Analysis And Control Of The Coupled Structural-Acoustic Vibration In Vehicle

The vibration and noise problems of passenger compartment in vehicles having been an important restriction for its rapid development. At present, the processing methods of vibration and noise signal and the assessment tools of vibration response in vehicles are still immature. Therefore, the systematical studies on the feature extraction method of vibration and noise signal and the method of the statistical estimation method of vibration response in vehicles has not only important theoretical significance, but also practical value.For the research of noise, vibration and harshness (NVH) in vehicle, a further study into the feature extraction method of vibration and noise signal and the statistical estimation method of structural vibration response have been made in this paper. The main contents of this paper are summarized as follows:(1) A novel method for suppressing the strong background noises in the feature extraction of vibration signal is proposed. According to the characteristics of vehicle vibration and noise signal, after comparing some presently applied feature extraction methods, it proposed a new method: multi-correlation of time series and empirical mode decomposition. Which can eliminate the effect of zero-average noise in sampling series, get over the difficulties of frequency identification in the subsequence analysis that caused by strong background noise, protrude the feature components of original signal, is of preferable for nonlinear, non-stationary vibration signals. This method has no special restrictions for the type and strength of noise, and a strong adaptability. After the processing of multi-correlation of time series, it provides a wonderful former data for spectrum analysis; then from using empirical mode decomposition, it can sufficiently put up the needed feature signal, and plus little increase in computational time.(2) A method which can analyses the vibration response of the variable mass plate is presented. Based on the Lagrange's dynamics equation and Rayleigh-Ritz energy method, the response analysis method is described and the statistical character is pointed out. It demonstrated the proposed method using Monte Carlo number simulation.(3) Based on the proper orthogonal decomposition (POD), the statistical estimation method of vibration response, when the correlative excitations acting on the structure, is proposed,and the relative deviation calculation expression and calculation method of load parameters in response statistical estimate is given. The results indicate that the statistical analysis of response is directly connected with the relativity of the input excitation and the correlation of nature frequency, the relative deviation decreases gradually with the increment of vibration frequency, the calculation expression of relative deviation which considered the excitation relativity and correlation of nature frequency can in concordance with the result of experimentation better.(4) The statistical estimation method of response and the calculation method of load parameters in the complex coupling system which using statistical energy analysis (SEA), The results show that: the load parameters is connected with the ratio of the input energy of the subsystem and the input energy of the whole system, and with the load parameters of the subsystem; the irrelevant excitation is a special case of correlative excitation, they can be expressed in a unified expression. The experiments of complex system response statistical estimation have shown that: considering the correlative excitations, the calculation results of the average energy are better consistent with the result of experiment. With the increment of vibration frequency, the influence of correlative excitation gradually weakened, when the number of transmission paths increased, the relative deviation of subsystem response gradually increased.In conclusion, the two areas, the feature extraction method of vibration and noise signal and the statistical estimation method of vibration response of NVH in vehicle, are systematically studied in this paper. The results has an important theoretical significance and engineering applications for improving vehicle NVH performance, guiding vehicles NVH designs, as well as the later revisions of the structure.