Study And Application Of OPAX Method Based On Wavelet Denoising Technology

Transmission path analysis(TPA)is an effective method to identify vehicle vibration source and noise source.The theory is becoming more and more mature,and a variety of analysis methods based on traditional transfer path analysis(CTPA)have been formed.In this paper,with the support of liaoning natural science foundation project,the method of transmission path analysis(OPAX)of extended working condition is studied.In the model establishment of the transmission path in the extended working condition,the signal at the input end is obtained by the vehicle under the acceleration working condition,which is inevitably mixed with noise signal,which affects the accuracy of load identification and leads to errors in the calculation of vibration contribution of each transmission path.Based on this problem,this paper adopts wavelet noise reduction technology to improve the OPAX method.By analyzing the advantages and disadvantages of the two classical threshold methods,the wavelet decomposition coefficients of the effective signal and the noise signal have a large difference after wavelet decomposition,and the optimal threshold value suitable for processing the noise signal is determined.The new wavelet threshold and new wavelet threshold functions are constructed by combining the advantages of the two classical threshold functions.The determination coefficient,signal-to-noise ratio,root-mean-square error and smoothness in the regression analysis are used as the evaluation benchmark for the accuracy identification of the contribution of each transmission path by OPAX method.Taking a domestic SUV as the research object,a transmission path analysis model was established.The vehicle vibration transfer test was carried out,and the vibration acceleration signal and frequency response function at each suspension and target point were measured under the condition of uniform acceleration.The measured acceleration signal was denoised by wavelet threshold,and the vibration contribution of each path to the target point before and after denoising was calculated by OPAX module.By comparison,it is found that the measured value of the path vibration contribution of the improved OPAX method is more consistent with the fitted value.The root mean square error,signal-to-noise ratio,smoothness and determination coefficient of the model changed from 0.0579,7.2359,0.1509 and 0.7953 before the improvement to 0.0119,11.9759,0.0009 and 0.9559 respectively.The improved OPAX method accurately locates the order of the main contribution of vibration excitation at the second order.In particular,the frequency range of the main vibration contribution of the improved OPAX method was significantly reduced from 27.78Hz-33.91 Hz,44.73Hz-60.78 Hz,and 69.25Hz-81.97 Hz to 30.47Hz-34.44 Hz,49.27Hz-58.05 Hz,and 72.28Hz-79.24 Hz,respectively.Thus,it is shown that the new threshold function constructed in this paper takes into account the advantages of the two threshold functions,and effectively improves the analytical accuracy of the OPAX method for the analysis of the transmission path of the extended condition.