AAS 96-176

ATTITUDE CONTROL AND MOMENTUM MANAGEMENT OF SPACECRAFT BASED ON A SENSITIVITY OBSERVATION

R. R. Kumar and H. Seywald, Analytical Mechanics Associates, Inc.

Abstract

Periodic attitude control and momentum management is of critical importance to spacecraft such as Space Station which cannot afford the huge fuel penalty incurred by momentum dumping via the Reaction Control System. The problem is made complicated due to the widely varying configurations during the build up sequence. This has resulted in different controller architectures for different configurations making the attitude control system extremely complex. It is well known that the disturbing torque (which includes the aerodynamic, solar, and torques transmitted through articular joints) acting on the spacecraft core varies as a function of true anomaly. It is observed for a large class of spacecraft configurations, such as the build up sequence configurations of the Space Station, that the sensitivity of the disturbance torque to perturbations in attitude of the core is quite independent of the true anomaly. Moreover, in the vicinity of the torque equilibrium attitude, the change in the disturbance torques show a linear dependence on the attitude perturbation. These observations are used to derive a simple linear feedback controller with time varying gains, based on linear quadratic optimal control theory. The single attitude controller / momentum manager was tested successfully on several different configurations of the Space Station in realistic simulated space environments.