OPERATIONAL MODAL ANALYSIS IN ABSENCE OF A RANDOM DISTRIBUTED LOAD

In this paper the performance of several modal parameter estimation techniques is compared by considering a simple me-chanical structure as test bed. Specifically, among Input/Output (I/O) techniques, a frequency domain poly-reference method is considered. Among Operational Modal Analysis (OMA), Fre-quency Domain Decomposition and poly-reference least square complex frequency-domain techniques are used. I/O technique and OMA are performed using the measurements due to a ran-dom shaker excitation. In the first case the responses and the input force are used to calculate the FRFs. On the contrary, OMA is performed by using only the set of measured responses, by supposing unknown the input force. Note that the OMA hy-pothesis of a random distributed force is not observed. In order to characterise the performance of the examined methods, the re-sults obtained by the OMA are compared to the result of the I/O technique