We describe a high-density storage system for physical goods in which identical conveyor modules can be plugged together to store and retrieve unit-loads or small containers. Material movement conforms to the "puzzle architecture" found in popular board games such as the 15-puzzle and Rush Hour. Control of the system is decentralized, meaning that each module contains identical operating logic that directs its behavior based on local conditions and message passing. We prove the system deadlock-free and show its performance under a wide variety of operating configurations.Note to Practitioners-One of the obstacles to widespread adoption of automated material handling systems is inflexibility: once a system is designed and installed, making changes to its configuration is typically very difficult. The GridStore system overcomes this obstacle for high-density storage systems by implementing decentralized control, meaning that each conveyor module in a Grid-Store system has its own, independent controller. One implication of decentralized control is that the system can be expanded or reconfigured rapidly, and without rewiring or reprogramming. Applications of this system could range from small, desktop systems to large, container-handling systems.
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