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  • 201.
    Andersson, Ellen
    Linköpings universitet, Institutionen för datavetenskap.
    Cognitive Workload, Game Experience, and Intrinsic Motivation2017Independent thesis Basic level (degree of Bachelor), 12 poäng / 18 hpOppgave
    Abstract [en]

    When it comes to game design, two features that have been linked to the success of a game are playability and the subjective game experience. This is perhaps not surprising, as the main purpose of a game is to entertain. What cognitive factors that may underlie these features has, however, not been explored. This study examines the relationship between both workload and cognitive workload and player experience. The results suggest that an increase in workload, including cognitive workload, positively affect the player experience of the game as well as the player’s intrinsic motivation.

  • 202.
    Andersson, Erik
    et al.
    Linköpings universitet, Institutionen för datavetenskap.
    Combler, David
    Linköpings universitet, Institutionen för datavetenskap.
    Evaluation of Key Management Protocols and Their Implementations2018Independent thesis Basic level (degree of Bachelor), 10,5 poäng / 16 hpOppgave
    Abstract [en]

    When constructing a network system it is important to consider the attributes which define said system and how to best build around those attributes. In this report we’ve studied Key Management Protocols as well as 802.15.4 WPAN networks and how key managment is conducted in such networks. This was done to better understand how Key Management Protocols themselves work and if, or how, they differ when used in 802.15.4 networks.

    In this report we studied 4 different Key Management Protocols: IKEv2,HIPv2,PANA and 802.1X as well as their various implementations. Based on the information gathered we analyzed how an implementation would work according to IEEE 802.15.9.

    Firstly we found was that IKEv2 offers a lot of functionality at the cost of system complexity and required a lot of memory. It also required major modifications to work in 802.15.4 networks.

    Secondly we found that HIPv2 offers the ability to separate the locator and identifier tags of TCP/IP and is lightweight. It doesn’t use IP or TCP/UDP and as such required minor changes to work in 802.15.4 networks.

    Finally, PANA and 802.1X both offer client-to-network authentication using EAP and use a moderate to high amount of space. 802.1X required a moderate amount of changes to work in 802.15.4 networks. PANA on the other hand required few changes, though it should not be used as a general purpose Key Management Protocol in 802.15.4 networks.

  • 203.
    Andersson, Gustav
    et al.
    Linköpings universitet, Institutionen för datavetenskap.
    Eriksson, Gustav
    Linköpings universitet, Institutionen för datavetenskap.
    Jungmalm, David
    Linköpings universitet, Institutionen för datavetenskap.
    Möller Ehrnlund, Björn
    Linköpings universitet, Institutionen för datavetenskap.
    Petersson, Julius
    Linköpings universitet, Institutionen för datavetenskap.
    Yngesjö, Tim
    Linköpings universitet, Institutionen för datavetenskap.
    Plattform för spelifiering inom programmeringskurser2019Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Denna rapport beskriver ett arbete som utförts i kursen TDDD96 - Kandidatprojekt i programvaruutveckling. Projektet gick ut på att utveckla en webbplattform för spelifierad tävlingsprogrammering åt UPP-gruppen på Institutionen för datavetenskap vid Linköpings universitet. Plattformen är tänkt att användas i programmeringskurser. Den innehåller funktioner som låter användare ladda upp spel och agenter via en hemsida där agenterna kan spela spelen mot varandra. Produkten består av en klient i form av en hemsida, och en server. Det finns även ett API för att skapa spel till plattformen. Rapporten beskriver dessa delar både på det tekniska planet samt hur utvecklingsprocesserna gick till. Utöver detta presenteras och diskuteras gruppens erfarenheter från projektet samt hur den slutgiltiga produkten förhåller sig till gruppens och kundens mål. Genom att använda kodgranskning under utvecklingen upplevde gruppen en ökad kvalitet på koden, men också att det stävjade utvecklingen i de fall då granskningen tog lång tid. Den viktigaste erfarenheten gruppen tog med sig från detta projekt är att kommunikationen har mycket stor betydelse för resultaten, och bör därför struktureras upp ordentligt. Genom att arbeta med kundens behov som högsta prioritet, dokumentera all kod väl och konstruera systemet modulärt för att främja vidareutveckling, kan en bra och välgjord produkt skapas som ger värde för kunden.

  • 204.
    Andersson, Helena
    Linköpings universitet, Institutionen för systemteknik.
    Genus och informationsteknologi2004Independent thesis Basic level (professional degree)Oppgave
    Abstract [en]

    This thesis discusses how the education in the Master of Engineering program can change to become more into line for the students needs, especially for the women, both directly in the education situation and later in their occupational roles. This is done using a gender perspective. Both the education and the occupation today is characterised by masculine norms and values. The education lacks gender perspective and is created by men, for men. The thesis gives concrete proposals on how to change two existing courses to better fit the students. Some of the most important changes are to make the goals of the courses more accessible and visible for the students, make sure that both men and women occurs in teaching positions and have course literature written by women as well as men.

  • 205.
    Andersson, Helena
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Eriksson, Kristina
    Linköpings universitet, Institutionen för teknik och naturvetenskap.
    You´ve got m@il: en studie om sambandet mellan e-post och effektiv kommunikation i en IT-intensiv organisation2004Independent thesis Basic level (degree of Bachelor)Oppgave
    Abstract [sv]

    Användningen av elektroniska kommunikationsmedel ökar ständigt och många organisationer byggersin verksamhet på ett starkt informationsberoende. Verksamheterna har blivit allt mer informationsbaserade och informationsteknologin är en oumbärlig del för organisationers infrastrukturer. Därför är utgångspunkten för denna studie att utveckla ny kunskap om hur individer uppfattar effektiv kommunikation i en IT-intensiv organisation. Arbetet undersöker även aspekter som medverkar eller motverkar den upplevda effektiviteten vid användandet av e-post i IT-intensiva organisationer och hur e-post kombineras med andra kommunikationsverktyg för att uppnå önskad effektivitet.

    Den empiriska grunden till studien är en organisation, där tio kvalitativa intervjuer gjorts. Studien har hermeneutisk inriktning eftersom den bygger på informanternas tolkningar, uppfattningar och åsikter. Arbetet undersöker empirisk data, intervjuer, vilket har mynnat ut i ett resultat, vilket är ett induktivt förhållningssätt. Vid intervjutillfällena har gruppmedlemmarnas intention varit att få så mycket information som möjligt, om organisationen och deras arbetssätt med elektroniska kommunikationsmedel för att sedan behandla det mest relevanta.

    Studiens resultat påvisar att e-post är ett väsentligt arbetsredskap och ett villkor för effektiv kommunikation i en IT-intensiv organisation. E-post kan ses som en del av en stor verktygslåda där olika verktyg kompletterar varandra. Det är medarbetaren själv som väljer vilket verktyg som är mest lämpat i olika situationer. Resultatet visar även att informations- och uppgiftsmängden ständigt ökar med den elektroniska kommunikationen. Vilket leder till tyngre arbetsbörda och stress för medarbetarna.

  • 206.
    Andersson, Henric
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Maskinkonstruktion. Linköpings universitet, Tekniska högskolan.
    Variability and Customization of Simulator Products: A Product Line Approach in Model Based Systems Engineering2012Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    AIRCRAFT DEVELOPERS, like other organizations within development and manufacturing, are experiencing increasing complexity in their products and growing competition in the global market. Products are built from increasingly advanced technologies and their mechanical, electronic, and software parts grow in number and become more interconnected. Different approaches are used to manage information and knowledge of products in various stages of their lifecycle.

    "Reuse" and "Model Based Development" are two prominent trends for improving industrial development efficiency. The product line approach is used to reduce the time to create product variants by reusing components. The model based approach provides means to capture knowledge about a system in the early lifecycle stages for usage throughout its entire lifetime. It also enables structured data  management as a basis for analysis, automation, and team collaboration for efficient management of large systems and families of products.

    This work is focused on the combination of methods and techniques within;

    • modeling and simulation-based development, and
    • (re)use of simulation models through the product line concept.

    With increasing computational performance and more efficient techniques/tools for building simulation models, the number of models increases, and their usage ranges from concept evaluation to end-user training. The activities related to model verification and validation contribute to a large part of the overall cost for development and maintenance of simulation models. The studied methodology aims to reduce the number of similar models created by different teams during design, testing, and end-user support of industrial products.

    Results of the work include evaluation of a configurator to customize and integrate simulation models for different types of aircraft simulators that are part of a simulator product family. Furthermore, contribution comprises results where constraints in the primary product family (aircraft) govern the configuration space of the secondary product family (simulators). Evaluation of the proposed methodology was carried out in cooperation with the simulator department for the 39 Gripen fighter aircraft at Saab Aeronautics.

    Delarbeid
    1. Experience from introducing Unified Modeling Language/Systems Modeling Language at Saab Aerosystems
    Åpne denne publikasjonen i ny fane eller vindu >>Experience from introducing Unified Modeling Language/Systems Modeling Language at Saab Aerosystems
    2010 (engelsk)Inngår i: Systems Engineering, ISSN 1098-1241, E-ISSN 1520-6858, Vol. 13, nr 4, s. 369-380Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    A Unified Modeling Language/Systems Modeling Language (UML/SysML) subset was the modeling notation selected for an aerospace systems engineering project at Saab Aerosystems. In this paper, the rationale for selecting UML/SysML is given, along with a description of the situation at the project planning stage regarding business conditions, method and tools support. The usage of use case, sequence, and activity diagrams are described as well as definition of functional chains with SysML. Furthermore, the connections to system implementation activities including code generation and simulation are discussed. The advantages and disadvantages of using UML/SysML from experience in an industrial context are reported.

    It is also described how UML/SysML is related to industrial research projects in the Model Based Systems Engineering (MBSE) methods and tools area. Introducing UML/SysML with a methodology and a supporting toolset in an operative organization require a clear strategy, including planning, just-in-time training, and mentor support. Finally, industrial needs for further development of SysML are discussed.

    sted, utgiver, år, opplag, sider
    Wiley, 2010
    Emneord
    Systems Modeling Language, Unified Modeling Language, Model Based Systems Engineering, Unmanned Aerial Vehicle
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-17941 (URN)10.1002/sys.20156 (DOI)000284008700005 ()
    Tilgjengelig fra: 2009-04-27 Laget: 2009-04-27 Sist oppdatert: 2017-12-13bibliografisk kontrollert
    2. Model Based Systems Engineering for Aircraft Systems – How does Modelica Based Tools Fit?
    Åpne denne publikasjonen i ny fane eller vindu >>Model Based Systems Engineering for Aircraft Systems – How does Modelica Based Tools Fit?
    2011 (engelsk)Inngår i: Proceedings of the 8th International Modelica Conference, March 20th-22nd, Technical Univeristy, Dresden, Germany / [ed] Clauß, Christoph, Linköping: Linköping University Electronic Press, 2011, s. 856-864Konferansepaper, Publicerat paper (Annet vitenskapelig)
    Abstract [en]

    Saab Aeronautics has chosen Modelica and Dymola as part of the means for model based system engineering (MBSE). This paper will point out why a considerable effort has been made to migrate models from other simulation tools to Dymola. The paper also shows how the models and tools are used, experiences gained from usage in an industrial context as well as some remaining trouble spots.

    sted, utgiver, år, opplag, sider
    Linköping: Linköping University Electronic Press, 2011
    Serie
    Linköping Electronic Conference Proceedings, ISSN 1650-3686, E-ISSN 1650-3740 ; 63
    Emneord
    MBSE, Dymola, Aircraft simulation, Model integration, Modelica
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-73511 (URN)10.3384/ecp11063856 (DOI)978-91-7393-096-3 (ISBN)
    Konferanse
    8th International Modelica Conference, March 20th-22nd, Technical Univeristy, Dresden, Germany
    Tilgjengelig fra: 2012-01-06 Laget: 2012-01-06 Sist oppdatert: 2018-02-20bibliografisk kontrollert
    3. Variability and Configuration Principles for Simulation Models in Product Line Development
    Åpne denne publikasjonen i ny fane eller vindu >>Variability and Configuration Principles for Simulation Models in Product Line Development
    2010 (engelsk)Inngår i: Proceedings of the 7th European Systems Engineering Conference, EuSEC 2010: Systems Engineering & Innovation / [ed] INCOSE, 2010, s. 15-Konferansepaper, Publicerat paper (Annet vitenskapelig)
    Abstract [en]

    This paper defines the challenges and needs related to Configuration Management of large scale aeronautical simulation systems, where the MBSE approach is a guiding force. The basic problem is to support modeling and simulation of all variants of a product line. The simulation models may be used in (at least) three different contexts; development, verification and training, each with their specific objectives.

    Assumptions and basic components of the research issue are as follows: There exists a defined product line. The product line is modeled with respect of

    • Configuration; for certification, delivery, and maintenance in a PDM/PLM context
    • Behavior; for development, verification and training in a simulation context

    Configurable simulation models are developed and maintained to represent parts/modules of the product line as well as the environment where the products operate. Each simulation model included in any utilized simulation system can be viewed as a module in a (simulation product) platform. The modular models are stored in a model library for easy access and inclusion in a simulation system. Every model must be configurable in at least three dimensions; representation, usage and implementation. They will represent a specific product within the product family, they will be used in some of the three contexts (development, verification and training) and they will be implemented in a specific simulation platform/architecture.

    Management of configurable simulation models in the described context is an increasingly challenging activity. Supporting systems and methods for configuration and integration of models and simulation systems are not mature and do not scale up. To view the model set as a Software Product Line representing the Product Line of the end products is an approach to more stringent map the simulation models to the real product/system. A concept of a structured ConfiguratioN datA object (CNA-string) is introduced as a means to integrate configuration information and to be used for simulation set-up purposes. Application example in the work is the light weight fighter aircraft Saab 39 Gripen.

    Emneord
    MBSE, PDM, PLM, CSM, Simulation
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-60818 (URN)
    Konferanse
    7th European Systems Engineering Conference EuSEC 2010. Systems Engineering and Innovation, Stockholm, Sweden, May 23–26
    Tilgjengelig fra: 2010-10-27 Laget: 2010-10-27 Sist oppdatert: 2012-02-16bibliografisk kontrollert
    4. Configuration Management of Models for Aircraft Simulation
    Åpne denne publikasjonen i ny fane eller vindu >>Configuration Management of Models for Aircraft Simulation
    2010 (engelsk)Inngår i: Proceedings of the 27th International Congress of the Aeronautical Sciences, 2010, s. 10-Konferansepaper, Publicerat paper (Annet vitenskapelig)
    Abstract [en]

    Support for configuration and instantiation of large-scale aircraft simulations has become a major issue as the numbers of models grow, model fidelity increases and there is a trend to design models to allow reuse between simulation environments. In this work a method for configuration support is presented that is based on the Product Line principles with structures and data inherited from the Product Data Management system. An XML-based information object to carry product configuration data and knowledge between tools, called a CNA-string is introduced. A rule-based method to support specification of consistent configurations is adopted from the sales configuration domain. The application example is configurations of the Gripen fighter aircraft simulation models.

    Emneord
    Software Product Line, Modularity, Configurator, Simulation
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-60821 (URN)
    Konferanse
    The 27th International Congress of the Aeronautical Sciences, 19-24 September, Nice, France
    Tilgjengelig fra: 2010-10-27 Laget: 2010-10-27 Sist oppdatert: 2012-02-16bibliografisk kontrollert
    5. Methodology for Development and Validation of Multipurpose Simulation Models
    Åpne denne publikasjonen i ny fane eller vindu >>Methodology for Development and Validation of Multipurpose Simulation Models
    2012 (engelsk)Inngår i: 50th AIAA Aerospace Sciences Meeting Online Proceedings including the New Horizons Forum and Aerospace Exposition (2012), AIAA , 2012Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    This paper describes a framework for development and validation of multipurpose simulation models. The presented methodology enables reuse of models in different applications with different purposes. The scope is simulation models representing physical environment, physical aircraft systems or subsystems, avionics equipment, and electronic hardware. The methodology has been developed by a small interdisciplinary team, with experience from Modeling and Simulation (M&S) of vehicle systems as well as development of simulators for verification and training. Special care has been taken to ensure usability of the workflow and method descriptions, mainly by means of 1) a user friendly format, easy to overview and update, 2) keeping the amount of text down, and 3) providing relevant examples, templates, and checklists. A simulation model of the Environmental Control System (ECS) of a military fighter aircraft, the Saab Gripen, is used as an example to guide the reader through the workflow of developing and validating multipurpose simulation models. The methods described in the paper can be used in both military and civil applications, and are not limited to the aircraft industry.

    sted, utgiver, år, opplag, sider
    AIAA, 2012
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-74716 (URN)10.2514/6.2012-877 (DOI)
    Konferanse
    50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition, 9–12 January, 2012, Gaylord Opryland Resort & Convention Center, 9-12 January, Nashville, Tennessee
    Tilgjengelig fra: 2012-02-06 Laget: 2012-02-06 Sist oppdatert: 2016-04-25
    6. Towards Configuration Support for Collaborative Simulator Development: A Product Line Approach in Model Based Systems Engineering
    Åpne denne publikasjonen i ny fane eller vindu >>Towards Configuration Support for Collaborative Simulator Development: A Product Line Approach in Model Based Systems Engineering
    2011 (engelsk)Inngår i: Proceedings of the 2011 20th IEEE International Workshops on Enabling Technologies, WETICE 2011: Infrastructure for Collaborative Enterprises, IEEE conference proceedings, 2011, s. 185-192Konferansepaper, Publicerat paper (Annet vitenskapelig)
    Abstract [en]

    In development and support of complex products such as power plants, automotive vehicles, or aircrafts, modeling and simulation has become an important activity as a basis for knowledge capture. Simulation is used in several steps of the product lifecycle; for evaluation of early design, for system verification, and for user training. With emerging techniques such as tools for high-level modeling, multi-core computing, and visualization, the number of useful models is growing. This paper focuses on reuse of multipurpose models and configuration support in a product line context. A configurator prototype system is presented. The simulator set created from validated models is considered to be a secondary product line. The product set which the simulation models represent is considered to be the primary product line. The Saab Gripen fighter aircraft, together with simulators in which the aircraft behavior, performance, and handling qualities are represented, is used to exemplify application. Integration principles of the systems for simulator configuration, Software Configuration Management, and Product Data Management (PDM) are studied. Preliminary results show that a configurator tool can be used, but there is need to map structures between the simulation and PDM domains.

    sted, utgiver, år, opplag, sider
    IEEE conference proceedings, 2011
    Emneord
    MBSE, Product Line, Configurator, Simulation
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-70177 (URN)10.1109/WETICE.2011.74 (DOI)2-s2.0-80052639762 (Scopus ID)978-0-7695-4410-6 (ISBN)978-1-4577-0134-4 (ISBN)
    Konferanse
    20th IEEE International Workshops on Enabling Technologies: Infrastructures for Collaborative Enterprises, 27-29 June, Paris, France
    Tilgjengelig fra: 2011-08-23 Laget: 2011-08-23 Sist oppdatert: 2018-01-12bibliografisk kontrollert
    7. Experience from Model and Software Reuse in Aircraft Simulator Product Line Engineering
    Åpne denne publikasjonen i ny fane eller vindu >>Experience from Model and Software Reuse in Aircraft Simulator Product Line Engineering
    2013 (engelsk)Inngår i: Information and Software Technology, ISSN 0950-5849, E-ISSN 1873-6025, Vol. 55, nr 3, s. 595-606Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Context: "Reuse" and "Model Based Development" are two prominent trends for improving industrial development efficiency. Product lines are used to reduce the time to create product variants by reusing components. The model based approach provides the opportunity to enhance knowledge capture for a system in the early stages in order to be reused throughout its lifecycle. This paper describes how these two trends are combined to support development and support of a simulator product line for the SAAB 39 Gripen fighter aircraft.

    Objective: The work aims at improving the support (in terms of efficiency and quality) when creating simulation model configurations. The objective is to increase the level of reuse when combining and customizing models for usage in a range of development and training simulators.

    Method: The research has been conducted with an interactive approach using prototyping and demonstrations, and the evaluation is based on an iterative and a retrospective method.

    Results: A product line of simulator models for the SAAB 39 Gripen aircraft has been analyzed and defined in a Product Variant Master. A configurator system has been implemented for creation, integration, and customization of stringent simulator model configurations. The system is currently under incorporation in the standard development process at SAAB Aeronautics.

    Conclusion: The explicit and visual description of products and their variability through a configurator system enables better insights and a common understanding so that collaboration on possible product configurations improves and the potential of software reuse increases. The combination of application fields imposes constraints on how traditional tools and methods may be utilized. Solutions for Design Automation and Knowledge Based Engineering are available, but their application has limitations for Software Product Line engineering and the reuse of simulation models.

    Emneord
    Software Product Line; SPL; Knowledge Based Engineering; KBE; Model Based Development; Simulation; Configurator; Customization; PDM; SCM
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-75077 (URN)10.1016/j.infsof.2012.06.014 (DOI)000315369200008 ()
    Tilgjengelig fra: 2012-02-16 Laget: 2012-02-16 Sist oppdatert: 2017-12-07
  • 207.
    Andersson, Henric
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Maskinkonstruktion. Linköpings universitet, Tekniska högskolan.
    Carlsson, Magnus
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Maskinkonstruktion. Linköpings universitet, Tekniska högskolan.
    Ölvander, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Maskinkonstruktion. Linköpings universitet, Tekniska högskolan.
    Towards Configuration Support for Collaborative Simulator Development: A Product Line Approach in Model Based Systems Engineering2011Inngår i: Proceedings of the 2011 20th IEEE International Workshops on Enabling Technologies, WETICE 2011: Infrastructure for Collaborative Enterprises, IEEE conference proceedings, 2011, s. 185-192Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    In development and support of complex products such as power plants, automotive vehicles, or aircrafts, modeling and simulation has become an important activity as a basis for knowledge capture. Simulation is used in several steps of the product lifecycle; for evaluation of early design, for system verification, and for user training. With emerging techniques such as tools for high-level modeling, multi-core computing, and visualization, the number of useful models is growing. This paper focuses on reuse of multipurpose models and configuration support in a product line context. A configurator prototype system is presented. The simulator set created from validated models is considered to be a secondary product line. The product set which the simulation models represent is considered to be the primary product line. The Saab Gripen fighter aircraft, together with simulators in which the aircraft behavior, performance, and handling qualities are represented, is used to exemplify application. Integration principles of the systems for simulator configuration, Software Configuration Management, and Product Data Management (PDM) are studied. Preliminary results show that a configurator tool can be used, but there is need to map structures between the simulation and PDM domains.

  • 208.
    Andersson, Henrik
    et al.
    Linköpings universitet, Institutionen för datavetenskap.
    Andersson, Robin
    Linköpings universitet, Institutionen för datavetenskap.
    Eriksson, Leif
    Linköpings universitet, Institutionen för datavetenskap.
    Hagberg, Alfred
    Linköpings universitet, Institutionen för datavetenskap.
    Lundgren, Jonathan
    Linköpings universitet, Institutionen för datavetenskap.
    Musse, Mustaf
    Linköpings universitet, Institutionen för datavetenskap.
    Nylander, Eric
    Linköpings universitet, Institutionen för datavetenskap.
    Maskininlärning för automatisk matchning av produkter2018Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Denna rapport behandlar det kandidatarbete som har utförts av sju studenter från civilin-genjörsprogrammen datateknik och mjukvaruteknik på Tekniska högskolan vid Linköpingsuniversitet. Projektets mål var att ta fram ett system som via maskininlärning automatisktskapade matchningar mellan företagets interna basprodukter och produkter från diverse le-verantörer. Beställningen av systemet gjordes av Byggvarulistan i Sverige AB.

    Det utvecklade systemet ska lösa problemet företaget hade med att behöva göra alla match-ningar manuellt. Systemet innehåller en maskininlärningsdel som utför matchningarna ochett administrationsgränssnitt för att korrigera och acceptera dessa matchningar. Utvecklingenav systemet har behövts anpassas till de rådande förutsättningarna med visst brus i kundensdatabas. Graden av nytta som kunden kommer utvinna från systemet beror därför delvispå hur kvaliteten på databasens innehåll kan förbättras för att ge bättre förutsättningar tillmatchningssystemet.

    Rapporten beskriver hur utvecklingen av systemet har skett samt vad det slutgiltiga systemetblev. Detta gjordes utifrån en analys av de använda utvecklingsprocesserna och det slutgil-tiga systemet i ett bredare sammanhang. Det finns även sju individuella bidrag från varderaprojektmedlem där denne utvärderar ett arbetsmetod, algoritm, roll eller liknande relaterattill projektet.

  • 209.
    Andersson Hultgren, Jonas
    Linköpings universitet, Institutionen för systemteknik, Informationskodning.
    Metoder för förbättrad rumsuppfattning i körsimulatorer2011Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Körsimulatorer är idag en mycket viktig resurs för att utföra studier med fokus på förarbeteende. Så väl full kontroll överscenario och miljö som kostnad och säkerhet är aspekter som gör det fördelaktigt att utföra simulatorstudier gentemotstudier i den riktiga trafiken.

    Ett problem med körsimulatorer är att bilden projiceras på en tvådimensionell skärm, vilket begränsar förarens förmåga attuppskatta avstånd och hastighet. Det är allmänt känt att avstånd och hastighet underskattas i körsimulatorer.

    Målet med examensarbetet var att hitta metoder som kan ge förbättrad avståndsbedömning i körsimulatorer och underprojektet implementerades och testades rörelseparallax samt skuggor, med största fokus på det förstnämnda.

    I slutet av projektet genomfördes ett simulatorförsök för att utvärdera effekten av rörelseparallax. Tio försökspersoner fickgöra två körningar vardera i VTI:s Simulator III-anläggning, den ena med rörelseparallax aktiverat och den andra meddetsamma inaktiverat. Scenariot som utspelade sig under körningarna innehöll ett flertal omkörningssituationer samt etthastighetsuppfattningstest.

    Resultaten från simulatorförsöket visade att försökspersonerna tenderade att placera sig längre från mittlinjen närrörelseparallax var aktiverat i de situationer som sikten skymdes av framförvarande fordon.

  • 210.
    Andersson, Jacob
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling. Linköpings universitet, Tekniska högskolan.
    Zahirovic, Elvis
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling. Linköpings universitet, Tekniska högskolan.
    För- och Nackdelar med Molnbaserade Affärssystem2013Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Molnet är en ny revolution inom IT- världen. På senare år har teknologin kring molnbaserade tjänster utvecklats väsentligt och allt fler företag väljer att lägga hela eller delar av sitt affärssystem på molnet. Den grundläggande idén bakom molnet är att beräkningarna utförs på servrar och att informationen därefter strömmas vidare till användaren. De senaste tre åren har investeringarna gällande molnbaserade affärssystem börjat accelerera i allt högre takt. I dagsläget riktar sig molnbaserade affärssystem mot mindre företag som är i ett behov utav ett standardiserat affärssystem som inte kostar multum. Framtiden ser dock ljus ut och investeringarna kring molnbaserade affärssystem har ökat markant sedan 2010.

    Molnbaserade affärssystem har likt de allra flesta nya tekniker sina för- samt nackdelar. Vår undersökning grundar sig i att finna vilka för- samt nackdelar molnbaserade affärssystem för med sig, säkerhetsmässigt samt ekonomiskt för leverantör och kund. Studien har genomförts med en kvalitativ ansats. Det empiriska avsnittet bygger på semistrukturerade intervjuer som genomförts hos flera företag. Teoridelen står som begreppsgrund för den empiriska undersökningen. Intervjupersonernas svar visade vilka för- och nackdelar molnlösningar för med sig, med affärssystem i molnet i synnerhet. Vi jämför vår teoristudie med materialet från den empiriska undersökningen, för att nå svar på våra frågeställningar. Flera problem kan uppstå när ett lokalt affärssystem skall bytas ut eller migreras till ett molnbaserat affärssystem. Säkerheten är ett hett diskussionsämne, klart är att det finns säkerhetshål och att data som färdas mellan servrar på internet alltid är känsligare än data som transporteras lokalt inom en organisation. Säkerheten på molnet är relativt omfattande med diverse säkerhetscertifikat och krypteringar. Hemmasnickrade säkerhetslösningar är en omöjlighet och de flesta företagen följer ”best-practices”. Serverhallarna som information lagras på är byggda med mycket god säkerhet, vilket innebär att inga utomstående personer har tillgång till dessa. Ett stort problem är dock att informationen aldrig lagras lokalt (inom företaget), utan på molnet, vilket kan leda till en misstro hos molnleverantörernas kunder. Ur ett ekonomiskt perspektiv är molnbaserade affärssystem i dagsläget ett bra alternativ för mindre nystartade företag då den initiala kostnaden är låg och som kund betalar man utefter användning. Den initiala kostnaden är således lägre gentemot ett ”traditionellt”, lokalt affärssystem där hårdvara måste inhandlas och personal skall anställas för att sköta underhåll och drift.

  • 211.
    Andersson, Jesper
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Dynamic software architectures2006Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Software architecture is a software engineering discipline that provides notations and processes for high-level partitioning of systems' responsibilities early in the software design process. This thesis is concerned with a specific subclass of systems, systems with a dynamic software architecture. They have practical applications in various domains such as high-availability systems and ubiquitous computing.

    In a dynamic software architecture, the set of architectural elements and the configuration of these elements may change at run-time. These modifications are motivated by changed system requirements or by changed execution environments. The implications of change events may be the addition of new functionality or re-configuration to meet new Quality of Service requirements.

    This thesis investigates new modeling and implementation techniques for dynamic software architectures. The field of Dynamic Architecture is surveyed and a common ground defined. We introduce new concepts and techniques that simplify understanding, modeling, and implementation of systems with a dynamic architecture, with this common ground as our starting point. In addition, we investigate practical use and reuse of quality implementations, where a dynamic software architecture is a fundamental design principle.

    The main contributions are a taxonomy, a classification, and a set of architectural patterns for dynamic software architecture. The taxonomy and classification support analysis, while the patterns affect design and implementation work directly. The investigation of practical applications of dynamic architectures identifies several issues concerned with use and reuse, and discusses alternatives and solutions where possible.

    The results are based on surveys, case studies, and exploratory development of dynamic software architectures in different application domains using several approaches. The taxonomy, classification and architecture patterns are evaluated through several experimental prototypes, among others, a high-performance scientific computing platform.

    Delarbeid
    1. A classification of dynamic software architectures
    Åpne denne publikasjonen i ny fane eller vindu >>A classification of dynamic software architectures
    2005 (engelsk)Rapport (Annet vitenskapelig)
    Abstract [en]

    A recent trend in computing is towards more autonomous software systems. This is mainly driven by that our daily life more and more depends on computers and software. Areas like ubiquitous computing with small (embedded) systems and their antipodes world-wide distributed systems require different support in terms of flexibility and availability. Systems must be able to adapt to changes in the environment, including self-healing and adaptation. Users can not take on the tedious task of constantly maintaining and updating their software packages to each and every change. This paper discusses one of the foundations for developers of these systems, dynamic architecture. We investigate the existing body of work in the area and identify dimensions and aspects of dynamically changing arcbitectures. Continuing, we use this division creating a dassification of four fundamental dynamic architecture dasses: Dynamic, Adaptive, Constructive, and Reflective. These four are presented as architectural patterns and their possible application areas are discussed.

    Publisher
    s. 51
    Serie
    Technical report, ISSN 1650-2647 ; 04122
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-12965 (URN)
    Tilgjengelig fra: 2008-04-01 Laget: 2008-04-01 Sist oppdatert: 2012-11-20
    2. Development and use of dynamic product-line architectures
    Åpne denne publikasjonen i ny fane eller vindu >>Development and use of dynamic product-line architectures
    2005 (engelsk)Inngår i: IEE Proceedings - Software, ISSN 1462-5970, E-ISSN 1463-9831, Vol. 152, nr 1, s. 15-28Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Software product families are used to improve reuse and shorten lead times, with several positive side effects such as improved quality and lowered cost. This paper presents the results of a case study conducted at four Swedish companies that are involved in either the development of or development with a software product family. We identify and discuss several issues such as inter-organizational development of platforms, platforms that employ dynamism, and platforms as a vehicle to achieve certain quality attributes. We analyze issues and demonstrate how these can be deduced to shortcomings in scoping and variability management for non-functional quality attributes and dynamic architectures.

    Emneord
    decision making; object-oriented methods; software architecture; software development management; software libraries; software prototyping; software quality; software reusability; software product families; Swedish companies; inter-organisational development; dynamic reconfiguration; dynamic product-line architectures
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-12966 (URN)10.1049/ip-sen:20041007 (DOI)
    Tilgjengelig fra: 2008-04-01 Laget: 2008-04-01 Sist oppdatert: 2017-12-13
    3. A deployment system for pervasive computing
    Åpne denne publikasjonen i ny fane eller vindu >>A deployment system for pervasive computing
    2000 (engelsk)Inngår i: Proceedings. International Conference on  Software Maintenance, 2000., 2000, s. 262-270Konferansepaper, Publicerat paper (Annet vitenskapelig)
    Abstract [en]

    Software has for a long time been used for controlling different systems. Today, there is a trend towards integrating more software in consumer electronics, home appliances, cars etc. Suddenly software is moving from traditional environments, such as the desktop computer into new and unknown territory. This will influence many aspects of the software engineering process; above all, several new problems have arisen in the domain of software deployment. How can software be effectively deployed in these environments? Current deployment strategies are not directly applicable. The paper discusses problems with current deployment models and proposes a new, modified model. A deployment model for pervasive computing must support component based development, different delivery models, and installation and activation strategies. Support for dynamic installation and activation (i.e. making modifications without de-activating the software), is especially important. We introduce a prototype implementation, the Java Distributed Run-time Updating Management System (JDRUMS), which we have used as a vehicle for eliciting requirements for our deployment model

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-12967 (URN)10.1109/ICSM.2000.883058 (DOI)0-7695-0753-0 (ISBN)
    Konferanse
    International Conference on Software Maintenance (ICSM' 2000), San José, October
    Tilgjengelig fra: 2008-04-01 Laget: 2008-04-01 Sist oppdatert: 2012-11-20
    4. Reconfigurable scientific applications on GRID services
    Åpne denne publikasjonen i ny fane eller vindu >>Reconfigurable scientific applications on GRID services
    2005 (engelsk)Inngår i: Advances in Grid Computing: European Grid Conference, Amsterdam, The Netherlands, February 14-16, 2005, Revised Selected Papers / [ed] Peter M. A. Sloot, Alfons G. Hoekstra, Thierry Priol, Alexander Reinefeld, Marian Bubak, Springer Berlin/Heidelberg, 2005, s. 813-822Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    This paper proposes a runtime environment for dynamically changing, parallel scientific applications. This kind of applications is motivated by the LOFAR/LOIS project aiming at a multidisciplinary research platform for natural scientists and engineers. The dynamic infrastructure in turn is than mapped to Grid Services environments.

    sted, utgiver, år, opplag, sider
    Springer Berlin/Heidelberg, 2005
    Serie
    Lecture Notes in Computer Science, ISSN 0302-9743 ; 3470
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-12968 (URN)10.1007/11508380_83 (DOI)978-3-540-26918-2 (ISBN)978-3-540-32036-4 (ISBN)
    Tilgjengelig fra: 2008-04-01 Laget: 2008-04-01 Sist oppdatert: 2012-12-11
  • 212.
    Andersson, Jesper
    et al.
    MSI Universitet Växjö, Sweden.
    Ericsson, Morgan
    MSI Universitet Växjö, Sweden.
    Kessler, Christoph
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, PELAB - Laboratoriet för programmeringsomgivningar.
    Löwe, Welf
    MSI Universitet Växjö, Sweden.
    Profile-Guided Composition2008Inngår i: 7th Int. Symposium on Software Composition SC 2008,2008, Berlin: Springer , 2008, s. 157-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We present an approach that generates context-aware, optimized libraries of algorithms and data structures. The search space contains all combinations of implementation variants of algorithms and data structures including dynamically switching and converting between them. Based on profiling, the best implementation for a certain context is precomputed at deployment time and selected at runtime. In our experiments, the profile-guided composition outperforms the individual variants in almost all cases.

  • 213.
    Andersson, Johan
    Linköpings universitet, Institutionen för systemteknik.
    Rekommendationer för införande av public key infrastructure2002Independent thesis Basic level (professional degree)Oppgave
    Abstract [en]

    The use of insecure networks -such as the Internet- to send and receive information has made the need for preventing unauthorised people reading it yet more important. One of the easiest way to do this is through public key cryptography. However, the problem with this solution is how to tie a specific public key to a certain subject. This is solved by letting a trusted third party issue a certificate that holds, as a minimum, the name of the subject and the subject's public key along with the issuer's digital signature on the information. The rules we make for issuing, revoking and verifying of certificates and the entities that are being used to do so are called PKI - Public Key Infrastructure. In this thesis we shall se what PKI really is in a more detailed way and which entities it constitutes of. We will also investigate some of the areas in which we could make use of it, for instance secure e-mail and virtual private networks. Next, we will look into some of the drawbacks with PKI and what you should think of in order to aviod these. Finally, we'll give recommendations for the implementation itself. As for the theory of cryptography, the basics is presented to the interested reader in a separate appendix.

  • 214.
    Andersson, Johan
    et al.
    Linköpings universitet, Institutionen för datavetenskap.
    Andersson, Katrin
    Linköpings universitet, Institutionen för datavetenskap.
    Automated Software Testing in an Embedded Real-Time System2007Independent thesis Basic level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Today, automated software testing has been implemented successfully in many systems, however there does still exist relatively unexplored areas as how automated testing can be implemented in a real-time embedded system. This problem has been the foundation for the work in this master thesis, to investigate the possibility to implement an automated software testing process for the testing of an embedded real-time system at IVU Traffic Technologies AG in Aachen, Germany.

    The system that has been the test object is the on board system i.box.

    This report contains the result of a literature study in order to present the foundation behind the solution to the problem of the thesis. Questions answered in the study are: when to automate, how to automate and which traps should one avoid when implementing an automated software testing process in an embedded system.

    The process of automating the manual process has contained steps as constructing test cases for automated testing, analysing whether an existing tool should be used or a unique test system needs to be developed. The analysis, based on the requirements on the test system, the literature study and an investigation of available test tools, lead to the development of a new test tool. Due to limited devlopement time and characterstics of the i.box, the new tool was built based on post execution evaluation. The tool was therefore divided into two parts, a part that executed the test and a part that evaluated the result. By implementing an automated test tool it has been proved that it is possible to automate the test process at system test level in the i.box.

  • 215.
    Andersson, Jonas
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    Using React Native and AWS Lambda for cross-platform development in a startup2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    When developing mobile applications, the tradition has been to write code specific (native) for each platform they are running on. Usually it’s about writing two separate applications for the biggest platforms, Android and iOS. There exist alternatives to this approach that uses the same code for different platforms.

    React Native is a relatively new cross-platform development framework that makes it possible to use the same code for application to Android and iOS. It also uses native UI-elements as a possible solution for performance issues that is often associated with cross-plattform development.

    This thesis evaluates React Native and compares it against native Android. The implementation is done by replicating the main functionality from a social media application written as a native Android application. However, the application is not made as an exact replica since that could limit the solutions in React Native. The evaluation is done in a Startup company and therefore focuses on aspects important in a Startup.

    Another issue when developing a mobile application is what type of backend that shall be used. Performance, scalability and complexity are all important aspects when choosing a framework or language as a base for the backend architecture.There do exist theoretical frameworks that could be used when building the backend. However, these frameworks require resources that are often missing in a Startup.

    AWS Lambda is a platform that claims to be a cost-effective way of building a scalable application. In this thesis AWS Lambda is evaluated to see if it can be used to create an automatically scaled backend for this type of social media application.

    The conclusion of the React Native evaluation is that it can be a suitable alternative to native Android development. If the team has previous experience in web development but lack experience in mobile application development it can be a wise choice since it removes the need to learn two frameworks in native Android and native iOS development. React Native is also good to fast create functional prototypes which can be shown to potential investors. The biggest drawback is performance in animations. However, there are often ways to work around that. In our case this drawback did not affect the user experience of the end application.

    The evaluation of AWS Lambda concludes that it is not for every project. In this thesis, the application was a bit too database heavy and therefore the autoscaling ability did not work properly. However, for a service that needs a lot of computing power, AWS Lambda could be a good fit. It could also be a suitable alternative if someone in the team has previous experience in the AWS environment.

  • 216.
    Andersson, Jonas
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer.
    Karlsson, David
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer.
    Improving rendering times of Autodesk Maya Fluids using the GPU2008Independent thesis Basic level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Fluid simulation is today a hot topic in computer graphics. New highly optimized algorithms have allowed complex systems to be simulated in high speed. This master thesis describes how the graphics processing unit, found in most computer workstations, can be used to optimize the rendering of volumetric fluids. The main aim of the work has been to develop a software that is capable of rendering fluids in high quality and with high performance using OpenGL. The software was developed at Filmgate, a digital effects company in Göteborg, and much time was spent making the interface and the workflow easy to use for people familiar with Autodesk Maya. The project resulted in a standalone rendering application, together with a set of plugins to exchange data between Maya and our renderer.

    Most of the goals have been reached when it comes to rendering features. The performance bottleneck turned out to be reading data from disc and this is an area suitable for future development of the software.

  • 217.
    Andersson, Jonatan
    Linköpings universitet, Institutionen för datavetenskap, Interaktiva och kognitiva system.
    Assessment and Improvement of Initial Learnability in Complex Systems: A Qualitative Study to Promote Intuitive Software Development2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This Master’s Thesis aimed to assess and propose improvements for initial learnability in Sectra AB’s Picture Archiving Communication System (PACS) by integrating usability engineering and agile software development. Assessing initial learnability and re-designing complex systems is difficult as they have a high skill cap and take longer time to learn in comparison to simpler ones. Further, companies that use agile methodologies often focus on completing small items which might hide the overarching vision of a product that can lead to usability problems. While there are several methods for assessing usability, no research has specifically focused on assessing initial learnability in complex systems. This study however investigates how this may be achieved by combining current methodologies for measuring learnability with usability engineering and agile software development. Initial learnability issues and needs were assessed after evaluating Sectra PACS using 5 participants and analysed using impact mapping as well as conducting a focus group within the organisation that owns the product.

  • 218.
    Andersson, Jonatan
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Filosofiska fakulteten.
    Design och utkast av ett informationssystem för akutkliniken vid Karolinska Sjukhuset: Design samt utvärdering av prototyp för akutpatienter i väntan på vård2014Independent thesis Basic level (degree of Bachelor), 12 poäng / 18 hpOppgave
    Abstract [sv]

    På Karolinska Sjukhusets akutklinik i Solna har man upplevt problem med att personalen får lägga mycket tid på att besvara på patienters frågor som man många gånger tror beror på brist av information. Syftet med studien var att visa på hur ett informationssystem skulle kunna öka den s.k. informationssystems-framgången för Karolinska Sjukhuset med fokus på kopplingen mellan organisationen och patienterna. Detta gjordes genom att skapa två prototyper med hjälp av Adobe Photoshop, Illustrator samt Axure RP som sedan kördes via          en iPhone. Studien ämnade även utvärdera dessa produkter för att hitta eventuella användbarhetsproblem som kan komma att sänka en potentiell användarens nöjdhet. Detta gjorde med hjälp av ett tänka-högt-protokoll som kompletterades av en SUS-enkät.

     

    Studien resulterade i en klargörande analys om vad som var bra- respektive dåligt med de olika prototyperna samt hur de bör tillämpas och vilka resultat det kan få för patienterna, personalen samt Karolinska Sjukhuset som organisation. Det visade sig att en mobilapplikation var något som försöksdeltagarna uppskattade samt tyckte var nödvändigt för att bidra till ett förbättrat informationsflöde på akutkliniken. Vidare bör man dock fortsätta att användbarhetstesta produkten samt experimentera med olika typer med informationspresentation för att optimera gränssnittet samt göra produkten uppdaterad och intressant. 

  • 219.
    Andersson, Jonny
    Linköpings universitet, Institutionen för systemteknik.
    Automatic test vector generation and coverage analysis in model-based software development2005Independent thesis Basic level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Thorough testing of software is necessary to assure the quality of a product before it is released. The testing process requires substantial resources in software development. Model-based software development provides new possibilities to automate parts of the testing process. By automating tests, valuable time can be saved. This thesis focuses on different ways to utilize models for automatic generation of test vectors and how test coverage analysis can be used to assure the quality of a test suite or to find "dead code" in a model. Different test-automation techniques have been investigated and applied to a model of an adaptive cruise control system (ACC) used at Scania. Source code has been generated automatically from the model, model coverage and code coverage has therefore been compared. The work with this thesis resulted in a new method to create test vectors for models based on a combinatorial test technique.

  • 220.
    Andersson, Julia
    et al.
    Linköpings universitet, Institutionen för datavetenskap.
    Hultqvist, Andreas
    Linköpings universitet, Institutionen för datavetenskap.
    Video quality encoding characterization and comparison2019Independent thesis Basic level (degree of Bachelor), 10,5 poäng / 16 hpOppgave
    Abstract [en]

    Adaptive streaming is a popular technique that allows quality adaption for videos based on the current playback conditions. The purpose of this thesis is to investigate how chunks in video files downloaded from YouTube correlate to each other. We investigate how the chunk size characteristics depend on the category and encoding of the video. The main focus is to analyze the chunk sizes of the video, focusing on distinctness between 360$^\circ$ and 2D videos. This is performed using the YouTube API. The videos are downloaded and analysed using youtube-dl and mkv-info. The results show that chunk sizes for adjacent qualities have higher correlation and that videos having a similarity between scenes have higher correlation. In addition, 360$^\circ$ videos differ primarily from regular 2D videos by the amount of qualities used and a generally higher correlation for all qualities.

  • 221.
    Andersson, Kaisa
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Björk, Carolina
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Specific conditions for marketing of non-profit organizations conducting fundraising2013Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [en]

    Många ideella organisationer behöver bidrag och stöd för att kunna bedriva sitt arbete. Därmed blir det viktigt att vara synliga och sticka ut från mängden för att få människors stöd. Syftet med denna studie är att undersöka specifika förutsättningar för marknadsföring av ideella organisationer som bedriver insamling i Sverige. Genom kvalitativa intervjuer undersöktes hur väl Barncancerfondens och Kvinna till Kvinnas uppfattningar överensstämmer med teorier som finns inom området. Slutsatser som överensstämde med litteraturen var att ideella organisationer ofta har som mål att nå en mycket bred publik eller till och med hela allmänheten. Men studien visar även att Barncancerfonden och Kvinna till Kvinna arbetar strategiskt med målgrupper för att rikta insamling och informationsarbete, trots att det finns en vilja att nå ut brett. Inom ideella organisationer är det även svårt att modifiera budskapet, eftersom det måste spegla verksamheten. Hur organisationen påverkas av detta beror delvis på vilken typ av ämne som organisationen berör eftersom det med ett intresseväckande ämne är lättare att nå ut. En annan specifik förutsättning är att gåvor ofta är en osynlig handling som gynnar någon annan. Avsaknaden av produkt nämns av organisationerna som något marknadsföringen måste bemöta, vilket kan ske på olika sätt. Ideella verksamheter normalt uppfattas ha ett gott syfte vilket gör allmänheten mer mottaglig för budskapen.

  • 222.
    Andersson, Karl
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    Mapping out dependencies in network components in critical infrastructure2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Companies that operate with critical infrastructure face a growing threat from cyber-attacks while at the same time the development in the business is rapidly moving towards a higher level of digitalization. A common type of system in critical infrastructure is supervisory control and data acquisition systems, these systems have properties that can affect their security and will therefore serve as the basis for this thesis work. To stay protected despite systems changes, companies need to make risk assessments in order to analyze how changes will affect the overall system. One thing that is important to focus on is dependencies within the system, this means that not only interaction among computers and networks are concerned but instead a more holistic view of the system need to be considered. This thesis aims to aid the process of a future risk assessment by providing a methodology to be used as a preparatory step before a risk assessment by describing the current situation of the system. This is done by evaluating two system modeling approaches, and also by proposing a number of perspectives that each provides different kind of information about the system’s dependencies. These perspectives are then evaluated by creating system models and dependency graphs, and discussing the outcomes with experts in a utility company to find out their applicability. According to the experts, the proposed perspectives have promising properties that can be useful in future risk assessments as well as in other scenarios. Moreover, the evaluated modeling approaches got positive comments during evaluation and are considered to serve their purpose.

  • 223.
    Andersson, Karl
    et al.
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska fakulteten.
    Odlander, Marcus
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska fakulteten.
    Detecting a Distributed Denial-of-Service Attack Using Speed Test Data: A Case Study on an Attack with Nationwide Impact2015Independent thesis Basic level (degree of Bachelor), 10,5 poäng / 16 hpOppgave
    Abstract [en]

    This thesis presents a case study that investigates a large Distributed Denial of Service (DDoS) attack and how it affected speed tests observed by the crowd-based speed test application Bredbandskollen.  Furthermore, the thesis also investigates the possibility of using crowd-based speed tests as a method to detect a DDoS attack. This method has very low overhead which makes it an interesting complement to other methods. This thesis also shows that there was a significant deviation in the number of measurements during the DDoS attack considered in the case study compared to the year average. Furthermore, the measurements of the peak day of the attack had a higher average download speed than the year average. Whereas the higher download speed observation at first may appear non-intuitive, we briefly discuss potential explanations and how such positive anomalies could potentially be used to detect attacks. Detecting DDoS attacks early can lead to earlier recognition of network problems which can aid Internet Service Providers (ISPs) in maintaining the availability of their networks.

  • 224.
    Andersson, Leo
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling.
    Sjöberg, Gustav
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling.
    Spelifiering: En fallstudie med fokus på framställning och slutgiltigt värde2014Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    This bachelor thesis is an exploratory investigation about the phenomenon 'Gamification', which by some definitions is about implementing game elements into non-game contexts. For example exercise services as Runkeeper and Nike Plus who both are available on android and iOS platforms. This study is mainly about the potential value of gamified systems and services for companies and its users and how such a system or service is developed. The thesis also discusses the development aspect of gamified systems in order to give the reader a more ‘in depth’ understanding about the phenomenon. This has been achieved by visiting businesses, by studying marketing – and motivational theories and then connect those theories to the theory about gamification. After this case study have we been able to draw the conclusion that an essential part of gamification is the occurrence of real time calculations and game elements. This means that high demands are put on the developer who has to have good knowledge about the different game elements and when these elements are applicable. The system architect has to work with the other developers in order to be able to pick the best software and hardware that can meet the demands of the service. Fast calculations and high performance are critical factors to be able to offer a good experience to the users of the service. We have also been able to conclude that the guests that has been using the service MySkiStar has become more active in their skiing. Exactly what types of business and customer values MySkiStar as a gamified service has generated is not possible to specify. The reason for this is that SkiStar has not done any follow up in order to map the different areas that we have been interested in. The final value of such a service is therefore merely based on speculations until an investigation has been done to map the value. 

  • 225.
    Andersson, Lina
    Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Införande av ett dokumenthanteringssystem på SMHI2002Independent thesis Basic level (professional degree)Oppgave
    Abstract [sv]

    Den ostrukturerade dokumenthantering, som idag förekommer på avdelningen Ida på företaget SMHI, gav upphov till detta examensarbete.

    Ett dokumenthanteringssystem har införskaffats till avdelningen. Dokumenthanteringssystemet är en produkt från Microsoft med namnet SharePoint Portal Server (SPS), vilken levererats av WM-data. SPS är relativt ny på marknaden, vilket gör att erfarenheter saknas kring produkten.

    Syftet med dokumenthanteringssystemet är att samla alla dokument på samma plats, vilket gör dem lätt tillgängliga för alla berörda. Förhoppningsvis kommer införandet av ett dokumenthanteringssystem också att innebära att belastningen på övriga filtjänster minskar.

    Examensarbetet bestod i att göra ett förslag till både dokumentstruktur och metadata, som senare skulle implementeras i SPS.

    Dokumentstrukturen skapades med hänsyn till SMHI:s systemförvaltningsmodell. För att vara säker på att strukturen och metadatan skulle fungera i verkligheten, och inte bara på papperet, genomfördes två pilotsystem. Med hjälp av dessa gjordes några förändringar i både struktur och metadata.

    Dokumenthanteringssystemets alla funktioner har under examensarbetets gång utforskats med hjälp av manualer.Vilka dessa funktioner är och hur de fungerar beskrivs i denna rapport.

    Vid användandet av SPS har en hel del brister upptäckts i programvaran. Bristerna är av större eller mindre betydelse för SMHI:s behov. Dessa har dock anmälts till Microsoft, och man hoppas därmed att de blir åtgärdade till nästa version av SPS.

    Examensarbetet har resulterat i ett förslag till dokumentstruktur och ett förslag till metadata. Förslagen implementerades också i dokumenthanteringssystemet, eftersom tiden medgav detta.

  • 226.
    Andersson, Magnus
    et al.
    Linköpings universitet, Institutionen för systemteknik.
    Severinson, Kristofer
    Linköpings universitet, Institutionen för systemteknik.
    Hydroakustisk kommunikation med bandspridningsteknik2004Independent thesis Basic level (professional degree)Oppgave
    Abstract [en]

    This thesis investigates techniques for stealth hydroacoustic communication using spread spectrum. The Swedish naval defense organisations have a vision that all their units should be able to communicate with each other, even between underwater vehicles. But the properties of water makes it a complex channel to use for wireless communications. Radiomagnetic waves have very limited range in water, therefore acoustic waves are used.

    In this report the basics of wireless communication systems are described including source coding, channel coding, modulation techniques as well as different techniques for spread spectrum. The fundamental principle for all spread spectrum systems is to use more bandwidth than necessary to spread the signal energy in the frequency spectrum. This limits the data rate but results in a robust communication link which is difficult to detect, intercept and to jam.

    In addition to the theoretical background, this thesis also gives a brief description of a Matlab system and a VHDL-system that was developed during the project. Finally the results of this project are presented and some suggestions of further developments are given.

  • 227.
    Andersson, Marcus
    Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Cryptographic Key Masking During Run-Time2008Independent thesis Basic level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Many of the products commercially available today contain some form of encrypted or hashed data. It can involve DRM protection, licenses and certificates, signatures or identification information. Regardless of what the data is intended for, it is protected for a reason and may be worth a great deal of money to the owner.

    There are numerous examples of products that have been subject to hacking in the form of simple memory attacks. If the keys are made all too easily extracted, the value of the protected data will soon be lost.

    The aim of the thesis work discussed in this report was to evaluate the vulnerabilities in mobile phones to this sort of attacks and to find possible security enhancements that can be applied. A method is proposed where masking will secure the cryptology keys while they reside in the memory.

    Different masks are developed and tested - The effects on performance are measured and the security is evaluated.

    The thesis work concludes that it is possible to implement masking on many of the security functions using keys and that the masks will increase security. The conclusion also states that the time consumption of the masking heavily depends on which mask that is used and that the masking could be applied in such a way that the level of masking can be varied.

  • 228.
    Andersson, Marcus
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska fakulteten.
    Gränssnittsdesign för kundnöjdhet och administration2015Independent thesis Basic level (degree of Bachelor), 10,5 poäng / 16 hpOppgave
    Abstract [sv]

    Kundnöjdhet är en stor inkomstkälla för företag. Det finns många sätt att mäta kundnöjdhet och ett av de nyaste sätten är genom en digital monter placerad i fysisk butik. Denna studie ämnar undersöka hur gränssnitt till en undersökningsapplikation skall utformas för att tilltala en bred målgrupp att lämna omdömen och hur ett användbart gränssnitt till den administrativa sidan för denna applikation kan utformas. Resultaten från utvärderingen av undersökningsgränssnittet visar att det finns designelement som tilltalar vissa användare mer än andra. Detta ger en fingervisning om hur design kan utformas för att vara tilltalande för användarna att lämna omdömen via teknisk plattform. Utvärderingen av administrationsgränssnittet visade att genom att följa teorin kan ett lättanvändbart administrationsgränssnitt skapas.

  • 229.
    Andersson, Maria
    et al.
    Division of Information Systems, FOI, Swedish Defence Research Agency, Linköping, Sweden.
    Ntalampiras, Stavros
    Department of Electrical and Computer Engineering, University of Patras, Patras, Greece.
    Ganchev, Todor
    Department of Electrical and Computer Engineering, University of Patras, Patras, Greece.
    Rydell, Joakim
    Division of Information Systems, FOI, Swedish Defence Research Agency, Linköping, Sweden.
    Ahlberg, Jörgen
    Division of Information Systems, FOI, Swedish Defence Research Agency, Linköping, Sweden.
    Fakotakis, Nikos
    Department of Electrical and Computer Engineering, University of Patras, Patras, Greece.
    Fusion of Acoustic and Optical Sensor Data for Automatic Fight Detection in Urban Environments2010Inngår i: Information Fusion (FUSION), 2010 13th Conference on, IEEE conference proceedings, 2010, s. 1-8Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We propose a two-stage method for detection of abnormal behaviours, such as aggression and fights in urban environment, which is applicable to operator support in surveillance applications. The proposed method is based on fusion of evidence from audio and optical sensors. In the first stage, a number of modalityspecific detectors perform recognition of low-level events. Their outputs act as input to the second stage, which performs fusion and disambiguation of the firststage detections. Experimental evaluation on scenes from the outdoor part of the PROMETHEUS database demonstrated the practical viability of the proposed approach. We report a fight detection rate of 81% when both audio and optical information are used. Reduced performance is observed when evidence from audio data is excluded from the fusion process. Finally, in the case when only evidence from one camera is used for detecting the fights, the recognition performance is poor. 

  • 230.
    Andersson, Maria
    et al.
    FOI Swedish Defence Research Agency.
    Rydell, Joakim
    FOI Swedish Defence Research Agency.
    Ahlberg, Jörgen
    Linköpings universitet, Institutionen för systemteknik, Datorseende. Linköpings universitet, Tekniska fakulteten. FOI Swedish Defence Research Agency.
    Estimation of crowd behaviour using sensor networks and sensor fusion2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Commonly, surveillance operators are today monitoring a large number of CCTV screens, trying to solve the complex cognitive tasks of analyzing crowd behavior and detecting threats and other abnormal behavior. Information overload is a rule rather than an exception. Moreover, CCTV footage lacks important indicators revealing certain threats, and can also in other respects be complemented by data from other sensors. This article presents an approach to automatically interpret sensor data and estimate behaviors of groups of people in order to provide the operator with relevant warnings. We use data from distributed heterogeneous sensors (visual cameras and a thermal infrared camera), and process the sensor data using detection algorithms. The extracted features are fed into a hidden Markov model in order to model normal behavior and detect deviations. We also discuss the use of radars for weapon detection.

  • 231.
    Andersson, Matilda
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Filosofiska fakulteten.
    Vägen mot en guideapplikation: Designförslag till en guide i kulturhistorisk miljö2012Independent thesis Basic level (degree of Bachelor), 12 poäng / 18 hpOppgave
    Abstract [sv]

    Detta projekt har skapat en design till en applikation, vars mål är att få människor i närnatur och samtidigt möjliggöra för dem att lära sig mer om den kulturhistoria denna natur har att bjuda.I projektet har designen till en guideapplikation för användning i miljö med kulturhistoriska arv undersökts och tagits fram. Projektet är en fallstudie och använder ramverket Minnesmark som en grund för designen.Designen är framtagen genom att använda en målinriktad designmetod och designprocess av Goodwin(2009). Med detta menas att personor och scenarier har varit de främsta verktygen för att generera krav till designen. Krav baseras även på ramverket Minnesmarks möjligheter och begränsningar. Vidare krav kommer även från intervjuer med två olika guider.En första design; en prototyp, utvärderades av åtta personer för att förbättra designen. Utifrån dessa förbättringar togs den slutgiltiga designen fram som består av fem olika delar vilka tillsammans skapar en applikation att använda i miljö med kulturhistoriska arv.

  • 232.
    Andersson, Mats
    Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Artificiella immunsystem kan inte ge säkrare datorsystem2005Independent thesis Basic level (degree of Bachelor)Oppgave
    Abstract [sv]

    Forskningen om artificiella immunsystem försöker använda människans immunförsvar som modell för hur ett datorsystem på egen hand skall kunna försvara sig mot okänt inkräktande, till skillnad från traditionella antiviruslösningar som bygger på manuell detektion av nya virus.

    Denna uppsats hävdar att människans immunförsvar inte är någon relevant modell för ett artificiellt immunsystem som tillgodoser användarnas behov av säkrare datorsystem, eftersom det finns skillnader i hur datorsystem och människor principiellt fungerar.

    Ett antal hypoteser ställs upp som beläggs med data från den immunologiska forskningen, Microsofts säkerhetsbulletiner, samt virusbeskrivningar från antivirusföretaget Sophos. Hypoteserna kopplas ihop i en slutledningskedja som visar att de hypoteser som relaterar till datorsystem, inte är förenliga med de hypoteser som relaterar till människans immunförsvar, om det artificiella immunsystemet skall tillgodose användarnas behov av säkrare datorsystem.

    Forskningen om artificiella immunsystem diskuteras, där de principer och antaganden som de olika lösningarna bygger på monteras ned genom att implicita inkonsistenser görs explicita. Uppsatsen avslutas med en belysning av varför hypoteserna egentligen går att belägga, där grundbulten är att människans immunförsvar skyddar behovet hos sin värd, den mänskliga individen, till skillnad från det artificiella immunsystemet, som inte är tänkt att skydda behovet hos sin värd, själva datorsystemet, utan snarare behovet hos användaren av datorsystemet.

  • 233.
    Andersson, Mikael
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Utvärdering av ramverket JQuery for mobile2012Independent thesis Basic level (degree of Bachelor), 10,5 poäng / 16 hpOppgave
    Abstract [sv]

    Examensarbetet har utförts på Lawson, som idag gör en satsning mot de mobila användarna. Då det idag finns många olika typer av enheter, webbläsare och operativsystem utvecklas det mobila applikationer till varje plattform vilket medför stora kostnader och längre utvecklingstider. Den här rapporten är skriven i syfte att se över vad det finns för möjligheter att använda ny teknik som HTML5 och CSS3 tillsammans med ramverket jQuery for mobile för att utveckla webbapplikationer.

    För att visa på funktionaliteten och vad man kan göra så har två exempelapplikationer tagits fram och testas på flera olika plattformar/enheter, bland annat en iPad och en Samsung Galaxy Tab 8.9. Koden för dessa applikationer finns som bilaga i rapporten.

    Målet var att se över vad det fanns för stöd för swipes, enhetlig native-design/känsla, kunna använda enhetens kamera och GPS. En hel del, bland annat swipes, GPS och lokal lagring, går att lösa med HTML5 och jQuery for mobile. Men vill man komma åt ännu mer hårdvarunära funktionalitet, så som kamera, så behöver man lägga på ett ramverk, i mitt fall valde jag att utöka arbetet och även se över ramverket Cordova. Det ramverket gjorde att man kunde komma åt kameran i mobilen.

    Slutsatsen av undersökningen är att det går att göra mycket med jQuery for mobile som bygger på webbtekniker som JavaScript, HTML5 och CSS3. Men för att få hårdvarunära funktionalitet behövs det användas en annan typ av ramverk, t.ex. Cordova, som erbjuder ett API mot själva hårdvarufunktionaliteten. För att den funktionaliteten sedan ska fungera måste applikationen kompileras, på samma sätt som en native-applikation. Dock så använder Cordova samma teknik som ramverket jQuery for mobile, så kostnader och utvecklingstid kan hållas nere. Vid små applikationer fungerar det utmärkt att använda denna teknik men vid större kan man behöva göra lite fler prestandatester innan man säkert kan avgöra om tekniken är lämplig.

  • 234.
    Andersson, Mikael
    et al.
    Linköpings universitet, Institutionen för systemteknik.
    Karlström, Per
    Linköpings universitet, Institutionen för systemteknik.
    Parallel JPEG Processing with a Hardware Accelerated DSP Processor2004Independent thesis Basic level (professional degree)Oppgave
    Abstract [en]

    This thesis describes the design of fast JPEG processing accelerators for a DSP processor.

    Certain computation tasks are moved from the DSP processor to hardware accelerators. The accelerators are slave co processing machines and are controlled via a new instruction set. The clock cycle and power consumption is reduced by utilizing the custom built hardware. The hardware can perform the tasks in fewer clock cycles and several tasks can run in parallel. This will reduce the total number of clock cycles needed.

    First a decoder and an encoder were implemented in DSP assembler. The cycle consumption of the parts was measured and from this the hardware/software partitioning was done. Behavioral models of the accelerators were then written in C++ and the assembly code was modified to work with the new hardware. Finally, the accelerators were implemented using Verilog.

    Extension of the accelerator instructions was given following a custom design flow.

  • 235.
    Andersson Naesseth, Christian
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Machine learning using approximate inference: Variational and sequential Monte Carlo methods2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Automatic decision making and pattern recognition under uncertainty are difficult tasks that are ubiquitous in our everyday life. The systems we design, and technology we develop, requires us to coherently represent and work with uncertainty in data. Probabilistic models and probabilistic inference gives us a powerful framework for solving this problem. Using this framework, while enticing, results in difficult-to-compute integrals and probabilities when conditioning on the observed data. This means we have a need for approximate inference, methods that solves the problem approximately using a systematic approach. In this thesis we develop new methods for efficient approximate inference in probabilistic models.

    There are generally two approaches to approximate inference, variational methods and Monte Carlo methods. In Monte Carlo methods we use a large number of random samples to approximate the integral of interest. With variational methods, on the other hand, we turn the integration problem into that of an optimization problem. We develop algorithms of both types and bridge the gap between them.

    First, we present a self-contained tutorial to the popular sequential Monte Carlo (SMC) class of methods. Next, we propose new algorithms and applications based on SMC for approximate inference in probabilistic graphical models. We derive nested sequential Monte Carlo, a new algorithm particularly well suited for inference in a large class of high-dimensional probabilistic models. Then, inspired by similar ideas we derive interacting particle Markov chain Monte Carlo to make use of parallelization to speed up approximate inference for universal probabilistic programming languages. After that, we show how we can make use of the rejection sampling process when generating gamma distributed random variables to speed up variational inference. Finally, we bridge the gap between SMC and variational methods by developing variational sequential Monte Carlo, a new flexible family of variational approximations.

    Delarbeid
    1. Capacity estimation of two-dimensional channels using Sequential Monte Carlo
    Åpne denne publikasjonen i ny fane eller vindu >>Capacity estimation of two-dimensional channels using Sequential Monte Carlo
    2014 (engelsk)Inngår i: 2014 IEEE Information Theory Workshop, 2014, s. 431-435Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    We derive a new Sequential-Monte-Carlo-based algorithm to estimate the capacity of two-dimensional channel models. The focus is on computing the noiseless capacity of the 2-D (1, ∞) run-length limited constrained channel, but the underlying idea is generally applicable. The proposed algorithm is profiled against a state-of-the-art method, yielding more than an order of magnitude improvement in estimation accuracy for a given computation time.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-112966 (URN)10.1109/ITW.2014.6970868 (DOI)
    Konferanse
    Information Theory Workshop
    Tilgjengelig fra: 2015-01-06 Laget: 2015-01-06 Sist oppdatert: 2018-11-09
    2. Sequential Monte Carlo for Graphical Models
    Åpne denne publikasjonen i ny fane eller vindu >>Sequential Monte Carlo for Graphical Models
    2014 (engelsk)Inngår i: Advances in Neural Information Processing Systems, 2014, s. 1862-1870Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    We propose a new framework for how to use sequential Monte Carlo (SMC) algorithms for inference in probabilistic graphical models (PGM). Via a sequential decomposition of the PGM we find a sequence of auxiliary distributions defined on a monotonically increasing sequence of probability spaces. By targeting these auxiliary distributions using SMC we are able to approximate the full joint distribution defined by the PGM. One of the key merits of the SMC sampler is that it provides an unbiased estimate of the partition function of the model. We also show how it can be used within a particle Markov chain Monte Carlo framework in order to construct high-dimensional block-sampling algorithms for general PGMs.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-112967 (URN)
    Konferanse
    Neural Information Processing Systems (NIPS)
    Tilgjengelig fra: 2015-01-06 Laget: 2015-01-06 Sist oppdatert: 2018-11-09bibliografisk kontrollert
    3. Nested Sequential Monte Carlo Methods
    Åpne denne publikasjonen i ny fane eller vindu >>Nested Sequential Monte Carlo Methods
    2015 (engelsk)Inngår i: Proceedings of The 32nd International Conference on Machine Learning / [ed] Francis Bach, David Blei, Journal of Machine Learning Research (Online) , 2015, Vol. 37, s. 1292-1301Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    We propose nested sequential Monte Carlo (NSMC), a methodology to sample from sequences of probability distributions, even where the random variables are high-dimensional. NSMC generalises the SMC framework by requiring only approximate, properly weighted, samples from the SMC proposal distribution, while still resulting in a correct SMC algorithm. Furthermore, NSMC can in itself be used to produce such properly weighted samples. Consequently, one NSMC sampler can be used to construct an efficient high-dimensional proposal distribution for another NSMC sampler, and this nesting of the algorithm can be done to an arbitrary degree. This allows us to consider complex and high-dimensional models using SMC. We show results that motivate the efficacy of our approach on several filtering problems with dimensions in the order of 100 to 1 000.

    sted, utgiver, år, opplag, sider
    Journal of Machine Learning Research (Online), 2015
    Serie
    JMLR Workshop and Conference Proceedings, ISSN 1938-7228 ; 37
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-122698 (URN)
    Konferanse
    32nd International Conference on Machine Learning, Lille, France, 6-11 July, 2015
    Tilgjengelig fra: 2015-11-16 Laget: 2015-11-16 Sist oppdatert: 2018-11-09bibliografisk kontrollert
    4. Interacting Particle Markov Chain Monte Carlo
    Åpne denne publikasjonen i ny fane eller vindu >>Interacting Particle Markov Chain Monte Carlo
    Vise andre…
    2016 (engelsk)Inngår i: Proceedings of the 33rd International Conference on Machine Learning (ICML), 2016Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    We introduce interacting particle Markov chain Monte Carlo (iPMCMC), a PMCMC method based on an interacting pool of standard and conditional sequential Monte Carlo samplers. Like related methods, iPMCMC is a Markov chain Monte Carlo sampler on an extended space. We present empirical results that show significant improvements in mixing rates relative to both non-interacting PMCMC samplers and a single PMCMC sampler with an equivalent memory and computational budget. An additional advantage of the iPMCMC method is that it is suitable for distributed and multi-core architectures.

    Emneord
    Sequential Monte Carlo, Probabilistic programming, parallelisation
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-130043 (URN)
    Konferanse
    International Conference on Machine Learning (ICML), New York, USA, June 19-24, 2016
    Prosjekter
    CADICS
    Forskningsfinansiär
    Cancer and Allergy Foundation
    Tilgjengelig fra: 2016-07-05 Laget: 2016-07-05 Sist oppdatert: 2018-11-09
    5. Reparameterization Gradients through Acceptance-Rejection Sampling Algorithms
    Åpne denne publikasjonen i ny fane eller vindu >>Reparameterization Gradients through Acceptance-Rejection Sampling Algorithms
    2017 (engelsk)Inngår i: Proceedings of the 20th International Conference on Artificial Intelligence and Statistics, 2017Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    Variational inference using the reparameterization trick has enabled large-scale approximate Bayesian inference in complex probabilistic models, leveraging stochastic optimization to sidestep intractable expectations. The reparameterization trick is applicable when we can simulate a random variable by applying a differentiable deterministic function on an auxiliary random variable whose distribution is fixed. For many distributions of interest (such as the gamma or Dirichlet), simulation of random variables relies on acceptance-rejection sampling. The discontinuity introduced by the accept-reject step means that standard reparameterization tricks are not applicable. We propose a new method that lets us leverage reparameterization gradients even when variables are outputs of a acceptance-rejection sampling algorithm. Our approach enables reparameterization on a larger class of variational distributions. In several studies of real and synthetic data, we show that the variance of the estimator of the gradient is significantly lower than other state-of-the-art methods. This leads to faster convergence of stochastic gradient variational inference.

    Serie
    Proceedings of Machine Learning Research, ISSN 1938-7228 ; 54
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-152645 (URN)
    Konferanse
    Artificial Intelligence and Statistics, 20-22 April 2017, Fort Lauderdale, FL, USA
    Tilgjengelig fra: 2018-11-09 Laget: 2018-11-09 Sist oppdatert: 2018-11-21
    6. Variational Sequential Monte Carlo
    Åpne denne publikasjonen i ny fane eller vindu >>Variational Sequential Monte Carlo
    2018 (engelsk)Inngår i: Proceedings of International Conference on Artificial Intelligence and Statistics, 9-11 April 2018, Playa Blanca, Lanzarote, Canary Islands / [ed] Amos Storkey and Fernando Perez-Cruz, 2018, Vol. 84, s. 968-977Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    Many recent advances in large scale probabilistic inference rely on variational methods. The success of variational approaches depends on (i) formulating a flexible parametric family of distributions, and (ii) optimizing the parameters to find the member of this family that most closely approximates the exact posterior. In this paper we present a new approximating family of distributions, the variational sequential Monte Carlo (VSMC) family, and show how to optimize it in variational inference. VSMC melds variational inference (VI) and sequential Monte Carlo (SMC), providing practitioners with flexible, accurate, and powerful Bayesian inference. The VSMC family is a variational family that can approximate the posterior arbitrarily well, while still allowing for efficient optimization of its parameters. We demonstrate its utility on state space models, stochastic volatility models for financial data, and deep Markov models of brain neural circuits.

    Serie
    Proceedings of Machine Learning Research, ISSN 2640-3498 ; 84
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-152646 (URN)
    Konferanse
    The 21st International Conference on Artificial Intelligence and Statistics, Playa Blanca, Lanzarote, Canary Islands, April 9-11, 2018
    Tilgjengelig fra: 2018-11-09 Laget: 2018-11-09 Sist oppdatert: 2019-11-21bibliografisk kontrollert
  • 236.
    Andersson Naesseth, Christian
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Nowcasting using Microblog Data2012Independent thesis Basic level (degree of Bachelor), 10,5 poäng / 16 hpOppgave
    Abstract [en]

    The explosion of information and user generated content made publicly available through the internet has made it possible to develop new ways of inferring interesting phenomena automatically. Some interesting examples are the spread of a contagious disease, earth quake occurrences, rainfall rates, box office results, stock market fluctuations and many many more. To this end a mathematical framework, based on theory from machine learning, has been employed to show how frequencies of relevant keywords in user generated content can estimate daily rainfall rates of different regions in Sweden using microblog data.

    Microblog data are collected using a microblog crawler. Properties of the data and data collection methods are both discussed extensively. In this thesis three different model types are studied for regression, linear and nonlinear parametric models as well as a nonparametric Gaussian process model. Using cross-validation and optimization the relevant parameters of each model are estimated and the model is evaluated on independent test data. All three models show promising results for nowcasting rainfall rates.

  • 237.
    Andersson Naesseth, Christian
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Linderman, Scott
    Columbia University, New York City, New York, United States.
    Ranganath, Rajesh
    New York University, New York City, New York, United States.
    Blei, David
    Columbia University, New York City, New York, United States.
    Variational Sequential Monte Carlo2018Inngår i: Proceedings of International Conference on Artificial Intelligence and Statistics, 9-11 April 2018, Playa Blanca, Lanzarote, Canary Islands / [ed] Amos Storkey and Fernando Perez-Cruz, 2018, Vol. 84, s. 968-977Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Many recent advances in large scale probabilistic inference rely on variational methods. The success of variational approaches depends on (i) formulating a flexible parametric family of distributions, and (ii) optimizing the parameters to find the member of this family that most closely approximates the exact posterior. In this paper we present a new approximating family of distributions, the variational sequential Monte Carlo (VSMC) family, and show how to optimize it in variational inference. VSMC melds variational inference (VI) and sequential Monte Carlo (SMC), providing practitioners with flexible, accurate, and powerful Bayesian inference. The VSMC family is a variational family that can approximate the posterior arbitrarily well, while still allowing for efficient optimization of its parameters. We demonstrate its utility on state space models, stochastic volatility models for financial data, and deep Markov models of brain neural circuits.

  • 238.
    Andersson Naesseth, Christian
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Lindsten, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Schön, Thomas
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Capacity estimation of two-dimensional channels using Sequential Monte Carlo2014Inngår i: 2014 IEEE Information Theory Workshop, 2014, s. 431-435Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We derive a new Sequential-Monte-Carlo-based algorithm to estimate the capacity of two-dimensional channel models. The focus is on computing the noiseless capacity of the 2-D (1, ∞) run-length limited constrained channel, but the underlying idea is generally applicable. The proposed algorithm is profiled against a state-of-the-art method, yielding more than an order of magnitude improvement in estimation accuracy for a given computation time.

  • 239.
    Andersson Naesseth, Christian
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Lindsten, Fredrik
    The University of Cambridge, Cambridge, United Kingdom.
    Schön, Thomas
    Uppsala University, Uppsala, Sweden.
    Nested Sequential Monte Carlo Methods2015Inngår i: Proceedings of The 32nd International Conference on Machine Learning / [ed] Francis Bach, David Blei, Journal of Machine Learning Research (Online) , 2015, Vol. 37, s. 1292-1301Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We propose nested sequential Monte Carlo (NSMC), a methodology to sample from sequences of probability distributions, even where the random variables are high-dimensional. NSMC generalises the SMC framework by requiring only approximate, properly weighted, samples from the SMC proposal distribution, while still resulting in a correct SMC algorithm. Furthermore, NSMC can in itself be used to produce such properly weighted samples. Consequently, one NSMC sampler can be used to construct an efficient high-dimensional proposal distribution for another NSMC sampler, and this nesting of the algorithm can be done to an arbitrary degree. This allows us to consider complex and high-dimensional models using SMC. We show results that motivate the efficacy of our approach on several filtering problems with dimensions in the order of 100 to 1 000.

  • 240.
    Andersson Naesseth, Christian
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Lindsten, Fredrik
    University of Cambridge, Cambridge, UK.
    Schön, Thomas
    Uppsala University, Uppsala, Sweden.
    Sequential Monte Carlo for Graphical Models2014Inngår i: Advances in Neural Information Processing Systems, 2014, s. 1862-1870Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We propose a new framework for how to use sequential Monte Carlo (SMC) algorithms for inference in probabilistic graphical models (PGM). Via a sequential decomposition of the PGM we find a sequence of auxiliary distributions defined on a monotonically increasing sequence of probability spaces. By targeting these auxiliary distributions using SMC we are able to approximate the full joint distribution defined by the PGM. One of the key merits of the SMC sampler is that it provides an unbiased estimate of the partition function of the model. We also show how it can be used within a particle Markov chain Monte Carlo framework in order to construct high-dimensional block-sampling algorithms for general PGMs.

  • 241.
    Andersson Naesseth, Christian
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten. Columbia University, USA.
    Ruiz, Francisco
    Columbia University, USA, University of Cambridge, UK.
    Linderman, Scott
    Columbia University, USA.
    Blei, David
    Columbia University, USA.
    Reparameterization Gradients through Acceptance-Rejection Sampling Algorithms2017Inngår i: Proceedings of the 20th International Conference on Artificial Intelligence and Statistics, 2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Variational inference using the reparameterization trick has enabled large-scale approximate Bayesian inference in complex probabilistic models, leveraging stochastic optimization to sidestep intractable expectations. The reparameterization trick is applicable when we can simulate a random variable by applying a differentiable deterministic function on an auxiliary random variable whose distribution is fixed. For many distributions of interest (such as the gamma or Dirichlet), simulation of random variables relies on acceptance-rejection sampling. The discontinuity introduced by the accept-reject step means that standard reparameterization tricks are not applicable. We propose a new method that lets us leverage reparameterization gradients even when variables are outputs of a acceptance-rejection sampling algorithm. Our approach enables reparameterization on a larger class of variational distributions. In several studies of real and synthetic data, we show that the variance of the estimator of the gradient is significantly lower than other state-of-the-art methods. This leads to faster convergence of stochastic gradient variational inference.

  • 242.
    Andersson, Nisa
    et al.
    Linköpings universitet, Institutionen för datavetenskap.
    Broman, Nils
    Björn, Martin
    Linköpings universitet, Institutionen för datavetenskap.
    Byström, Adrian
    Linköpings universitet, Institutionen för datavetenskap.
    Markfjärd, Gabriel
    Linköpings universitet, Institutionen för datavetenskap.
    Rasmussen, Christian
    Linköpings universitet, Institutionen för datavetenskap.
    Sundberg, Simon
    Linköpings universitet, Institutionen för datavetenskap.
    Prediktion av priset på höstvete2019Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    I denna rapport finnes resultatet av kandidatprojektet i kursen TDDD96 som ges av Linköpings universitet. Projektet har utförts av sju studenter på Civilingenjörsprogrammet inom Datateknik och Civilingenjörsprogrammet inom Mjukvaruteknik. Projektet som utförts var ett mjuvaruutvecklingsprojekt, där studenterna utvecklade en webb-applikation för visningen av historisk data från källor relaterade till lantbruk, med fokus på grödan höstvete. Projektet har dessutom innefattat en studie som, med hjälp av enkla maskininlärningstekniker, undersökt om datan är tillräcklig för att ge en prediktion på vad priset kan tänkas vara i framtiden. Rapporten behandlar de tekniska, gruppadministrativa, och informationsinsamlande val som gjorts, samt hur arbetet med utvecklingen har genomförts och vad resultatet av projektet blev. Rapporten innehåller även sju individuella delar, tillhörande var och en av de sju studenterna, där de genomfört en studie på en egen frågeställning. Dessa finnes i slutet av dokumentet.

  • 243.
    Andersson, Olof
    et al.
    Linköpings universitet, Institutionen för systemteknik, Datorteknik.
    Bengtsson, Karl
    Linköpings universitet, Institutionen för systemteknik, Datorteknik.
    Adapting an FPGA-optimized  microprocessor to the MIPS32 instruction set2010Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Nowadays, FPGAs are large enough to host entire system-on-chip designs, wherein a soft core processor is often an integral part. High performance of the processor is always desirable, so there is an interest in finding faster solutions.This report aims to describe the work and results performed by Karl Bengtson and Olof Andersson at ISY. The task was to continue the development of a soft core microprocessor, originally created by Andreas Ehliar. The first step was to decide a more widely adopted instruction set for the processor. The choice fell upon the MIPS32 instruction set. The main work of the project has been focused on implementing support for MIPS32, allowing the processor to execute MIPS assembly language programs. The development has been done with speed optimization in mind. For every new function, the effects on the maximum frequency has been considered, and solutions not satisfying the speed requirements has been abandoned or revised.The performance has been measured by running a benchmark program—Coremark. Comparison has also been made to the main competitors among soft core processors. The results were positive, and reported a higher Coremark score than the other processors inthe study. The processor described herein still lacks many essential features. Nevertheless, the conclusion is that it may be possible to create a competitive alternative to established soft processors.

  • 244.
    Andersson, Olov
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerade datorsystem. Linköpings universitet, Tekniska fakulteten.
    Methods for Scalable and Safe Robot Learning2017Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Robots are increasingly expected to go beyond controlled environments in laboratories and factories, to enter real-world public spaces and homes. However, robot behavior is still usually engineered for narrowly defined scenarios. To manually encode robot behavior that works within complex real world environments, such as busy work places or cluttered homes, can be a daunting task. In addition, such robots may require a high degree of autonomy to be practical, which imposes stringent requirements on safety and robustness. \setlength{\parindent}{2em}\setlength{\parskip}{0em}The aim of this thesis is to examine methods for automatically learning safe robot behavior, lowering the costs of synthesizing behavior for complex real-world situations. To avoid task-specific assumptions, we approach this from a data-driven machine learning perspective. The strength of machine learning is its generality, given sufficient data it can learn to approximate any task. However, being embodied agents in the real-world, robots pose a number of difficulties for machine learning. These include real-time requirements with limited computational resources, the cost and effort of operating and collecting data with real robots, as well as safety issues for both the robot and human bystanders.While machine learning is general by nature, overcoming the difficulties with real-world robots outlined above remains a challenge. In this thesis we look for a middle ground on robot learning, leveraging the strengths of both data-driven machine learning, as well as engineering techniques from robotics and control. This includes combing data-driven world models with fast techniques for planning motions under safety constraints, using machine learning to generalize such techniques to problems with high uncertainty, as well as using machine learning to find computationally efficient approximations for use on small embedded systems.We demonstrate such behavior synthesis techniques with real robots, solving a class of difficult dynamic collision avoidance problems under uncertainty, such as induced by the presence of humans without prior coordination. Initially using online planning offloaded to a desktop CPU, and ultimately as a deep neural network policy embedded on board a 7 quadcopter.

    Delarbeid
    1. Model-Based Reinforcement Learning in Continuous Environments Using Real-Time Constrained Optimization
    Åpne denne publikasjonen i ny fane eller vindu >>Model-Based Reinforcement Learning in Continuous Environments Using Real-Time Constrained Optimization
    2015 (engelsk)Inngår i: Proceedings of the Twenty-Ninth AAAI Conference on Artificial Intelligence (AAAI) / [ed] Blai Bonet and Sven Koenig, AAAI Press, 2015, s. 2497-2503Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    Reinforcement learning for robot control tasks in continuous environments is a challenging problem due to the dimensionality of the state and action spaces, time and resource costs for learning with a real robot as well as constraints imposed for its safe operation. In this paper we propose a model-based reinforcement learning approach for continuous environments with constraints. The approach combines model-based reinforcement learning with recent advances in approximate optimal control. This results in a bounded-rationality agent that makes decisions in real-time by efficiently solving a sequence of constrained optimization problems on learned sparse Gaussian process models. Such a combination has several advantages. No high-dimensional policy needs to be computed or stored while the learning problem often reduces to a set of lower-dimensional models of the dynamics. In addition, hard constraints can easily be included and objectives can also be changed in real-time to allow for multiple or dynamic tasks. The efficacy of the approach is demonstrated on both an extended cart pole domain and a challenging quadcopter navigation task using real data.

    sted, utgiver, år, opplag, sider
    AAAI Press, 2015
    Emneord
    Reinforcement Learning, Gaussian Processes, Optimization, Robotics
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-113385 (URN)978-1-57735-698-1 (ISBN)
    Konferanse
    Twenty-Ninth AAAI Conference on Artificial Intelligence (AAAI), January 25-30, 2015, Austin, Texas, USA.
    Forskningsfinansiär
    Linnaeus research environment CADICSeLLIIT - The Linköping‐Lund Initiative on IT and Mobile CommunicationsSwedish Foundation for Strategic Research VINNOVAEU, FP7, Seventh Framework Programme
    Tilgjengelig fra: 2015-01-16 Laget: 2015-01-16 Sist oppdatert: 2018-01-11bibliografisk kontrollert
    2. Model-Predictive Control with Stochastic Collision Avoidance using Bayesian Policy Optimization
    Åpne denne publikasjonen i ny fane eller vindu >>Model-Predictive Control with Stochastic Collision Avoidance using Bayesian Policy Optimization
    2016 (engelsk)Inngår i: IEEE International Conference on Robotics and Automation (ICRA), 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, s. 4597-4604Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    Robots are increasingly expected to move out of the controlled environment of research labs and into populated streets and workplaces. Collision avoidance in such cluttered and dynamic environments is of increasing importance as robots gain more autonomy. However, efficient avoidance is fundamentally difficult since computing safe trajectories may require considering both dynamics and uncertainty. While heuristics are often used in practice, we take a holistic stochastic trajectory optimization perspective that merges both collision avoidance and control. We examine dynamic obstacles moving without prior coordination, like pedestrians or vehicles. We find that common stochastic simplifications lead to poor approximations when obstacle behavior is difficult to predict. We instead compute efficient approximations by drawing upon techniques from machine learning. We propose to combine policy search with model-predictive control. This allows us to use recent fast constrained model-predictive control solvers, while gaining the stochastic properties of policy-based methods. We exploit recent advances in Bayesian optimization to efficiently solve the resulting probabilistically-constrained policy optimization problems. Finally, we present a real-time implementation of an obstacle avoiding controller for a quadcopter. We demonstrate the results in simulation as well as with real flight experiments.

    sted, utgiver, år, opplag, sider
    Institute of Electrical and Electronics Engineers (IEEE), 2016
    Serie
    Proceedings of IEEE International Conference on Robotics and Automation, ISSN 1050-4729
    Emneord
    Robot Learning, Collision Avoidance, Robotics, Bayesian Optimization, Model Predictive Control
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-126769 (URN)10.1109/ICRA.2016.7487661 (DOI)000389516203138 ()
    Konferanse
    IEEE International Conference on Robotics and Automation (ICRA), 2016, Stockholm, May 16-21
    Prosjekter
    CADICSELLIITNFFP6CUASSHERPA
    Forskningsfinansiär
    Linnaeus research environment CADICSELLIIT - The Linköping‐Lund Initiative on IT and Mobile CommunicationsEU, FP7, Seventh Framework ProgrammeSwedish Foundation for Strategic Research
    Tilgjengelig fra: 2016-04-04 Laget: 2016-04-04 Sist oppdatert: 2018-01-10bibliografisk kontrollert
    3. Deep Learning Quadcopter Control via Risk-Aware Active Learning
    Åpne denne publikasjonen i ny fane eller vindu >>Deep Learning Quadcopter Control via Risk-Aware Active Learning
    2017 (engelsk)Inngår i: Proceedings of The Thirty-first AAAI Conference on Artificial Intelligence (AAAI) / [ed] Satinder Singh and Shaul Markovitch, AAAI Press, 2017, Vol. 5, s. 3812-3818Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    Modern optimization-based approaches to control increasingly allow automatic generation of complex behavior from only a model and an objective. Recent years has seen growing interest in fast solvers to also allow real-time operation on robots, but the computational cost of such trajectory optimization remains prohibitive for many applications. In this paper we examine a novel deep neural network approximation and validate it on a safe navigation problem with a real nano-quadcopter. As the risk of costly failures is a major concern with real robots, we propose a risk-aware resampling technique. Contrary to prior work this active learning approach is easy to use with existing solvers for trajectory optimization, as well as deep learning. We demonstrate the efficacy of the approach on a difficult collision avoidance problem with non-cooperative moving obstacles. Our findings indicate that the resulting neural network approximations are least 50 times faster than the trajectory optimizer while still satisfying the safety requirements. We demonstrate the potential of the approach by implementing a synthesized deep neural network policy on the nano-quadcopter microcontroller.

    sted, utgiver, år, opplag, sider
    AAAI Press, 2017
    Serie
    Proceedings of the AAAI Conference on Artificial Intelligence, ISSN 2159-5399, E-ISSN 2374-3468 ; 5
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-132800 (URN)978-1-57735-784-1 (ISBN)
    Konferanse
    Thirty-First AAAI Conference on Artificial Intelligence (AAAI), 2017, San Francisco, February 4–9.
    Prosjekter
    ELLIITCADICSNFFP6SYMBICLOUDCUGS
    Forskningsfinansiär
    Linnaeus research environment CADICSELLIIT - The Linköping‐Lund Initiative on IT and Mobile CommunicationsEU, FP7, Seventh Framework ProgrammeCUGS (National Graduate School in Computer Science)Swedish Foundation for Strategic Research
    Tilgjengelig fra: 2016-11-25 Laget: 2016-11-25 Sist oppdatert: 2018-01-13bibliografisk kontrollert
  • 245.
    Andersson, Olov
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerad datorsystem. Linköpings universitet, Tekniska högskolan.
    Heintz, Fredrik
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerad datorsystem. Linköpings universitet, Tekniska högskolan.
    Doherty, Patrick
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerad datorsystem. Linköpings universitet, Tekniska högskolan.
    Model-Based Reinforcement Learning in Continuous Environments Using Real-Time Constrained Optimization2015Inngår i: Proceedings of the Twenty-Ninth AAAI Conference on Artificial Intelligence (AAAI) / [ed] Blai Bonet and Sven Koenig, AAAI Press, 2015, s. 2497-2503Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Reinforcement learning for robot control tasks in continuous environments is a challenging problem due to the dimensionality of the state and action spaces, time and resource costs for learning with a real robot as well as constraints imposed for its safe operation. In this paper we propose a model-based reinforcement learning approach for continuous environments with constraints. The approach combines model-based reinforcement learning with recent advances in approximate optimal control. This results in a bounded-rationality agent that makes decisions in real-time by efficiently solving a sequence of constrained optimization problems on learned sparse Gaussian process models. Such a combination has several advantages. No high-dimensional policy needs to be computed or stored while the learning problem often reduces to a set of lower-dimensional models of the dynamics. In addition, hard constraints can easily be included and objectives can also be changed in real-time to allow for multiple or dynamic tasks. The efficacy of the approach is demonstrated on both an extended cart pole domain and a challenging quadcopter navigation task using real data.

  • 246.
    Andersson, Olov
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerade datorsystem. Linköpings universitet, Tekniska fakulteten.
    Sidén, Per
    Linköpings universitet, Institutionen för datavetenskap, Statistik och maskininlärning. Linköpings universitet, Filosofiska fakulteten.
    Dahlin, Johan
    Kotte Consulting AB.
    Doherty, Patrick
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerade datorsystem. Linköpings universitet, Tekniska fakulteten.
    Villani, Mattias
    Linköpings universitet, Institutionen för datavetenskap, Statistik och maskininlärning. Linköpings universitet, Filosofiska fakulteten. Stockholm University, Stockholm, Sweden.
    Real-Time Robotic Search using Structural Spatial Point Processes2019Konferansepaper (Fagfellevurdert)
  • 247.
    Andersson, Olov
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerade datorsystem. Linköpings universitet, Tekniska fakulteten.
    Wzorek, Mariusz
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerade datorsystem. Linköpings universitet, Tekniska fakulteten.
    Doherty, Patrick
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerade datorsystem. Linköpings universitet, Tekniska fakulteten.
    Deep Learning Quadcopter Control via Risk-Aware Active Learning2017Inngår i: Proceedings of The Thirty-first AAAI Conference on Artificial Intelligence (AAAI) / [ed] Satinder Singh and Shaul Markovitch, AAAI Press, 2017, Vol. 5, s. 3812-3818Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Modern optimization-based approaches to control increasingly allow automatic generation of complex behavior from only a model and an objective. Recent years has seen growing interest in fast solvers to also allow real-time operation on robots, but the computational cost of such trajectory optimization remains prohibitive for many applications. In this paper we examine a novel deep neural network approximation and validate it on a safe navigation problem with a real nano-quadcopter. As the risk of costly failures is a major concern with real robots, we propose a risk-aware resampling technique. Contrary to prior work this active learning approach is easy to use with existing solvers for trajectory optimization, as well as deep learning. We demonstrate the efficacy of the approach on a difficult collision avoidance problem with non-cooperative moving obstacles. Our findings indicate that the resulting neural network approximations are least 50 times faster than the trajectory optimizer while still satisfying the safety requirements. We demonstrate the potential of the approach by implementing a synthesized deep neural network policy on the nano-quadcopter microcontroller.

  • 248.
    Andersson, Olov
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerade datorsystem. Linköpings universitet, Tekniska fakulteten.
    Wzorek, Mariusz
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerade datorsystem. Linköpings universitet, Tekniska fakulteten.
    Rudol, Piotr
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerade datorsystem. Linköpings universitet, Tekniska fakulteten.
    Doherty, Patrick
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerade datorsystem. Linköpings universitet, Tekniska fakulteten.
    Model-Predictive Control with Stochastic Collision Avoidance using Bayesian Policy Optimization2016Inngår i: IEEE International Conference on Robotics and Automation (ICRA), 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, s. 4597-4604Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Robots are increasingly expected to move out of the controlled environment of research labs and into populated streets and workplaces. Collision avoidance in such cluttered and dynamic environments is of increasing importance as robots gain more autonomy. However, efficient avoidance is fundamentally difficult since computing safe trajectories may require considering both dynamics and uncertainty. While heuristics are often used in practice, we take a holistic stochastic trajectory optimization perspective that merges both collision avoidance and control. We examine dynamic obstacles moving without prior coordination, like pedestrians or vehicles. We find that common stochastic simplifications lead to poor approximations when obstacle behavior is difficult to predict. We instead compute efficient approximations by drawing upon techniques from machine learning. We propose to combine policy search with model-predictive control. This allows us to use recent fast constrained model-predictive control solvers, while gaining the stochastic properties of policy-based methods. We exploit recent advances in Bayesian optimization to efficiently solve the resulting probabilistically-constrained policy optimization problems. Finally, we present a real-time implementation of an obstacle avoiding controller for a quadcopter. We demonstrate the results in simulation as well as with real flight experiments.

  • 249.
    Andersson, Patrik
    et al.
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska fakulteten.
    Berntsen, David
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska fakulteten.
    Hultqvist, Tobias
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska fakulteten.
    Post, Jesper
    Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för datavetenskap.
    Schlyter, Fredrik
    Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för datavetenskap.
    Sibelius Parmbäck, Sebastian
    Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för datavetenskap.
    Therén, Oskar
    Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för datavetenskap.
    Iterativ utveckling av en adaptiv bildvisare för mobila plattformar2015Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Detta dokument behandlar ett kandidatarbete gjort av sju datateknikstudenter från Tekniska högskolan vid Linköpings universitet. Arbetet gick ut på att utveckla en webbapplikation för att visa bilder. Målet med webbapplikationen var inledningsvis vagt, den skulle visa bilder, ha någon metod för att ta reda på vilka bilder användaren gillade och sedan basera vilka bilder som skulle visas nästa gång på vilka som hade gillats.

    Dokumentet innehåller också ett kapitel om de erfarenheter och lärdomar gruppen har fått från projektet. Det innehåller även ett appendix med kapitel skrivna av gruppens medlemmar som behandlar olika ämnen relevanta till arbetet.

  • 250.
    Andersson, Patrik
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling.
    Norén, Erik
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling.
    Utvärderingsmetoder för e-tjänster: Användningsbaserad granskning av utvärderingsmetoderna Effektstyrning, DEVIS och Expertutvärdering2011Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Syfte: Denna studie har två huvudsyften, ett praktiskt och ett akademiskt. Det praktiska huvudsyftet är att genomföra en utvärdering av e-tjänsten Nationella Exjobb-poolen (’xjobb.nu’) som drivs av Verket för Högskoleservice (’VHS’). Kopplat till detta har vi haft vårt akademiska huvudsyfte som varit att utvärdera hur väl tre metoder (’Effektstyrning’, ’DEVIS’ och ’Expertutvärdering’) passar för att utvärdera en existerande e-tjänst.

    Frågor: Vi har utgått från tre forskningsfrågor som med grund i vårt syfte är uppdelade i akademiska och praktiska frågor med inriktning på att utvärdera användbarheten hos en e-tjänst och hur användbara de tre metoderna är för utvärdering av e-tjänst.

    Forskningsmetod: Vår studie har varit till största delen kvalitativ med inslag av kvantitativ metod och har haft en induktiv ansats. Arbetet har även varit en fallstudie ur det perspektivet att våra studier av metoderna kan ses som fall. Arbetsordningen har varit sådan att vi sammanställde metoderna för att kunna ställa upp dem så att den efterföljande metodjämförelsen blev möjlig. Efter metodjämförelsen har vi sedan tillämpat metoderna på vårt undersökningsobjekt och analyserat resultatet av detta för att få fram vårt utvärderingsresultat.

    Kunskapsbidrag: Vår studie har ett praktiskt kunskapsbidrag och ett akademiskt kunskapsbidrag. Det praktiska kunskapsbidraget är ett utvärderingsresultat till VHS; att deras sida är funktionell och stödjer de flesta designregler för användbarhet men har ett antal punkter som kan åtgärdas. Det akademiska kunskapsbidraget är i form av ett utvärderingsresultat av de tre metoderna; att metoderna kan användas tillsammans och åtminstone Effektstyrning inte bör användas ensamt vid utvärdering. Vi har även valt att kalla den uppsättning verktyg vi har använt för en metod vid namn S.A.E. – Systematisk Användbarhetsutvärdering av E-tjänst.

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