Identification And Control Of Vehicle Interior Low-frequency Structure-borne Noise Based On Transfer Path Analysis Method

Vehicle interior noise is one of the main indicators of the vehicle NVH(Noise Vibration and Harshness) behavior, and directly determines the quality and market competition of the whole vehicle. Facing the fierce market competition and accelerating development trend of new models, the low-frequency structure-borne noise is one of the most important research topics of automotive research and development. This dissertation proposes a kind of technology method for rapid identification and effective control of vehicle interior low-frequency structure-borne noise, and carries out the key technology research on the generating mechanism and control strategy of interior noise.In order to accomplish fast identification of vehicle interior structure-borne noise, transfer path analysis of structure-borne and airborne is proposed synchronously based on the OPAX method. With an actual model as the research object, the exciting forces and acoustic loads are estimated, whose results are verified by the results from the single path inversion method. The results show that exhaust noise is main reason of vehicle noise at 1600 rpm, while structure-borne contributions in X direction of left-mount and Z direction of hanger 1 are main reason of interior noise at 2700 rpm.So as to obtain more reliable dynamic simulation model of BIW(Body In White), the validation and optimization methods of BIW are improved. With the Effective Independence Weighted Average Acceleration Amplitude(EI-WAAA) method of experimental modal testing, the reliable experimental modal data are obtained efficiently. Next, the optimized locations and parameters of simulation model are determined using the Modal Assurance Criterion Contribution Analysis(MACCA) and sensitivity analysis methods. The results show the modal frequencies error is less than 5%, and MAC value is more than 0.8, which mean the more reliable model is built.To get the more accurate acoustic-structure coupling hybrid model of BIW. The acoustic modality of car cavity is analyzed firstly. The coupling surface mapping technology is adopted to establish the acoustic-structure coupling model with the optimized BIW and car cavity. Then the hybrid model is built based on acoustic-structure coupling model and experimental analysis results using matrix inversion method. At last, the interior noises are predicted according to modal superposition method. The results show that there is a high consistency in the order 2 and order 4, and the reliability of the model is verified.To find the optimized locations of damping material treatment, the panel contribution coefficient of multi-condition, multi-filed point and multi-frequency is defined. With two field points in two kinds of conditions for the four main frequencies of the actual vehicle model as the control target, the optimized locations of damping treatment is determined. Then, the concept of modal strain energy weighted average is put forward. The modal strain energy of two global modes and five local modes is analyzed. The optimized locations to the layout of the damping material are compared with the results of the improved panel acoustic contribution analysis method. A comprehensive process including the two methods is given for the layout of the damping treatment. The locations of damping treatment are left-front floor, right-front floor, left-middle floor, right-middle floor, floor tunnel rear floor and trunk.At last, the suitable damping materials are selected and the results are validated. The dynamic stiffness of key points of vehicle body are tested when the different damping materials are pasted the body. Considering the other factors such as cost, mass and temperature range, the wide temperature damping materials is chose. The measurement results show that vehicle interior noise has been effectively controlled for the selected damping materials, especially reduced by 1.1~3.7 d B(A) in order 2 and order 4.