Singularity-free task-priority design for trajectory tracking in space robots

Space robots, i.e., spacecraft with robotic manipulators, are essential for in-orbit servicing and debris removal. The high actuation redundancy of these systems allows for the imposition of multiple tasks with different priority levels. This work presents a singularity-free task-priority design for trajectory tracking in space robots, effectively removing the stringent assumption that the manipulator operates within the feasible workspace (free of kinematic singularities). The design, based on a modular hierarchical architecture, ensures end-effector tracking takes priority over tasks like maintaining a safe distance and a proper attitude of the spacecraft base. The proposed control law uses a 6D matrix representation of rigid motion that unifies attitude and position, offering invariance to inertial frame changes, making it ideal for space robotics.