Fault Diagnosis of Wind Turbine Bearing Using Variational Nonlinear Chirp Mode Decomposition and Order Analysis

In this paper, a method for bearing fault diagnosis without using a tachometer under variable speed conditions by combining the variational nonlinear chirp mode decomposition (VNCMD) with angular resampling technique is proposed. First of all, the original bearing vibration signal can be decomposed and the rotation mode can be reconstructed by using the VNCMD. Then the rotation phase is calculated from the reconstructed rotation mode. In the next step, the original bearing vibration signal is resampled on the basis of the extracted rotation angle information. Finally, the bearing fault indicator can be displayed in the envelope order spectrum and then the bearing fault can be diagnosed. This method addresses the problem that the frequency components are aliasing in the envelope spectrum under variable speed conditions. The reliability and effectiveness of the method proposed in this study are proved by the experiments.