Multi-Robot Path Deconfliction through Prioritization by Path Prospects

This work deals with the problem of planning conflict-free paths for mobile robots in cluttered environments. Since centralized, coupled planning algorithms are computationally intractable for large numbers of robots, we consider decoupled planning, in which robots plan their paths sequentially in order of priority. Choosing how to prioritize the robots is a key consideration. State-of-the-art prioritization heuristics, however, do not model the coupling between a robot's mobility and its environment. This is particularly relevant when prioritizing between robots with different degrees of mobility. In this paper, we propose a prioritization rule that can be computed online by each robot independently, and that provides consistent, conflict-free path plans. Our innovation is to formalize a robot's path prospects to reach its goal from its current location. To this end, we consider the number of homology classes of trajectories, which capture distinct prospects of paths for each robot. This measure is used as a prioritization rule, whenever any robots enter negotiation to deconflict path plans. We perform simulations with heterogeneous robot teams and compare our method to five benchmarks. Our method achieves the highest success rate, and strikes a good balance between makespan and flowtime objectives.