Snail robots as a new paradigm for swarm robotics in unstructured environments

Abstract Terrestrial robot swarms that can self-reconfigure offer adaptable solutions for various tasks and environments. However, most existing terrestrial robot swarms remain confined to controlled indoor environments. We introduce a novel 3D terrestrial snail robotic swarm system inspired by the morphological attributes of land snails, specifically engineered for unstructured environments. Contemporary reconfigurable terrestrial robotic swarms rely on free connections for adaptability and scalability. Unfortunately, these mechanisms often compromise stability or are time-intensive in reconfiguration. Addressing these limitations, we present a hybrid-connection system that integrates two distinct modes, drawing inspiration from the unique adhesive mechanisms of land snails. The free mode, mirroring a snail's routine locomotion, leverages magnet-embedded tracks to create a medium-stability connection with an iron spherical shell. This facilitates crucial movements such as sliding, yawing, and transitioning amongst other robots, thereby augmenting the swarm's configurational adaptability and operational efficiency. In contrast, the strong mode, analogous to a snail's enhanced suction response when disturbed, utilizes an active vacuum sucker with directional polymer stalks. This mode provides robust adhesion to the spherical shell, establishing high stability for fixed configurations. The system expertly balances mobility and secure connection needs by assigning specific functions to each mode. Our outdoor experiments highlight not only the advanced capabilities of individual snail robot units but also the exceptional synergy within the swarm, effectively demonstrating its proficiency in navigating diverse terrains and executing manipulative tasks. This research propels the evolution of terrestrial robotic swarms, widening the horizons for their real-world applications, particularly in unstructured outdoor environments.