Gear Tacho-less Order Tracking Method Based on SWT and IEWT
Aiming at the problem that the low speed gear fault signal of multistage gear transmission is susceptible to background noise interference under variable rotational speed conditions,which makes it difficult to extract weak fault features,a gear tacho-less order tracking method based on synchrosqueezing wavelet transform(SWT)and improved empirical wavelet transform(IEWT)is proposed.Firstly,in order to improve the accuracy of order tracking instantaneous frequency estimation without a tachometer,a continuous wavelet transform-elliptic time varying filter is designed to filter and denoise the gear vibration signal,and then a peak search is performed based on the filtered single component SWT time frequency distribution to achieve high-precision instantaneous frequency estimation;Then,according to the IFE curve,the time-varying fault signal is resampled at equal angles to obtain the angular domain stationary signal.An improved empirical wavelet transform method for adaptive decomposition of stationary signals in diagonal domain is proposed to solve the problem of unreasonable spectral segmentation in empirical wavelet transform.Finally,appropriate components are selected for autocorrelation denoising,and fault features are identified through order demodulation analysis.Simulation and analysis of measured partial tooth breakage data show that the method can accurately extract low-frequency weak fault features of variable speed gearbox.
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