An approach for performance evaluation of SBS/RS with shuttle vehicles serving multiple tiers of multiple-deep storage rack

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.

Shuttle-Based Storage and Retrieval System: A Literature Review

“…The results show that the double-deep system does have better performance in some cases. Eder [14] proposed a multi-deep and multi-tier SBS/RS. The system saves floor space due to multi-deep storage.…”

“…System Depth [6] SBS/RS Double-deep [14] SBS/RS Multi-deep [15] AVS/RS Multi-deep [16] AVS/RS Multi-deep…”

Hybrid model for the design of a deep-lane multisatellite AVS/RS

“…This is a strong initial assumption. Eder overcame this assumption in their recent studies [15,21,22] by modeling the SBS/RS with a continuous open queuing system with limited capacity. Recently, Kumawat and Roy [23] illustrated an original method for solving multistage SOQNs and validated it using a case study on a multitier shuttle-based compact storage system.…”

“…Consequently, a model that estimates system performance must consider all tiers and not a single-tier configuration. Most studies related to AVS/RS estimate system performance considering a single-tier system [7] or simply by multiplying the performance of a single tier by the number of tiers in the system [15,21,22].…”

“…Most studies on AVS/ RS simplify the system transactions by defining a single vehicle per tier, representing both the shuttle and the satellite. In particular, [15,21,22] Eder recently considered the shuttle and satellite as a single vehicle and linked the number of vehicles to the number of tiers. Thus, Lerher [26] studied double-deep AVS/RS considering a single vehicle, called a shuttle carrier, to perform the task along the cross-aisle and within the lanes.…”