The work that is reported herein deals with system identification methods for large
flexible structures. Proposed space missions for the future include the deployment of
large flexible structures, e.g., NASA's proposed space station. These structures must be
controlled to maneuver the structure to desired locations and to suppress unwanted vibration. Before controlling any structure, it is necessary to have an accurate model
which may include accurate estimates of the structure's natural frequencies and mode
shapes. System identification is an important process that precludes system control.
Precision structures such as those proposed for the Space Based Laser or the Aerospace
Plane require high performance control systems which will require robust, computationally
efficient system identification algorithms. This work attempts to experimentally
verify, develop, and compare existing identification algorithms to determine their properties
and improve their efficiency towards potential applicability in a space environment.
To this end, we consider the Temporal Correlation Method and the Eigensystem
Realization Algorithm. The algorithms are implemented on the Astronautics Laboratory
Grid structure, and the results of the algorithms are compared in the presence of
damping, noise, and residual modes. In addition, the Temporal Correlation Method is
shown to be a constrained version of the Eigensystem Realization Algorithm for cases
of light damping.
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