Response time analysis of a live-cube compact storage system with two storage classes

We study a next generation of storage systems: live-cube compact storage systems. These systems are becoming increasingly popular, due to their small physical and environmental footprint paired with a large storage space. At each level of a live-cube system, multiple shuttles take care of the moveme...

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Bibliographic Details
Published inIIE transactions Vol. 49; no. 5; pp. 461 - 480
Main Authors Zaerpour, Nima, Yu, Yugang, de Koster, René B. M.
Format Journal Article
LanguageEnglish
Published Abingdon Taylor & Francis 04.05.2017
Taylor & Francis Ltd
Subjects
Closed form solutions
Exact solutions
live-cube compact storage system
Logistics
material handling
Mathematical analysis
Response time
Response time (computers)
response time analysis
Retrieval
Space shuttles
Storage systems
two-class-based storage policy
Unit loads
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Summary:We study a next generation of storage systems: live-cube compact storage systems. These systems are becoming increasingly popular, due to their small physical and environmental footprint paired with a large storage space. At each level of a live-cube system, multiple shuttles take care of the movement of unit loads in the x and y directions. When multiple empty locations are available, the shuttles can cooperate to create a virtual aisle for the retrieval of a desired unit load. A lift takes care of the movement across different levels in the z-direction. Two-class-based storage, in which high turnover unit loads are stored at storage locations closer to the Input/Output point, can result in a short response time. We study two-class-based storage for a live-cube system and derive closed-form formulas for the expected retrieval time. Although the system needs to be decomposed into several cases and sub-cases, we eventually obtain simple-to-use closed-form formulas to evaluate the performance of systems with any configuration and first zone boundary. Continuous-space closed-form formulas are shown to be very close to the results obtained for discrete-space live-cube systems. The numerical results show that two-class-based storage can reduce the average response time of a live-cube system by up to 55% compared with random storage for the instances tested.
ISSN:2472-5854
2472-5862
DOI:10.1080/24725854.2016.1273563