Continuous wavelet transform and entropy criterion in modal analysis

In this work, wavelet method is used for the identification of the modal parameters of linear structures. The analyzed signal is supposed to be the free response collected from an accelerometer placed at one selected position along the structure. In order to reach optimal frequential and temporal resolutions for all the modes of vibration, a parameter N is introduced into the Morlet wavelet. The value of N which minimizes the entropy of the wavelet coefficients for each mode is the optimal value of analysis. That allows an adequate distribution of the resolutions that gives a more precise estimate of the modal parameters of the structure. Numerical examples show the effect of the variation of the N parameter with the mode of vibration on the modes coupling and on the border effect.