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  • 1.
    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.

  • 2.
    Hagqvist, Petter
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för automation och datateknik.
    Heralic, Almir
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Christiansson, Anna-Karin
    Högskolan Väst, Institutionen för teknik, matematik och datavetenskap, Avd för elektro- och lantmäteri.
    Lennartson, Bengt
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för tillverkningsprocesser. Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS). Chalmers.
    Resistance based iterative learning control of additive manufacturing with wire2015Ingår i: Mechatronics (Oxford), ISSN 0957-4158, E-ISSN 1873-4006, Vol. 31, s. 116-123Artikel i tidskrift (Refereegranskat)
    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.

  • 3.
    Hagqvist, Petter
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för automation och datateknik.
    Heralic, Almir
    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
    Chalmers.
    Resistance measurements for control of laser metal wire deposition2014Ingår i: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 54, nr March, s. 62-67Artikel i tidskrift (Refereegranskat)
    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.

  • 4.
    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.

  • 5.
    Heralic, Almir
    Högskolan Väst, Institutionen för ingenjörsvetenskap.
    Towards full Automation of Robotized Laser Metal-wire Deposition2009Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Metal wire deposition by means of robotized laser welding offers great saving potentials, i.e. reduced costs and reduced lead times, in many different applications, such as fabrication of complex components, repair or modification of high-value components, rapid prototyping and low volume production, especially if the process can be automated. Metal deposition is a layered manufacturing technique that builds metal structures by melting metal wire into beads which are deposited side by side and layer upon layer. This thesis presents a system for on-line monitoring and control of robotized laser metal wire deposition (RLMwD). The task is to ensure a stable deposition process with correct geometrical profile of the resulting geometry and sound metallurgical properties. Issues regarding sensor calibration, system identification and control design are discussed. The suggested controller maintains a constant bead height and width throughout the deposition process. It is evaluated through real experiments, however, limited to straight line deposition experiments. Solutions towards a more general controller, i.e. one that can handle different deposition paths, are suggested.

    A method is also proposed on how an operator can use different sensor information for process understanding, process development and for manual on-line control. The strategies are evaluated through different deposition tasks and considered materials are tool steel and Ti-6Al-4V. The developed monitoring system enables an operator to control the process at a safe distance from the hazardous laser beam.

    The results obtained in this work indicate promising steps towards full automation of the RLMwD process, i.e. without human intervention and for arbitrary deposition paths.

  • 6.
    Heralic, Almir
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Charles Murgau, Corinne
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    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)
  • 7.
    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.

  • 8.
    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.
    Hurtig, Kjell
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Ottosson, Mattias
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Lennartson, Bengt
    Chalmers.
    Control Design for Automation of Robotized Laser Metal-Wire Deposition2008Ingår i: Proceedings of the 17th IFAC World Congress, International Federation of Automatic Control , 2008, s. 14785-14791Konferensbidrag (Övrigt vetenskapligt)
    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.

  • 9.
    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.

  • 10.
    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 controlArtikel i tidskrift (Refereegranskat)
  • 11.
    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.
    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)
  • 12.
    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.
    Freeform Fabrication using Laser Metal-wire Deposition2007Ingår i: Proceedings from the 1st Swedish Production Symposium: 28-30 August, Gothenburg, Sweden, 2007, s. session 1.2-Konferensbidrag (Övrigt vetenskapligt)
  • 13.
    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.

  • 14.
    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.
    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)
  • 15.
    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.
    Hurtig, Kjell
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
    Kristiansson, Anna-Karin
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro- och automationsteknik.
    Visual feed-back for operator interaction in robotized laser metal deposition2008Ingår i: 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, s. 297-304Konferensbidrag (Övrigt vetenskapligt)
  • 16.
    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)
1 - 16 av 16
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