Attitude control of flexible space vehicles

Objectives of this paper are to enhance the concept of multiple control in attitude control systems for large flexible space vehicles and to discuss some questions of stability and structure-control system interaction. The approach to the design of a multiple control system is illustrated with a typical example for which the control system configuration includes a main loop providing control for the main portion of the structure arid auxiliary loops providing active damping for the flexible appendages. Criteria for the first cut design of each auxiliary loop are given. The performance of the multiloop control system described, vs that of the corresponding single-loop, is illustrated by the results of analog simulation. Qualitative results of analysis and stability limitations of different classes of attitude control system configurations for large flexible space vehicles are also discussed. The normal mode approach particularly suitable for the use of transfer functions is considered in modeling the structure dynamics. A criterion for mode separability in a multimode structure is presented. The simplification deriving from its application to the analysis of an attitude control system is illustrated.