The growing satellite congestion in Earth orbits increases the risk of Kessler Syndrome, that could potentially hinder humanity's activities in space. This problem could be tackled with Active Debris Removal or On-Orbit Servicing missions. This thesis project aimed to investigate the combined controller approach for OOS mission reach phase, in which both the s/c base and robotic manipulator are actively controlled by a single control system. The multi-body dynamics were defined with the SpaceDyn toolbox in Matlab and the advanced control method was chosen, Model Predictive Control (MPC). The advantage of MPC is the optimization-based strategy, a straightforward definition of constraints and dynamics prediction within the future horizon. The NMPC approach with successive linearization was designed and verified, the controller was tuned and the control system was tested in simulated scenario cases. This study was performed in collaboration with the German Aerospace Center DLR within RICADOS project.

Nowadays, a satellite is considered as out of range forever once it is launched. This may soon no longer hold thanks to on-orbit servicing. However, the complexity of that topic makes it highly challenging on many aspects. On-orbit servicing using a robotic arm is nonetheless the most investigated technology in order to achieve the berthing of two satellites in orbit. This research project aims at developing a robust controller for the deployment of a robotic arm, which is mounted on a servicer satellite, and for the reaching of a defined handle on the target satellite under mission constraints. While operating the space manipulator, the combined control of both the manipulator and the spacecraft base has a great potential in terms of achievable performance and may bring robotic on-orbit servicing one step closer to reality. In order to reveal the potential of this innovative control strategy, a model of the system dynamics was developed, before being used to design a robust controller. The latter was then successfully implemented in different simulators to test its performance and robustness to a variety of constraints including hardware, environment and mission constraints. The simulations proved that combined control can be used for the entire maneuver. Finally, this controller was successfully implemented in the on-board computer of the on-orbit servicing simulator at the German Aerospace Center. From now on, the maneuver can be completed from the ground control room. The implementation of the robust and combined controller has increased the technology readiness level of the reach phase during an on-orbit servicing mission.