Formation Control of Underactuated Spacecraft

This paper presents a control design for the formation flying of multiple spacecraft with full rotational actuation and a single-axis unidirectional thruster. Using a leader–follower formation architecture, the control design begins by treating each follower spacecraft as fully actuated, and generating the corresponding desired control command using a sliding mode controller robust to collisions, perturbations, and model uncertainties. Then, an attitude controller aligns the thrust direction of the underactuated spacecraft with the desired control direction, given torque limits, angular velocity bounds, perturbations, and model uncertainties. Thrust limits also constrain the desired control magnitude before it is applied by the thruster during the attitude manoeuvre. A simulation is conducted using four followers to verify the performance of the control scheme. The results demonstrate successful formation control while satisfying all operational requirements.