Vehicle NVH Design Theory And Approach Using System Target Programming

Automotive NVH design includes forward design and trouble shooting and involves optimized design and multidisciplinary analysis,which make the NVH design problem extremely extensive and complex.Although there are some solutions to parts of NVH problems,it is essentially a “one(specific method)to one(specific problem)” relationship,and failed to form a set of universal design method system.In addition,all valued research results of engineering applications in this field are regarded as the core technology of enterprises(foreign capital)and they keep secret strictly,which makes it difficult for the domestic automobile industry to obtain these core technologies through conventional means.Therefore,it is necessary to study automobile NVH design issues from a new perspective.In this thesis,vehicle NVH forward design and trouble shooting has been in-depth studied and the optimal design throught based on NVH level decomposition system has been explored.A new optimal design solution is put forward,and the engineering case analysis of NVH design and development is carried out to solve the key technical problems of NVH forward design and trouble shooting,in which the accuracy was ensured while improving the computational efficiency.The main work of the research is as follows:(1)The system of NVH target decomposition is proposed and its concept is explained.Based on the consistency of NVH target decomposition and design process and relying on multi-level vehicle NVH design goal planning,an all-round vehicle NVH design system is put forward which includes "vehicle","system","subsystem" and the "parts".This system mainly involves the establishment of NVH hierarchical decomposition architecture and the numerical analysis of NVH hierarchical decomposition architecture,which can be applied to the vehicle NVH forward design and trouble shooting.On this basis,the construction steps of NVH level decomposition system has been developed and the modeling framework of NVH level decomposition system has been built.(2)The design algorithm of NVH hierarchical decomposition system of automobile is studied and the steps of numericalization of NVH hierarchical decomposition architecture are proposed.A model of the two-level decomposition system was established by using the intelligent optimization algorithm,the hierarchical mapping model and the interval search strategy.At the same time,it was refined into a single-objective two-level model and a multi-objective two-level model.These models are verified by the theoretical mathematical meyhod(Error within 6%).On this basis,the design algorithm is extended to the multi-level decomposition system model,and an innovative optimization method called generalized inverse method is formed.The "optimization goal" of the method is no longer an exact target value,but a possible range of the target vector,which makes the method more general and robust than the traditional optimization design method in the engineering application.(3)Through the proposed "generalized inverse method",two typical vehicle NVH design problems including suspension damper anti-noise design,engine mounting vibration isolation design were analyzed.The corresponding NVH hierarchical decomposition architecture is established for the two design problems,and the optimal design interval of each design variable under target requirements is solved by the generalized inverse method.The correctness of the calculation result is verified.The results show that the generalized inverse method can be applied to the above NVH forward design problems.On this basis,the vehicle NVH forward design flow and bench have been generalized.(4)Through the proposed "generalized inverse method",two kinds of NVH trouble shooting problems including vehicle starting judder problem and vehicle chassis structure noise problem were analyzed.The corresponding NVH hierarchical decomposition architecture is established for the two diagnostic problems.The design variables are screened by contribution analysis or subjective evaluation,and the generalized inverse method is used to solve the design variable fault interval when the design target fails.Then,the causes of the faults were further analyzed and investigated.According to the diagnosis results,the vehicle was rectified and verified by experiments.The results show that the generalized inverse method can accurately and quickly diagose the above NVH trouble shooting problems.On this basis,the vehicle NVH trouble shooting flow and bench have been generalized.(5)A vehicle NVH analysis and diagnosis software is designed and developed.In order to analyze the vehicle NVH problems more convenient,the generalized inverse method flow was modularly designed,and a NVH analysis and diagnosis software including data input,analysis,diagnosis,data display and results export has been developed.Meanwhile,to effectively manage kinds of data and files,the Python language,Django framework,Mysql database and Apache is used to construct an engineering database system.The developed analysis and diagnosis software with GUI can be used to analyze vehicle NVH problems.