Comparison of two dissimilar modal Identification Techniques.

Abstract

This paper discusses work performed under a collaborative research agreement between NASA and DLR in the area of Dynamics and Control of Large Space Systems. The objective is to develop improved techniques for system identification of future large spacecraft. Recent laboratory results using a refined Phase Resonance Method (PRM) and the Eigensystem Realization Algorithm (ERA) on the same test structure are reported. These methods are dissimilar modal identification techniques developed at DLR and NASA, respectively. In this application, the natural frequencies and mode shapes determined using the PRM and ERA techniques are mostlly identical within engineering accuracy. Although ERA identified 30 modes in the frequency range from 0 to 100 Hz compared with 26 modes for PRM, the additional results are weakly-observed torsional modes of the individual beams which were not sought.