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Shock and Vibration
Volume 9, Issue 6, Pages 293-306

Wavelet Based Demodulation of Vibration Signals Generated by Defects in Rolling Element Bearings

C.T. Yiakopoulos and I.A. Antoniadis

National Technical University of Athens, Department of Mechanical Engineering, Machine Design and Control Systems Section, P.O. Box 64078, Athens 15710, Greece

Received 11 September 2000; Revised 10 January 2002

Copyright © 2002 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Vibration signals resulting from roller 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. The paper proposes a new effective demodulation method, based on the wavelet transform. The method fully exploits the underlying physical concepts of the modulation mechanism, present in the vibration response of faulty bearings, using the excellent time-frequency localization properties of the wavelet analysis. The choice of the specific wavelet family is marginal to their overall effect, while the necessary number of wavelet levels is quite limited. Experimental results and industrial measurements for three different types of bearing faults confirm the validity of the overall approach.