Fault Feature Extraction of Elliptically Shaped Bearing Raceway 2019-01-1564
The elliptically shaped bearing (ESB) with a rigid, elliptical inner race and a flexible, thin-walled outer race is the most easily damaged core component of harmonic drive. The ESB rotates under cycle load of alternating stress due to its special elliptic structure. Hence, the impact noise produced by alternating between long axis and short axis is apt to conceal the fault features of ESB such as fatigue spalling and pitting. In order to diagnose the fault on raceway surface of ESB, a new method of CMWT-FH based on Continuous Morlet Wavelet Transform (CMWT) and FFT-based Hilbert (FH) spectrum analysis is proposed to extract the fault feature. First, the formulas of fault feature frequency is deduced based on the geometry and kinematic characteristic of ESB; then the CMWT method is employed to decompose the fault signal of ESB; finally, the FH spectrum analysis is performed to extract the fault feature frequency of ESB from the decomposition signal with the largest kurtosis value in the first several layers. Compared with the conventional FH method, the proposed CMWT-FH method can identify fault feature frequency and its sideband of ESB more accurately and determine whether the fault location is on the outer or inner ring.
Yingying Guo, Xuezhi Zhao
South China University of Technology
Noise and Vibration Conference & Exhibition