Second generation wavelet packet construction and aircraft engine weak damage identification

To identify weak damage of aircraft engine rolling bearing, a new method to construct second generation wavelet packet was presented. In this method, the decomposition and reconstruction procedures of second generation packet were designed, and the second generation packet operators which lock on to the dominant signal structure were calculated. The vibration signal of rolling bearing was decomposed with second generation wavelet packet, and the signal at each frequency band was reconstructed. The reconstruction signals were demodulated with Hilbert transform, and envelope spectrum at each band was obtained. The dB values of fault feature frequency components corresponding envelope spectrum at each frequency band were calculated, and the maximal dB value of fault feature frequency components was extracted to identify damage of rolling bearing. The proposed damage identification method was used to analyze simulation signal and experimental signal from a rolling bearing with weak outer race damage, and results confirm the advantages of second generation wavelet packet for rolling bearing damage identification.