On Robust Coordinated Compliant Control Design for Space Manipulators under Flexible and Uncertain Dynamics
Kostas Nanos, Evangelos Papadopoulos
AI summary
Problem
Robotic capture in space often suffers from contact loss, dangerous impact forces, and spacecraft attitude drift during the transition to physical contact. Existing controllers typically require discrete switching or lack robustness to realistic orbital disturbances.
Approach
The authors propose a Coordinated Compliant Control (CCC) law that uses continuous nonlinear gain scheduling to smoothly transition between PD tracking and impedance-based force regulation, explicitly modeling coupled rigid-body dynamics and reaction wheel actuation.
Key results
- Switching-free transition between free-space and contact phases
- Effective regulation of peak contact forces to prevent structural damage
- Maintenance of chaser spacecraft attitude stability during manipulation
- Verified robustness to solar panel oscillations and sensor noise in high-fidelity simulations
Why it matters
This method directly mitigates critical failure modes in on-orbit servicing, enabling safer and more reliable robotic capture operations for future space missions.
Abstract
This paper presents a coordinated compliant control strategy for space manipulator systems to enable safe and robust target capture during on-orbit servicing and assembly missions. The proposed controller operates in two distinct phases: free-space motion and contact interaction. In the free-space phase, end-effector accurate trajectory tracking is required, while in the contact phase, the control objective shifts to force regulation, maintaining contact forces within safe bounds and ensuring stable interaction durations to enhance operational safety. A key feature of the developed method is its ability to provide a smooth and continuous transition between free-space and contact phases without requiring controller switching. Furthermore, the controller preserves the attitude stability of the chaser spacecraft during manipulation, mitigating mission-critical risks such as communication loss or solar panel misalignment. The approach explicitly incorporates the coupled rigid-body dynamics of the SMS and demonstrates robustness to various real-world disturbances. Simulation results validate the effectiveness of the proposed controller. Future work includes experiments, using the planar Space Robotics Emulator of our lab at the National Technical University of Athens to assess real-world readiness.