Quality Inspection System for Robotic Laser Welding of Double-Curved Geometries

Anders Faarbæk Mikkelstrup*, Mathias Thomsen, Kristoffer Stampe, Benny Ørtoft Endelt, Jens Boll, Ewa Kristiansen, Morten Kristiansen

*Corresponding author

Research output: Contribution to journalConference article in JournalResearchpeer-review

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Abstract

The quality of robotic laser welded parts is related to the joint location, the trajectory of the laser focal point and the process parameters. By performing in-process monitoring, it is possible to acquire sufficient process knowledge for post-inspection to evaluate the geometrical weld quality. The existing solutions for such systems operate along linear welds. This paper contributes with a quality inspection system for robot laser welding, that can handle double-curved geometries. The data acquisition system includes a CMOS camera, which is mounted such that it looks through the laser optics, external LED illumination and matching optical filters. During the process, the area around the moving laser focal point is captured, resulting in a sequence of images. The trajectory of the focal point is determined by estimating the 2D displacement field between each image using template matching and subsequently filtering the data through a Kalman filter to improve the accuracy and robustness of the system. The joint location is determined by applying a Canny edge detector and a standard Hough transform within a specified region of interest. As this paper deals with double-curved geometries, the region of interest is moved in relation to the laser trajectory, such that it always contains the visible part of the joint, that is closest to the focal point. The developed post-inspection system evaluates the quality of the weld by comparing the estimated trajectory relative to the determined location of the joint. The performance of the proposed quality inspection system was validated empirically on 18 samples. The tests showed promising results, as the system was able to accurately detect changes in the welding trajectory relative to the location of the joint with an accuracy of ± 0.2 mm.

Original languageEnglish
JournalProcedia Manufacturing
Volume36
Pages (from-to)50-57
Number of pages8
ISSN2351-9789
DOIs
Publication statusPublished - 26 Aug 2019
Event17th Nordic Laser Materials Processing Conference, NOLAMP17 - Trondheim, Norway
Duration: 27 Aug 201929 Aug 2019

Conference

Conference17th Nordic Laser Materials Processing Conference, NOLAMP17
CountryNorway
CityTrondheim
Period27/08/201929/08/2019

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Laser beam welding
Robotics
Inspection
Trajectories
Geometry
Welds
Lasers
Laser optics
Template matching
Hough transforms
Optical filters
Process monitoring
Robustness (control systems)
Kalman filters
Light emitting diodes
Data acquisition
Welding
Lighting
Cameras
Robots

Keywords

  • Image processing
  • Laser welding
  • Quality inspection
  • Vision system
  • Welding trajectory

Cite this

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title = "Quality Inspection System for Robotic Laser Welding of Double-Curved Geometries",
abstract = "The quality of robotic laser welded parts is related to the joint location, the trajectory of the laser focal point and the process parameters. By performing in-process monitoring, it is possible to acquire sufficient process knowledge for post-inspection to evaluate the geometrical weld quality. The existing solutions for such systems operate along linear welds. This paper contributes with a quality inspection system for robot laser welding, that can handle double-curved geometries. The data acquisition system includes a CMOS camera, which is mounted such that it looks through the laser optics, external LED illumination and matching optical filters. During the process, the area around the moving laser focal point is captured, resulting in a sequence of images. The trajectory of the focal point is determined by estimating the 2D displacement field between each image using template matching and subsequently filtering the data through a Kalman filter to improve the accuracy and robustness of the system. The joint location is determined by applying a Canny edge detector and a standard Hough transform within a specified region of interest. As this paper deals with double-curved geometries, the region of interest is moved in relation to the laser trajectory, such that it always contains the visible part of the joint, that is closest to the focal point. The developed post-inspection system evaluates the quality of the weld by comparing the estimated trajectory relative to the determined location of the joint. The performance of the proposed quality inspection system was validated empirically on 18 samples. The tests showed promising results, as the system was able to accurately detect changes in the welding trajectory relative to the location of the joint with an accuracy of ± 0.2 mm.",
keywords = "Image processing, Laser welding, Quality inspection, Vision system, Welding trajectory",
author = "Mikkelstrup, {Anders Faarb{\ae}k} and Mathias Thomsen and Kristoffer Stampe and Endelt, {Benny {\O}rtoft} and Jens Boll and Ewa Kristiansen and Morten Kristiansen",
year = "2019",
month = "8",
day = "26",
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language = "English",
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pages = "50--57",
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issn = "2351-9789",
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}

Quality Inspection System for Robotic Laser Welding of Double-Curved Geometries. / Mikkelstrup, Anders Faarbæk; Thomsen, Mathias ; Stampe, Kristoffer; Endelt, Benny Ørtoft; Boll, Jens; Kristiansen, Ewa; Kristiansen, Morten.

In: Procedia Manufacturing, Vol. 36, 26.08.2019, p. 50-57.

Research output: Contribution to journalConference article in JournalResearchpeer-review

TY - GEN

T1 - Quality Inspection System for Robotic Laser Welding of Double-Curved Geometries

AU - Mikkelstrup, Anders Faarbæk

AU - Thomsen, Mathias

AU - Stampe, Kristoffer

AU - Endelt, Benny Ørtoft

AU - Boll, Jens

AU - Kristiansen, Ewa

AU - Kristiansen, Morten

PY - 2019/8/26

Y1 - 2019/8/26

N2 - The quality of robotic laser welded parts is related to the joint location, the trajectory of the laser focal point and the process parameters. By performing in-process monitoring, it is possible to acquire sufficient process knowledge for post-inspection to evaluate the geometrical weld quality. The existing solutions for such systems operate along linear welds. This paper contributes with a quality inspection system for robot laser welding, that can handle double-curved geometries. The data acquisition system includes a CMOS camera, which is mounted such that it looks through the laser optics, external LED illumination and matching optical filters. During the process, the area around the moving laser focal point is captured, resulting in a sequence of images. The trajectory of the focal point is determined by estimating the 2D displacement field between each image using template matching and subsequently filtering the data through a Kalman filter to improve the accuracy and robustness of the system. The joint location is determined by applying a Canny edge detector and a standard Hough transform within a specified region of interest. As this paper deals with double-curved geometries, the region of interest is moved in relation to the laser trajectory, such that it always contains the visible part of the joint, that is closest to the focal point. The developed post-inspection system evaluates the quality of the weld by comparing the estimated trajectory relative to the determined location of the joint. The performance of the proposed quality inspection system was validated empirically on 18 samples. The tests showed promising results, as the system was able to accurately detect changes in the welding trajectory relative to the location of the joint with an accuracy of ± 0.2 mm.

AB - The quality of robotic laser welded parts is related to the joint location, the trajectory of the laser focal point and the process parameters. By performing in-process monitoring, it is possible to acquire sufficient process knowledge for post-inspection to evaluate the geometrical weld quality. The existing solutions for such systems operate along linear welds. This paper contributes with a quality inspection system for robot laser welding, that can handle double-curved geometries. The data acquisition system includes a CMOS camera, which is mounted such that it looks through the laser optics, external LED illumination and matching optical filters. During the process, the area around the moving laser focal point is captured, resulting in a sequence of images. The trajectory of the focal point is determined by estimating the 2D displacement field between each image using template matching and subsequently filtering the data through a Kalman filter to improve the accuracy and robustness of the system. The joint location is determined by applying a Canny edge detector and a standard Hough transform within a specified region of interest. As this paper deals with double-curved geometries, the region of interest is moved in relation to the laser trajectory, such that it always contains the visible part of the joint, that is closest to the focal point. The developed post-inspection system evaluates the quality of the weld by comparing the estimated trajectory relative to the determined location of the joint. The performance of the proposed quality inspection system was validated empirically on 18 samples. The tests showed promising results, as the system was able to accurately detect changes in the welding trajectory relative to the location of the joint with an accuracy of ± 0.2 mm.

KW - Image processing

KW - Laser welding

KW - Quality inspection

KW - Vision system

KW - Welding trajectory

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DO - 10.1016/j.promfg.2019.08.008

M3 - Conference article in Journal

VL - 36

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EP - 57

JO - Procedia Manufacturing

JF - Procedia Manufacturing

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ER -