Safety-Critical Control in Multi-Spacecraft Specific Tracking of Rotating Target Based on Fully Actuated System Models

This paper addresses the close-proximity multi-spacecraft mission of tracking a tumbling space object under safety constraints. The six-degree-of-freedom control objectives of spacecraft include: 1) hovering at a specific area above the target, and 2) maintaining a line of sight that continuously points toward the target. During the control process, motion constraints for both position and attitude are considered: 1) position constraints ensure collision avoidance among multiple spacecraft and the target, and 2) attitude constraints require the sensor's optical axis to avoid direct sunlight. To achieve these goals, a high-order fully actuated system is established for specific tracking, and the direct parametric method is used to design control law based on fully actuated theory. Subsequently, the backup control barrier function method with quadratic programming (CBF-QP) is introduced to the fully actuated system. This safety-critical control framework transforms the tracking control inputs, initially not considering safety, into guaranteed-safe control inputs that satisfy motion constraints. Finally, a numerical simulation of multi-satellite hovering observation is conducted to validate the effectiveness of the proposed algorithm.