APPLICATION OF A WAVELET-BASED FREQUENCY RESPONSE FUNCTION TO THE ANALYSIS OF A BILINEAR SYSTEM
John R. Hartin · University of North Texas Digital Library (University of North Texas) · 2000
Fourier-based methods are the Qresent standard for calculation of frequency response functions and modal analysis, but standard Fourier methods are not well suited for the analysis of nonlinear or non-s&ionary behavior.A wavelet-based technique that calculates complex, time-va~ing frequency response functions (~RFs) for input/output relationships has been developed.'The method uses a simple tone-like Grossman-Morlet wa~let that has unique resolution characteristike optimized to;,zoom-in on different portions of the time-f~equency spectrum.The method is used to determine time varying frequency responses and mode shapes for a ten degree-of-freedom bilinear structure.Some characteristics of nonlinear no,rrnal mode behavior like bifurcated resonant peaks and lo@alized modes are illustrated.The method holds promise for analysis of nonlinear input-output systems with time-varying responses, and could be a powerful tool for cdndition monitoring or damage detection.This method $presents a unique, fundamental advance in time frequency measurement techniques since a time varying 'transfer function is computed rather than direct respbnse decomposition.