An evaluation of storage assignment policies for twin shuttle AS/RS

This study analyzes automated storage and retrieval systems (AS/RSs) under multi-aisle storage environment. The focus is on the choice of S/R machines, single shuttle or twin shuttle. Since a twin shuttle system is about 40% more expensive, its throughput capacity should outperform a single shuttle system by at least 40% to justify its cost. Simulation experiments suggest that twin shuttle systems are more cost-effective when the dedicated aisle rule is implemented. If I/Os are located at the same side and S/R periods overlaps, the class-based storage rule will improve the relative performance of twin shuttle systems. Our results can provide useful information to practitioners who plan to implement AS/RSs in real world applications.