Bearing condition monitoring approaches - envelope and cepstrum analyses

Abstract

Envelope and cepstrum analyses are useful tools to identify the fault bearing characteristic frequencies (BCFs) and distinguish them from other frequencies. However, the traditional envelope analysis has disadvantages such as the choice of central frequency of filter needs prior experience. To overcome the traditional envelope shortage, an optimal wavelet filter is used as a band-pass filter whose parameters are optimised based on the maximum kurtosis value. To further reduce the residual in-band noise and highlight the periodic impulsive feature, an envelope enhancement is applied to the filtered signal. The article aims to compare these two condition monitoring tools in a pragmatic way and demonstrate their properties by using a practical example of a rolling bearing fault. The results prove that cepstrum analysis provides a clear indication of fault for machine parts such as vehicle gearbox, in addition to evaluating the efficiency of proposed band-pass filter in the envelope analysis.