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Schwarzl C.,Virtual Vehicle Competence Center | Peischl B.,University of Graz
Proceedings - International Conference on Quality Software | Year: 2010

Today's multimedia solutions in the automotive industry are complex and distributed hardware/software systems that interact with a multitude of different environments. Assuring the functional correctness of such software-enabled systems is a major issue to maintain and improve overall product quality. In this article we report on a test case generation approach, that allows engineers to employ well-known UML state chart models to deduce test cases fully automatically. Our approach is based on symbolic transition systems (STSs) and overcomes the intricacies resulting from straightforward application of enumerative test models (e.g. state space explosion). The derivation of the test sequences is performed by searching paths through the STS models with respect to their communication structure. By calculating the weakest preconditions of these paths the validity of the paths (and their related parameters) is ensured. Notably, our first empirical results on an industry showcase - a flashing indicator model developed with our industry partner - indicate that our model composition approach is applicable for both - systematic as well as randomized test case generation. © 2010 IEEE. Source


Zangl H.,University of Graz | Fuchs A.,Virtual Vehicle Competence Center | Bretterklieber T.,University of Graz | Moser M.J.,University of Graz | Holler G.,University of Graz
IEEE Transactions on Instrumentation and Measurement | Year: 2010

Passive or semiactive wireless sensors, i.e., sensors that require neither wires nor external power supply/batteries, are attractive for many measurement problems. Standard approaches based on Radio Frequency Identification technology usually have difficulties when a fairly conductive matter such as steel or a large amount of water is in the vicinity of the devices. This paper investigates methods for power and data transmission, even through the metal walls, e.g., of a tank or a pipe using super low frequency carrier signals. The feasibility is demonstrated by means of finite-element analysis and laboratory experiments and validated with a prototype setup for both a steel pipe and a tin container. Experimental results for capacitive fill-level measurement inside a metallic container are reported. © 2006 IEEE. Source


Benedikt M.,Virtual Vehicle Competence Center | Benedikt M.,University of Graz | Stippel H.,Virtual Vehicle Competence Center | Watzenig D.,Virtual Vehicle Competence Center
SAE Technical Papers | Year: 2010

In the automotive industry well-established different simulation tools targeting different needs are used to mirror the physical behavior of domain specific components. To estimate the overall system behavior coupling of these components is necessary. As systems become more complex, simulation time increases rapidly by using traditional coupling approaches. Reducing simulation time by still maintaining accuracy is a challenging task. Thus, a coupling methodology for co-simulation using adaptive macro step size control is proposed. Convergence considerations of the used algorithms and scheduling of domain specific components are also addressed. Finally, the proposed adaptive coupling methodology is examined by means of a cross-domain co-simulation example describing a hybrid electric vehicle. Considerable advantages in terms of simulation time reduction are presented and the trade-off between simulation time and accuracy is depicted. Copyright © 2010 SAE International. Source


Allmaier H.,Virtual Vehicle Competence Center | Priestner C.,Virtual Vehicle Competence Center | Six C.,Virtual Vehicle Competence Center | Priebsch H.H.,Virtual Vehicle Competence Center | And 2 more authors.
Tribology International | Year: 2011

It is the aim of this work to predict friction in journal bearings reliably and accurately under realistic dynamic working conditions. To this purpose elastohydrodynamic (EHD) calculations using an extensive oil-model and including an approach to the conformal roughnesses of the bearing surfaces are carried out for transient loads typical for current utility vehicles (40 MPa) as well as for considerably higher specific loads (70 MPa) and for different lubricants (SAE10, SAE20, SAE30 and SAE40) to account for a large span of working conditions ranging from full film lubrication to mixed lubrication with metalmetal contact. The results obtained from this simulation model are compared to measurements performed on a journal bearing test rig. We find that the results of the presented approach agree very closely with the experimental values. The presented approach allows consequently to investigate the effectiveness of changes in bearing geometry, bearing materials, bearing surface roughness, lubricant viscosity and engine operating conditions to reduce friction in journal bearings. © 2011 Elsevier Ltd. All rights reserved. Source


Allmaier H.,Virtual Vehicle Competence Center | Priestner C.,Virtual Vehicle Competence Center | Reich F.M.,Virtual Vehicle Competence Center | Priebsch H.H.,Virtual Vehicle Competence Center | Novotny-Farkas F.,OMV Austria Exploration and Production GmbH
Tribology International | Year: 2013

In a previous work an elastohydrodynamic (EHD) simulation model was presented to predict the frictional losses within journal bearings and validated with a large set of measurements. In the current work this simulation model is extended to a thermoelastohydrodynamic (TEHD) simulation to take into account the influence of local temperatures within the bearing. Detailed comparisons of the results between the two models show that for full film lubricated and even slightly mixed lubricated working conditions the inclusion of local temperatures results in rather small corrections to the properties studied. In addition, a method is developed from the TEHD-results to estimate a representative global oil temperature for single bearings to predict friction with the EHD-model. © 2012 Elsevier Ltd. Source

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