Multibody dynamics and robust control of flexible spacecraft

The paper focuses on an approach to the study of the dynamics and control of large flexible space structures, comprised of subassemblies, a subject of considerable contemporary interest. To begin with, a relatively general Lagrangian formulation of the problem is presented. The governing equations are nonlinear, nonautonomous, coupled, and extremely lengthy even in matrix: notation. Next, an efficient computer code is developed and the versatility of the program illustrated through a dynamical study of the first element launch (FEL) configuration of the Space Station Freedom, now superseded by the International Space Station. Finally, robust control of the rigid body motion of the FEL configuration using both the linear-quadratic-Gaussian/loop transfer recovery (LQG/LTR) and H-infinity procedures is demonstrated. The controllers designed using the simplified linear models, prove to be effective in regulating librational disturbances. Such a global approach-formulation, numerical code, dynamics, and control-is indeed rare. It can serve as a powerful tool to gain comprehensive understanding of dynamical interactions and thus aid in the development of an effective and efficient control system.