The fault diagnosis method of rolling bearing based on wavelet packet transform and zooming envelope analysis

The fault of rolling bearing is one of familiar faults in rotaries. In accordance with the defects of traditional envelope analysis to specify the resonant frequency band manually, a new fault diagnosis method based on wavelet packet transform and zooming envelope analysis is proposed. Firstly, the modulated frequency of resonant frequency band is extracted for rolling bearing, and the original signal is reconstructed and the other interfering signals are filtered based on wavelet packet transform. Secondly, the recomposed signal is demodulated by Hilbert transform, the high-frequency natural vibration is removed and the envelope signal can be obtained. Thirdly, in order to improve frequency precision of the envelope signal, the FFT-FS spectrum zooming method is proposed also. Finally, the fault vibration of a type 6350 rolling bearing installed on DBE-56-N4 electric machine is measured in the laboratory to verify the theoretical analysis presented above.