Space system formation planning and scheduling: a distributed approach

A multi-agent distributed architecture for autonomous planning and scheduling tasks of a space system formation is here proposed. Each physical element of the team is represented as an independent unit, with its own knowledge base, its own resources and its operational skills. High-level goals asking for single/ multiple units coordinated intervention can be dealt with. The pre/post-conditions consistent net definition to accomplish the distributed planning task is accomplished thanks to a partial ordered planning algorithm. A temporal net formalism is chosen to cope with the distributed scheduling problem: the intra/inter agents´ temporal consistency is gained by applying an all shortest paths algorithm. No instantiation is asked for solving the distributed net, to preserve robustness of the scheduling according to possible external uncertainties and system failures. As no leader exists, local and shared resource consistency is acquired thanks to iterative negotiation processes among agents for the best compromise selection devoted to lower the conflicts occurrence. Two negotiation strategies are presented, to emphasize either the team welfare or the single agent welfare respectively. The communication protocol is based on the innovation of the communication oriented graph concept. The proposed architecture is here applied to a rovers scenario devoted to planetary exploration. Simulations show the validity of the proposed approach to assure multiple and robust final allocations