Optimizing the Locomotion of a Robotic Active Matter System of Smarticles

We consider the locomotive properties of an active matter system of shape-changing robots. This system is composed of smart, active particles, termed smarticles, that interact with each other via inter-robot collisions. In contrast to meticulously designed traditional robots, the smarticle robot swarm consists of generic, reconfigurable components noisily interacting. Although control of such a collective is beyond existing methods, the resulting system would be scalable, robust, and flexible in structure. Rather than adapting the model-agnostic formalisms of control theory, we posit that by considering the fundamental physics of the system, the swarm may become controllable. We have shown that when enclosed in a rigid ring, the smarticles exhibit emergent locomotion if the symmetry of internal configurations is broken by an inactive robot. Here, we use geometric mechanics to optimize robot inactivations to allow for faster directed locomotion in the plane. We demonstrate this in an experimental system of five smarticles and find that the system locomotes optimally when two smarticles are inactive. Finally, we find an expression for the optimal number of inactive smarticles as a function of the size of the swarm.