Slides
Physical sorting is a new kind of behavior for swarm robotics. Robots move physically to become sorted and evenly distributed in a line. Physical movement is necessary when we cannot simply swap tasks, especially for physical loads, charging robot batteries, and when it is difficult to reach consensus. I present two algorithms to solve this problem: the geometry-based version and the topology-based version. I show that the sorting problem is much more difficult than expectation when robots have limited communication range. Counterexamples are found in the straightforward geometry-based version, and the thoughtful topology-based version provides a safe, correct, and efficient solution. Simulations and experiments show how these algorithms work on low-cost multi-robot systems.