Morphological evolution of freeform robots

Abstract

We demonstrate the evolution of locomoting amorphous robots composed of multiple materials. Research in evolutionary robotics has traditionally been limited to morphologies comprising rigid and discrete components, such as links connected with rotational or linear joints and actuators. In the continuous robots presented here, actuation is accomplished by periodic volumetric expansion and contraction of one or more materials composing the body of the robot. The challenges of representing evolvable multi-material freeform shapes and evaluation (simulation) of the resulting soft bodies are discussed. Several genotypic representations are explored which use a level-set threshold to generate the material distribution in the phenotype. Soft body simulation of the robot is accomplished using a relaxation algorithm to model the dynamics of the resulting amorphous machines under the actuation material expansion, gravity forces, and non-linear ground friction. These results open the door to a new design space that more closely mimics the freeform, amorphous and continuous nature of biological systems.