STUDY ON THE METHOD OF EMD-BASED VIBRATION SIGNAL TIME-FREQUENCY ANALYSIS

A new method for identifying the instantaneous frequency with empirical mode decomposition (EMD) based Hilbert transformation (HT) was proposed. Through EMD,the time series data are seperated into intrinsic mode functions (IMFs), and then each IMF is decomposed to an envelope signal and a frequency modulated signal. The instantaneous frequency can be derived from the frequency modulated signal using arccosine function. A simulated nonlinear signal was processed using the method and the results show the validity of the technology. A deep crack rotor vibration signal was dealt with as an example and the results show that the method is helpful to detect the phase-modulation caused by torsional vibration of the rotor.