RS-ModCubes: Self-Reconfigurable, Scalable, Modular Cubic Robots for Underwater Operations

This paper introduces a reconfigurable underwater robot system, RS-ModCubes, which allows scalable multi-robot configurations. An RS-ModCubes system comprises multiple ModCube modules, that can travel underwater with 6 DoFs and assemble with each other into a larger structure with onboard electromagnets. This system is designed to explore the feasibility of modularity and reconfigurability in underwater robotics, eliminating the need to customize mechanical designs for a specific task. We develop a modeling framework for reconfigurable robot systems, incorporating hydrodynamic effects via Monte Carlo approximation. A model-based feedforward Proportional Derivative (PD) controller serves as the baseline for control. Inspired by dexterous manipulation, we evaluated the robot's maximum task wrench space and power efficiency, compared against four commercial underwater robots. RS-ModCubes is validated via both real-world experiments and simulations, including individual and multi-module trajectory tracking and hovering docking.