design space pruning heuristics and global optimization method for ...
design space pruning heuristics and global optimization method for ...
design space pruning heuristics and global optimization method for ...
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aBiB <<br />
25%, <strong>and</strong> 15% <strong>for</strong> Leg 1, Leg 2, <strong>and</strong> Leg 3, respectively. The number of asteroid<br />
sequences is reduced from 3072 to 131, <strong>and</strong> only 19 feasible sequences were eliminated.<br />
th<br />
The best sequence eliminated has a final mass of 653 kg, which ranks 37P<br />
P. There<strong>for</strong>e,<br />
none of the top solutions are eliminated <strong>and</strong> the <strong>design</strong> <strong>space</strong> is reduced by a factor of 23.<br />
Table 4: Pruning <strong>method</strong>ology applied to sample problem.<br />
Pruning<br />
Metric<br />
Trajectory Leg % Sequences<br />
Eliminated<br />
# Sequences<br />
Eliminated<br />
aBi+1B All N/A 2560<br />
θBwedgeB Leg 1 30% 128<br />
θBwedgeB Leg 2 25% 96<br />
θBwedgeB Leg 3 15% 42<br />
∆VBoptB Leg 1 30% 41<br />
∆VBoptB Leg 2 25% 46<br />
∆VBoptB Leg 3 15% 28<br />
2.5.2 Evaluation of Global Optimization Methods on the Sample Problem<br />
The <strong>global</strong> <strong>optimization</strong> <strong>method</strong>s under consideration are all tested on the full<br />
sample problem (instead of the pruned <strong>design</strong> <strong>space</strong>), in order to evaluate them on the<br />
largest possible <strong>design</strong> <strong>space</strong>. For the genetic algorithm, two approaches are considered,<br />
as was presented in Figure 11 <strong>and</strong> Figure 12: (1) a single-level approach, where all <strong>global</strong><br />
<strong>design</strong> variables are solved <strong>for</strong> simultaneously, <strong>and</strong> (2) a two-level approach, where an<br />
outer loop optimizer solves <strong>for</strong> the asteroid sequence <strong>and</strong> an inner loop optimizer solves<br />
<strong>for</strong> the time variables. The branch-<strong>and</strong>-bound is used solely in the two-level<br />
configuration, with the branch-<strong>and</strong>-bound <strong>method</strong> solving <strong>for</strong> the asteroid sequence <strong>and</strong> a<br />
genetic algorithm solving <strong>for</strong> the time variables.<br />
The basic genetic algorithm is applied to the sample problem in a variety of ways.<br />
In each case, the following settings must be chosen:<br />
72