Study On Identification Method Of Multi-correlation Vibration And Noise For Vehicle Gearbox

In order to identify the noise and vibration sources of gearbox,a signal processing method of combining S transform with singular value decomposition was proposed,and the periodic impact feature of gearbox planetary gear and bearing failure was identified by reducing noise.Another signal processing method of combining S transform with synchrosqueezed transform was proposed,thus getting synchrosqueezed S transform.The periodic impact feature of gearbox planetary gear and bearing failure was identified by improving time-frequency resolution.At last,combining S transform with time series decomposition algorithm,time-frequency correlation of the multi-correlation was discussed,and is used to analyze the correlation between noise sources.The main contents of this paper are as follows:In the first part,the purpose and significance of the research were explained firstly.Then the gearbox signal characteristics and common characteristics of gear fault and bearing failure were summarized in the basic theory part.Formulas for time-frequency analysis such as S transform,discrete S transform and synchrosqueezed transform were deduced.In the second part,from the point of view of noise reduction,the fault of gearbox planetary gear and bearing were identified.The theory of singular value decomposition(SVD)was introduced firstly.Then a noise reduction method of the S transform-singular value decomposition-singular value ratio spectrum(SVR)was proposed.Firstly,the time-frequency matrix obtained by the S-transform of the signal was used as the SVD construction matrix.Secondly,the threshold,which is the last peak position of the front dense peak of the singular value ratio spectrum,was chosen to denoise the signal.Thirdly,the denoised S transform matrix was reconstructed.Lastly,the inverse S transform was performed to obtain the periodic time domain impact characteristics,thus getting the frequency domain impact feature.Verification of the effectiveness of the proposed method was carried out using simulation and experimental data.The results show that the method can accurately,intuitively and effectively identify the periodic impact features.In the third part,from the point of view of improving time-frequency resolution,the fault of planetary gear and bearing was identified.By combining S transform and synchrosqueezed transform,synchrosqueezed S transform(SSST)was obtained and the formula was deduced.Synchrosqueezed S transform can improve the time-frequency resolution of S transform while keeping S transform's sensitive to impact features.So SSST can identify impact features.Verification of the effectiveness was carried out using simulation and experimental data.The results show that the method can accurately and effectively identify the periodic impact features.In the fourth part,the basic theory of multi-correlation analysis was presented firstly.A time series decomposition algorithm was derived from synchrosqueezed S transform,and was used in correlation analysis.And time-frequency correlation was proposed.By comparing and analyzing the time-frequency correlation with the traditional ones through analysis of simulation and experimental data of two signals correlation and three signals correlation,the results show that time-frequency correlation can not only reflect the time-varying and frequency-varying characteristics of the correlation,but also has advantages in the correlation analysis of non-stationary signals.In conclusion,by combining S-transform with other methods,the complex signal of gearbox was studied in this paper.The impact features of the signals were identified and the time-frequency correlation was attained.Besides a number of valuable conclusions haven been got.