Planning coordination and execution in multi-robots environment

We present and discuss a generic cooperative scheme for multi-robot cooperation based on an incremental and distributed plan-merging process. Each robot, autonomously and incrementally builds and executes its own plans taking into account the multi-robot context. The robots are assumed to be able to collect the other robots current plans and goals and to produce plans which satisfy a set of constraints that are discussed. We discuss the properties of this cooperative scheme (coherence, detection of dead-lock situations) as well as the class of applications for which it is well suited. We show how this paradigm can be used in a hierarchical manner, and in contexts where planning is performed in parallel with plan execution. We also discuss the possibility to negotiate goals within this framework and how this paradigm "fills the gap" between centralised 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 with a very limited centralised activity and important gains in system flexibility and robustness to execution contingencies.