A distributed self-assembly approach for hollow shape in swarm robotics

The subtractive manufacturing of machining and the additive manufacturing of 3D printing rely on special processing equipment, and the produced parts have inherent flaws such as single function and non-reusability. Combining with the development of self-assembly in swarm robotics, a programmable forming method with flexible task is previously proposed. However, self-assembly of hollow shapes which have a hole inside has proved to be difficult to achieve, because robots in the hollow shape have less communication and reference to make decisions, while individuals make decisions purely through local interactions. In this paper, we propose a novel distributed self-assembly approach for hollow shape, which employs the stratified mechanism and uses a chain forming approach. The novel approach mainly includes the methods of state update, follow-up motion, rule extension, and trapped planning, respectively, solving the message blocking, motion separation, and robot trapped problems when the motion-chains fill up the hollow shape. We evaluate the feasibility and flexibility of this approach in simulation, and demonstrate the self-assembly algorithm on the hardware robotic platform designed in our lab. The formation of the hollow shape expands the range in which self-assembly can be formed, making it suitable for various types of parts.