Momentum Unloading of SmArT Reaction Wheels with Magnetic Torquers

This paper deals with the attitude control of a microsatellite for multi-mission applications in sun-synchronous orbits. The microsatellite is three-axis stabilized by means of three lightweight reaction wheels. In this paper, the wheel momentum dumping with magnetic torquers is analyzed. In particular, control techniques are developed that simultaneously perform the wheel momentum dumping and guarantee the required attitude control accuracy. To this end, a mathematical model is used that considers the variation of the Earth's magnetic field along the orbit. The effectiveness of proposed control techniques is numerically tested using a code that simultaneously integrates the microsatellite orbital and attitude dynamics. © 2000 Lister Science.