Energy Sharing Mechanism for Freeform Robots Utilizing Conductive Spherical Sliding Surfaces

Energy sharing among modular robots enables sustainable operation of the system by maintaining energy balance among the modules. In this paper, we propose a novel energy sharing mechanism for FreeSN, a modular self- reconfigurable robot consisting of node and strut modules. Utilizing the feature that our modules are connected in a face- to-face manner, our method successfully establishes an energy sharing channel at almost any point on a sphere by placing transmission intermediaries at the interfacing face between modules, which is facilitated by the combination of brush contact and shell decomposition. Such mechanism also allows the utilization of the node module’s inner space for extra energy storage. A prototype of this energy sharing system has been implemented on FreeSN and rigorously tested. Our findings indicate that energy sharing is reliably established between modules; for strut modules positioned randomly on a node module’s surface, the probability of forming a valid connection is 56.6%. With orientation adjustment, a connection is achievable at nearly any position on the sphere, barring a few exceptional points. As a result, the operational endurance of the strut modules, which provide all the driving forces in the system, is markedly enhanced. This technique also holds potential for broader application across other freeform robotic platforms that incorporate conductive spherical surfaces for sliding connections.