MIMO Modal Parameters Identification in Frequency Domain

Modal Parameters identification in frequency domain using LSCF and LSFD algorithm for MIMO systems using fast implementation

This tool allows to identify modal parameters, eigenfrequency, modal damping factor and modal residues using complex Frequency Response Function (FRF) of a MIMO system. The least-squares problem is solved using fast implementation of the normal equations based on fft to improve the efficiency of the algorithm.

The algorithm is based on

- the Linear Square Complex Frequency Estimator (LSCF) using discrete-time z-model to estimate eigenfrequency and modal damping.

- the Least-Squares Frequency-Domain estimator (LSFD) to estimate modal residues.

The choice of the identification order and the selection of the physical poles are assisted by a stabilization chart using frequency and damping convergence criteria. The stabilization chart can then be automatically interpreted.

The folder contains:

- A file example (file_example.m) based on a numerical 4 dofs system (omg.mat, FRF_tot.mat).

- the function time2frf.m allows to load time data (time, input, output) in .txt format and returns complex FRF and natural frequency vector.

- the function select_frf.m allows to select a part of the FRF in the specified frequency range.

- the function lscf.m estimates eigenfrequency and modal damping factor using a stabilization chart in a specified order range and computes identified FRF using discrete z-model.

- the function plotstabchart.m plot the stabilization chart

- the function select_stabchart.m allows to select physical stable poles in the stabilization chart.

- the function lsfd.m estimates complex residues and identified FRF using s-model.