Self-reconfiguring modular robotic boats.

Self-reconfiguring aquatic robots offer promise for a wide range of marine applications, including building temporary infrastructure, remote maintenance and search-and-rescue operations, environmental monitoring, and on-demand transportation. However, achieving autonomous water-based self-reconfiguration, even in two dimensions on the water surface, remains challenging, due to complex nonlinear hydrodynamics, disturbances from self-motion and neighboring robots, as well as external environmental factors. Here, we present the FloatForm platform, a group of miniature modular robotic boats capable of self-assembling into physically connected structures, self-reconfiguring, and collectively traveling as larger assemblies via a hybrid coordination framework. Each robot unit is equipped with onboard sensing, motion control, and the ability to coordinate and physically connect with its neighbors. We demonstrate the feasibility of aquatic self-reconfiguration via hybrid coordination, where distributed controllers on each robot handle coordination tasks such as aggregating into desired shapes and avoiding collisions, while a minimalist central planner oversees the overall success of each task and fixes final imperfections. This work advances the design, control, and coordination of modular robotic systems in aquatic environments, enabling flexible, robust, and scalable applications on the water.