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This paper demonstrates a new methodology for designing a virtual factory model and model execution on the basis of a real schedule plan. The main characteristic of the developed method is that the inputs are regarded as one of the main parameters of the production process, and the main objective is to create a low-cost production process model. The methodology is adjusted for use in SMEs (Small and Medium-Sized Enterprises) with individual or unique type of production. For such companies, the method represents an ability to optimize existing production processes through detecting and eliminating possible errors and disturbances before the real production process is executed at an acceptable cost. The applicability and suitability of the developed method for virtual production performance has been proven with the verification process, where the input data for the simulation was obtained from a real company. The simulation results have shown that the presented methodology is a useful tool for the optimization of the production process.

In this paper we proposed a new architectural model of the smart factory to allow production experts to make easier and more exact planning of new, smart factories by using all the key technologies of Industry 4.0. The existing complex reference architectural model of Industry 4.0 (RAMI 4.0) offers a good overview of the smart-factory architecture, but it leads to some limitations and a lack of clarity for the users. To overcome these limitations, we have developed a simple model with the entire and very simple architecture of the smart factory, based on the concept of distributed systems with exact information and the data flows between them. The proposed architectural model enables more reliable and simple modelling of the smart factory than the existing RAMI 4.0 model. Our approach improves the existing methodology for planning the smart factory and makes all the necessary steps clearer. At the end of the paper a comparison of the proposed architectural model LASFA (LASIM Smart Factory) with the existing RAMI 4.0 model was made. The developed LASFA model was already successfully implemented in the laboratory environment for building the demo centre of a smart factory.

Original scientific paper This paper describes some possible methods for the reduction of the axial static flow forces in hydraulic sliding-spool and small on/off seat valves. These forces increase with the increase in the volume flow and the pressure difference and thus determine higher actuation forces for the control of the valve unit. This results in the necessary use of more powerful actuators for the direct control of hydraulic valves. The topic is therefore very relevant from the energy consumption point of view regarding the actuation of hydraulic valves. To make the use of low-power actuators for the control of directly actuated valves possible also for higher hydraulic power the flow forces acting on the valve piston in the axial direction must be reduced. This paper presents one of the possible solutions with such a design of the hydraulic valve housing and the spool that the flow stream of the fluid through the valve causes minimal axial static forces. The main influential geometry parameters of the sliding-spool and seat valve are defined and analysed in detail using the CFD (Computational Fluid Dynamics) simulation tool Ansys CFX and experimental analysis for the validation of the numerical fluid model of the valve. The results of the research are very promising and prove that the axial component of the flow forces and therefore the necessary actuation force can be reduced significantly just by modifying the geometry of the valve housing and spool. Thus the power consumption of the actuator is minimised and the valve dynamic characteristics are improved at the same time.Keywords: CFD simulation; experimental analysis; fluid flow forces; geometry optimisation; seat valve; sliding-spool valve CFD simulacija smanjenja sila protoka fluida u hidrauličnom ventiluIzvorni znanstveni članak Ovaj članak opisuje neke moguće metode za smanjenje statičnih sila protok ulja u hidrauličkom ventilu sa uzdužnim klipom i malim "on/off" sjedežnim ventilom. Sa porastom strujnog toka i razlike tlakova dolazi do povećanja aksijalnih statičnih sila što prouzročava upotrebu viših potisni sila odnosno veću potrošnju energije pri upravljanu ventila. Spomenjeno rezultira obaveznom upotrebom aktuatora veće snage za direktno upravljanje hidrauličkog ventila. Sa stajališta potrošnje energije pri upravljanju ventilom ova tema je veoma važna. Da bi omogućili upotrebu aktuatora niže snage za direktno upravljane ventila s visokim protokom ulja, potrebno je smanjiti aksijale sile koje djeluju na klip u ventilu.Ovaj istraživački rad predstavlja jedno od mogućih rješenja s takvim dizajnom kućišta hidrauličkog ventila i klipa da strujni tok ulja kroz ventil uzrokuje minimalne statične aksijalne sile. Glavni parametri geometrije ventila sa uzdužnim klipom i malim "on/off" ventila su definirani i detaljno analizirani pomoću CFD (Computational Fluid Dynamics) simulacijskoj alata Ansys CFX. Poslije toga provedena je eksperimentalna analiza za validaciju numeričkog modela ventila. Rezultati istraživanja su vrlo obećavajući i dokazuju da aksi...

A digital twin of a manufacturing system is a digital copy of the physical manufacturing system that consists of various digital models at multiple scales and levels. Digital twins that communicate with their physical counterparts throughout their lifecycle are the basis for data-driven factories. The problem with developing digital models that form the digital twin is that they operate with large amounts of heterogeneous data. Since the models represent simplifications of the physical world, managing the heterogeneous data and linking the data with the digital twin represent a challenge. The paper proposes a five-step approach to planning data-driven digital twins of manufacturing systems and their processes. The approach guides the user from breaking down the system and the underlying building blocks of the processes into four groups. The development of a digital model includes predefined necessary parameters that allow a digital model connecting with a real manufacturing system. The connection enables the control of the real manufacturing system and allows the creation of the digital twin. Presentation and visualization of a system functioning based on the digital twin for different participants is presented in the last step. The suitability of the approach for the industrial environment is illustrated using the case study of planning the digital twin for material logistics of the manufacturing system.

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This paper presents a new approach for modelling and simulation of hydraulic spool valves by using the already known simple mathematical expressions for describing the sliding spool geometry. The main objective of the research is to divide the hydraulic sliding spool into functional elements which can be described analytically. Such models can be implemented as micro components into any hydraulic simulation tool's library. By using such an approach, hydraulic valves can be designed very flexibly, with different shapes of spool metering edges in combination with other functional elements. The user can quickly find the most appropriate spool construction for the desired hydraulic system performance. This can be done in advance, before designing the real system. The paper deals with and presents only one of the several different geometrical shapes of spool metering edges and the corresponding mathematical models of the volume flow characteristics that we have developed. Simulation results are verified and confirmed with experimental tests using a real valve geometry.

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