Research On Road Noise Analysis And Optimization Of New Energy Vehicles Based On Transfer Path

The low-frequency road noise of electric vehicle is a severity problem contrast to traditional oil-fueled vehicle,while electric vehicle use motor as power source,and the noise is more easy to user perception for customs because of lacking of drive power train.So the analysis and optimization for road noise is the key to improve NVH of electric vehicle.In order to be improve road noise performance of the electric vehicle,this paper apply transfer path analysis method and establish a FEM model,which include chassis,body,air cavity etc.,but not include tire assembly.The lowfrequency road noise of electric vehicle is optimized and research by the method of experiment and simulation.First,road noise is the main problems for electric vehicle in the rough surface road.The basic theories and terms of NVH are briefly summarized,and the mechanism of road noise and its influencing factors are described according to the basic principles of NVH.Road noise excitation was transmitted to human ear through tire,suspension and body.So in principle,the road noise performance can be optimized from two major directions:reducing excitation and optimizing transmission path.Secondly,the road noise performance optimization of a electric vehicle was taken as an example.The vibration acceleration of the wheel center was test.The wheel center load was calculated through transfer path analysis and inverse matrix principle.Four wheel center loads could be input into the vehicle finite element model to simulate the noise results.An accurate vehicle finite element model was established.According to the transmission path analysis principle,the contribution of road noise of the electric vehicle was analyzed.It was found that the main road noise problem was in the frequency range of 30Hz to 60Hz,and its main contribution was the rear suspension.According to the results of contribution analysis and working deformation analysis,it was determined that the excitation of the problem point was mainly transmitted to the sub-frame through the control arm of the rear suspension and then to the body through the sub-frame,which causes a large vibration energy on the front beam of the top cover of the body,and finally causes a large peak value of sound pressure in the car at 30HZ-60Hz.Finally,according to the results of simulation optimization analysis and the scheme,the effectiveness of the scheme is verified by the actual vehicle.It was found that the optimization of the front beam structure of reduces the peak value of the 40Hz sound pressure in the car by about 4.6dB(A),and the optimization of the bushing structure of the upper swing arm also contributes to the peak value around 40Hz,but the effect of this scheme on the total sound pressure level was not obvious.The total sound pressure level decreased by 1.5dB(A)by adding double vibration isolation at the sub-frame and body mounting points.Through the method of combining test and simulation,it was verified that the simulation optimization method can quickly locate the weaknesses of chassis and body,and an effective optimization scheme can be developed for the weaknesses.Meanwhile,it can provide reference for the optimization of road noise performance of other vehicles.