Visual Servoing and Impedance Control in Robotic Manipulators for On-Orbit Servicing

This paper presents a controller for a robotic manipulator for spacecraft docking operations oriented to on-orbit servicing. The proposed controller combines visual and force/torque feedback in order to complete the approach and contact phases of the docking. Visual servoing is used not only for guiding the end-effector during the approach phase, but also to maintain the end-effector probe correctly aligned during the contact phase. During the contact phase, an impedance controller generates the compliant behavior needed to minimize the peak forces that could result in a failed docking. The proposed controller has been tested experimentally in a hardware-in-the-loop robotic test-bench showing that in this ground-testing environment docking can be completed successfully for a set of initial conditions (relative speed of the spacecraft).