Demodulation of vibration signals generated by defects in rolling element bearings using complex shifted Morlet wavelets

Vibration signals resulting from rolling element bearing defects, present a rich content of physical information, the appropriate analysis of which can lead to the clear identification of the nature of the fault. The envelope detection or demodulation methods have been established as the dominant analysis methods for this purpose, since they can separate the useful part of the signal from its redundant contents. This paper proposes an effective demodulation method, based on the use of a complex shifted Morlet wavelet family. The method is designed in a way that can fully exploit the underlying physical concepts of the modulation mechanism, present in the vibration response of faulty bearings, using a time-frequency representation of the signal. A key element of the proposed method is the systematic introduction of selection criteria for the automated choice of the critical parameters that characterise the Morlet wavelet family used. Experimental results and industrial measurements for two different types of bearing faults confirm the validity of the overall approach. (C) 2002 Published by Elsevier Science Ltd.