A Momentum-based Relative Dynamics Model for Hardware-in-the-Loop Simulation of On-Orbit Servicing

Kurzfassung

Due to the increasing amount of debris orbiting the Earth, on-orbit proximity operations have become an increasingly critical research topic. This type of maneuvers generally involves a chaser spacecraft docking with a target, to ultimately perform life-extension or deorbiting operations. As a result, these technological advancements aim to contribute to a more cost-effective and sustainable approach to space missions. This thesis focuses on the development of a novel control formulation for floating-base robotic systems, such as satellites, which is optimized for the context of on-orbit servicing. Specifically, the proposed dynamics representation allows the control of the motion of multiple systems both synchronously and independently, eliminating the need for acceleration measurements of the bodies. This capability can be effectively exploited to achieve docking in a wide range of configurations. In parallel, the work provides a relative dynamics notation that is utilized to successfully overcome the problem of reduced experimental workspace, intrinsically possessed by the robotic simulators employed during the on-ground testing. This work was entirely developed at the Robotics and Mechatronics Institute of the German Aerospace Center (DLR). Accordingly, the validation phase was conducted on the On-Orbit Servicing Simulator (OOS-SIM): a cutting-edge Hardware-in-the-Loop (HIL) facility for microgravity conditions. Therefore, the outcome of this thesis is a novel concept for on-ground validations, which effectively ensures physical consistency with the real mission scenario. In particular, the HIL simulator replicates only the relative motion between the two spacecraft, while their real total behavior is visualized in real-time through dedicated software.