On the Attitude Control of a Satellite with Incomplete Set of Reaction Wheels

Attitude control of a satellite is the process of orienting the satellite in a specified, predetermined direction. It consists of attitude stabilization and attitude maneuver control. In this study, when a part of actuators of the satellite becomes out of order, an alternative control algorithm has been suggested using the remaining actuators as a backup means. When two of four reaction wheels of the satellite fail, the alternative control algorithm for attitude control depends on the positions of the failed reaction wheels. When the failed wheels are placed opposite to each other, it is possible to control the attitude of the satellite using the only remaining two reaction wheels. However, when they are placed adjacent to each other, the attitude control would still be possible using the proper combination of the remaining wheels and dissimilar actuators. It has been found by a series of simulation that the currently suggested control algorithm would be successful in controlling the attitude of the satellite with defective reaction wheels.