Impact of class-based storage, sequencing of retrieval requests and warehouse reorganisation on throughput of shuttle-based storage and retrieval systems

Abstract

Shuttle-based storage and retrieval systems (SBS/RS) are an important part of automated warehouses. SBS/RS are often used if throughput demand is high. SBS/RS can have significant advantages compared to crane-based automated storage and retrieval systems (AS/RS) with regard to throughput, energy efficiency and flexibility, depending on the application. Therefore, in the last ten years, the market for SBS/RS has grown considerably. Research of SBS/RS has not been as thorough as in the case of AS/RS. In particular, the development and investigation of the storage management policies class-based storage, sequencing of retrieval requests and warehouse reorganization and the resulting throughput increases and reductions in energy consumption during their application have considerable potential. This paper demonstrates the potential for throughput improvement in the application of these storage management policies. A simulation model is used to determine the throughput. The results show that significant optimization of the throughput is achieved by the application of the presented storage management policies.

An approach for a performance calculation of shuttle-based storage and retrieval systems with multiple-deep storage

“…One way is to use a discrete event simulation (DES) to evaluate the performance of the systems. Various publications by, e.g., Ekren et al [6,7], Marchet et al [24], Trummer et al [27], Lerher et al [16,17,[19][20][21] , Kriehn et al [13], and Ha et al [10] treat this. Literature discussing that will not be treated in this paper in more detail because of its diverging aims to this publication.…”

“…The system that is investigated in this paper is a tier-captive single-aisle SBS/RS for double-deep storage, as shown in [23] Tier-captive SCC OQN (yes) Single-deep Ekren et al [7] Tier-captive SCC/DCC SIM Single-deep Lerher et al [21] Tier-captive SCC/DCC SIM Single-deep Marchet et al [24] Tier-captive SCC SIM Single-deep Lerher [14] Tier-captive SCC/DCC CTM (no) Single-deep Sari et al [25] Tier-captive SCC/DCC CTM (yes) Single-deep Kartnig et al [12] Tier-captive DCC SQ (yes) Single-deep Trummer et al [27] Tier-captive SCC/DCC SIM Single-deep Lerher et al [18] Tier-captive SCC/DCC CTM (no) Single-deep Lerher et al [20] Tier-captive DCC SIM Single-deep Ekren et al [6] Tier-captive DCC SIM Single-deep Wang et al [29] Tier-captive SCC/DCC OQN (no) Single-deep Lerher [15] Tier-captive SCC/DCC CTM (yes) Double-deep Eder et al [4] Tier-captive SCC/DCC SQLC (yes) Single-deep Eder et al [3] Tier-captive SCC/DCC SQLC (yes) Double-deep Lerher et al [22] Tier-captive SCC/DCC CTM (no) Single-deep Lerher et al [17] Tier-captive SCC/DCC SIM Single-deep Lerher et al [19] Tier-captive SCC/DCC SIM Single-deep Borovinšek et al [1] Tier-captive SCC/DCC CTM (no) Single-deep Ekren et al [8] Tier-captive SCC/DCC OQN (yes) Single-deep Lerher [16] Tier-captive DCC SIM Single-deep Epp et al [9] Tier-captive SCC/DCC OQN(yes) Single-deep Eder et al [5] Tier-captive SCC/DCC SQLC (yes) Single-deep Kriehn et al [13] Tier-captive SCC/DCC SIM Single-deep Ha et al [10] Tier-captive SCC SIM Single-deep Eder [2] Tier -There are different transfer times from and to the shuttle depending on the depth of the rack. -There is no difference in time between the transfer of totes to and from the lifts.…”

“…For dual command cycle, it is: (13) Another aspect that has to be changed is the time for the transfer to and from the shuttle (t t S ). This is because the time for transferring the tote to and from the shuttle depends on which storage location the tote is located in the rack slot.…”

Analytical model to estimate the performance of shuttle-based storage and retrieval systems with class-based storage policy

“…Ekren et al [6] presented an approach that treated, or rather, simulated class-based storage policies in SBS/RS. Kriehn et al [9] conducted another simulation study on the same topic in an attempt to optimize the class-based storage policy and to quantify the reachable benefit of the storage policy.…”

“…1. A lift can be seen in front [13] Tier-captive Uniform QN Single deep No Ekren et al [6] Tier-captive Class-based SIM Single deep Yes Eder et al [3] Tier-captive Uniform SQLC Double deep Yes Eder et al [4] Tier-captive Uniform SQLC Single deep Yes Schloz et al [15] Tier-captive Class-based OPT Single deep No Eder et al [5] Tier-captive Uniform SQLC Single deep Yes Kriehn et al [9] Tier-captive Class-based SIM Single deep Yes Eder [2] Tier-captive Uniform SQLC Single deep Yes of each rack for totes transport from the input/output (I/O) point to the tier and back. Basically, these I/O points are located on the first tier in front of the lifts.…”