Exploiting Subgraph Structure in Multi-Robot Path Planning

TL;DR

This paper introduces a novel abstraction method for multi-robot path planning that partitions maps into subgraphs, enabling more efficient planning by reducing the search space and allowing quick resolution into concrete plans.

Contribution

The paper presents a new abstraction technique using subgraph partitioning with entry and exit restrictions, improving planning efficiency and completeness in multi-robot path planning.

Findings

The proposed method is sound and complete.

It outperforms prioritised planning in certain scenarios.

Combining both methods yields better results than either alone.

Abstract

Multi-robot path planning is difficult due to the combinatorial explosion of the search space with every new robot added. Complete search of the combined state-space soon becomes intractable. In this paper we present a novel form of abstraction that allows us to plan much more efficiently. The key to this abstraction is the partitioning of the map into subgraphs of known structure with entry and exit restrictions which we can represent compactly. Planning then becomes a search in the much smaller space of subgraph configurations. Once an abstract plan is found, it can be quickly resolved into a correct (but possibly sub-optimal) concrete plan without the need for further search. We prove that this technique is sound and complete and demonstrate its practical effectiveness on a real map. A contending solution, prioritised planning, is also evaluated and shown to have similar performance albeit at the cost of completeness. The two approaches are not necessarily conflicting; we demonstrate how they can be combined into a single algorithm which outperforms either approach alone.