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1.
Analytical model and swapping policy assessment of a vertical lift module – buffer integrated storage system
Jakob Marolt, Fabio Sgarbossa, Jesus A. Jimenez, Abhimanyu Sharotry, Tone Lerher, 2024, original scientific article

Abstract: To meet the rising demands of global trade and e-commerce, efficient warehousing relies on inte-grated and cooperative material handling systems. This paper investigates the extension of VerticalLift Module (VLM) storage capability with a Buffer System and assesses the impact of this integra-tion on performance. We developed an analytical model to calculate the expected dual commandcycles, forming the basis for evaluating the VLM – Buffer integrated storage system’s performance.Our research emphasises minimising unnecessary swaps between the VLM and the Buffer Systemto enhance throughput performance. We introduce the Look Ahead Strategy (LAS) to minimiseinter-system swaps and develop a Binary Integer Program (BIP) to benchmark its performance. Theresults indicate that LAS performs on par with BIP, due to its ability to consider product popular-ity during the final selection of the outbound swapping tote. Through a comprehensive analysisof the analytical model with an empirical correction, utilising Pareto-based order sequences, theresults show deviations of less than 1% on average, affirming the analytical model’s accuracy. Ourresearch provides insights on using the VLM-Buffer integrated storage system, emphasising efficienttote swapping policies like LAS for enhanced warehouse operations, and allows managers to assesssystem performance through scenario-based analyses.
Keywords: automated warehouses, vertical lift module, toteswapping, analytical and numerical modelling, performance evaluation
Published in DKUM: 11.10.2024; Views: 0; Downloads: 1
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2.
A new sustainable warehouse management approach for workforce and activities scheduling
Vlado Popović, Milorad J. Kilibarda, Milan Andrejić, Borut Jereb, Dejan Dragan, 2021, original scientific article

Abstract: Sustainable engineering is very important for logistics systems. Nowadays, sustainable warehouse management is a key factor in market success. Workforce fluctuation and inverting the number of customers' demands make a lot of problems in distribution warehouses. This study addresses a sustainable approach for the workforce scheduling problem recognized in a real distribution warehouse. The problem arises from the high variability of demand for workers over oneworkday, which causes workforce surplus in some periods of the workday and shortages in others. Engineering managers of the distribution warehouse already use different full-time and part-timeshifts, and schedule workers on different activities, but they still have significant workforce surplusesor shortages in some periods. This study proposes the scheduling of activities' execution together with workers to face that variability and decrease the cost of the workforce. This idea comes from the fact that some activities in a distribution warehouse can be done in a specific time period after the need for them occurs. In this way, the variability of demand for workers can be decreased, and alower workforce cost may be ensured. Based on this idea, the entire problem is modeled as integer linear programming. The real example of the problem is solved, and the proposed model is tested on randomly generated instances of the problem in Python by means of the PuLP linear programming package. The results indicate different positive effects in the manner of sustainable warehouse management: lower workforce costs, time savings, better utilization of all types of resources andequipment, increased employee satisfaction, and so on. For even 61% of instances of the introduced problem, the obtained cost of the workforce is lower by more than 20% if activities' executions arescheduled together with employees.
Keywords: workforce, activities planning, schedule, optimization, warehouses, sustainable warehouse management, logistics
Published in DKUM: 11.10.2024; Views: 0; Downloads: 5
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3.
Advanced technologies in logistics engineering : automated storage systems with shuttles integrated with hoisted carriage
Tone Lerher, Primož Bencak, 2022, original scientific article

Abstract: This paper presents automated storage systems with shuttles integrated with hoisted carriage for successful application in intralogistics. The first part of the paper presents classic and advanced AVS/RS along with specific intralogistics automation systems known as AutoStore from Swisslog and Skypod from Exotec. The second part of the paper focuses on an advanced system with shuttle vehicles capable of serving multiple tiers of the storage rack. An analytical model for the shuttle vehicles capable of serving multiple tiers of the storage rack is presented, which is based on (i) the sequences of acceleration, constant velocity and deceleration, and (ii) randomised assignment policy. Based on the presented model, the expected Single Command (SC) and Dual Command (DC) travel (cycle) time as well as the throughput performance of the shuttle vehicles capable of serving several tiers of warehouse, could be calculated. A programme code in MATLAB has been presented for the computation of throughput performances of automated storage systems with shuttles integrated with hoisted carriage capable of serving several tiers of the storage rack.
Keywords: analytical and numerical model, automated vehicle-storage and retrieval systems AVS/RS, automated warehouses, cycle time and throughput performance, shuttles integrated with hoisted carriage
Published in DKUM: 26.06.2024; Views: 162; Downloads: 16
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4.
A Comparison of Traditional and Modern Data Warehouse Architectures : zaključno delo
Rok Virant, 2021, undergraduate thesis

Abstract: Data has never been as desired or valued as it is today. The value of data and information over the past decade has not only changed trends in business and the IT industry but has also changed the dynamic of work. Enormous amounts of aggregate data offer companies and other corporations the option to explore and study data samples. Data collection and information processing are new dynamic factors, not only for individuals but also for corporations. Companies and corporations who are able to process large amounts of data in the shortest possible time can place themselves in a leading position in certain professions. In this bachelor’s thesis we will describe the basic concepts and factors that have shaped new, cloud-based data warehouse technologies. At the same time, we also emphasize why and how these technologies are used. We focus on how the changing technology influenced the users and their consumption of data, the changing dynamics of work as well as the changes of data itself. In the practical part, we created two DWH environments (on-premises and cloud) that we compare with each other. In the experiment, we underlined the fact that CDWHs are in certain situations not always faster than TDWH.
Keywords: Data Warehouses, Cloud Computing, Outsourcing, Data, Information
Published in DKUM: 18.10.2021; Views: 1121; Downloads: 179
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5.
Method for evaluating the throughput performance of shuttle based storage and retrieval systems
Tone Lerher, Banu Y. Ekren, Zaki Sari, Bojan Rosi, 2016, original scientific article

Abstract: In this paper a method for throughput performance calculation of shuttle based storage and retrieval systems (SBS/RS) is presented. SBS/RS represent a new technology in automated storage and retrieval systems. Since it is important to design SBS/RS right the first time due to the relative inflexibility of the physical layout, we provide a proposed method for the throughput performance calculation of these systems. The performance of the system is considered as a throughput capacity of the SBS/RS as a whole.
Keywords: automated warehouses, performance analysis, shuttle based systems, storage, logistics
Published in DKUM: 12.07.2017; Views: 1480; Downloads: 457
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6.
Multi-objective optimization of automated storage and retrieval systems
Tone Lerher, Matjaž Šraml, Matej Borovinšek, Iztok Potrč, 2013, original scientific article

Abstract: The multi-objective optimization of automated warehouse is discussed and evaluated in present paper. Since most of researchers in material handling community had performed optimization of decision variables with single objective function only (usually named with minimum travel time, maximum throughput capacity, minimum cost, etc.), the multi-objective optimization (time-cost-quality) will be presented in present research. For the optimization of decision variables in objective functions, the method with genetic algorithms is used. The main objective of our contribution is to determine the performance of the system according to the multi-objective optimization technique.
Keywords: automated warehouses, performance, multi-objective function, optimization
Published in DKUM: 10.07.2015; Views: 1133; Downloads: 70
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7.
A multi-objective optimization approach for designing automated warehouses
Tone Lerher, Matej Borovinšek, Iztok Potrč, Matjaž Šraml, 2012, published scientific conference contribution

Abstract: A multi objective optimization of automated warehouses is discussed and evaluated in present paper. Since most of researchers in material handling community had performed optimization of decision variables with single objective function only (usually named with minimum travel time, maximum throughput capacity, minimum cost, etc.), the multi objective optimization (travel time - cost - quality) will be presented. For the optimization of decision variables in objective functions, the method with genetic algorithms is used. To find the Pareto optimal solutions, the NSGA II genetic algorithm was used. The main objective of our contribution is to determine the performance of the system according to the multi objective optimization technique. The results of the proposed model could be useful tool for the warehouse designer in the early stage of warehouse design.
Keywords: automated warehouses, material handling, multi objective optimization
Published in DKUM: 10.07.2015; Views: 1331; Downloads: 34
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