Wavelet Based Demodulation of Vibration Signals Generated by Defects in Rolling Element Bearings

Abstract

Vibration signals resulting from roller bearing defects, present a rich content of physical information, the appropriate analysis of which can lead to the clear identification of the nature of the fault. The envelope detection or demodulation methods have been established as the dominant analysis methods for this purpose, since they can separate the useful part of the signal from its redundant contents. The paper proposes a new effective demodulation method, based on the wavelet transform. The method fully exploits the underlying physical concepts of the modulation mechanism, present in the vibration response of faulty bearings, using the excellent time-frequency localization properties of the wavelet analysis. The choice of the specific wavelet family is marginal to their overall effect, while the necessary number of wavelet levels is quite limited. Experimental results and industrial measurements for three different types of bearing faults confirm the validity of the overall approach.

Robust performance degradation assessment methods for enhanced rolling element bearing prognostics

“…Eq. (6) shows that the wavelet transform can also be considered as a special filtering operation. The frequency segmentation is obtained by dilating the analysis wavelet.…”

“…As for the vibration signal of rolling element bearing, modulation [6] and noise are two major barriers in causing difficulties in incipient defect detection. To overcome the modulation issue, a large variety of signal demodulation methods have been developed over the years [8,9].…”

Multiscale envelope manifold for enhanced fault diagnosis of rotating machines

“…13(b). Then the two resonance bands are determined in the ranges of [7,12] and [3.8, 6.1], as illustrated in Fig. 13(d).…”

“…This is because the fault-related periodic impulse is a modulator to the high natural frequencies of the machine [5]. To demodulate the impact impulses, some wavelet-based demodulation methods have been studied [6][7][8][9][10] and confirmed to outperform the conventional filter-based or FFT-based Hilbert transform [7,9]. However, the extracted envelope by those methods is either at a single scale or among a scale band, which still confronts the contamination of in-band noise.…”

Application of the EMD method in the vibration analysis of ball bearings

“…As the bearing is running, the impulse is produced periodically. Hence, the impacts produced by the defect can be modeled as an infinite series of impulses of equal amplitude, with the period between the impulses being T d [10,11]: Theses impulses excite the natural frequencies of ball bearing, resulting in an increase in the vibration energy at these high frequencies and the total resonance vibration can be described by an equation in the form vðtÞ ¼ dðtÞ hðtÞ,…”