Bearing failure impulse enhancement method using multiple resonance band centre positioning and envelope integration

Due to the complex structure of electromechanical systems, impulse components with a transient duration will excite multi-resonance phenomena and generate diverse peak-like bands in the spectra of vibration signals. Resonance bands excited by bearing failure-induced impulses that characterise failure area and form, are confused with frequency components caused by impulsive interference and background noise. Given the imperceptibility of the failure features of on-machine bearings, a better identification strategy is to extract the information of multiple predominate resonance bands excited by failure, referred to as effective resonance frequency bands (ERFBs), and to then integrate them, instead of locating only the optimal resonance frequency band (ORFB). In this paper, a multiple resonance band centre positioning and envelope integration method is proposed to enhance the bearing failure features. To this end, a robust indicator, ratio of cyclic content (RCC), is utilised to construct an Improved-Protrugram to position the centres of ERFBs correctly. Then, a dichotomy is introduced to establish an iterative search algorithm for improving position efficiency. Further, the positioned sub-band components are filtered and demodulated to obtain the envelopes of failure-induced multiple resonances. Finally, a variable weighting envelop integration strategy is proposed to eliminate interference that does not coexist between different sub-band components. The effectiveness of the proposed method is verified using both simulated and experimental bearing failure signals. The results indicate that the proposed method is superior to ORFB location methods for on-machine bearing failure identification.