Robust modal identification/estimation of the mini-mast testbed

The Mini-Mast is a 20-m-long, three-dimensional, deployable/retractable truss structure designed to imitate future trusses in space. This structure has undergone various static and dynamic experiments to identify its modal properties so that control laws can be developed and tested. This paper presents results from a robust (with respect to measurement noise sensitivity), time-domain, modal identification technique for identifying the modal properties of the Mini-Mast structure even in the presence of noisy measurements. Three testing/analysis procedures are considered: 1) sinusoidal excitation near the resonant frequencies of the Mini-Mast, 2) frequency response function averaging of several modal tests, and 3) random input excitation with a free response period. The results indicate that the robust technique of the paper is more accurate using the actual experimental data than are existing techniques.