Evolving three-dimensional Lego structures: Table experiment

To evolve a Lego table we started with a fixed plate as in fig. 2.14, and wanted to obtain a table 10 bricks tall, with a support surface of and capable of supporting a weight of 50 g located anywhere over this surface. There were four objectives to fulfill:

1.

The height of the structure must be as required.

2.

The surface most cover the target area.

3.

The desired weight has to be supported all over the surface.

4.

All other conditions met, a minimal number of bricks should be used.

To cover all the objectives we wrote a step fitness function giving between 1 and 2 points for the first objective partially fulfilled, between 2 and 3 for the first objective completed and partial satisfaction of the second, and so on. With this setup, the algorithm built upward first, then broadened to cover the surface, later secured that all points of the surface supported a load of 50g and finally tried to reduce the number of bricks to a minimum.

One of the solutions we obtained is shown in figs. 2.4 and 2.5; fig 2.18 is a photo of the finished table.

  

Figure 2.18: Lego table as specified by the diagram of fig. 2.4, holding a 50g weight.