Tracking control for the grasping of a tumbling satellite with a Free-Floating robot

In this letter, a novel method is presented for grasping a partially cooperative tumbling satellite with a free-floating robot. A reference trajectory, provided by an offline motion planner and adapted online to account for modeling uncertainties, is tracked with a visual servo for the approach phase and with a joint-space controller for the rigidization phase, which follows the grasp. An extended Kalman filter is implemented for providing robustness, predictions during measurement unavailability and a velocity estimate of the tumbling satellite as a feed-forward for control, throughout the grasping task. The visual servo is in cascade with an impedance controller to achieve tracking while being compliant. The method is successfully validated on the OOS-SIM facility, which is used for simulating gravity-free multibody dynamics with a novel momentum-based control method.