Try using the residue function. If your transfer function is 2nd order (s^2 is the highest power term in the denominator of the laplace domain transfer function), its simple to determine the damping freq and damping factor. The denominator in a standard 2nd order system is of the form

s^2+2*zeta*wn*s+wn^2, please check it in a standard control theory book.

Premal

gt0398b <g...@cad.gatech.edu> wrote:

I am using Matlab 7.0 plus most of the toolboxes. I have some experiemtally obtained transfer funtions of a previous experiement. This experiment imparts a random vibration on one location on a structure and senses acceleration at another location. I would like to extract the modal residues, damping ratios and natural frequencies from these experimental transfer funtions. I have looked through the System Identification toolbox but nothing seems to perform this function. I would appreciate any help. Patrick Roberts Dept. of Aerospace Engineering Georgia Tech

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I am using Matlab 7.0 plus most of the toolboxes. I have some experiemtally obtained transfer funtions of a previous experiement. This experiment imparts a random vibration on one location on a structure and senses acceleration at another location. I would like to extract the modal residues, damping ratios and natural frequencies from these experimental transfer funtions. I have looked through the System Identification toolbox but nothing seems to perform this function. I would appreciate any help. Patrick Roberts Dept. of Aerospace Engineering Georgia Tech