Micro-satellite Reconfigurable Attitude Control Laws with Reaction Wheels Desaturation and Fault Management

This paper proposes a new reconfigurable control strategy for the attitude control of a Low Earth Orbit (LEO) micro-satellite equipped with reaction control wheels and reaction control thrusters (used as a secondary actuation system). Control laws are combined with control allocation algorithms that enable the optimal allocation of control effort in case of reaction wheels saturation and/or faults as well as when control limits are reached (e.g. maximum torques provided by reaction wheels). This allows to effectively use the redundancy of the actuators set and guarantee robust stability and control of the satellite attitude. The effectiveness of the proposed strategy has been assessed through a numerical analysis that includes several simulation scenarios, where different initial conditions have been set and also the fault of a reaction wheel has been simulated. Simulations have shown the ability of the control architecture to effectively manage several control issues (i.e. maximum achievable torques, reaction wheel saturation and faults) through the allocation of control effort among all the available control effectors.