Transfer Path Analysis And Optimization Of A Vehicle On In-Vehicle Vibration And Noise

With a steady development in the domestic automobile market, people pay more attention on vehicle NVH performance which becomes a vital index to evaulating a vehicle. In addition, SUV should have a certain off-road ability so that a good vibration and noise level of in-vehicle will help the driver to concentrate on his driving task and improving the safety as well.This essay is based on the transfer path analysis method, which is combined with vehicle tests and the Finite Element Method to analyze in-vehicle vibration and noise caused by the engine, predict the noise level of the vehicle. According to the tests in a semi-anechoic chamber, vehicle frequency response functions are obtained for the measured points in idle and wide open throttle conditions with a decoupling powertrain. It is concluded that the vibration and noise level of the vehicle in the idl e condition can meet the design requirements, but the in-vehicle noise on the 2500r/min and 4000r/min show obvious peaks in the wide open throttle condition. The inverse matrix method is used to calculate the excitation point load of the engine, and finally the validity of the results is verified.The finite element model of the body in white is established to analyze its freedom modal, and the results are compared with the experimental modal which is validated. Based on the frequency response analysis of the finite element model which the excitation point load is used as input, it infers that the Y-direction of 1st exhaust hook and the Z-direction of rear mount are the major factors of noise peak in the wide open throttle condition. Through the analysis of the transfer function and the loads condition, it needs to add a bearing to the sub-frame, and analyze the noise level of the vehicle. The results show that the noise peak values have decreased 3-5d B(A) in the wide open throttle condition, which significantly improves the vehicle’s noise level.