Ground-Truth Validation of the Motion Suspension System for the Qualification of Space Robotic Manipulators

Future space missions, including satellite life extension, orbital asset inspection, and deorbiting, rely heavily on space robotic manipulators. However, testing these robots on Earth presents significant challenges, as they are designed to operate in zero gravity but must be tested under 1 g conditions. Since the joints of most space manipulators cannot support their own weight under Earth gravity, mechanical support systems are required to reduce the gravitational joint loads. 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 cabledriven parallel robot that enables ground-based testing of space robotic manipulators in a fully three-dimensional workspace. This paper presents a quantitative assessment of force reconstruction accuracy, for ground-truth validation of the MSS. Using optical motion capture, we achieved sub-degree accuracy in measuring suspension force direction, identifying systematic errors and improving system performance by 15.6%. This study is crucial to validate the MSS as a qualification platform for space robotic manipulators.