Lifelong Multi-Subsystem Pickup and Delivery with Buffer-Limited Handover Stations

2026-07-20

AI Summary

This study addresses the challenges of congestion and starvation arising from single-berth, limited-buffer handover stations in lifelong multi-subsystem pickup-and-delivery tasks. To this end, it formally introduces the Multi-Subsystem Multi-Agent Pickup and Delivery with Bounded Handover Stations (MS-MAPD-BHS) problem and proposes the Handover-Aware Reservation and Routing (HARR) online controller. HARR enables coupled path planning and conflict-free berth scheduling across subsystems by leveraging a shared berth reservation calendar and deterministic receding-horizon predictions of buffer occupancy, thereby guaranteeing both execution completeness and buffer safety. Experimental results demonstrate that, compared to fixed-berth baselines, HARR achieves up to a 77% increase in throughput and a 92% reduction in backlog under moderate workloads, while also exhibiting superior planning efficiency over coupled token-passing approaches.

Abstract

Coordinating payload transfers between subsystems is a critical challenge in lifelong Multi-Agent Pickup and Delivery (MAPD). We study systems where agents are confined to separate regions and must exchange payloads through shared handover stations. These stations, equipped with single docks and finite buffers, are inherently vulnerable to blocking and starvation. We formalize this problem as Multi-Subsystem MAPD with Buffer-limited Handover Stations (MS-MAPD-BHS). We then propose Handover-Aware Reservation and Routing (HARR), an online controller that couples per-subsystem planners. HARR uses a shared dock reservation calendar and a deterministic rolling-horizon projection of buffer occupancy to coordinate actions. A candidate route is accepted only if its dock interval is free and the resulting buffer occupancy projection remains within capacity. Under perfect execution, these checks ensure collision-free dock use and buffer-safe committed operations within the reservation horizon. In simulation, HARR achieves up to 77% higher throughput and 92% lower backlog than a fixed-dock ablation at moderate load, while also reducing planning time relative to a coupled station-aware Token Passing baseline. These results show that explicit interface coordination substantially improves stability in modular multi-subsystem transport.

Problem

• Multi-Agent Pickup and Delivery
• Handover Stations
• Buffer Limitation
• Subsystem Coordination
• Lifelong Planning

Innovation

• Handover-Aware Reservation and Routing
• Buffer-limited Handover Stations
• Multi-Subsystem MAPD
• Rolling-horizon Buffer Projection
• Dock Reservation Calendar