Abstract

This paper presents a method for determining the performance of shuttle-based storage and retrieval systems (SBS/RS) with tier-captive, single-aisle shuttles serving various numbers of tiers of multiple-deep storage. The use of this approach takes place in the design process of SBS/RS. The proposed approach considers the real operating characteristics of the shuttle and lifts. The basis of this calculation method is a continuous-time, open-queueing system with limited capacity. The cycle times of the lifts and shuttles, determined by a spatial value approach, can be used directly in the presented method with an assumed uniform distribution of storage locations and a probability-based model of storage depth. This approach is validated by a comparison with a discrete-event simulation. Finally, an example based on a system provided by a European material handling provider is presented to outline how this calculation model can be used for designing SBS/RS that fulfill predefined requirements. The result of this example is a decrease in the needed ground space with an increasing number of tiers served by each shuttle and with increasing storage depth.

Highlights

  • Technological developments in the global supply chain have increased the requirements for physical storage technology

  • The aim of this paper is to provide a decision tool that accurately and quickly evaluates the throughput of shuttle-based storage and retrieval systems (SBS/RS) with shuttles serving multiple tiers of multiple-deep storage

  • The system investigated in this paper is a tier-captive, single-aisle SBS/RS with multiple-deep storage and shuttles serving multiple tiers

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Summary

Introduction

Technological developments in the global supply chain have increased the requirements for physical storage technology. The usage of the approach is mainly for material handling providers who design new systems at given requirements such as storage capacity, throughput, length, and height. Using this calculation, it is possible to define a system that meets the requirements. The parameters for this numerical study are based on a system provided by a European material handling provider. A comparison of different numbers of tiers per shuttle and different rack depths follows, with a performance measurement of each

Literature review
System description
Analytical approach
Interarrival time
Service time
Mean time needed to transfer the pallet to and from the shuttle
Probability of relocation
Mean ride time necessary in the relocation cycle
Mean time needed in the relocation cycle
Numerical study
Numerical evaluation of approximation quality
Optimization example
Findings
Conclusion
Full Text
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