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Proceedings Paper

Modal characterization of the ASCIE segmented optics test bed: new algorithms and experimental results
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Paper Abstract

New frequency response measurement procedures, on-line modal tuning techniques, and off- line modal identification algorithms are developed and applied to the modal identification of the Advanced Structures/Controls Integrated Experiment (ASCIE), a generic segmented optics telescope test-bed representative of future complex space structures. The frequency response measurement procedure simultaneously uses all the actuators to excite the structure and all the sensors to measure the structural response so that all the transfer functions are measured simultaneously. Structural responses to sinusoidal excitations are measured and analyzed to calculate spectral responses. The spectral responses in turn are analyzed as the spectral data become available and, which is new, the results are used to maintain high quality measurements. Data acquisition, processing, and checking procedures are fully automated. As the acquisition of the frequency response progresses, an on-line algorithm keeps track of the actuator force distribution that maximizes the structural response to automatically tune to a structural mode when approaching a resonant frequency. This tuning is insensitive to delays, ill-conditioning, and nonproportional damping. Experimental results show that it is useful for modal surveys even in high modal density regions. For thorough modeling, a constructive procedure is proposed to identify the dynamics of a complex system from its frequency response with the minimization of a least-squares cost function as a desirable objective. This procedure relies on off-line modal separation algorithms to extract modal information and on least-squares parameter subset optimization to combine the modal results and globally fit the modal parameters to the measured data. The modal separation algorithms resolved modal density of 5 modes/Hz in the ASCIE experiment. They promise to be useful in many challenging applications.

Paper Details

Date Published: 10 July 1992
PDF: 16 pages
Proc. SPIE 1696, Controls for Optical Systems, (10 July 1992); doi: 10.1117/12.138149
Show Author Affiliations
Alain C. Carrier, Lockheed Palo Alto Research Lab. (United States)
Jean-Noel Aubrun, Lockheed Palo Alto Research Lab. (United States)

Published in SPIE Proceedings Vol. 1696:
Controls for Optical Systems
John A. Breakwell, Editor(s)

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