The DLR On-Orbit Servicing Simulator: Reproducing Free-Floating Dynamics with Robotic Facilities

The use of spacecrafts equipped with robotic manipulators is recognized as a promising technology with two major applications. On one hand, to safely collect and de-orbit objects and thus mitigate the development of space debris; on the other hand, to repair and extend the lifetime of mal-functioning satellites. One of the major difficulties to accomplish an OOS mission is that it needs to be tested on-ground prior to the launch. Hence, a reliable simulator is required and must be capable of reproducing the microgravity conditions on ground in the most realistic manner. Robot-based facilities can effectively implement active gravity compensation and allow unconstrained motions within the robot workspace. The OOS-SIM is an on-ground robotic facility developed in DLR and is devoted to simulate on-orbit servicing missions. The set-up is based on industrial robots equipped with force-torque sensors to simulate satellite dynamics in space and interaction forces between different bodies. This presentation will provide an overview on the advancements and capabilities of the OOS-SIM in the area of dynamic, autonomous and teleoperation control. It will outline the benefits and limitations of using this kind of robotic facilities. In particular, it will be shown how the intrinsic time delays and further discretization effects found in the robot control loops can distort the simulated dynamics. These effects will be identified, isolated and addressed through different energy-based control strategies to ensure faithful dynamics simulation while preserving system stability.