| The car seat is the most direct contact with the occupant in cars,and its vibration characteristics affect the ride comfort directly.The study of the vibration characteristics of the seat is an important part of automobile research.As the comfort requirements of consumers increase,the NVH performance of vehicle,such as seat vibration,abnormal sound etc.,have attracted more and more designers attention,and have been become an important index to evaluate the seat comfort.In this paper,the seat vibration characteristics were analyzed by modal analysis and 4-channel frequency scanning experiment for the abnormal vibration problem of the left and right seats in a certain commercial vehicle found in the road test,and benchmarked by finite element method(FEM).Then,the main paths of vibration transmission were obtained by the vibration contribution analysis and transfer function calculation by using the Transfer Path Analysis(TPA)and CAE(Computer Aided Engineering)technology.The optimization scheme was proposed to solve the seat vibration problem based on the above analysis results.The main researches and the results are as follow:1.The finite element models of the seat and the body in white(BIW)were established on the finite element analysis software HyperWorks,and the modal analysis was carried out by MSC.Nastran to obtain the previous two modes and frequencies of the seat vibration.The results showed that the frequency of Fore/Aft mode was 17.12 Hz and the frequency of Lat.Bend mode was 20.49 Hz.However,the frequency of Fore/Aft mode and Lat.Bend mode,obtained by the seat modal test on the LMS test and analysis system,was 17.8Hz and 18.6Hz,respectively.The error between the simulation results and the experimental results was within 10%,which verified the reliability of the FEM simulation.2.The 4-channel frequency scanning test of the seat showed that the peak of the X-direction vibration acceleration at the top of the seat back reached a peak value of0.06 g at the frequency of 17.84 Hz,which was consistent with the vibration characteristics obtained in the road test.The 4-channel frequency scanning test was simulated by CAE technology,and the results showed that a local peak of the seat vibration acceleration occurred when the modal frequency coincided with the excitation frequency.The simulation results were basically same as the experimental,and were credible for the error was within 15%.3.The frequency response analysis was carried out using Multi-Level TPA and CAE technology to obtain the transmission characteristics of vibration in the seat.According to the multi-level TPA theory,the vehicle system was divided into BIW system and seat system,and the corresponding transfer functions were established to study the transmission characteristics of vibration in the whole system and subsystem.The main excitation source,obtained by the contribution of vibration,was the X-direction excitation at the Front-Right suspension connector.Then the vibration transfer path was obtained by comparing and analyzing the transfer functions.The results showed that the main path of vibration transmission was the Front-Right suspension connector X-direction ? seat mounting Z-direction ? seat back top X-direction,which provided the basis for further optimization.4.The optimization scheme was designed according to the results of transmission path analysis,and the 4-channel frequency scanning test and the road test were carried out.The results showed that the seat back vibration acceleration reduced by about 40.7%.The abnormal vibration problem of the seats was successfully solved and resultantly the ride comfort was improved. |
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