How to obtain modal parameters from FRF

Hello,

Recently i have received the data of the Frequency Response Function in a frequency invertal of a given system. The system consists of a free-free beam with 21 points of measurement. I would like to know how, from this data, you can obtain in MATLAB all the modal parameters such as natural frequencies, damping coefficents and modes (assuming viscous damping).

All the examples i have seen, suppose you know how the system is modeled but in this case all i know is the FRF of all the points of measurement.

Answer 1

[Nick Choi]

You could use the frequency response data to estimate the model for the system. With that estimate, you could determine the parameters.

The following documentation pages contain examples of how to estimate models based upon frequency response data as well as how to determine modal parameters:

https://www.mathworks.com/help/ident/gs/estimate-models-using-frequency-domain-data.html

https://www.mathworks.com/help/signal/ug/modal-analysis-of-identified-models.html

This documentation page provides additional information on how to estimate models based upon frequency response data:

https://www.mathworks.com/help/ident/ug/frequency-domain-identification-estimating-models-using-frequency-domain-data.html

Answer 2

[Ahmed Sboui]

SVP si vous êtes arrivé à résoudre votre problématique , montre moi comment vous l'avez résolu et merci bien à l'avance , je suis ce même cas.