Using appropriate IMFs for envelope analysis in multiple fault diagnosis of ball bearings

The traditional envelope analysis is an effective method for the fault detection of rolling bearings. However, all the resonant frequency bands must be examined during the bearing-fault detection process. To ameliorate the above deficiency, this paper presents a new concept based on the empirical mode decomposition (EMD) to choose an appropriate intrinsic mode function (IMF) for the subsequent envelope analysis. By virtue of the band-pass filtering nature of EMD, the resonant frequency bands of structure to be measured are captured in the IMFs. As impulses arising from rolling elements striking bearing faults modulate with structure resonance, appropriate IMFs are potentially able to characterize fault signatures, instead of always using IMF 1. In the study, dual- and triple-fault bearings are used to justify the proposed method and comparisons with the traditional envelope analysis are made.