Optimal desaturation of momentum exchange control systems
Additional Document Info
This paper describes a new and systematic approach to the problem of desaturating momentum exchange controller devices as used, for instance, in attitude control systems for orbiting spacecrafts. This particular approach is notably efficient because it makes optimal use of the natural external environmental torques acting on the spacecraft (gravity-gradient torques, aerodynamic torques, etc.)- Two cases are treated: one where the predominant external disturbing torques are due to well-behaved gravity-gradient torque functions which are assumed completely known a priori; and a more general case where the magnitude and waveform of the disturbance torque functions are unknown (and cannot be measured) but are known to satisfy some given fcth-degree linear differential equation. In this latter case, a novel real-time, on-line, physically realizable disturbance estimator is used to obtain an accurate estimate of the external disturbance torques acting on the spacecraft, based on measurements of only the current system state vector. The problem of optimal desaturation of the momentum exchange controller is cast into the mathematical format of a minimal energy optimization problem for a plant represented by a linear, time-varying differential equation with a time-vary ing forcing term. 1971, American Institute of Aeronautics and Astronautics, Inc., All rights reserved.