The robot is the tether: active, adaptive power routing modular robots with unary inter-robot connectors

This paper describes a novel approach to powering a radical type of microrobot. Our long-term aim is to enable the construction of ensembles of millions of coordinated near-spherical, submillimeter microrobots. Both the large number of potential simultaneous neighbors of each robot (12) and the difficulty of fine actuation at such small scales preclude the use of complex connectors previously developed in many modular robotics efforts. Instead, we propose to leverage multirobot cooperation to simplify the mechanics of modular robot docking. In our approach, the robots actively cooperate to route virtual power busses (both supply and ground) to all the robots in the ensemble using only unary (single conductor) electrical connectors between robots. A unary connector allows for larger tolerances in engagement angle, simplifies robot manufacture, speeds reconfiguration, and maximizes the proportion of the connector surface area useful for carrying current. The algorithms we present permit a robot ensemble to efficiently harvest and distribute power from sources discovered in the environment and/or carried by the ensemble. We evaluate these algorithms in a variety of simulated deployment conditions and report on the impact of hardware defects, limited on-board power storage, and the ensemble-environment interface.