Bubble-raft inspired shape-assembly in flying robot swarm for uniform formation and obstacle traversal

Natural swarms can move cohesively while continuously reshaping their spatial shape, yet reproducing this behavior with large flying robot swarms in obstacle environments remains difficult, especially in achieving uniformity and safety. Here, we present a distributed 3D shape-assembly controller for flying robot swarms that forms arbitrary target shapes with uniform coverage and safe inter-robot distance. Inspired by bubble-rafts, each robot is associated with a non-overlapping region inside the target shape and updates its velocity by considering region exploration, region balancing and distance fine-tuning. The proposed region-based shape-assembly method is able to drive the swarm toward uniform formations and enable fast shape transformation, as well as resilience to robot joining and failure. For navigation, we design a lightweight velocity-obstacle mechanism that adjusts the nominal shape-assembly velocity to collision-free commands with minimal formation disruption. We validate the proposed methods in extensive simulations and real-world swarm experiments, demonstrating efficient formation of complex 3D shapes, robust maintenance of safety distances, and reliable obstacle traversal.