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Innovative approaches to wear reduction in horizontal powder screw conveyors : a design of experiments-guided numerical study
Marko Motaln, Tone Lerher, 2024, izvirni znanstveni članek

Opis: Numerical simulations play a vital role in the modern engineering industry, especially when faced with interconnected challenges such as particle interactions and the structural integrity of conveyor systems. This article focuses on the handling of materials and emphasizes the importance of using parametric numerical analysis to improve efficiency, reduce wear, and enhance the structural integrity of horizontal screw conveyors. Through the utilization of the Design of Experiments, we systematically investigated critical parameters such as screw pitch, clearance, wear, rotational velocity, and additional structural factors. This examination was carried out within a well-defined parametric framework, utilizing a combination of software tools provided by the Ansys suite and Minitab. The findings demonstrate the effectiveness of the Design of Experiments analysis in achieving improved performance and provide valuable insights for engineers and researchers involved in the design of conveyor systems. Furthermore, this comprehensive approach clarifies how conveyor systems respond to changes in parameters and highlights the complex interaction between transported particles and the conveyor system. We present a detailed analysis that clarifies the complex relationships and dependencies among different parameters, providing engineers and researchers with valuable insights. By understanding the interactions of these factors, the methodology provides not only results but also a strategic framework for advancing conveyor system design and engineering practices.
Ključne besede: discrete element method, design optimization, horizontal screw conveyors, parametric study, conveying equipment, bulk handling, bulk solids, abrasive wear, screw conveyor, FEA, performance analysis
Objavljeno v DKUM: 09.04.2024; Ogledov: 65; Prenosov: 5
.pdf Celotno besedilo (10,51 MB)
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Robotic bin-picking : benchmarking robotics grippers with modified YCB object and model set
Tone Lerher, Primož Bencak, Luka Bizjak, Darko Hercog, Boris Jerman, 2023, objavljeni znanstveni prispevek na konferenci

Opis: Robotic bin-picking is increasingly important in the order-picking process in intralogistics. However, many aspects of the robotic bin-picking process (object detection, grasping, manipulation) still require the research community's attention. Established methods are used to test robotic grippers, enabling comparability of the research community's results. This study presents a modified YCB Robotic Gripper Assessment Protocol that was used to evaluate the performance of four robotic grippers (twofingered, vacuum, gecko, and soft gripper). During the testing, 45 objects from the modified YCB Object and Model Set from the packaging categories, tools, small objects, spherical objects, and deformable objects were grasped and manipulated. The results of the robotic gripper evaluation show that while some robotic grippers performed substantially well, there is an expressive grasp success variation over diverse objects. The results indicate that selecting the object grasp point next to selecting the most suitable robotic gripper is critical in successful object grasping. Therefore, we propose grasp point determination using mechanical software simulation with a model of a two-fingered gripper in an ADAMS/MATLAB cosimulation. Performing software simulations for this task can save time and give comparable results to real-world experiments.
Ključne besede: intralogistics, robotic bin-picking, YCB protocol, robotic gripper evaluation, mechanical software simulations, performance analysis
Objavljeno v DKUM: 21.03.2024; Ogledov: 79; Prenosov: 7
.pdf Celotno besedilo (773,38 KB)
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Multi-criteria measurement of ai support to project management
Vesna Čančer, Polona Tominc, Maja Rožman, 2023, izvirni znanstveni članek

Opis: This paper aims to measure the level of artificial intelligence (AI) support to project management (PM) in selected service sector activities. The exploratory factor analysis was employed based on the extensive survey on AI in Slovenian companies and the multi-criteria measurement with an emphasis on value functions and pairwise comparisons in the analytic hierarchy process. The synthesis and performance sensitivity analysis results show that in the service sector, concerning all criteria, PM is with the level 0.276 best supported with AI in services of professional, scientific, and technical activities, which also stand out concerning the first-level goals in using AI solutions in a project with the value 0.284, and in successful project implementation using AI with the value 0.301. Although the lowest level of AI support to PM, which is 0.220, is in services of wholesale and retail trade and repair of motor vehicles and motorcycles, these services excel in adopting AI technologies in a project with a value of 0.277. Services of financial and insurance activities, with the level 0.257 second-ranked concerning all criteria, have the highest value of 0.269 concerning the first-level goal of improving the work of project leaders using AI. The paper, therefore, contributes to the comparison of AI support to PM in service sector activities. The results can help AI development policymakers determine which activities need to be supported and which should be set as an example. The presented methodological frame can serve to perform measurements and benchmarking in various research fields.
Ključne besede: artificial intelligence, factor analysis, multiple criteria, performance sensitivity, project management
Objavljeno v DKUM: 12.02.2024; Ogledov: 175; Prenosov: 12
.pdf Celotno besedilo (4,18 MB)
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An optimisation model for minimising totes exchange in VLM and SBS/RS integrated system
Jakob Marolt, Goran Đukić, Fabio Sgarbossa, Tone Lerher, 2022, objavljeni znanstveni prispevek na konferenci

Opis: Warehouses and distribution centres are based on integrated material handling solutions. Most of the research papers in intralogistics are only concerned with one system to analyse and optimise the addressed system's performance, such as maximum throughput performance, minimum total cost, maximum energy efficiency, etc. This paper presents a concept to justify the proposed VLM and SBS/RS integrated system and a binary integer programming (BIP) model that minimises totes exchange between the two storage systems. The results show that the minimal number of exchanges between VLM and SBS/RS was achieved in a case study with a longer order list (T = 1600) and a highly dependent SKU's Pareto relationship (20-50).
Ključne besede: automated warehousing, intralogistics, VLM, SBS, RS, integrated systemoptimisation, performance analysis
Objavljeno v DKUM: 02.08.2023; Ogledov: 298; Prenosov: 31
.pdf Celotno besedilo (743,43 KB)
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Product assembly assistance system based on pick-to-light and computer vision technology
Darko Hercog, Primož Bencak, Uroš Vincetič, Tone Lerher, 2022, izvirni znanstveni članek

Opis: Product assembly is often one of the last steps in the production process. Product assembly is often carried out by workers (assemblers) rather than robots, as it is generally challenging to adapt automation to any product. When assembling complex products, it can take a long time before the assembler masters all the steps and can assemble the product independently. Training time has no added value; therefore, it should be reduced as much as possible. This paper presents a custom-developed system that enables the guided assembly of complex and diverse products using modern technologies. The system is based on pick-to-light (PTL) modules, used primarily in logistics as an additional aid in the order picking process, and Computer Vision technology. The designed system includes a personal computer (PC), several custom-developed PTL modules and a USB camera. The PC with a touchscreen visualizes the assembly process and allows the assembler to interact with the system. The developed PC application guides the operator through the assembly process by showing all the necessary assembly steps and parts. Two-step verification is used to ensure that the correct part is picked out of the bin, first by checking that the correct pushbutton on the PTL module has been pressed and second by using a camera with a Computer Vision algorithm. The paper is supported by a use case demonstrating that the proposed system reduces the assembly time of the used product. The presented solution is scalable and flexible as it can be easily adapted to show the assembly steps of another product.
Ključne besede: product assembly, PTL, pick-to-light, computer vision, LabVIEW, performance analysis
Objavljeno v DKUM: 31.07.2023; Ogledov: 337; Prenosov: 19
.pdf Celotno besedilo (12,43 MB)
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Analysis and improvements of the mechanisms for cross-border interchange and activation of the regulating reserves : doctoral dissertation
Marcel Topler, 2022, doktorska disertacija

Opis: This Doctoral Thesis deals with the mechanisms for cross-border interchange and activation of the regulating reserves (RRs), i.e., Imbalance Netting Process (INP) and Cross-Border Activation of the RRs (CBRR), between participating Control Areas (CAs), to reduce the costs of balancing energy. The main objective of INP is to interchange the RRs between participating CAs with opposite signs of interchange power variation. In comparison, the main objective of CBRR is to activate the RRs in participating CAs with the same signs of interchange power variation. Both the INP and CBRR aim to release the RRs and reduce balancing energy as part of the power system's safe operation. The Thesis's main objective is to analyze the impact of the mechanisms for cross-border interchange and activation of the RRs on mutual oscillations of participating CAs and stability for small disturbances. The Thesis's secondary objective is to analyze the impact of the INP and CBRR on frequency quality, on the provision of Load-Frequency Control (LFC), on balancing energy and unintended exchange of energies between participating CAs. Frequency quality in Continental Europe (CE) has been declining in recent years, so it is important that the mechanisms for cross-border interchange and activation of the RRs do not further impair its quality. Both the classic INP and CBRR include a frequency-dependent contribution and, therefore, inherently affect the frequency response of the participating CAs, which is not discussed in the literature. Thus, the impact of the classic INP and CBRR on frequency quality and the provision of LFC is thoroughly evaluated with dynamic simulations of a three-CA test system and eigenvalue analysis of a two-CA system. It is demonstrated that both the classic INP and CBRR reduce the damping of the entire power system. Therefore, a modified implementation of the classic INP and CBRR is presented, and improved INP and CBRR are proposed, which have no impact on the mutual oscillations of participating CAs and stability for small disturbances. Furthermore, the dynamic simulations results confirm that the frequency quality can be improved by the classic INP and CBRR, although there are also cases where it can deteriorate. However, the improved INP and CBRR generally improve the frequency quality in all cases. The improved INP and CBRR also enhance the provision of LFC compared to the classic INP and CBRR. Moreover, the improved INP and CBRR reduce the unintended exchange of energies, thus increasing the economic effects of the INP's and CBRR's activation. The improved INP increases energy exchange, therefore positive economic benefits can be expected in comparison to the system with the classic INP. However, the improved CBRR reduces energy exchange, therefore positive economic benefits can be expected in comparison to the system with the classic CBRR, since energy exchange is paid by CA via bidding process.
Ključne besede: load-frequency control, imbalance netting, cross-border activation, balancing energy, regulating reserves, eigenvalue analysis, performance indicators, area control error, rate of change of frequency, control area
Objavljeno v DKUM: 09.03.2023; Ogledov: 413; Prenosov: 80
.pdf Celotno besedilo (14,64 MB)

Simulation model for robotic pick-point evaluation for 2-F robotic gripper
Primož Bencak, Darko Hercog, Tone Lerher, 2023, izvirni znanstveni članek

Opis: Robotic bin-picking performance has been gaining attention in recent years with the development of increasingly advanced camera and machine vision systems, collaborative and industrial robots, and sophisticated robotic grippers. In the random bin-picking process, the wide variety of objects in terms of shape, weight, and surface require complex solutions for the objects to be reliably picked. The challenging part of robotic bin-picking is to determine object pick-points correctly. This paper presents a simulation model based on ADAMS/MATLAB cosimulation for robotic pick-point evaluation for a 2-F robotic gripper. It consists of a mechanical model constructed in ADAMS/View, MATLAB/Simulink force controller, several support functions, and the graphical user interface developed in MATLAB/App Designer. Its functionality can serve three different applications, such as: (1) determining the optimal pick-points of the object due to object complexity, (2) selecting the most appropriate robotic gripper, and (3) improving the existing configuration of the robotic gripper (finger width, depth, shape, stroke width, etc.). Additionally, based on this analysis, new variants of robotic grippers can be proposed. The simulation model has been verified on a selected object on a sample 2-F parallel robotic gripper, showing promising results, where up to 75% of pick-points were correctly determined in the initial testing phase.
Ključne besede: intralogistics, robotic bin-picking, simulation model, ADAMS, pick-point determination, MATLAB/Simulink, 2-F robotic gripper, performance analysis
Objavljeno v DKUM: 27.02.2023; Ogledov: 592; Prenosov: 57
.pdf Celotno besedilo (19,99 MB)
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K-vertex: a novel model for the cardinality constraints enforcement in graph databases : doctoral dissertation
Martina Šestak, 2022, doktorska disertacija

Opis: The increasing number of network-shaped domains calls for the use of graph database technology, where there are continuous efforts to develop mechanisms to address domain challenges. Relationships as 'first-class citizens' in graph databases can play an important role in studying the structural and behavioural characteristics of the domain. In this dissertation, we focus on studying the cardinality constraints mechanism, which also exploits the edges of the underlying property graph. The results of our literature review indicate an obvious research gap when it comes to concepts and approaches for specifying and representing complex cardinality constraints for graph databases validated in practice. To address this gap, we present a novel and comprehensive approach called the k-vertex cardinality constraints model for enforcing higher-order cardinality constraints rules on edges, which capture domain-related business rules of varying complexity. In our formal k-vertex cardinality constraint concept definition, we go beyond simple patterns formed between two nodes and employ more complex structures such as hypernodes, which consist of nodes connected by edges. We formally introduce the concept of k-vertex cardinality constraints and their properties as well as the property graph-based model used for their representation. Our k-vertex model includes the k-vertex cardinality constraint specification by following a pre-defined syntax followed by a visual representation through a property graph-based data model and a set of algorithms for the implementation of basic operations relevant for working with k-vertex cardinality constraints. In the practical part of the dissertation, we evaluate the applicability of the k-vertex model on use cases by carrying two separate case studies where we present how the model can be implemented on fraud detection and data classification use cases. We build a set of relevant k-vertex cardinality constraints based on real data and explain how each step of our approach is to be done. The results obtained from the case studies prove that the k-vertex model is entirely suitable to represent complex business rules as cardinality constraints and can be used to enforce these cardinality constraints in real-world business scenarios. Next, we analyze the performance efficiency of our model on inserting new edges into graph databases with varying number of edges and outgoing node degree and compare it against the case when there is no cardinality constraints checking. The results of the statistical analysis confirm a stable performance of the k-vertex model on varying datasets when compared against a case with no cardinality constraints checking. The k-vertex model shows no significant performance effect on property graphs with varying complexity and it is able to serve as a cardinality constraints enforcement mechanism without large effects on the database performance.
Ključne besede: Graph database, K-vertex cardinality constraint, Cardinality, Business rule, Property graph data model, Property graph schema, Hypernode, Performance analysis, Fraud detection, Data classification
Objavljeno v DKUM: 10.08.2022; Ogledov: 616; Prenosov: 72
.pdf Celotno besedilo (3,43 MB)

The role of logistics in performance management
Mimo Drašković, 2016, samostojni znanstveni sestavek ali poglavje v monografski publikaciji

Opis: Apart from the proven and significant role of logistics in integrating marketing and management systems of a company, the position on the connection between the logistics and institutional (top) level of a business strategy in contemporary literature and business practice is being acknowledged. The mentioned position implies the implementation of performance management. In this way, the earlier opinion and praxis of connecting logistics with operations and provisional functioning in the area concerning a degree of integrations of business functions are being surpassed. The relationship between performance management and logistics can be considered from two aspects: a) role of logistics in enhancement of performance management and b) roles of measuring and analysis in enhancing the logistics performances themselves. This paper explains the mentioned dual relationship through the prism of acquirement of key competences and competitive advantages of an organization through enhancement of certain performances.
Ključne besede: logistics, performance management, enhancement, measuring, analysis
Objavljeno v DKUM: 09.05.2018; Ogledov: 947; Prenosov: 84
.pdf Celotno besedilo (3,15 MB)
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The analysis of barriers in succession processes of family business with the use of grey incidence analysis (Polish Perspective)
Ewa Więcek-Janka, Rafał Mierzwiak, Joanna Kijewska, 2016, izvirni znanstveni članek

Opis: The article presents results of research on the identification and evaluation of barriers faced by successors in family businesses during the first process of succession. The analysis of empirical material used grey systems theory, which was considered as an equivalent for the analysis of small samples and qualitative research. While conducting the literature review and empirical study, the authors concentrated on (a) the identification of barriers in the development of family firms and (b) eliciting the perspective of the new generation of owners in family firms entering the succession process through an empirical analysis of the assessed level of risk in relationships with family and business.
Ključne besede: family business, company performance, business efficiency, leadership, ownership, family, risk, research, grey incidence analysis, grey system theory
Objavljeno v DKUM: 14.11.2017; Ogledov: 1376; Prenosov: 389
.pdf Celotno besedilo (695,38 KB)
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