Adaptive Proximity Control of Spacecraft With Collision and Occlusion Avoidance

Abstract

This article addresses the relative position tracking problem for safety-critical spacecraft proximity operations (SPOs), in the presence of collision and occlusion avoidance constraints as well as mass uncertainty. A spherical keep-out zone is established around the target to prevent collisions with its appendages, while a capsule-shaped envelope is designed for the pursuer to enable analytical calculations of collision distances between the pursuer and obstacles. To prevent visual occlusion of target features by obstacles, an ice-cream-shaped visibility cone encompassing all the extracted target features is constructed. Given this, the occlusion avoidance problem is formulated as a collision avoidance problem between the intervening obstacle and the visibility cone, which has a continuously differentiable collision distance. Subsequently, a dynamically scaled immersion and invariance (I&I) adaptive controller is developed, leveraging potential functions to handle collision and occlusion avoidance as well as velocity constraints. The I&I adaptive controller enables the pursuer to asymptotically reach the desired position without colliding with the target and obstacles, while maintaining visibility of target features, despite the presence of mass uncertainty. Simulation results demonstrate the effectiveness of the proposed method.