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BETA
Christiansson, Anna-KarinORCID iD iconorcid.org/0000-0001-5608-8636
Alternative names
Publications (10 of 57) Show all publications
Elefante, A., Nilsen, M., Sikström, F., Christiansson, A.-K., Maggipinto, T. & Ancona, A. (2019). Detecting beam offsets in laser welding of closed-square-butt joints by wavelet analysis of an optical process signal. Optics and Laser Technology, 109, 178-185
Open this publication in new window or tab >>Detecting beam offsets in laser welding of closed-square-butt joints by wavelet analysis of an optical process signal
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2019 (English)In: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 109, p. 178-185Article in journal (Refereed) Published
Abstract [en]

Robotized laser beam welding of closed-square-butt joints is sensitive to the positioning of the laser beam with respect to the joint since even a small offset may result in a detrimental lack of sidewall fusion. An evaluation of a system using a photodiode aligned coaxial to the processing laser beam confirms the ability to detect variations of the process conditions, such as when there is an evolution of an offset between the laser beam and the joint. Welding with different robot trajectories and with the processing laser operating in both continuous and pulsed mode provided data for this evaluation. The detection method uses wavelet analysis of the photodetector signal that carries information of the process condition revealed by the plasma plume optical emissions during welding. This experimental data have been evaluated offline. The results show the potential of this detection method that is clearly beneficial for the development of a system for welding joint tracking.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Laser beam welding, Joint tracking, Butt joints, Photodiode, Wavelet analysis
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-12832 (URN)10.1016/j.optlastec.2018.08.006 (DOI)000446949600023 (Scopus ID)
Funder
VINNOVA, 2016-03291
Available from: 2018-08-21 Created: 2018-08-21 Last updated: 2018-10-25Bibliographically approved
Nilsen, M., Sikström, F., Christiansson, A.-K. & Ancona, A. (2018). In-process Monitoring and Control of Robotized Laser Beam Welding of Closed Square Butt Joints. Paper presented at 8th Swedish Production Symposium (SPS 2018), Stockholm, Sweden, May 16-18, 2018. Procedia Manufacturing, 25, 511-516
Open this publication in new window or tab >>In-process Monitoring and Control of Robotized Laser Beam Welding of Closed Square Butt Joints
2018 (English)In: Procedia Manufacturing, E-ISSN 2351-9789, Vol. 25, p. 511-516Article in journal (Other academic) Published
Abstract [en]

In robotized laser welding of technical zero gap closed square butt joints it is critical to position the laser beam correct with regardsto the joint. Welding with an offset from the joint may cause lack of sidewall fusion, a serious defect that is hard to detect and gives a weak weld . When using machined parts with gap and misalignment between the parts that is close to zero, existing joint tracking systems will probably fail to track the joint. A camera based system using LED illumination and matching optical filters is proposed in this paper to address this issue. A high dynamic range CMOS camera and the LED illumination is integrated into the laser tool. The camera captures images of the area in front of the melt pool where the joint is visible and an algorithm based on the Hough transform and a Kalman filter estimates the offset between the laser spot and the joint position. Welding experiments, using a 6 kW fiber laser, have been conducted to evaluate the performance of the system. Promising results are obtained that can be used in the further development of a closed loop controlled joint tracking system.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Laser welding, Butt joints, Joint tracking, Camera
National Category
Production Engineering, Human Work Science and Ergonomics Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-12828 (URN)10.1016/j.promfg.2018.06.123 (DOI)
Conference
8th Swedish Production Symposium (SPS 2018), Stockholm, Sweden, May 16-18, 2018
Projects
VINNOVA project VarGa (2016-03291)MoRE program project Hy-Las - Hybrid sensing for understanding of laser welding technology for process control, no 608473
Funder
VINNOVA, 2016-03291EU, European Research Council, FP7/2007-2013
Note

Del av specialnumret Proceedings of the 8th Swedish Production Symposium (SPS 2018) Redaktörer: M. Onori, L. Wang, X. V. Wang och W. Ji

This work was supported by the VINNOVA project VarGa (2016-03291) and also the People Programme (MarieCurie Actions) of the European Unions Seventh Framework Programme (FP7/2007-2013) under REA grant agreement no 608473 (MoRE program project Hy-Las - Hybrid sensing for understanding of laser welding technology for processcontrol).

Available from: 2018-08-28 Created: 2018-08-28 Last updated: 2018-08-31Bibliographically approved
Nilsen, M., Sikström, F., Christiansson, A.-K. & Ancona, A. (2018). Robust vision-based joint tracking for laser welding of curved closed-square-butt joints. The International Journal of Advanced Manufacturing Technology, 1-12
Open this publication in new window or tab >>Robust vision-based joint tracking for laser welding of curved closed-square-butt joints
2018 (English)In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, p. 1-12Article in journal (Refereed) Epub ahead of print
Abstract [en]

Robotized laser beam welding of closed-square-butt joints is sensitive to how the focused laser beam is positioned in relation to the joint, and existing joint tracking systems tend to fail in detecting the joint when the gap and misalignment between the work pieces are close to zero. A camera-based system is presented based on a high dynamic range camera operating with LED illumination at a specific wavelength and a matching optical filter. An image processing algorithm based on the Hough transform extracts the joint position from the camera images, and the joint position is then estimated using a Kalman filter. The filter handles situations, when the joint is not detectable in the image, e.g., when tack welds cover the joint. Surface scratches, which can be misinterpreted as being the joint, are handled by a joint curve prediction model based on known information about the nominal path defined by the robot program. The performance of the proposed system has been evaluated off line with image data obtained during several welding experiments.

Place, publisher, year, edition, pages
London: Springer, 2018
Keywords
Laser beam welding, Joint tracking, Butt joints, Camera, Hough transform, Kalman filter
National Category
Materials Engineering Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13211 (URN)10.1007/s00170-018-3044-0 (DOI)
Projects
VINNOVA project VarGa
Funder
VINNOVA, 2016-03291
Note

First Online: 27 November 2018

Funders: SWE-DEMO MOTOR ; [2015-06047]

Available from: 2018-12-18 Created: 2018-12-18 Last updated: 2018-12-19Bibliographically approved
Kisielewicz, A., Sikström, F., Christiansson, A.-K. & Ancona, A. (2018). Spectroscopic monitoring of laser blown powder directed energy deposition of Alloy 718. Paper presented at 8th Swedish Production Symposium, SPS 2018, Stockholm, Sweden, 16-18 May, 2018. Procedia Manufacturing, 25, 418-425
Open this publication in new window or tab >>Spectroscopic monitoring of laser blown powder directed energy deposition of Alloy 718
2018 (English)In: Procedia Manufacturing, E-ISSN 2351-9789, Vol. 25, p. 418-425Article in journal (Refereed) Published
Abstract [en]

Experimental explorations of a spectrometer system used for in-process monitoring of the laser blown powder directed energy deposition of Alloy 718 is presented. Additive manufacturing of metals using this laser process experiences repeated heating and cooling cycles which will influence the final microstructure and chemical composition at every given point in the built. The spectrometer system disclosed, under certain process conditions, spectral lines that indicate vaporisation of chromium. Post process scanning electron microscope energy dispersive spectroscopy analysis of the deposited beads confirmed a reduction of chromium. Since the chromium concentration in Alloy 718 is correlated to corrosion resistance, this result encourages to further investigations including corrosion tests.

National Category
Metallurgy and Metallic Materials Production Engineering, Human Work Science and Ergonomics
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-13303 (URN)10.1016/j.promfg.2018.06.112 (DOI)
Conference
8th Swedish Production Symposium, SPS 2018, Stockholm, Sweden, 16-18 May, 2018
Note

Del av specialnumret Proceedings of the 8th Swedish Production Symposium (SPS 2018) Redaktörer: M. Onori, L. Wang, X. V. Wang och W. J

We would like to thank Mr. Kjell Hurting at University West in Trollhättan, Sweden for his help with running the experiments and Ms. Caterina Gaudiuso at INF-CNR Institute, Bari for the support in performing EDS analysis. We would also like to thank Ms. Paria Karimi Neghlani and Mr. Esmaeil Sadeghimeresht at University West for their valuable comments during discussions on the paper content. Additionally, we thank SUMANnext and DigiAM projects for funding the research.

Available from: 2018-12-20 Created: 2018-12-20 Last updated: 2018-12-20Bibliographically approved
Ericsson, M., Zhang, X. & Christiansson, A.-K. (2018). Virtual Commissioning of Machine Vision Applications in Aero Engine Manufacturing. In: Proceedings of The 15th International Conference on Control,Automation, Robotics and Vision, November 18-21, 2018: . Paper presented at 2018 15th International Conference on Control, Automation, Robotics and Vision (ICARCV) Marina Bay Sands Expo and Convention Centre, Singapore, November 18-21, 2018 (pp. 1947-1952). , Article ID 0293.
Open this publication in new window or tab >>Virtual Commissioning of Machine Vision Applications in Aero Engine Manufacturing
2018 (English)In: Proceedings of The 15th International Conference on Control,Automation, Robotics and Vision, November 18-21, 2018, 2018, p. 1947-1952, article id 0293Conference paper, Published paper (Refereed)
Abstract [en]

New aero engine design puts new demands on the manufacturing methods with increased automation level. Therefore, the use of vision sensors for control and guiding of industrial robots is being increasingly used. In such system, it is need to customise the machine vision system with real components in the real environment which is normally done close to the start-up of the production. This paper addresses a new concept for designing, programming, analysing, testing and verifying a machine vision application early in the design phase, called Virtual Machine Vision. It is based on a robot simulation software where the real machine vision application is simulated before the implementation in the production line. To verify the Virtual Machine Vision concept an advanced stereo vision application was used. Using two captured images from the robot simulated environment, camera calibration, image analysis and stereo vision algorithms are applied to determine a desired welding joint. The information of the weld joint, i.e. robot position and orientation for the weld path, are sent from the machine vision system to the robot control system in the simulation environment and the weld path is updated. The validation of the Virtual Machine Vision concept using the stereo vision application is promising for industrial use, and it is emphasised that the same programs are used in the virtual and real word.

Keywords
Vision for robots, Image-based modeling, Modeling and identification
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13390 (URN)978-1-5386-9581-4 (ISBN)
Conference
2018 15th International Conference on Control, Automation, Robotics and Vision (ICARCV) Marina Bay Sands Expo and Convention Centre, Singapore, November 18-21, 2018
Available from: 2019-01-09 Created: 2019-01-09 Last updated: 2019-01-09Bibliographically approved
Nilsen, M., Sikström, F., Christiansson, A.-K. & Ancona, A. (2017). Monitoring of Varying Joint Gap Width During Laser Beam Welding by a Dual Vision and Spectroscopic Sensing System. Paper presented at 16th Nordic Laser Materials Processing Conference, NOLAMP16. Physics Procedia, 89, 100-107
Open this publication in new window or tab >>Monitoring of Varying Joint Gap Width During Laser Beam Welding by a Dual Vision and Spectroscopic Sensing System
2017 (English)In: Physics Procedia, ISSN 1875-3892, E-ISSN 1875-3892, Vol. 89, p. 100-107Article in journal (Refereed) Published
Abstract [en]

A vision and spectroscopic system for estimation of the joint gap width in autogenous laser beam butt welding is presented. Variations in joint gap width can introduce imperfections in the butt joint seam, which in turn influence fatigue life and structural integrity. The aim of the monitoring approach explored here is to acquire sufficiently robust process data to be used to guide post inspection activities and/or to enable feedback control for a decreased process variability. The dual-sensing approach includes a calibrated CMOS camera and a miniature spectrometer integrated with a laser beam tool. The camera system includes LED illumination and matching optical filters and captures images of the area in front of the melt pool in order to estimate the joint gap width from the information in the image. The intensity of different spectral lines acquired by the spectrometer has been investigated and the correlation between the intensity of representative lines and the joint gap width has been studied. Welding experiments have been conducted using a 6 kW fiber laser. Results from both systems are promising, the camera system is able to give good estimations of the joint gap width, and good correlations between the signal from the spectrometer and the joint gap width have been found. However, developments of the camera setup and vision algorithm can further improve the joint gap estimations and more experimental work is needed in order to evaluate the robustness of the systems.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Laser beam welding; Butt joints; Varying gap width; Vision sensor; Spectroscopic sensor
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-11898 (URN)10.1016/j.phpro.2017.08.014 (DOI)2-s2.0-85037711817 (Scopus ID)
Conference
16th Nordic Laser Materials Processing Conference, NOLAMP16
Funder
VINNOVA, 2016-03291
Note

Funders: People programme (Marie Curie Actions) of the European Union's 29 seventh framework progamme (FP7/2007-2013), no 608473

Available from: 2017-12-11 Created: 2017-12-11 Last updated: 2019-01-29Bibliographically approved
Nilsen, M., Sikström, F., Christiansson, A.-K. & Ancona, A. (2017). Vision and spectroscopic sensing for joint tracing in narrow gap laser butt welding. Optics and Laser Technology, 96, 107-116
Open this publication in new window or tab >>Vision and spectroscopic sensing for joint tracing in narrow gap laser butt welding
2017 (English)In: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 96, p. 107-116Article in journal (Refereed) Published
Abstract [en]

The automated laser beam butt welding process is sensitive to positioning the laser beam with respect to the joint because a small offset may result in detrimental lack of sidewall fusion. This problem is even more pronounced incase of narrow gap butt welding, where most of the commercial automatic joint tracing system fail to detect the exact position and size of the gap. In this work, adual vision and spectroscopic sensing approach is proposed to trace narrow gap butt joints during laser welding. The system consists of a camera with suitable illumination and matched optical filters and a fast miniature spectrometer. An image processing algorithm of the camera recordings has been developed in order to estimate the laser spot position relative the joint position. The spectral emissions from the laser induced plasma plume has been acquired by the spectrometer, and based on the measurements of the intensities of selected lines of the spectrum, the electron temperature signal has been calculated and correlated to variations of process conditions. The individual performances of these two systems have been experimentally investigated and evaluated offline by data from several welding experiments where artificial abrupt as well as gradual excursions of the laser beam out of the joint were produced. Results indicate thata combination of the information provided by the vision and spectroscopic systems is beneficial for development of a hybrid sensing system for joint tracing.

Place, publisher, year, edition, pages
Guildford, Surrey: , 2017
Keywords
Laser beam welding, Joint tracing, Butt joints, Optical spectroscopy, Vision sensor, Hybrid sensing
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-10639 (URN)10.1016/j.optlastec.2017.05.011 (DOI)000405051800015 ()2-s2.0-85019735734 (Scopus ID)
Funder
VINNOVA, 2014-05227Knowledge Foundation, 2010/0283EU, FP7, Seventh Framework Programme, FP7/2007-2013
Note

Ingår i lic. avhandling

Available from: 2017-02-03 Created: 2017-02-03 Last updated: 2019-01-31Bibliographically approved
Nilsen, M., Sikström, F. & Christiansson, A. K. (2016). Joint tracking in zero gap laser beam welding using a vision sensor. In: The 7th International Swedish Production Symposium, SPS16, Conference Proceedings: 25th – 27th of October 2016. Paper presented at 7th Swedish Production Symposium (SPS), Lund, Sweden, October 25-27, 2016 (pp. 1-7). Lund: Swedish Production Academy
Open this publication in new window or tab >>Joint tracking in zero gap laser beam welding using a vision sensor
2016 (English)In: The 7th International Swedish Production Symposium, SPS16, Conference Proceedings: 25th – 27th of October 2016, Lund: Swedish Production Academy , 2016, p. 1-7Conference paper, Published paper (Refereed)
Abstract [en]

The paper describes a robust vision sensor system that can find very narrow gaps between metal sheets to be butt welded together. The use of automated laser beam welding is seen as a key enabler for efficient manufacturing by enabling narrow and deep welds with a limited heat affected zone and low thermal distortion of the welded components. It is sensitive to positioning the laser beam with respect to the joint position. Even a small off-set from the actual joint could result in detrimental lack of fusion. The system comprises a CMOS camera with optic filters integrated in the welding optics and appropriate LED illumination of the work piece. By analysing the spectral emissions during welding, illumination and matching optic filters have been chosen in a spectral range where the process disturbances are relatively low. In this way it has been shown possible to detect the joint position even during harsh welding conditions. Preliminary results from the first experiments show promising results, however more tests will be performed using different weld geometries etc. to verify the robustness of the algorithm.

Place, publisher, year, edition, pages
Lund: Swedish Production Academy, 2016
Keywords
Laser beam welding, joint tracing, narrow gap, butt weld
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-10162 (URN)
Conference
7th Swedish Production Symposium (SPS), Lund, Sweden, October 25-27, 2016
Available from: 2016-12-07 Created: 2016-11-23 Last updated: 2018-08-12Bibliographically approved
Hagqvist, P., Christiansson, A.-K. & Heralic, A. (2015). Automation of a laser welding system for additive manufacturing. In: Kazuhiro Saitou, Univ. of Michigan (Ed.), Proceedings of the 2015 IEEE International Conference on Automation Science and Engineering: . Paper presented at 11th IEEE International Conference on Automation Science and Engineering, CASE 2015; Elite Park Avenue HotelGothenburg; Sweden; 24 August 2015 through 28 August 2015 (pp. 900-905). IEEE
Open this publication in new window or tab >>Automation of a laser welding system for additive manufacturing
2015 (English)In: Proceedings of the 2015 IEEE International Conference on Automation Science and Engineering / [ed] Kazuhiro Saitou, Univ. of Michigan, IEEE, 2015, p. 900-905Conference paper, Published paper (Refereed)
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.

Place, publisher, year, edition, pages
IEEE, 2015
Keywords
Additive manufacturing, laser welding
National Category
Control Engineering Aerospace Engineering Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-8015 (URN)10.1109/CoASE.2015.7294213 (DOI)2-s2.0-84952778708 (Scopus ID)978-1-4673-8182-6 (ISBN)
Conference
11th IEEE International Conference on Automation Science and Engineering, CASE 2015; Elite Park Avenue HotelGothenburg; Sweden; 24 August 2015 through 28 August 2015
Note

Article number 7294213

Available from: 2015-08-31 Created: 2015-08-31 Last updated: 2018-08-12Bibliographically approved
Sikström, F., Christiansson, A.-K. & Lennartson, B. (2015). Model based feedback control of gas tungsten arc welding: An experimental study. In: Automation Science and Engineering (CASE), 2015 IEEE International Conference on: . Paper presented at 11th IEEE International Conference on Automation Science and Engineering, CASE 2015; Elite Park Avenue HotelGothenburg; Sweden; 24 August 2015 through 28 August 2015 (pp. 411-416). IEEE conference proceedings
Open this publication in new window or tab >>Model based feedback control of gas tungsten arc welding: An experimental study
2015 (English)In: Automation Science and Engineering (CASE), 2015 IEEE International Conference on, IEEE conference proceedings, 2015, p. 411-416Conference paper, Published paper (Refereed)
Abstract [en]

In order to obtain high structural integrity and joint performance in welding a transient heat conduction model has been utilized to design a model based feedback controller.Gas tungsten arc welding of work-pieces of austenitic steel have been simulated by the finite element method. The basis for controller design is a low order model obtained from parametric system identification. The identification has been performed both on the finite element simulation and on physical welding. The low order model responses show a good agreement with both the finite element simulation result and the physical process response. An experimental study has been performed to verify the approach. This study also explores what experiments are needed for a successful design. It is shown that model based control successfully mitigates perturbations that occur during welding.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2015
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-8299 (URN)10.1109/CoASE.2015.7294113 (DOI)2-s2.0-84952778514 (Scopus ID)
Conference
11th IEEE International Conference on Automation Science and Engineering, CASE 2015; Elite Park Avenue HotelGothenburg; Sweden; 24 August 2015 through 28 August 2015
Note

Article number 7294113

Available from: 2015-09-29 Created: 2015-09-29 Last updated: 2016-02-08Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-5608-8636

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