Automated spacecraft docking is a concept of operations with several important
potential applications. One application that has received a great deal of attention
recently is that of an automated docking capable unmanned re-supply spacecraft. In
addition to being useful for re-supplying orbiting space stations, automated shuttles
would also greatly facilitate the manned exploration of nearby space objects, including
the Moon, near-Earth asteroids, or Mars. These vehicles would allow for longer
duration human missions than otherwise possible and could even accelerate human
colonization of other worlds. This thesis develops an optimal docking controller for an
automated docking capable spacecraft. An innovative vision-based relative navigation
system called VisNav is used to provide real-time relative position and orientation
estimates, while a Kalman post-filter generates relative velocity and angular rate estimates
from the VisNav output. The controller's performance robustness is evaluated
in a closed-loop automated spacecraft docking simulation of a scenario in circular
lunar orbit. The simulation uses realistic dynamical models of the two vehicles, both
based on the European Automated Transfer Vehicle. A high-fidelity model of the
VisNav sensor adds realism to the simulated relative navigation measurements. The
docking 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 in
vehicle 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 was
robust to both types of mass property modeling errors, as well as both types of initial
condition modeling errors, even in the presence of sensor noise. The VisNav
system was found to perform satisfactorily in all test cases, with excellent estimate
error convergence characteristics for the scenario considered. These results demonstrate
preliminary feasibility of the presented docking system, including VisNav, for
space-based automated docking applications.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2009-08-2820 |
| Date | 14 January 2010 |
| Creators | Morris, Jeffery C. |
| Contributors | Valasek, John |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis |
| Format | application/pdf |
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