Combined Attitude and Orbital MPC for Thruster Based Spacecrafts

University essay from KTH/Reglerteknik

Author: Joakim Lilja; [2017]

Keywords: ;

Abstract: A spacecraft needs to simultaneously provide orbital and attitude controlbut these are in general treated as separate systems. Normally the attitudecontrol is conducted via reaction wheels but can in scenarios with high manoeuvrabilitydemands be handed over to pure thruster control. In specificcases the reaction wheels are removed from the spacecraft to save mass. Ifboth the orbital and attitude control is regulated with thrusters, there is apotential to save fuel in a combined control strategy. Model predictive controlhas been shown to be a viable method for orbital control with a fuel minimisingobjective. This thesis investigates a combined orbital and attitude model predictivecontrol strategy. Three test cases are simulated with a specific thrusterconfiguration; maintaining a passive orbit relative to a target, large-angle reorientationand repositioning, and rendezvous. Preliminary results show thatincluding the coupled dynamics lowers the overall fuel consumption while satisfyingrequirements on position and attitude in scenarios where the timescaleof the orbital and attitude control is similar.

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