Virtual Vehicle Research Center

Graz, Austria

Virtual Vehicle Research Center

Graz, Austria
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Stanisavljevic D.,Virtual Vehicle Research Center | Spitzer M.,Virtual Vehicle Research Center
CEUR Workshop Proceedings | Year: 2017

This paper deals with applications of machine learning algorithms in manufacturing. Machine learning can be defined as a field of computer science that gives computers the ability to learn without explicitly developing the needed algorithms. Manufacturing is the production of merchandise by manual labour, machines and tools. The focus of this paper is on automatic production lines. The areas of interest of this paper are semiconductor manufacturing and production on assembly lines. The purpose of this paper is to review the relevant papers describing the applications of machine learning techniques in these fields of manufacturing thus creating a firm foundation for further research in the matter of machine learning in manufacturing. Copyright © 2016 for this paper by its authors.


Masovic D.,Virtual Vehicle Research Center
24th Telecommunications Forum, TELFOR 2016 | Year: 2016

The focus of this paper is improving predictions of airborne sound insulation in buildings based on the classical model of sound transmission. Firstly, it is demonstrated that acoustic properties of real noise in buildings can have a critical influence on the rating values of sound insulation and their correlation with subjective impression of the achieved acoustic comfort. Secondly, the contributions of the most important descriptors of building elements and junctions between them are analysed. Finally, the two standardized models, detailed and simplified, are compared in various practical sound insulation scenarios. © 2016 IEEE.


Veloso R.,Virtual Vehicle Research Center | Elnemr Y.,Virtual Vehicle Research Center
Noise Control Engineering Journal | Year: 2017

1D linear acoustic or gas-dynamics modeling of intake and exhaust systems is typically done during the early development stages of a vehicle in order to do quick sound design assessments. One of the components in the intake system of a turbocharged IC engine is the automotive charge air cooler. The charge air cooler is positioned at the outlet of the compressor in order to cool the charged air before it enters the engine. Charge air coolers are typically modeled as a 1D system comprised of an intake tank/duct, cooling tubes and an outlet tank/duct. A problem arises when the position of the inlet/outlet ducts is not axially symmetrical, which introduces three-dimensional acoustic effects. This behavior is not included in typical 1D modeling. Finite element modeling could be used to describe this 3D effect but would need much longer time and a detailed geometrical model that could be unavailable during the early development stage. In this study an acoustic multi-port description of the charge air cooler model is presented. Such a description includes the influence of the asymmetric position of the inlet/outlet ducts on the acoustics. The multi-port description is then reduced to an equivalent acoustic two-port model for the entire charge air cooler between its inlet/outlet ports. The frequency dependent transmission loss (TL) is calculated and compared to experimental results with good agreement. © 2017 Institute of Noise Control Engineering.


Suhr B.,Virtual Vehicle Research Center | Six K.,Virtual Vehicle Research Center
Granular Matter | Year: 2017

The prediction quality of discrete element method (DEM) models for railway ballast can be expected to depend on three points: the geometry representation of the single particles, the used contact models and the parametrisation using principal experiments. This works aims at a balanced approach, where none of the points is addressed with excessive depth. In a first step, a simple geometry representation is chosen and the simplified Hertz–Mindlin contact model is used. When experimental data of cyclic compression tests and monotonic direct shear tests are considered, the model can be parametrised to fit either one of the two tests, but not both with the same set of parameters. Similar problems can be found in literature for monotonic and cyclic triaxial tests of railway ballast. In this work, the comparison between experiment and simulation is conducted using the entire data of the test, e.g. shear force over shear path curve from the direct shear test. In addition to a visual comparison of the results also quantitative errors based on the sum of squares are defined. To improve the fit of the DEM model to both types of experiments, an extension on the Hertz–Mindlin contact law is used, which introduces additional physical effects (e.g. breakage of edges or yielding). This model introduces two extra material parameters and is successfully parametrised. Using only one set of parameters, the results of the DEM simulation are in good accordance with both experimental cyclic compression test and monotonic directs shear test. © 2017, The Author(s).


Schoeftner J.,Johannes Kepler University | Ebner W.,Virtual Vehicle Research Center
Vehicle System Dynamics | Year: 2017

Automated and manual transmissions are the main link between engine and powertrain. The technical term when the transmission provides the desired torque during all possible driving conditions is denoted as powertrain matching. Recent developments in the last years show that double-clutch-transmissions (DCTs) are a reasonable compromise in terms of production costs, shifting quality, drivability and fuel efficiency. They have several advantages compared to other automatic transmissions (AT). Most DCTs nowadays consist of a hydraulic actuation control unit, which controls the clutches of the gearbox in order to induce a desired drivetrain torque into the driveline. The main functions of hydraulic systems are manifold: they initiate gear shifts, they provide sufficient oil for lubrication and they control the shift quality by suitably providing a desired oil flow or pressure for the clutch actuation. In this paper, a mathematical model of a passenger car equipped with a DCT is presented. The objective of this contribution is to get an increased understanding for the dynamics of the hydraulic circuit and its coupling to the vehicle drivetrain. The simulation model consists of a hydraulic and a mechanical domain: the hydraulic actuation circuit is described by nonlinear differential equations and includes the dynamics of the line pressure and the proportional valve, as well as the influence of the pressure reducing valve, pipe resistances and accumulator dynamics. The drivetrain with its gear ratios, moments of inertia, torsional stiffness of the rotating shafts and a simple longitudinal vehicle model represent the mechanical domain. The link between hydraulic and mechanical domain is given by the clutch, which combines hydraulic equations and Newton's laws. The presented mathematical model may not only be used as a simulation model for developing the transmission control software, it may also serve as a virtual layout for the design process phase. At the end of this contribution a parametric study shows the influence of the mechanical components, the accumulator and the temperature of the oil. © 2017 Informa UK Limited, trading as Taylor & Francis Group


Steiner A.,Virtual Vehicle Research Center | Mladek A.,Virtual Vehicle Research Center
2017 12th International Conference on Ecological Vehicles and Renewable Energies, EVER 2017 | Year: 2017

One of the biggest barriers towards large scale adoption of electric and plug-in hybrid cars is still range limitation due to limited storage capacity of electric batteries. The air conditioning system for passenger comfort and the thermal conditioning system (battery and powertrain) are main auxiliary consumers in EVs with respect to energy consumption. Therefore, the Horizon 2020 project «OPTEMUS» proposes to tackle this bottleneck by leveraging low energy consumption and energy harvesting through a holistic vehicle-occupant-centred approach. This manuscript presents the approach of the project and first simulation results of the air conditioning system including a heat pump. This system is capable of using the ambient air or a preconditioned battery as heat source. © 2017 IEEE.


Suhr B.,Virtual Vehicle Research Center | Six K.,Virtual Vehicle Research Center
Computational Particle Mechanics | Year: 2017

In the discrete element simulation of granular materials, the modelling of contacts is crucial for the prediction of the macroscopic material behaviour. From the tribological point of view, friction at contacts needs to be modelled carefully, as it depends on several factors, e.g. contact normal load or temperature to name only two. In discrete element method (DEM) simulations the usage of Coulomb’s law of friction is state of the art in modelling particle–particle contacts. Usually in Coulomb’s law, for all contacts only one constant coefficient of friction is used, which needs to reflect all tribological effects. Thus, whenever one of the influence factors of friction varies over a wide range, it can be expected that the usage of only one constant coefficient of friction in Coulomb’s law is an oversimplification of reality. For certain materials, e.g. steel, it is known that a dependency of the coefficient of friction on the contact normal load exists. A more tribological tangential contact law is implemented in DEM, where the interparticle friction coefficient depends on the averaged normal stress in the contact. Simulations of direct shear tests are conducted, using steel spheres of different size distributions. The strong influence of interparticle friction on the bulk friction is shown via a variation of the constant interparticle friction coefficient. Simulations with constant and stress-dependent interparticle friction are compared. For the stress-dependent interparticle friction, a normal stress dependency of the bulk friction is seen. In the literature, measurements of different granular materials and small normal loads also show a stress dependency of the bulk friction coefficient. With increasing applied normal stress, the bulk friction coefficient reduces both in the experiments and in the simulations. © 2016, The Author(s).


Allmaier H.,Virtual Vehicle Research Center | Offner G.,AVL List GmbH
SAE Technical Papers | Year: 2016

Elastohydrodynamic (EHD)-simulation is a widely applied simulation technique that is used in a very diverse field of applications ranging from the study of vibroacoustics to the calculation of friction power losses in lubricated contacts. In particular, but not limited to, the automotive industry, technical advances and new requirements put current EHD simulation methodology under test. Ongoing trends like downsizing, downspeeding, start-stop and the continuing demand for increasing fuel efficiency impose new demands and challenges also on the simulation methodology. Increasing computational capabilities enable new simulation opportunities on the other hand. In the following, an overview is given on the current state of the art and today's challenges for the elastohydrodynamic simulation of journal bearings and their wide range of applications from highly loaded main bearings supporting the crank shaft in the ICE to high speed turbocharger bearings. The topics addressed in this work span a wide range from mixed lubrication, low viscosity lubricants, polymer coatings, microstructured surfaces to the simulation of the thermal behavior and the simulation of hydraulically coupled journal bearings as they are commonly present in internal combustion engines. Copyright © 2016 SAE International.


Steiner A.,Virtual Vehicle Research Center | Rieberer R.,University of Graz
Applied Thermal Engineering | Year: 2013

The use of resistance heaters with PTC elements to cover the heat demand of electric vehicles reduces significantly the cruising range. Reversible cooling and heating systems are one of the most promising solutions for this problem. However, in heat pump mode the frost formation on the exterior heat exchanger reduces the performance and efficiency of the system. Therefore, an efficient defrosting method is crucial to benefit from the heat pump also under frosting conditions. In the present paper, measurement results of a reverse cycle defrosting process on a reversible cooling and heating system using CO 2 as working fluid for an electric city car at chosen operating condition are discussed. Further, a transient Modelica simulation model was set up in order to assess the impact of different parameters during defrosting and to optimize the process. The simulation results showed the effect of different throttle valve openings on the defrosting process and a best performing valve-opening, where the defrost efficiency was higher and the defrost time was shorter compared to the other cases. © 2013 Elsevier Ltd. All rights reserved.


de Rijk S.,Virtual Vehicle Research Center | Nijman E.,Virtual Vehicle Research Center
Journal of Sound and Vibration | Year: 2016

A novel method for representing the transverse vibrations of sandwich beams as equivalent Timoshenko beams is developed. Special attention is given to damping modelling together with the evanescent parts of the solutions to assert applicability of the approach to any boundary conditions. Shear stiffness is evaluated based on current knowledge. The latter is then used to update the reference theory for vibrations in sandwich beams. Analytical case studies are presented to show the performance and limitations of the method and compared with experimental data. © 2016 Elsevier Ltd.

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