Deadlock-Free Method for Multi-Agent Pickup and Delivery Problem Using Priority Inheritance with Temporary Priority

Yukita Fujitani*, Tomoki Yamauchi, Yuki Miyashita, Toshiharu Sugawara

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review


This paper proposes a control method for the multi-agent pickup and delivery problem (MAPD problem) by extending the priority inheritance with backtracking (PIBT) method to make it applicable to more general environments. PIBT is an effective algorithm that introduces a priority to each agent, and at each timestep, the agents, in descending order of priority, decide their next neighboring locations in the next timestep through communications only with the local agents. Unfortunately, PIBT is only applicable to environments that are modeled as a bi-connected area, and if it contains dead-ends, such as tree-shaped paths, PIBT may cause deadlocks. However, in the real-world environment, there are many dead-end paths to locations such as the shelves where materials are stored as well as loading/unloading locations to transportation trucks. Our proposed method enables MAPD tasks to be performed in environments with some tree-shaped paths without deadlock while preserving the PIBT feature; it does this by allowing the agents to have temporary priorities and restricting agents' movements in the trees. First, we demonstrate that agents can always reach their delivery location without deadlock. Our experiments indicate that the proposed method is very efficient, even in environments where PIBT is not applicable, by comparing them with those obtained using the well-known token passing method as a baseline.

Original languageEnglish
Pages (from-to)1552-1561
Number of pages10
JournalProcedia Computer Science
Publication statusPublished - 2022
Event26th International Conference on Knowledge-Based and Intelligent Information and Engineering Systems, KES 2022 - Verona, Italy
Duration: 2022 Sept 72022 Sept 9


  • Multi-agent systems
  • Pickup and delivery problem
  • Priority inheritance

ASJC Scopus subject areas

  • Computer Science(all)


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