The Multi-AMR Buffer Storage, Retrieval, and Reshuffling Problem: Exact and Heuristic Approaches
Buffer zones are essential in production systems to decouple sequential processes. As industries evolve, the need for efficient storage and retrieval systems has become increasingly critical, especially in dense floor storage environments like space-constrained brownfield facilities. Manual operation in these settings faces significant challenges due to severe labor shortages and rising operational costs. To address these issues, automating buffer zones has become a necessity, leading to the emergence of the Buffer Storage, Retrieval, and Reshuffling Problem (BSRRP).
Traditionally, previous research has focused on scenarios limited to reshuffling and retrieving a fixed set of items. However, real-world manufacturing environments require a more adaptive approach that incorporates not only the existing inventory but also accommodates arriving unit loads. In this context, the Multi-AMR BSRRP is introduced, which involves coordinating a fleet of autonomous mobile robots (AMRs) to manage concurrent reshuffling operations alongside time-windowed storage and retrieval tasks within a shared floor area.
Formulation and Methodology
The study presents a Binary Integer Programming (IP) model designed to obtain exact solutions, serving as a benchmarking tool. However, given that the BSRRP is classified as NP-hard, exact methods become computationally intractable when scaled to industrial levels. To overcome this limitation, the authors propose a hierarchical heuristic approach.
- A* Search: This component focuses on task-level sequence planning for the placement of unit loads. It effectively determines the optimal order in which tasks should be executed to maximize efficiency.
- Constraint Programming (CP): This technique is employed for multi-robot coordination and scheduling. It ensures that the actions of the robotic fleet are synchronized and optimized for the best performance within the shared space.
Results and Implications
Experimental results have demonstrated significant improvements in computation time, achieving orders-of-magnitude reductions compared to the exact formulation. These findings highlight the practicality and efficiency of the proposed heuristic approach, confirming its viability as responsive control logic for high-density production environments.
The implications of this research are profound, as they pave the way for more automated and efficient manufacturing processes. By effectively managing buffer zones through advanced robotic coordination, industries can respond better to labor shortages and operational challenges, ultimately leading to reduced costs and increased productivity.
Conclusion
The Multi-AMR BSRRP represents a significant advancement in the automation of buffer zones in production systems. By integrating exact and heuristic methodologies, this approach not only addresses current operational challenges but also sets the groundwork for future research and development in the field of industrial automation.