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 cyclo-stationarity and bilinearity. For the first time, we present a comparison between cyclo-stationarity 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. (C) 2001 Academic Press.