Cyclostationary-based Multiband Envelope Spectra Extraction for bearing diagnostics: The Combined Improved Envelope Spectrum

摘要

Bearing diagnostics is a field of intensive research, focusing nowadays mainly in complicated machinery (e.g. planetary gearboxes, multi-stage gearboxes, etc.) operating under varying conditions (e.g. varying speed and load), as they still provide challenges in terms of accuracy and time of detection/diagnosis. One of the most common methods for bearings diagnostics is Envelope Analysis, where a filter is usually applied around an excited frequency band and the signal is enveloped, obtaining the Squared Envelope Spectrum. However, as the bearing damage may excite several frequency bands simultaneously, band-pass filtering around only one frequency band may not be sufficient for the detection of the bearing fault under the presence of noise. Recently, the iESFOgram (Improved Envelope Spectrum via Feature Optimisation-gram) has been proposed, based on either the Cyclic Spectral Correlation or the Cyclic Spectral Coherence, in order to select the optimal frequency band and extract the corresponding Improved Envelope Spectrum. In this paper the method is extended towards the extraction of the Combined Improved Envelope Spectrum (CIES), performing a multi-band integration of the bivariable map around multiple resonant frequencies that are carriers of the bearing damage signature. The proposed method is applied, tested and evaluated on experimental data and the results are compared with state-of-the-art band-selection tools.