Real-Time Satellite Proximity Operations Using Electromagnetic Interactions with Singularity-Robustness and Modeling Error Compensation

This paper proposes a real-time 6-DOF proximity control method using electromagnetic forces and torques to enable future on-orbit infrastructure. The long-duration stable and accurate proximity control method is required for onorbit infrastructure such as on-orbit servicing and distributed aperture systems. Fuel-less electromagnetic actuators enable such proximity control. Conventional electromagnetic proximity control faces two main challenges. The first is the trade-off between control accuracy and computation time. Rigorously calculating electromagnetic interactions improves accuracy but requires substantial computation time, while simplified models neglect the effects of coil shape and arrangement. The second challenge is control singularities, where the electromagnetic actuation matrix becomes rank-deficient. These conditions can occur unexpectedly in proximity region and compromise system safety. The proposed control architecture addresses both challenges. A computationally efficient model that accounts for coil arrangement effects-significant in close proximity-is combined with a disturbance observer (DOB) to compensate for near-field modeling errors and enhance accuracy. A statedependent Riccati equation (SDRE) controller is designed to improve the robustness against singularities. Numerical simulations of docking maneuvers demonstrate the effectiveness of the proposed method. Even in scenarios where conventional methods fail due to singularities, the proposed method achieved 1 cm position and 3° attitude accuracy while being nearly 10 times more computationally efficient. Case studies further confirm robustness across various realistic coil arrangements. Overall, the results indicate a practical framework for electromagnetic proximity control, combining computational efficiency with accuracy and robustness.