Multi-scale enveloping order spectrogram for rotating machine health diagnosis

• A hybrid technique is proposed to enhance health diagnosis of rotating machines.
• Complex wavelet transform is used for envelope extraction.
• Computed order tracking is applied for eliminating speed dependence.
• Experimental results verified the effectiveness of the hybrid technique.

This paper presents a hybrid technique to enhance health diagnosis of rotating machines under varying speed conditions. This is achieved through the integration of complex wavelet transform-based envelope extraction of speed-varying vibration signals with computed order tracking for eliminating speed dependence in the sampled data. By performing a post-spectral analysis of the resampled signal, a multi-scale enveloping order spectrogram is realized that has shown to enable enhanced defect feature extraction. Numerical simulation and experimental studies have demonstrated the effectiveness of the hybrid technique in identifying bearing structural defects under varying operating conditions.