Control of a Satellite-Mounted Manipulator for on-orbit grasping via Incremental MPC

The thesis focuses on the grasping maneuver of a target satellite performed by a spacecraft-manipulator system. This technology's appeals lies in its ability to enhance activities like in-orbit repairs and refueling, that are usually collected under the term "in-orbit services" (IOS). The project is carried out in collaboration with D-Orbit S.p.A., which together with the European Space Agency (Esa) plans to complete the first European IOS mission in the coming years. The scenario considered in the thesis involves two satellites that are supposed to be in free-floating mode. The equations-of-motion of the spacecraft-manipulator system are derived for the proper mode of operation. The adopted control strategy is developed in the framework of optimal control, specifically Model Predictive Control (MPC). However, since it is important to guarantee real-time feasibility of the architecture, the system is linearized via the time-delay estimation (TDE) technique. The resulting controller is termed Incremental MPC (IMPC). The application-specific generalized Jacobian matrix is employed to automatically compensate for the coupling existing between the base satellite and the robotic arm and related to the system free-floating dynamics. Then, a Simulink-Simscape multibody simulator is developed to test the control law in different conditions. The validity of the IMPC controller is assessed through a Monte Carlo simulation. The main advantage of the proposed control law with respect to other proposed controllers it its capability of providing the control input in real-time in a useful time.