| Vehicle interior NVH performance is one of issues which are concerned by the car manufacturers and consumers, and powertrain mounting system is very important subsystem that has an great influence on occupant comfort.So selecting the appropriate system can reduce noise and vibration of vehicle interior.This paper based on the background of engineering and the research results also directly applied to engineering practice. It takes a medium-sized bus interior NVH performance improvement as the design goal and optimize its engine parameters characteristic of powertrain mounting system and improve their body ceiling structure through the noise and vibration test, spectrum analysis, order analysis, computer simulation, optimization design theory and technology. Its main contents are as follows:(1) The whole vehicle NVH performance testing and diagnostics. It takes the a medium-sized bus which is made in China as the research object. It determines the vibration transmission path and the dominant factor that leads to low idle noise and vibration inside the car is the quality of diagnostic conclusions engine powertrain mounting system through the vibration of the vehicle 11 measuring points, noise and vibration noise test signal 12 measurement points, according to the noise spectrum, order maps, color maps sound frequency domain analysis, order features and noise source contribution analysis of vibration signal spectral characteristics.(2) Introducing the basic theory and principles of high-dimensional nonlinear approximation model and mainly describing the BPNN-HDMR TPS-HDMR high-dimensional approximation model methods. It has a brief introduction about Kriging-HDMR and RBF-HDMR high-dimensional approximation model methods and analyzes the process of building four high-dimensional models and their basic characteristics, explains their respective characteristics and scope of high-dimensional approximation models base on the comparative analysis of the accuracy and efficiency.(3) Establishing passenger car sound field acoustic coupling model and engine powertrain mounting system of high-dimensional approximation model. It takes the parameters optimization of bus engine mounting system as the background to establish a noise field coupling CAE model inside the vehicle and verifies the credibility of the model by comparing simulation results with test results. In this paper, the stiffness and damping of the engine mount point are taken as the four design variables, and it takes the lowest sound pressure level at the main driving right ear as the optimization goal when the bus is idling so that establish the function approximation model of driver's seat RMS vibration, sound pressure level at the driver's right ear with the engine at a four-point suspension stiffness, damping, based on the TPS-HDMR, and it has been optimized the results; Finally, it raises the design proposals about the stiffness damping parameter combination of the bus powertrain for four-point suspension.(4) Analysing bus body vibration to interior noise acoustic contribution and improving body ceiling structure design. It established bus body finite element model and the internal bus tune acoustic model and confirmed the ceiling panels acoustics greatest contribution at the driver right ear through the body structure panels acoustic contribution analysis, and then the bus body ceiling panels were molded freedom modal analysis, and extract the internal bus tune acoustic modes. Modifing the bus roof structure through shifting body and interior ceiling sound mode frequency, inhibiting the engine vibration second order mode frequency shapes access to the body ceiling modal frequency; and finally it has been better optimization results through comparing the internal bus acoustic quality before and after optimization. It has a direct guidance value to improve the NVH performance of the vehicle and also verifies the correctness of the optimization results. |
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