Cyclic bispectrum patterns of defective rolling element bearing vibration response

Abstract

The vibration signal from a faulty rolling element bearing is not strictly phase locked to the rotational speed of the shaft, due to the variable slip between the bearing elements. For this reason, the classical diagnostic methods, which are based on Fourier analysis, cannot detect clearly the modulation phenomena and the type of the defect, because the relevant information contained in the second order statistic measures is diminished. The main purpose of this paper is the combination of cyclostationary and higher order statistic analysis methods, which can lead to better results, concerning the identification of the status of the bearing. The paper demonstrates that the cyclic bispectral analysis can lead to a discrete spectral structure, enabling the clear detection the type of the bearing fault and the corresponding modulation mechanism, thus significantly overcoming the corresponding problem of other existing methods.