The impact of batch retrievals on throughput performance of a carousel system serviced by a storage and retrieval machine

A carousel system is an example of an automated storage and retrieval system that is used in distribution centers and manufacturing facilities. We analyze the impact batch retrieval processing has on throughput performance for horizontal carousel systems that use automated storage and retrieval machines as robotic pickers. By developing an analytical cycle-time model we provide the theoretical base necessary to support the management decision of whether to batch or not. We conduct a computational experiment to test the accuracy of our analytical model, to demonstrate how our approach can guide management decisions, and to illustrate the throughput improvements that can be realized through the use of a batch policy. Testing indicates that batch processing increases carousel throughput performance over sequential processing. For the instances tested, batch processing resulted in an average decrease in cycle time over sequential sequencing of 20%. Our results indicate that with batch retrievals, adding to the carousel's length increases storage capacity with a negligible impact on the carousel's throughput performance. (C) 2012 Elsevier B.V. All rights reserved.