Abstract: Aiming at the problem that the modulation sidebands of vibration signals of a gearbox with variable rotating speed are difficult to identify, an order analysis method based on multi-scale chirplet and sparse signal decomposition is proposed. In the proposed method, a vibration signal of gearbox is decomposed to obtain the meshing component and the modulation sidebands by using the sparse signal decomposition based on multi-scale chirplet and simultaneously, their instantaneous frequencies are obtained. Then the rotating speed signal can be obtained by software method without the tachometer. Based on the obtained rotating speed, the uniform angle resampling on the sum of the meshing component and the modulation sideband components are carried out, so the order spectrum of the resampled signals can be obtained and used in the fault diagnosis of the gearbox. Simulation and practical application examples show that the proposed method has a strong noise immunity and is better than the traditional order method in identifying the modulation sidebands.

Key words: Fault diagnosis, Gear, Order analysis, Sparse signal decomposition