Conceptualization of a Reduced-Complex Cable-Based Gravity Compensation System for Space Manipulator On-Ground Tests

Robotics is primed to play a crucial role in future space missions. By performing tasks such as on-orbit servicing, inspection and de-orbiting, space robotics can enable a sustainable use of Earth’s orbits. The DLR’s Compliant Assistance and
Exploration SpAce Robot (CAESAR) is a light-weight, dexterous robot with seven degrees of freedom designed for on-orbit servicing in the Geostationary Earth Orbit (GEO).

As CAESAR is designed for microgravity, it requires external gravity compensation to operate on-ground within joint torque limits. The CAESAR laboratory at Oberpfaffenhofen (Munich, Germany) uses a cable-driven parallel robot, the Motion Suspension System, to test and validate CAESAR. The MSS is attached to the space robot at a point close to the wrist and applies an uplift suspension force that reduces the primarily gravitational torque loads in the space robot’s joints. Four actuated direct-drive motors allow to follow complex three-dimensional trajectories of the space robot arm.

However, a cable robot with four actuators is a complex and sophisticated system which cannot be easily transferred to other facilities. A reduced number of cables can improve the handling aspects of the cable robot but comes with limitations of the performance. This is why this study shall design a concept of a reduced the number of cables and analyze the limitations on the space robot’s workspace and the performance.

Experience and qualification

• Enrolled in a Master’s degree in robotics, computer science or a related.
• Knowledge of robotics dynamics
• Knowledge in MATLAB/Simulink

Tasks

• Literature review of space robotics, test facilities, and cable robotics
• Evaluation of relevant robotic parameters measuring the performance of
  the suspension system
• Design a simulation environment for analysis
• Design a concept of a one/reduced-cable space robot suspension system
• Analyze the limitations and performance of the concept

Contacts