Uncertainty Modeling and Experiments in Control of Large Flexible Space Structures

Abstract—Approaches to uncertainty modeling for robust con-trol of large flexible space structures (LFSS’s) such as additive or multiplicative perturbations in H 1 do not work very well because of the special properties of LFSS dynamics. In this paper, we propose the use of a left-coprime factorization (LCF) of LFSS dynamics in modal coordinates in order to get improved stability margins and performance in robust control design. The plant uncertainty is then described as stable perturbations of the coprime factors accounting for modal parameter uncertainty and unmodeled dynamics. Two multivariable H 1 designs based on LCF’s of 46th-order collocated and noncollocated models of an LFSS experimental testbed are presented together with simulation and experimental results to illustrate the technique. Index Terms—Coprime factorization, digital control, flexible structures, robustness, space vehicle control, uncertain systems, H-infinity control, vibration control. I