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    <p><a href="http://garethrees.org/2011/07/04/strandbeest/strandbeest.html" rel="noreferrer">Try the demo!</a></p> <p><img src="https://i.stack.imgur.com/wCTVS.png" alt="enter image description here"></p> <p>This is a fascinating question, though I think somewhat beyond the scope of Stack Overflow: it's not something that going to be solved in a few minutes, so I'll stick an outline here and update it if I make any progress. There are going to be three parts to any approach:</p> <ol> <li><p>Scoring the footprint: does the linkage break? does the footprint have the right kind of shape? how flat is it? how smooth is the motion? does it spend enough time in the flat portion?</p></li> <li><p>Searching for good values of the magic numbers. It's not clear that this has to be an evolutionary algorithm (though I can see why the idea of such an algorithm would appeal to Theo Jansen as it fits in with the animal metaphor in his art); perhaps other approaches like local search (hill climbing) or simulated annealing would be productive.</p></li> <li><p>Searching for good configurations of the arms. This is where an evolutionary approach seems like it might be most worthwhile.</p></li> </ol> <p>You can try out different magic numbers in my Javascript/canvas demo to see what kinds of motion you can get (CD = 55.4 is quite entertaining, for example). There's a whole <a href="http://www.math.toronto.edu/~drorbn/People/Eldar/thesis/default.htm" rel="noreferrer">mathematical theory of linkages</a>, by the way, that connects the configuration spaces of linkages to topological manifolds.</p> <hr> <p>I added some simple scoring to the demo. The <em>ground score</em> is the fraction of the cycle that the foot spends on the ground, which I take to be all points whose y-coordinate is within some tolerance of the lowest point. The <em>drag score</em> is the biggest difference between any two horizontal velocities while the foot is on the ground. (It's always negative, so that higher values = small differences in velocities = better.)</p> <p>But here's where the difficulty comes in. In order to program any kind of search, I need to be able to combine these scores. But how do I balance them against each other? The Jansen magic numbers give me groundScore: 0.520; dragScore: -0.285. If I set AC=10, GH=65, EH=50, i get groundScore: 0.688; dragScore: -0.661. Nearly 70% of the time the foot is on the ground. But the take-off is draggy. Is it better or worse than Jansen's?</p> <p>I think that getting actual engineering feedback in order to determine a good score is going to be the big problem here, not the actual search.</p>
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    1. POEvolutionary Algorithm for the Theo Jansen Walking Mechanism
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    1. COThe parametrized version of your applet is great! When I get some graphics for the fitting error, I will update my code!
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    2. COVery neat demo Gareth!
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    3. COYou did a great job introducing the scores, Gareth! As a suggestion, I would try to test horizontal displacement instead of speeds, since the result would come in the same length units used to build the linkage. Also, we must be aware that some combinations change the slope of the ground-contact path, so the points pertaining to this path should be within the tolerance distance from the double-tangent (if the path has some concave section) or minimum-curvature-tangent (if the path is fully convex) line. Indeed a very tricky problem...
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