Gear crack detection by adaptive amplitude and phase demodulation

A new method for gear crack detection is presented. It consists of the coupling of adaptive demodulation with an abrupt change detector. The adaptive algorithm is intended to account for the slow variations of the signal. Two methods for this adaptive demodulation are proposed: a RLS approach based on a linear version of the signal model and a LMS approach which directly estimates the physical parameters (amplitude and phase) for each harmonic considered. Their respective advantages and disadvantages are discussed and the superiority over the Hilbert transform approach is shown. The crack detection is formulated as an abrupt change detection problem solved by the sequential monitoring of the prediction error. Its effectiveness is demonstrated through the application of the demodulation detection algorithm to gearbox under reliability tests. (C) 1997 Academic Press Limited