Browsing by Author "Lerher, Tone"

Now showing 1 - 9 of 9

Citation - WoS: 60
Citation - Scopus: 69
A tool for time variance and energy related performance estimations in a shuttle-based storage and retrieval system
(Elsevier Inc. usjcs@elsevier.com, 2018) Banu Yetkin Yetkin Ekren; Anıl Akpunar; Zaki Sari; Tone Lerher; Akpunar, Anil; Lerher, Tone; Ekren, Banu Y.; Sari, Zaki
The aim of this study is to present a tool that can calculate critical performance measures of different Shuttle-Based Storage and Retrieval System (SBS/RS) designs. Specifically our aim is to develop an analytical model-based tool that can estimate the mean and variance of travel time of lifts and shuttles as well as the mean amount of energy consumption and energy regeneration per transaction for a pre-defined SBS/RS design. The methodology illustrated in this paper can also be utilized for any system having a straight discrete travel pattern with equal distance stop points. We are motivated in this study by a relatively new automated storage and retrieval technology SBS/RS. By the provided tool one can evaluate these systems’ performance promptly by changing the input design parameters (e.g. discrete travel lengths velocity of vehicles acceleration/deceleration of vehicles number of tiers number of bays etc.) of these systems. The analytical models used in the tool are verified via simulation for several SBS/RS design scenarios. As a result it is found that the proposed tool produces highly accurate results specifically less than 1% Absolute Percentage Error from the simulation results. © 2018 Elsevier B.V. All rights reserved.
Aisle-to-aisle design for SBS/RS under smart deadlock control policies
(IEOM Society, 2021) Ecem Eroğlu Turhanlar; Banu Yetkin Yetkin Ekren; Tone Lerher; Lerher, Tone; Turhanlar, Ecem Eroglu; Ekren, Banu Yetkin
Recent increase in e-commerce warehouse operations have become one of the most significant issues. Recent customer profile requests fast delivery time with flexible options in purchasing. Automated warehousing technologies are widely utilized in warehouses to provide fast solutions for those demand profiles. Shuttle-based storage and retrieval system (SBS/RS) is an automated warehousing technology assuring fast transaction process in warehouses. In this work we study a special design for SBS/RS where automated vehicles (i.e. shuttles) are more flexible in their travel pattern so that the system would not require a dedicated shuttle in each tier resulting with decreased number of shuttles compared to a dedicated one (i.e. each zone with a single shuttle) in the system. We compare these two system designs flexible and dedicated ones by using an agent-based simulation modelling approach. The proposed flexible design is developed on deadlock and collision prevention algorithms evaluating real time information. The performance of the system is compared by their average flow time per transaction maximum flow time of a transaction throughput rate and utilization of shuttles etc. The results show that by integrating smart collision and deadlock prevention algorithms the proposed flexible aisle-to-aisle SBS/RS works better than the dedicated system design. © 2021 Elsevier B.V. All rights reserved.
Citation - WoS: 21
Citation - Scopus: 26
Autonomous mobile robot travel under deadlock and collision prevention algorithms by agent-based modelling in warehouses
(TAYLOR & FRANCIS LTD, 2024) Ecem Eroglu Turhanlar; Banu Y. Ekren; Tone Lerher; Lerher, Tone; Turhanlar, Ecem Eroglu; Ekren, Banu Y.
Recent dramatic increase in e-commerce has also increased the adoption of automation technologies in warehouses. Autonomous mobile robots (AMRs) are from those technologies widely utilized in warehouse operations. It is important to design the operation of those robotic systems in such a way that they meet the current and future system requirements correctly. In this paper we study flexible travel of AMRs in warehouses by developing smart deadlock and collision prevention algorithms on agent-based modelling. By that AMR agents can interact with each other and environment so that they can make smart decisions maximizing their goals. We compare the performance of the developed flexible travel system with non-flexible designs where there is a single AMR dedicated to a specific zone so that no deadlock or collision possibility takes place. The results show that AMRs may provide up to 39% improvement in the flexible system compared to its non-flexible design.
Citation - WoS: 36
Citation - Scopus: 43
Cost and performance comparison for tier-captive and tier-to-tier SBS/RS warehouse configurations
(Blackwell Publishing Ltd, 2021) Melis Küçükyaşar; Banu Yetkin Yetkin Ekren; Tone Lerher; Y. Ekren, Banu; Küçükyaşar, Melis; Lerher, Tone; Ekren, Banu Y.
This paper compares two shuttle-based storage and retrieval system (SBS/RS) configurations developed on travel policy of shuttles in the systems. Specifically we compare two system configurations of SBS/RS: SBS/RS with tier-captive shuttles and SBS/RS with tier-to-tier shuttles. In a tier-captive SBS/RS warehouse design there is a dedicated shuttle in each tier that cannot travel between tiers. Due to a large number of shuttles in such a configuration lifts are always bottlenecks and the utilizations of shuttles are very low. In this study we propose an alternative SBS/RS design with tier-to-tier shuttles in which shuttles can travel between tiers by using a separate lifting mechanism dedicated for them. The advantage of this design would be reduction in investment cost due to the decreased number as well as higher utilizations of shuttles in the system. The two configurations were compared on the following performance metrics: initial investment costs throughput rates per hour and average energy consumption per transaction when there is a regeneration mechanism in the system. In a tier-to-tier SBS/RS design allowing shuttles to travel between tiers increases operational complexity of the system. Thus we simulate the two system designs and compare their performance metrics by conducting several rack design experiments based on the number of aisles tiers and bays. The results of this study suggest that there may be a better configuration in terms of total investment cost and throughput rate in a newly proposed tier-to-tier SBS/RS design that could be considered as an alternative to a tier-captive SBS/RS design. © 2021 Elsevier B.V. All rights reserved.
Citation - WoS: 12
Citation - Scopus: 10
Cost and performance comparison of tier-captive SBS/RS with a novel AVS/RS/ML
(Taylor and Francis Ltd., 2024) Banu Yetkin Yetkin Ekren; Tone Lerher; Melis Küçükyaşar; Boris Jerman; Yetkin Ekren, Banu; Jerman, Boris; Lerher, Tone; Küçükyaşar, Melis; Ekren, Banu Yetkin
This paper introduces a novel autonomous vehicle-based storage and retrieval system that utilizes movable lifts (AVS/RS/ML) proposed as an alternative to the tier-captive shuttle-based storage and retrieval system (SBS/RS). The newly proposed system aims to provide an affordable solution with highly utilised AGVs that can also perform operations out of warehouse. The performance of this novel system is compared with the equivalent tier-captive SBS/RS warehouse design where each shuttle is dedicated in a specific tier in that design. The comparison is based on the initial system investments costs throughput rates and average utilisation of lifts/MLs in the system. Collision prevention rules are also applied to AVS/RS/ML and its performance is tested through simulation. The results show that the tier-captive SBS/SR system becomes cost-efficient under high throughput rate requirements while the AVS/RS/ML technology is preferred for relatively moderate and low process rate requirements. The unit-cost per month performance metric of AVS/RS/ML is less sensitive to an increase in number of tiers in the system compared to the tier-captive SBS/RS case indicating that AVS/RS/ML may be promising for high-tier warehouse system designs. © 2024 Elsevier B.V. All rights reserved.
Citation - Scopus: 1
Design and Operation of Singleand Multi-deep Shuttle-Based Storage and Retrieval Systems (SBS/RS)
(Springer International Publishing, 2024) Tone Lerher; Jakob Marolt; Fabio Sgarbossa; Banu Yetkin Yetkin Ekren; Goran Dukic; Marolt, Jakob; Sgarbossa, Fabio; Dukic, Goran; Lerher, Tone; Ekren, Banu Y.
With the rapid growth of e-commerce practices the efficient management of warehouses and fulfilment centres has become crucial in supply chain operations. One effective strategy for achieving this efficiency is the digital transformation of warehouses through automation. In particular shuttle-based storage and retrieval systems (SBS/RS) have gained significant attention due to their ultra-high transaction process capability. However ongoing research focuses on enhancing the operating performance and cost efficiency of these SBS/RS designs. This chapter presents mathematical modelling approaches for estimating the performance of single- and multi-deep SBS/RS designs. These models provide valuable insights for designing warehouses that optimize transaction process rates while ensuring a balanced utilization of elevators and shuttles in the system tailored to meet the specific requirements of the warehouse. By leveraging these modelling techniques warehouse managers can make informed decisions regarding the design and configuration of SBS/RSs to improve overall operational efficiency and productivity. © 2025 Elsevier B.V. All rights reserved.
Citation - Scopus: 5
Energy efficient automated warehouse design
(Elsevier, 2020) Melis Küçükyaşar; Banu Yetkin Yetkin Ekren; Tone Lerher; Küçükyaşar, Melis; Lerher, Tone; Ekren, Banu Yetkin
The aim of this work is to study an automated warehousing system design to optimize significant performance metrics: energy and travel time related performance metrics in the system. Different from the literature we study a specific design of a well-known automated warehousing system shuttle-based storage and retrieval system (SBS/RS) in which shuttles can travel between tiers by using a lifting mechanism installed at periphery of racks. In a traditional SBS/RS design shuttles are dedicated in each tier that is tier-captive. They perform horizontal travel for storage and retrieval of loads within a tier of an aisle. There is a single lifting mechanism in each aisle for vertical travel of loads. These systems are mostly utilized in large distribution centers to obtain high transaction rate for storage and retrieval processes. In a traditional design because there is a dedicated shuttle in each tier of an aisle and a single lifting mechanism in each aisle lifts are mostly bottleneck and the utilization of shuttles are very low. Hence a new design with a few numbers of shuttles that can travel between tiers might be promising in decreasing the initial investment cost and increasing the utilization levels of shuttles. In this work we explore an optimal warehouse design for that new SBS/RS concept—tier-to-tier SBS/RS—in terms of number of shuttles number of tiers aisles acceleration/deceleration values of lifts/shuttles etc. to improve some significant performance metrics from the system (e.g. energy consumption and cycle time per transaction). © 2022 Elsevier B.V. All rights reserved.
Citation - Scopus: 11
Energy efficient design of autonomous vehicle based storage and retrieval system
(Institut za Istrazivanja, 2017) Anıl Akpunar; Banu Yetkin Yetkin Ekren; Tone Lerher; Yetkin Ekren, Banu; Akpunar, Anil; Lerher, Tone
Autonomous warehousing is moving beyond traditional crane-based AS/RS technologies on the way to autonomous vehicle (AV) based AS/RS (AVS/RS) technologies. AVS/RS proposes substantial flexibility with respect to throughput capacity in the transfer of unit loads in high density storage areas due to having opportunity in changing the number of AVs in the system. Because of recent trend in ecological concern an efficient AVS/RS warehouse design should not only consider minimization of cycle time of a transaction to process but also consider the minimization of energy consumption in the system. In this study we explore energy minimum AVS/RS warehouse design providing maximum utilization of resources in the system. We consider rack design in terms of number of aisles tiers and bays as well as number of AVs as decision variables in the design and energy minimization as objective function. We completed 81 simulation experiments for different levels of those decision variables and provide the results via a histogram graph. © 2023 Elsevier B.V. All rights reserved.
Citation - WoS: 24
Citation - Scopus: 28
Simulation-Based Performance Analysis for a Novel AVS/RS Technology with Movable Lifts
(MDPI, 2021) Boris Jerman; Banu Yetkin Ekren; Melis Kucukyasar; Tone Lerher; Jerman, Boris; Kucukyasar, Melis; Lerher, Tone; Ekren, Banu Yetkin
This paper studies a novel autonomous vehicle-based storage and retrieval system (AVS/RS) design with movable lifts (AVS/RS/ML). In the proposed system there are aisle-captive lifts that are able to travel along the warehouse aisle to position themselves at the target column location. Those lifts can lift up/down the autonomous vehicles to/from the target storage compartment when they are in standstill. This novel design is proposed as an alternative to existing AVS/RSs to balance the resource utilizations as well as to provide an inexpensive solution with highly utilized autonomous vehicles (i.e. AGVs). As an initial work for this novel system two alternative operating designs under different racking configurations are experimented. We compare those two designs by their throughput rate performance metrics under the arrival rate scenarios with highly utilized AGVs (i.e. 95%). Besides we experiment with two warehouse capacity scenarios: 900 and 1800 storage compartments. The results show that designs with two separate I/O point locations provide a better throughput rate than designs with single I/O point location. Besides a decreased number of columns in the system improves the system's performance.