ReLMBot: A Reconfigurable, Legged, Miniature, Modular Robot With Compliant or Rigid, Magnetic Connection Mechanisms

This letter presents ReLMBot, a reconfigurable, legged, miniature, modular robot with magnetic and passive mechanisms. The robot comprises multiple modules, each equipped with backbones featuring permanent magnets, which offer reconfigurability without requiring additional power or actuation while enhancing the robot's compliance. Moreover, by choosing the geometry of the magnets differently, the connections can be made rigid (square-shaped) or compliant (cylindrical). A dynamic model incorporating the robot's magnetic connections is developed to simulate and verify its climbing performance and docking/undocking behavior. The results demonstrated that cylindrical magnets achieve a higher success rate in climbing obstacles and provide significantly higher additional climbing height compared to square-shaped magnets as the number of modules increases. Furthermore, the robot's starting position relative to the obstacle has a major impact on its climbing success. Modules with square-shaped magnets maintain near 100% success until just below their climbable limit, then drop sharply, especially with fewer modules. Cylindrical magnets show a gradual decline, turning abruptly 5 mm before failure. The modules weigh 29.43 grams and have palm-sized dimensions, allowing them to dock and undock to perform various tasks, including climbing obstacles higher than a single module. The modules possess soft c-shaped legs, enabling operation in diverse terrains like gravel, sand, or grass. The modules' miniature structure, ease of manufacture, and affordability make them a suitable option for multiple use cases. The robot's wireless communication capability makes it a strong contender for surveillance in confined spaces like collapsed buildings and nuclear sites, large areas like farmlands, and even planetary exploration missions.