Prescribed-Time Proximity Control of Spacecraft With Collision Avoidance and Visibility Maintenance

This article addresses the prescribed-time tracking control problem for spacecraft proximity operations under spatial motion constraints, including collision avoidance and visibility maintenance. To prevent collisions with target appendages and obstacles, a cardioid-shaped keep-out zone is established around the target, forming a safety corridor, while a capsule-shaped envelope is defined for the chaser spacecraft to facilitate the analytical computation of collision distances. Additionally, a conical visibility region is constructed to ensure persistent observation of target features, which transforms visibility maintenance into an equivalent collision avoidance formulation. Subsequently, a prescribed-time safe proximity controller is developed by employing artificial potential fields and a Robust Integral of the Sign of the Error (RISE)-based disturbance observer in conjunction with the time-scale transformation technique. Lyapunov stability analysis shows that the designed controller guarantees that the chaser reaches the desired position within a prescribed finite time, while strictly complying with spatial motion constraints, despite the presence of disturbances. Finally, the efficacy of the proposed method is validated through comprehensive numerical simulations.