Constraints Tightening Approach Towards Model Predictive Control Based Rendezvous and Docking with Uncooperative Targets

This paper presents a guidance & control strategy and a case study for rendezvous and docking with an uncooperative target based on Model Predictive Control (MPC). It is shown that linear invariant constrained MPC is not able to stay in the centre of the line of sight constraint while approaching a target. Then, online constraint tightening framework is proposed to mimic straight line approach in the relative frame while orbiting around the tumbling target. Our formulation also includes quadratic input constraints to address the physical limitations of a thrust configuration along a single axis. The concept of the tightening constraints framework is eventually validated through simulations to achieve docking conditions while staying in the centre of the line of sight cone.