Computer Evolution of Buildable Objects for Evolutionary Design by Computers

This chapter describes our work in evolution of buildable designs using miniature plastic bricks as modular components. Lego1 bricks are well known for their flexibility when it comes to creating low cost, handy designs of vehicles and structures. Their simple modular concept make toy bricks a good ground for doing evolution of computer simulated structures which can be built and deployed. Instead of incorporating an expert system of engineering knowledge into the program, which would result in more familiar structures, we combined an evolutionary algorithm with a model of the physical reality and a purely utilitarian fitness function, providing measures of feasibility and functionality. Our algorithms integrate a model of the physical properties of Lego structures with an evolutionary process that freely combines bricks of different shape and size into structures that are evaluated by how well they perform a desired function. The evolutionary process runs in an environment that has not been unnecessarily constrained by our own preconceptions on how to solve the problem. The results are encouraging. The evolved structures have a surprisingly alien look: they are not based in common knowledge on how to build with brick toys; instead, the computer found ways of its own through the evolutionary search process. We were able to assemble the final designs manually and confirm that they accomplish the objectives introduced with our fitness functions. This chapter discusses background and related work first (section 2), then goes on to describe our methods; first the model we use to simulate Lego structures (sections 3-4), then the representation and evolutionary algorithms (section 5). The results sections (6-7) discuss applications, showing the results of several evolutionary runs and illustrating with pictures of the final assembled Lego artifacts. Finally, on sections 8-9, current and future lines of work and conclusions are drawn.