Compound-Fault Diagnosis of rolling bearing based on Order Wavelet Packet and Rough Sets Theory

The diagnosis of compound-fault is always a difficult point, and there is not an effective method in equipment diagnosis field, and then a new method of compound-fault diagnosis was presented in the paper. The vibration signals at start-up in the gearbox are non-stationary signals, in order to solve the compound-fault diagnosis of rolling bearing, the order tracking wavelet packet and rough sets theory are combined and introduced into the fault diagnosis field. Firstly, the non-stationary vibration signals at start-up were resampled using computer order tracking arithmetic and equal angle distributed vibration signals were obtained, and then the signals were decomposed and recomposed with the wavelet packet. The energy distribution of every frequency band was calculated according to normalization process. A new feature vector can be obtained, then clear and concise decision rules can be obtained by rough sets theory. Finally, the result of compound-fault example proves that the proposed method has high validity and more amplitude appliance foreground.