A methodology for analyzing vibration data from planetary gear systems using complex Morlet wavelets

Planetary gear trains are complex flight critical components of helicopters and other aircraft. Failure modes on such components may lead to loss of life and/or aircraft. It is essential, therefore, that incipient failures or faults be detected and isolated as early as possible and corrective action be taken in order to avoid catastrophic events. Research thus far has focused on gear teeth faults and available methods could not detect a crack in the planetary gear plate under all operating conditions. A wavelet domain methodology is suggested for the analysis and feature extraction of the vibration data from the planetary gear system of military helicopters. Complex Morlet wavelets are employed and the time domain knowledge, preserved by the wavelet decomposition, is used to extract useful features that distinguish between faulted and healthy gear plates from experimental data made available from both on-aircraft and test cell experiments. A statistical method based on the z-test is also suggested to evaluate the relative performance of these features.