Normalized Complex Teager Energy Operator Demodulation Methodand Its Application to Rotor Rub-impact Fault Diagnosis

Abstract

Normalized Hilbert transform(NHT) demodulation method introduces an empirical AM-FM decomposition to a monocomponent signal, achieving a separation of the envelope signal(i.e., instantaneous amplitude) and the FM signal, then instantaneous frequency can be directly extracted through Hilbert transform to the FM signal. Compared with direct HT method, NHT method could gain a better demodulation performance. However, studies show that the FM signal results from empirical AM-FM decomposition may contain riding waves, which are prone to negative frequency. Moreover, since Hilbert transform is still used, oscillations will inevitably occur near endpoints of the obtained instantaneous frequency by NHT method. Aiming at the drawbacks of NHT method, an improved empirical AM-FM decomposition for eliminating riding waves and an instantaneous frequency estimate based on complex Teager energy operator(CTEO) for the FM signal are presented, respectively. Furthermore, a new signal demodulation method named normalized complex Teager energy operator(NCTEO) demodulation is proposed, in which the improved empirical AM-FM decomposition is applied to a monocomponent signal to extract instantaneous amplitude, and NCTEO method is applied to the resulting FM signal to extract instantaneous frequency. Simulated signals experiments and earlyrub-impact fault signals analysis of rotor system verify the excellence and effectiveness of NCTEO method.