ERA Modal Identification Experiences with Mini-Mast.

Abstract

This paper summarizes work performed under a collaborative research effort between NASA and the German Aerospace Research Establishment (DLR). The objective is to develop improved understanding of the practical performance characteristics of system identification procedures for large space sructures. Results obtained using the ERA modal identification technique applied to frequency response functions from Mini-Mast are discussed. Mini-Mast is a 20-meter long generic space truss located at NASA Langley, and it serves as the first ground testbed for the CSI Guest Investigator program. Data for ERA are obtained by inverse Fourier transformation of frequency response functions generated using modern, multiple-input random excitation techniques. Modal identification proved to be difficult for this large, deployable truss structure. Techniques for optimizing accuracy and for assessing identification uncertainty and sensitivity are shown.