Reaction Wheels Desaturation Using Magnetorquers Under Environmental Disturbances

Reaction wheels momentum management under the effect of modeled environmental disturbances is addressed in this paper. First, models of the spacecraft, gravity gradient, solar radiation, magnetic residue and atmospheric drag torques are established. Secondly, a control strategy involving two loops is developed where the first one controls the attitude via reaction wheels, while the second dumps the excess momentum built up in the wheels using magnetorquers. Stability is proved using Lyapunov theory, and the unwinding problem present when using quaternions is avoided by taking into account the initial state of the attitude. Finally, the results of the control strategy are examined in the numerical simulation. It is shown that the attitude can be stabilized with high speed and accuracy, while also keeping the angular momentum of the reaction wheels close to the desired value.