Time-frequency analysis of a non-stationary wind pressure with HHT method

The analysis method of non-stationary signals is a major issue in signal analysis field.Taking signals of non-stationary wind pressure and lift coefficient obtained from wind tunnel tests as research objects,time frequency analysis of signals was presented with HHT method.Based on HHT method,the meaningful instantaneous frequency,and the exact expression of frequency changing with time were obtained,the signal was finally expressed as the energy distribution in the time frequency plane,i.e.,a Hilbert spectrum.This method could be used to analyze a large amount of nonlinear and non-stationary signals whose frequencies changed with time,and to decompose complex signals into a number of intrinsic mode functions with higher to lower frequencies.The analysis results did not show significant characteristics of spectral distribution,however,they were different from the previous intrinsic mode functions extracted with HHT.If intrinsic mode function extracted from a non-stationary signal in the test was a residual signal with lower frequencies and the other parts with higher frequencies were neglected,the residual signal curves of the time histories of the wind pressure and the lift coefficient could be regressed a linear function and a sine function,respectively.It was shown that the main components of this non-stationary signal are mostly stationary ones,and their time histories can be analyzed with the method of stationary signal analysis.