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  • 1.
    Acsintoae, Andra
    et al.
    Univ Bucharest, Romania.
    Florescu, Andrei
    Univ Bucharest, Romania.
    Georgescu, Mariana-Iuliana
    Univ Bucharest, Romania; MBZ Univ Artificial Intelligence, U Arab Emirates; SecurifAI, Romania.
    Mare, Tudor
    SecurifAI, Romania.
    Sumedrea, Paul
    Univ Bucharest, Romania.
    Ionescu, Radu Tudor
    Univ Bucharest, Romania; SecurifAI, Romania.
    Khan, Fahad
    Linköpings universitet, Institutionen för systemteknik, Datorseende. Linköpings universitet, Tekniska fakulteten. MBZ Univ Artificial Intelligence, U Arab Emirates.
    Shah, Mubarak
    Univ Cent Florida, FL 32816 USA.
    UBnormal: New Benchmark for Supervised Open-Set Video Anomaly Detection2022Ingår i: 2022 IEEE/CVF CONFERENCE ON COMPUTER VISION AND PATTERN RECOGNITION (CVPR 2022), IEEE COMPUTER SOC , 2022, s. 20111-20121Konferensbidrag (Refereegranskat)
    Abstract [en]

    Detecting abnormal events in video is commonly framed as a one-class classification task, where training videos contain only normal events, while test videos encompass both normal and abnormal events. In this scenario, anomaly detection is an open-set problem. However, some studies assimilate anomaly detection to action recognition. This is a closed-set scenario that fails to test the capability of systems at detecting new anomaly types. To this end, we propose UBnormal, a new supervised open-set benchmark composed of multiple virtual scenes for video anomaly detection. Unlike existing data sets, we introduce abnormal events annotated at the pixel level at training time, for the first time enabling the use of fully-supervised learning methods for abnormal event detection. To preserve the typical open-set formulation, we make sure to include dis-joint sets of anomaly types in our training and test collections of videos. To our knowledge, UBnormal is the first video anomaly detection benchmark to allow a fair head-to-head comparison between one-class open-set models and supervised closed-set models, as shown in our experiments. Moreover, we provide empirical evidence showing that UB-normal can enhance the performance of a state-of-the-art anomaly detection framework on two prominent data sets, Avenue and ShanghaiTech. Our benchmark is freely available at https://github.com/lilygeorgescu/UBnormal.

  • 2.
    Adolfsson, Henrik
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik.
    Comparison of Auto-Scaling Policies Using Docker Swarm2019Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    When deploying software engineering applications in the cloud there are two similar software components used. These are Virtual Machines and Containers. In recent years containers have seen an increase in popularity and usage, in part because of tools such as Docker and Kubernetes. Virtual Machines (VM) have also seen an increase in usage as more companies move to solutions in the cloud with services like Amazon Web Services, Google Compute Engine, Microsoft Azure and DigitalOcean. There are also some solutions using auto-scaling, a technique where VMs are commisioned and deployed to as load increases in order to increase application performace. As the application load decreases VMs are decommisioned to reduce costs.

    In this thesis we implement and evaluate auto-scaling policies that use both Virtual Machines and Containers. We compare four different policies, including two baseline policies. For the non-baseline policies we define a policy where we use a single Container for every Virtual Machine and a policy where we use several Containers per Virtual Machine. To compare the policies we deploy an image serving application and run workloads to test them. We find that the choice of deployment strategy and policy matters for response time and error rate. We also find that deploying applications as described in the methodis estimated to take roughly 2 to 3 minutes.

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  • 3. Beställ onlineKöp publikationen >>
    Aghighi, Meysam
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Computational Complexity of some Optimization Problems in Planning2017Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Automated planning is known to be computationally hard in the general case. Propositional planning is PSPACE-complete and first-order planning is undecidable. One method for analyzing the computational complexity of planning is to study restricted subsets of planning instances, with the aim of differentiating instances with varying complexity. We use this methodology for studying the computational complexity of planning. Finding new tractable (i.e. polynomial-time solvable) problems has been a particularly important goal for researchers in the area. The reason behind this is not only to differentiate between easy and hard planning instances, but also to use polynomial-time solvable instances in order to construct better heuristic functions and improve planners. We identify a new class of tractable cost-optimal planning instances by restricting the causal graph. We study the computational complexity of oversubscription planning (such as the net-benefit problem) under various restrictions and reveal strong connections with classical planning. Inspired by this, we present a method for compiling oversubscription planning problems into the ordinary plan existence problem. We further study the parameterized complexity of cost-optimal and net-benefit planning under the same restrictions and show that the choice of numeric domain for the action costs has a great impact on the parameterized complexity. We finally consider the parameterized complexity of certain problems related to partial-order planning. In some applications, less restricted plans than total-order plans are needed. Therefore, a partial-order plan is being used instead. When dealing with partial-order plans, one important question is how to achieve optimal partial order plans, i.e. having the highest degree of freedom according to some notion of flexibility. We study several optimization problems for partial-order plans, such as finding a minimum deordering or reordering, and finding the minimum parallel execution length.

    Delarbeten
    1. Oversubscription planning: Complexity and compilability
    Öppna denna publikation i ny flik eller fönster >>Oversubscription planning: Complexity and compilability
    2014 (Engelska)Ingår i: Proceedings of the Twenty-Eighth AAAI Conference on Artificial Intelligence, AI Access Foundation , 2014, Vol. 3, s. 2221-2227Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    Many real-world planning problems are oversubscription problems where all goals are not simultaneously achievable and the planner needs to find a feasible subset. We present complexity results for the so-called partial satisfaction and net benefit problems under various restrictions; this extends previous work by van den Briel et al. Our results reveal strong connections between these problems and with classical planning. We also present a method for efficiently compiling oversubscription problems into the ordinary plan existence problem; this can be viewed as a continuation of earlier work by Keyder and Geffner.

    Ort, förlag, år, upplaga, sidor
    AI Access Foundation, 2014
    Nationell ämneskategori
    Data- och informationsvetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-116727 (URN)000485439702031 ()2-s2.0-84908192348 (Scopus ID)9781577356790 (ISBN)
    Konferens
    28th AAAI Conference on Artificial Intelligence, AAAI 2014, 26th Innovative Applications of Artificial Intelligence Conference, IAAI 2014 and the 5th Symposium on Educational Advances in Artificial Intelligence, EAAI 2014
    Tillgänglig från: 2015-04-09 Skapad: 2015-04-02 Senast uppdaterad: 2020-06-29
    2. Tractable Cost-Optimal Planning over Restricted Polytree Causal Graphs
    Öppna denna publikation i ny flik eller fönster >>Tractable Cost-Optimal Planning over Restricted Polytree Causal Graphs
    2015 (Engelska)Ingår i: Proceedings of the Twenty-Ninth AAAI Conference on Artificial Intelligence, AAAI Press, 2015Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    Causal graphs are widely used to analyze the complexity of planning problems. Many tractable classes have been identified with their aid and state-of-the-art heuristics have been derived by exploiting such classes. In particular, Katz and Keyder have studied causal graphs that are hourglasses (which is a generalization of forks and inverted-forks) and shown that the corresponding cost-optimal planning problem is tractable under certain restrictions. We continue this work by studying polytrees (which is a generalization of hourglasses) under similar restrictions. We prove tractability of cost-optimal planning by providing an algorithm based on a novel notion of variable isomorphism. Our algorithm also sheds light on the k-consistency procedure for identifying unsolvable planning instances. We speculate that this may, at least partially, explain why merge-and-shrink heuristics have been successful for recognizing unsolvable instances.

    Ort, förlag, år, upplaga, sidor
    AAAI Press, 2015
    Serie
    Proceedings of the AAAI Conference on Artificial Intelligence, ISSN 2159-5399, E-ISSN 2374-3468
    Nyckelord
    automated planning, causal graph, polynomial-time algorithm, cost-optimal planning, polytree
    Nationell ämneskategori
    Datorsystem
    Identifikatorer
    urn:nbn:se:liu:diva-118729 (URN)000485625503038 ()978-1-57735-703-2 (ISBN)
    Konferens
    29th AAAI Conference on Artificial Intelligence (AAAI-15), January 25–30, Austin, TX, USA
    Forskningsfinansiär
    CUGS (National Graduate School in Computer Science)
    Tillgänglig från: 2015-06-03 Skapad: 2015-06-03 Senast uppdaterad: 2022-02-18
    3. Cost-optimal and Net-benefit Planning: A Parameterised Complexity View
    Öppna denna publikation i ny flik eller fönster >>Cost-optimal and Net-benefit Planning: A Parameterised Complexity View
    2015 (Engelska)Ingår i: 24th International Joint Conference on Artificial Intelligence (IJCAI-15), IJCAI-INT JOINT CONF ARTIF INTELL, ALBERT-LUDWIGS UNIV FREIBURG GEORGES-KOHLER-ALLEE, INST INFORMATIK, GEB 052, FREIBURG, D-79110, GERMANY , 2015, s. 1487-1493Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    Cost-optimal planning (COP) uses action costs and asks for a minimum-cost plan. It is sometimes assumed that there is no harm in using actions with zero cost or rational cost. Classical complexity analysis does not contradict this assumption; planning is PSPACE-complete regardless of whether action costs are positive or non-negative, integer or rational. We thus apply parameterised complexity analysis to shed more light on this issue. Our main results are the following. COP is W[2]-complete for positive integer costs, i.e. it is no harder than finding a minimum-length plan, but it is para-NPhard if the costs are non-negative integers or positive rationals. This is a very strong indication that the latter cases are substantially harder. Net-benefit planning (NBP) additionally assigns goal utilities and asks for a plan with maximum difference between its utility and its cost. NBP is para-NP-hard even when action costs and utilities are positive integers, suggesting that it is harder than COP. In addition, we also analyse a large number of subclasses, using both the PUBS restrictions and restricting the number of preconditions and effects.

    Ort, förlag, år, upplaga, sidor
    IJCAI-INT JOINT CONF ARTIF INTELL, ALBERT-LUDWIGS UNIV FREIBURG GEORGES-KOHLER-ALLEE, INST INFORMATIK, GEB 052, FREIBURG, D-79110, GERMANY, 2015
    Nationell ämneskategori
    Transportteknik och logistik
    Identifikatorer
    urn:nbn:se:liu:diva-128181 (URN)000442637801080 ()9781577357384 (ISBN)
    Konferens
    24th International Joint Conference on Artificial Intelligence (IJCAI-15), Buenos Aires, Argentina, Jul 25-31, 2015
    Forskningsfinansiär
    CUGS (National Graduate School in Computer Science), 1054Vetenskapsrådet, 621- 2014-4086
    Tillgänglig från: 2016-05-20 Skapad: 2016-05-20 Senast uppdaterad: 2019-07-03Bibliografiskt granskad
    4. A Multi-parameter Complexity Analysis of Cost-optimal and Net-benefit Planning
    Öppna denna publikation i ny flik eller fönster >>A Multi-parameter Complexity Analysis of Cost-optimal and Net-benefit Planning
    2016 (Engelska)Ingår i: Twenty-Sixth International Conference on Automated Planning and Scheduling King's College, London June 12, 2016 – June 17, 2016 / [ed] Amanda Coles, Andrew Coles, Stefan Edelkamp, Daniele Magazzeni, Scott Sanner, AAAI Press, 2016, s. 2-10Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    Aghighi and Bäckström have previously studied cost-optimal planning (COP) and net-benefit planning (NBP) for three action cost domains: the positive integers (Z_+), the non-negative integers (Z_0) and the positive rationals (Q_+). These were indistinguishable under standard complexity analysis for both problems, but separated for COP using parameterised complexity analysis. With the plan cost, k, as parameter, COP was W[2]-complete for Z_+, but para-NP-hard for both Z_0 and Q_+, i.e. presumably much harder. NBP was para-NP-hard for all three domains, thus remaining unseparable. We continue by considering combinations with several additional parameters and also the non-negative rationals (Q_0). Examples of new parameters are the plan length, l, and the largest denominator of the action costs, d. Our findings include: (1) COP remains W[2]-hard for all domains, even if combining all parameters; (2) COP for Z_0 is in W[2] for the combined parameter {k,l}; (3) COP for Q_+ is in W[2] for {k,d} and (4) COP for Q_0 is in W[2] for {k,d,l}. For NBP we consider further additional parameters, where the most crucial one for reducing complexity is the sum of variable utilities. Our results help to understand the previous results, eg. the separation between Z_+ and Q_+ for COP, and to refine the previous connections with empirical findings.

    Ort, förlag, år, upplaga, sidor
    AAAI Press, 2016
    Nyckelord
    cost-optimal planning, parameterised complexity, numeric domains
    Nationell ämneskategori
    Datorsystem
    Identifikatorer
    urn:nbn:se:liu:diva-136278 (URN)000492982200001 ()9781577357575 (ISBN)
    Konferens
    Twenty-Sixth International Conference on Automated Planning and Scheduling (ICAPS-16), London, UK, June 12–17, 2016
    Tillgänglig från: 2017-04-05 Skapad: 2017-04-05 Senast uppdaterad: 2020-06-29Bibliografiskt granskad
    5. Plan Reordering and Parallel Execution -- A Parameterized Complexity View
    Öppna denna publikation i ny flik eller fönster >>Plan Reordering and Parallel Execution -- A Parameterized Complexity View
    2017 (Engelska)Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    Bäckström has previously studied a number of optimization problems for partial-order plans, like finding a minimum deordering (MCD) or reordering (MCR), and finding the minimum parallel execution length (PPL), which are all NP-complete. We revisit these problems, but applying parameterized complexity analysis rather than standard complexity analysis. We consider various parameters, including both the original and desired size of the plan order, as well as its width and height. Our findings include that MCD and MCR are W[2]-hard and in W[P] when parameterized with the desired order size, and MCD is fixed-parameter tractable (fpt) when parameterized with the original order size. Problem PPL is fpt if parameterized with the size of the non-concurrency relation, but para-NP-hard in most other cases. We also consider this problem when the number (k) of agents, or processors, is restricted, finding that this number is a crucial parameter; this problem is fixed-parameter tractable with the order size, the parallel execution length and k as parameter, but para-NP-hard without k as parameter.

    Ort, förlag, år, upplaga, sidor
    AAAI Press, 2017
    Nyckelord
    Partially ordered plan, Parameterized complexity, Complexity of planning, Plan reordering, Parallel plan execution
    Nationell ämneskategori
    Datorsystem
    Identifikatorer
    urn:nbn:se:liu:diva-136279 (URN)000485630703082 ()
    Konferens
    Thirty-First AAAI Conference on Artificial Intelligence (AAAI-17)
    Tillgänglig från: 2017-04-05 Skapad: 2017-04-05 Senast uppdaterad: 2020-06-29Bibliografiskt granskad
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  • 4.
    Aghighi, Meysam
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Bäckström, Christer
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    A Multi-parameter Complexity Analysis of Cost-optimal and Net-benefit Planning2016Ingår i: Twenty-Sixth International Conference on Automated Planning and Scheduling King's College, London June 12, 2016 – June 17, 2016 / [ed] Amanda Coles, Andrew Coles, Stefan Edelkamp, Daniele Magazzeni, Scott Sanner, AAAI Press, 2016, s. 2-10Konferensbidrag (Refereegranskat)
    Abstract [en]

    Aghighi and Bäckström have previously studied cost-optimal planning (COP) and net-benefit planning (NBP) for three action cost domains: the positive integers (Z_+), the non-negative integers (Z_0) and the positive rationals (Q_+). These were indistinguishable under standard complexity analysis for both problems, but separated for COP using parameterised complexity analysis. With the plan cost, k, as parameter, COP was W[2]-complete for Z_+, but para-NP-hard for both Z_0 and Q_+, i.e. presumably much harder. NBP was para-NP-hard for all three domains, thus remaining unseparable. We continue by considering combinations with several additional parameters and also the non-negative rationals (Q_0). Examples of new parameters are the plan length, l, and the largest denominator of the action costs, d. Our findings include: (1) COP remains W[2]-hard for all domains, even if combining all parameters; (2) COP for Z_0 is in W[2] for the combined parameter {k,l}; (3) COP for Q_+ is in W[2] for {k,d} and (4) COP for Q_0 is in W[2] for {k,d,l}. For NBP we consider further additional parameters, where the most crucial one for reducing complexity is the sum of variable utilities. Our results help to understand the previous results, eg. the separation between Z_+ and Q_+ for COP, and to refine the previous connections with empirical findings.

    Ladda ner fulltext (pdf)
    A Multi-parameter Complexity Analysis of Cost-optimal and Net-benefit Planning
  • 5.
    Aghighi, Meysam
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Bäckström, Christer
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Plan Reordering and Parallel Execution -- A Parameterized Complexity View2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    Bäckström has previously studied a number of optimization problems for partial-order plans, like finding a minimum deordering (MCD) or reordering (MCR), and finding the minimum parallel execution length (PPL), which are all NP-complete. We revisit these problems, but applying parameterized complexity analysis rather than standard complexity analysis. We consider various parameters, including both the original and desired size of the plan order, as well as its width and height. Our findings include that MCD and MCR are W[2]-hard and in W[P] when parameterized with the desired order size, and MCD is fixed-parameter tractable (fpt) when parameterized with the original order size. Problem PPL is fpt if parameterized with the size of the non-concurrency relation, but para-NP-hard in most other cases. We also consider this problem when the number (k) of agents, or processors, is restricted, finding that this number is a crucial parameter; this problem is fixed-parameter tractable with the order size, the parallel execution length and k as parameter, but para-NP-hard without k as parameter.

  • 6.
    Aghighi, Meysam
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Jonsson, Peter
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Ståhlberg, Simon
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Tractable Cost-Optimal Planning over Restricted Polytree Causal Graphs2015Ingår i: Proceedings of the Twenty-Ninth AAAI Conference on Artificial Intelligence, AAAI Press, 2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    Causal graphs are widely used to analyze the complexity of planning problems. Many tractable classes have been identified with their aid and state-of-the-art heuristics have been derived by exploiting such classes. In particular, Katz and Keyder have studied causal graphs that are hourglasses (which is a generalization of forks and inverted-forks) and shown that the corresponding cost-optimal planning problem is tractable under certain restrictions. We continue this work by studying polytrees (which is a generalization of hourglasses) under similar restrictions. We prove tractability of cost-optimal planning by providing an algorithm based on a novel notion of variable isomorphism. Our algorithm also sheds light on the k-consistency procedure for identifying unsolvable planning instances. We speculate that this may, at least partially, explain why merge-and-shrink heuristics have been successful for recognizing unsolvable instances.

  • 7.
    Ahlgren, Simon
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    Aini, Daniel
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    Conversion and Analysis of Telemetric Data from the CCSDS Standard2017Självständigt arbete på grundnivå (högskoleexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
    Abstract [en]

    When communicating with spacecrafts, the international standard is to use the protocols defined by CCSDS. In this study, the Space Packet Protocol from CCSDS is converted to the Digital Recording Standard used in aviation. The goal of the study is to find out in what way such a conversion can be made, as well as analyzing the efficiency of different packing methods for the Digital Recording Standard. An application is developed in order to perform the conversion, and the performance of said application is profiled using different packet sizes. In the end the results are evaluated and an optimal packet size is found in terms of runtime and memory usage. In the end we conclude that a packet size of 216 bytes is best when prioritizing speed, and a packet size of 219 bytes is best when prioritizing memory.

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  • 8.
    Ahlqvist, Axel
    Linköpings universitet, Institutionen för systemteknik, Datorseende.
    Examining Difficulties in Weed Detection2022Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Automatic detection of weeds could be used for more efficient weed control in agriculture. In this master thesis, weed detectors have been trained and examined on data collected by RISE to investigate whether an accurate weed detector could be trained on the collected data. When only using annotations of the weed class Creeping thistle for training and evaluation, a detector achieved a mAP of 0.33. When using four classes of weed, a detector was trained with a mAP of 0.07. The performance was worse than in a previous study also dealing with weed detection. Hypotheses for why the performance was lacking were examined. Experiments indicated that the problem could not fully be explained by the model being underfitted, nor by the object’s backgrounds being too similar to the foreground, nor by the quality of the annotations being too low. The performance was better when training the model with as much data as possible than when only selected segments of the data were used.

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  • 9.
    Ahmad, Fozail
    et al.
    McGill Univ, Canada.
    Rangappa, Maruthi
    McGill Univ, Canada.
    Katiyar, Neeraj
    McGill Univ, Canada.
    Staniszewski, Martin
    Siemens Energy, Canada.
    Varro, Daniel
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten. McGill Univ, Canada.
    Hybrid Cloudification of Legacy Software for Efficient Simulation of Gas Turbine Designs2023Ingår i: 2023 IEEE/ACM 45TH INTERNATIONAL CONFERENCE ON SOFTWARE ENGINEERING: SOFTWARE ENGINEERING IN PRACTICE, ICSE-SEIP, IEEE COMPUTER SOC , 2023, s. 384-395Konferensbidrag (Refereegranskat)
    Abstract [en]

    When developing aeroderivative gas turbines at Siemens Energy, engine models are subject to complex simulation campaigns for finite element analysis carried out by a legacy simulation tool. This paper presents results of a multi-year software modernization project to provide a software-as-a-service (SaaS) framework that enables the distributed and automated execution of simulation jobs over a hybrid cloud platform containing both private cloud and public cloud nodes. Our framework allows to significantly reduce the net time required for completing complex simulation campaigns, thus increasing the effectiveness of engineers. The performance of our framework is evaluated in various cloud configurations with complex simulation campaigns performed in the context of a real simulation task.

  • 10.
    Ahmad, Ijaz
    et al.
    VTT Tech Res Ctr Finland, Finland.
    Shahabuddin, Shariar
    Nokia, Finland.
    Malik, Hassan
    Edge Hill Univ, England.
    Harjula, Erkki
    Univ Oulu, Finland.
    Leppanen, Teemu
    Univ Oulu, Finland.
    Loven, Lauri
    Univ Oulu, Finland.
    Anttonen, Antti
    VTT Tech Res Ctr Finland, Finland.
    Sodhro, Ali Hassan
    Mid Sweden Univ, Sweden.
    Mahtab Alam, Muhammad
    Tallinn Univ Technol, Estonia.
    Juntti, Markku
    Univ Oulu, Finland.
    Yla-Jaaski, Antti
    Aalto Univ, Finland.
    Sauter, Thilo
    TU Wien, Austria; Danube Univ Krems, Austria.
    Gurtov, Andrei
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Ylianttila, Mika
    Univ Oulu, Finland.
    Riekki, Jukka
    Univ Oulu, Finland.
    Machine Learning Meets Communication Networks: Current Trends and Future Challenges2020Ingår i: IEEE Access, E-ISSN 2169-3536, Vol. 8, s. 223418-223460Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The growing network density and unprecedented increase in network traffic, caused by the massively expanding number of connected devices and online services, require intelligent network operations. Machine Learning (ML) has been applied in this regard in different types of networks and networking technologies to meet the requirements of future communicating devices and services. In this article, we provide a detailed account of current research on the application of ML in communication networks and shed light on future research challenges. Research on the application of ML in communication networks is described in: i) the three layers, i.e., physical, access, and network layers; and ii) novel computing and networking concepts such as Multi-access Edge Computing (MEC), Software Defined Networking (SDN), Network Functions Virtualization (NFV), and a brief overview of ML-based network security. Important future research challenges are identified and presented to help stir further research in key areas in this direction.

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  • 11.
    Ahmad, Ijaz
    et al.
    VTT Tech Res Ctr Finland, Finland.
    Suomalainen, Jani
    VTT Tech Res Ctr Finland, Finland.
    Porambage, Pawani
    VTT Tech Res Ctr Finland, Finland; Univ Oulu, Finland.
    Gurtov, Andrei
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Huusko, Jyrki
    VTT Tech Res Ctr Finland, Finland.
    Höyhtyä, Marko
    VTT Tech Res Ctr Finland, Finland.
    Security of Satellite-Terrestrial Communications: Challenges and Potential Solutions2022Ingår i: IEEE Access, E-ISSN 2169-3536, Vol. 10, s. 96038-96052Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The integration of satellite and terrestrial networks has become inevitable in the next generations of communications networks due to emerging needs of ubiquitous connectivity of remote locations. New and existing services and critical infrastructures in remote locations in sea, on land and in space will be seamlessly connected through a diverse set of terrestrial and non-terrestrial communication technologies. However, the integration of terrestrial and non-terrestrial systems will open up both systems to unique security challenges that can arise due to the migration of security challenges from one to another. Similarly, security challenges can also arise due to the incompatibility of distinct systems or incoherence of security policies. The resulting security implications, thus, can be highly consequential due to the criticality of the infrastructures such as space stations, autonomous ships, and airplanes, for instance. Therefore, in this article we study existing security challenges in satellite-terrestrial communication systems and discuss potential solutions for those challenges. Furthermore, we provide important research directions to encourage future research on existing security gaps.

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  • 12.
    Al-egli, Muntaher
    et al.
    Linköpings universitet, Institutionen för datavetenskap.
    Zeidan Nasser, Adham
    Linköpings universitet, Institutionen för datavetenskap.
    Identifiering av anomalier i COSMIC genom analys av loggar2015Självständigt arbete på grundnivå (högskoleexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Loggar är en viktig del av alla system, det ger en inblick i vad som sker. Att analysera loggar och extrahera väsentlig information är en av de största trenderna nu inom IT-branchen. Informationen i loggar är värdefulla resurser som kan användas för att upptäcka anomalier och hantera dessa innan det drabbar användaren.

    I detta examensarbete dyker vi in i grunderna för informationssökning och analysera undantagsutskrifter i loggar från COSMIC för att undersöka om det är möjligt att upptäcka anomalier med hjälp av retrospektivdata. Detta examensarbete ger även en inblick i möjligheten att visualisera data från loggar och erbjuda en kraftfull sökmotor. Därför kommer vi att fördjupa oss i de tre välkända program som adresserar frågorna i centraliserad loggning: Elasticsearch, Logstash och Kibana.

    Sammanfattningsvis visar resultatet att det är möjligt att upptäckta anomalier genom att tillämpa statistiska metoder både på retrospektiv- och realtidsdata.

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  • 13.
    Alhowaidi, Mohammad
    Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system. Linköpings universitet, Tekniska högskolan.
    Real-Time Systems with Radiation-Hardened Processors: A GPU-based Framework to Explore Tradeoffs2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Radiation-hardened processors are designed to be resilient against soft errorsbut such processors are slower than Commercial Off-The-Shelf (COTS)processors as well significantly costlier. In order to mitigate the high costs,software techniques such as task re-executions must be deployed together withadequately hardened processors to provide reliability. This leads to a huge designspace comprising of the hardening level of the processors and the numberof re-executions of each task in the system. Each configuration in this designspace represents a tradeoff between processor load, reliability and costs.

    The reliability comes at the price of higher costs due to higher levels of hardeningand performance degradation due to hardening or due to re-executions.Thus, the tradeoffs between performance, reliability and costs must be carefullystudied. Pertinent questions that arise in such a design scenario are — (i)how many times a task must be re-executed and (ii) what should be hardeninglevel? — such that the system reliability is satisfied.

    In order to evaluate such tradeoffs efficiently, in this thesis, we proposenovel framework that harnesses the computational power of Graphics ProcessingUnits (GPUs). Our framework is based on a system failure probabilityanalysis that connects the probability of failure of tasks to the overall systemreliability. Based on characteristics of this probabilistic analysis as well asreal-time deadlines, we derive bounds on the design space to prune infeasiblesolutions. Finally, we illustrate the benefits of our proposed framework withseveral experiments

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  • 14.
    Ali, Akhtar
    et al.
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Dastgeer, Usman
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Kessler, Christoph
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    OpenCL for programming shared memory multicore CPUs2011Ingår i: Fourth Swedish Workshop on Multi-Core Computing MCC-2011: November 23-25, 2011, Linköping University, Linköping, Sweden / [ed] Christoph Kessler, Linköping: Linköping University , 2011, Vol. S. 65-70, s. 65-70Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    In this work, we evaluate the effectiveness of OpenCL for programming multicore CPUs in a comparative case study with OpenMP and Intel TBB for five benchmark applications: matrix multiply, LU decomposition, 2D image convolution, Pi value approximation and image histogram generation.

  • 15.
    Ali Mousa, Mohammad
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    Nguyen, Bertil
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    Prestandaeffektivisering av webbapplikation för journalföring2021Självständigt arbete på grundnivå (högskoleexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Webbapplikationer är ett smidigt sätt för företag att effektivisera sina tjänster. Det finns flera faktorer som utgör användarens intryck av webbapplikationen. I detta arbete kommer vi att fördjupa oss inom prestanda. I detta arbete kommer en journalföringsapplikation implementeras för att sedan applicera prefetching och cacheing på denna webbapplikation. För att få insikt över huruvida dessa tekniker påverkade applikationen positivt mättes implementationerna med optimeringar separat från grundimplementationen. Resultatet visar på att både cacheing och prefetching hade positiv effekt på prestandan I webbapplikationen. Däremot finner vi att det är viktigt att klargöra vad man vill cachea och prefetcha eftersom i vår implementation av dessa optimeringstekniker får en bättre presterande applikation på bekostnad av användarvänlighet. 

  • 16.
    Almgren, Magnus
    et al.
    Department of computer science and engineering, Chalmers university of technology, Gothenburg.
    Andersson, Peter
    FOI, Swedish Defence Research Agency, Linköping, Sweden.
    Björkman, Gunnar
    Stockholms stad / Kungliga Tekniska Högskolan, KTH, Stockholm.
    Ekstedt, Mathias
    Industrial Information and Control Systems, Royal Institute of Technology, KTH, Stockholm.
    Hallberg, Jonas
    FOI, Swedish Defence Research Agency, Linköping, Sweden.
    Nadjm-Tehrani, Simin
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Westring, Eric
    FOI, Swedish Defence Research Agency, Linköping, Sweden.
    RICS-el: Building a National Testbed for Research and Training on SCADA Security2019Ingår i: Critical Information Infrastructures Security: 13th International Conference, CRITIS 2018, Kaunas, Lithuania, September 24-26, 2018, Revised Selected Papers / [ed] Eric Luiijf, Inga Žutautaitė and Bernhard Hämmerli, Springer, 2019, s. 219-225Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Trends show that cyber attacks targeting critical infrastructures are increasing, but security research for protecting such systems are challenging. There is a gap between the somewhat simplified models researchers at universities can sustain contra the complex systems at infrastructure owners that seldom can be used for direct research. There is also a lack of common datasets for research benchmarking. This paper presents a national experimental testbed for security research within supervisory control and data acquisition systems (SCADA), accessible for both research training and experiments. The virtualized testbed has been designed and implemented with both vendor experts and security researchers to balance the goals of realism with specific research needs. It includes a real SCADA product for energy management, a number of network zones, substation nodes, and a simulated power system. This environment enables creation of scenarios similar to real world utility scenarios, attack generation, development of defence mechanisms, and perhaps just as important: generating open datasets for comparative research evaluation.

  • 17.
    Almquist, Mathias
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Almquist, Viktor
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    A study on Android games: 3G energy consumption, CPU-utilization and system calls2015Självständigt arbete på grundnivå (högskoleexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The popularity of mobile games has increased drastically during the recent years andmany people use them as their main source of entertainment. Mobile gamescommunicate with other devices over the network which consumes a lot of energy,especially when connected to cellular networks (e.g., 3G). This high energy expensecan feel unjustified to the player since always-on network connectivity is not requiredin order to play most games.Furthermore, the number of malware-infected applications in offical applicationstores has increased significantly in the recent years. These malware-infectedapplications can gain unrestricted access and control of users phones which can be athreat to security. Information about the behaviour characteristics of games can beused to develop or improve systems for detecting malware applications.In this thesis, 20 popular Android games are analysed with a focus on the datacommunication, CPU utilization and system call behaviour. The main subject of thedata communication study is the 3G communication energy consumed by games. Thesystem call study aims at quantifying the number and type of calls used by games.This may be useful in a further study of harmful behaviour by apps.The profiling results presented in this report show that the communication energyvaries drastically among games. Games with a very similar gameplay can consumevery different amounts of energy which indicates that there is room for improvementsin many of the games. Ad-free games consume significantly less energy than gamesthat use in-app advertisements. The results show that improving the advertisementfetching policy could reduce the energy consumption of these games. The majority ofthe games can be played without network connectivity and therefore thecommunication energy consumed could be completely avoided. The thesis alsoshows that games use a wide variety of system calls and that many of the system callsare common among the games.

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  • 18.
    Almquist, Mathias
    et al.
    Linköpings universitet, Institutionen för datavetenskap.
    Almquist, Viktor
    Linköpings universitet, Institutionen för datavetenskap.
    Analysis of 360° Video Viewing Behaviours2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In this thesis we study users' viewing motions when watching 360° videos in order to provide information that can be used to optimize future view-dependent streaming protocols. More specifically, we develop an application that plays a sequence of 360° videos on an Oculus Rift Head Mounted Display and records the orientation and rotation velocity of the headset during playback. The application is used during an extensive user study in order to collect more than 21 hours of viewing data which is then analysed to expose viewing patterns, useful for optimizing 360° streaming protocols. 

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  • 19.
    Almqvist, Tom
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    Utvärdering av metoder för temporär lagring av data i en webbapplikation2018Självständigt arbete på grundnivå (högskoleexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    I databasapplikationer är det viktigt att kunna minska belastningen på en databas i syfte att minska responstiden. Detta kan exempelvis åstadkommas med hjälp av olika metoder för temporär lagring av data, något som studerats i detta arbete. De metoder som utvärderats och jämförts i detta arbete är Redis och memcached. Utvärderingen jämförde Redis och memcached med avseende på minnesanvändning, CPU-användning och tidsåtgång för hämtning av data i respektive cache. Dessa egenskaper beräknades med hjälp av verktygen SYSSTAT och valgrind. Det visade sig i slutändan att den interna fragmenteringen i memcached är dess största nackdel, medan Redis är något långsammare än memcached när det gäller att hämta stora mängder data. Utifrån de resultat som anskaffats var det tänkt att använda den metod som är mest lämpad för SysPartners ändamål, vilket ansågs vara Redis.

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  • 20.
    Alnervik, Erik
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Evaluation of the Configurable Architecture REPLICA with Emulated Shared Memory2014Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    REPLICA är en grupp av konfigurerbara multiprocessorer som med hjälp utav ett emulerat delat minne realiserar PRAM modellen.

    Syftet med denna avhandling är att genom benchmarking av olika beräkningsproblem på REPLICA, liknande (SB-PRAM och XMT) och mindre lika (Xeon X5660 och Tesla M2050) parallella arkitekturer, utvärdera hur REPLICA står sig mot andra befintliga arkitekturer. Både prestandamässigt och hur enkel arkitekturen är att programmera effektiv, men även försöka ta reda på om REPLICA är speciellt lämpad för några särskilda typer av beräkningsproblem.

    Genom att använda välkända Berkeley dwarfs applikationer och opartisk indata från bland annat The University of Florida Sparse Matrix Collection och Rodinia benchmark suite, säkerställer vi att det är relevanta beräkningsproblem som utförs och mäts.

    Vi visar att dagens parallella arkitekturer har problem med prestandan för applikationer med oregelbundna minnesaccessmönster, vilken REPLICA arkitekturen kan vara en lösning på. Till exempel, så behöver REPLICA endast vara klockad med några få MHz för att matcha både Xeon X5660 och Tesla M2050 för algoritmen breadth first search, vilken lider av just oregelbunden minnesåtkomst. Genom att jämföra effektiviteten för REPLICA gentemot en CPU (Xeon X5660), visar vi att det är lättare att programmera REPLICA effektivt än dagens multiprocessorer.

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  • 21.
    Al-Trad, Anas
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Optimized Composition of Parallel Components on a Linux Cluster2012Självständigt arbete på avancerad nivå (masterexamen), 30 poäng / 45 hpStudentuppsats (Examensarbete)
    Abstract [en]

    We develop a novel framework for optimized composition of explicitly parallel software components with different implementation variants given the problem size, data distribution scheme and processor group size on a Linux cluster. We consider two approaches (or two cases of the framework). 

    In the first approach, dispatch tables are built using measurement data obtained offline by executions for some (sample) points in the ranges of the context properties. Inter-/extrapolation is then used to do actual variant-selection for a given execution context at run-time.

    In the second approach, a cost function of each component variant is provided by the component writer for variant-selection. These cost functions can internally lookup measurements' tables built, either offline or at deployment time, for computation- and communication-specific primitives.

    In both approaches, the call to an explicitly parallel software component (with different implementation variants) is made via a dispatcher instead of calling a variant directly.

    As a case study, we apply both approaches on a parallel component for matrix multiplication with multiple implementation variants. We implemented our variants using Message Passing Interface (MPI). The results show the reduction in execution time for the optimally composed applications compared to applications with hard-coded composition. In addition, the results show the comparison of estimated and measured times for each variant using different data distributions, processor group and problem sizes.

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  • 22.
    Alvila, Markus
    et al.
    Linköpings universitet, Institutionen för datavetenskap.
    Johansson, Jonathan
    Linköpings universitet, Institutionen för datavetenskap.
    Johansson, Philip
    Linköpings universitet, Institutionen för datavetenskap.
    Lenz, Silas
    Linköpings universitet, Institutionen för datavetenskap.
    Lindmark, Sebastian
    Linköpings universitet, Institutionen för datavetenskap.
    Norberg, Emil
    Linköpings universitet, Institutionen för datavetenskap.
    Regard, Viktor
    Linköpings universitet, Institutionen för datavetenskap.
    Övervakning och bedömning av flygledares prestanda2017Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Möjligheten att fjärrstyra flygledartorn kommer att ställa högre krav på flygledares koncentrations- och simultanförmåga runt om i Sverige. Det är viktigt att åtgärder tas för att förhindra att en trött flygledare begår ett misstag och det är just detta som det framtagna systemet försöker att förhindra.

    Med hjälp av sensorer och modeller kan systemet bestämma flygledarens trötthet, stressnivå, uppmärksamhet och nuvarande arbetsuppgift. Alla värden presenteras i ett enkelt grafiskt gränssnitt. Tillsammans med resultaten för flygledarens hälsa presenteras även all sensordata i gränssnittet.

    Systemet är främst uppbyggt av två olika ramverk: Apache NiFi och Apache Spark. Vad de båda ramverken har gemensamt är att de har funktionalitet för att bygga kluster, vilket betyder att endast antalet noder sätter gränsen för hur många flygledare som kan vara uppkopplade samtidigt.

    Denna prototyp har inte all funktionalitet på plats för att behandla flera flygledare. Grunden är däremot lagd för att enkelt kunna implementera ytterligare funktionalitet och i slutändan ha flera flygledare uppkopplade samtidigt. Systemet öppnar upp möjligheter till att fördela arbetet på de flygledare som är mest fokuserade och kan därför bidra till att öka flygsäkerheten.

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  • 23. Beställ onlineKöp publikationen >>
    Aminifar, Amir
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Analysis, Design, and Optimization of Embedded Control Systems2016Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    Today, many embedded or cyber-physical systems, e.g., in the automotive domain, comprise several control applications, sharing the same platform. It is well known that such resource sharing leads to complex temporal behaviors that degrades the quality of control, and more importantly, may even jeopardize stability in the worst case, if not properly taken into account.

    In this thesis, we consider embedded control or cyber-physical systems, where several control applications share the same processing unit. The focus is on the control-scheduling co-design problem, where the controller and scheduling parameters are jointly optimized. The fundamental difference between control applications and traditional embedded applications motivates the need for novel methodologies for the design and optimization of embedded control systems. This thesis is one more step towards correct design and optimization of embedded control systems.

    Offline and online methodologies for embedded control systems are covered in this thesis. The importance of considering both the expected control performance and stability is discussed and a control-scheduling co-design methodology is proposed to optimize control performance while guaranteeing stability. Orthogonal to this, bandwidth-efficient stabilizing control servers are proposed, which support compositionality, isolation, and resource-efficiency in design and co-design. Finally, we extend the scope of the proposed approach to non-periodic control schemes and address the challenges in sharing the platform with self-triggered controllers. In addition to offline methodologies, a novel online scheduling policy to stabilize control applications is proposed.

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  • 24.
    Aminifar, Amir
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Self-Triggered Controllers, Resource Sharing, and Hard Guarantees2016Ingår i: 2016 2ND INTERNATIONAL CONFERENCE ON EVENT-BASED CONTROL, COMMUNICATION, AND SIGNAL PROCESSING (EBCCSP), IEEE , 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    Today, many control applications in embedded and cyber-physical systems are implemented on shared platforms, alongside other hard real-time or safety-critical applications. Having the resource shared among several applications, to provide hard guarantees, it is required to identify the amount of resource needed for each application. This is rather straightforward when the platform is shared among periodic control and periodic real-time applications. In the case of event-triggered and self-triggered controllers, however, the execution patterns and, in turn, the resource usage are not clear. Therefore, a major implementation challenge, when the platform is shared with self-triggered controllers, is to provide hard and efficient stability and schedulability guarantees for other applications. In this paper, we identify certain execution patterns for self-triggered controllers, using which we are able to provide hard and efficient stability guarantees for periodic control applications.

  • 25.
    Amlinger, Anton
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    An Evaluation of Clustering and Classification Algorithms in Life-Logging Devices2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Using life-logging devices and wearables is a growing trend in today’s society. These yield vast amounts of information, data that is not directly overseeable or graspable at a glance due to its size. Gathering a qualitative, comprehensible overview over this quantitative information is essential for life-logging services to serve its purpose.

    This thesis provides an overview comparison of CLARANS, DBSCAN and SLINK, representing different branches of clustering algorithm types, as tools for activity detection in geo-spatial data sets. These activities are then classified using a simple model with model parameters learned via Bayesian inference, as a demonstration of a different branch of clustering.

    Results are provided using Silhouettes as evaluation for geo-spatial clustering and a user study for the end classification. The results are promising as an outline for a framework of classification and activity detection, and shed lights on various pitfalls that might be encountered during implementation of such service.

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  • 26.
    Anders, Söderholm
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    Justus, Sörman
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    GPU-accelleration of image rendering and sorting algorithms with the OpenCL framework2016Självständigt arbete på grundnivå (högskoleexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Today's computer systems often contains several different processing units aside from the CPU. Among these the GPU is a very common processing unit with an immense compute power that is available in almost all computer systems. How do we make use of this processing power that lies within our machines? One answer is the OpenCL framework that is designed for just this, to open up the possibilities of using all the different types of processing units in a computer system. This thesis will discuss the advantages and disadvantages of using the integrated GPU available in a basic workstation computer for computation of image processing and sorting algorithms. These tasks are computationally intensive and the authors will analyze if an integrated GPU is up to the task of accelerating the processing of these algorithms. The OpenCL framework makes it possible to run one implementation on different processing units, to provide perspective we will benchmark our implementations on both the GPU and the CPU and compare the results. A heterogeneous approach that combines the two above mentioned processing units will also be tested and discussed. The OpenCL framework is analyzed from a development perspective and what advantages and disadvantages it brings to the development process will be presented.

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  • 27. Beställ onlineKöp publikationen >>
    Andersson, Anders
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska fakulteten. Statens väg- och transportforskningsinstitut (VTI), Trafik och trafikant,TRAF, Fordonsteknik och simulering, FTS, Linköping, Sweden.
    Distributed Moving Base Driving Simulators: Technology, Performance, and Requirements2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Development of new functionality and smart systems for different types of vehicles is accelerating with the advent of new emerging technologies such as connected and autonomous vehicles. To ensure that these new systems and functions work as intended, flexible and credible evaluation tools are necessary. One example of this type of tool is a driving simulator, which can be used for testing new and existing vehicle concepts and driver support systems. When a driver in a driving simulator operates it in the same way as they would in actual traffic, you get a realistic evaluation of what you want to investigate. Two advantages of a driving simulator are (1.) that you can repeat the same situation several times over a short period of time, and (2.) you can study driver reactions during dangerous situations that could result in serious injuries if they occurred in the real world. An important component of a driving simulator is the vehicle model, i.e., the model that describes how the vehicle reacts to its surroundings and driver inputs. To increase the simulator realism or the computational performance, it is possible to divide the vehicle model into subsystems that run on different computers that are connected in a network. A subsystem can also be replaced with hardware using so-called hardware-in-the-loop simulation, and can then be connected to the rest of the vehicle model using a specified interface. The technique of dividing a model into smaller subsystems running on separate nodes that communicate through a network is called distributed simulation.

    This thesis investigates if and how a distributed simulator design might facilitate the maintenance and new development required for a driving simulator to be able to keep up with the increasing pace of vehicle development. For this purpose, three different distributed simulator solutions have been designed, built, and analyzed with the aim of constructing distributed simulators, including external hardware, where the simulation achieves the same degree of realism as with a traditional driving simulator. One of these simulator solutions has been used to create a parameterized powertrain model that can be configured to represent any of a number of different vehicles. Furthermore, the driver's driving task is combined with the powertrain model to monitor deviations. After the powertrain model was created, subsystems from a simulator solution and the powertrain model have been transferred to a Modelica environment. The goal is to create a framework for requirement testing that guarantees sufficient realism, also for a distributed driving simulation.

    The results show that the distributed simulators we have developed work well overall with satisfactory performance. It is important to manage the vehicle model and how it is connected to a distributed system. In the distributed driveline simulator setup, the network delays were so small that they could be ignored, i.e., they did not affect the driving experience. However, if one gradually increases the delays, a driver in the distributed simulator will change his/her behavior. The impact of communication latency on a distributed simulator also depends on the simulator application, where different usages of the simulator, i.e., different simulator studies, will have different demands. We believe that many simulator studies could be performed using a distributed setup. One issue is how modifications to the system affect the vehicle model and the desired behavior. This leads to the need for methodology for managing model requirements. In order to detect model deviations in the simulator environment, a monitoring aid has been implemented to help notify test managers when a model behaves strangely or is driven outside of its validated region. Since the availability of distributed laboratory equipment can be limited, the possibility of using Modelica (which is an equation-based and object-oriented programming language) for simulating subsystems is also examined. Implementation of the model in Modelica has also been extended with requirements management, and in this work a framework is proposed for automatically evaluating the model in a tool.

    Delarbeten
    1. Vehicle Powertrain Test Bench Co-Simulation with a Moving Base Simulator Using a Pedal Robot
    Öppna denna publikation i ny flik eller fönster >>Vehicle Powertrain Test Bench Co-Simulation with a Moving Base Simulator Using a Pedal Robot
    2013 (Engelska)Ingår i: SAE International Journal of Passenger Cars - Electronic and Electrical Systems, ISSN 1946-4614, E-ISSN 1946-4622, Vol. 6, nr 1, s. 169-179Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    To evaluate driver perception of a vehicle powertrain a moving base simulator is a well-established technique. We are connecting the moving base simulator Sim III, at the Swedish National Road and Transport Research Institute with a newly built chassis dynamometer at Vehicular Systems, Linköping University. The purpose of the effort is to enhance fidelity of moving base simulators by letting drivers experience an actual powertrain. At the same time technicians are given a new tool for evaluating powertrain solutions in a controlled environment. As a first step the vehicle model from the chassis dynamometer system has been implemented in Sim III. Interfacing software was developed and an optical fiber covering the physical distance of 500 m between the facilities is used to connect the systems. Further, a pedal robot has been developed that uses two linear actuators pressing the accelerator and brake pedals. The pedal robot uses feedback loops on accelerator position or brake cylinder pressure and is controlled via an UDP interface. Results from running the complete setup showed expected functionality and we are successful in performing a driving mission based on real road topography data. Vehicle acceleration and general driving feel was perceived as realistic by the test subjects while braking still needs improvements. The pedal robot construction enables use of a large set of cars available on the market and except for mounting the brake pressure sensor the time to switch vehicle is approximately 30 minutes.

    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-92215 (URN)10.4271/2013-01-0410 (DOI)
    Tillgänglig från: 2013-05-08 Skapad: 2013-05-08 Senast uppdaterad: 2019-04-28Bibliografiskt granskad
    2. A Driving Simulation Platform using Distributed Vehicle Simulators and HLA
    Öppna denna publikation i ny flik eller fönster >>A Driving Simulation Platform using Distributed Vehicle Simulators and HLA
    Visa övriga...
    2015 (Engelska)Ingår i: Proceedings of the DSC 2015 Europe: Driving Simulation Conference & Exhibition / [ed] Heinrich Bülthoff, Andras Kemeny and Paolo Pretto, 2015, s. 123-130Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    Modern vehicles are complex systems consisting of an increasing large multitude of components that operate together. While functional verification on individual components is important, it is also important to test components within a driving environment, both from a functional perspective and from a driver perspective. One proven way for testing is vehicle simulators and in this work the main goals have been to increase flexibility and scalability by introducing a distributed driving simulator platform.

    As an example, consider a workflow where a developer can go from a desktop simulation to an intermediate driving simulator to a high fidelity driving simulator with Hardware-In-the-Loop systems close to a finished vehicle in an easy way. To accomplish this, a distributed simulation architecture was designed and implemented that divides a driving simulator environment into four major entities with well-defined interfaces, using HLA as the method of communication. This platform was evaluated on two aspects, flexibility/scalability and timing performance. Results show that increased flexibility and scalability was achieved when using a distributed simulation platform. It is also shown that latency was only slightly increased when using HLA.

    Nyckelord
    Test, Vehicle, Engine, Performance, Simulator (driving), Computer
    Nationell ämneskategori
    Datorsystem
    Forskningsämne
    90 Road: Vehicles and vehicle technology, 911 Road: Components of the vehicle; 90 Road: Vehicles and vehicle technology, 96 Road: Vehicle operating and management
    Identifikatorer
    urn:nbn:se:liu:diva-136153 (URN)9783981309935 (ISBN)
    Konferens
    Driving Simulation Conference 2015. 16-18 september 2015, Tübingen, Germany
    Tillgänglig från: 2016-01-11 Skapad: 2017-03-31 Senast uppdaterad: 2019-04-28Bibliografiskt granskad
    3. Testing cooperative intelligent transport systems in distributed simulators
    Öppna denna publikation i ny flik eller fönster >>Testing cooperative intelligent transport systems in distributed simulators
    Visa övriga...
    2019 (Engelska)Ingår i: Transportation Research Part F: Traffic Psychology and Behaviour, ISSN 1369-8478, E-ISSN 1873-5517, Vol. 65, s. 206-216Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Simulation is often used as a technique to test and evaluate systems, as it provides a cost-efficient and safe alternative for testing and evaluation. A combination of simulators can be used to create high-fidelity and realistic test scenarios, especially when the systems-under-test are complex. An example of such complex systems is Cooperative Intelligent Transport Systems (C-ITS), which include many actors that are connected to each other via wireless communication in order to interact and cooperate. The majority of the actors in the systems are vehicles equipped with wireless communication modules, which can range from fully autonomous vehicles to manually driven vehicles. In order to test and evaluate C-ITS, this paper presents a distributed simulation framework that consists of (a) a moving base driving simulator; (b) a real-time vehicle simulator; and (c) network and traffic simulators. We present our approach for connecting and co-simulating the simulators. We report on limitation and performance that this simulation framework can achieve. Lastly, we discuss potential benefits and feasibility of using the simulation framework for testing of C-ITS.

    Ort, förlag, år, upplaga, sidor
    Elsevier, 2019
    Nyckelord
    Cooperative intelligent transportation systems, Hardware-in-the-loop, Network simulator, Traffic simulator, Moving base driving simulator
    Nationell ämneskategori
    Farkostteknik Datorsystem
    Identifikatorer
    urn:nbn:se:liu:diva-159824 (URN)10.1016/j.trf.2019.07.020 (DOI)
    Tillgänglig från: 2019-08-22 Skapad: 2019-08-22 Senast uppdaterad: 2019-08-22Bibliografiskt granskad
    4. Parameterization procedure of a powertrain model for a driving simulator
    Öppna denna publikation i ny flik eller fönster >>Parameterization procedure of a powertrain model for a driving simulator
    2016 (Engelska)Ingår i: Advances in Transportation Studies, ISSN 1824-5463, Vol. 1, s. 99-112Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The automotive industry is facing a major challenge to reduce environmental impacts. As a consequence, the increasing diversity of powertrain configurations put a demand on testing and evaluation procedures. One of the key tools for this purpose is simulators. In this paper a powertrain model and a procedure for parameterizing it, using chassis dynamometers and a developed pedal robot are presented. The parameterizing procedure uses the on-board diagnostics of the car and does not require any additional invasive sensors.

    Thus, the developed powertrain model and parameterization procedure provide a rapid non- invasive way of modelling powertrains of test cars. The parameterizing procedure has been used to model a front wheel drive Golf V with a 1.4L multi-fuel engine and a manual gearbox. The achieved results show a good match between simulation results and test data. The powertrain model has also been tested in real-time in a driving simulator.

    Ort, förlag, år, upplaga, sidor
    Aracne editrice, 2016
    Nyckelord
    Motor, Test, Characteristics, Simulation
    Nationell ämneskategori
    Farkostteknik
    Forskningsämne
    90 Road: Vehicles and vehicle technology, 911 Road: Components of the vehicle
    Identifikatorer
    urn:nbn:se:liu:diva-156538 (URN)10.4399/978885489179109 (DOI)2-s2.0-84982994768 (Scopus ID)
    Tillgänglig från: 2019-04-26 Skapad: 2019-04-26 Senast uppdaterad: 2019-05-03Bibliografiskt granskad
    5. Vehicle model quality framework for moving base driving simulators, a powertrain model example
    Öppna denna publikation i ny flik eller fönster >>Vehicle model quality framework for moving base driving simulators, a powertrain model example
    2018 (Engelska)Ingår i: International Journal of Vehicle Systems Modelling and Testing, ISSN 1745-6436, E-ISSN 1745-6444, Vol. 13, nr 2, s. 93-108Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Moving base driving simulators, with an enclosed human driver, are often used to study driver-vehicle interaction or driver behaviour. Reliable results from such a driving simulator study strongly depend on the perceived realism by the driver in the performed driving task. Assuring sufficient fidelity for a vehicle dynamics model during a driving task is currently to a large degree a manual task. Focus here is to automate this process by employing a framework using collected driving data for detection of model quality for different driving tasks. Using this framework, a powertrain model credibility is predicted and assessed. Results show that chosen powertrain model is accurate enough for a driving scenario on rural roads/motorway, but need improvements for city driving. This was expected, considering the complexity of the vehicle dynamics model, and it was accurately captured by the proposed framework which includes real-time information to the simulator operator.

    Ort, förlag, år, upplaga, sidor
    InderScience Publishers, 2018
    Nyckelord
    vehicle dynamics model, driving simulator, driving task, quality framework, domain of validity, domain of operation, powertrain model
    Nationell ämneskategori
    Datorsystem Farkostteknik
    Identifikatorer
    urn:nbn:se:liu:diva-156544 (URN)10.1504/IJVSMT.2018.098330 (DOI)2-s2.0-85063100727 (Scopus ID)
    Tillgänglig från: 2019-04-26 Skapad: 2019-04-26 Senast uppdaterad: 2019-05-03Bibliografiskt granskad
    6. Models for Distributed Real-Time Simulation in a Vehicle Co-Simulator Setup
    Öppna denna publikation i ny flik eller fönster >>Models for Distributed Real-Time Simulation in a Vehicle Co-Simulator Setup
    2013 (Engelska)Ingår i: Proceedings of the 5th International Workshop on Equation-Based Object-Oriented Modeling Languages and Tools; April 19, University of Nottingham, Nottingham, UK / [ed] Henrik Nilsson, Linköping: Linköping University Electronic Press, 2013, Vol. 84, s. 131-139Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    A car model in Modelica has been developed to be used in a new setup for distributed real-time simulation where a moving base car simulator is connected with a real car in a chassis dynamometer via a 500m fiber optic communication link. The new co-simulator set-up can be used in a number of configurations where hardware in the loop can be interchanged with software in the loop. The models presented in this paper are the basic blocks chosen for modeling the system in the context of a distributed real-time simulation; estimating parameters for the powertrain model; the choice of numeric solver; and the interaction with the solver for real-time properties.

    Ort, förlag, år, upplaga, sidor
    Linköping: Linköping University Electronic Press, 2013
    Serie
    Linköping Electronic Conference Proceedings, ISSN 1650-3686, E-ISSN 1650-3740 ; 84
    Nyckelord
    Modelica; real-time; distributed; communications link
    Nationell ämneskategori
    Datorsystem
    Identifikatorer
    urn:nbn:se:liu:diva-118994 (URN)978-91-7519-621-3 (ISBN)978-91-7519-617-6 (ISBN)
    Konferens
    The 5th International Workshop on Equation-Based Object-Oriented Modeling Languages and Tools, April 19, University of Nottingham, Nottingham; UK
    Tillgänglig från: 2015-06-05 Skapad: 2015-06-05 Senast uppdaterad: 2019-04-28Bibliografiskt granskad
    7. Powertrain Model Assessment for Different Driving Tasks through Requirement Verification
    Öppna denna publikation i ny flik eller fönster >>Powertrain Model Assessment for Different Driving Tasks through Requirement Verification
    2018 (Engelska)Ingår i: The 9th EUROSIM Congress on Modelica and Simulation, 2018, s. 721-727Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    For assessing whether a system model is a good candidate for a particular simulation scenario or choosing the best system model between multiple design alternatives it is important to be able to evaluate the suitability of the system model. In this paper we present a methodology based on finite state machine requirements verifying system behaviour in a Modelica environment where the intended system model usage is within a moving base driving simulator. A use case illustrate the methodology with a Modelica powertrain system model using replaceable components and measured data from a Golf V. The achieved results show the importance of context of requirements and how users are assisted in finding system model issues. 

    Serie
    Linköping Electronic Conference Proceedings, ISSN 1650-3686, E-ISSN 1650-3740 ; 142
    Nyckelord
    system model assessment, requirement modelling, Modelica, finite state machine, powertrain validations
    Nationell ämneskategori
    Datorsystem
    Identifikatorer
    urn:nbn:se:liu:diva-156540 (URN)10.3384/ecp17142721 (DOI)978-91-7685-399-3 (ISBN)
    Konferens
    EUROSIM 2016
    Tillgänglig från: 2019-04-26 Skapad: 2019-04-26 Senast uppdaterad: 2019-05-13
    Ladda ner fulltext (pdf)
    Distributed Moving Base Driving Simulators: Technology, Performance, and Requirements
    Ladda ner (png)
    presentationsbild
  • 28. Beställ onlineKöp publikationen >>
    Andersson, Anders
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska fakulteten. Swedish National Road and Transport Research Institute (VTI), Linköping, Sweden.
    Extensions for Distributed Moving Base Driving Simulators2017Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Modern vehicles are complex systems. Different design stages for such a complex system include evaluation using models and submodels, hardware-in-the-loop systems and complete vehicles. Once a vehicle is delivered to the market evaluation continues by the public. One kind of tool that can be used during many stages of a vehicle lifecycle is driving simulators.

    The use of driving simulators with a human driver is commonly focused on driver behavior. In a high fidelity moving base driving simulator it is possible to provide realistic and repetitive driving situations using distinctive features such as: physical modelling of driven vehicle, a moving base, a physical cabin interface and an audio and visual representation of the driving environment. A desired but difficult goal to achieve using a moving base driving simulator is to have behavioral validity. In other words, \A driver in a moving base driving simulator should have the same driving behavior as he or she would have during the same driving task in a real vehicle.".

    In this thesis the focus is on high fidelity moving base driving simulators. The main target is to improve the behavior validity or to maintain behavior validity while adding complexity to the simulator. One main assumption in this thesis is that systems closer to the final product provide better accuracy and are perceived better if properly integrated. Thus, the approach in this thesis is to try to ease incorporation of such systems using combinations of the methods hardware-in-the-loop and distributed simulation. Hardware-in-the-loop is a method where hardware is interfaced into a software controlled environment/simulation. Distributed simulation is a method where parts of a simulation at physically different locations are connected together. For some simulator laboratories distributed simulation is the only feasible option since some hardware cannot be moved in an easy way.

    Results presented in this thesis show that a complete vehicle or hardware-in-the-loop test laboratory can successfully be connected to a moving base driving simulator. Further, it is demonstrated that using a framework for distributed simulation eases communication and integration due to standardized interfaces. One identified potential problem is complexity in interface wrappers when integrating hardware-in-the-loop in a distributed simulation framework. From this aspect, it is important to consider the model design and the intersections between software and hardware models. Another important issue discussed is the increased delay in overhead time when using a framework for distributed simulation.

    Delarbeten
    1. Vehicle Powertrain Test Bench Co-Simulation with a Moving Base Simulator Using a Pedal Robot
    Öppna denna publikation i ny flik eller fönster >>Vehicle Powertrain Test Bench Co-Simulation with a Moving Base Simulator Using a Pedal Robot
    2013 (Engelska)Ingår i: SAE International Journal of Passenger Cars - Electronic and Electrical Systems, ISSN 1946-4614, E-ISSN 1946-4622, Vol. 6, nr 1, s. 169-179Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    To evaluate driver perception of a vehicle powertrain a moving base simulator is a well-established technique. We are connecting the moving base simulator Sim III, at the Swedish National Road and Transport Research Institute with a newly built chassis dynamometer at Vehicular Systems, Linköping University. The purpose of the effort is to enhance fidelity of moving base simulators by letting drivers experience an actual powertrain. At the same time technicians are given a new tool for evaluating powertrain solutions in a controlled environment. As a first step the vehicle model from the chassis dynamometer system has been implemented in Sim III. Interfacing software was developed and an optical fiber covering the physical distance of 500 m between the facilities is used to connect the systems. Further, a pedal robot has been developed that uses two linear actuators pressing the accelerator and brake pedals. The pedal robot uses feedback loops on accelerator position or brake cylinder pressure and is controlled via an UDP interface. Results from running the complete setup showed expected functionality and we are successful in performing a driving mission based on real road topography data. Vehicle acceleration and general driving feel was perceived as realistic by the test subjects while braking still needs improvements. The pedal robot construction enables use of a large set of cars available on the market and except for mounting the brake pressure sensor the time to switch vehicle is approximately 30 minutes.

    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-92215 (URN)10.4271/2013-01-0410 (DOI)
    Tillgänglig från: 2013-05-08 Skapad: 2013-05-08 Senast uppdaterad: 2019-04-28Bibliografiskt granskad
    2. Models for Distributed Real-Time Simulation in a Vehicle Co-Simulator Setup
    Öppna denna publikation i ny flik eller fönster >>Models for Distributed Real-Time Simulation in a Vehicle Co-Simulator Setup
    2013 (Engelska)Ingår i: Proceedings of the 5th International Workshop on Equation-Based Object-Oriented Modeling Languages and Tools; April 19, University of Nottingham, Nottingham, UK / [ed] Henrik Nilsson, Linköping: Linköping University Electronic Press, 2013, Vol. 84, s. 131-139Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    A car model in Modelica has been developed to be used in a new setup for distributed real-time simulation where a moving base car simulator is connected with a real car in a chassis dynamometer via a 500m fiber optic communication link. The new co-simulator set-up can be used in a number of configurations where hardware in the loop can be interchanged with software in the loop. The models presented in this paper are the basic blocks chosen for modeling the system in the context of a distributed real-time simulation; estimating parameters for the powertrain model; the choice of numeric solver; and the interaction with the solver for real-time properties.

    Ort, förlag, år, upplaga, sidor
    Linköping: Linköping University Electronic Press, 2013
    Serie
    Linköping Electronic Conference Proceedings, ISSN 1650-3686, E-ISSN 1650-3740 ; 84
    Nyckelord
    Modelica; real-time; distributed; communications link
    Nationell ämneskategori
    Datorsystem
    Identifikatorer
    urn:nbn:se:liu:diva-118994 (URN)978-91-7519-621-3 (ISBN)978-91-7519-617-6 (ISBN)
    Konferens
    The 5th International Workshop on Equation-Based Object-Oriented Modeling Languages and Tools, April 19, University of Nottingham, Nottingham; UK
    Tillgänglig från: 2015-06-05 Skapad: 2015-06-05 Senast uppdaterad: 2019-04-28Bibliografiskt granskad
    3. A Driving Simulation Platform using Distributed Vehicle Simulators and HLA
    Öppna denna publikation i ny flik eller fönster >>A Driving Simulation Platform using Distributed Vehicle Simulators and HLA
    Visa övriga...
    2015 (Engelska)Ingår i: Proceedings of the DSC 2015 Europe: Driving Simulation Conference & Exhibition / [ed] Heinrich Bülthoff, Andras Kemeny and Paolo Pretto, 2015, s. 123-130Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    Modern vehicles are complex systems consisting of an increasing large multitude of components that operate together. While functional verification on individual components is important, it is also important to test components within a driving environment, both from a functional perspective and from a driver perspective. One proven way for testing is vehicle simulators and in this work the main goals have been to increase flexibility and scalability by introducing a distributed driving simulator platform.

    As an example, consider a workflow where a developer can go from a desktop simulation to an intermediate driving simulator to a high fidelity driving simulator with Hardware-In-the-Loop systems close to a finished vehicle in an easy way. To accomplish this, a distributed simulation architecture was designed and implemented that divides a driving simulator environment into four major entities with well-defined interfaces, using HLA as the method of communication. This platform was evaluated on two aspects, flexibility/scalability and timing performance. Results show that increased flexibility and scalability was achieved when using a distributed simulation platform. It is also shown that latency was only slightly increased when using HLA.

    Nyckelord
    Test, Vehicle, Engine, Performance, Simulator (driving), Computer
    Nationell ämneskategori
    Datorsystem
    Forskningsämne
    90 Road: Vehicles and vehicle technology, 911 Road: Components of the vehicle; 90 Road: Vehicles and vehicle technology, 96 Road: Vehicle operating and management
    Identifikatorer
    urn:nbn:se:liu:diva-136153 (URN)9783981309935 (ISBN)
    Konferens
    Driving Simulation Conference 2015. 16-18 september 2015, Tübingen, Germany
    Tillgänglig från: 2016-01-11 Skapad: 2017-03-31 Senast uppdaterad: 2019-04-28Bibliografiskt granskad
    Ladda ner fulltext (pdf)
    Extensions for Distributed Moving Base Driving Simulators
    Ladda ner (pdf)
    omslag
    Ladda ner (jpg)
    presentationsbild
  • 29.
    Andersson, Anders
    et al.
    Statens väg- och transportforskningsinstitut, Fordonsteknik och simulering, FTS.
    Andersson Hultgren, Jonas
    Statens väg- och transportforskningsinstitut, Fordonsteknik och simulering, FTS.
    Leandertz, Rickard
    Hiq Accelerated Concept Evaluation AB, Stockholm, Sweden.
    Johansson, Martin
    Pitch Technologies.
    Eriksson, Steve
    Pitch Technologies.
    Jakobson, Ola
    Volvo Car Corporation.
    A Driving Simulation Platform using Distributed Vehicle Simulators and HLA2015Ingår i: Proceedings of the DSC 2015 Europe: Driving Simulation Conference & Exhibition / [ed] Heinrich Bülthoff, Andras Kemeny and Paolo Pretto, 2015, s. 123-130Konferensbidrag (Refereegranskat)
    Abstract [en]

    Modern vehicles are complex systems consisting of an increasing large multitude of components that operate together. While functional verification on individual components is important, it is also important to test components within a driving environment, both from a functional perspective and from a driver perspective. One proven way for testing is vehicle simulators and in this work the main goals have been to increase flexibility and scalability by introducing a distributed driving simulator platform.

    As an example, consider a workflow where a developer can go from a desktop simulation to an intermediate driving simulator to a high fidelity driving simulator with Hardware-In-the-Loop systems close to a finished vehicle in an easy way. To accomplish this, a distributed simulation architecture was designed and implemented that divides a driving simulator environment into four major entities with well-defined interfaces, using HLA as the method of communication. This platform was evaluated on two aspects, flexibility/scalability and timing performance. Results show that increased flexibility and scalability was achieved when using a distributed simulation platform. It is also shown that latency was only slightly increased when using HLA.

  • 30.
    Andersson, Anders
    et al.
    Swedish National Road and Transport Research Institute, Sweden.
    Buffoni, Lena
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Powertrain Model Assessment for Different Driving Tasks through Requirement Verification2018Ingår i: The 9th EUROSIM Congress on Modelica and Simulation, 2018, s. 721-727Konferensbidrag (Refereegranskat)
    Abstract [en]

    For assessing whether a system model is a good candidate for a particular simulation scenario or choosing the best system model between multiple design alternatives it is important to be able to evaluate the suitability of the system model. In this paper we present a methodology based on finite state machine requirements verifying system behaviour in a Modelica environment where the intended system model usage is within a moving base driving simulator. A use case illustrate the methodology with a Modelica powertrain system model using replaceable components and measured data from a Golf V. The achieved results show the importance of context of requirements and how users are assisted in finding system model issues. 

  • 31.
    Andersson, Anders
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten. Swedish National Road and Transportation Research Institute.
    Fritzson, Peter
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Models for Distributed Real-Time Simulation in a Vehicle Co-Simulator Setup2013Ingår i: Proceedings of the 5th International Workshop on Equation-Based Object-Oriented Modeling Languages and Tools; April 19, University of Nottingham, Nottingham, UK / [ed] Henrik Nilsson, Linköping: Linköping University Electronic Press, 2013, Vol. 84, s. 131-139Konferensbidrag (Refereegranskat)
    Abstract [en]

    A car model in Modelica has been developed to be used in a new setup for distributed real-time simulation where a moving base car simulator is connected with a real car in a chassis dynamometer via a 500m fiber optic communication link. The new co-simulator set-up can be used in a number of configurations where hardware in the loop can be interchanged with software in the loop. The models presented in this paper are the basic blocks chosen for modeling the system in the context of a distributed real-time simulation; estimating parameters for the powertrain model; the choice of numeric solver; and the interaction with the solver for real-time properties.

    Ladda ner fulltext (pdf)
    Models for Distributed Real-Time Simulation in a Vehicle Co-Simulator Setup
  • 32.
    Andersson, Anders
    et al.
    VTI, Swedish National Road and Transport Research Institute, Linköping, Sweden.
    Kharrazi, Sogol
    VTI, Swedish National Road and Transport Research Institute, Linköping, Sweden.
    Vehicle model quality framework for moving base driving simulators, a powertrain model example2018Ingår i: International Journal of Vehicle Systems Modelling and Testing, ISSN 1745-6436, E-ISSN 1745-6444, Vol. 13, nr 2, s. 93-108Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Moving base driving simulators, with an enclosed human driver, are often used to study driver-vehicle interaction or driver behaviour. Reliable results from such a driving simulator study strongly depend on the perceived realism by the driver in the performed driving task. Assuring sufficient fidelity for a vehicle dynamics model during a driving task is currently to a large degree a manual task. Focus here is to automate this process by employing a framework using collected driving data for detection of model quality for different driving tasks. Using this framework, a powertrain model credibility is predicted and assessed. Results show that chosen powertrain model is accurate enough for a driving scenario on rural roads/motorway, but need improvements for city driving. This was expected, considering the complexity of the vehicle dynamics model, and it was accurately captured by the proposed framework which includes real-time information to the simulator operator.

  • 33.
    Andersson, Daniel
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Integrated Test Environment2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    To implement a command line interpreter is normally an easy task. The task getsharder when adding requirements of multi instance functions and the system is torun on a multi-processor security critical embedded system. This thesis describesa first iteration of the system development. The project behind the thesis consistsof requirement elicitation, design, implementation and unit testing. The resultfrom the project is a working first version of the system.

    Ladda ner fulltext (pdf)
    Integrated Test Environment
  • 34.
    Andersson, Erik Olov Mårten
    Linköpings universitet, Institutionen för datavetenskap.
    A Gameful Quest to Make Second Language Acquisition Fun2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This study explores the application of principles from game design, and the motivational psychology it is founded upon, to the domain of second language acquisition. A gameful design process based on playtesting andanalysis with design lenses is adapted and used to iteratively design and develop a system for conversation practice with the goal of creating a motivating and engaging experience.The results indicate effectiveness of the process, but generalizing the results would require further research with bigger sample sizes and studies with varied core activities.

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    fulltext
  • 35.
    Andersson, Filip
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    Fault Diagnosis in Distributed Simulation Systems over Wide Area Networks using Active Probing2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The domain of distributed simulation is growing rapidly. This growth leads to larger and more complex supporting network architectures with high requirements on availability and reliability. For this purpose, efficient fault-monitoring is required. This work is an attempt to evaluate the viability of an Active probing approach in a distributed simulation system in a wide area network setting. In addition, some effort was directed towards building the probing-software with future extensions in mind. The Active probing approach was implemented and tested against certain performance requirements in a simulated environment. It was concluded that the approach is viable for detecting the health of the network components. However, additional research is required to draw a conclusion about the viability in more complicated scenarios that depend on more than the responsiveness of the nodes. The extensibility of the implemented software was evaluated with the QMOOD-metric and not deemed particularly extensible.

    Ladda ner fulltext (pdf)
    fulltext
  • 36.
    Andersson, Fredrik
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Storing and structuring big data with businessintelligence in mind2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Sectra has a customer database with approximately 1600 customers across the world. In this system there exists not only medical information but alsoinformation about the environment which the system runs in, usage  pattern and much more.

    This report is about storing data received from log les into a suitable database. Sectra wants to be able to analyze this information so that they can make strategic decisions and get a better understanding of their customers' needs. The tested databases are MongoDB, Cassandra, and MySQL. The results shows that MySQL  is not suitable for storing large amount of data with the current conguration. On the other hand, both MongoDB and Cassandra performed well with the growing amount of data.

    Ladda ner fulltext (pdf)
    fulltext
  • 37.
    Andersson Granberg, Tobias
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Nguyen, Ngoc Hien Thi
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    SIMULATION BASED PREDICTION OF THE NEAR-FUTURE EMERGENCY MEDICAL SERVICES SYSTEM STATE2018Ingår i: 2018 WINTER SIMULATION CONFERENCE (WSC), IEEE , 2018, s. 2542-2553Konferensbidrag (Refereegranskat)
    Abstract [en]

    An ambulance dispatcher decides which ambulances to allocate to new calls, and how to relocate ambulances in order to maintain a good coverage. Doing this, it is valuable to have information about the future expected response times in different parts of the area of responsibility, as well as the expected number of available ambulances. We present a simulation model that can be used to predict this, and compare the results to a naive forecasting model. The results show that while it is difficult to accurately predict the future system state, the simulation based prediction manages this better than the naive model.

  • 38.
    Andersson, Gustav
    Linköpings universitet, Institutionen för datavetenskap, Interaktiva och kognitiva system. Linköpings universitet, Tekniska högskolan.
    Implementing touch interaction in a casual mobile game2014Självständigt arbete på grundnivå (kandidatexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This thesis is to help developers in the touch design of casual games. The thesis work was made on the development platform Gideros Mobile and much of the thesis theory and methods will be based on that work. The purpose of the report is to show what one should think about when making a casual game in a touch design perspective, like taking into account that most people are used to one type of input design (like swiping or tapping), that you should design the game with the purpose to reach out to as a large audience as possible (taking into account people with disabilities) and some small notes on what should be avoided so not to deter people from wanting to play the game. It is important to note that this thesis is built for the purpose of mobile casual games, others will probably not find this thesis relevant.

    Ladda ner fulltext (pdf)
    fulltext
  • 39.
    Andersson Holmström, Simon
    Linköpings universitet, Institutionen för systemteknik, Datorteknik.
    Adaptive TDC: Implementation and Evaluation of an FPGA2015Självständigt arbete på grundnivå (kandidatexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Time to digital converter (TDC) is a digital unit that measures the time interval between two events.This is useful to determine the characteristics and patterns of a signal or an event. In this thesis ahybrid TDC is presented consisting of a tapped delay line and a clock counter principle.

    The TDC is used to measure the time between received data in a QKD application. If the measuredtime does not exceed a certain value then data had been sent without any interception. It is alsopossible to use TDCs in other fields such as laser-ranging and time-of-flight applications.

    The TDC consists of two carry chains, an encoder, a FIFO and a counter for each channel, anAXI-module and a control unit to generate command signals to all channels that are implemented.The time is measured by sampling the signal that has propagated through the carry chain and from thissample encode the propagation length.

    In this thesis a TDC is implemented that has a 10 ns dead time and a resolution below 28 psin a four channel mode. The propagation variation is approximately two percent of the total valueduring testing. For the implementation an FPGA-board with a Zynq XC7Z020 SoC is used withSystemVerilog that is a hardware describing language (HDL).

    Ladda ner fulltext (pdf)
    fulltext
  • 40.
    Andersson, Håkan
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten. Construct Tools PC AB, Sweden.
    Nordin, Peter
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska fakulteten.
    Borrvall, Thomas
    DYNAmore Nordic AB, Brigadgatan 5, S-58758 Linkoping, Sweden.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Hilding, Daniel
    DYNAmore Nordic AB, Brigadgatan 5, S-58758 Linkoping, Sweden.
    Schill, Mikael
    DYNAmore Nordic AB, Brigadgatan 5, S-58758 Linkoping, Sweden.
    Krus, Petter
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system. Linköpings universitet, Tekniska fakulteten.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    A co-simulation method for system-level simulation of fluid-structure couplings in hydraulic percussion units2017Ingår i: Engineering with Computers, ISSN 0177-0667, E-ISSN 1435-5663, Vol. 33, nr 2, s. 317-333Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper addresses a co-simulation method for fluid power driven machinery equipment, i.e. oil hydraulic machinery. In these types of machinery, the fluid-structure interaction affects the end-product performance to a large extent, hence an efficient co-simulation method is of high importance. The proposed method is based on a 1D system model representing the fluid components of the hydraulic machinery, within which structural 3D Finite Element (FE) models can be incorporated for detailed simulation of specific sub-models or complete structural assemblies. This means that the fluid system simulation will get a more accurate structural response, and that the structural simulation will get more correct fluid loads at every time step, compared to decoupled analysis. Global system parameters such as fluid flow, performance and efficiency can be evaluated from the 1D system model simulation results. From the 3D FE-models, it is possible to evaluate displacements, stresses and strains to be used in stress analysis, fatigue evaluation, acoustic analysis, etc. The method has been implemented using two well-known simulation tools for fluid power system simulations and FE-simulations, respectively, where the interface between the tools is realised by use of the Functional Mock-up Interface standard. A simple but relevant model is used to validate the method.

    Ladda ner fulltext (pdf)
    fulltext
  • 41.
    Andersson, Rikard
    et al.
    Linköpings universitet, Institutionen för datavetenskap.
    Emberg, Johan
    Linköpings universitet, Institutionen för datavetenskap.
    Hazell, Sofie
    Linköpings universitet, Institutionen för datavetenskap.
    Laestander, Hjalmar
    Linköpings universitet, Institutionen för datavetenskap.
    Norberg, Gustaf
    Linköpings universitet, Institutionen för datavetenskap.
    Elmfeldt Rönnmark, Maximilian
    Linköpings universitet, Institutionen för datavetenskap.
    Buciuto Sundelin, Bruno
    Linköpings universitet, Institutionen för datavetenskap.
    Törngren, Erik
    Linköpings universitet, Institutionen för datavetenskap.
    Heat n' Eat: Utvecklingen av en användbar e-butik med fokus på navigerbarhet2017Självständigt arbete på grundnivå (kandidatexamen), 12 poäng / 18 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Studenter idag har brist på både tid och pengar. Samtidigt ökar e-handeln och specifikt matförsäljningen över internet. Rapporten har som avsikt att undersöka möjligheterna för en tjänst, i form av en webbapplikation, som erbjuder studenter högkvalitativ mat inom deras budget på ett enkelt sätt. Via en marknadsundersökning på Campus Valla uttryckte studenter avsaknad av en sådan tjänst. Studien genomfördes genom att ta fram teori rörande användbarhet och navigerbarhet. Studenter som grupp har ofta ont om tid och är vana vid att få snabb och tydlig information vilket god navigerbarhet säkerställer. Efter teoristudien genomfördes användartester på målgruppen. Som ett resultat utvecklades webbapplikationen Heat n’ Eat. För att uppnå god navigerbarhet blev utformningen en simpel struktur med produkterna i fokus. Ett avslutande användartest visade att webbapplikationen kan anses vara användbar med fokus på navigerbarhet.

    Ladda ner fulltext (pdf)
    fulltext
  • 42.
    Andersson, Samuel
    et al.
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Ekberg, Björn
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Prestandaoptimering av spelet Go Supernova2013Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Som underlag för den här rapporten använder vi oss av vårtspel Go Supernova. Det är skrivet i Java med hjälp avramverket LibGDX. Vi har undersökt hur man kan optimeraspelet för att kunna hantera så många objekt som möjligt menändå hålla ett bra spelflöde utan att förstöra den vision vihade när vi skapade spelet från första början. Vi har kommitfram till att ljusmotorn box2dlights använder sig av mycketprocessorkraft och användningen av den behövde justeras föratt tillfredsställa våra krav. Vi kommer även att tala omdesignval av spelets interna delar som gjorde att vi kundeundvika prestandaförluster.

    Ladda ner fulltext (pdf)
    rapport
  • 43.
    Angström, Fredrik
    et al.
    Linköpings universitet, Institutionen för datavetenskap.
    Faber, Petra
    Linköpings universitet, Institutionen för datavetenskap.
    Evaluating the personalisation potential in local news2021Självständigt arbete på grundnivå (kandidatexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Personalisation of content is a frequently used technique intended to improve user engagement and provide more value to users. Systems designed to provide recommendations to users are called recommender systems and are used in many different industries. This study evaluates the potential of personalisation in a media group primarily publishing local news, and studies how information stored by the group may be used for recommending content. Specifically, the study focuses primarily on content-based filtering by article tags and user grouping by demographics. This study first analyses the data stored by a media group to evaluate what information, data structures, and trends have potential use in recommender systems. These insights are then applied in the implementation of recommender systems, leveraging that data to perform personalised recommendations. When evaluating the performance of these recommender systems, it was found that tag-based content selection and demographic grouping each contribute to accurately recommending content, but that neither method is sufficient for providing fully accurate recommendations.

    Ladda ner fulltext (pdf)
    fulltext
  • 44.
    Antonov, Vera
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Interaktiva och kognitiva system.
    Sterner, Adam
    Linköpings universitet, Institutionen för datavetenskap, Interaktiva och kognitiva system.
    Methods for developing visualizations in a non-designer environment: A case study2019Självständigt arbete på grundnivå (kandidatexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Teams consisting of only software developers will occasionally need to develop products that has to be easy to use. User Centered Design (UCD) is one approach to help increase the ease of use of a product and that can be incorporated into the teams’ traditional workflow when needed. The software developer team followed in this thesis had not tried to incorporate UCD into their current workflow when developing such products. So, this thesis looks at how a product designed with an agile/UCD approach differs from a product developed by the software development team’s traditional approach. The two products were designed to solve the same problem. The results show that the product developed with an agile/UCD-approach gave better usability rankings and better external appeal than the one created with the team’s traditional approach. On the other hand, traditional methods constitute a better choice for quick development of products for more technical user groups within the company for example.

    Ladda ner fulltext (pdf)
    fulltext
  • 45.
    Araki, Masahiro
    et al.
    Department of Electronics and Information Science, Kyoto Institute of Technology, Kyoto, Japan.
    Komatani, Kazunori
    Graduate School of Informatics, Kyoto University.
    Hirata, Taishi
    Graduate School of Informatics, Kyoto University.
    Doshita, Shuji
    Department of Science and Technology, Ryukoku University, Japan.
    A Dialogue Library for Task-Oriented Spoken Dialogue Systems1999Rapport (Övrigt vetenskapligt)
    Abstract [en]

    In this paper, we describe a dialogue library for task-oriented spoken dialogue systems. This library was designed for a general task domains. We have classified several domains into three abstract tasks according to the direction of information flow. Subdialogue of the abstract task can be represented by the library which is combined to each application, such as, slot-filler, database and XML. The portability of this library was evaluated in slot-filling task.

    Ladda ner fulltext (pdf)
    fulltext
  • 46.
    Aramrattana, Maytheewat
    et al.
    The Swedish National Road and Transport Research Institute (VTI), Linköping, Sweden.
    Andersson, Anders
    The Swedish National Road and Transport Research Institute (VTI), Linköping, Sweden.
    Reichenberg, Frida
    RISE Viktoria, Lindholmen Science Park, Lindholmspiren 3A, Gothenburg, Sweden.
    Mellegård, Niklas
    RISE Viktoria, Lindholmen Science Park, Lindholmspiren 3A, Gothenburg, Sweden.
    Burden, Håkan
    RISE Viktoria, Lindholmen Science Park, Lindholmspiren 3A, Gothenburg, Sweden.
    Testing cooperative intelligent transport systems in distributed simulators2019Ingår i: Transportation Research Part F: Traffic Psychology and Behaviour, ISSN 1369-8478, E-ISSN 1873-5517, Vol. 65, s. 206-216Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Simulation is often used as a technique to test and evaluate systems, as it provides a cost-efficient and safe alternative for testing and evaluation. A combination of simulators can be used to create high-fidelity and realistic test scenarios, especially when the systems-under-test are complex. An example of such complex systems is Cooperative Intelligent Transport Systems (C-ITS), which include many actors that are connected to each other via wireless communication in order to interact and cooperate. The majority of the actors in the systems are vehicles equipped with wireless communication modules, which can range from fully autonomous vehicles to manually driven vehicles. In order to test and evaluate C-ITS, this paper presents a distributed simulation framework that consists of (a) a moving base driving simulator; (b) a real-time vehicle simulator; and (c) network and traffic simulators. We present our approach for connecting and co-simulating the simulators. We report on limitation and performance that this simulation framework can achieve. Lastly, we discuss potential benefits and feasibility of using the simulation framework for testing of C-ITS.

  • 47.
    Arreström, Leopold
    et al.
    Linköpings universitet, Institutionen för datavetenskap.
    Magnusson, Fanny
    Linköpings universitet, Institutionen för datavetenskap.
    Bästa praxisar i ett funktionellt och reaktivt JavaScript-ramverk på ett medelstort teknikföretag: En fallstudie2020Självständigt arbete på grundnivå (kandidatexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Exsitec AB är ett medelstort svenskt teknikföretag som nyligen börjat använda sig av ramverket NgRx för tillståndshantering i sina applikationer. Utvecklarna på Exsitec AB har upplevt att de saknar riktlinjer för hur ramverket bäst ska användas, framförallt hur de ska undvika att stora projekt som använder ramverket inte ska bli svårhanterliga. Denna fallstudie syftar till att utröna hur deras arbete med NgRx ser ut vid tiden för studien och utifrån det ta fram praxisar som gör arbetet lättare. Detta görs genom att först genomföra en intervjuserie för att förstå den nuvarande situationen och hitta problemområden. Därefter genomförs kodförståelseexperiment för att se om föreslagna lösningar kan öka kodförståelsen på Exsitec AB. Från detta tas tre praxisar fram med vilka Exsitec ABs arbete med NgRx kan underlättas.

    Ladda ner fulltext (pdf)
    fulltext
  • 48.
    Asghar, Adeel
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Pfeiffer, Andreas
    DLR Institute of System Dynamic and Control, Wessling, Tyskland.
    Palanisamy, Arunkumar
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Mengist, Alachew
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Sjölund, Martin
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Pop, Adrian
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Fritzson, Peter
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Automatic Regression Testing of Simulation Models and Concept for Simulation of Connected FMUs in PySimulator2015Ingår i: Proceedings of the 11th International Modelica Conference: Versailles, France, September 21-23, 2015 / [ed] Peter Fritzson, Hilding Elmqvist, Linköping, 2015, s. 671-679Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Modelica and FMI tool ecosystem is growing each year with new tools and methods becoming available. The open Modelica standard promises portability but it is important to ensure that a certain model behaves the same in different Modelica tools or in a different version of the same tool. It is also very important (for model evolution) to check that a new version of the same model produces comparable results. Finally, it is desirable to verify that a model exported in FMU form from a Modelica tool gives exactly the same results as the original model. This paper presents a framework for automatic regression testing as part of PySimulator which provides an efficient and concise way of testing if a model or a range of models behaves in the same way in several tools or versions of a tool by checking that the results produced are essentially identical. The FMI standard has been adopted by many tool vendors and is growing in popularity each year. This paper proposes a concept for building and simulating a system made from connected FMUs generated by different tools. The FMUs for Co-Simulation can be connected together using a GUI. The system model built graphically in this way can be saved for later use or simulated directly inside PySimulator. Active development is going on to support simulation of connected FMUs for Model Exchange.

  • 49.
    Askling, Kim
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    Application of Topic Models for Test Case Selection: A comparison of similarity-based selection techniques2019Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Regression testing is just as important for the quality assurance of a system, as it is time consuming. Several techniques exist with the purpose of lowering the execution times of test suites and provide faster feedback to the developers, examples are ones based on transition-models or string-distances. These techniques are called test case selection (TCS) techniques, and focuses on selecting subsets of the test suite deemed relevant for the modifications made to the system under test.

    This thesis project focused on evaluating the use of a topic model, latent dirichlet allocation, as a means to create a diverse selection of test cases for coverage of certain test characteristics. The model was tested on authentic data sets from two different companies, where the results were compared against prior work where TCS was performed using similarity-based techniques. Also, the model was tuned and evaluated, using an algorithm based on differential evolution, to increase the model’s stability in terms of inferred topics and topic diversity.

    The results indicate that the use of the model for test case selection purposes was not as efficient as the other similarity-based selection techniques studied in work prior to thist hesis. In fact, the results show that the selection generated using the model performs similar, in terms of coverage, to a randomly selected subset of the test suite. Tuning of the model does not improve these results, in fact the tuned model performs worse than the other methods in most cases. However, the tuning process results in the model being more stable in terms of inferred latent topics and topic diversity. The performance of the model is believed to be strongly dependent on the characteristics of the underlying data used to train the model, putting emphasis on word frequencies and the overall sizes of the training documents, and implying that this would affect the words’ relevance scoring to the better.

    Ladda ner fulltext (pdf)
    fulltext
  • 50.
    Asplund, Mikael
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Nadjm-Tehrani, Simin
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Attitudes and Perceptions of IoT Security in Critical Societal Services2016Ingår i: IEEE Access, E-ISSN 2169-3536, Vol. 4, s. 2130-2138Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A quiet revolution that impacts several sectors, ranging over transport, home automation, energy, industrial control, and health services is undergoing with addition of new networked devices leading to enhanced services. In this paper, we aim to identify information security requirements that are common over several (vertical) sectors, and in particular, ones that impact critical societal services, namely, the energy, water, and health management systems. We present the results of an interview-based study where actors in these sectors were asked about their perceptions and attitudes on the security of Internet of Things (IoT). We set these perceptions and attitudes in context through a literature review of IoT security, and relate to current challenges in this area. This paper demonstrates that despite an overall optimistic view on IoT in critical societal services, there is a lack of consensus on risks related to IoT security.

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    fulltext
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