The Motion Suspension System for On-Ground Tests of Space Robots: Demonstration and Results

Space robotics plays a significant role in advancing space exploration creating various opportunities for upcoming space missions. Robotic systems deployed on satellites can be used to extend the lifetime of target satellites, inspect orbital assets, and support the deorbiting process. On-ground verification and validation are essential for ensuring the reliable performance of the robot in space. However, space robots are designed for zero gravity conditions, but are tested within Earth’s gravity. This creates significant challenges as the robotic joints provide limited torque preventing them from performing movements in Earth’s environment. Against this background, the Institute of Robotics and Mechatronics at the German Aerospace Center (DLR) and the University of Duisburg-Essen have developed the Motion Suspension System (MSS), a cable-driven parallel robot that enables space robots to operate in the full three-dimensional workspace. This paper outlines initial experiences with the MSS by focusing on a contact-oriented task utilizing the space-qualified DLR robot arm CAESAR (Compliant Assistance and Exploration SpAce Robot). It shows the applied suspension forces of the MSS in relation to the robot arm’s gravitational force, discusses the system’s limitations and capabilities in executing complex trajectories, and presents general lessons learned from using the MSS for verification.