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  • 1. Batungwanayo, Guillaume
    et al.
    Runnemalm, Anna
    University West, Department of Engineering Science, Division of Automation Systems.
    Ericsson, Mikael
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Weld Joint Tracking System in an Automatic Inspection Cell by Using Emissivity Variation2014In: Proceedings of the 6th International Swedish Production Symposium 2014 / [ed] Stahre, Johan, Johansson, Björn & Björkman, Mats, 2014, p. 1-7Conference paper (Refereed)
    Abstract [en]

    Thermography has proven to be a suitable nondestructive testing method for automatic crack inspection of welds. However automatic weld inspection raises challenges. E.g. the position of the weld might not be exactly as the predefined weld seam, and a weld joint tracking system is needed. To reduce the number of equipment used, a solution is presented in this papers. The infrared camera in the thermography system is a carrier of information of the weld path. This is used for the weld joint tracking system. It is shown that the weld joint tracker is fast enough for an on-line automatic inspection.

  • 2.
    Bolmsjö, Gunnar
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Danielsson, Fredrik
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Svensson, Bo
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Collaborative Robots to Support Flexible Operation in a Manufacturing System2012In: Flexible Automation and Intelligent Manufacturing, FAIM 2012 / [ed] Hasse Nylund, Satu Kantti, Ville Toivonen, Seppo Torvinen, Tampere University, Finland, 2012, p. 531-538Conference paper (Refereed)
    Abstract [en]

    Collaborative robotic systems where human(s) and robot(s) cooperate in performing a common task is an attractive solution to introduce automation combined with high flexibility for tasks that have a high complexity and characterized by low volume or down to one-off. By introducing collaboration in robotics systems, the operator can complement with cognitive capacity and skill in order to gain in flexibility and agility in the task operation. This paper describes on-going work related to work on collaboration between operator and robot. User scenarios are outlined together with methods, software components and hardware to support collaboration, where some of these are under development. As the standards related to collaborative robotic systems are soon to be completed, it is expected that this type of semi-automatic systems will be important for flexible and agile automation of production which otherwise cannot be automated.

  • 3.
    Carlsson, Henrik
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Nilsson, Jim
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Danielsson, Fredrik
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Lennartson, Bengt
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Automated Generation of Discrete Event System Simulation Models for Flexible Automation2011In: The 21st International Conference on Flexible Automation and Intelligent Manufacturing: Taichung, Taiwan, June 26-29 2011, 2011, p. 825-832Conference paper (Refereed)
    Abstract [en]

    Flexible automation cells with rapid product changes are an important competitive advantage for industries today. These cells can increase a company’s productivity and thereby increase their profits. A flexible cell shall be able to handle different products with none or minimal changes to the cell itself. A powerful tool, which can be used to analyse and verify such cells, is discrete event system simulation. Problems such as potential bottlenecks, deadlocks, answers to "what-if" questions and the level of resource utilisation can be gathered. The drawback of discrete event system simulation is that the modelling task is both time consuming and difficult to accomplish. Furthermore, state-of-the-art discrete event system simulation tools that are used in the industry today are not suitable for flexible automation. If the production scenario is changed, e.g. introduction of a new product, the simulation and modelling has to be redone and this is both time consuming and tedious. In this paper a new approach will be presented that enables discrete event simulation models to be generated automatically. The models are generated from information retrieved from a PLM/PDM database system, which is shared among other engineering tools such as robot simulation, CAD and process planning. Hence, when the cell and the database are updated a new model can easily be generated. The database is also connected to the real cell so up-to-date data can be retrieved from the real cell. The model generator described in this paper was implemented and tested in a discrete event system simulation tool and showed promising results. With this approach it is possible to handle flexible automation cells more effectively in a process planning stage.

  • 4.
    Carlsson, Henrik
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Svensson, Bo
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Danielsson, Fredrik
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    A General Virtual Manufacturing Concept for Programming, Verification and Optimisation of Complex Control Functions2008In: Proceedings of the 18th International Conference on Flexible Automation and Intelligent Manufacturing, FAIM 2008: June 30th - July 2nd, 2008, University of Skövde, Sweden / [ed] Leo J. de Vin, Skövde, 2008, p. 668-675Conference paper (Refereed)
    Abstract [en]

    This paper describes a general virtual manufacturing concept for industrial control systems. Our virtual manufacturing concept provides a distinct advantage; programming, verification and optimisation of complex real-time dependent control functions described by real control code, which can be directly transferred to the real manufacturing system. To achieve this distinct advantage, a time synchronised virtual manufacturing system is a necessity. The aim of this paper is thus to present and to describe in detail, our proposed virtual manufacturing concept. To the authors’ knowledge no such general virtual manufacturing concept, i.e. one that can correctly handle complex real-time dependent control functions, currently exists. To summarise previous work related to virtual manufacturing and industrial control systems, several critical issues have been identified. The virtual manufacturing concept proposed in this paper addresses these issues. To verify that our concept can manage these critical issues found and further is suitable in industrial applications a virtual manufacturing test case is also presented. The test case, that includes motion control (i.e. servo), complex control functions, real control systems etc., was carried out with success.

  • 5.
    Carlsson, Henrik
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Svensson, Bo
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Danielsson, Fredrik
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Lennartson, Bengt
    Chalmers University of Technology, Department of Signals and Systems.
    Methods for Reliable Simulation-Based PLC Code Verification2012In: IEEE Transactions on Industrial Informatics, ISSN 1551-3203, E-ISSN 1941-0050, ISSN 1551-3203, Vol. 8, no 2, p. 267-278Article in journal (Refereed)
    Abstract [en]

    Simulation based PLC code verification is a part of virtual commissioning, where the control code is verified against a virtual prototype of an application. With today’s general OPC interface it is easy to connect a PLC to a simulation tool for e.g. verification purposes. However, there are some problems with this approach that can lead to an unreliable verification result. In this paper, four major problems with the OPC interface are described, and two possible solutions to the problems are presented: a general IEC 61131-3 based software solution, and a new OPC standard solution

  • 6.
    Carse, Eddie
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Garsallawi, Naman
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Wennström-Juslin, Christina
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Förslag till övervakningslösning med värmekameror för Magnetgärdets transformatorstation2010Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The substation called Magnetgärdet is located in Ludvika, Sweden and it is owned by Västerbergslagens Energi AB. The substation has recently been renovated and is now placed indoors, which reduces the influence of weather on the station. To decrease the need for personal supervision and increase the availability of the station a monitoring solution is needed.

    The purpose of this degree thesis is to examine if it is possible to monitor the condition of critical items in the station with infrared cameras. To determine this, theory on condition monitoring, thermography and thermal imaging cameras has been compiled together with relevant measurements and tests. The results are then discussed to see if a possible solution can be presented. Important criteria for making condition monitoring with infrared cameras possible have also been formulated in this degree thesis.

    The conclusion is that it is possible, but a complicated system is required. The solution we have given is based on different parts interplaying with each other and it should become a powerful monitoring system. It is however uncertain whether infrared cameras are the only and best tools, therefore other tools should be considered. It might be possible to use thermistors with, or instead of infrared cameras.

  • 7.
    Danielsson, Fredrik
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Svensson, Bo
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    A flexible lean automation concept for robotized manufacturing industry2011In: Proceedings of the 4th International Swedish Production Symposium: 3 - 5, May, Lund, Lund: Swedish Production Academy , 2011, p. 361-367Conference paper (Refereed)
    Abstract [en]

    Due to constant changesin the market there is a need for low-cost and low-volume manufacturing.Usually this type of production is difficult to automate due to the time ittakes to become profitable and the inflexibility of such solutions.  Therefore, flexible automation solutions needto be addressed together with cost effective aspects. In this paper, a newconcept for the design of a flexible, robotized solution based on leanautomation is presented and simulated. The proposed lean automation concept isformed of standardized robot stations, human-robot collaboration and costeffective level of automation. The main goals are flexible automated productionsystem and reduced production cost. This paper shows that the proposed flexiblelean automation concept has some key advantages compared to the traditionalrobot cells; a longer lifetime for the robot cell as well as being easier tore-balance, introduce new parts to and expand the cell. Further, it also showsthat the proposed concept reduces the cost for automation of products with low volume.

  • 8.
    Danielsson, Fredrik
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Svensson, Bo
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Flexible Robotized Automation in Manufacturing Systems2011In: The 21st International Conference on Flexible Automation and Intelligent Manufacturing: Taiwan, 26-29 June 2011, 2011, p. 207-214Conference paper (Refereed)
    Abstract [en]

    Due to constant changes in the market there is a need for low-cost and low-volume manufacturing. Usually this type of production is difficult to automate due to the time it takes to become profitable and the inflexibility of such solutions. Therefore, flexible automation solutions need to be addressed together with cost effective aspects. In this paper, a new concept for the design of a flexible, robotized solution based on lean automation is presented and simulated. The proposed lean automation concept is formed of standardized robot stations, human-robot collaboration and cost effective level of automation. The main goals are flexible automated production system and reduced production cost. This paper shows that the proposed flexible lean automation concept has some key advantages compared to the traditional robot cells; a longer lifetime for the robot cell as well as being easier to re-balance, introduce new parts to and expand the cell. Further, it also shows that the proposed concept reduces the cost for automation of products with low volume.

  • 9.
    Danielsson, Fredrik
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Svensson, Bo
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Gustavsson, Steve
    University West.
    A Flexible Lean Automation Concept for Robotized Manufacturing Industry2010In: MESM 2010: 11th Middle Eastern Simulation Multiconference / [ed] Mar wan Al-Akai di, Ostend: Eurosis , 2010, p. 101-104Conference paper (Refereed)
    Abstract [en]

    This paper describes a general virtual manufacturing concept for industrial control systems. Our virtual manufacturing concept provides a distinct advantage; programming, verification and optimisation of complex real-time dependent control functions described by real control code, which can be directly transferred to the real manufacturing system. To achieve this distinct advantage, a time synchronised virtual manufacturing system is a necessity. The aim of this paper is thus to present and to describe in detail, our proposed virtual manufacturing concept. To the authors’ knowledge no such general virtual manufacturing concept, i.e. one that can correctly handle complex real-time dependent control functions, currently exists. To summarise previous work related to virtual manufacturing and industrial control systems, several critical issues have been identified. The virtual manufacturing concept proposed in this paper addresses these issues. To verify that our concept can manage these critical issues found and further is suitable in industrial applications a virtual manufacturing test case is also presented. The test case, that includes motion control (i.e. servo), complex control functions, real control systems etc., was carried out with success.

  • 10.
    De Backer, Jeroen
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Robotic Friction Stir Welding for Flexible Production2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Friction Stir Welding (FSW) is a modern welding process that joins materials by frictional heat, generated by a rotating tool. Unlike other welding processes, the material never melts, which is beneficial for the weld properties. FSW is already widely adopted in several industries but the applications are limited to simple geometries like straight lines or circular welds, mostly in aluminium. The welding operation is performed by rigid FSW machines, which deliver excellent welds but puts limitations on the system in terms of flexibility and joint geometries. Therefore, several research groups are working on the implementation of the FSW process on industrial robots. A robot allows welding of three-dimensional geometries and increases the flexibility of the whole system. The high process forces required for FSW, in combination with the limited stiffness of the robot brings some extra complexity to the system.  The limitations of the robot system are addressed in this licentiate thesis.

    One part of the thesis studies the effect of robot deflections on the weld quality. A sensor-based solution is presented that measures the path deviation and compensates this deviation by modifying the robot trajectory. The tool deviation is reduced to an acceptable tolerance and root defects in the weld are hereby eliminated. The sensor-based method provided better process understanding, leading to a new strategy that uses existing force-feedback for path compensations of the tool. This method avoids extra sensors and makes the system less complex. Another part of this work focuses on the extra complexity to maintain a stable welding process on more advanced geometries. A model is presented that allows control of the heat input in the process by control of the downforce. Finally, the robot’s limitations in terms of maximal hardness of the materials to be welded are investigated. Parameter tuning and implementation of preheating are proposed to allow robotic FSW of superalloys.

  • 11.
    De Backer, Jeroen
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Process and Product Development.
    Oqueka, Jens
    University West, Department of Engineering Science.
    Bolmsjö, Gunnar
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Investigation of path compensation methods for robotic friction stir welding2012In: Industrial robot, ISSN 0143-991X, E-ISSN 1758-5791, Vol. 39, no 6, p. 601-608Article in journal (Refereed)
    Abstract [en]

    Purpose – Friction stir welding (FSW) is a novel method for joining materials without using consumables and without melting the materials. The purpose of this paper is to present the state of the art in robotic FSW and outline important steps for its implementation in industry and specifically the automotive industry.

    Design/methodology/approach – This study focuses on the robot deflections during FSW, by relating process forces to the deviations from the programmed robot path and to the strength of the obtained joint. A robot adapted for the FSW process has been used in the experimental study. Two sensor-based methods are implemented to determine path deviations during test runs and the resulting welds were examined with respect to tensile strength and path deviation.

    Findings – It can be concluded that deflections must be compensated for in high strengths alloys. Several strategies can be applied including online sensing or compensation of the deflection in the robot program. The welding process was proven to be insensitive for small deviations and the presented path compensation methods are sufficient to obtain a strong and defect-free welding joint.

    Originality/value – This paper demonstrates the effect of FSW process forces on the robot, which is not found in literature. This is expected to contribute to the use of robots for FSW. The experiments were performed in a demonstrator facility which clearly showed the possibility of applying robotic FSW as a flexible industrial manufacturing process.

  • 12.
    De Backer, Jeroen
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Soron, Mikael
    ESAB Welding AB .
    Three-dimensional friction stir welding of Iconel 718 using the ESAB Rosio FSW-robot2012In: Trends in Welding Research: Proceedings of the International Conference on Trends in Welding Research, June 4-8, 2012, Hilton Chicago/Indian Lakes ResortChicago, Illinois, USA / [ed] Tarasankar DebRoy, Stan A. David, John N. DuPont, Toshihiko Koseki, Harry K. Bhadeshia, Ohio: ASM International, 2012, p. 829-833Conference paper (Refereed)
  • 13.
    De Backer, Jeroen
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Soron, Mikael
    ESAB Welding AB .
    Cederqvist, Lars
    Influence of side-tilt angle on process forces and lap joint strength in robotic friction stir welding2012In: Proceedings 9th International friction stir welding symposium, Huntsville, AL, USA, 15th to 17th of May 2012, 2012, p. CD-Conference paper (Refereed)
  • 14.
    De Backer, Jeroen
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Soron, Mikael
    ESAB Welding AB .
    Ilar, Torbjörn
    University West, Department of Engineering Science, Division of Production Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Process and Product Development.
    Friction stir welding with robot for light vehicle design2010In: Proceedings from the 8th International Friction Stir Welding Symposium: Timmendorfer Strand, Germany 18-20 May 2010, The Welding Institute , 2010Conference paper (Other academic)
    Abstract [en]

    Reducing weight is one of the enablers to design more environmentally friendly vehicles. Friction Stir Welding (FSW) supports low weight design through its capability to join different combinations of light weight materials, e.g. different aluminium alloys, but also through its possibilities in producing continuous joints. StiRoLight is a recently started project for robotised FSW for joining of light weight materials emphasising on the vehicle industry, an industry with a long-time experience of robotic welding. The first task involves investigation of force feedback for maintaining the desired contact force. Another important aspect in robotised FSW is the compliance of the robot, which may result in deviations from the pre-programmed path as a result of the high process forces experienced during the welding operation. The further exploration of three-dimensional FSW seams and definition of the process windows will be part of further research within this project.

  • 15.
    Ericsson, Mikael
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Holmblad, Lars
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Almhage, Lisa
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Brochmann, Johanne
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Co-op-modellen – ökad motivation, genomströmning och anställningsbarhet hos studenterna2011In: 3:e UTVECKLINGSKONFERENSEN FÖR SVERIGES INGENJÖRSUTBILDNINGAR 30 NOVEMBER – 1 DECEMBER 2011 PÅ TEKNISKA HÖGSKOLAN VID LINKÖPINGS UNIVERSITET / [ed] Svante Gunnarsson, Linköping: Linköpings Universitet , 2011, p. 90-93Conference paper (Refereed)
    Abstract [sv]

    Den här artikeln beskriver ett mycket framgångsrikt utbildningskoncept som genomförs på Högskolan Väst, främst på ingenjörsutbildningarna maskin och elkraft, som ger en ökad samverkan mellan högskola och omkringliggande samhälle. Konceptet bygger på en amerikansk modell som heter ”Cooperative Education” (Co-op). I Co-oputbildningen varvas teoriperioder med betalda arbetsperioder ute på olika företag och organisationer. Genom en väl planerad integration mellan teoriperioderna och arbetsperioderna förlängs utbildningen i genomsnitt med ca 6 månader men studenten har efter erlagd examen ca 1 års arbetslivserfarenhet. För att sköta kontakterna med de olika företagen finns Co-opkoordinatorer anställda på högskolan. Dessa har till uppgift att sköter den grundläggande kontakten med respektive företag. Studenterna anställs av företagen via ett normalt anställningsförfarande och de har lön enligt företagets kollektivavtal. Företagens organisation och arbetssätt integreras naturligt i utbildningen genom Co-opmodellen då studenten deltar i företagets verksamhet. Detta ger studenten en direkt inblick i arbetslivets villkor och en för Co-opmodellen karaktäristisk självgående förmåga hos studenterna utvecklas.

    Under arbetsperioden besöks studenten och företaget av Co-opkoordinatorn. Under detta besök diskuteras bl.a. arbetsinnehåll, utbildning och framtida kunskapsbehov i företaget. Företagens önskemål fångas upp och integreras på ett bra sätt i utbildningen. Exempel på bra samverkan är gästlärare från företagen. Gästlärare har funnits med sen starten av högskolans ingenjörsutbildningar 1990 och andelen kurser med en eller flera gästföreläsare har ökat genom åren. Den främsta samarbetspartnern på elkraftprogrammet är Vattenfall, men också Preemraff och Trollhättan Energi finns representerade.

    Konkreta resultat av utbildningskonceptet är att studenterna blir mer studiemotiverade vilket ger en ökad genomströmning av godkända studenter på programmen jämfört med studenter som inte följer Co-opmodellen. Ett annat resultat är att Co-opstudenterna har en mycket högre anställningsbarhet jämfört med en vanlig student som har läst samma utbildning.

  • 16.
    Forsmark, Anders
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Sidemark, Tim
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Anslutning av vindkraft till ett svagt nät i Tidaholm2012Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Vindkraftverk ansluts idag i snabb takt till elnät runt om i världen. Elnäten är ofta inte tillräckligt dimensionerade på platser där vindkraftutbyggnad är lämplig vilket leder till ett behov av nätförstärkning. Förstärkning sker konventionellt genom att övergå till en högre spänning, något som kan vara förenat med stora kostnader och ledtider. Bland annat därför har en filosofi med beteckningen smarta elnät uppstått, som handlar om hur elnätsystemet ska se ut när det är mer anpassat till de nya energikällornas karaktär och samtidigt medför ett mer effektivt totalutnyttjande. För vindkraftverk kan det då handla om att i högre grad än idag reglera produktionen och understödja nätet, t.ex. via intelligenta kontrollsystem, kraftelektronik och energilager. I den här rapporten undersöks hur mycket vindkraft som kan anslutas till ett svagt elnät då principer för smarta elnät tillämpas och för att se om kostnaden blir lägre än anslutning via konventionella nätförstärkningsmetoder.

    Det svaga elnätet som studien bygger på ligger i Tidaholm. Vindkraftseffekten som ska anslutas är på 62 MW. Begränsningar i befintliga regionnätets ledningar gör att 60,3 MW kan anslutas med principer för smarta elnät, fast det finns flera skäl till att anta att den fulla mängden vindkraft går att ansluta. Detta till en kostnad som väsentligt understiger kostnaden att förstärka nätet på konventionellt sätt, kostnadsbesparingen uppgår till ca 58 % eller ca 95 Mkr.

  • 17.
    Hagqvist, Petter
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Heralic, Almir
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Technology, Mathematics and Computer Science, Division for Electrical Engineering and Land Surveying.
    Lennartson, Bengt
    University West, Department of Engineering Science, Division of Manufacturing Processes. University West, Department of Engineering Science, Division of Production System. Chalmers.
    Resistance based iterative learning control of additive manufacturing with wire2015In: Mechatronics (Oxford), ISSN 0957-4158, E-ISSN 1873-4006, Vol. 31, p. 116-123Article in journal (Refereed)
    Abstract [en]

    This paper presents successful feed forward control of additive manufacturing of fully dense metallic components. The study is a refinement of former control solutions of the process, providing more robust and industrially acceptable measurement techniques. The system uses a solid state laser that melts metal wire, which in turn is deposited and solidified to build the desired solid feature on a substrate. The process is inherently subjected to disturbances that might hinder consecutive layers to be deposited appropriately. The control action is a modified wire feed rate depending on the surface of the deposited former layer, in this case measured as a resistance. The resistance of the wire stick-out and the weld pool has shown to give an accurate measure of the process stability, and a solution is proposed on how to measure it. By controlling the wire feed rate based on the resistance measure, the next layer surface can be made more even. A second order iterative learning control algorithm is used for determining the wire feed rate, and the solution is implemented and validated in an industrial setting for building a single bead wall in titanium alloy. A comparison is made between a controlled and an uncontrolled situation when a relevant disturbance is introduced throughout all layers. The controller proves to successfully mitigate these disturbances and maintain stable deposition while the uncontrolled deposition fails.

  • 18.
    Hagqvist, Petter
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Heralic, Almir
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Lennartson, Bengt
    Chalmers.
    Resistance measurements for control of laser metal wire deposition2014In: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 54, no March, p. 62-67Article in journal (Refereed)
    Abstract [en]

    A method for controlling robotized laser metal wire deposition online by electrical resistance metering is proposed. The concept of measuring the combined resistance of the wire and the weld pool is introduced and evaluated for automatic control purposes. Droplet formation, detachment of the wire from the weld pool and stubbing can be hard to avoid during processing due to the sensitive process and short reaction times needed for making on-line adjustments. The implemented system shows a possible route for automatic control of the process wherein such problems can be avoided automatically. The method proves to successfully adjust the distance between the tool and the workpiece through controlling the robot height position, thus increasing stability of the laser metal wire deposition process.

  • 19.
    Hagqvist, Petter
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Sikström, Fredrik
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Emissivity estimation for high temperature radiation pyrometry on Ti–6Al–4V2013In: Measurement, ISSN 0263-2241, E-ISSN 1873-412X, Vol. 46, no 2, p. 871-880Article in journal (Refereed)
    Abstract [en]

    The paper demonstrates a versatile procedure suitable for industrial implementation of temperature measurement on a hot titanium alloy. The driving force has been the need for an accurate temperature measurement during additive manufacturing using laser welding technology where Ti–6Al–4V-wire is melted. The challenges consider both industrial constraints and the varying emissivity of the surface. Measurements makes use of a narrow bandwidth spot radiation pyrometer and a calibration procedure for estimation of the surface temperature through spectral emissivity estimation. The theoretical results are validated through experiments. A number of difficulties in radiation temperature measurements for metals with varying surface properties are discussed; especially the case of surface oxidation. The uncertainty in temperature reading due to the uncertainty in the emissivity estimate is established along with a model that qualitatively describes surface oxidation. The procedure is expected to be useful for several manufacturing applications where it is important to control high temperatures.

  • 20.
    Hedlund, Petter
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Studie av alternativ vid konstruktion av testutrustning för generatorskydd2012Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Denna studie utreder alternativ för hur en testutrustning för generatorskydd skulle kunna konstrueras. Den är utförd på uppdrag av Siemens Industrial Turbomachinery, SIT. Målet är att underlätta konfigureringen av generatorskyddet för de konstruktörer som arbetar på SIT samt förebygga fel i provningsfasen som försenar färdigställandet av de turbinanläggningar i vilka generatorskydden skall användas. Testutrustningen behöver vara billig vilket medfört att fokus har legat på att undersöka möjligheten för konstruktion av en egen lösning av signalgenereringen, som är den del av utrustningen som kostar mest.

    Konstruktionen är tänkt att fungera genom användandet av ett styrsystem vars analoga utsignaler förstärks till nivåer passande generatorskyddet. Spänningssignalerna transformeras upp med hjälp av en transformator och strömsignalerna förstärks genom användande av en förstärkarkrets innehållandes transistorer och en operationsförstärkare.

    Kostnaden för konstruktionen är låg jämfört med att köpa in en utrustning motsvarande det reläprovningsinstrument som används i provningsfasen. Det upptäcktes dock att det fanns möjlighet att köpa in ett begagnat reläprovningsinstrument till ett likvärdigt pris. Då detta instrument är av samma fabrikat som det reläprovningsinstrument som används av SIT vid funktionsprovning och dessutom en väl beprövad produkt anses det lämpligare att istället köpa in ett sådant.

  • 21.
    Heralic, Almir
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Monitoring and Control of Robotized Laser Metal-Wire Deposition2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The thesis gives a number of solutions towards full automation of the promising manufacturing technology Robotized Laser Metal-wire Deposition (RLMwD). RLMwD offers great cost and weight saving potentials in the manufacturing industry. By metal deposition is here meant a layered manufacturing technique that builds fully-dense structures by melting metal wire into solidifying beads, which are deposited side by side and layer upon layer. A major challenge for this technique to be industrially implemented is to ensure process stability and repeatability. The deposition process has shown to be extremely sensitive to the wire position and orientation relative to the melt pool and the deposition direction. Careful tuning of the deposition tool and process parameters are therefore important in order to obtain a stable process and defect-free deposits. Due to its recent development, the technique is still manually controlled in industry, and hence the quality of the produced parts relies mainly on the skills of the operator. The scientific challenge is therefore to develop the wire based deposition process to a level where material integrity and good geometrical fit can be guaranteed in an automated and repeatable fashion. This thesis presents the development of a system for on-line monitoring and control of the deposition process. A complete deposition cell consisting of an industrial robot arm, a novel deposition tool, a data acquisition system, and an operator interface has been developed within the scope of this work. A system for visual feedback from the melt pool allows an operator to control the process from outside the welding room. A novel approach for automatic deposition of the process based on Iterative Learning Control is implemented. The controller has been evaluated through deposition experiments, resembling real industrial applications. The results show that the automatic controller increases the stability of the deposition process and also outperforms a manual operator. The results obtained in this work give novel solutions to the important puzzle towards full automation of the RLMwD process, and full exploitation of its potentials.

  • 22.
    Heralic, Almir
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Charles Murgau, Corinne
    University West, Department of Engineering Science, Division of Production Engineering.
    Dzevad, Imamovic
    Volvo Aero Coorporation.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Lennartson, Bengt
    Dep of signal and systems, Chalmers.
    Towards stable high-speed metal-wire deposition, Part I: Parameter studyIn: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387Article in journal (Refereed)
  • 23.
    Heralic, Almir
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Automatic in-process control of laser metal-wire deposition based on sensor feedback2011In: 30th Interantional Congress on Applications of Lasers & Electro-Optics, ICALEO 2011: Orlando October 23-27, 2011. Code 87581|, 2011, p. 211-220Conference paper (Refereed)
    Abstract [en]

    This paper describes alasermetaldepositionsystem that isbasedon robotizedlaserwelding andwirefiller material. The system has been found suitable for the manufacture of simple but large shapes with high metallurgical requirements such as bosses or flanges found on aero engine components. Several benefits have been identified with the usage ofwirefiller compared to powderized feedstock, such as betterprocessefficiency, higherdepositionrates, and cleaner working environment. Thewirebaseddepositionprocessis however sensitive to disturbances and thus requires continuous monitoring and adjustments.Inthis work a 3D scanning system is described forautomaticin-processcontrolof thedeposition. The goal is to obtain a flat surface for each deposited layerinorder to ensure stabledeposition. The deviationsinthe layer height are compensated by controlling thewirefeed rate. The system is tested throughdepositionof small cylindrical bosses and the results show that the proposedcontrolapproach is suitable forautomaticdepositionof such structures. The material consideredinthis paper is Ti-6Al-4V deposited on plates of same material. The paper presents the equipment and thecontrolstrategy and discusses practical issues regarding thesensorused.

  • 24.
    Heralic, Almir
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Production Engineering.
    Ottosson, Mattias
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Lennartson, Bengt
    Chalmers.
    Control Design for Automation of Robotized Laser Metal-Wire Deposition2008In: Proceedings of the 17th IFAC World Congress, International Federation of Automatic Control , 2008, p. 14785-14791Conference paper (Other academic)
    Abstract [en]

    In this paper a novel approach towards automation of robotized laser metal-wire deposition (RLMwD) is described. The RLMwD technique is being developed at University West in cooperation with Swedish industry for solid freeform fabrication of fully dense metal structures. The process utilizes robotized fibre laser welding and metal wire filler material, together with a layered manufacturing method, to create metal structures directly from a CAD drawing. The RLMwD process can also be used for repair or modification of existing components. This paper faces the challenge of designing a control system for maintaining stable process variables, such as a constant layer height and a stable component temperature, during the entire manufacturing process. Several problems are identified and discussed in the paper, e.g. the difficulty of obtaining the bead height in the weld pool environment. The case study is a repair application for stamping tools, where worn out trim edges are to be repaired. Issues regarding the control design, system identification, and the practical implementation of this application are discussed.

  • 25.
    Heralic, Almir
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Lennartson, Bengt
    Dep of signal and systems, Chalmers.
    Height control of laser metal-wire deposition based on iterative learning control and 3D scanning2012In: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 50, no 9, p. 1230-1241Article in journal (Refereed)
    Abstract [en]

    Laser Metal-wire Deposition is an additive manufacturing technique for solid freeform fabrication of fully dense metal structures. The technique is based on robotized laser welding and wire filler material, and the structures are built up layer by layer. The deposition process is, however, sensitive to disturbances and thus requires continuous monitoring and adjustments. In this work a 3D scanning system is developed and integrated with the robot control system for automatic in-process control of the deposition. The goal is to ensure stable deposition, by means of choosing a correct offset of the robot in the vertical direction, and obtaining a flat surface, for each deposited layer. The deviations in the layer height are compensated by controlling the wire feed rate on next deposition layer, based on the 3D scanned data, by means of iterative learning control. The system is tested through deposition of bosses, which is expected to be a typical application for this technique in the manufacture of jet engine components. The results show that iterative learning control including 3D scanning is a suitable method for automatic deposition of such structures. This paper presents the equipment, the control strategy and demonstrates the proposed approach with practical experiments.

  • 26.
    Heralic, Almir
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Lennartson, Bengt
    Dep of signal and systems, Chalmers.
    Towards stable high-speed metal-wire deposition, Part II: Automatic deposition using feedback controlArticle in journal (Refereed)
  • 27.
    Heralic, Almir
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Ottosson, Mattias
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Lennartson, Bengt
    Chalmers Tekniska Högskola.
    Increased stability in laser metal wire deposition through feedback from optical measurements2010In: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 48, no 4, p. 478-485Article in journal (Refereed)
    Abstract [en]

    Robotized laser metal-wire deposition is a fairly new technique being developed at University West in cooperation with Swedish industry for solid freeform fabrication of fully densed metal structures. It is developed around a standard welding cell and uses robotized fiber laser welding and wire filler material together with a layered manufacturing method to create metal structures. In this work a monitoring system, comprising two cameras and a projected laser line, is developed for on-line control of the deposition process. The controller is a combination of a PI-controller for the bead width and a feed-forward compensator for the bead height. It is evaluated through deposition of single-bead walls, and the results show that the process stability is improved when the proposed controller is used.

  • 28.
    Heralic, Almir
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Ottosson, Mattias
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Lennartson, Bengt
    Dep of signal and systems, Chalmers.
    Automation of laser metal deposition for the manufacture of fully dense structures2011In: 4th International Swedish Production Symposium, SPS11: 3-4 May, Lund, Sverige / [ed] Jan-Eric Ståhl, Swedish Productio Academy , 2011, p. 219-227Conference paper (Refereed)
  • 29.
    Heralic, Almir
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Ottosson, Mattias
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Norlander, Torbjörn
    Volvo Aero Coorporation.
    Geometry control of laser metal deposition for the manufacture of complex structures in the aero industry2011In: 20th International Society for Airbreathing Engines Conference, ISABE 2011: September 12-16, 2011 Gothenburg, 2011, p. 1666-1674Conference paper (Refereed)
  • 30.
    Heralic, Almir
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Ottosson, Mattias
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Production Engineering.
    Kristiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Visual feed-back for operator interaction in robotized laser metal deposition2008In: Proceedings of the 22nd International Conference on Surface Modification Technologies SMT22: Held at University West, Trollhättan, Sweden September 22-24, 2008 / [ed] T.S. Sudarshan & Per Nylen, 2008, p. 297-304Conference paper (Other academic)
  • 31.
    Ivarsson, Johanna
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Improvement of Commutation Failure Prediction in HVDC Classic Links2011Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In this thesis, an evaluation of the existing control system for ABB: s HVDC Classic Links is performed in order to investigate whether a possible improvement to commutation failure prediction is possible and to be recommended.

    The thesis starts with a theoretical approach to the complexity of consequences of increasing the extinction angle (γ) in order to prevent commutation failure in inverter operation, which is later confirmed through using the simulation software PSCAD to evaluate coherence between simulation results and theory.

    Dynamic power studies are performed through simulations in the electromagnetic time domain transient tool PSCAD in order to establish a possible improvement to the existing commutation failure prediction today used in ABB control systems for HVDC applications.

  • 32.
    Karlsson, Lars
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Fallstudie i Järbo: En utredning av förutsättningarna för återstart av ett nedlagt småskaligt vattenkraftverk2009Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The prospects of achieving a restart of the two small hydropower plants studied in this report are good. The basic conditions are favourable in the sense that the plans for a restart are well in line with accepted procedures such as established by decisions in the highest courts regarding similar cases. The owner plans to run the operation in essentially the same way it was originally run, a circumstance which has proven to be important when seeking to get restart of discontinued hydropower activities approved. These power plants are small, very small. This means that investment costs has to be minimized if there is to be any chance of achieving an acceptable pay-off time for the investment. Some can't be affected at all, such as the cost for getting connected to the power network. Some, such as those of new tubes, intake bars and electrical wiring and equipment for the plants, can be affected to some extent by carefully choosing the suppliers of the equipment and choosing the most cost-efficient (in most cases synonymous with the simplest but yet functional) solutions. A few components, such as the generator, can possibly be obtained as used equipment, which helps keeping the costs down. Lastly, the potential of saving money by doing as much as possible of the work yourself should not be underestimated.

  • 33.
    Keyvani, Ali
    et al.
    University West, Department of Engineering Science, Division of Production Engineering. University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Danielsson, Fredrik
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    A Virtual Manufacturing Approach for Integrating Fixture Design with Process Planning2009In: Proceedings of the sixth CIRP-sponsored International Conference on Digital Enterprise Technology: 14-16 dec, HongKong, 2009, p. 483-496Conference paper (Other academic)
    Abstract [en]

    Computer Aided Process Planning has received more attention recently due to considerable progress in the aspects of both technology and theory. Beside the traditional trends and efforts to integrate the product design and process planning activities usually referred to as concurrent engineering, virtual manufacturing tools have opened new horizons to this domain. This paper describes how to combine an existing modular fixture design with process planning and simulation tools. The proposed concurrent architecture consists of a functional model and an operational workflow for the design of modular fixtures within the process-planning phase. Two different paradigms, the Variant and the Generative, are discussed in relation to the proposed architecture. Fixtures for Body in White lines are a crucial design problem in the automotive industry. Therefore, the proposed architecture has been tested and investigated in such an environment.

  • 34.
    Larsson, Hans
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Fjärrfrånskiljares inverkan på kundavbrottstiden i Vattenfall Eldistributions lokalnät2009Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    An alternative approach in Vattenfall Eldistribution’s network has evolved from the increased demands on reducing network downtime. Eldistribution are using remote controlled disconnectors / reclosers in Finland to reduce the system average interruption duration index (SAIDI). The initial section of the report includes a study on the source of downtime and SAIDI-statistics in Eldistribution’s network. A comparison with network and the climate in Finland is carried out which indicate different conditions in the two countries. The weather comparison shows that it’s more difficult to use non-insulated overhead-lines in Sweden because of the climate conditions. The result shows a maximum reduction of SAIDI by 36% and a minimum of 17% based on calculations on six example-lines. If all the lines would be possible to build under similar principles it would result in a reduction of Eldistributions SAIDI by approximately 12 % if the 200 worst lines was supplemented with remote controlled disconnectors with a corresponding amount of reduced SAIDI-minutes. Comparisons with cable alternatives show that it’s more cost-effective to invest in remoted controlled disconnectors if the target is a quick and cheap reduction of SAIDI. As a general recommendation the backup powering of a network should be remote controlled and the lines should have at least one outsourced remote controlled disconnector. This will split the line in multiple remote controlled areas, which will reduce disruption time for customers connected to the line. If a line doesn’t have any backup powering it should be investigated whether it’s possible to connect the line to another line to ensure backup-feeding if this is possible to do at acceptable costs. If there are more locations on the line suitable for supplementation of remote controlled disconnectors, those places should be used to get as much reduced SAIDI as possible at a cost-effective level. It's difficult to give a general advice concerning the number of remote controlled disconnectors but the first disconnector is generally more cost-effective than the subsequent ones. Reclosers should be deployed at appropriate locations to be equally costefficient as remoted controlled disconnectors. Examples of such places can be when switching from cable to non-insulated line and before a section where errors often occur.

  • 35.
    Lennartson, Bengt
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Sikström, Fredrik
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Sampled-data Hcontrol applied to the choice of controller order and sampling rate2010Manuscript (preprint) (Other academic)
  • 36.
    Lennartsson, Aron
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Byte av styrsystem i mellantork B2011Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Saab Automobile AB är ett företag som tillverkar bilar i familjesegmentet och har sin fabrik belägen i Trollhättan. Deras underhållsavdelning i måleriet har ett behov av att byta ut sin Sattscope H terminal som styr mellantork täckfärg B. Anledningen är att terminalens display tappar pixlar och att nya terminaler inte längre finns som reservdel. Mellantork täckfärg B fungerar inte utan terminalen. Saab ser därför att terminalen byts ut mot en dator med Ledpanel designer installerad, som skall fungera som operatörspanel. Nya menyer skall också programmeras. Detta för att underlätta vid byte av karosstyp eller färggrupp då nuvarande system måste programmeras i Dox10 av underhållspersonal, vilket är omständigt. Med dessa två extramenyer och Ledpanel installerat är syftet att operatören själv skall kunna ändra karosstyp och färggrupp och på så sätt effektivisera ställtiden samtidigt som det avlastar för underhållsavdelningen.

    Innan produktionen kan startas med den nya programvaran måste ett antal funktionstester noga utföras. Dessa tester utför Saabs underhållspersonal frekvent när ett nytt program skall tillämpas. Testerna utförs för att säkerställa programmets funktion och för att kunna utesluta vissa fel när produktionen väl är igång. Om ett fel ändå skulle inträffa kan produktionen behöva stå stilla medan felet åtgärdas och på så sätt kan ett enkelt fel då bli mycket kostamt för företaget. Följande verifieringsförsök har gjorts innan drifttagande för det nya programmet 182920 togs i bruk: medveten spänningsdipp, uppstart, test av funktioner och en simulering. En backup av hela systemet har även gjorts för snabb återlagring.

    För att få en inblick i hur mellantork B:s PLC-system fungerar har dess funktioner och arbetssätt beskrivits. En handhavandebeskrivning har även gjorts för operatörspanelen så att en operatör utan utbildning lätt skall förstå och kunna navigera sig i programmet. 

  • 37.
    Mård, Mathias
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Automation i Distributionsnät2012Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    As a part of Göteborg Energi’s work towards a smarter electric grid, the company has chosen to investigate the possibilities of automation in their middle voltage grid. In Europe, there are example cases where these technologies already are installed which many articles on the CIRED conference 2011 proved. Netcontrol Oy in Finland has, together with Tekla, created an automated SCADA system that Vattenfall in Finland today uses. The grid mainly consists of 10 kV open loop fed city grid and this automation is mainly designed for this type of grid. The intention of the automation is to when a fault occurs, the automation disconnects the faulted cable in the loop and then reconnects, this in as little time as possible in order to not make customers suffer.There are several different theories about how automation can be implemented, the two main principles are local automation and centralized automation. The local automation is implemented at station level with fault detectors that communicate with each other and thus disconnects a fault in the circuit using logic steps. This is the fastest option and Göteborg Energi has already installed several devices in the grid, which could make this option possible to realize. The other alternative is to let the SCADA do the sectionalizing using information from the indicators in the loop. This poses a problem though when the system becomes more complex. The operational staff might have problems with letting the SCADA make its own decisions and thereby lose control over the events in the grid. What the system could do instead is to make a suggestion on how the operational staff should handle the situation. However, the fault durations in this case will end at its best around 2-5 minutes and this makes the customer suffer for a longer time than the earlier principle.Hence, local automation is recommended, partly because it is today implemented in the grid and also because the fault duration is much shorter. This option can, with today’s technology disconnect a single-phase to ground fault without a power failure, and thus does no customer suffer during the fault. This should be supplemented with some sort of residual current compensation of the earth fault in order to remove the active fault current, thus minimizing the probability of a double earth fault or short circuit. Göteborg Energi should contact the suppliers of these devices and find out what they consider appropriate, and implement the technology in a loop as a pilot project to investigate its function.

  • 38.
    Nia, Nima K.
    et al.
    Volvo Cars, VCIT, Olofström, Sweden.
    Danielsson, Fredrik
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Lennartson, Bengt
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    A faster collision detection method applied on a sheet metal press line2011In: The 21st International Conference on Flexible Automation and Intelligent Manufacturing: Taiwan, 26-29 June 2011, 2011, p. 833-840Conference paper (Refereed)
    Abstract [en]

    Geometrical collision detection is a time and resource consuming simulation task. In order to decrease time and resources, a general method has been developed. The method is useful in simulation cases where 3D CAD data is part of an iterative method, e.g. optimization. The method is based on a transformation of a general 3D problem to a 2D problem, eliminating the need of 3D CAD models. Press Line simulations during the last decade have been accepted as a quality improvement method. Today simulations of automated press lines are done for internal collision checks in dies and external collision checks against dies and material handling equipment. If these collisions are not detected in simulations, they result in delays, in introduction of a new product in the line, so called line tryout or later on when the line is ramped up to decided rate. The results of these collisions are used for pre-die design, design of grippers, maintenance and production planning. In this paper a new method, based on 2D simplifications, is developed and tested successfully in a virtual model of a press line at Volvo Car Manufacturing. Die Uppers 2 917 708 triangles and Die Lowers 602 686 triangles where reduced to 58 and 90 points. The result of the method shows substantial reduction of geometry data and a considerable improvement in collision detection evaluation time over general 3D algorithms in the tested case.

  • 39.
    Nia, Nima K.
    et al.
    Volvo Cars, VCIT, Olofström, Sweden.
    Danielsson, Fredrik
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Lennartson, Bengt
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    A faster collision detection method applied on a sheet metal press line2011In: The 4th International Swedish Production Symposium, Lund: Swedish Production Academy , 2011, p. 467-472Conference paper (Refereed)
    Abstract [en]

    Geometrical collision detection is a time and resource consuming simulation task. In order to decrease time and resources, a general method applicable for 2D motions has been developed. The method is useful in simulation cases where 3D CAD data is part of an iterative method, e.g. optimization. The method is based on a transformation of a general 3D problem to a 2D problem, eliminating the need of 3D CAD models. Press Line simulations during the last decade have been accepted as a quality improvement method. Today simulations of automated press lines are done for internal collision checks in dies and external collision checks against dies and material handling equipment. If these collisions are not detected in simulations, they result in delays, in introduction of a new product in the line, so called line tryout or later when the line is ramped up to decide rate. The results of these collisions are used for pre-die design, design of grippers, maintenance and production planning. In this paper a new method, based on 2D simplifications, is developed and tested successfully in a virtual model of a press line at Volvo Car Manufacturing. Die Uppers 2 917 708 triangles and Die Lowers 602 686 triangles where reduced to 58 and 90 points. The result of the method shows substantial reduction of geometry data and considerable improvement in collision detection evaluation time over general 3D algorithms in the tested case.

  • 40.
    Nia, Nima K.
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Danielsson, Fredrik
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Lennartson, Bengt
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Efficient geometrical simulation and virtual commissioning performed in stamping2012In: Proceedings of 2012 IEEE 17th International Conference on Emerging Technologies & Factory Automation (ETFA 2012), Polen: IEEE, 2012, p. 1-8Conference paper (Refereed)
    Abstract [en]

    In order to  perform efficient geometrical simulation and virtual commissioning in stamping, three fields are investigated namely: simulation building time, collision detection time and optimization time. Hence, reducing time is the main theme of this paper. To reduce simulation building time and optimization time, an efficient stamping simulation model is built and tested. Collision detection time is examined by a relative motion method based on 3D to 2D geometrical collision detection. The presented results mean that simulation and virtual commissioning can be performed at least ten times faster compared to standard approaches.

  • 41.
    Nilsson, Daniel
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Berg, Sebastian
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Standardisering och modularisering av lågspänningsställverken i ABB:s HVDC-stationer.2010Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis investigates the possibilities to standardize and modularize the low-voltageswitchgear in ABB’s HVDC-stations. The reason for this is that the customized solutionthey use today take too much engineering and production time to meet the expectedincrease of projects.The report is based on thirteen stations in eight different closed or ongoing projects. Theselection was based on the station size, geographical location, commissioning year andstation type.In order to obtain a correct representation of the loads in the low-voltage switchgear, therelevant station documentation was reviewed and compiled in a database. The data wasthen analyzed to determine the most frequently occurring loads and their characteristics.The thesis shows that it’s possible to standardize some components in the low-voltageswitchgear. However, this report doesn’t take into consideration any possible increase oftotal size and cost. It also shows the most frequent sizes of the circuit breakers for each ofthe common loads.The standard proposition for the common loads was developed to cover all the occurringsizes of the circuit breakers in the stations. For the converter transformers coolingequipment there’s two different cubicles to choose from, while the remaining loads islimited to a single alternative.An alternative solution could be to develop a standard for each occurring station type.However, this would require that the data from a larger number of projects, for all stationtypes, are reviewed and compiled.

  • 42.
    Nilsson, Rikard
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Rekommendationer inför konstruktion av mellanspänningsställverk: ett underhållsperspektiv2009Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    OKG AB is the owner of the three boiling water reactors Oskarshamn 1, 2 and 3. The nuclear power plant is located in Simpevarp north of Oskarshamn. The thesis has been carried out at Oskarshamn 1 within a project called CEM. Oskarshamn 1 started to produce electricity in 1972 and can today deliver an electrical power of 491 MW.

    The thesis considers maintenance aspects which are to be taken into consideration before planning and construction of the new automatic gas turbine secured switchgears in system 642. The switchgears are the main distribution switchgears within Oskarshamn 1 and are to be replaced because of high age and lack of spare parts.

    In purpose to achieve high availability performance and availability for the switchgears, aspects which improves the reliability, maintainability and maintenance supportability has been specified. Suggestion of new distribution of the loads between the busbars and arrangement of the cubicles has also been carried out and specified.

    The results of the thesis are the specified maintenance aspects which can be used when planning and constructing the switchgears. The most important maintenance aspects are that the equipment has high personnel safety, that there is enough space in the cubicles to perform maintenance and that a complete documentation is delivered together with the equipment. Suggestion of new load distribution between the busbars has been carried out with the help of a technical specification. The suggestion of new arrangement for the switchgears implies that there is enough space in the existing electrical room for the switchgears.

  • 43.
    Olsson, Christian
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    The automatic manufacturing processes: the technique of controlling a mobile robot2010Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In today's industry it is of mayor concern to keep the manufacturing processes as effective and flexible as possible. The usage of robots and automatic technology is a much known way to achieve the goals of rationalization. The disadvantage lays in the fact that implementation of robots is usually a very resource consuming task. However, in some circumstances a solution to this matter may be to simply implement mobile robots instead of fixed robots.

    The task of this project is to successfully control and understand the system of a mobile robot in a automatic manufacturing process.

  • 44.
    Ryberg, Anders
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Camera Modelling and Calibration with Machine Vision Applications2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Camera modelling and calibration are important parts of machine vision. They can be used for calculating geometric information from images. A camera model is a mathematical projection between a 3D object space and a 2D image. The camera calibration is a mathematical procedure calculating parameters of the camera model, usually based on several images of reference points. These fundamental parts of machine vision are improved in this thesis. One large part is the development of a generic camera model, GCM, that is accurate, computationally efficient and can be used for both conventional, fisheye and even catadioptric cameras. Different models were used in the past for conventional and  omnidirectional cameras and this is a well-known problem, the solution of which is described in this thesis. The accuracy of camera models is improved by introducing new ways of compensating for different distortions, such as radial istortion, varying entrance pupil point and decentring distortion. Calibration is mproved by introducing newmeans of calculating start estimates of camera parameters, from analysing shapes, sizes and positions of the reference points in the images. These start estimates are needed in order to make the calibration converge. Methods for calculating better reference centre points than the centres of gravity are developed in order to increase the accuracy further. Non-trivial null spaces that occur during calibration are identified. Awareness of these improve the calibration. Calibrations with different camera models are implemented and tested for real cameras in order to compare their accuracy. Certain models are better for certain situations, but the overall performance and properties are favourable for the GCM. A stereo vision welding robot system is developed, using the new model. It determines the geometry of a 3D weld joint, so that a robot can follow it. The same system is implemented in a virtual environment using a simulation software. Such simulation is important since it makes it possible to develop robot vision systems off-line.

  • 45.
    Sikström, Fredrik
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Modeling and simulation for welding automation2010Doctoral thesis, comprehensive summary (Other academic)
  • 46.
    Sikström, Fredrik
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Simulation-based feedback control of welding processes2008Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Fusion welding for joining of metals is an important manufacturing process widely used in industry, and very appreciated for its usefulness. This thesis presents a strategy dealing with the problem of designing feedback control for robotised welding. The idea is to use off-line programming where computer aided robotics for weld sequences is integrated with finite element modelling for simulations and analyses of weld processes. By this approach the design, evaluations, trials and visualisation can be made “off-line”, beside or prior to continuous production. The focus is to reduce the amount of manpower and need for physical experiments. Focuses on the results are to ensure a high quality weld with limited residual stress and deformation. Different models for two types of austenitic steels and two types of weld sources has been calibrated and validated to form a basis for this strategy. Suggestions for systematic model calibration methods have been proposed including global and local optimisation methods. Experimental work has been performed to support and verify the simulation results and the usefulness of the method. The simulation based strategy has been evaluated and proven to work successfully in two different types of applications. The method is not independent of physical experiments since it is based on models that have to be calibrated, but the experiments needed are assumed to be carried out in a simple and cost efficient way. The thesis suggests how these experiments can be performed. The use of all these technologies is assumed to form an efficient tool for the welding engineer in order to obtain high weld quality in robotised welding. The research presented indicates that the methods work well in real situations and that further work for more robust industrialisation will be beneficial for the welding community.

  • 47.
    Sikström, Fredrik
    et al.
    University West, Department of Engineering Science, Division of Process and Product Development. University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Lennartson, Bengt
    University West, Department of Engineering Science, Division of Process and Product Development.
    Model order reduction methods applied to a welding model2012In: Proceedings of the Institution of mechanical engineers. Part I, journal of systems and control engineering, ISSN 0959-6518, E-ISSN 2041-3041, Vol. 226, no 7, p. 972-984Article in journal (Refereed)
    Abstract [en]

    A  finite element representation modelling transient heat conduction of gas tungsten arc welding of stainless steel is used to evaluate different methods for model order reduction. The focus is on establishing a linear low-order model of the dynamic  relation between the welding current and the temperature measured by a radiation pyrometer. The objective of this low-order model is to design a model-based feedback controller and to investigate the consequences of applying feedback control of the process. Three different approaches for model reduction have been evaluated, namely the Krylov subspace method for moment    matching, balanced truncation and parametric system identification. The study provides a knowledge base for the selection of model order reduction methods when dealing with large-scale systems like finite element models of transient heat conduction, and it recommends parametric system identification. It renders sufficient approximations for controller design, no linearization of the finite element model is required, and there is no limit on degrees of freedom of the finite element model.

  • 48.
    Sikström, Fredrik
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Lennartson, Bengt
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Modeling and simulation aspects of feedback control in gas tungsten arc welding: An experimental study2010Manuscript (preprint) (Other academic)
  • 49.
    Sikström, Fredrik
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Lennartson, Bengt
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Role of fixture forces on distortion in gas tungsten arc welding: An experimental and modelling approach2011In: Proceedings of the Institution of mechanical engineers. Part B, journal of engineering manufacture, ISSN 0954-4054, E-ISSN 2041-2975, Vol. 225, no 1, p. 140-148Article in journal (Refereed)
    Abstract [en]

    Simulation and experiments show that the fixture clamping force has a significant influence on the structural integrity of a welded workpiece. This understanding is of great importance for the manufacture of aerospace components with tight tolerances in the specifications. The focus in the present study is on the temperature history during welding and residual deformation; its main contribution is a demonstrator designed for evaluation of the influence of fixture clamping forces and validation of the simulation results. The demonstrator concerns a simplified situation considering gas tungsten arc welding of a nickel-based metal plate fixed by a specially designed fixture, where one side of the plate was clamped with different levels of force. The temperature history was measured during the weld sequence and deformation measurements were performed after cooling and release of the workpiece from the fixture. The results from simulation and experimentation showed good agreement. The proposed strategy is industrially competitive and has shown that the looser the fixture clamps, the smaller the residual deformation. Furthermore, the study provides a knowledge base for selection of active fixture concepts in that the fixture clamping force can be determined in advance and possibly also be subject to force control.

  • 50.
    Sikström, Fredrik
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Ericsson, Mikael
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Integration of finite element analysis and computer aided robotics for advanced programming of robotized welding2009In: ASM Proceedings of the International Conference: Trends in Welding Research / [ed] S.A. David, T. DebRoy, J.N. DuPont, T. Koseki, and H.B. Smartt, ASM International, 2009, p. 454-460Conference paper (Refereed)
    Abstract [en]

    This paper describes a promising approach where finite element analysis is combined with computer aided robotics in off-line programming of advanced robotized welding. Finite element analysis is used to find an optimized weld power signal based on weld trajectories obtained from computer aided robotic simulations. The weld power signal is calculated by applying feedback control in the finite element simulation. This optimization ensures a full penetration weld while the total specific thermal energy input is minimized in order to mitigate unwanted residual stress and distortion. The objective with this approach is to support the design of robotized welding and significantly reduce the number of costly trials in physical implementations. The relevance of this paper is a useful method for off-line optimization of robot trajectories and varying process parameters.

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