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Optimizing smart manufacturing systems using digital twin
Robert Ojsteršek, Aljaž Javernik, Borut Buchmeister, 2023, izvirni znanstveni članek

Opis: Presented paper investigates the application of digital twins for the optimisation of intelligent manufacturing systems and focuses on the comparison between simulation modelling results and real-world production conditions. A digital twin was created in the Simio software environment using a data-driven simulation model derived from a real-world production system. Running the digital twin in real time, which was displayed graphically, facilitated the analysis of key parameters, including the number of finished products, average flow time, workstation utilization and product quality. The discrepancies were attributed to the use of random distributions of input data in the dynamic digital twin, as opposed to the long-term measurements and averages in the real-world system. Despite the limitations in the case study, the results underline the financial justification and predictive capabilities of digital twins for optimising production systems. Real-time operation enables continuous evaluation and tracking of parameters and offers high benefits for intelligent production systems. The study emphasises the importance of accurate selection of input data and warns that even small deviations can lead to inaccurate results. Finally, the paper high-lights the role of digital twins in optimising production systems and argues for careful consideration of input data. It highlights the importance of analysing real-world production systems and creating efficient simulation models as a basis for digital twin solutions. The results encourage extending the research to different types of production, from job shop to mass production, in order to obtain a comprehensive optimisation perspective.
Ključne besede: smart manufacturing, digital twin, optimisation, simulation modelling, Simio, case study
Objavljeno v DKUM: 25.03.2024; Ogledov: 97; Prenosov: 3
.pdf Celotno besedilo (1,28 MB)
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Obtaining the synthetic fuels from waste plastic and their effect on cavitation formation in a common-rail diesel injector
Luka Kevorkijan, Amalia Palomar-Torres, Eloisa Torres Jiménez, Carmen Mata, Ignacijo Biluš, Luka Lešnik, 2023, izvirni znanstveni članek

Opis: The presented paper addresses two significant issues of the present time. In general, the studies of the effect of synthetic fuels on cavitation formation and cavitation erosion prediction in the nozzle tip of common-rail diesel injectors were addressed. The first problem is plastic waste, which can have a significant negative environmental impact if not treated properly. Most plastic waste has high energy value, so it represents valuable material that can be used in resource recovery to produce various materials. One possible product is synthetic fuel, which can be produced using thermal and catalytic pyrolysis processes. The first issue addressed in the presented paper is the determination of fuel properties since they highly influence the fuel injection process, spray development, combustion, etc. The second is the prediction of cavitation development and cavitation erosion in a common-rail diesel injector when using pyrolytic oils from waste plastic. At first, pyrolytic oils from waste high- and low-density polyethylene were obtained using thermal and catalytic pyrolysis processes. Then, the obtained oils were further characterised. Finally, the properties of the obtained oils were implemented in the ANSYS FLUENT computational program and used in the study of the cavitation phenomena inside an injection nozzle hole. The cavitating flow in FLUENT was calculated using the Mixture Model and Zwart-Gerber-Belamri cavitation model. For the modelling of turbulence, a realisable k–ε model with Enhanced Wall Treatment was used, and an erosion risk indicator was chosen to compare predicted locations of cavitation erosion. The results indicate that the properties of the obtained pyrolytic oils have slightly lower density, surface tension and kinematic viscosity compared to conventional diesel fuel, but these minor differences influence the cavitation phenomenon inside the injection hole. The occurrence of cavitation is advanced when pyrolytic oils are used, and the length of cavitation structures is greater. This further influences the shift of the area of cavitation erosion prediction closer to the nozzle exit and increases its magnitude up to 26% compared to diesel fuel. All these differences have the potential to further influence the spray break-up process, combustion process and emission formation inside the combustion chamber.
Ključne besede: plastic waste, synthetic fuels, pyrolytic oils, common-rail, cavitation, erosion, transient simulation
Objavljeno v DKUM: 18.03.2024; Ogledov: 90; Prenosov: 5
.pdf Celotno besedilo (4,55 MB)
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Managing the complexity of empty container movements through repositioning strategies and routing practices under certain demand and supply : doctoral dissertation
Alaa Abdelshafie, 2023, doktorska disertacija

Opis: Over the past decades, container transportation management has become an important part of the global maritime industry. Due to an ever-increasing movement of containers across the globe in line with the economic boom, the trade imbalance and issues related to empty containers have become inevitable. The accumulation of empty containers in specific ports not only causes a waste of money but also increases the environmental footprint. Accordingly, the urgent need for empty container management has been gaining more attention than ever before, as the shipping companies recognized that more revenues are always derived from a good repositioning strategy. In this respect, this thesis described state-of-the-art of empty container management, focusing on the practices concerning the movement of empty containers that are varied between organizational policies, technical solutions, and optimization applications. With the development of computer-aided systems, the combination of optimization and simulation models has been proposed to tackle the maritime empty container problem. The thesis shows how the strengths of optimization-based simulation can be integrated to provide high-quality solutions with low computational costs. Agent-based modelling was developed to model the global movements of empty containers, providing realistic details of interactions among entities and characteristics of components within the system. The model was applied between ports in the Middle East and Asia for one of the biggest shipping lines worldwide. By using simulated annealing (SA), the best sequence for moving containers can be determined. The results comparison demonstrate that the proposed optimised repositioning strategy can significantly reduce the shipping line’s costs and make full use of empty containers in the planning horizon.
Ključne besede: shipping industry, container transportation management, empty container repositioning, simulation, optimization, agent-based modelling
Objavljeno v DKUM: 08.12.2023; Ogledov: 362; Prenosov: 16
.pdf Celotno besedilo (3,38 MB)

High strain-rate deformation analysis of open-cell aluminium foam
Anja Mauko, Mustafa Sarıkaya, Mustafa Güden, Isabel Duarte, Matej Borovinšek, Matej Vesenjak, Zoran Ren, 2023, izvirni znanstveni članek

Opis: This study investigated the high-strain rate mechanical properties of open-cell aluminium foam M-pore®. While previous research has examined the response of this type of foam under quasi-static and transitional dynamic loading conditions, there is a lack of knowledge about its behaviour under higher strain rates (transitional and shock loading regimes). To address this gap in understanding, cylindrical open-cell foam specimens were tested using a modified Direct Impact Hopkinson Bar (DIHB) apparatus over a wide range of strain rates, up to 93 m/s. The results showed a strong dependency of the foam's behaviour on the loading rate, with increased plateau stress and changes in deformation front formation and propagation at higher strain rates. The internal structure of the specimens was examined using X-ray micro-computed tomography (mCT). The mCT images were used to build simplified 3D numerical models of analysed aluminium foam specimens that were used in computational simulations of their behaviour under all experimentally tested loading regimes using LS-DYNA software. The overall agreement between the experimental and computational results was good enough to validate the built numerical models capable of correctly simulating the mechanical response of analysed aluminium foam at different loading rates.
Ključne besede: Open-cell aluminium foam, Micro-computed tomography, High-strain rate, Direct impact hopkinson bar, Digital image correlation, Computer simulation
Objavljeno v DKUM: 06.12.2023; Ogledov: 306; Prenosov: 28
.pdf Celotno besedilo (3,28 MB)
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PSpice simulations for single-phase rectifiers for testing DC fuses
Adrian Plesca, Costica Nituca, Gabriel Chiriac, Zhiyuan Liu, Yingsan Geng, 2019, izvirni znanstveni članek

Opis: In this article, simulations were realized for different power rectifiers used for testing DC fuses. Using the OrCAD PSpice software, a single-phase uncontrolled bridge rectifier and a single-phase controlled bridge rectifier are simulated for different loads. From the data analysis, some important conclusions were realized regarding the form of the temperature waveforms in transient conditions and quasisteady state thermal conditions.
Ključne besede: Power Rectifiers, Simulation, PSpice, DC fuse
Objavljeno v DKUM: 05.12.2023; Ogledov: 222; Prenosov: 3
.pdf Celotno besedilo (445,89 KB)
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Pantograph driven with a linear induction motor with adaptive fuzzy control
Costica Nituca, Gabriel Chiriac, 2019, izvirni znanstveni članek

Opis: This article presents an adaptive fuzzy control for a linear induction motor, which is used to control the vertical movement of a pantograph, which supplies an electric locomotive from a contact line. The system has the goal of eliminating all the discontinuity on the route, the resonance phenomenon, the separation of the pantograph head from the contact wire, and electric arches. The simulations demonstrate functional control of the pantograph driven with a linear induction motor system using fuzzy control techniques.
Ključne besede: linear induction motor, fuzzy control, locomotive pantograph, simulation
Objavljeno v DKUM: 05.12.2023; Ogledov: 146; Prenosov: 3
.pdf Celotno besedilo (1,04 MB)
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Optimal control of gain and offset in direct conversion receivers : magistrsko delo
Amadej Maurič, 2023, magistrsko delo

Opis: In the master’s thesis, the development and implementation of optimal control for direct conversion receiver is presented. A background overview of direct conversion receivers, in-phase and quadrature mixers, sampling theory, control theories, adaptive systems, and optimal control is given. The development of a system model which is later used in simulations is also presented. Optimal control is achieved through standard control techniques, such as feedback and feedforward control, with error functions giving restrictions. Information to feed the optimal control is acquired by the system through the analog converters to the digital converters, digital to analog converters, and received signal strength indicators. For the development and testing of optimal control, MATLAB environment was used. Simulations and presentation of the results were also done in MATLAB. Limitations, exact operation, and comments were given throughout the thesis
Ključne besede: optimal control, direct conversion receiver, radio frequency signal, simulation, MATLAB
Objavljeno v DKUM: 23.11.2023; Ogledov: 256; Prenosov: 0

Comparison and optimization of algorithms for simultaneous localization and mapping on a mobile robot : master's thesis
Matic Rašl, 2023, magistrsko delo

Opis: In this thesis, we compare and evaluate different SLAM solutions for a low-cost mobile robot. We present a simulator for the robot and use it to gather simulated data. Using this data, we then optimize the SLAM algorithms using an evolutionary algorithm. The optimized solutions are then validated and compared to default SLAM configurations. Up to 83 % reduction of error is achieved on validation data with multiple SLAM algorithms with improvements also visible on the real-world data.
Ključne besede: SLAM, optimization, mobile robot, evolutionary algorithm, simulation.
Objavljeno v DKUM: 05.10.2023; Ogledov: 271; Prenosov: 12
.pdf Celotno besedilo (2,64 MB)

Methodology improvements to simulate performance and emissions of engine transient cycles from stationary operating modes: A case study applied to biofuels
Fernando Cruz-Peragón, Eloisa Torres Jiménez, Luka Lešnik, Octavio Armas, 2022, izvirni znanstveni članek

Opis: In the present study engine/vehicle responses from a standardized transient test cycle are estimated using 13 stationary operating regimes following a previously developed methodology. The main advantage of the methodology tested is that allows obtaining an estimation of transient parameters in a stationary test bench, which requirements are much less demanding than those of the transient test bench. The objectives are: in one hand, to demonstrate that the methodology correctly estimates engine responses regardless of the fuel tested, as it is proposed in a previous paper and, on the other hand, to improve the methodology and the accuracy of the estimated parameters. The fuels tested are renewable fuels from different raw materials (biodiesel from rapeseed, sunflower, and soybean), and diesel fuel as the reference. Biodiesels were tested neat and blended (30% v/v) with diesel fuel. The engine is a common-rail light-duty one, and the standardized testing procedure used to illustrate the implementation of the methodology is the New European Driving Cycle (NEDC). Two design of experiments (DoE) of 13 runs each were analyzed. One of the DoE tested was proposed for characterizing the NEDC, referred as to CTDoE design, while the other one is a five-level fractional factorial design (FFDoE) that adequately matches the optimality criteria of orthogonality, D-optimal criterion, rotatability, and space-filling. The original methodology was improved by the implementation of a new fitting function that simulates the cold start effect over the engine parameters and by an new definition of the boundary in the [n,M] domain. These improvements showed significantly higher accuracy of the estimated engine parameters obtained, both instantaneous and accumulated, respect to the original methodology. The results obtained based on the application of the FFDoE design support the feasibility of the methodology tested. Engine performance and regulated emissions responses, such as intake air and fuel mass flow rate, thermomechanical exergy rate, exhaust gas residual heat rate, total hydrocarbons (THC), nitrogen oxides (NOx), carbon monoxide (CO) and particulate matter (PM) emissions from a transient test were instantaneously and cumulatively predicted with high accuracy using the engine responses from 13 steady-state operating modes.
Ključne besede: simulation, light duty diesel engine, transient cycle, biodiesel, design of experiments, cold start correction function
Objavljeno v DKUM: 21.09.2023; Ogledov: 205; Prenosov: 14
.pdf Celotno besedilo (13,39 MB)
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The impact of serious games in economic and business education: a case of ERP business simulation
Tina Beranič, Marjan Heričko, 2022, izvirni znanstveni članek

Opis: Digitalisation nowadays impacts business environments significantly. Therefore, if higher education wants to educate students properly for a successful career path, the business and economics curriculum must be enriched with innovative teaching approaches covering actual topics, such as, for example, the implementation of the ERPsim business simulation, a representative of serious games. The ERPsim business simulation is based on SAP ERP, and is aimed at teaching ERP concepts. It covers different business processes, and allows students to learn using a hands-on approach, simulating real-life scenarios. The presented research focuses on using an ERPsim business simulation as the introduction to the course. The simulation was implemented to ease the introduction of ERP and IT concepts to the business and economic oriented students. Considering the positive effects of serious games and gamification, our research was formed and focused on knowledge acquisition and future student engagement. We researched whether participation in the introductory simulation results in significant knowledge gain and impacts students’ future course engagement. The data were gathered using a self-assessment questionnaire before and after an introductory simulation. The results were highly positive, confirming many positive aspects of business simulation, among others, significant knowledge increase in the domains of business process and ERP transactions, and in the domain of technical knowledge for SAP ERP. The results confirmed that the introductory simulation is appropriate for introducing ERP concepts to newcomers, and, nevertheless, confirmed the positive impact on their intent on future course engagement.
Ključne besede: business simulation, knowledge acquisition, course engagement, ERPsim, SAP, gamification
Objavljeno v DKUM: 17.08.2023; Ogledov: 310; Prenosov: 31
.pdf Celotno besedilo (337,46 KB)
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