OPTIMAL ENVELOPE DEMODULATION METHOD BASED ON ADAPTIVE COM-PLEX SHIFTED MORLET WAVELET IN BEARING DIAGNOSIS

LIANG Lin¹  XU Guanghua²

(1. School of Mechanical Engineering, Xi’an Jiaotong University, Xi’an 710049;
2. The State Key Laboratory for Manufacturing Sys-tems Engineering, Xi’an Jiaotong University, Xi’an 710049)

Abstract: Due to the demodulation performance of traditional envelope demodulation methods depend strongly on a number of parameters selected by experience of the user, so an adaptive wavelet-based envelope method derived from complex shifted Morlet wavelet is proposed to overcome this shortcoming. The complex shifted Morlet wavelet family is adopted to extract fault features based on the fact that the bearing defect can ex-cites vibration at specific impact component. Meanwhile, based on the optimal principle of maximal kurtosis of coefficient waveform, the shape parameters of Morlet wavelet, which include center frequency and envelope factor, can be adjusted adaptively to match with the impact component. Thereby, the optimization envelope can be constructed effectively. Experimental results and industrial measurement analysis show that the new approach, compared with the common complex shifted wavelet transform, could effectively extract the weak fault feature with the optimal matching of waveform, and is suitable to extract the incipient fault feature for rolling bearing.

Key words: Complex shifted Morlet wavelet Continuous wavelet transform Envelope demodulation Fault diagnosis

CLC No: TN911.7 

国家自然科学基金重点资助项目(50335030). Received 20051026, received in revised form 20060626