Plate shape detecting device for metal strip, rolling mill, and detecting method

Abstract

To cancel out the effect of variations in a looper angle, variations in luminance of illumination, and variations in lightness in surroundings, and assess only changes in plate elongation distribution.SOLUTION: A plate shape detecting device divides an area in an image into a plurality of zones in a plate width direction of a metal strip 1, standardizes and converts a plate width direction position within a plate width range of the area in the image into a range of -1≤x≤1 when a value representing the plate width direction position of each of the divided zones is a variable (x), applies index information representing magnitude corresponding to a plate elongation amount of the area in each of the zones to Chebyshev polynomial E(x) representing distribution E(x) in each of the zones and having only zeroth-order, primary, secondary, and fourth-order terms of x, obtains coefficients, corrects E(x) as Ec(x) such that coefficient C0' of a zeroth-order component of E(x) is constant at all times, and transmits, as information corresponding to the distribution in the plate width direction of the plate elongation in a rolling direction, one or more of a primary corrective coefficient, a secondary corrective coefficient, and fourth-order corrective coefficient as determination result signals of the plate elongation distribution in the plate width direction.SELECTED DRAWING: Figure 1

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 judgment device and method that can easily judge defects in the plate surface shape of a metal strip plate without using a special light source such as a rod-shaped light source, and describes the device and method comprising: a roll that is installed with a rotating axis extending in the width direction of the rolled steel plate and lifts the rolled steel plate upward; a camera that takes an image including the lifted area of the rolled steel plate that has been lifted upward by the roll; and a control device that judges defects in the plate surface shape of the metal strip plate based on the image taken by the camera.

[0003] Patent Document 2 describes a metal strip shape determination device, rolling mill, and determination method that are less susceptible than conventional devices to slight disturbances or suddenly appearing small obstacles. The device and rolling mill and method include a camera installed to capture an image including an area where strip-shaped reflected light is visible across the rolled metal strip in the strip width direction, 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 area in the image into multiple areas in the strip width direction of the metal strip, and transmits information as a signal corresponding to the distribution of strip elongation in the strip width direction based on index information that indicates the size related to the area in each divided area. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6808888 [Patent Document 2] Patent No. 7130350 Summary of the Invention [Problem to be solved by the invention]

[0005] Many techniques have been known for determining whether the shape of a metal strip rolled by a rolling mill is good or bad, for example, whether or not the strip is elongated, based on long linear or rod-shaped reflected light in the width direction of the metal strip.

[0006] This judgment is based on the fact that when a part of the plate stretches and the shape of the plate changes, the shape of the reflected light, which was previously linear or rod-like, no longer becomes regular, and part of it moves or displaces.

[0007] However, since the reflected light area in the rolling direction at each position in the plate width direction is narrow, the linear or rod-shaped reflected light is significantly affected by slight disturbances, such as small obstacles, and is prone to misjudgment.

[0008] The inventors discovered that the influence of such disturbances can be reduced by making judgments using band-shaped reflected light as disclosed in Patent Document 1, and came up with the idea of the technology disclosed in Patent Document 2 as a technology that makes better use of the characteristics of band-shaped reflected light.

[0009] In the technology described in Patent Document 2, distributions in the strip width direction, such as the length in the rolling direction and area of a reflected light area reflected on the strip surface near the curved portion of a metal strip lifted by a tension control looper installed between rolling mill stands on a rolling line, are applied to a Chebyshev polynomial to find coefficients of the Chebyshev polynomial and determine the strip elongation distribution in the strip width direction.

[0010] In response to this, the inventors conducted further intensive research and found that there is room for improvement, because the technology described in Patent Document 2 is based on the premise that changes in the length in the rolling direction and area of the reflected light area reflected on the plate correspond to changes in the rolling elongation of the plate. However, this premise is valid only when the looper angle, i.e., the height of the apex position of the looper, is constant and the brightness of the reflected light area reflected on the plate surface, i.e., the brightness of the lighting and the ambient brightness, is constant.

[0011] Specifically, the looper angle fluctuates during rolling because it is installed to control the line tension. Also, since it becomes difficult to maintain constant brightness due to deterioration of lighting fixtures over time, the brightness of the lighting may fluctuate. Furthermore, the ambient brightness may change between day and night.

[0012] Therefore, even though the distribution of sheet elongation in the sheet width direction is constant, fluctuations in the looper angle and fluctuations in the brightness of the lighting and the surrounding brightness cause the length and area of the reflected light area in the rolling direction reflected on the sheet to fluctuate, causing a phenomenon that makes it appear as if the distribution of sheet elongation is changing, and so it was found that there is room for further improvement.

[0013] The present invention provides a metal strip shape detection device, rolling mill, and detection method that can cancel out the effects of variations in looper angle, as well as variations in lighting brightness and ambient brightness, and evaluate only changes in strip elongation distribution. [Means for solving the problem]

[0014] The present invention includes a plurality of means for solving the above-mentioned problems. One example of such means is a plate shape detection device for a rolled metal band, comprising: a camera installed so as to take an image including an area in which a band-like reflected light is visible across the surface of a metal band lifted by a looper in the plate width direction; and an image processing unit that determines the plate shape of the metal band based on the image taken by the camera, wherein the image processing unit divides the area in the image into a plurality of areas in the plate width direction of the metal band, and when a value indicating the position in the plate width direction of each of the divided areas is set as a variable (x), the image processing unit normalizes and converts the position in the plate width direction within the plate width range of the area in the image into a range of -1≦x≦1, and calculates index information representing a magnitude corresponding to the amount of plate elongation of the area as a distribution E(x) of each of the areas, E(x)=C0′+C1′×x+C2′×(2x 2 -1)+C4'×(8x 4 -8x 2+1) (where -1≦x≦1) to find the coefficients (C0', C1', C2', C4') of the Chebyshev polynomial, and then change E(x) to Ec(x)=C0c+C1c·x+C2c·(2x) so that the coefficient C0' of the 0th order component of the Chebyshev polynomial is always constant. 2 -1)+C4c·(8x 4 -8x 2 +1), and one or more of the first-order correction coefficient (C1c), the second-order correction coefficient (C2c), and the fourth-order correction coefficient (C4c) are transmitted as a determination result signal of the distribution of sheet elongation in the sheet width direction as information corresponding to the distribution of sheet elongation in the rolling direction in the sheet width direction. [Effects of the Invention]

[0015] According to the present invention, the influence of variations in looper angle can be negated, and the influence of variations in lighting brightness and ambient brightness can be negated, so that only changes in the sheet elongation distribution can be evaluated. Other problems, configurations, and effects will become clear from the following description of the embodiments. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a diagram showing an outline of a rolling facility equipped with a metal strip shape detection device according to an embodiment of the present invention; [Figure 2] FIG. 2 is a diagram showing an example of the state of a metal strip between stands during operation in a rolling facility. [Figure 3] FIG. 10 is a diagram showing another example of the state of a metal strip between stands during operation in a rolling facility. [Figure 4] 10A and 10B are diagrams showing an example of a method for calculating an average length within each divided area and a component distribution of a Chebyshev polynomial in the plate shape detection device for a metal strip plate according to the embodiment; [Figure 5] 10 is a diagram showing an example of the distribution of distances between the upstream and downstream boundaries of each divided section of the reflected light area when the metal band is divided into seven sections in the width direction in the plate shape detection device for the metal band according to the embodiment. FIG. [Figure 6] FIG. 10 is a diagram showing a state in which the upper position of the looper is high during operation of the rolling equipment. [Figure 7] FIG. 10 is a diagram showing a state in which the upper position of the looper is low during operation of the rolling equipment. [Figure 8] FIG. 10 is a diagram showing a state in which the illuminance illuminating the reflected light area is bright during operation of the rolling facility. [Figure 9] FIG. 10 is a diagram showing a state in which the illuminance illuminating the reflected light area is low during operation of the rolling facility. [Figure 10] FIG. 2 is a diagram showing an example of a display screen of a monitor in the plate shape detection device for a metal band plate according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] 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 10. In the drawings used in this specification, identical or corresponding components are designated by identical or similar reference numerals, and repeated explanations of these components may be omitted.

[0018] First, the overall configuration of a rolling facility including a metal strip shape detection device will be described with reference to Figures 1 to 3. Figure 1 is a schematic diagram showing the configuration of a metal strip shape detection device of this embodiment and a rolling facility equipped with the same, and Figures 2 and 3 are diagrams showing an example of the state of the metal strip surface between stands during operation in the rolling facility.

[0019] The rolling equipment 100 shown in FIG. 1 for rolling a metal strip 1 includes an F1 stand 10, an F2 stand 20, an F3 stand 30, an F4 stand 40, an F5 stand 50, cameras 61, 62, 63, and 64, loopers 71, 72, 73, and 74 for tension control, an image processing computer 80, a control device 82, a monitor 85, and the like.

[0020] Furthermore, the F1 stand 10, F2 stand 20, F3 stand 30, F4 stand 40, F5 stand 50, cameras 61, 62, 63, 64, image processing computer 80, and control device 82 are connected by a communication line 90.

[0021] The rolling equipment 100 is not limited to the configuration in which five rolling stands are installed as shown in FIG. 1, but may 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, a lower work roll, an upper backup roll that supports the upper work roll and the lower work roll by contacting them, a lower backup roll, reduction cylinders 11, 21, 31, 41, 51 provided above the upper backup rolls, and load detectors 12, 22, 32, 42, 52. Note that a six-stage configuration can be achieved by providing an intermediate roll 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 arranged with its rotation axis extending in the width direction of the metal band 1 so that the traveling metal band 1 can be placed on it, and is installed so as to lift and hold the metal band 1 upward.

[0024] The looper 71 may be, for example, one that is biased upward by a spring or the like, or one that is lifted by a hydraulic cylinder or motor drive.

[0025] The camera 61 is installed so as to capture an image including an area where a strip of reflected light is reflected across the width direction of the rolled metal band 1. Preferably, the camera is installed so as to capture an image including the lifted area of the metal band 1 that has been lifted upward by the looper 71. In particular, the camera can be installed on the outer side of the metal band 1 in the width direction when the metal band 1 is viewed from above. Data of the image captured by the camera 61 is transmitted to the image processing computer 80 via a communication line 90.

[0026] 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.

[0027] Camera 62 is installed at a position where it takes an image including the lifted area of metal band 1 lifted vertically upward by looper 72, camera 63 is installed at a position where it takes an image including the lifted area of metal band 1 lifted upward by looper 73, and camera 64 is installed at a position where it takes an image including the lifted area of metal band 1 lifted upward by looper 74. Data of the images taken by cameras 62, 63, and 64 is transmitted to image processing computer 80 via communication line 90.

[0028] Like the camera 61, the cameras 62, 63, and 64 are preferably installed on the outer sides of the metal band 1 in the width direction when the metal band 1 is viewed from above.

[0029] A photographing step is executed in which the cameras 61, 62, 63, and 64 photograph an image including an area in which strip-shaped reflected light that crosses the rolled metal strip 1 in the strip width direction is captured.

[0030] Lighting may also be provided to illuminate the lifted photographing area of the metal strip 1 lifted upward by the rolls, which is mainly photographed by the cameras 61, 62, 63, and 64. This lighting may be general lighting appropriately placed on the ceiling of the rolling factory where the rolling equipment 100 is installed, and no special new lighting equipment is required in the present invention, although dedicated lighting may be provided.

[0031] The image processing computer 80 executes various processes (including image processing steps) for determining the plate shape of the metal strip 1 based on the images captured by the cameras 61, 62, 63, and 64.

[0032] For example, an image including the lifted area, which is near the curve of the metal band plate 1 lifted upward by loopers 71, 72, 73, and 74 as shown in Figure 2 or Figure 3, is processed to identify the range including the upstream and downstream boundaries of the point where the brightness of the reflected light on the surface of the metal band plate 1 shown in the image is greater than a specific brightness value as reflected light area 1A or reflected light area 1B.

[0033] In this embodiment, the image processing computer 80 divides the reflected light area in the image into multiple areas in the width direction of the metal strip 1, and transmits information on the distribution in the width direction of the plate regarding the plate elongation in the rolling direction as a signal based on index information related to the size of the reflected light area corresponding to the plate elongation amount, such as the boundary position and area value of the upstream and downstream reflected light areas 1A, 1B in each divided area.

[0034] In the region where the strip-like reflected light is visible across the width direction of the metal band 1, if the elongation in the rolling direction (longitudinal direction of the band) at each position in the width direction of the metal band 1 is uniform, the surface of the metal band 1 is flat and the plate waves are small, so there is little difference in distribution depending on the direction of illumination, as shown in Figure 2. For this reason, the boundary lines of the reflected light region 1A due to illumination are approximately parallel on the upstream and downstream sides, and when the reflected light region 1A is divided into multiple regions in the width direction, the various parameters as described above for each region are approximately the same or uniform in all regions.

[0035] In contrast, if the elongation in the rolling direction differs depending on the position in the strip width direction (e.g., end elongation, center elongation), the way the light hits will differ due to differences in height, such as plate waves, and the boundary line of the reflected light area 1B caused by the illumination will be wavy on either the upstream side, the downstream side, or both sides, and will not be parallel, as shown in Figure 3. For this reason, when the metal band-shaped reflected light area 1B is divided into multiple areas in the strip width direction, the parameters such as the length in the rolling direction of each area will be non-uniform depending on the position in the strip width direction.

[0036] Therefore, the image processing computer 80 divides various parameters (index information) into multiple parts in the sheet width direction, and finds them, including values relating to the two boundary lines on the upstream and downstream sides of the reflected light region and area values relating to the distance between them, and preferably uses Chebyshev polynomials to resolve these values into each component (distribution of zeroth-order component, first-order component, second-order component, and fourth-order component). The judgment results according to each component value are output to the monitor 85 and the control device 82. The details will be explained in detail later using Figure 4 and subsequent figures. Preferably, this image processing computer 80 is the entity that executes the image processing steps.

[0037] Returning to FIG. 1, the control device 82 is a device that controls the operation of each device in the rolling equipment 100, and in this embodiment, is a device that executes various controls in response to the determination of the plate shape of the metal strip 1 by the image processing computer 80.

[0038] These image processing computer 80 and control device 82 can be configured as computers having a monitor 85 such as a liquid crystal display (described later), input devices, storage devices, a CPU, memory, etc., and may be configured as one computer or as separate computers, and are not particularly limited.

[0039] The control of the operation of each device by the image processing computer 80 and the control device 82 is executed based on various programs recorded in a storage device. Note that the control processing of the operation executed by the image processing computer 80 and the control device 82 may be integrated into a single program, or may be separated into multiple programs, or a combination thereof. Furthermore, some or all of the programs may be realized by dedicated hardware, or may be modularized.

[0040] The monitor 85 is a display device such as a display or an audio device such as an alarm. For example, when the image processing computer 80 determines that there is a problem with the plate shape, the monitor 85 is a device that notifies the operator of the necessary steps to be taken. Therefore, a display is often used as the monitor 85.

[0041] Here, the image processing computer 80 described above includes a display signal section, and transmits to the monitor 85 a signal relating to the content to be displayed on the monitor 85 .

[0042] During operation, the operator can check the state of the strip shape by visually checking the display screen of the monitor 85, each stand itself, and the spaces between the stands.

[0043] In addition, the present invention is not limited to a configuration in which the control device 82 notifies the operator of the occurrence of a problem with the plate shape and automatically performs operations to improve the problem with the plate shape, but may be a configuration in which the information is only displayed on the monitor 85, or a configuration in which the display on the monitor 85 is omitted and the control device 82 only automatically performs operations to improve the problem with the plate shape.

[0044] Next, specific examples of the plate shape detection device and detection method for the rolled metal strip 1 according to the present invention will be described with reference to Fig. 4 and subsequent figures. First, the details of the method for calculating the state quantity in the width direction from the calculated values of the boundary lines of the reflected light region will be described with reference to Figs. 4 and 5.

[0045] Fig. 4 is a diagram showing an example of a method for calculating index information in each divided area of the reflected light area in the plate shape detection device for a metal strip plate of the embodiment, and a component distribution of each degree of the Chebyshev polynomial. Fig. 5 is a diagram showing an example of a distribution of the distance between the boundary lines on the upstream and downstream sides of each divided area of the reflected light area when the range including the reflected light area of the metal strip plate is divided into seven in the plate width direction.

[0046] First, the image processing computer 80 performs binarization processing for each pixel on a selected rolled surface image range from among the images captured by the cameras 61, 62, 63, and 64, and determines an appropriate brightness threshold value to determine two width-direction boundary lines on the upstream and downstream sides of the reflected light region in the rolling direction. This processing is performed throughout the entire width direction of the plate to identify the reflected light regions 1A and 1B. The details of this processing can be determined by a known method.

[0047] Next, the reflected light regions 1A and 1B were divided into N sections in the width direction of the plate (5 sections in FIG. 4, 7 sections in FIG. 5). When j is the number (No.) of each divided section (j = 1 to N), for pixels present in the image of divided section No. j, the distance between the boundary lines in the rolling direction (Y-axis direction) between the upstream and downstream sides of the reflected light region was determined for each pixel position in the width direction (X-axis direction) of the plate, and index information was calculated. For example, in FIG. 4, the average length Laj in the rolling direction for each divided section was calculated as index information, and the results were plotted as a bar graph.

[0048] In this case, the Chebyshev polynomial, which will be described in detail later, E(x) = C0'+C1'×x+C2'×(2x 2 -1)+C4'×(8x 4 -8x 2 +1) … (1) When approximating the index information E(x), there are four unknown coefficients (C0, C1, C2, C4) to be described later for finding C0', C1', C2', and C4', and four or more relational expressions are required to find the unknowns, so the number of divisions in the strip width direction is set to four or more. Also, since it is desirable for the center part in the strip width direction to belong to a certain division area, it is desirable to set the number of divisions to an odd number so that the center part of the strip width is not located on the boundary between the division areas.

[0049] It is preferable that one divided area contains multiple pixels in the strip width direction. This is to reduce the impact of any abnormalities in the pixels in the strip width direction. The number of divisions is preferably between 4 and 11. An odd number is particularly preferable. The lower limit of 4 for the number of divisions is to enable the coefficients of the Chebyshev polynomial to be determined, and the upper limit of 11 for the number of divisions is because 11 divisions are sufficient to obtain coefficients with sufficient accuracy, and even if the number of divisions is increased beyond this, the calculation load increases and the accuracy does not improve.

[0050] Next, the image processing computer 80 standardizes the position of the area in the image in the strip width direction by converting the coordinates into the range of -1≦x≦1, where x=-1 represents the drive side (DS) end of the strip width, x=1 represents the work side (WS) end of the strip width, and x=0 represents the center position of the strip width. The index information for each divided area is the distribution (E(x)) of each divided area, and E(x)=C0+C1×x+C2×x consists of only 0th, 1st, 2nd, and 4th order terms. 2 +C4×x 4 First, the coefficient vector (C0, C1, C2, C4) of each component is calculated using the function expressed by the formula above. Then, the Chebyshev polynomial coefficient vector (C0', C1', C2', C4') of each component is calculated by treating the Chebyshev polynomial and the above formula as equivalent formulas.

[0051] The features of approximating the index information corresponding to the distribution of strip elongation in the rolling direction relative to the strip width direction using Chebyshev polynomials are: (1) the strip width range (X-axis) is normalized within the range of -1 to +1, and (2) the first-order component (strip elongation), second-order components (center elongation and edge elongation), and fourth-order component (quarter elongation) are separated, making it easy to determine the control input for each component.

[0052] The following describes how to calculate the Chebyshev polynomial coefficient vectors (C0', C1', C2', C4') from the measured values of each divided area. Here, we will explain an example where the width direction of the metal band plate 1 is divided into seven sections, as shown in Figure 5, unlike Figure 4 etc.

[0053] As shown in Fig. 5, each distribution value vector (E1, E 2、 E 3、 E 4、 E 5、 E 6、 The relation between the vector (C0, C1, C2, C4) and the coefficient vector (C0, C1, C2, C4) of the quartic equation can be expressed as the following equation (2) when x = xi. E(x i )=C0+C1×x i +C2×x i 2 +C4×x i4 (i=1~7) (2) When equation (2) is expressed as a vector and a matrix, it becomes equation (3) shown below.

[0054]

number

[0055] In equation (3), the strip width direction position (x) is (-1≦x≦1), where x=-1 represents the strip width end position on the drive side (DS) and x=1 represents the strip width end position on the work side (WS). xi (i=1 to 7) is the strip width direction position (-1≦xi≦1) where the detection value at each divided zone position is set, and can be said to be the width direction position coordinate (xi) at the center position of each divided zone, with the strip width center position being x=0.

[0056] From this equation (3), the unknown vector (C0, C1, C2, C4) is calculated using the least squares method to find the Chebyshev polynomial coefficient vector (C0', C1', C2', C4'). The least squares method used here can be as follows:

[0057] First, if we express equation (3) in matrix and vector form as E=M×C, the transpose matrix M is written on the left and right sides. T Multiplying by this gives the following equation (4).

[0058] M T ×E= (M T ×M)×C ··· (4) However, E = [E 1, E 2, E 3, E 4, E 5, E 6, E7], M=[[1 , x 1, x1 2 , x1 4 ],[1 , x 2, x2 2 , x2 4 ],[1, x 3, x3 2 , x3 4 ],[1 , x 4, x4 2 , x4 4 ],[1 , x 5, x5 2 , x5 4 ],[1 , x 6, x6 2 , x6 4 ],[1 , x 7, x7 2 , x7 4 ]], C=[C 0, C 1, C 2, C4].

[0059] Therefore, the coefficient vector C is a matrix (M T ×M) inverse matrix (M T ×M) -1 is used and calculated using the following formula (5). C= (M T ×M) -1 ×M T ×E (5) From this equation (5), (C0, C1, C2, C4) are found, and the index information E(x) indicating the state of the reflected light area is expressed by the Chebyshev polynomial coefficient vector (C0', C1', C2', C4'), resulting in the above equation (1).

[0060] Therefore, (C0', C1', C2', C4') can be calculated using the following formula (6) based on formulas (1) and (2).

[0061]

number

[0062] Here, the zeroth-order component term C0' is necessary for the formula, so it is desirable to find it. The zeroth-order component term C0' represents the index information that forms the overall baseline (foundation), and the other order components represent the component distribution of each order on top of that baseline. When there is no sheet elongation distribution corresponding to the first-order or higher components, the distance between the boundary lines on the upstream and downstream sides of the reflected light area will be an approximately uniform length in the rolling direction, as shown in Figure 2.

[0063] Here, as a result of intensive research by the present inventors, it has become clear that it is possible to deal with the above-mentioned fluctuations in the angle and illuminance of the loopers 71, 72, 73, and 74 by performing the following additional processing. This will be explained below with reference to Figs. 6 to 9. Fig. 6 is a diagram showing a state when the looper top position h is high during operation of the rolling equipment, Fig. 7 is a diagram showing a state when the looper top position h is low, Fig. 8 is a diagram showing a state when the illuminance illuminating the reflected light area is bright, and Fig. 9 is a diagram showing a state when the illuminance illuminating the reflected light area is dark.

[0064] Patent Document 2 assumes that changes in the length and area of the reflected light area reflected on the plate in the rolling direction correspond to changes in the rolling elongation of the plate. This assumption holds true when the angle θ of the loopers 71, 72, 73, and 74, i.e., the height of the vertex position h of the loopers 71, 72, 73, and 74, is constant, and the brightness of the reflected light area reflected on the surface of the metal band plate 1, i.e., the brightness of the lighting and the ambient brightness, is constant.

[0065] However, because the loopers 71, 72, 73, and 74 are installed to control the line tension, the angle θ of the loopers 71, 72, 73, and 74 fluctuates during rolling. Furthermore, it becomes difficult to maintain constant brightness due to deterioration of lighting fixtures over time, and the brightness of the lighting may fluctuate. Furthermore, the ambient brightness may change between day and night, and the brightness may also be affected by factors such as the weather outside the factory.

[0066] For example, as shown in Fig. 6, when the upper positions h of the loopers 71, 72, 73, and 74 are high, the length w of the reflected light regions 1A and 1B in the rolling direction is relatively shorter than when the upper positions h of the loopers 71, 72, 73, and 74 are low as shown in Fig. 7. Furthermore, when the illuminance of the reflected light regions is bright as shown in Fig. 8, the length w of the reflected light regions 1A and 1B in the rolling direction is relatively longer than when the illuminance of the reflected light regions is dark as shown in Fig. 9.

[0067] In this way, even though the sheet elongation distribution in the sheet width direction is constant, fluctuations in the angle θ of the loopers 71, 72, 73, and 74, as well as fluctuations in the brightness of the lighting and the surrounding brightness, cause fluctuations in the length and area in the rolling direction of the reflected light area reflected on the sheet, resulting in a phenomenon that appears as if the sheet elongation distribution is changing.

[0068] Therefore, in the present invention, the influence of such fluctuations in the angle θ of the loopers 71, 72, 73, and 74 is counteracted, and furthermore, the influence of fluctuations in the brightness of the lighting and fluctuations in the ambient brightness is counteracted, and processing is further performed to evaluate only the changes in the plate elongation distribution.

[0069] As described above, in Patent Document 2, the Chebyshev polynomial applied to the distribution in the strip width direction, such as the length in the rolling direction and the area of the reflected light area reflected on the surface of the metal strip 1 near the curved portion of the metal strip 1 lifted by the loopers 71, 72, 73, and 74, is expressed as Equation (1).

[0070] Here, E(x) in the formula (1) represents the distance in the rolling direction of the reflected light area on the surface of the metal band plate 1 at the loopers 71, 72, 73, and 74.

[0071] The rolling direction distance of the reflected light area on the surface of the metal strip plate 1 at the loopers 71, 72, 73, and 74 corresponds to the radius of curvature of the plate in the rolling direction, provided that the height positions of the loopers 71, 72, 73, and 74 are constant and the brightness of the lighting and the ambient brightness are constant and do not change, and the radius of curvature of the plate in the rolling direction is determined by the magnitude of the plate elongation.

[0072] In other words, if the angles of the loopers 71, 72, 73, and 74 are constant and the brightness of the lighting is constant, E(x) represents the distance in the rolling direction of the reflected light area on the surface of the metal strip 1 at the loopers 71, 72, 73, and 74, which corresponds to the sheet elongation.

[0073] Therefore, we will correct the Chebyshev coefficients independent of changes in the angle of the loopers 71, 72, 73, and 74 and changes in the lighting luminance and surrounding brightness. First, we will introduce a proportional correction coefficient F(θ, L), which is a function of the angle θ of the loopers 71, 72, 73, and 74 and the illuminance L of the reflected light area due to the lighting luminance and surrounding brightness.

[0074] The Chebyshev polynomial obtained by correcting equation (1) so as to be independent of changes in the angle θ of the loopers 71, 72, 73, and 74 and changes in the illuminance L of the reflected light area is written as the following equation (7).

[0075] Ec(x) = C0c + C1cx + C2c(2x 2 -1) + C4c(8x 4 -8x 2 +1) (-1≦x≦1) (7) In other words, Ec(x) is defined as a pure relative distribution of plate elongation that does not depend on changes in the angle of the loopers 71, 72, 73, and 74 or on changes in the illumination brightness.

[0076] E(x) in equation (1) can be calculated by multiplying Ec(x) in equation (7), which represents the pure sheet elongation distribution, by a proportional correction coefficient F(θ, L), which is a function of the angle θ of the loopers 71, 72, 73, and 74 and the illuminance L of the reflected light area formed on the surface of the metal strip. In other words, it can be written as the following equation (8).

[0077] E(x) = F(θ,L)Ec(x) = F(θ,L)[C0c + C1cx + C2c(2x 2 -1) + C4c(8x 4 -8x 2 +1)] (8) That is, from equations (1) and (8), the following relationships such as equations (9) to (12) can be obtained.

[0078] C0' = F(θ,L)C0c (9) C1' = F(θ,L)C1c (10) C2' = F(θ,L)C2c (11) C4' = F(θ,L)C4c (12) Here, the Chebyshev coefficients (C0c, C1c, C2c, C4c) of Ec(x), which represent the pure sheet elongation distribution, can be written as the following equations (13) to (16) from equations (9) to (12).

[0079] C0c = C0' / F(θ,L) ··· (13) C1c = C1' / F(θ,L) ··· (14) C2c = C2' / F(θ,L) ··· (15) C4c = C4' / F(θ,L) ··· (16) In this way, if F(θ, L) can be determined, the Chebyshev coefficients (C0c, C1c, C2c, C4c) of Ec(x), which represents the pure plate elongation distribution, can be obtained.

[0080] Next, the flow of deriving the proportional correction coefficient F(θ, L), which is a function of the angle θ of the loopers 71, 72, 73, and 74 and the illuminance L illuminating the reflected light area, will be described.

[0081] When the angle θ of the loopers 71, 72, 73, and 74 does not change and the illuminance L of the reflected light area does not change either, E(x) in equation (1) is fulcrum at x=0, which is the center position of the strip width. The first-order component (C1'), second-order component (C2'), and fourth-order component (C4') of the Chebyshev coefficient in equation (1) indicate left-right changes with respect to the strip width, but the zeroth-order component (C0') of the Chebyshev coefficient indicates the average amount of strip elongation caused by rolling, and it is determined that this will always be maintained at a constant value if constant reduction rate control is performed in each rolling mill.

[0082] That is, the 0th-order component (C0') of the Chebyshev coefficient in equation (1) at a certain time t (Time=t) is written as (C0't) as shown in the following equation (17), and it is assumed that the 0th-order component of the Chebyshev coefficient should always show a constant value of C0std below.

[0083] C0't = C0std (C0std: constant value) (17) If the zeroth-order correction coefficient (C0c) of the Chebyshev coefficient in Ec(x) of equation (7), which expresses the pure plate elongation distribution that is not dependent on the angle change of the loopers 71, 72, 73, and 74 or the change in illuminance in the reflected light area, is also taken to represent a constant value of C0std, it can be written as follows:

[0084] C0c = C0std (18) By substituting equation (18) into equation (13), the proportional correction coefficient F(θ, L), which is a function of the angle θ of the loopers 71, 72, 73, and 74 and the illuminance L of the reflected light area, can be written as the following equation (19).

[0085] F(θ,L) = C0' / C0std ··· (19) Next, the Chebyshev coefficients (C0c, C1c, C2c, C4c) of Ec(x), which represents the pure sheet elongation distribution, are calculated.

[0086] Here, by substituting equation (19) into equations (13) to (16), the Chebyshev coefficients of Ec(x), which represent the pure sheet elongation distribution, namely the zeroth-order correction coefficient (C0c), the first-order correction coefficient (C1c), the second-order correction coefficient (C2c), and the fourth-order correction coefficient (C4c), can be obtained as shown in the following equations (20) to (23).

[0087] C0c = C0'C0std / C0'= C0std ··· (20) C1c = C1'C0std / C0' (21) C2c = C2'C0std / C0' (22) C4c = C4'C0std / C0' (23) In other words, by using equations (20) to (23), it is possible to more accurately determine the Chebyshev coefficients, which are independent of the angle θ of the loopers 71, 72, 73, and 74, and independent of the illuminance L of the reflected light area, which is affected by fluctuations in the brightness of the lighting and fluctuations in the ambient brightness, but which depend only on the magnitude of the plate elongation.

[0088] In this embodiment, the third-order component is not adopted because the rolling control mechanism of the rolling mill is not designed to handle the correction of strip elongation for the third-order component, and by omitting the calculation processing and handling means for the third-order component, it becomes easier to judge the status of the rolled strip shape for the separated first-order component, second-order component, and fourth-order component and to correct strip elongation.

[0089] Based on the polynomial approximation result in the strip width direction obtained by this equation (6), the image processing computer 80 can output a control command signal to the control device 82 to correct the leveling, bending force, pair cross angle, etc. Furthermore, instead of or in addition to this, it can output a display command signal to the monitor 85 to display guidance required to correct the leveling, bending force, pair cross angle, etc., thereby conveying correction information for the leveling, bending force, pair cross angle, etc. to the operator.

[0090] Preferably, the image processing computer 80 calculates the 0th component (C0c), the 1st component (C1c×x), the 2nd component (C2c×(2x)) of the function of each order term vector (C0c, C1c, C2c, C4c) in the above-mentioned E(x). 2 -1)), 4th order component (C4c×(8x 4 -8x 2 +1)) can be sent to the monitor 85 to display a graph of each component term. The screen displayed on the monitor 85 will be, for example, as shown in FIG.

[0091] Fig. 10 is a diagram showing an example of the monitor display screen. In Fig. 10, the zeroth-order component term (C0c) is also displayed, but because automatic control and operational support to the operator are not performed based on the zeroth-order component term, it is not necessarily necessary to transmit or display a signal of the zeroth-order component term to the monitor 85. Note that the zeroth-order component term can provide information on changes in line tension.

[0092] The operator can check the screen shown in Figure 10 and perform operations to correct, for example, the leveling, bending force, pair cross angle (in the case of a pair cross rolling mill), etc. For example, since the first-order component (C1c x x) indicates one-sided elongation, the leveling of the rolling cylinders 11, 21, 31, 41, and 51 will be manipulated.

[0093] Among the Chebyshev polynomial coefficients of the corrected Ec(x), the first-order component C1c indicates an index of one-sided elongation, so an operation command signal is output to the control device 82 to normalize the first-order component (within the target range) by manipulating the leveling of the driving side (DS) and working side (WS) pressing cylinders 41 on the upstream side of the camera 64 in question, and / or the driving side (DS) and working side (WS) pressing cylinders 51 on the downstream side.

[0094] Among the Chebyshev polynomial coefficients of the corrected Ec(x), the second-order component C2c indicates an index of edge or middle buckling. Therefore, one or more of the following operations are performed: An operation command signal is output to the control device 82 to operate the work roll / intermediate roll bending device of the F4 stand 40, which is the upstream rolling mill of the corresponding camera 64, and / or the F5 stand 50, which is the downstream rolling mill; in the case of a pair cross rolling mill, to operate the pair cross angle; or in the case of a work roll shift / intermediate roll shift rolling mill, to predict middle buckling / edge buckling in advance and shift the work rolls / intermediate rolls, since shifting during rolling is difficult. This normalizes the second-order component (to within the target range).

[0095] Among the Chebyshev polynomial coefficients of the corrected Ec(x), the fourth-order component C4c indicates an index of quarter elongation. Therefore, to correct quarter elongation, one or more of the following operations are performed: The work roll bending device of the F4 stand 40, which is the upstream rolling mill of the corresponding camera 64, and / or the F5 stand 50, which is the downstream rolling mill, is bent. Furthermore, in the case of a pair cross mill, the pair cross angle is adjusted either in conjunction with the bending operation or independently. In the case of a six-high intermediate roll shift rolling mill, quarter elongation is predicted in advance and the intermediate rolls are shifted to the appropriate position. By outputting an operation command signal to the control device 82 to perform the bending operation and pair cross angle adjustment, the fourth-order component indicating quarter elongation is normalized (within the target range to achieve the target strip shape). Note that quarter elongation is more likely to occur when the roll diameter is smaller relative to the roll length because the roll is more likely to bend in the roll width end region due to the bending operation. However, the above operations can normalize it.

[0096] Next, the effects of this embodiment will be described.

[0097] In the sheet shape detection device for a rolled metal strip 1, the device comprises cameras 61, 62, 63, 64 installed so as to capture an image including an area where strip-shaped reflected light is visible across the surface of the metal strip 1 lifted by the loopers 71, 72, 73, 74 of the present embodiment described above, and an image processing computer 80 for determining the sheet shape of the metal strip 1 based on the images captured by the cameras 61, 62, 63, 64, the image processing computer 80 divides the area in the image into a plurality of areas in the sheet width direction of the metal strip 1, and when a value indicating the position in the sheet width direction of each of the divided areas is set as a variable (x), the image processing computer 80 normalizes and converts the position in the sheet width direction within the sheet width range of the area in the image to the range of -1≦x≦1, and obtains index information representing the magnitude corresponding to the sheet elongation amount of the area as a distribution E(x) of each area, which is E(x)=C0′+C1′×x+C2′×(2x 2 -1)+C4'×(8x 4 -8x 2+1) (where -1≦x≦1) to find the coefficients of the Chebyshev polynomial (C0', C1', C2', C4'). Then, E(x) is calculated so that the coefficient C0' of the 0th order component of the Chebyshev polynomial is always constant: Ec(x)=C0c+C1c·x+C2c·(2x 2 -1)+C4c·(8x 4 -8x 2 +1), and one or more correction coefficients from among a first-order correction coefficient (C1c), a second-order correction coefficient (C2c), and a fourth-order correction coefficient (C4c) are transmitted as a determination result signal of the strip elongation distribution in the strip width direction as information corresponding to the distribution of strip elongation in the rolling direction in the strip width direction.

[0098] This process makes it possible to correct the Chebyshev coefficients independent of changes in the angles of the loopers 71, 72, 73, and 74, as well as changes in lighting luminance and ambient brightness, thereby canceling out the effects of variations in the looper angles, as well as the effects of variations in lighting luminance and ambient brightness, and making it possible to evaluate only changes in the distribution of plate elongation.As a result, plate elongation can be detected with greater accuracy than before.

[0099] Furthermore, the first-order correction coefficient (C1c), second-order correction coefficient (C2c), and fourth-order correction coefficient (C4c) are expressed as C1c = C1'C0std / C0' (21), C2c = C2'C0std / C0' (22), and C4c = C4'C0std / C0' (23), where C0std is a constant, and C0' indicated at a specific time, Time=t, is used to express C0std=C0't, and C0' at Time=t is expressed as C0'=C0't. This correction makes it possible to more accurately evaluate pure changes in the sheet elongation distribution, even if there are fluctuations in the looper angle and changes in illuminance.

[0100] <Other> The present invention is not limited to the above-described embodiment, and various modifications and applications are possible. The above-described embodiment has been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to having all of the described configurations. [Explanation of symbols]

[0101] 1...Metal strip 1A,1B…Reflected light area 10...F1 Stand 11, 21, 31, 41, 51...Pressure cylinder 12, 22, 32, 42, 52...Load detector 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) 82...Control device 85...Monitor 90...Communication line 100...Rolling equipment

Claims

1. a camera installed so as to capture an image including an area where a strip of reflected light is reflected across the surface of the metal band plate lifted by the looper in the width direction of the plate; an image processing unit that determines the plate shape of the metal band plate based on the image captured by the camera, The image processing unit divides the region in the image into a plurality of regions in the width direction of the metal strip, and when a value indicating the position in the width direction of each of the divided regions is set as a variable (x), the image processing unit normalizes and converts the position in the width direction of each of the regions in the image within the width range of the region to a range of -1≦x≦1, and calculates a distribution E(x) of each of the regions, where E(x)=C is an index information representing a magnitude corresponding to the amount of elongation of the region in the region, and the distribution E(x) is a value consisting of only 0th, 1st, 2nd, and 4th order terms of x. ０ '+C １ '×x+C ２ '×(2x ２ -1) + C ４ '×(8x ４ -8x ２ +1) (where -1≦x≦1) and apply it to the Chebyshev polynomial, and the coefficients (C ０ ', C １ ', C ２ ', C ４ ') and In the E(x), the coefficient C of the 0th order component of the Chebyshev polynomial ０ ' is always constant, so that E(x) is Ec(x)=C ０ c+C １ c・x+C ２ c・(2x ２ -1)+C ４ c・(8x ４ -8x ２ +1) Corrected as As information corresponding to the distribution of the sheet elongation in the rolling direction in the sheet width direction, a primary correction coefficient (C １ c), the secondary correction coefficient (C ２ c), and the fourth-order correction factor (C ４ c) any one or more of the correction coefficients is transmitted as a judgment result signal of the strip elongation distribution in the strip width direction.

1. A plate shape detection device for a metal strip plate.

2. 2. The plate shape detection device for a metal strip according to claim 1, The primary correction coefficient (C １ c), the secondary correction coefficient (C ２ c), and the fourth-order correction coefficient (C ４ c) is expressed by the following formula: C １ c=C １ ’C ０ std / C ０ ’ C ２ c=C ２ ’C ０ std / C ０ ’ C ４ c=C ４ ’C ０ std / C ０ ’ However, C ０ std is a constant, and C indicated at a specific time Time = t ０ ' to C ０ std=C ０ 't, and C when Time = t ０ 'But C ０ '=C ０ Let's say 't 1. A plate shape detection device for a metal strip plate.

3. The plate shape detection device for a metal strip plate according to claim 1 or 2; A rolling mill equipped with a control device, The control device transmits one or more operation signals related to the leveling amount, bending force, or pair cross angle of the rolling mill based on the judgment result signal. A rolling mill characterized by:

4. a photographing step of photographing an image including an area in which a strip of reflected light is reflected across the width direction of the metal band lifted by the looper using a camera; an image processing step of determining the shape of the metal band based on the image captured in the photographing step, In the image processing step, the region in the image is divided into a plurality of regions in the width direction of the metal strip, and when a value indicating the position in the width direction of each of the divided regions is set as a variable (x), the position in the width direction of the region in the image within the width range is normalized and converted to a range of -1≦x≦1, and index information indicating the magnitude corresponding to the amount of elongation of the region in the region is set as a distribution E(x) of each of the regions, E(x)=C consisting of only 0th, 1st, 2nd, and 4th order terms of x. ０ '+C １ '×x+C ２ '×(2x ２ -1) + C ４ '×(8x ４ -8x ２ +1) (where -1≦x≦1) and apply it to the Chebyshev polynomial, and the coefficients (C ０ ', C １ ', C ２ ', C ４ ') and In the E(x), the coefficient C of the 0th order component of the Chebyshev polynomial ０ ' is always constant, so that E(x) is Ec(x)=C ０ c+C １ c・x+C ２ c・(2x ２ -1)+C ４ c・(8x ４ -8x ２ +1) Corrected as As information corresponding to the distribution of the sheet elongation in the rolling direction in the sheet width direction, a primary correction coefficient (C １ c), the secondary correction coefficient (C ２ c), and the fourth-order correction factor (C ４ c) any one or more of the correction coefficients is transmitted as a judgment result signal of the strip elongation distribution in the strip width direction. A method for detecting the shape of a metal strip plate.

5. 5. The method for detecting the shape of a metal band plate according to claim 4, In the image processing step, The primary correction coefficient (C １ c), the secondary correction coefficient (C ２ c), and the fourth-order correction coefficient (C ４ c) is expressed by the following formula: C １ c=C １ ’C ０ std / C ０ ’ C ２ c=C ２ ’C ０ std / C ０ ’ C ４ c=C ４ ’C ０ std / C ０ ’ However, C ０ std is a constant, and C indicated at a specific time Time = t ０ ' to C ０ std=C ０ 't, and C when Time = t ０ 'But C ０ '=C ０ Let's say 't A method for detecting the shape of a metal strip plate.

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