Comparison of envelope demodulation methods in the analysis of rolling bearing damage

In rotating machinery, especially in rolling bearing diagnostics, early and effective fault diagnosis is essential to ensure the reliability of rolling bearings. The commonly used vibration analysis gathers large amounts of information about the dynamics and the general condition of the bearings by recording vibrations generated by a rolling bearing. Within the vibration analysis, the location of the damage can be determined by using envelope demodulation. This is done by identifying the damage frequency within a damaged bearing. Peak-, Root-Mean-Square (RMS)-, and Hilbert-envelopes are the conventional demodulation methods in this field, but each of these methods is different and thus more or less suitable for particular applications. This paper presents a comparative study of these three methods. The selected envelopes are compared and evaluated through experiments, the evaluation of measurement data and the establishment of quality characteristics regarding efficiency and quality. In the process, a decision tool is created to help in the selection of a suitable envelope demodulation technique. A formula for calculating an optimal window size of the Peak-envelope is established, as well as a recommendation for selecting a window size of the RMS-envelope.