Automated Spacecraft Docking Using a Vision-Based Relative Navigation Sensor

摘要

Automated spacecraft docking is a concept of operations with several importantpotential applications. One application that has received a great deal of attentionrecently is that of an automated docking capable unmanned re-supply spacecraft. Inaddition to being useful for re-supplying orbiting space stations, automated shuttleswould also greatly facilitate the manned exploration of nearby space objects, includingthe Moon, near-Earth asteroids, or Mars. These vehicles would allow for longerduration human missions than otherwise possible and could even accelerate humancolonization of other worlds. This thesis develops an optimal docking controller for anautomated docking capable spacecraft. An innovative vision-based relative navigationsystem called VisNav is used to provide real-time relative position and orientationestimates, while a Kalman post-filter generates relative velocity and angular rate estimatesfrom the VisNav output. The controller's performance robustness is evaluatedin a closed-loop automated spacecraft docking simulation of a scenario in circularlunar orbit. The simulation uses realistic dynamical models of the two vehicles, bothbased on the European Automated Transfer Vehicle. A high-fidelity model of theVisNav sensor adds realism to the simulated relative navigation measurements. Thedocking controller's performance is evaluated in the presence of measurement noise,with the cases of sensor noise only, vehicle mass errors plus sensor noise, errors invehicle moments of inertia plus sensor noise, initial starting position errors plus sensor noise, and initial relative attitude errors plus sensor noise each being considered.It was found that for the chosen cases and docking scenario, the final controller wasrobust to both types of mass property modeling errors, as well as both types of initialcondition modeling errors, even in the presence of sensor noise. The VisNavsystem was found to perform satisfactorily in all test cases, with excellent estimateerror convergence characteristics for the scenario considered. These results demonstratepreliminary feasibility of the presented docking system, including VisNav, forspace-based automated docking applications.