Metal strip shape detection device, rolling mill, and detection method

Abstract

Even when vibrations are occurring in the metal strip, the change in the strip's elongation distribution can be evaluated with high accuracy. [Solution] In the acquired image, the distance traveled in the rolling direction by the upstream and downstream pixel points constituting the upstream boundary of the reflected light region is determined, and the reflected light region is divided into j sections in the plate width direction to form divided regions. For each divided region, the average travel speed, the number of sign reversals, and the fluctuation frequency are determined, and the average value of the fluctuation frequency of the upstream pixel point and the fluctuation frequency of the downstream pixel point is used as information corresponding to the average fluctuation frequency of the upstream and downstream pixel points of the reflected light region, and this corresponds to the position of the center of the divided region i in the plate width direction. When the value indicating the position in the plate width direction is taken as a variable x, the position in the plate width direction within the plate width range of the region in the image is normalized to the range -1≦x≦1, and the value of the information is used as an index corresponding to the rolled plate elongation distribution in the plate width direction obtained from the (k)th image, and its coefficient is determined by applying it to a Chebyshev polynomial, and the coefficient C1' of the first term is transmitted as the detection result signal of the rolled plate elongation distribution of the first component in the plate width direction of the (k)th image.

Description

[Technical Field]

[0001] The present invention relates to a metal strip shape detection device, a rolling mill, and a detection method. [Background technology]

[0002] Patent Document 1 describes a defect detection device and defect detection method that can easily determine defects in the surface shape of a metal strip without using a special light source such as a rod, comprising: a roll with a rotating shaft extending in the width direction of the rolled steel sheet and lifting the rolled steel sheet upward; a camera that captures an image including the lifted area of ​​the rolled steel sheet lifted upward by the roll; and a control device that determines defects in the surface shape of the metal strip based on the image captured by the camera.

[0003] Patent Document 2 describes a metal strip shape determination device, rolling mill, and determination method that are less susceptible to the effects of slight disturbances and suddenly occurring small obstacles compared to conventional devices, comprising a camera set up to capture an image that includes a region in which a strip-shaped reflected light transverses the width direction of the rolled metal strip is reflected, and an image processing computer that determines the shape of the metal strip based on the image captured by the camera. The image processing computer divides the region in the image into multiple sections in the width direction of the metal strip, and transmits information as a signal corresponding to the distribution of elongation in the width direction of the metal strip in the rolling direction, based on index information representing the size related to each divided area. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6808888 [Patent Document 2] Patent No. 7130350 [Overview of the project] [Problems that the invention aims to solve]

[0005] Numerous techniques have been known to detect the quality of the shape of a metal strip rolled by a rolling mill, such as whether or not there is any elongation, based on long linear or rod-shaped reflected light in the width direction of the metal strip.

[0006] The detection method is based on the fact that when some stretching occurs and the plate shape changes, the shape of the reflected light, which was linear or rod-shaped, becomes irregular, and some of it moves or displaces.

[0007] However, linear or rod-shaped lighting has the drawback that the area of ​​reflected light in the rolling direction at each position in the width direction of the plate surface is narrow, making it highly susceptible to the effects of even slight disturbances, such as small obstacles, and prone to false detections.

[0008] The inventors of the present invention have discovered that by detecting changes in the band-shaped reflected light region projected onto the surface of a metal strip near the curved portion of a strip lifted by a tension control looper installed between the rolling mill stands of a rolling mill line, using general lighting as disclosed in Patent Document 1, the influence of external disturbances can be reduced. As a technique that makes better use of the characteristics of the band-shaped reflected light region, they conceived the technique disclosed in Patent Document 2.

[0009] In the technology described in Patent Document 2, the length and area of ​​a band-shaped reflected light region projected onto the surface of a metal strip near the curved portion of the strip, which is lifted by a tension control looper installed between the rolling mill stands of a rolling line, are applied to a Chebyshev polynomial to determine the coefficients of the Chebyshev polynomial and to make a determination about the strip elongation distribution in the strip width direction.

[0010] In actual rolling operations, the metal strip may vibrate in the looper section, and the position, length in the rolling direction, and area of ​​the reflected light region projected onto the surface of the rolling metal strip are constantly fluctuating. This phenomenon can be observed where the reflected light region does not remain stably in the same position.

[0011] As a result of the present inventors' diligent studies on the technology described in Patent Document 2, it became clear that there are cases where the technology described in Patent Document 2 cannot cope with such fluctuations in the reflected light region.

[0012] The present invention provides a metal strip shape detection device, a rolling mill, and a detection method that can evaluate changes in the elongation distribution of a metal strip with high accuracy, even when vibrations are occurring in the metal strip. [Means for solving the problem]

[0013] The present invention includes multiple means for solving the above problems, but to give one example, a rolled metal strip shape detection device comprising: a camera installed in a rolling mill to capture an image that includes a range in which a band-shaped illumination light transverse in the width direction of the strip, called a reflected light region, is reflected on the surface of a metal strip lifted by a looper; and an image processing unit that detects the shape of the metal strip based on the image captured by the camera, wherein the image processing unit numbers the acquired images as 1, 2, 3, ..., k, ..., and the (k)th In the image, the pixel position Pu(k)p (p=1~Ru, where Ru is the number of pixel points constituting the upstream boundary line of the reflected light region) in the rolling direction of the pixel points constituting the upstream boundary line of the reflected light region and the pixel position Pd(k)q (q=1~Rd, where Rd is the number of pixel points constituting the downstream boundary line of the reflected light region) in the rolling direction of the pixel points constituting the downstream boundary line of the reflected light region are determined, and the displacement distance Mu(k)p of the pixel point on the upstream boundary line in the rolling direction is calculated from the difference between the pixel position Pu(k-1)p of image number (k) and the pixel position Pu(k)p of image number (k). Calculate the difference between the pixel position Pd(k-1)q of image number (k-1) and the pixel position Pd(k)q of image number (k) to determine the rolling direction displacement Md(k)q of the pixel point on the downstream boundary line, divide the reflected light region into j sections in the plate width direction to form divided regions (i) (i=1~j), and when capturing the (k)th image, calculate the average displacement Mu(k)i of the displacement Mu(k)p of the pixel point on the upstream boundary line and the average displacement Md(k)q of the pixel point on the downstream boundary line for the pixel point within the divided region (i), and calculate the image number (k-1 The time Ts between the image acquisition time of image number (k) and the divided area (i) is determined, and for each divided area (i), the average moving velocity Vu(k)i of the pixel point on the upstream boundary line is determined from the time Ts and the average moving distance Mu(k)i, and for each divided area (i), the average moving velocity Vd(k)i of the pixel point on the downstream boundary line is determined from the time Ts and the average moving distance Md(k)i, and for each divided area (i), the number of sign reversals of the average moving velocity Vu(k)i of the pixel point on the upstream boundary line between acquiring the (k-F+1)th image and the (k)th image is determined,The number of sign reversals Nd(k)i of the average movement velocity Vd(k)i of the pixel points on the downstream boundary line is determined, the time Tf between the image acquisition time of image number (k-F+1) and image number (k) is determined, for each divided area (i), the average fluctuation frequency Qu(k)i of the pixel points constituting the upstream boundary line is determined from the time Tf and the number of sign reversals Nu(k)i, for each divided area (i), the average fluctuation frequency Qd(k)i of the pixel points constituting the downstream boundary line is determined from the time Tf and the number of sign reversals Nd(k)i, the average value of the two average fluctuation frequencies Qu(k)i and Qd(k)i is calculated for each divided area (i), and the obtained average value is ( Let Q(k)i be the information corresponding to the two average fluctuation frequencies of the pixel points constituting the upstream boundary line and the pixel points constituting the downstream boundary line of the reflected light region in the k)th image. When the value of the information Q(k)i is associated with the position of the center in the plate width direction of the divided area (i), and the value indicating the position in the plate width direction is taken as the variable (x), the position in the plate width direction within the plate width range of the reflected light region in the image is normalized to the range -1≦x≦1, and the j values ​​of Q(k)i are used as an index corresponding to the rolled plate elongation distribution in the plate width direction obtained from the (k)th image, the notation for the position in the plate width direction is changed to (x), and Q(k)i=E(xi), where E(x)= C0'+C1'×x+C2'×(2x, 2 -1) + C4' × (8x 4 -8x 2 By substituting the values ​​of x (x) and x (x) into the Chebyshev polynomial (+1) (where -1≦x≦1), the coefficients of the Chebyshev polynomial (C0', C1', C2', C4') are obtained from E(xi) which has j values ​​of x (xi), and the coefficient of the first term (C1') is transmitted as the detection result signal of the rolled sheet elongation distribution of the first component in the sheet width direction of the (k)-th image. Here, xi is the position of the center in the sheet width direction of the divided region (i) obtained by dividing the reflected light region into j sections in the sheet width direction, expressed in (x) notation. F, i, j, and k are integers. [Effects of the Invention]

[0014] According to the present invention, even when vibration occurs in the metal strip, the change in the sheet elongation distribution in rolling can be evaluated with high accuracy. Problems, configurations, and effects other than those described above will be clarified by the description of the following embodiments.

Brief Description of the Drawings

[0015] [Figure 1] The figure which shows an example of the outline of the rolling equipment provided with the sheet shape detection apparatus of the metal strip of the Example of this invention. [Figure 2] The figure which shows an example of the state where the reflected light of illumination is reflected in a substantially rectangular band shape in the sheet width direction on the surface of the metal strip in the looper part between stands during operation in the rolling equipment. [Figure 3] The figure which shows an example of the state where the reflected light of illumination is reflected in an irregular band shape in the sheet width direction on the surface of the metal strip in the looper part between stands during operation in the rolling equipment. [Figure 4] The figure in the case of (Gd = Gw) showing the definition of the leveling amount (Gd - Gw). [Figure 5] The figure in the case of (Gd > Gw) showing the definition of the leveling amount (Gd - Gw). [Figure 6] The figure which shows an example of the relationship with the rolling direction movement distance Mu(k)p when the rolling direction position Pu(k - 1)p of the pixel which constitutes the upstream side boundary line of the reflected light area moves from the (k - 1) - th image and the (k) - th image in the sheet shape detection apparatus of the metal strip of the Example. [Figure 7] The figure which shows an example of averaging the moving distance of each pixel which moved in the rolling direction with Mu(k)p from the (k - 1) - th image and the (k) - th image in the sheet shape detection apparatus of the metal strip of the Example for each divided area (i) which divided the reflected light area in the sheet width direction, and re - expressing the averaged moving distance in the rolling direction as Mu(k)i. [Figure 8] The figure which shows an example of the method of equally dividing the sheet width direction in the sheet shape detection apparatus of the metal strip of the Example. [Figure 9] The figure which shows an example of the method of unevenly dividing the sheet width direction in the sheet shape detection apparatus of the metal strip of the Example. [Figure 10]This figure shows an example of how, in the metal strip shape detection device of the embodiment, the rolling direction travel distances Mu(k)i and Md(k)i obtained for each divided area (i) of pixels constituting the upstream boundary and pixels constituting the downstream boundary of the reflected light region from the (k)th image are divided by the elapsed time Ts between the (k-1)th image and the (k)th image to obtain the average travel velocities Vu(k)i and Vd(k)i in the divided area (i) of pixels constituting the upstream boundary and pixels constituting the downstream boundary. [Figure 11] This figure shows an example of determining the number of sign reversals Nu(k)i and Nd(k)i of the average moving velocities Vu(k)i and Vd(k)i for each divided region (i) of pixels constituting the upstream boundary and downstream boundary of the reflected light region during the time Tf between the (k+F-1)th image and the (k)th image of the metal strip shape detection device of the embodiment. [Figure 12] This figure shows an example of how two average fluctuation frequencies Q(k)i are obtained from the number of sign reversals Nu(k)i and Nd(k)i for each divided region (i) obtained from the (k+F-1)th image to the (k)th image in the metal strip shape detection device of the embodiment. These two average fluctuation frequencies Q(k)i are the average fluctuation frequency Qu(k)i of pixels constituting the upstream boundary line in the rolling direction of the reflected light region and the average fluctuation frequency Qd(k)i of pixels constituting the downstream boundary line. [Figure 13] The first half of the plate shape detection flowchart for the plate shape detection device of the metal strip in the embodiment. [Figure 14] The latter half of the plate shape detection flowchart for the plate shape detection device of the metal strip in the embodiment. [Figure 15] This figure shows an example of a monitor display screen showing the 0th, 1st, 2nd, and 4th order components of the Chebyshev polynomial x in the metal strip shape detection device of the embodiment. [Modes for carrying out the invention]

[0016] Embodiments of the metal strip shape detection device, rolling mill, and detection method of the present invention will be described with reference to Figures 1 to 15. In the drawings used herein, the same or corresponding components are denoted by the same or similar reference numerals, and repeated descriptions of these components may be omitted.

[0017] First, the overall configuration of the rolling mill, including the metal strip shape detection device, will be explained using Figures 1 to 3. Figure 1 is a schematic diagram showing the configuration of the metal strip shape detection device and the rolling mill equipped therewith in this embodiment, and Figures 2 and 3 are examples of how the reflected light from the lighting is projected in a band-like pattern onto the surface of the metal strip in the looper section between the stands during operation of the rolling mill.

[0018] The rolling mill 100 used to roll the metal strip 1 shown in Figure 1 is equipped with F1 stand 10, F2 stand 20, F3 stand 30, F4 stand 40, F5 stand 50, cameras 61, 62, 63, 64, loopers 71, 72, 73, 74 for tension control, an image processing computer 80, a database 81, a control device 82, a monitor 85, and the like.

[0019] These F1 stand 10, F2 stand 20, F3 stand 30, F4 stand 40, F5 stand 50, cameras 61, 62, 63, 64, image processing computer 80, database 81, control device 82, and monitor 85 are connected by a communication line 90.

[0020] Of these, cameras 61, 62, 63, and 64, loopers 71, 72, 73, and 74, an image processing computer 80, and a database 81 constitute the metal strip plate shape detection device of the present invention.

[0021] Furthermore, the rolling mill 100 is not limited to the configuration with five rolling stands as shown in Figure 1; it is sufficient to have at least two stands.

[0022] Each of the F1 stand 10, F2 stand 20, F3 stand 30, F4 stand 40, and F5 stand 50 is equipped with an upper work roll and a lower work roll, an upper backup roll that supports the upper and lower work rolls by contacting them, a lower backup roll, and pressure cylinders 11, 21, 31, 41, 51 and load sensors 12, 22, 32, 42, 52 located above the upper backup roll. Furthermore, a six-stage configuration is possible by adding intermediate rolls between each work roll and each backup roll.

[0023] The looper 71 is a tension control roll installed between the F1 stand 10 and the F2 stand 20. The looper 71 is positioned so that the rotating shaft extends in the width direction of the metal strip 1 so that the moving metal strip 1 rests on the roll, and is installed to lift and hold the metal strip 1 upwards. The looper 71 could be biased upwards by a spring, or lifted by a hydraulic cylinder or motor drive, for example.

[0024] Similarly, a tension control looper 72 is installed between the F2 stand 20 and the F3 stand 30, a tension control looper 73 is installed between the F3 stand 30 and the F4 stand 40, and a tension control looper 74 is installed between the F4 stand 40 and the F5 stand 50.

[0025] Camera 61 is positioned to capture an image of the surface of the metal strip 1, which has been rolled and lifted and curved by the looper 71, including an area where a band of illumination light, called the reflected light area 2, is visible as reflected light that transverses the width direction of the metal strip. Preferably, when the metal strip 1 is viewed from above, camera 61 can be positioned on the outside of the metal strip 1 in the width direction. The image data captured by camera 61 is transmitted to the image processing computer 80 via the communication line 90.

[0026] It is desirable to use a high-speed camera for camera 61. The image acquisition speed can be, for example, 1,000 to 2,000,000 frames per second (FPS), but these specific upper and lower limits are merely examples and are not limited to these values. It is also desirable to use high-speed cameras for cameras 62, 63, and 64, which will be described later, similar to camera 61.

[0027] Furthermore, camera 62 is positioned to capture an image of the surface of the metal strip 1, which has been rolled and lifted by the looper 72, including an area where a band of illumination light, transverse in the width direction of the sheet, called the reflected light region 2, is visible reflected on the surface of the metal strip 1. Camera 63 is positioned to capture an image of the surface of the metal strip 1, which has been rolled and lifted by the looper 73, including an area where a band of illumination light, transverse in the width direction of the sheet, called the reflected light region 2, is visible reflected on the surface of the metal strip 1. Camera 64 is positioned to capture an image of the surface of the metal strip 1, which has been rolled and lifted by the looper 74, including an area where a band of illumination light, transverse in the width direction of the sheet, called the reflected light region 2, is visible reflected on the surface of the metal strip 1. The image data captured by cameras 62, 63, and 64 is transmitted to the image processing computer 80 via the communication line 90.

[0028] Cameras 62, 63, and 64, like camera 61, are preferably installed on the outside of the metal strip 1 in the width direction when the metal strip 1 is viewed from above.

[0029] These cameras 61, 62, 63, and 64 perform a shooting step in which they capture an image that includes a region where a band-shaped reflected light transverses the width direction of the rolled metal strip 1 is visible.

[0030] Further lighting can be provided to illuminate the lifted shooting area of ​​the metal strip 1, which is lifted upward by the roll and is primarily photographed by cameras 61, 62, 63, and 64. This lighting can be general lighting that is appropriately placed on the ceiling of the rolling mill where the rolling equipment 100 is installed, and no special new lighting equipment is required in this invention, however, dedicated lighting may be provided.

[0031] The image processing computer 80 is a device that performs various processes (including image processing steps) to detect the shape of the metal strip 1 based on images captured by cameras 61, 62, 63, and 64. Preferably, the image processing computer 80 is the main entity that performs the image processing steps.

[0032] For example, using image processing, an image including the lifted region, which is the curved vicinity of the metal strip 1 that has been rolled and lifted by loopers 71, 72, 73, and 74 as shown in Figure 2 or Figure 3, is identified as the reflected light region 2, which is the range including the upstream and downstream boundaries of the area where the brightness of the reflected light from the surface of the metal strip 1 shown in the image is greater than a specific brightness value.

[0033] Here, the visible area of ​​the strip-shaped reflected light that crosses the width direction of the metal strip 1 is small in distribution depending on how the light hits it, as shown in Figure 2, because the surface of the metal strip 1 is flat and the plate wave is small, assuming that the elongation in the rolling direction (strip longitudinal direction) at each position in the width direction of the metal strip 1 is uniform. For this reason, the boundary lines of the reflected light region 2 due to illumination are approximately uniform in distance between the upstream boundary line 2A and the downstream boundary line 2B, and the parameters such as the area value of each region and the average length in the rolling direction when the reflected light region 2 is divided into multiple regions in the width direction are approximately uniform in all regions.

[0034] In contrast, if there are differences in elongation in the rolling direction depending on the position in the width direction of the sheet (e.g., elongation at the edges, elongation in the middle), the metal strip is not flat, and the way it is illuminated differs due to the varying degrees of steepness caused by sheet waves, etc. As shown in Figure 3, the boundary lines of the reflected light region 2 due to illumination are wavy on either the upstream boundary line 2A or the downstream boundary line 2B, or both, and the distance between the upstream boundary line 2A and the downstream boundary line 2B of the reflected light region 2 becomes non-uniform. For this reason, when the reflected light region 2 of the metal strip is divided into multiple regions in the width direction, the parameters such as the area value of each region and the average length in the rolling direction will be non-uniform in each region.

[0035] In the aforementioned Patent Document 1, the Chebyshev polynomial (1) below is used as an indicator of the sheet elongation distribution due to rolling, using the sheet width distribution, such as the length and area in the rolling direction, of the reflected light region 2 projected onto the surface of the metal sheet 1 near the curved portion of the metal sheet 1 lifted by the loopers 71, 72, 73, and 74. Curve fitting (curve approximation) is performed using the Chebyshev polynomial (1) below.

[0036] E(x) = C0' + C1' × x + C2' × (2x 2 -1) + C4' × (8x 4 -8x 2 +1) (where -1 ≤ x ≤ 1) ··· (1) In the Chebyshev polynomial, for example, as an index of the sheet elongation distribution in the width direction due to rolling, E(x) is assumed to represent the length in the rolling direction of the reflected light region 2 on the surface of the metal strip 1 at loopers 71, 72, 73, and 74, as well as the magnitude corresponding to the sheet elongation due to rolling. C0', C1', C2', and C4' represent the values ​​of the coefficients when the Chebyshev polynomial, which is assumed to represent the magnitude corresponding to the sheet elongation distribution in the width direction, is separated into its 0th, 1st, 2nd, and 4th order components of x. x represents the normalized position in the width direction of the sheet; for example, x=-1 represents the sheet width end position on the drive side (DS), and x=1 represents the sheet width end position on the work side (WS). In other words, in this case, if the coefficient of the linear component of x in the Chebyshev polynomial (C1') is positive, it indicates that the plate elongation is large on the working side (WS). Also, if the coefficient of the quadratic component of x (C2') is positive, it indicates that the elongation at the edges of the plate width is greater than at the center of the plate width. Furthermore, if the coefficient of the quartic component of x (C4') is negative, it indicates that the quarter elongation in the plate width direction is large.

[0037] The definition of leveling amount is shown below.

[0038] As shown in Figures 4 and 5, the leveling amount is defined as the value obtained by subtracting the distance between the upper and lower work roll axes at the work side (WS) position from the distance between the upper and lower work roll axes Gd at the drive side (DS) position of the reduction cylinder (WS).

[0039] When changing the leveling amount, the plate thickness at the center of the plate width should not be changed. Therefore, as shown in Figure 5, when the leveling amount increases compared to the state shown in Figure 4, the plate thickness on the drive side (DS) becomes thicker, the plate thickness on the work side (WS) becomes thinner, and the plate elongation on the work side (WS) increases. The value of the Chebyshev first-order component (C1') obtained by this method indicates that if the value is positive, the plate elongation on the work side (WS) is large, and if the value is negative, the plate elongation on the drive side (DS) is large.

[0040] In this embodiment, the image processing computer 80 performs the following five analysis processes on each acquired image.

[0041] The first analysis process performed by the image processing computer 80, as shown in Figure 6, involves numbering the acquired images 1, 2, 3, ..., k, ..., and for the (k)th image, determining the pixel position Pu(k)p in the rolling direction of the upstream pixel point constituting the upstream boundary line 2A of the reflected light region 2 (p=1~Ru, where Ru is the number of pixels constituting the upstream boundary line 2A of the reflected light region 2), and, although not shown in Figure 6, the pixel position Pd(k)q in the rolling direction of the downstream pixel point constituting the downstream boundary line 2B of the reflected light region 2 (q=1~Rd, where Rd is the number of pixels constituting the downstream boundary line 2B of the reflected light region 2). This data is preferably stored in the database 81.

[0042] Here, as described above, the boundary line of the reflected light region 2 fluctuates during rolling. Therefore, in this embodiment, as the second analysis process performed by the image processing computer 80, the distance Mu(k)p (=Pu(k)p-Pu(k-1)p) in the rolling direction of the pixel point on the upstream boundary line 2A of the reflected light region 2 is determined from the pixel position Pu(k-1)p of image number (k) and the pixel position Pu(k)p of image number (k) stored in the database 81, as shown in Figure 6. In addition, although not shown in Figure 6, the distance Md(k)q (=Pd(k)q-Pd(k-1)q) in the rolling direction of the pixel point on the downstream boundary line 2B of the reflected light region 2 is determined from the pixel position Pd(k-1)q of image number (k) and the pixel position Pd(k)q of image number (k).

[0043] Furthermore, the second analysis process performed by the image processing computer 80, as shown in Figure 7, reconsiders the rolling direction travel distance Mu(k)p of pixel points on the upstream boundary line 2A of the reflected light region 2 within the range of divided areas (i) (i=1~j) obtained by dividing the reflected light region 2 into j sections in the plate width direction. The average value of the rolling direction travel distance Mu(k)p of pixel points on the upstream boundary line 2A that exist within the range of divided area (i) is calculated and taken as the average travel distance Mu(k)i for pixel points constituting the upstream boundary line 2A of the reflected light region 2 in divided area (i). Similarly, although not shown in Figure 7, the average value of Md(k)q of the rolling direction travel distance Md(k)q of pixel points on the downstream boundary line 2B that exist within the range of divided area (i) is calculated and taken as the average travel distance Md(k)i for pixel points constituting the downstream boundary line 2B of the reflected light region 2 in divided area (i).

[0044] Furthermore, as for the method of dividing the reflected light region 2, each divided region (i) (i=1~j) divided in the plate width direction may be equally divided into j equal widths as shown in Figure 8, or each of the j may be unequally divided into arbitrary widths as shown in Figure 9.

[0045] Next, the third analysis process performed by the image processing computer 80, as shown in Figure 10, involves dividing the average movement distance Mu(k)i of the pixel points constituting the upstream boundary line 2A of the reflected light region 2 in each divided area (i) obtained by dividing the reflected light region 2 into j sections in the plate width direction, and the average movement distance Md(k)i of the pixel points constituting the downstream boundary line 2B of the reflected light region 2 in each divided area (i), by the time Ts required from the acquisition of the (k-1)th image to the acquisition of the (k)th image. This calculates the average movement velocity Vu(k)i (=Mu(k)i / Ts) of the pixel points constituting the upstream boundary line 2A for each divided area (i) of the reflected light region 2, and the average movement velocity Vd(k)i (=Md(k)i / Ts) of the pixel points constituting the downstream boundary line 2B.

[0046] Next, the fourth analysis process performed by the image processing computer 80, as shown in Figure 11, examines how many times the positive / negative signs (+ / -) of the average movement velocity Vu(k)i of the pixel points constituting the upstream boundary line 2A and the average movement velocity Vd(k)i of the pixel points constituting the downstream boundary line 2B were reversed during the time Tf required from the acquisition of the (k-F+1)th image to the acquisition of the (k)th image. This allows the computer to determine the number of sign reversals Nu(k)i for the average movement velocity Vu(k)i of the pixel points constituting the upstream boundary line 2A of the reflected light region 2 in the divided area (i), and the number of sign reversals Nd(k)i for the average movement velocity Vd(k)i of the pixel points constituting the downstream boundary line 2B of the reflected light region 2.

[0047] Subsequently, the fifth analysis process performed by the image processing computer 80, as shown in Figure 12, calculates the average fluctuation frequency Qu(k)i (=[Nu(k)i / Tf] / 2) of the pixel points constituting the upstream boundary line 2A of the reflected light region 2 and the average fluctuation frequency Qd(k)i (=[Nd(k)i / Tf] / 2) of the pixel points constituting the downstream boundary line 2B from the sign inversion counts Nu(k)i and Nd(k)i. Furthermore, it calculates Q(k)i (=[Qu(k)i+Qd(k)i] / 2) as the average fluctuation frequency of the pixel points constituting the upstream and downstream boundary lines (2A,2B) that form the reflected light region 2 for each divided area (i).

[0048] Furthermore, as a continuation of the fifth analysis process performed by the image processing computer 80, the value of the obtained information Q(k)i is used as an index corresponding to the elongation of the rolled plate in the (k)th image, and the value indicating the position in the plate width direction is taken as the variable (x). The position in the plate width direction within the plate width range is normalized to the range -1 ≤ x ≤ 1, and the central position of each divided area (i) in the plate width direction is associated with xi. Q(k)i is then set to the Chebyshev polynomial E(xi) = Q(k)i of equation (1) at the time of the (k)th image.

[0049] Then, the j values ​​of E(xi) (i.e., E(xi)=Q(k)i) obtained at the central position xi of each divided region (i) (i=1~j) in the plate width direction of the reflected light region 2 of the (k)-th image are applied to the Chebyshev polynomial of equation (1) for each divided region (i), and curve fitting is performed using the least squares method. From the equation of the approximate curve, the coefficients of the Chebyshev polynomial (C0', C1', C2', C4') are determined, and the linear coefficient (C1') is transmitted as the detection result signal of the linear component of the rolled plate elongation distribution in the plate width direction.

[0050] Preferably, the image processing computer 80 can further transmit, in addition to the linear coefficient of x in the Chebyshev polynomial (C1'), one or more coefficients of either the quadratic coefficient of x (C2') or the quartic coefficient of x (C4') as a detection result signal of the rolled sheet elongation distribution of the quadratic or quartic components in the sheet width direction.

[0051] Database 81 also functions as a recording medium containing various parameters used when operating the rolling mill 100.

[0052] Returning to Figure 1, the control device 82 is a device that controls the operation of each piece of equipment within the rolling mill 100. In this embodiment, it is a device that performs various controls in accordance with the detection of the plate shape of the metal strip 1 by the image processing computer 80.

[0053] These image processing computers 80, databases 81, and control devices 82 can be composed of computers having monitors 85 such as liquid crystal displays, input devices, storage devices, CPUs, memory, etc., and may be composed of a single computer, or each may be composed of separate computers; there are no particular limitations.

[0054] The operation of each device is controlled by the image processing computer 80 and the control device 82 based on various programs stored in the memory. The control processes performed by the image processing computer 80 and the control device 82 may be combined into a single program, each part may be divided into multiple programs, or a combination of these. Furthermore, some or all of the programs may be implemented in dedicated hardware or may be modularized.

[0055] The monitor 85 is a display device such as a screen or an audio device such as an alarm. For example, when the image processing computer 80 detects that there is a problem with the board shape, it is a device that informs the operator about the necessary corrective actions. Therefore, a screen is often used as such a monitor 85.

[0056] Here, the image processing computer 80 mentioned above includes a display signal unit, which transmits signals related to the content to be displayed on the monitor 85 to the control device 82 and the monitor 85.

[0057] During operation, the operator can visually check the state of the board shape by looking at the display screen of monitor 85, each stand itself, and the spaces between the stands.

[0058] Furthermore, the system is not limited to a configuration in which the operator is notified of a problem with the plate shape and the control device 82 automatically performs an operation to correct the problem with the plate shape. It can also be configured to simply display the problem on the monitor 85, or to omit the display on the monitor 85 and have only the control device 82 automatically perform an operation to correct the problem with the plate shape.

[0059] Next, the flow of the plate shape detection device and detection method for the rolled metal strip 1 in the present invention will be explained using Figures 13 and 14. Figures 13 and 14 show a flowchart of the method for calculating the average fluctuation frequency Q(k)i of the upstream and downstream boundary lines (2A, 2B) that form the reflected light region 2, which is an indicator of the present invention.

[0060] As shown in Figure 13, before or during rolling, the image processing computer 80 sets the number of images F (for example, F=1000) for determining the average fluctuation frequency of the boundary line of the reflected light region 2 (step S201), and also sets the image number k (step S202). Here, the initial value of the image number is k=1.

[0061] Subsequently, the image processing computer 80 acquires surface images (k) of the metal strip 1 near the curved portion of the metal strip 1 that has been lifted by the loopers 71, 72, 73, and 74, which were captured by the cameras 61, 62, 63, and 64 (step S203). Here, the acquired images are numbered 1, 2, 3, ..., k, ... in the order they were acquired.

[0062] Next, the image processing computer 80 processes the images (k) captured by cameras 61, 62, 63, and 64 to extract the reflected light region 2 on the surface of the metal strip 1 near the curved portion of the metal strip 1 (step S204).

[0063] For example, the image processing computer 80 performs binarization on all pixels (image pixels) in the selected rolled surface image range from the images captured by cameras 61, 62, 63, and 64 to determine an appropriate brightness threshold. This determines the pixel coordinates that constitute the upstream boundary line 2A and the downstream boundary line 2B visible in the plate width direction on the upstream and downstream sides of the reflected light region 2 projected on the surface of the metal strip, thereby identifying the reflected light region 2. The details of this process can be based on known methods.

[0064] Next, the image processing computer 80 stores the position Pu(k)p in the rolling direction of the pixel points constituting the upstream boundary line 2A of the reflected light region 2 for the image obtained as the (k)-th among the images captured by the cameras 61, 62, 63, and 64 (step S205), and also stores the position Pd(k)q in the rolling direction of the pixel position of the downstream boundary line 2B of the reflected light region 2 (step S206). Here, p is the pixel number constituting the upstream boundary line 2A, representing p = 1 to (the number of pixels Ru constituting the upstream boundary line), q is the pixel number constituting the downstream boundary line 2B, representing q = 1 to (the number of pixels Rd constituting the downstream boundary line). These steps S205 and S206 may be in any order, may be processed in parallel, or step S206 may be processed prior to step S205.

[0065] Next, the image processing computer 80 determines whether the image number k < F (step S207). When it is determined that the image number k < F, the process proceeds to step S208, where the image number k is updated (k = k + 1) (step S208), and the process proceeds to step S203, waiting for a predetermined number of images to be processed. On the other hand, when it is determined in step S207 that the image number k ≧ F, the process proceeds to step S209.

[0066] Next, the image processing computer 80 calculates the movement distance Mu(k)p (= Pu(k)p - Pu(k - 1)p) from the pixel position Pu(k - 1)p of the upstream boundary line 2A of the image number (k - 1) and the pixel position Pu(k)p of the upstream boundary line 2A of the image number (k) (step S209), and also calculates the movement distance Md(k)q (= Pd(k)q - Pd(k - 1)q) from the pixel position Pd(k - 1)q of the downstream boundary line 2B of the image number (k - 1) and the pixel position Pd(k)q of the downstream boundary line 2B of the image number (k) (step S210).

[0067] Next, the image processing computer 80 divides the reflected light region 2 extracted from the image (k) captured by the cameras 61, 62, 63, and 64 into j parts in the plate width direction (for example, j = 7) (step S211).

[0068] Next, as shown in Figure 14, the image processing computer 80 uses the movement distance Mu(k)p of the pixel point on the upstream boundary line 2A obtained in step S209 to calculate the average movement distance Mu(k)i (=average [Mu(k)p]i (i=1~j)) in each divided area (i) (i=1~j) of the reflected light region divided into j sections in the plate width direction, using the movement distance Md(k)q of the pixel point on the downstream boundary line 2B obtained in step S210 to calculate the average movement distance Md(k)i (=average [Md(k)q]i) (i=1~j) in each divided area (i) (i=1~j) of the reflected light region divided into j sections in the plate width direction (step S212).

[0069] Next, the image processing computer 80 calculates the time Ts (=T(k)-T(k-1)) between the image acquisition times T(k-1) and T(k) of image number (k) and calculates the average movement velocity Vu(k)i (=Mu(k)i / Ts) (i=1~j) (i=1~j) for each divided area (i) (i=1~j) of the reflected light region divided into j sections in the width direction of the plate, from the average movement distance Mu(k)i of the pixel point on the upstream boundary line 2A that moved during the time Ts between image number (k-1) and image number (k). It also calculates the average movement velocity Vd(k)i (=Md(k)i / Ts) (i=1~j) (i=1~j) (step S213) (step S213).

[0070] Next, the image processing computer 80 calculates the number of times the average moving velocities Vu(k)i and Vd(k)i in the rolling direction of the pixel points constituting the upstream boundary line 2A and downstream boundary line 2B in each divided area (i) (i=1~j) of the reflected light region divided into j sections in the plate width direction, have undergone sign reversals (+ / -) between the acquisition of the (k-F+1)th image and the acquisition of the (k)th image, and calculates the number of sign reversals Nu(k)i and Nd(k)i respectively (step S214).

[0071] Next, the image processing computer 80 calculates the time Tf (seconds) (=T(k)-T(k-F+1)) required from the acquisition of the (k-F+1)th image to the acquisition of the (k)th image, and calculates the average fluctuation frequency Qu(k)i (=[Nu(k)i / Tf] / 2) of the pixel points on the upstream boundary line 2A in each j-divided section (i) by dividing the number of sign reversals Nu(k)i of the average movement velocity Vu(k)i of the pixel points constituting the upstream boundary line 2A calculated in step S214 by the time Tf seconds, and then dividing by 1 / 2. At the same time, it calculates the average fluctuation frequency Qd(k)i (=[Nd(k)i / Tf] / 2) of the pixel points on the downstream boundary line 2B in each j-divided section (i) by dividing the number of sign reversals Nd(k)i of the average movement velocity Vd(k)i of the pixel points constituting the downstream boundary line 2B by dividing by the time Tf seconds, and then dividing by 1 / 2 (step S215).

[0072] Next, the image processing computer 80 calculates the average fluctuation frequency Q(k)i (=[Qu(k)i + Qd(k)i] / 2) (i=1~j) (unit: [Hz]) of the pixel points constituting the upstream boundary line 2A and the downstream boundary line 2B in each j-divided division area (i) (step S216), using the average fluctuation frequency Qu(k)i of the pixel points on the upstream boundary line 2A and the average fluctuation frequency Qd(k)i of the pixel points on the downstream boundary line 2B calculated in step S215 for the (k)-th image acquired (step S216).

[0073] Next, the image processing computer 80 re-expresses the central position in the plate width direction of each divided area (i) when the reflected light region 2 is divided in the plate width direction using the variable (x) of the plate width direction position in each divided area (i). The average fluctuation frequency Q(k)i of the two boundary lines of the reflected light region 2 in each divided area (i) obtained at the time of the camera image (k) obtained in step S216 is associated with the central position in the plate width direction of the divided area (i) to (x), and E(xi)=Q(k)i is set to E(xi)=Q(k)i. E(xi) expressed in terms of (x) is curve-fitted to the Chebyshev polynomial of equation (1), and the Chebyshev coefficients (C0', C1', C2', C4') are calculated from the obtained approximation (step S217). Note that xi represents the central position of the divided area (i) when the reflected light region 2 is divided in the plate width direction, with the plate width direction position expressed as x.

[0074] The advantages of approximating the average fluctuation frequency Q(k)i (E(xi)=Q(k)i) of the upstream and downstream boundary lines (2A,2B) that form a reflected light region 2, which is an index corresponding to the sheet elongation distribution in the rolling direction relative to the sheet width direction, with a Chebyshev polynomial are that (1) the sheet width range (x axis) is normalized to the range from -1 to +1, and (2) the first-order component (single-sided elongation), second-order component (intermediate elongation / edge elongation), and fourth-order component (quarter elongation) of x are separated, and the rolling control operation method for each component can be easily estimated.

[0075] Next, the image processing computer 80 transmits the Chebyshev coefficients (C1', C2', C4') obtained in step S213 as detection result signals of the plate elongation distribution in the (k)-th image to, for example, the control device 82 or the monitor 85 (step S218).

[0076] Subsequently, the image processing computer 80 determines whether or not rolling is continuing (step S219). If it determines that rolling is continuing, it returns to step S208, updates the image number (k) to (k=k+1), and continues the plate shape detection process. If it determines that rolling is complete, it terminates the process.

[0077] In this embodiment, a cubic component is not used in the Chebyshev polynomial. This is because the rolling control mechanism of the rolling mill is not designed to handle sheet elongation correction for the cubic component. By omitting the calculation processing and handling means for the cubic component, it becomes easier to judge the condition of the rolled sheet shape and correct sheet elongation for the separated primary, quaternary, and quartic components.

[0078] The image processing computer 80 can output a control command signal to the control device 82 to correct the leveling, bending force, pair crossing angle, etc. based on the polynomial approximation result in the sheet width direction obtained using the Chebyshev polynomial of equation (1). Further, alternatively, or in addition, by outputting a display command signal for performing guidance display necessary for correcting the leveling, bending force, pair crossing angle, etc. to the monitor 85, the operator can be informed of correction information such as the leveling, bending force, pair crossing angle, etc.

[0079] Preferably, the image processing computer 80 is the 0th order component [C0'] of x of the function of each order term vector (C0', C1', C2', C4') in the above-mentioned E(x), the 1st order component [C1'×x] of x, the 2nd order component [C2'×(2x 2 -1)] of x, and the 4th order component [C4'×(8x 4 -8x 2 +1)] of x, and can send a signal to the monitor 85 to display the graph of each component term. The screen displayed on the monitor 85 is, for example, a screen as shown in FIG. 15.

[0080] FIG. 15 is a diagram showing an example of the display screen of the monitor 85. In FIG. 15, examples of the distribution displays of the 0th order, 1st order, 2nd order, and 4th order components of x of the Chebyshev polynomial are shown at the sheet width direction positions (-1≦x≦1) within the sheet width. The operator can check the display screen of the monitor 85 shown in this FIG. 15 and perform operations to correct, for example, the leveling, bending force, pair crossing angle (in the case of a pair crossing rolling mill), etc.

[0081] Among the Chebyshev polynomial coefficients, the coefficient (C1') of the 1st order component of x indicates an index of unilateral elongation. Therefore, the leveling of the backup rolls 41 on the driving side (DS) and the working side (WS) on the upstream side of the corresponding camera 64, and / or the backup rolls 51 on the driving side (DS) and the working side (WS) on the downstream side is operated, and an operation command signal is output to the control device 82 to normalize the 1st order component (within the target range).

[0082] The coefficient of the quadratic component of x in the Chebyshev polynomial coefficients (C2') indicates an indicator of edge elongation or mid-roll elongation. Therefore, one or more of the following operations are performed: an operation command signal is output to the control device 82 to operate the bending device of the work roll / intermediate roll of the F4 stand 40, which is the upstream rolling mill, and / or the F5 stand 50, which is the downstream rolling mill, or to operate the pair cross angle in the case of a pair cross rolling mill, or, in the case of a work roll shift / intermediate roll shift rolling mill, to predict mid-roll elongation / edge elongation in advance and shift the work roll / intermediate roll in advance because it is difficult to shift during rolling, thereby normalizing the quadratic component (to within the target range).

[0083] The coefficient of the fourth-order component of x in the Chebyshev polynomial coefficients (C4') indicates an indicator of quarter elongation. Therefore, in order to correct quarter elongation, one or more of the following operations are performed: The bending operation is performed on the work roll bending device of the F4 stand 40, which is the upstream rolling mill of the camera 64, and / or the F5 stand 50, which is the downstream rolling mill. Furthermore, in the case of a pair cross mill, the pair cross angle is operated together with the bending operation or independently. In the case of a 6-stage intermediate roll shift rolling mill, the quarter elongation is predicted in advance and the intermediate rolls are shifted to the appropriate position. By outputting operation command signals to the control device 82 to perform the bending operation and pair cross angle operation, the fourth-order component indicating quarter elongation is normalized (to within the target range so that the target plate shape is achieved). Note that quarter elongation is more likely to occur when the roll diameter is small relative to the roll length, as the roll is more likely to bend in the region of the roll width end due to the bending operation, but this can be normalized by the above operations.

[0084] Next, the effects of this embodiment will be described.

[0085] In the metal strip 1 plate shape detection device in the rolling mill of the above-described embodiment, the image processing computer 80 numbers the acquired images as 1, 2, 3, ..., k, ... in the order they are acquired, and in the (k)th image, the pixel position Pu(k)p (p=1~Ru, where Ru is the number of pixel points constituting the upstream boundary line 2A of the reflected light region 2) in the rolling direction of the pixel points constituting the downstream boundary line 2B of the reflected light region 2) and the pixel position Pd(k)q (q=1~Rd, where R is the number of pixel points constituting the upstream boundary line 2A of the reflected light region 2) in the rolling direction of the pixel points constituting the downstream boundary line 2B of the reflected light region 2 d is the number of pixel points that make up the downstream boundary line 2B of the reflected light region 2), and the distance Mu(k)p (=Pu(k)p-Pu(k-1)p) of the movement of the pixel point on the upstream boundary line 2A in the rolling direction is calculated from the difference between the pixel position Pu(k-1)p of image number (k) and the pixel position Pu(k)p of image number (k), and the distance Md(k)q (=Pd(k)q-Pd(k-1)q) of the pixel point on the downstream boundary line 2B in the rolling direction is calculated from the difference between the pixel position Pd(k-1)q of image number (k) and the pixel position Pd(k)q of image number (k), and the reflected light region 2 is measured in the plate width direction j Divided regions (i) (i=1~j) are formed, and when the (k)th image is captured, for the pixel points within the range of region (i), the average movement distance Mu(k)i of the pixel points on the upstream boundary line 2A (Mu(k)p) and the average movement distance Md(k)i of the pixel points on the downstream boundary line 2B (Md(k)q) are calculated, the time Ts between the image acquisition time of image number (k-1) and image number (k) is calculated, and for each region (i), the average movement velocity Vu(k)i of the pixel points on the upstream boundary line 2A is calculated from the time Ts and the average movement distance Mu(k)i, and For each divided area (i), calculate the average movement velocity Vd(k)i of the pixel points on the downstream boundary line 2B from time Ts and average movement distance Md(k)i. For each divided area (i), calculate the number of sign reversals Nu(k)i of the average movement velocity Vu(k)i of the pixel points on the upstream boundary line 2A and the number of sign reversals Nd(k)i of the average movement velocity Vd(k)i of the side pixel points on the downstream boundary line 2B during the acquisition of images (k-F+1) to (k). Calculate the time Tf between the acquisition time of image number (k-F+1) and image number (k). For each divided area (i),The average fluctuation frequency Qu(k)i (=[Nu(k)i / Tf] / 2) of the pixel points constituting the upstream boundary line 2A is calculated from time Tf and the number of sign reversals Nu(k)i. For each divided area (i), the average fluctuation frequency Qd(k)i (=[Nd(k)i / Tf] / 2) of the pixel points constituting the downstream boundary line 2B is calculated from time Tf and the number of sign reversals Nd(k)i. The average values ​​of the two average fluctuation frequencies, Qu(k)i and Qd(k)i, are calculated for each divided area (i), and the obtained average values ​​are used to represent the pixel points constituting the upstream boundary line 2A and the downstream boundary line 2B of the reflected light region 2 of the (k)th image. Let Q(k)i (=[Qu(k)i+Qd(k)i] / 2) be the information corresponding to the two average fluctuation frequencies of the pixel point, and let the value of the information Q(k)i correspond to the position of the center in the plate width direction of the divided area (i). When the value indicating the position in the plate width direction is taken as the variable (x), the position in the plate width direction within the plate width range of the reflected light region 2 in the image is normalized to the range -1≦x≦1, and the j values ​​of Q(k)i are used as an index corresponding to the rolled plate elongation distribution in the plate width direction obtained from the (k)th image. The notation for the position in the plate width direction is changed to (x), and Q(k)i=E(xi), where E(x) = C0'+C1'×x+C2'×(2x, 2 -1) + C4' × (8x 4 -8x 2 By substituting this into the Chebyshev polynomial (+1) (where -1≦x≦1), the coefficients of the Chebyshev polynomial (C0', C1', C2', C4') are determined from E(xi) which has j values ​​of x (xi), and the coefficient of the first term (C1') is transmitted as the detection result signal of the rolled sheet elongation distribution of the first component in the sheet width direction of the (k)-th image.

[0086] This makes it possible to evaluate changes in plate elongation distribution, which could not be addressed by the aforementioned Patent Document 1, with high accuracy.

[0087] Furthermore, the image processing computer 80 transmits one or more coefficients from among the first-order coefficient (C1'), second-order coefficient (C2'), or fourth-order coefficient (C4') as detection result signals of the rolled sheet elongation distribution of the first-order, second-order, or fourth-order components in the sheet width direction, thereby enabling it to respond to a wider range of sheet shape changes.

[0088] <Other> It should be noted that the present invention is not limited to the embodiments described above, and various modifications and applications are possible. The embodiments described above are explained in detail for the purpose of clearly illustrating the present invention, and are not necessarily limited to those having all the configurations described. [Explanation of symbols]

[0089] 1...Metal strip 2...Reflected light area 2A... Upstream boundary line of the reflected light region 2B... Downstream boundary line of the reflected light region 10…F1 Stand 11, 21, 31, 41, 51… Reducing cylinders 12, 22, 32, 42, 52… Load detectors 20…F2 Stand 30…F3 Stand 40…F4 Stand 50…F5 stand 61, 62, 63, 64… Camera 71, 72, 73, 74… Looper 80…Image processing computer (image processing unit) 81…Database 82...Control device 85... Monitor 90...communication line 100...Rolling equipment

Claims

1. In a rolling mill, a camera is installed to capture an image that includes the area on the surface of a metal strip lifted by a looper, where a band of illumination light, called the reflected light region, is reflected across the width of the strip. A rolled metal strip shape detection device comprising: an image processing unit for detecting the shape of the metal strip based on the image captured by the camera, The aforementioned image processing unit, The images were numbered 1, 2, 3, ..., k, ... in the order they were acquired. In the (k)th image, determine the pixel position Pu(k)p in the rolling direction of the pixel point constituting the upstream boundary of the reflected light region (p = 1 to Ru, where Ru is the number of pixel points constituting the upstream boundary of the reflected light region) and the pixel position Pd(k)q in the rolling direction of the pixel point constituting the downstream boundary of the reflected light region (q = 1 to Rd, where Rd is the number of pixel points constituting the downstream boundary of the reflected light region). The distance Mu(k)p of the pixel point on the upstream boundary line in the rolling direction is determined from the difference between the pixel position Pu(k-1)p of image number (k) and the pixel position Pu(k)p of image number (k). The distance Md(k)q of the movement of the pixel point on the downstream boundary line in the rolling direction is determined from the difference between the pixel position Pd(k-1)q of image number (k) and the pixel position Pd(k)q of image number (k). The reflected light region is divided into j sections in the width direction of the plate to form divided regions (i) (i = 1 to j), When capturing the (k)th image, for pixel points located within the range of the divided area (i), calculate the average movement distance Mu(k)i of the pixel points on the upstream boundary line Mu(k)p and the average movement distance Md(k)i of the pixel points on the downstream boundary line Md(k)q. The time Ts between the acquisition times of image number (k-1) and image number (k) is calculated. For each of the divided areas (i), the average movement velocity Vu(k)i of the pixel point on the upstream boundary line is determined from the time Ts and the average movement distance Mu(k)i. For each of the divided areas (i), the average moving velocity Vd(k)i of the pixel point on the downstream boundary line is determined from the time Ts and the average moving distance Md(k)i. For each of the divided regions (i), the number of sign reversals of the average movement velocity Vu(k)i of the pixel points on the upstream boundary line and the number of sign reversals of the average movement velocity Vd(k)i of the pixel points on the downstream boundary line are calculated between acquiring the (k-F+1)th image and the (k)th image. The time Tf between the acquisition time of image number (k - F + 1) and image number (k) is calculated. For each of the divided areas (i), the average fluctuation frequency Qu(k)i of the pixel points constituting the upstream boundary line is determined from the time Tf and the number of sign reversals Nu(k)i. For each of the divided areas (i), the average fluctuation frequency Qd(k)i of the pixel points constituting the downstream boundary line is determined from the time Tf and the number of sign reversals Nd(k)i. The average values ​​of the average fluctuation frequency Qu(k)i and the average fluctuation frequency Qd(k)i are calculated for each divided area (i), and the obtained average value is taken as information Q(k)i corresponding to the two average fluctuation frequencies of the pixel point constituting the upstream boundary line and the pixel point constituting the downstream boundary line of the reflected light region of the (k)-th image, and the value of the information Q(k)i is assigned to the position of the center in the plate width direction of the divided area (i). When the value indicating the position in the width direction of the plate is taken as the variable (x), the position in the width direction of the plate within the plate width range of the reflected light region in the image is normalized to the range -1 ≤ x ≤ 1, and the j values ​​of Q(k)i are used as an index corresponding to the rolled plate elongation distribution in the width direction of the plate obtained from the (k)th image, the notation for the position in the width direction of the plate is changed to (x), and Q(k)i = E(xi), consisting only of 0th, 1st, 2nd, and 4th order terms of x. E(x) = C ０ '+C １ × x + C ２ '×(2x ２ -1) + C ４ '×(8x ４ -8x ２ Substituting this into the Chebyshev polynomial (+1) (where -1 ≤ x ≤ 1), we get E(xi) with j values ​​of x (xi), The coefficients (C ０ ’, C １ ’, C ２ ’, C ４ ’) of the Chebyshev polynomial are obtained, and the coefficient (C １ ’) of its first-order term is transmitted as a detection result signal of the rolling sheet elongation distribution of the first-order component in the sheet width direction of the (k)-th image Here, xi represents the central position in the width direction of the divided region (i) obtained by dividing the reflected light region into j sections in the width direction of the plate, as denoted by (x). Note that F, i, j, and k are integers. A device for detecting the shape of metal strips.

2. In the metal strip shape detection device according to claim 1, The image processing unit determines the coefficient of the second term (C ２ ') or the coefficient of the fourth term (C ４ The system further transmits one or more of the aforementioned coefficients as a detection result signal of the rolled sheet elongation distribution of the second or fourth component in the sheet width direction. A device for detecting the shape of metal strips.

3. A metal strip plate shape detection device according to claim 1 or 2, In a rolling mill equipped with a control device, Based on the detection result signal, the control device transmits one or more operation signals related to the leveling amount of the rolling mill, the bending force, or the pair cross angle. Rolling mill.

4. In a rolling mill, the shooting step involves using a camera to capture an image of the surface of a metal strip lifted by a looper, including an area where a band-shaped illumination light, called the reflected light region, is reflected across the width of the strip. A method for detecting the shape of a rolled metal strip, comprising: an image processing step for detecting the shape of the metal strip based on the image captured in the aforementioned shooting step, In the aforementioned image processing step, The images were numbered 1, 2, 3, ..., k, ... in the order they were acquired. In the (k)th image, determine the pixel position Pu(k)p in the rolling direction of the pixel point constituting the upstream boundary of the reflected light region (p = 1 to Ru, where Ru is the number of pixel points constituting the upstream boundary of the reflected light region) and the pixel position Pd(k)q in the rolling direction of the pixel point constituting the downstream boundary of the reflected light region (q = 1 to Rd, where Rd is the number of pixel points constituting the downstream boundary of the reflected light region). The distance Mu(k)p of the pixel point on the upstream boundary line in the rolling direction is determined from the difference between the pixel position Pu(k-1)p of image number (k) and the pixel position Pu(k)p of image number (k). The distance Md(k)q of the movement of the pixel point on the downstream boundary line in the rolling direction is determined from the difference between the pixel position Pd(k-1)q of image number (k) and the pixel position Pd(k)q of image number (k). The reflected light region is divided into j sections in the width direction of the plate to form divided regions (i) (i = 1 to j), When capturing the (k)th image, for pixel points located within the range of the divided area (i), calculate the average movement distance Mu(k)i of the pixel points on the upstream boundary line Mu(k)p and the average movement distance Md(k)i of the pixel points on the downstream boundary line Md(k)q. The time Ts between the acquisition times of image number (k-1) and image number (k) is calculated. For each of the divided areas (i), the average movement velocity Vu(k)i of the pixel point on the upstream boundary line is determined from the time Ts and the average movement distance Mu(k)i. For each of the divided areas (i), the average moving velocity Vd(k)i of the pixel point on the downstream boundary line is determined from the time Ts and the average moving distance Md(k)i. For each of the divided regions (i), the number of sign reversals of the average movement velocity Vu(k)i of the pixel points on the upstream boundary line and the number of sign reversals of the average movement velocity Vd(k)i of the pixel points on the downstream boundary line are calculated between acquiring the (k-F+1)th image and the (k)th image. The time Tf between the acquisition time of image number (k - F + 1) and image number (k) is calculated. For each of the divided areas (i), the average fluctuation frequency Qu(k)i of the pixel points constituting the upstream boundary line is determined from the time Tf and the number of sign reversals Nu(k)i. For each of the divided areas (i), the average fluctuation frequency Qd(k)i of the pixel points constituting the downstream boundary line is determined from the time Tf and the number of sign reversals Nd(k)i. The average values ​​of the average fluctuation frequency Qu(k)i and the average fluctuation frequency Qd(k)i are calculated for each divided area (i), and the obtained average value is taken as information Q(k)i corresponding to the two average fluctuation frequencies of the pixel point constituting the upstream boundary line and the pixel point constituting the downstream boundary line of the reflected light region of the (k)-th image, and the value of the information Q(k)i is assigned to the position of the center in the plate width direction of the divided area (i). When the value indicating the position in the width direction of the plate is taken as the variable (x), the position in the width direction of the plate within the plate width range of the reflected light region in the image is normalized to the range -1 ≤ x ≤ 1, and the j values ​​of Q(k)i are used as an index corresponding to the rolled plate elongation distribution in the width direction of the plate obtained from the (k)th image, the notation for the position in the width direction of the plate is changed to (x), and Q(k)i = E(xi), consisting only of 0th, 1st, 2nd, and 4th order terms of x. E(x) = C ０ '+C １ × x + C ２ '×(2x ２ -1) + C ４ '×(8x ４ -8x ２ Substituting this into the Chebyshev polynomial (+1) (where -1 ≤ x ≤ 1), we get E(xi) with j values ​​of x (xi), The coefficient (C) of the Chebyshev polynomial. ０ ', C １ ', C ２ ', C ４ Find the coefficient of the linear term (C) １ The (k)-th image is transmitted as the detection result signal of the rolled sheet elongation distribution of the first component in the sheet width direction. Here, xi represents the central position in the width direction of the divided region (i) obtained by dividing the reflected light region into j sections in the width direction of the plate, as denoted by (x). Note that F, i, j, and k are integers. A method for detecting the shape of a metal strip.

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