Evolving robot morphology

True evolvable hardware should evolve whole hardware structures. In robotics, it is not enough only to evolve the control circuit; the performance of the control circuit is dependent on other hardware parameters-the robot body plan, which might include body size, wheel radius, motor time constant, sensors, etc. Both the control circuit and the body plan co-evolve in true evolvable hardware. By including the robot body plan in the genotype as a kind of Hox gene, we co-evolve task-fulfilling behaviors and body plans, and we study the distribution of body parameters in the morphological space. Further, we have developed a new hardware module for the Khepera robot, namely ears with programmable amplifiers, synthesizers and mixers, that allow us to study true evolvable hardware by modelling the evolution of auditory sensor morphology.