An experimental investigation of modeling and optimal control of modified space structures

Author: Moser, Albert N.

Year: 1992

Degree: Dissertation (Ph.D.)

Committee Member: Caughey, Thomas Kirk

Option: Applied Mechanics

DOI: 10.7907/6cyt-4m83

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.

Future space missions will rely on structures with many closely spaced and lightly damped modes. To meet the alignment performance requirements of the missions, these structures will need to incorporate active control. Control which does not destabilize the system requires very accurate models of all modes present in a certain bandwidth of the structure's response. Development of the accurate models through system identification is significantly complicated by modes with almost equal frequencies and dampings which appear as single peaks in the structure's frequency response function. Similarly, difficulty in control will be increased by changes in the system due to docking of other systems.

A structure was built at Caltech for identification and control experiments which exhibits many of the features of large space structures. Identification, modification, and control experiments have been conducted on this system to develop optimal controllers which are robust to system changes. This thesis presents the theory and experimental results behind the modeling of modifications on the structure. It also details use of H[...]/[...]-synthesis methods for this problem. Robust controllers have been implemented so as to remove responses of the lowest nine modes of the structure. These controllers perform very well even when the structure is modified by the addition of dynamics.

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