Abstract
Abstract
In some complex working conditions, such as variable speeds and variable loadings, events like bearing skidding and/or contact angle changing may happen during the operations. In such cases, order tracking based on the shaft speed, i.e. the first order tracking (FOT), can no longer completely eliminate the smearing effect on spectrum, and thus affects the bearing damage detection precision and accuracy. The existing second order tracking is unable to resolve these issues either in some cases. To resolve these problems, a new approach called time frequency analysis based second order tracking is developed in this paper. Based on the FOT, short-time Fourier transform and synchro-reassigning transform are used to obtain the actual fault characteristic order (FCO) information. Then the FCO is extracted by ridge searching approach to set new synchronous resampling clock. Finally, synchronous resampling and order tracking are combined to correct and enhance the bearing damage feature, resulting in more accurate damage feature extraction. The effectiveness of proposed method is verified by numerical simulations and practical examples as well. The results show that the proposed method can effectively correct the dispersion and deviation of the FCO induced by speed variations as well as operation condition variations, and thus significantly improve the damage feature extraction.