Design and Validation of Orbital Robotic Missions

Abstract

A servicer spacecraft equipped with robotic manipulators is a key technology for space debris removal and on-orbit servicing missions. The servicer is a composite system consisting of robotic manipulators, on-board cameras, proprioceptive and exteroceptive sensors, and the spacecraft actuation system. This hybrid nature of sensing and actuation on the spacecraft and manipulator subsystems poses several challenges to achieve the task of the robotic mission. This chapter outlines the challenges in such robotic missions and provides hardware design and control strategies, with a key focus on on-ground validation. Firstly, the mission aspects of the robotic capture of a satellite are introduced while considering the e.Deorbit mission study. The on-ground verification and validation of the control algorithms under micro-gravity condition is a necessity before the space mission commissioning. To this end, a state-of-art on-ground robotic facility, namely OOS-SIM, is described and used later for validation. From a control perspective, strategies for the orbital robot including vision-based semi-autonomy, shared control and teleoperation are reviewed. In particular, these controllers are designed to accomplish the mission task while considering the dynamic interaction between the spacecraft and the manipulator, the heterogeneity of the actuators available for control, and the lack of direct measurements of the complete state. In this context, the combined impedance control of the robotic manipulator and the satellite is specifically designed to be compliant against interaction with space targets. Finally, an end-to-end validation of a space-mission for on-orbit servicing is presented involving both on-board and on-ground segments, with realistic space communication characteristics.