Compound fault diagnosis of rolling bearing under variable speed based on generalized demodulation transformation and symplectic geometric mode decomposition

In this paper, a superior compound fault diagnosis method of rolling bearing under a variable speed is proposed, which is based on the generalized demodulation transformation and symplectic geometric mode decomposition. First, generalized demodulation transformation is performed on a time-varying non-stationarity compound fault signal to smooth the fault components by calculating the characteristic frequency, phase function, and theoretical fault frequency point. Then, a new signal decomposition method is applied to extract component signals of different frequencies from the smoothed fault components, and the frequency of each extracted component signal is obtained. Finally, the frequencies of the obtained fault components are compared with theoretical fault frequencies to perform decoupling and diagnosis of compound fault. The simulation and experimental analysis results show that the proposed method can effectively decouple different fault components of compound fault without using the order tracking, providing a superior solution for the diagnosis of compound fault under a time-varying rotational speed.