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Assembly line optimization using MTM time standard and simulation modeling—A case study
Matic Breznik, Borut Buchmeister, Nataša Vujica-Herzog, 2023, original scientific article

Abstract: This study presents an approach to solving the assembly line balancing problem (ALBP) using the Methods-Time Measurement (MTM) time standard and simulation software. ALBP is a common problem in manufacturing where a set of tasks with fixed times must be assigned to a series of sequential workstations in order to minimize the total idle time and reduce the assembly cost per product. This study uses MTM, a widely used production process scheduling method, to create a new time analysis of an assembly process that was previously balanced using the Work-Factor method and time study. This literature review shows that there are a lack of combinations of updated time analyses with newer simulation approaches in the current literature, and this was the motivation for the present work. An assembly line simulation was performed using Simio software to evaluate different design options and operating scenarios. The results show that the use of MTM and simulation can help minimize idle time and improve assembly line performance, thereby reducing costs and increasing efficiency. This study shows that the approach of using MTM and simulation is effective in solving ALBP and is a useful tool for manufacturing companies to improve the performance of their assembly lines and reduce costs.
Keywords: optimization, production planning, assembly line, MTM time standard, simulation, industry 4.0
Published in DKUM: 23.05.2023; Views: 39; Downloads: 3
.pdf Full text (3,25 MB)

Planning and construction of the lifting and towing device of the autonomous mobile robot MiR 100 for the delivery of transport trolleys in intralogistics
Tone Lerher, Aleš Belšak, Rok Skerbiš, Jure Tumpej, Žiga Volavšek, Domen Stamenov, Marko Motaln, 2022, published scientific conference contribution

Abstract: Intralogistics is a very important area in warehousing and production for managing the flow of materials and informational flow. In recent years, automation and especially robotisation have had a major impact on throughput performance in intralogistics. Especially important is the transport of materials and products based on automated guided vehicles (AGVs) and autonomous mobile robots (AMRs) with different top modules, such as the lifting and towing device. In this paper, planning and construction of the lifting and towing device of the autonomous mobile robot MiR 100 for the delivery of transport trolleys in intralogistics is presented. Using the engineering design methods, a new design of the lifting and towing device has been proposed and evaluated.
Keywords: intralogistics, material handling systems, automation and robotisation, planning and construction, lifting and towing mechanism, simulation and animation
Published in DKUM: 15.03.2023; Views: 216; Downloads: 44
.pdf Full text (1,45 MB)

Simulation model for robotic pick-point evaluation for 2-F robotic gripper
Primož Bencak, Darko Hercog, Tone Lerher, 2023, original scientific article

Abstract: 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.
Keywords: intralogistics, robotic bin-picking, simulation model, ADAMS, pick-point determination, MATLAB/Simulink, 2-F robotic gripper, performance analysis
Published in DKUM: 27.02.2023; Views: 170; Downloads: 20
.pdf Full text (19,99 MB)
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The importance of the correct choice of Franz diffusion cell volume for in vitro drug release testing of wound dressings
Tina Maver, Uroš Maver, 2022, original scientific article

Keywords: in vitro drug release testing, Franz diffusion cells, simulation, naproxen, alginate
Published in DKUM: 16.02.2023; Views: 178; Downloads: 19
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Measurements of material heat transfer properties : master study programme
Miha Donša, 2022, master's thesis

Abstract: An experimental setup was created to observe temperature change at two points inside the experimental body. Such an experimental setup created data that was used as an anchor point of optimization that was coupled with numerical models to find unknown variables of heat conductivity and specific heat of the materials. Two numerical models were created. A 1D numerical model was created for possibilities of fast optimization ignoring the insulation and heat transfer through it. Such a model did not manage to describe the experimental setup accurately. Therefore, a 3D numerical model was created simulating the whole experimental setup and yielded much more promising results. Problems with the model were soon seen when experimental data was compared to the numerical solution where variables that were initially not taken into the account showed a much greater effect than first anticipated. Therefore, the 3D numerical model was adjusted to describe the experimental setup as accurately as possible. The experiment was done with two different materials. The materials were picked based on their heat conductivity (high and low). High heat conductivity material was easy to understand and to find a solution to it. With low conductivity material, some problems were quickly observed and as such created a lot of questions as to why and how to find the unknown variables of the material. It was then shown that the masses of the materials in the experiment and the length of the experiment played the most important role in the experiment and quickly explained why and how the experimental setup should be modified to obtain better results.
Keywords: heat transfer, material heat transfer properties, specific heat, heat conductivity, optimization, numerical simulation of heat transfer
Published in DKUM: 07.07.2022; Views: 309; Downloads: 31
.pdf Full text (6,54 MB)

Suitability of Hydrogen Fuel Cell Powertrain for High-Performance Sports Cars : diplomsko delo
Dominik Ozmec, 2021, undergraduate thesis

Abstract: This bachelor´s thesis describes the development of Hydrogen Fuel Cell powertrain based on the case of the Tushek TS900 hybrid car. We wanted to see if a hydrogen fuel cell-powered vehicle could achieve comparable performance compared to an existing hybrid vehicle. We have built a Fuell Cell propulsion model for the high-performance sports car Tushek TS900, then we presented the basics and principles of the powertrains itself, and its connections. We performed vehicle acceleration simulations and compared them with a hybrid powertrain powered vehicle.
Keywords: hydrogen fuel cells, sports cars, powertrain design, car characteristics, driving simulation
Published in DKUM: 16.02.2022; Views: 377; Downloads: 46
.pdf Full text (3,24 MB)

Pressurized Water Nuclear Reactor Downcomer Flow Simulation : diplomsko delo
Aljaž Kekec, 2021, undergraduate thesis

Abstract: In the diploma thesis the flow pattern and conditions in the downcomer of a pressurized water nuclear reactor were simulated, to study coolant mixing inside the primary circuit. This was done using computational dynamics software Ansys CFX. The nuclear reactor in Krško (Slovenia) was used as a basis for the model. The downcomer geometry was simplied for a more feasible study. Three separate simulations were done: one with normal conditions, one with loss of coolant accident conditions and one with a modified geometry. The flow was then studied at different condition at the same levels using velocity contours. The results showed that the axial velocity profiles at the downcomer outlet are not completely uniform.
Keywords: Nuclear Power Plant, Pressurized Water Reactor, Downcomer, Flow simulation, Ansys CFX
Published in DKUM: 13.10.2021; Views: 548; Downloads: 48
.pdf Full text (2,49 MB)

Monte Carlo simulation of air resistance on an ellipsoid in motion
Veronika Bukina, 2021, master's thesis

Abstract: The main goal of the master's thesis was the analysis of air resistance on the body in motion in a model that does not require solving the Navier-Stokes equations, but works on the basis of mechanics and statistical physics. The model was a Monte Carlo (MC) simulation of the motion of ideal gas molecules in a closed container in which a body was placed, moving along one of the axes. For the most part of calculations, the approach was used when the body was fixed in the middle of the simulation cell, and one of the components of the molecular velocity had an additional term that simulated the flow, as if the body was moving at this speed in the opposite direction. First of all, a linear dependence of the drag force on speed was found for low flow speed for a flat plate, which was predicted by linear drag law. For high molecular flow rates, the quadratic dependence predicted by the Bernoulli equation was clearly observed. The results of calculating the corresponding resistivity coefficients for the flat plate were in agreement with the analytical values for both regimes of speeds. By analogy, a simulation was made for a spherical body, which also demonstrated a strong quadratic dependence at high speeds and the drag coefficient value is approximately equal to the analytical one. In the following, we studied systematically ellipsoids with circular cross-section, where we varied the ratio between semiaxes in the direction of motion and perpendicular direction, respectively. The results for the ellipsoid showed that the drag coefficient value is maximum for a flat plate (a limiting case of an ellipsoid, when the semiaxis in the direction of motion tends to 0) and decreases with stretching of the body along the flow axis. When the Maxwell distribution of molecular speeds that was mainly used was replaced with uniform Root-Mean-Square (RMS) speed the results for drag coefficient were slightly different.
Keywords: Air resistance, drag force, quadratic drag law, drag coefficient, Monte Carlo (MC) simulation, Maxwell distribution.
Published in DKUM: 13.10.2021; Views: 502; Downloads: 33
.pdf Full text (1,64 MB)

Measurement and modelling of power SiC MOSFET transistors : master's thesis
Darjan Molnar, 2021, master's thesis

Abstract: The increasing demand for smaller, faster, and more efficient switch mode power supplies (SMPS) and energy converters has led to the development of new power MOSFET technologies, such as SiC (silicon carbide) power MOSFET transistors. Switching parameters, output voltages and currents and power consumption need to be measured accurately to assess different types of power electronics components more efficiently in today’s rapid implementation of new energy transfer and modulation technology. The need for improving switching circuits in power electronics and trying to use simple simulation circuits for designing PCBs to measure output values of said power electronics transistors is the basis of this thesis. Even though manufacturers of power electronics transistors provide data on drain-source voltages and currents, these are mostly measured for specific conditions regarding pulse duration, gate-source voltage, case temperature of the transistor etc., and as such do not provide information as to where the limits of the drain source voltages and currents for different measurement parameter values are. The goal of the thesis is to find a way to measure the limits of drain-source voltages and currents of power electronics transistors (in this case a SiC MOSFET transistor), and to see if a simple SPICE-model could be built for other power electronic transistors as well, based on the results of this thesis.
Keywords: SiC, MOSFET, transistor, simulation, PCB
Published in DKUM: 02.06.2021; Views: 623; Downloads: 45
.pdf Full text (4,35 MB)

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