This example demonstrate the impact testing module as well as the two polyreference methods for EMA in ARTeMIS Modal. The structure is a symmetric steel plate with dimensions 300 x 300 x 8 mm. Two accelerometers has been mounted as references and the impacts were made in 16 positions in a 4 x 4 grid.
The test and analysis can be seen in the three YouTube videos below:
Below the final results are depicted.
Complex Mode Indicator Function - Peak Picking
When having multiple references there will be multiple singular value lines in the Complex Mode Indicator Function. In the case of a symmetric structure there will be multiple modes having more or less the same natural frequency. In this case the different modes are picked at the different singular values. This is necessary for three frequency location in the present example.
Rational Fraction Polynomial in Z domain (RFP-Z)
This method estimates the global modes by creating a stabilization diagram from which stable (physical) modes are picked out automatically. The primary user inputs are to specify the maximum model order, the frequency range of interest, and possibly modify the modal indicators to help the automatic search for global modes.