CYCLOSTATIONARY APPROACH AND BILINEAR APPROACH: COMPARISON, APPLICATIONS TO EARLY DIAGNOSIS FOR HELICOPTER GEARBOX AND CLASSIFICATION METHOD BASED ON HOCS

In this paper, we would like to determine links or common properties between cyclostationarity and bilinearity. For the first time, we present a comparison between cyclostationarity and bilinearity. By using calculations, simulations with synthetic signals and finally applications to industrial signals, we underline that cyclostationary and bilinear tools make it possible to determine both non-linear and non-stationary links. The second part of our study deals with applications of these approaches for the diagnosis of faults on industrial signals, recorded on a helicopter gear box. We especially underline the importance of torque in the quality of diagnosis. Finally, we introduce a classification method. It allows us to determine if a link between two frequencies is cyclostationary rather than bilinear. This method is based on the use of higher-order cyclic statistics and more especially on the cyclic bispectrum.