Accurate Instantaneous Frequency Estimation with Iterated Hilbert Transform and Its Application

Iterated Hilbert transform (IHT) is a new method for multicomponent demodulation. The principle of IHT is introduced, and some of its properties are researched. Although the amplitudes of the demodulated components obtained by IHT are accurate, there are limitations in the direct estimation of instantaneous frequencies via the extracted phases, so a smoothed instantaneous frequency estimation (SIFE) method based on difference operator and zero-phase digital low-pass filtering is proposed. The simulation results show that the proposed approach has higher performance than the adaptive segmentation algorithm and Hilbert-Huang transform. Finally, IHT and SIFE are applied to fault diagnosis of a rolling bearing, and the results show that the multicomponent fault vibration signal can be demodulated correctly and the weak feature of fault signals can be extracted efficiently with IHT and SIFE. Key-Words: Multicomponent demodulation, Hilbert transform, Amplitude envelopes, Filtering, Instantaneous frequency estimation, Fault diagnosis.