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  • 1.
    Amouzgar, Kaveh
    et al.
    University of Skovde, Jonkoping University.
    Strömberg, Niclas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Jonkoping University, Orebro Univ, University University West - Sweden.
    An approach towards generating surrogate models by using RBFN with a priori bias2014Ingår i: PROCEEDINGS OF THE ASME INTERNATIONAL DESIGN ENGINEERING TECHNICAL CONFERENCES AND COMPUTERS AND INFORMATION IN ENGINEERING CONFERENCE, 2014, VOL 2B, AMER SOC MECHANICAL ENGINEERS , 2014, Vol. 2BKonferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, an approach to generate surrogate models constructed by radial basis function networks (RBFN) with a priori bias is presented. RBFN as a weighted combination of radial basis functions only, might become singular and no interpolation is found. The standard approach to avoid this is to add a polynomial bias, where the bias is defined by imposing orthogonality conditions between the weights of the radial basis functions and the polynomial basis functions. Here, in the proposed a priori approach, the regression coefficients of the polynomial bias are simply calculated by using the normal equation without any need of the extra orthogonality prerequisite. In addition to the simplicity of this approach, the method has also proven to predict the actual functions more accurately compared to the RBFN with a posteriori bias. Several test functions, including Rosenbrock, Branin-Hoo, Goldstein-Price functions and two mathematical functions (one large scale), are used to evaluate the performance of the proposed method by conducting a comparison study and error analysis between the RBFN with a priori and a posteriori known biases. Furthermore, the aforementioned approaches are applied to an engineering design problem, that is modeling of the material properties of a three phase spherical graphite iron (SGI). The corresponding surrogate models are presented and compared.

  • 2.
    Bennulf, Mattias
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Danielsson, Fredrik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Svensson, Bo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Identification of resources and parts in a Plug and Produce system using OPC UA2019Ingår i: Procedia Manufacturing, E-ISSN 2351-9789, Vol. 38, s. 858-865Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper describes a method together with an implementation for automating the detection, identification and configuration of newly added resources and parts in a Plug and Produce system using OPC UA. In a Plug and Produce system, resources and parts are usually controlled by agents, forming a multi-agent system of collaborating resources. Hence, when a resource or part is connected to the system, a corresponding agent must be instantiated and associated with that specific device. In order to automate this, the system needs information about newly connected devices. This information could, for example, be positional data describing where the device is connected. Some devices like tools and parts to be processed have no own network connection, but still, they should get an agent with correct configuration instantiated. In this work, OPC UA is used for communication between devices and the corresponding agents. All agents and their communication are handled by an Agent Handling System, consisting of an OPC UA HUB together with functions for device detection and agent instantiation. The HUB is used for transferring data between devices and their agents in the network by OPC UA protocols. When a device is connected to the network, it is detected, and a connection is automatically created to the HUB that becomes configured for transmitting data between the device and its corresponding agent. © 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

  • 3.
    Carlsson, Henric
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för automation och datateknik.
    Danielsson, Fredrik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Lennartson, Bengt
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    General Time Synchronisation Method for PLC Programs Aiming at Virtual Verification and Development2008Ingår i: 17th IFAC World: Congress Proceedings of the 17th World Congress. The International Federation of Automatic Control. Soel, July 6-11, 2008, s. 4440-4445Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The latest state-of-the-art Computer Aided Production Engineering (CAPE) simulation technology offers OPC integration for PLC verification. A critical drawback with this technology has been identified and described within this paper. A new time synchronisation method and a simulation architecture are therefore presented and proposed. The time synchronisation method together with the architecture can be used when verifying and developing real-time dependent control logic for industrial control system, e.g. PLC with CAPE tools. The method described in this paper is general and should work on any PLCs that are compatible with the IEC 61131-3 standard. A test case was also carried out, showing that by disregarding time synchronisation it is impossible to verify real-time dependent PLC functions together with CAPE tools in a reliable way. However, the test case also shows that by applying the proposed time synchronisation method together with the described simulation architecture a successful industrial verification method is achieved

  • 4.
    Carlsson, Henrik
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Svensson, Bo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Danielsson, Fredrik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    A General Virtual Manufacturing Concept for Programming, Verification and Optimisation of Complex Control Functions2008Ingår i: 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, s. 668-675Konferensbidrag (Refereegranskat)
    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.
    Christiansson, Anna-Karin
    Högskolan Väst, Institutionen för teknik (HTU).
    A unified framework for mixed continuous/discrete-time H_infinity -control2003Doktorsavhandling, monografi (Övrigt vetenskapligt)
  • 6.
    Christiansson, Anna-Karin
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Danielsson, Fredrik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Heralic, Almir
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Ottosson, Mattias
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Hurtig, Kjell
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Automation of a robotised metal deposition system using laser melting of wire2008Ingår i: 18th International Conference on Flexible Automation and Intelligent Manufacturing (FAIM 2008): Skövde, 30 June-2 July, 2008, s. 122-129Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    This paper presents a system for full automation of free-form-fabrication of fully dense metal structures using robotized laser melting of wire. The structure is built of beads of melted wire laid side by side and layer upon layer governed by synchronized robot motion. By full automation is here meant that the process starts with a product specification of a component, and ends in a geometrically validated dense metal component fulfilling industrial material requirements. Due to the complexity of this flexible manufacturing system, a number of different disciplines are involved. This paper discusses mainly the system design, which includes how off-line programming is used for automatic generation of code and how feedback control is used for on-line adjustment of parameters based on desired building properties. To meet industrial needs, the project is carried out in a close cooperation between research and development activities in academy and industry.

  • 7.
    Christiansson, Anna-Karin
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för automation och datateknik.
    Lennartson, B.
    Chalmers University of Technology, Control Engineering Lab, Göteborg, Sweden .
    Toivonen, H.
    Åbo Akademi University, Department of Chemical Engineering, Åbo, Finland.
    Mixed continuous/discrete-time output feedback H∞ control: A unified approach1999Ingår i: European Control Conference, ECC 1999 - Conference Proceedings, 1999, s. 4077-4082Konferensbidrag (Refereegranskat)
    Abstract [en]

    A Riccati equation (RE) based solution to the H∞ optimal control problem for mixed continuous/discrete-time systems is presented. The results unify a number of recently penetrated H∞ control problems. In the infinite-horizon case a periodic behaviour is assumed, and it is shown how the related continuous RE with jumps can be replaced by an equivalent discrete periodic RE. A related algebraic RE, which involves the system behaviour during one period, then can be formulated and solved by standard methods. Typical applications are control of continuous-time or discrete-time periodic systems, as well as multirate and sampled-data control, including mixed continuous and sampled-data measurements. © 1999 EUCA.

  • 8.
    Christiansson, Anna-Karin
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för automation och datateknik.
    Lennartson, Bengt
    Chalmers University of Technology, Control Engineering Lab, Göteborg, Sweden.
    Low order sampled-data H∞ control2003Ingår i: Decision and Control, 2003. Proceedings. 42nd IEEE Conference on, 2003, Vol. 3, s. 2308-2313 Vol.3Konferensbidrag (Refereegranskat)
    Abstract [en]

    A method for obtaining low order sampled-data H∞ controllers is presented. The method is mainly based on a parametric static feedback controller for a plant that is augmented with the controller dynamics. The design of a full-order controller is a convex problem, while the optimisation problem for lower order controllers is non convex. The proposed method starts with design of a full-order sampled-data controller using Riccati equations. Then this controller is reduced by an ordinary model reduction technique, and the reduced controller is used as an initial value for an iterative procedure using linear matrix inequalities (LMIs) in the search for an optimal controller. The matrix inequalities are in fact linear in either the Lyapunov matrix or the static controller matrix, why the solution to the non convex problem fundamentally is given by a bilinear matrix inequality (BMI). The order of the controller is reduced until the closed loop performance degrades too much. Simulations are shown for the control of a time delayed SISO-plant where the controller order can be reduced from 8th to 3rd order. Results are also shown from control of a MIMO-model of a jet engine where the reduction is successful from 15th to 4th order. It is argued that the non convexity is handled efficiently since the procedure uses a model reduction of the full-order controller as initial value.

  • 9.
    Christiansson, Anna-Karin
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för automation och datateknik.
    Lennartson, Bengt
    Chalmers University of Technology, Control Engineering Lab, SE-41 2 96 Goteborg, Sweden .
    Toivonen, H.
    Åbo Akademi University, Department of Chemical Engineering, FIN-20500 Abo, Finland .
    Continuous-, discrete- and sampled-data- H∞ˆž control - a unified framework2000Ingår i: IEEE Proceedings: Conference on Decision and Control (CDC), ISSN 0191-2216, Vol. 2, s. 1936-1941Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a unified and general framework for H∞-control in both continuous time, discrete time and combinations of these. The general result is a hybrid continuous-/discrete-time H∞ˆž-controller. Using a compact hybrid notation, the work shows a close relationship between the continuous-and discrete-time solutions. In fact, the pure continuous and discrete time equations may be obtained as two similar interpretations of the general result. There are no assumptions made on certain system matrices being zero or normalised, e.g. D11 = 0. The method is Riccati equation (RE) based, and it is shown how the continuous REs can be "lifted" into discrete ones reflecting the system behaviour during the period. Typical applications are control of continuous-time or discrete-time periodic systems, as well as multirate and sampled-data control, including mixed continuous and sampled-data measurements.

  • 10.
    Christiansson, Anna-Karin
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för automation och datateknik.
    Lennartson, Bengt
    Chalmers University of Technology, Control Engineering Lab, Göteborg, Sweden.
    Toivonen, H.T.
    Åbo Akademi University, Department of Chemical Engineering, Åbo, Finland..
    Sampled-data H∞ˆž-control for time-varying hybrid systems2001Ingår i: Dynamics of continuous, discrete and impulsive systems, ISSN 1201-3390, E-ISSN 1918-2538, Dynamics of Continuous, Discrete and Impulsive Systems Series B: Applications and Algorithms, ISSN 1492-8760, Vol. 8, nr 4b, s. 427-444Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents sampled-data H∞ˆž-control of linear mixed continuous-time and discrete-time systems, including a mix of continuous-time and discrete-time performance signals and disturbances. However, neither continuous-time control signals nor continuous-time measurements are included. The sampling may well be multirate, i.e. different signals may be sampled by different rates, as long as a periodic pattern is repeated over the period, consisting of a number of sampling steps. In fact, the results are applicable even to arbitrary linear time-varying systems. The sampled-data system is discretised such that the continuous-time performance is reflected in the discretised or "lifted" system. This lifted system is combined with discrete-time updates at the sampling instants to achieve the sampled-data controller. The "hold-states" case is presented as a special application, when there is also a hold circuit at the controller output. The continuous-time Riccati equations with discrete-time updates then can be replaced by one discrete-time static feedback and filter Riccati equation respectively, which also reflect the intersample behaviour. Furthermore, convergence results between the discretised Riccati solutions and the corresponding continuous-time solutions are shown, when the sampling interval decreases towards zero. Simulations are shown when the results are applied to the control of a MIMO jet-engine model.

  • 11.
    Christiansson, Anna-Karin
    et al.
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap, Avd för elektro- och lantmäteri.
    Ottosson, Mattias
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap, Avd för elektro- och lantmäteri.
    Sensor and control system for metal deposition using robotised laser welding.2006Ingår i: 16th International Conference on Computer Technology in Welding and Manufacturing: Kiev, Ukraine, 2006, s. 328-332Konferensbidrag (Refereegranskat)
  • 12.
    Danielsson, Fredrik
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap.
    Off-line programming, verification and optimisation of industrial control systems2002Doktorsavhandling, monografi (Övrigt vetenskapligt)
  • 13.
    Danielsson, Fredrik
    et al.
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap.
    Hansbo, Anita
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap.
    Control system verification by emulation: an application to off-line pressline throughput rate orpimization2002Ingår i: Journal of Advanced Manufacturing Systems, ISSN 0219-6867, E-ISSN 1793-6896, Vol. 1, nr 2, s. 159-172Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study is part of a research project aims at off-line programming and verification of industrial control systems. In this paper, an off-line method for press line throughput rate optimization and control system verification is proposed, implemented and evaluated. The main tool is a virtual press station, developed by the first author, consisting of an emulated control system for a feeder/extractor robot which communicates with 3D-simulated production equipment. Moreover, several virtual press stations have been coupled and synchronized in a virtual press line. An important feature of the system is that the virtual robot controller is emulated, yielding an exact representation of the control logic and the possibility to run the entire system in virtual real time. The application considered is a sheet metal forming process where it is difficult to achieve maximum capacity utilization. There is much to gain if the control logic is improved and the throughput rate is increased. For this purpose, an automated robot motion optimization method is implemented and evaluated, using the virtual press line.

  • 14.
    Danielsson, Fredrik
    et al.
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap.
    Moore, P
    Eriksson, P
    Validation, off-line programming and optimisation of industrial control logic2003Ingår i: Mechatronics (Oxford), ISSN 0957-4158, E-ISSN 1873-4006, Vol. 13, nr 6, s. 571-585Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This article proposes a classification of different methods for validation, off-line programming and optimisation of control logic. The classification is an overview of different methods available and includes advantages and disadvantages for each method. The method overview points out a superior method, control system emulation, which is the most cost-effective and flexible method. The control system emulation method is also general and may be applied to validate and optimise control logic in various applications. Further, the method is compared with several other methods for validation of industrial control systems. However the method requires a standardised system architecture. This article proposes such architecture for the control system emulation method. Here, a control system emulator has also been implemented with the specific system architecture described in this article. An application case is also provided to demonstrate an approach to the integration of a control system emulator into a virtual manufacturing system.

  • 15.
    De Backer, Jeroen
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Robotic Friction Stir Welding for Flexible Production2012Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Friction Stir Welding eller ”friktionsomrörningssvetsning” är en svetsprocess som kräver ett roterande verktyg som genom friktionsvärme får materialet att mjukna. Verktyget blandar runt det plastiska materialet mekaniskt och skapar en fog av hög kvalité. Processen fungerar utan gas, utan rök, utan tillsatsmaterial och utan att smälta materialet. Alla dessa fördelar skapar stort industriellt intresse inom flera branscher. Idag används tekniken nästan uteslutande i styva maskiner som svetsar raka eller cirkulära fogar och framförallt för aluminium. Eftersom processen kräver stora krafter mellan material och verktyg är det svårt att implementera processen på en robot. En robot möjliggör svetsning av tredimensionella geometrier och ökar dessutom flexibiliteten.  Flera forskargrupper runt i världen har tagit fram en fungerande FSW robot som kan svetsa tunn lättviksmaterial som aluminium med hög kvalitet. Användningen i industrin av FSW robotar är däremot obefintlig och det finns ett antal anledningar till det. Först är roboten vek vilket gör att verktyget kan missa svetsfogen i hårda material och svetsdefekter kan uppstå. En annan anledning är at det inte finns en användbar automatiserad processtyrning tillgänglig, mest för att FSW är en robust process och inte kräver en avancerad styrning vid svetsning av raka fogar.

    De praktiska arbeten som redovisas i denna licentiatuppsats är huvudsakligen utförda i en robotiserad FSW-demonstrator på Högskolan Väst. FSW-roboten är en modifierad industrirobot som är försetts med spindel och kraftåterkoppling för att styra kraften som roboten applicerar på arbetsstycket.

    Detta arbete har identifierat ett antal problem som behöver lösas för att få en robust robotiserad FSW process i en flexibel produktionsmiljö. I denna licentiatrapport beskrivs en lösning hur en typ av svetsdefekter kan förhindras genom en sensorbaserad bankompensering. Både en kamera- och lasersensor-baserad mätmetod presenteras. En annan bankompenseringsstrategi är beskriven, som använder kraftsensorn från befintlig kraftåterkoppling istället för att lägga till extra sensor. Denna strategi kan utvecklas till en komplett utböjningsmodell på roboten i hela arbetsområdet. Robotens begränsningar gällande svetsbarhet av hårda material har undersökts och med hjälp av parameteroptimering och förvärmning kan även hårda nickelbaserade legeringar svetsas med roboten.

  • 16.
    Därnemyr, Johan
    Högskolan Väst, Institutionen för ingenjörsvetenskap.
    Åtgärder för att minimera kommunikationsstörningar vid avläsning av elmätare via elnätet2009Självständigt arbete på grundnivå (yrkesexamen), 10 poäng / 15 hpStudentuppsats
    Abstract [sv]

    Detta examensarbete tar upp frågan om kommunikationsproblem mellan de komponenter som ingår i ADDAX systemet, till största del de problem som uppstår mellan router och mätare. ADDAX systemet är uppbyggt på ett hierarkiskt vis med ADDAX server högst upp och mätaren längs ned. Systemet kommunicerar via PLC ”power line comunication”. Uppgiften har varit att kartlägga hur mätsystemet fungerar, vilka geografiska problemområden som finns med avseende på kommunikations problem, lokalisering av störkällor, åtgärdning av dessa störkällor och framtagande av ett flödesschema som skall kunna användas av montörerna vid felsökning i systemet. Arbetet inleddes med att ta fram underlag för vilka områden som påverkas av störningar i elnätskommunikationen. Detta gjordes med hjälp av programmet ”TC Meter Surv SA Edition 0.61” som arbetar mot ADDAX systemets databas för att se vilka mätare som är installerade och vilka som kommunicerar med systemet. Efter vissa problem togs två områden fram, ett på landsbygden och ett i centrala Grästorp. Vid mätning i dessa områden användes till en början två instrument, PL-monitor och HF+. HF+ visade sig vara överflödigt då samma information ges av PL-monnitor båda versioner visar på vilka störningsnivåer som finns i elnätet. HF+ är mer svårtolkat då användaren själv måste ta ställning till informationen som visas medan PL-monnitor enbart visar på den störning som stör ut kommunikationen. Då mätningarna genomförts och analyserats har det visat sig att programmet ej fungerat tillfredställande och att fel information om antal felaktiga mätare i de område som är beläget i centrala Grästorp, detta har resulterat i att en ny slutsats dragits där istället för en störning i LV nu problemet verkar ligga i MV. Kommunikations problemet på landsbygden kan troligtvis lösas med att installera filter hos de kunder vars mätare ej kommunicerar. Andra åtgärder som kan vara aktuella vid framtida kommunikationsproblem kan vara byta av kommunikations fas på mätaren, flytt av mätaren till matningsskåp, installation av repeterare eller att i samråd med kund få denna att stänga av störande utrustning vissa tider på dygnet. En slutsats som dragits av de erfarenheter som ackumulerats under projektets gång är att all mjukvara bör uppdateras och att master-routrar ersätts med en nyare version.

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  • 17.
    Ericsson, Mikael
    et al.
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap.
    Nylén, Per
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap.
    Danielsson, Fredrik
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap.
    Carlsson, Henrik
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap.
    Off-line programming of robots for metal deposition2005Ingår i: Trends in welding research: Proceedings of the 7th international conference, May 16-20. Pine Mountain, Georgia, 2005, s. 629-634Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Metal Deposition (MD) is a rapid prototyping technique to build parts by depositing metal in a required fashion. When a complex-shaped part is to be built, a simulation tool is needed to define robot trajectories. Three different simulation-based methods for robot trajectory generation are introduced and compared in this study. The methods are; reversed milling, adapted rapid prototyping and application programming in a computer aided robotics software. All methods were shown capable of creating robot paths for complex shapes, with the CAR software approach being the most flexible. Using this method, the geometry to be built is automatically sliced into layers and a robot path is automatically generated. The method was tentatively evaluated and appears to provide a powerful technique in the design and optimisation of robot paths for MD. Experiments showed that it is possible to manufacture fully dense parts using an Nd-Yag laser.

     

  • 18.
    Hagqvist, Petter
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för automationssystem.
    Christiansson, Anna-Karin
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för automationssystem.
    Heralic, Almir
    GKN Aerospace.
    Automation of a laser welding system for additive manufacturing2015Ingår i: Proceedings of the 2015 IEEE International Conference on Automation Science and Engineering / [ed] Kazuhiro Saitou, Univ. of Michigan, IEEE, 2015, s. 900-905Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents the benefits and challenges ofusing a standard robotised laser welding cell for additive manufacturing(AM). Additive manufacturing, sometimes denoted3D-printing or rapid prototyping, has lately met strong interestin several areas of society, and a variety of technologies andmaterials have been in focus. The current paper summarisesautomation efforts for AM of advanced aero engine componentsusing high power laser with welding optics as power source formelting metal wire and using an industrial robot for obtaininga 3-dimensional feature shape. The challenges are related to theprocess itself encountering high and repeated temperatures withmelting and solidification of the metal as the main players. Themajor research solutions discussed in this paper are relatedto automation issues for obtaining a stable process and tohave control of the temperatures and temperature changes thatthe metals encounter during the process. The solutions aresuccessfully implemented in an industrial laser welding cell.

  • 19.
    Heralic, Almir
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Monitoring and Control of Robotized Laser Metal-Wire Deposition2012Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    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.

  • 20.
    Heralic, Almir
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Charles, Corinne
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion. Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Dzevad, Imamovic
    Volvo Aero Coorporation.
    Christiansson, Anna-Karin
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Lennartson, Bengt
    Dep of signal and systems, Chalmers.
    Towards stable high-speed metal-wire deposition, Part I: Parameter studyIngår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387Artikel i tidskrift (Refereegranskat)
  • 21.
    Heralic, Almir
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Christiansson, Anna-Karin
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Automatic in-process control of laser metal-wire deposition based on sensor feedback2011Ingår i: 30th Interantional Congress on Applications of Lasers & Electro-Optics, ICALEO 2011: Orlando October 23-27, 2011. Code 87581|, 2011, s. 211-220Konferensbidrag (Refereegranskat)
    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.

  • 22.
    Heralic, Almir
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Christiansson, Anna-Karin
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Lennartson, Bengt
    Dep of signal and systems, Chalmers.
    Height control of laser metal-wire deposition based on iterative learning control and 3D scanning2012Ingår i: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 50, nr 9, s. 1230-1241Artikel i tidskrift (Refereegranskat)
    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.

  • 23.
    Heralic, Almir
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Christiansson, Anna-Karin
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för automation och datateknik.
    Lennartson, Bengt
    Dep of signal and systems, Chalmers.
    Towards stable high-speed metal-wire deposition, Part II: Automatic deposition using feedback controlIngår i: Artikel i tidskrift (Refereegranskat)
  • 24.
    Heralic, Almir
    et al.
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap, Avd för elektro- och lantmäteri.
    Christiansson, Anna-Karin
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap, Avd för elektro- och lantmäteri.
    Ottosson, Mattias
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap, Avd för elektro- och lantmäteri.
    Hurtig, Kjell
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap, Avd för maskinteknik.
    Lennartson, Bengt
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap, Avd för elektro- och lantmäteri. Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Automation of Robotized Laser Metal-Wire Deposition2007Ingår i: Proceedings of the ninth IASTED International Conference on Control and Applications: Montreal, Canada, ACTA Press , 2007, s. ID 658-075-Konferensbidrag (Refereegranskat)
  • 25.
    Heralic, Almir
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Christiansson, Anna-Karin
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Ottosson, Mattias
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Lennartson, Bengt
    Chalmers Tekniska Högskola.
    Increased stability in laser metal wire deposition through feedback from optical measurements2010Ingår i: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 48, nr 4, s. 478-485Artikel i tidskrift (Refereegranskat)
    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.

  • 26.
    Heralic, Almir
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Ottosson, Mattias
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Christiansson, Anna-Karin
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik. Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Lennartson, Bengt
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS). Dep of signal and systems, Chalmers.
    Automation of laser metal deposition for the manufacture of fully dense structures2011Ingår i: 4th International Swedish Production Symposium, SPS11: 3-4 May, Lund, Sverige / [ed] Jan-Eric Ståhl, Swedish Productio Academy , 2011, s. 219-227Konferensbidrag (Refereegranskat)
  • 27.
    Heralic, Almir
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Ottosson, Mattias
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Kristiansson, Anna-Karin
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik. Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Norlander, Torbjörn
    Volvo Aero Coorporation.
    Geometry control of laser metal deposition for the manufacture of complex structures in the aero industry2011Ingår i: 20th International Society for Airbreathing Engines Conference, ISABE 2011: September 12-16, 2011 Gothenburg, 2011, s. 1666-1674Konferensbidrag (Refereegranskat)
  • 28.
    Heralic, Almir
    et al.
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap, Avd för elektro- och lantmäteri.
    Wolff, Krister
    Chalmers University of Technology.
    Wahde, Mattis
    Chalmers University of Technology.
    Central Pattern Generators for Gait Generation in Bipedal Robots2007Ingår i: Humanoid Robots: New Developments, I-Tech Education and Publishing , 2007, s. 285-304Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 29.
    Lennartson, Bengt
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för automationssystem. Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS). Chalmers University of Technology, Department of Signals and Systems, Gothenburg, Sweden.
    Bengtsson, Kristofer
    Sekvensa AB.
    Wigstrom, Oskar
    Chalmers.
    Riazi, Sarmad
    Chalmers.
    Modeling and Optimization of Hybrid Systems for the Tweeting Factory2016Ingår i: IEEE Transactions on Automation Science and Engineering, ISSN 1545-5955, E-ISSN 1558-3783, Vol. 13, nr 1, s. 195-205Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, a predicate transition model for discrete-event systems is generalized to include continuous dynamics, and the result is a modular hybrid predicate transition model. Based on this model, a hybrid Petri net including explicit differential equations and shared variables is also proposed. It is then shown how this hybrid Petri net model can be optimized based on a simple and robust nonlinear programming formulation. The procedure only assumes that desired sampled paths for a number of interacting moving devices are given, while originally equidistant time instances are adjusted to minimize a given criterion. This optimization of hybrid systems is also applied to a real robot station with interacting devices, which results in about 30% reduction in energy consumption. Moreover, a flexible online and event-based information architecture called the Tweeting Factory is proposed. Simple messages (tweets) from all kinds of equipment are combined into high-level knowledge, and it is demonstrated how this information architecture can be used to support optimization of robot stations.

  • 30.
    Lennartson, Bengt
    et al.
    Chalmers University of Technology, Control Engineering Lab, Göteborg, Sweden.
    Middleton, R.
    Christiansson, Anna-Karin
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för automation och datateknik.
    Unified, periodic & sampled data H control using the delta operator2004Ingår i: Decision and Control, 2004. CDC. 43rd IEEE Conference on, 2004, Vol. 3, s. 2364-2369Konferensbidrag (Refereegranskat)
    Abstract [en]

    A unified and general framework is presented for H<sub>&infin;</sub> control of mixed continuous-time and discrete-time time-varying (periodic) systems. Using the delta operator, a close relationship is shown between the continuous- and discrete-time solutions. No assumptions are made on certain system matrices being zero or normalized, which makes the approach general and easy to apply. A combined continuous/discrete-time lifting procedure is shown to be useful, especially for ill-conditioned systems. This procedure together with the delta formalism results in a numerically robust design method concerning both short and long sampling periods for systems with W-conditioned dynamics, including widely spread eigenvalues.

  • 31.
    Lennartson, Bengt
    et al.
    Chalmers University of Technology, Control Engineering Lab, Göteborg, Sweden.
    Middleton, R.
    Christiansson, Anna-Karin
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för automation och datateknik.
    McKelvey, T.
    Low order sampled data H control using the delta operator and LMIs2004Ingår i: Decision and Control, 2004. CDC. 43rd IEEE Conference on, 2004, Vol. 4, s. 4479-4484Konferensbidrag (Refereegranskat)
    Abstract [en]

    A procedure for H optimization of low order controllers for discrete-time and sampled-data systems is presented in this paper. Generally, low order H controllers may be achieved by solving bilinear matrix inequalities (BMIs). In this paper an iterative alternation between two LMIs gives a suboptimal solution. To avoid local minima in this search the initial controller is obtained by a frequency weighted controller reduction scheme, where the closed loop properties of a full order controller is taken into account. A minimal number of parameters in the state space realization of the controller also reduces the complexity and improves numerical robustness. The complete presentation is based on delta operator models, which shows a close relationship between the continuous- and discrete-time solutions. The sensitivity of the ordinary discrete-time shift operator LMI formulation to small sampling periods is also analyzed.

  • 32.
    Lievain, Guillaume
    et al.
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap.
    Rupil, Damien
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap.
    Study of different sensor systems and investigation about poseye for positioning2004Rapport (Övrig (populärvetenskap, debatt, mm))
  • 33.
    Nia, Nima Khansari
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för automation och datateknik.
    Efficient simulation and optimization for tandem press lines2012Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 34.
    Nilsson, Anders
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Danielsson, Fredrik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Bennulf, Mattias
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Svensson, Bo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    A Classification of Different Levels of Flexibility in an Automated Manufacturing System and Needed Competence2021Ingår i: Towards Sustainable Customization: Bridging Smart Products and Manufacturing Systems: Proceedings of the 8th Changeable, Agile, Reconfigurable and Virtual Production Conference (CARV2021) and the 10th World Mass Customization & Personalization Conference (MCPC2021), Aalborg, Denmark, October/November 2021 / [ed] Ann-Louise Andersen, Rasmus Andersen, Thomas Ditlev Brunoe, Maria Stoettrup Schioenning Larsen, Kjeld Nielsen, Alessia Napoleone, Stefan Kjeldgaard, Springer Science and Business Media Deutschland GmbH , 2021, s. 27-34Konferensbidrag (Refereegranskat)
    Abstract [en]

    Mass customization has become more attractive but requires a transformation towards more flexible solutions in contrast to dedicated manufacturing systems. Flexibility includes complex tasks such as the introduction of new products or new manufacturing processes as well as to efficiently handle daily balancing. The main challenge when it comes to flexibility in manufacturing is to be able to handle the technical aspects and still be competitive. In this article we consider the cost for flexibility to include two main things; (1) setup time, e.g., time for planning, design, programming and configuration, installation, ramp-up, scrapping of old equipment, preparation of facility, hardware installation, and (2) need of competence, inhouse knowledge, external competence, or external expert competence. This article presents an overview of available solutions and the level of flexibility and the level of competence that is needed for a reconfiguration one can expect out of a specific solution. Further, most of the existing solutions found do not consider or address the full problem of flexibility. However, we describe a possible future of industrial concept: Plug & Produce, which can address flexibility within manufacturing more completely and sustainably over time. Methods for configuration instead of programming are developed by University West. 

  • 35.
    Pereira Ferreira, Rafael
    et al.
    Federal Institute of Maranhão, Department of Mechanic, Barra do Corda (BRA) ; Federal University of Uberlandia, Uberlândia ( BRA).
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Federal University of Uberlandia, Center for Research and Development of Welding Processes, Uberlândia (BRA).
    Concept of a Novel Path Planning Strategy for Wire + Arc Additive Manufacturing of Bulky Parts : Pixel2021Ingår i: Metals, E-ISSN 2075-4701, Vol. 11, nr 3, s. 1-20, artikel-id 498Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An innovative trajectory strategy was proposed and accessed for wire arc additive manufacturing (WAAM), applicable to different and more complex geometries, rather than being a single solution. This strategy, named Pixel, can be defined as a complex multitask procedure to carry out optimized path planning, whose operation is made through computational algorithms (heuristics), with accessible computational resources and tolerable computational time. The model layers are fractioned in squared grids, and a set of dots is systematically generated and distributed inside the sliced outlines, resembling pixels on a screen, over which the trajectory is planned. The Pixel strategy was based on creating trajectories from the technique travelling salesman problem (TSP). Unlike existing algorithms, the Pixel strategy uses an adapted greedy randomized adaptive search procedure (GRASP) metaheuristic, aided by four concurrent trajectory planning heuristics, developed by the authors. Interactions provide successive trajectories from randomized initial solutions (global search) and subsequent iterative improvements (local search). After all recurrent loops, a trajectory is defined and written in machine code. Computational evaluation was implemented to demonstrate the effectof each of the heuristics on the final trajectory. An experimental evaluation was eventually carried out using two different not easily printable shapes to demonstrate the practical feasibility of the proposed strategy.

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  • 36.
    Ramanathan, Prabhu K.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Autonomous Driving Cars: Decision-Making2021Ingår i: Internet of Vehicles and its Applications in Autonomous Driving / [ed] Gupta, Nishu; Prakash, Arun; Tripathi, Rajeev, Springer, 2021, s. 31-39Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    This study is an overview of autonomous cars and also the challenges faced in the field of autonomous cars. Recent advances are being made in the field of planning, perception, and decision-making for autonomous vehicles. This has led to great improvements in functional capabilities; several prototypes are already on roads. The challenge is to obtain the safe execution of vehicles in all driving situations. In this study, we will see recent methodologies for vehicle control using kinematic and dynamic model, collaborative autonomy, decision-making system for autonomous vehicles using convolutional neural network, path planning for autonomous vehicles using model predictive control, real-time decision-making for autonomous city vehicle using world model and driving maneuver system, and intention-aware autonomous driving decision-making using hidden Markov model and partially observable Markov decision process.

  • 37.
    Ramasamy, Sudha
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Zhang, Xiaoxiao
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Bennulf, Mattias
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Danielsson, Fredrik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Automated Path Planning for Plug Produce in a Cutting-tool Changing Application2019Ingår i: 24th IEEE International Conference on Emerging Technologies and Factory Automation (ETFA), 2019, s. 356-362, artikel-id 8869398Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, a path planning algorithm is designed and tested with a real robot for a Plug & Produce demonstrator. The demonstrator is divided into modules that can be connected and removed. Modules are used for various processes like tool change and storage. This paper focuses on the process of cutting-tool change for the production industry. The Plug & Produce demonstrator uses a multi-agent system where parts and resources are agents. A part agent, e.g., a cutting-tool, can request a robot to perform skills like transportation. This requires the robot to be autonomous. The aim of this paper is to automate the path planning for industrial robotics in a Plug & Produce system. This is done by implementing a sampling based RRT algorithm combined with a collision detection function in RobotStudio. With various real time scenarios, the path planning execution time is observed and presented in the paper.

  • 38.
    Ryberg, Anders
    et al.
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap, Avd för elektro- och lantmäteri.
    Christiansson, Anna-Karin
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap, Avd för elektro- och lantmäteri.
    Eriksson, Kenneth
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för naturvetenskap, lantmäteri- och maskinteknik.
    Accuracy Investigation of a Vision Based System for Pose Measurements2006Ingår i: Control, Automation, Robotics and Vision, 2006. ICARCV '06. 9th International Conference on, 2006, s. 1-6Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The accuracy of a pose measurement system, called PosEye, is investigated. PosEye is a system for real time measurement of the position and orientation, the pose, of a camera (sensor) using the information in its image. This sensor is aimed to be mounted on an industrial robot for welding. The investigation was done by comparing the PosEye system position output to that of a coordinate measuring machine. Sources of errors are identified, and suggestions for improvements are made

  • 39.
    Ryberg, Anders
    et al.
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap, Avd för elektro- och lantmäteri.
    Christiansson, Anna-Karin
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap, Avd för elektro- och lantmäteri.
    Eriksson, Kenneth
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap, Avd för matematik och naturvetenskap.
    Lennartson, Bengt
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS). Chalmers University of Technology.
    A new Camera Model and Algorithms for higher Accuracy and better Convergence in Vision-based Pose Calculations2006Ingår i: Mechatronics and Automation, Proceedings of the 2006 IEEE International Conference on, 2006, s. 194-199Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents novel strategies for better calibration and pose calculations of a system for determining the pose, i.e. position and orientation, of a camera. The system in question has a camera aimed to be placed on the hand of an industrial robot for welding, but is useful for any application with a need for measuring position and/or orientation. To calculate the pose of the camera circular reference points that can be recognized in the images are distributed in the working area. From their 2D image coordinates the 6D pose of the camera can be calculated. First the system is calibrated, i.e. the positions of the reference points and the camera parameters are determined. This is done by first taking images of the reference points from different locations, and then do a "total calibration" procedure to calculate the unknown parameters. For a specific system, called PosEye, it was concluded that the accuracy needs to be improved for welding applications. Also a method for making the calculations converge more easily, was needed. To meet these demands a new camera model is proposed, and three preprocessing calculation steps are presented. The new camera model increases accuracy by considering more distortion effects. The preprocessing steps give better initial values for more robust convergence of the algorithms and increased accuracy

  • 40.
    Sikström, Fredrik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Simulation-based feedback control of welding processes2008Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    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.

  • 41.
    Svensson, Bo
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Danielsson, Fredrik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Lennartson, Bengt
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik. Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Simulation based optimization of a sheet-metal press line2009Ingår i: IEEE Conference on Emerging Technologies & Factory Automation, ETFA 2009, 2009, s. 1-8Konferensbidrag (Refereegranskat)
    Abstract [en]

    An off-line optimization of a sheet-metal press line is performed with improved production performances, both in terms of increased production rate and smoother robot motions. Smooth motions prevent the sheet-metal to slide out of position or even fall out, thereby causing lengthy down times. The simulation based method use a process optimizer connected to a time synchronized virtual manufacturing model including real industrial control systems, e.g. PLC. The key benefit herein is that all tuned control system parameters can be directly downloaded to the real press line without any post-processing or transformations. The challenge to find suitable optimization algorithms for a press line that handle highly nonlinear, discontinuous functions; considerable number of parameters; and long evaluation times is reached.

  • 42.
    Svensson, Bo
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Danielsson, Fredrik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Lennartson, Bengt
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Virtual Real-Time Model: a Tool for Increased Production2005Ingår i: Mekatronikmöte 2005, 2005Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Increasing the total number of produced components in a pre-existing production line, which is a large-scale mechatronic system, is a continuous and never-ending story in industry. There is a need for tools and methods to develop the control software off-line, i.e. to manage programming, verification, validation, optimisation, training new operators, etc. without using the real production line. Therefore a general Virtual Real-Time Model, VRTM, for simulating industrial production lines is proposed. The VRTM is intended to be used for off-line control software development and is aimed at increase the throughput in highly automated production lines. The main features of the VRTM are that the same control software is used as in the real production line and that virtual real-time is used, implying that everything is time-synchronised and works in the same way as in the real production line (including security functions). An applied VRTM simulating a sheet-metal press line is implemented and validated. A comparison test with the press line at Volvo Car Manufacturing in Göteborg is performed with a satisfactory agreement. This shows that the VRTM can be used for off-line control software development.

  • 43.
    Windfäll, Åsa
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap, Avd för maskinteknik.
    Principles of robust and accurate computational 3D positioning from 2D image2005Rapport (Övrig (populärvetenskap, debatt, mm))
    Ladda ner fulltext (pdf)
    FULLTEXT01
  • 44.
    Yücel, Baris
    et al.
    Kungliga Tekniska Högskolan, Stockholm.
    Christiansson, Anna Karin
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap, Avd för elektro- och lantmäteri.
    Ring, Dan
    Volvo Aero Corporation, Trollhättan.
    Automatic Generation of Multivariable Sampled-data Controllers for Jet-engines2006Ingår i: Proceedings of Reglermöte 2006, 2006Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    In this contribution, it is shown how multivariable sampled-data controllers can be generated for a set of linearized models. The size of this set makes an automatic generation of controllers more practical and less time consuming. The control strategy is robust loopshaping according to Glover/McFarlane. The generated controllers are to be used for the military turbofan engine F404-RM12 which is currently used in the Swedish air fighter JAS39 Gripen.

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