Operating a large fleet of mobile robots using the plan-merging paradigm

We present and discuss the use of a generic scheme for multi-robot cooperation called the "plan-merging paradigm" for managing a large fleet of autonomous mobile robots. Each robot, autonomously and incrementally builds and executes its own plans taking into account the multi-robot context obtained by collecting the current plans and goals of the other robots. We describe the overall system architecture and discuss the properties of our cooperative scheme. We show how the plan-merging paradigm (PMP) can be used in a hierarchical manner and how it "fills the gap" between centralized planning and distributed execution. We finally illustrate this scheme through an implemented system which allows a fleet of autonomous mobile robots to perform load transfer tasks in a route network environment. The central activity is limited to task allocation and important gains are obtained in system flexibility and robustness to execution contingencies. Simulations (using up to 30 robots) as well as experiments with real robots (3) are presented and discussed.