Output-Only Analyses in Environmental Testing

Environmental tests are widely used to qualify structures for space missions, because the benchmark test facilities allow the replication of the loading conditions acting on a system during the different phases of the mission. In this paper, an Output-Only-based tech-nique is proposed to estimate the full modal parameters, in the frame of the environmental test-ing, to increase the accuracy of the dynamic identification and to reduce the overall time and cost associated to the qualification process. The Output-Only Modal Analysis approach, de-noted as Hilbert Transform Method by the authors, will be applied for the estimate of the "bi-ased" Frequency Response Functions, FRFs, whereas the evaluation of the modal masses asso-ciated to each mode will be carried out by the application of various mass perturbation methods available in literature. The robustness of these approaches will be assessed through environ-mental tests carried out on spacecraft structures, such as a robotic arm intended for space appli-cations and a tank prototype of the Vega launcher. The accuracy of the proposed method will be finally evaluated by comparing the FRF estimates, obtained with the Output-Only approach, with the ones gained using the standard input/output technique. Copyright © (2011) by International Operational Modal Analysis Conference (IOMAC) All rights reserved.