Evolvable mechanics: Hardware tools for evolutionary robotics

Embodying robot morphologies evolved in simulation can present serious problems for an engineer when translating simplified simulated mechanisms into working devices, often drawing on pre-existing component parts to provide specific functions, to reduce construction times and to cut costs. Actuators for generating motion in articulated joints are key components of any robot and a vast range of compact, low cost devices are available, but their behavior is based on generating positions and velocities by ironing out perturbations. In simulation it is easy to create variable compliance actuation schemes where damping and spring forces used to guide motion can be subject to evolutionary search and aid the generation of efficient adaptive behavior. We present an experimental design for a cost effective actuator module with software controlled compliance that can approximate arbitrary mechanical spring damping systems, with parameters that are software configurable at run time. The benefits of this software controlled compliance and the versatility of our embedded control system are demonstrated in a minimal walking robot. The potential value and inherent limitations of this device as a tool for evolutionary robotics, where software controlled compliant properties can form part of an evolutionary search, and in the wider field of autonomous robotics, are discussed.