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EP-4739978-A1 - MEASURING SYSTEM AND METHOD FOR DETECTING FLATNESS DEFECTS ON METAL STRIPS

EP4739978A1EP 4739978 A1EP4739978 A1EP 4739978A1EP-4739978-A1

Abstract

The invention relates to a measuring system for detecting flatness defects on a rolled metal strip, having a linear light source which is arranged laterally adjacent to the metal strip and is positioned such that the light source projects a light strip onto one surface of the metal strip. The measuring system additionally has a camera which is arranged laterally adjacent to the metal strip and is positioned such that light of the light strip reflected by the surface of the metal strip is detected. The light source and the camera face opposite faces of the metal strip. In a coordinate system in which the Z coordinate axis describes the normal direction that runs perpendicularly to the surface of the metal strip, the X coordinate axis points in the metal strip running direction, the Y coordinate axis points in the transverse direction of the metal strip, and the linear light source has a lower end point with the coordinates (x 1 ,y 1 ,z 1 ) and an upper end point with the coordinates (x 2 ,y 2 ,z 2 ), wherein the light source is oriented such that x 1 ≠ x 2 .

Inventors

  • SCHAUSBERGER, Florian
  • RITTENSCHOBER, Christian
  • HABERL, Alexander
  • SCHICKMAIR, Leonhard
  • SIMKOVICS, Markus

Assignees

  • voestalpine Stahl GmbH

Dates

Publication Date
20260513
Application Date
20240705

Claims (20)

  1. 1. A measuring system for detecting flatness defects on a rolled metal strip, the measuring system comprising: a line-shaped illumination source arranged laterally next to the metal strip and positioned to project a strip of light onto a surface of the metal strip; and a camera arranged laterally next to the metal strip and positioned to detect reflected light of the strip of light from the surface of the metal strip, the illumination source and the camera facing opposite sides of the metal strip such that a light beam running from the illumination source to the camera crosses the metal strip over its entire width, wherein in a coordinate system in which the Z coordinate axis designates a normal direction running perpendicular to the surface of the metal strip, the X coordinate axis points in the direction of travel of the metal strip and the Y coordinate axis points in the transverse direction of the metal strip, the line-shaped illumination source has a lower end point with the coordinates z 2 ) and an upper end point with the coordinates (x 2 ,y2,z 2 ) and is oriented so that x 2 x 2 is.
  2. 2. Measuring system according to claim 1, wherein the linear illumination source is oriented to the metal strip such that the light strip runs obliquely to the transverse direction of the metal strip.
  3. 3. Measuring system according to claim 2, wherein the light strip runs at an angle a with respect to the transverse direction of the metal strip, which is between 30° and 60°, in particular 40° and 50°.
  4. 4. Measuring system according to one of the preceding claims, wherein 180° Ax Ax = | x 2 - x 2 1 , Az = z 2 - z 2 and an angle ß x = — arctan(— ) is between 5° and 25°, in particular 8° and 15°.
  5. 5. Measuring system according to one of the preceding claims, wherein 180° Ay Ay = y 2 - yi, Az = z 2 - z 2 and an angle ß y = - arctan(— ) is greater than 0°.
  6. 6. Measuring system according to claim 5, wherein the angle ß y is between 1° and 10°, in particular 2° and 6°.
  7. 7. Measuring system according to one of the preceding claims, which is designed to detect longitudinal folds of the metal strip inline during a manufacturing process of the metal strip.
  8. 8. Measuring system according to one of the preceding claims, wherein the camera outputs a signal which assigns brightness values of the reflected light to an image of the surface of the metal strip.
  9. 9. Measuring system according to one of the preceding claims, wherein a distance between the illumination source and the side of the metal strip facing the illumination source in a transverse direction of the metal strip is at least 0.3 m, in particular 0.5 m or 1 m.
  10. 10. Measuring system according to one of the preceding claims, wherein a distance between the camera and the side of the metal strip facing the camera in a transverse direction of the metal strip is at least 0.3 m, in particular 0.5 m or 1 m.
  11. 11. Measuring system according to one of the preceding claims, wherein the camera is equipped with a tilt-shift lens.
  12. 12. Measuring system according to one of the preceding claims, further comprising: an evaluation device having an input that can be coupled to a signal output by the camera, wherein the evaluation device is designed to calculate a measure of the flatness defect.
  13. 13. Measuring system according to claim 12, wherein the signal output by the camera assigns brightness values of the reflection light to an image of the surface of the metal strip, and the evaluation device comprises: a first calculation means which is designed to calculate a line profile of the reflection light depending on the signal output by the camera.
  14. 14. Measuring system according to claim 13, wherein the evaluation device further comprises: a second calculation means which is designed to calculate a height profile of the surface of the metal strip along a transverse direction of the metal strip as a function of the line course of the reflected light.
  15. 15. Measuring system according to claim 14, wherein the evaluation device further comprises: a third calculation means which is designed to calculate the measure of the flatness defect depending on the height profile of the surface of the metal strip.
  16. 16. A method for detecting flatness defects on a rolled metal strip, the method comprising: Illuminating a surface of the metal strip with a line-shaped illumination source which is arranged laterally next to the metal strip and positioned such that it projects a strip of light onto the surface of the metal strip; and capturing reflected light of the strip of light from the surface of the metal strip by means of a camera which is arranged laterally next to the metal strip; wherein the illumination source and the camera face opposite sides of the metal strip, wherein in a coordinate system in which the Z-coordinate axis designates a normal direction which runs perpendicular to the surface of the metal strip, the X-coordinate axis points in the direction of travel of the metal strip and the Y-coordinate axis points in the transverse direction of the metal strip, the line-shaped illumination source has a lower end point with the coordinates z 2 ) and an upper endpoint with coordinates (x 2 , y2 , z 2 ) and is oriented such that x 2 V x 2 .
  17. 17. The method of claim 16, further comprising: Evaluating a signal output by the camera to calculate a measure of the flatness defect.
  18. 18. A method according to claim 17, wherein the signal output by the camera assigns brightness values of the reflected light to an image of the surface of the metal strip, the method further comprising: Calculating a line path of the reflected light depending on the signal output by the camera.
  19. 19. The method of claim 18, further comprising: Calculating a height profile of the surface of the metal strip along a transverse direction of the metal strip as a function of the line path of the reflected light.
  20. 20. The method of claim 19, further comprising: Calculating the degree of flatness defect depending on the height profile of the surface of the metal strip.

Description

MEASURING SYSTEM AND METHOD FOR DETECTING FLATNESS DEFECTS ON METAL STRIPS The invention relates to the detection of flatness defects on a rolled metal strip. During the production of metal strips, flatness defects such as longitudinal wrinkles can occur, which can significantly complicate further processing of the metal strip or lead to rejects (metal scrap). The problem is that the occurrence of flatness defects in the manufacturing process of metal strips is subject to strong and sometimes unpredictable fluctuations depending on the process parameters. For example, it is possible that a slight change in process parameters can lead to a sudden increase in flatness defects. In general, the risk of flatness defects increasing with increasing strip speed. Since metal strips should be produced at the highest possible strip speed for cost reasons, the metrological detection of flatness defects during the manufacturing process is of great importance in practice. It is desirable to provide a suitable (quantitative) measure for the severity of flatness defects in order to be able to intervene in them early and in a targeted manner (i.e., inline if possible) during the manufacturing process. A measuring system for detecting flatness defects in the production process is exposed to adverse environmental conditions (e.g. vibrations, etc.). In addition, damage of the measuring system in the event of faults (for example, tape breaks near the measurement). It is therefore desirable to create a robust measuring system whose risk of damage is as low as possible. JP 2010-117322 A describes a surface defect detection on a steel strip, in which a light strip is projected onto the steel strip and an image of the light strip is detected by means of a camera arranged obliquely above the steel strip. JP 2004354235 A describes a camera system for detecting folds in a stainless steel strap, whereby the camera system is located almost vertically above the stainless steel strap. JP 2000121574 A describes a surface defect detection on steel strips, which uses a linear light source arranged obliquely to the strip path. One object underlying the invention can be seen in the creation of a measuring system for detecting flatness defects on a rolled metal strip, which can withstand adverse environmental conditions in the production process and in which the risk of damage to the measuring system, e.g. in the event of disruptions in the production process, is as low as possible. A further object of the invention may be to provide a meaningful measure for the extent of flatness defects on a rolled metal strip. Furthermore, the invention aims to provide a method for detecting flatness defects on a rolled metal strip which has one or more of the above-mentioned properties. The problem underlying the invention is solved by the features of the independent claims. Examples of embodiments and further developments are the subject of the dependent claims. Accordingly, a measuring system for detecting flatness defects on a rolled metal strip has a linear illumination source which is arranged laterally next to the metal strip and is positioned such that it projects a strip of light onto a surface of the metal strip. The measuring system also has a camera which is arranged laterally next to the metal strip and is positioned such that it detects the reflected light of the strip of light from the surface of the metal strip. The illumination source and the camera face opposite sides of the metal strip. In a coordinate system in which the Z-coordinate axis designates a normal direction that runs perpendicular to the surface of the metal strip, the X-coordinate axis points in the direction of travel of the metal strip and the Y-coordinate axis points in the transverse direction of the metal strip, the linear illumination source has a lower end point with the coordinates (x^ y^ Z! ) and an upper end point with the coordinates (x 2 , y2 , z 2 ), whereby the illumination source is oriented such that x 2 x 2 is . By positioning the lighting source and the camera to the side of the metal strip, the measuring system is effectively protected from damage that can occur in the event of a disruption in the production process (production process of the metal strip). In particular, if a strip breaks, the areas to the side of the metal strip are much safer than areas above or below the metal strip. Furthermore, it has been shown that the sensitivity of the measurement can be strongly influenced and in particular increased by an inclination of the linear illumination source according to Xi x 2 . 180° Ax The angle of inclination can be expressed by the angle ß x = arctan(— ), where Ax = | x 2 - x 2 1 and Az = z 2 - z 2 . For example, it has been shown that the sensitivity of the measurement is particularly high when the angle ß x is between 5 ° and 25 °, in particular 8 ° and 15 °. In order to provide the best possible protection against damage to the measuring system