Decentralized pose control of modular reconfigurable robots operating in liquid environments

Modular reconfigurable robots are touted for their flexibility, as their bodies can assume a wide range of shapes. A particular challenge is to make them move efficiently in 3D without compromising the scalability of the system. This paper proposes decentralized and fully reactive controllers for pose control of 3D modular reconfigurable robots. The robots operate in liquid environments, and move by routing fluid through themselves. Each module uses only two bits of sensory information per face. Additionally, the modules can use up to five bits of information that are exchanged via shared power lines. We prove that robots of convex shape are guaranteed to reach a goal object with a preferred orientation. Using computer simulations of Modular Hydraulic Propulsion robots, all controllers are assessed for different environments, system sizes and noise, and their performances compared against a centralized controller. Given the simplicity of the solutions, modules could be realized at scales below a millimeter-cube, where robots of high spatial resolution could perform accurate movements in 3D liquid environments.