Global ETD Search

1	Scheduling of a Constellation of Satellites: Improving a Simulated Annealing Model by Creating a Mixed-Integer Linear Model Monmousseau, Philippe January 2015 (has links) The purpose of this thesis is to provide a new scheduling model of a large constellation of imaging satellites that does not use a heuristic solving method. The objective is to create a mixed-integer linear model that would be competitive in speed and in its closeness to reality against a current model using simulated annealing, while trying to improve both models. Each satellite has the choice between a number of possible events, each event having a utility and a cost, and the chosen schedule must take into account numerous time-related constraints. The main difficulties appeared in modeling realistically a battery level and in handling infeasible configurations due to inaccurate parameters. The obtained linear model has enabled a better understanding of the performance of the simulated annealing solver, and could also be adapted to different real-world scheduling problems. Mixed-Integer Linear Optimization Mathematics Matematik
2	Time-window optimization for a constellation of earth observation satellite Oberholzer, Christiaan Vermaak 02 1900 (has links) Thesis (M.Com.(quantitative Management)) / Satellite Scheduling Problems (SSP) are NP-hard and constraint programming and metaheuristics solution methods yield mixed results. This study investigates a new version of the SSP, the Satellite Constellation Time-Window Optimization Problem (SCoTWOP), involving commercial satellite constellations that provide frequent earth coverage. The SCoTWOP is related to the dual of the Vehicle Routing Problem with Multiple Timewindows, suggesting binary solution vectors representing an activation of time-windows. This representation fitted well with the MatLab® Genetic Algorithm and Direct Search Toolbox subsequently used to experiment with genetic algorithms, tabu search, and simulated annealing as SCoTWOP solution methods. The genetic algorithm was most successful and in some instances activated all 250 imaging time-windows, a number that is typical for a constellation of six satellites. / Quantitative Management Satellite scheduling Genetic algorithms Metaheuristics Simulated annealing Vehicle Routing Multiple time-windows Constellation of satellites Tabu search 621.3825 Artificial satellites-- Scheduling Remote sensing-- Mathematics Heuristic algorithms Earth sciences-- Remote sensing
3	Time-window optimization for a constellation of earth observation satellite Oberholzer, Christiaan Vermaak 02 1900 (has links) Thesis (M.Com.(quantitative Management)) / Satellite Scheduling Problems (SSP) are NP-hard and constraint programming and metaheuristics solution methods yield mixed results. This study investigates a new version of the SSP, the Satellite Constellation Time-Window Optimization Problem (SCoTWOP), involving commercial satellite constellations that provide frequent earth coverage. The SCoTWOP is related to the dual of the Vehicle Routing Problem with Multiple Timewindows, suggesting binary solution vectors representing an activation of time-windows. This representation fitted well with the MatLab® Genetic Algorithm and Direct Search Toolbox subsequently used to experiment with genetic algorithms, tabu search, and simulated annealing as SCoTWOP solution methods. The genetic algorithm was most successful and in some instances activated all 250 imaging time-windows, a number that is typical for a constellation of six satellites. / Quantitative Management Satellite scheduling Genetic algorithms Metaheuristics Simulated annealing Vehicle Routing Multiple time-windows Constellation of satellites Tabu search 621.3825 Artificial satellites-- Scheduling Remote sensing-- Mathematics Heuristic algorithms Earth sciences-- Remote sensing

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