Robust determination of end wave of metal strip

Abstract

To provide the possibility of easily recognizing at least the end waves in a rolled metal strip. [Solution] A metal strip 2 extending in the width direction from the operator-side strip end 4 to the drive-side strip end 5 moves out of the rolling stand 1 in the direction of transport. An evaluation means repeatedly receives images of the metal strip 2 captured by a camera 8. For the operator-side strip end 4 and the drive-side strip end 5, the evaluation means determines the value of one coordinate y as a function of the other coordinate x in the two-dimensional coordinate system associated with each image, thereby determining the characteristics of each strip end 4 and 5 as a function of the other coordinate x in each image. The evaluation means uses the characteristics of each strip end 4 and 5 within each evaluation range of the image to determine the measured amount for the end curvature of each strip end 4 and 5.

Description

[Technical Field]

[0001] The present invention relates to a method for determining edge waves of a metal strip, which extends in the width direction across the strip width from the operator-side strip end to the drive-side strip end and travels out of the rolling stand in the transport direction, wherein - an evaluation means repeatedly and continuously receives images of the metal strip captured by a camera from the camera, is based on the determining method.

[0002] The present invention is additionally based on a computer program for software-programmable evaluation means, wherein the computer program contains machine code that can be directly processed by the evaluation means, and processing of the machine code by the evaluation means causes the evaluation means to execute such a determining method.

[0003] The present invention is additionally based on an evaluation means that is software-programmable and programmed through use of such a computer program to execute such a determining method.

[0004] The present invention relates to a rolling device, wherein - the rolling device has a rolling stand for rolling the metal strip such that the metal strip extending in the width direction across the strip width from the operator-side strip end to the drive-side strip end travels out of the rolling stand in the transport direction, - the rolling device has a camera, - the rolling device has an evaluation means connected to the camera via a data link for the purpose of receiving images captured by the camera, is implemented as such an evaluation means, and executes such a determining method, is additionally based on the rolling device. [Background Art]

[0005] The subject matter mentioned is known from, for example, Patent Document 1.

[0006] In the aforementioned WO document, the camera is positioned centrally above the metal strip. The location of the strip ends is detected to determine the extent to which the metal strip is further evaluated for wavering. This involves evaluating the intensity variations of zonal regions that propagate in the direction of transport of the metal strip. Each individual zonal region is only small in width. However, as a whole, these zonal regions cover the entire width of the metal strip. Therefore, the evaluation of two zonal regions at the ends of the metal strip provides a quantifiable measure of the resulting end wave.

[0007] The process of capturing images of a metal strip moving out of a rolling stand and determining its flatness based on these images is known from Patent Documents 2, 3, and 4. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] International Publication No. 2023 / 041253 [Patent Document 2] International Publication No. 2021 / 105364 [Patent Document 3] Japanese Patent Application Publication No. 4-279208 [Patent Document 4] European Patent Application Publication No. 2258492 [Overview of the project] [Problems that the invention aims to solve]

[0009] In metal strip rolling, continuous attempts are being made to produce flat metal strips that are stress-free, have no outward strain, and are therefore flat. This occurs when the metal strip is rolled perfectly uniformly in the width direction, i.e., rolled with a constant relative reduction when visible in the width direction. If the rolling is non-uniform in the width direction, some longitudinal strips of the metal strip (when visible in the width direction) are rolled more than other longitudinal strips of the metal strip. As a result, the metal strip forms waves in the more heavily rolled longitudinal strips. This can result in a central wave, an end wave, and so-called quarter wave. Thus, the metal strip becomes non-planar, and the external (=visible) flatness is non-zero. If there is a small difference in length, or if the metal strip is subjected to tension, the external flatness is zero, but when tension is applied, the difference in length results in a difference in internal tensile stress. Therefore, in this case, the internal stress of the metal strip is non-zero. The waves mentioned may still be present in cases of widespread non-planarity, even when the metal strip is subjected to tension. Recognizing and, where possible, correcting defects in planarity in rolled metal strips is extremely important.

[0010] The environmental conditions in metal strip rolling are often extremely harsh, including high temperatures, vibrations, water or steam, oil vapor, as well as dust and rust particles. This complicates the operation of measuring devices to obtain values ​​that are characteristic of poor planarity, often resulting in high costs and large spatial requirements.

[0011] An objective of the present invention is to create the possibility of easily recognizing at least the edge waves in a rolled metal strip. [Means for solving the problem]

[0012] The objective is achieved by a determination method having the features of claim 1. Advantageous design of the operating method is the subject of dependent claims 2 to 16.

[0013] According to the present invention, the method for determining the type mentioned first is - The camera is positioned laterally above the metal strip, - The evaluation means determines the value of one coordinate as a function of the other coordinate in the two-dimensional coordinate system associated with each image for the operator-side strip end and the drive-side strip end, thereby determining the characteristics of each strip end as a function of the other coordinate in each image. - The evaluation means uses the functional properties of each strip end within each evaluation range of the image to determine the measured amount for the edge curvature of each strip end. It is designed in [location / location].

[0014] The phrase "positioned laterally above the metal strip" restricts the camera's placement in two ways. Firstly, the camera must be positioned above the metal strip so that, when viewed vertically, the captured image shows the upper side of the metal strip. Secondly, the camera must be positioned so that, when viewed in the width direction, the operator-side strip end is positioned between the camera and the drive-side strip end. Therefore, the camera is not positioned on top of the metal strip. If the camera is positioned on top of the metal strip but not laterally above it, then when viewed in the width direction, the camera will be positioned between the two strip ends.

[0015] The camera's placement affects the surroundings that can be captured by the camera and recognized by the captured image. Specifically, in an image captured by the method according to the present invention, the value of one coordinate depends on the height of the corresponding strip end for the specific value of the other coordinate. On the other hand, if the camera is placed on a metal strip, the value of one coordinate will not depend on the height of the corresponding strip end at this location, or will depend on it only slightly.

[0016] The worker-side strip end determined in the image is the lower strip end on this side of the metal strip. The upper worker-side strip end is depicted in the image, but is generally not recognizable. The drive-side strip end determined in the image is the upper strip end on this side. The lower drive-side strip end is itself hidden by the metal strip in the image.

[0017] The captured images are two-dimensional. These images can be "ordinary" optical images, that is, they can be captured in the visible spectrum or infrared. Infrared images are particularly suitable when metal strips are hot-rolled in a rolling stand. However, the determination method according to the present invention is applicable not only to the hot-rolling of metal strips but also to the cold-rolling of metal strips.

[0018] The determination method according to the present invention can be used in various ways. For example, the determination method according to the present invention can be integrated into a flatness control system in the same manner as in Patent Document 1. In this case, the determination method must be executed in real time. The evaluation means in this case is itself a control means for a rolling stand, or is connected to such a control means via a data link. Alternatively or additionally, the determination method according to the present invention may be incorporated into the adaptation of a model from which setting calculations for subsequent rolling of a metal strip are obtained. In this case, real-time execution is not required. Alternatively or additionally, the evaluation means can communicate with an operator. For example, the evaluation means can output the measurement values determined for edge wrinkling at the strip end, specifically in a visualized form, to the operator. The evaluation means can also output visual, auditory, and / or other types of warnings to the operator when, for example, a threshold value is exceeded.

[0019] Preferably, the direction of the other coordinate of the coordinate system extends substantially in the transport direction. This design facilitates image evaluation. The term "substantially" is intended to mean a maximum deviation of 5° in the direction of the other coordinate from the transport direction.

[0020] In principle, the pixels of each image form an orthogonal constant grid having two mutually orthogonal preferential directions. Preferably, the other coordinate of the coordinate system substantially coincides with one of these two preferential directions. This design likewise facilitates image evaluation. As mentioned above, the term "substantially" is intended to mean a maximum deviation of 5° of the other coordinate from the preferential direction.

[0021] In the simplest case, the evaluation range of the evaluation means is predetermined by a fixed method. Alternatively, the evaluation means can receive the evaluation range from an operator. This design is simple but very flexible. In still another design, the evaluation means automatically determines the evaluation range based on a received image. In this case, on the one hand, the evaluation range can be optimized by a flexible method, and on the other hand, an operator is relieved from the task of making an accurate determination. Regardless of which procedure is used, an appropriate specification of the evaluation range allows for possible breaking effects that occur in the front region and the rear region of a metal strip to be pressed.

[0022] When the evaluation range is automatically determined, for this purpose, the evaluation means: - determining a provisional lower limit and / or a provisional upper limit for the other coordinate, and for a plurality of images and for each strip edge, determining the scattering or variance of a characteristic of each function in the direction of one coordinate between the provisional lower limit and the provisional upper limit; - changing the provisional lower limit and / or the provisional upper limit, and for the plurality of images, re-determining the scattering or variance of the characteristic of each function in the direction of one coordinate within the changed provisional lower limit and provisional upper limit; - based on a change in the scattering or variance of the characteristic of each function in the direction of one coordinate, determining in which direction the provisional lower limit and / or the provisional upper limit should be changed again, or definitively adopting the provisional lower limit and / or the provisional upper limit as the upper limit and / or lower limit is preferably provided.

[0023] In a simple design, the evaluation means individually determines a measurement value for edge waving of each strip edge for an image. Therefore, the measurement value for edge waving of each strip edge is determined for each individual image independently of other images. This type of evaluation is particularly useful specifically for the head of the strip, and potentially also useful for the tail of the strip, that is, when the metal strip is not subjected to tension.

[0024] In the case of evaluating individual images, for example, the evaluation means can determine the position spectrum of the functional characteristics of each strip end in each image for the purpose of determining the measured amount of edge undulation at each strip end, and evaluate the determined position spectrum. For example, the evaluation means can determine the maximum amplitude and its position frequency, or the amplitude above a threshold and the associated position frequency. The determination of the position spectrum can be obtained, for example, by using the local Fourier transform, specifically the FFT (Fast Fourier Transform).

[0025] As an alternative to evaluating each image individually, the evaluation means can utilize a sequence of captured images of the metal strip for the purpose of determining the amount of measurement for edge undulation at each strip end. This type of evaluation is particularly advantageous when the metal strip is subjected to tension. In this case, edge waves may appear, depending on the extent of the tension. Generally, the images in the evaluated sequence are directly following each other; therefore, unrecorded images are skipped. However, this is possible on a case-by-case basis.

[0026] For the purpose of evaluating the overall sequence of images, it is advantageous if the characteristics of the strip ends can be directly compared for each image. Therefore, it is preferable that the evaluation means, for the purpose of evaluating the characteristics of the function of each strip end in a sequence of images, for each image, determines the average value of the characteristics of each function in one coordinate direction within the evaluation range of each image, subtracts the determined average value from the characteristics of the function of each strip end determined in each image, thereby determining the modified characteristics of the function of each strip end in each image, and performs a further evaluation of the sequence of images based on the modified characteristics.

[0027] In many cases, good results are obtained when further evaluation involves a statistical assessment of the modified properties of each strip end in the sequence images. This is especially true when the statistical evaluation involves determining the statistical variables of the properties of each modified function in the direction of one coordinate system by positional decomposition in the other coordinate system.

[0028] For example, the mean, spread, variance, and similar variables of the modified characteristics of each strip end can be determined for a sequence of images with respect to specific values ​​of the other coordinate. For instance, the evaluation means can determine the measured quantities for the end undulation of each strip end from the spread or variance with respect to specific values ​​of the other coordinate, or from the properties of the function of the spread or variance as a function of the other coordinate. Alternatively or additionally, the evaluation means can determine the measured quantities for the end undulation of each strip end from the properties of the function of the mean as a function of the other coordinate. This evaluation can be performed in the same manner as previously described for a single image.

[0029] As an alternative to statistical evaluation, the evaluation means can determine the measured quantity for the edge undulation of each strip end by evaluating the change over time in the direction of one coordinate system across a sequence of images of the modified function characteristics of the strip ends, based on positional decomposition in the other coordinate system.

[0030] To this end, the evaluation means can specifically determine the time spectrum of the change over time in one coordinate direction and evaluate the time spectrum. For example, the control means can determine the maximum amplitude and its frequency, or the amplitude above a threshold and the associated frequency. The time spectrum can be determined, for example, by using the time Fourier transform, specifically the FFT (Fast Fourier Transform).

[0031] Preferably, the evaluation means accepts changes in the measured quantity for the undulation of each strip end as valid only if these changes persist over a period longer than the shortest possible time period. Thus, short-term fluctuations and interferences can be easily filtered out.

[0032] Preferably, the evaluation means determines the camera movement while capturing the image and corrects the position of each coordinate system in the captured image by the camera movement before determining the function properties of each strip end. Thus, the main cause of error can be eliminated.

[0033] For the purpose of determining the camera's movement, the camera may be equipped with, for example, an acceleration sensor and / or a rotation sensor. In this case, the evaluation means can receive the corresponding sensor signals and use those sensor signals to determine the camera's movement. It is also possible for the evaluation means to know the location of a fixed structure that should be present in the captured image. In this case, the evaluation means can determine at what point in the captured image the fixed structure is located and from there determine the camera's movement. The fixed structure may be, for example, a stand support of a rolling stand, or a downstream rolling stand or element positioned on the stand support. A sling lifter may be considered a “fixed structure” if its current position is known by the evaluation means.

[0034] The objective is further achieved by a computer program having the features of claim 17. According to the present invention, the processing of machine code by the evaluation means causes the evaluation means to perform the determination method according to the present invention.

[0035] The objective is further achieved by an evaluation means having the features of claim 18. According to the present invention, the evaluation means is programmable by software and is programmed with a computer program according to the present invention to perform the method of determination according to the present invention.

[0036] The objective is further achieved by a rolling means having the features of claim 19. According to the present invention, in the case of the type of rolling means first mentioned, the camera is positioned laterally above the path line through which the metal strip travels out of the rolling stand, and the evaluation means is implemented as an evaluation means according to the present invention and performs a method of determination according to the present invention.

[0037] In many cases, the rolling means has a further rolling stand positioned on the exit side of the first-mentioned rolling stand. In this case, the camera is preferably positioned between the first-mentioned rolling stand and the further rolling stand when viewed in the direction of transport of the metal strip. Thus, the camera preferably "views" the metal strip substantially from the side. This results in capturing the ends of the strip with particularly high quality on the one hand, and on the other hand, ease of evaluation.

[0038] Furthermore, the camera is preferably positioned such that the operator-side connection line from the camera to the operator-side strip end forms an operator-side angle between 30° and 70° with respect to the operator-side vertical plane containing the operator-side strip end, and / or the drive-side connection line from the camera to the drive-side strip end forms a drive-side angle between 30° and 70° with respect to the drive-side vertical plane containing the drive-side strip end. At angles less than 30°, the end waves are only poorly visible in the captured image. At angles greater than 70°, it becomes increasingly difficult to distinguish between the two strip ends.

[0039] The features, characteristics, and advantages of the present invention described above, and the methods by which they are achieved, will become clearer and more understandable in the context of the following description of exemplary embodiments, which are described in more detail together with the drawings. [Brief explanation of the drawing]

[0040] [Figure 1] This is a side view of the rolling mechanism. [Figure 2]This is a view from above of the rolling mechanism from Figure 1. [Figure 3] This is a diagram of the rolling mechanism from Figure 1, as viewed from the opposite direction of the metal strip's transport. [Figure 4] This is a sequence diagram. [Figure 5] This is a sequence diagram. [Figure 6] This is a diagram showing an image and its contents. [Figure 7] This is a sequence diagram. [Figure 8] This is a diagram of the position spectrum. [Figure 9] This is a sequence diagram. [Figure 10] This is a diagram of the frequency distribution. [Figure 11] This diagram shows the changed values ​​in the direction of one coordinate when the other coordinate is a constant value. [Figure 12] This is a diagram showing the determination and evaluation of the time spectrum. [Figure 13] This is a sequence diagram. [Figure 14] This is a sequence diagram. [Figure 15] This is a sequence diagram. [Figure 16] This is a diagram showing an image and its contents. [Modes for carrying out the invention]

[0041] As shown in Figures 1 to 3, a metal strip 2 is rolled on a rolling stand 1. Only the work rollers of the rolling stand 1 are depicted in Figures 1 to 3. However, as a rule, the rolling stand 1 has additional rollers in addition to the work rollers, specifically support rollers. The metal strip 2 extends in the width direction yB over the strip width b. On one side, there is an upper worker-side strip end 3 and a lower worker-side strip end 4. On the other side, there is an upper drive-side strip end 5 and a lower drive-side strip end 6. The metal strip 2 moves out of the rolling stand 1 in the transport direction xB. In many cases, there are other rolling stands 7 in addition to the rolling stand 1. If additional rolling stands 7 exist, they are located on the output side of the rolling stand 1. Of the rolling stands 7, only the work rollers are depicted in Figures 1 and 2. As a rule, additional rolling stands 7 also have additional rollers in addition to the work rollers, specifically support rollers.

[0042] There is also camera 8. As shown in Figures 1 to 3, camera 8 is positioned laterally above the path line in which the metal strip 2 moves out of the rolling stand 1. Thus, camera 8 "views" the metal strip 2 from above and the side. The dashed line extending from camera 8 is intended to indicate the camera's capture range. The capture range is selected so that both the two operator-side strip ends 3 and 4 and the upper drive-side strip end 5 are within the capture range.

[0043] A worker-side connection line 9 from camera 8 to the (downward) worker-side strip end 4 forms a worker-side angle α1 with the worker-side vertical plane 10. The worker-side vertical plane 10 is defined by including the (downward) worker-side strip end 4 and being vertical. Preferably, camera 8 is positioned such that the worker-side angle α1 is between 30° and 70°. Strictly speaking, the worker-side angle α1 varies over the capture range in which the worker-side strip end 4 is captured. The maximum, minimum, or arithmetic mean of the worker-side angle α1 may be used as the worker-side angle α1 as needed.

[0044] Similarly, the drive-side connection 11 from the camera 8 to the (upper) drive-side strip end 5 forms a drive-side vertical plane 12 and a drive-side angle α2. The drive-side vertical plane 12 is defined by including the (upper) drive-side strip end 5 and being vertical. Preferably, the camera 8 is positioned such that the drive-side angle α2 is between 30° and 70°. Similar to the operator-side angle α1, the operator-side angle α2 also varies over the capture range in which the drive-side strip end 5 is captured. The maximum, minimum, or arithmetic mean of the drive-side angle α2 may be used as the drive-side angle α2 as needed. However, in any case, the drive-side angle α2 is greater than the operator-side angle α1.

[0045] If additional rolling stands 7 are present, the camera 8 is generally positioned between rolling stand 1 and the additional rolling stand 7, when viewed in the direction xB of transport of the metal strip 2.

[0046] As shown in Figure 1, camera 8 is connected to evaluation means 13 via a data link. This allows camera 8 to transmit captured image B to evaluation means 13. Evaluation means 13 receives and evaluates captured image B. As indicated by the symbol "μP", evaluation means 13 is programmable by software. Evaluation means 13 is programmed with a computer program 14, which further includes machine code 15. Machine code 15 can be processed directly by evaluation means 13. Processing of machine code 15 by evaluation means 13 causes evaluation means 13 to perform a determination method, which is first described in conjunction with Figure 4 and later in more detail, and then in conjunction with other figures.

[0047] As shown in Figure 4, in step S1, the evaluation means 13 receives image B of the metal strip 2 captured by the camera 8 from the camera 8.

[0048] In step S2, the evaluation means 13 checks whether the sequence of images B already received and stored in the evaluation means 13 has already been completed.

[0049] As long as the sequence is still incomplete, the evaluation means 13 proceeds to step S3. In step S3, the evaluation means 13 adds image B received in step S1 to the sequence. Next, the evaluation means 13 returns to step S1.

[0050] As soon as the sequence is complete, the evaluation means 13 proceeds to step S4. In step S4, the evaluation means 13 removes the oldest image B from the sequence. Next, in step S5, the evaluation means 13 adds the image B received in step S1 to the sequence. At this point, the sequence is completed again, but it has been updated by one cycle.

[0051] In the subsequent step S6, the evaluation means 13 evaluates image B from the sequence of image B. In step S6, the evaluation means 13 determines a measured amount M1 for the end undulation of the lower operator-side strip end 4 and a measured amount M2 for the end undulation of the upper drive-side strip end 5. Step S6 is the actual core subject of the present invention, which will be described in detail later.

[0052] In the subsequent step S7, the evaluation means 13 performs further actions, such as visualizing the results of step S6 or sending a message to the control means that controls the rolling stand 1. The control means is not depicted in the figure. From step S7, the evaluation means 13 returns to step S1.

[0053] Therefore, the evaluation means 13 repeatedly executes the sequence of steps S1 to S7, specifically by repeatedly receiving each image B and evaluating each image B in each sequence. The cycle time can correspond to frequencies within the range of standard video frequencies, and therefore can correspond to images B between 20 and 80 frames per second, specifically between 30 and 60 frames per second. For example, in the case of capturing 25 images per second, the cycle time is 40 ms.

[0054] In step S6, as shown in Figure 5, the evaluation means 13 initially selects one of the images B from the sequence of images B in step S11.

[0055] In step S11, for the selected image B, in step S12, the evaluation means 13 determines the coordinates x and y of the coordinate system. Thus, the evaluation means 13 defines the coordinate system for the selected image B. The coordinate system is two-dimensional and relates to each image B, as shown in Figure 6. In the simplest case, the coordinate x extends along the longitudinal direction of image B, and the coordinate y extends perpendicular to image B.

[0056] Figure 6 shows two preferred designs simultaneously. One preferred design is that the direction of the x-coordinate (the "other coordinate" in the sense of the claims) substantially extends in the direction xB of transport of the metal strip 2. Secondly, each individual pixel of each image B generally forms a constant orthogonal raster. Thus, the raster has two mutually orthogonal preferred directions. The other preferred design is that the x-direction coincides with one of these two preferred directions, and as a result, the y-direction coincides with the other of these two preferred directions.

[0057] In step S11, for the image B selected, in step S13, the evaluation means 13 determines the representations K1 and K2 of the strip ends 4 and 5. For example, if the metal strip 2 is being hot-rolled on the rolling stand 1 and the camera 8 is a thermal or infrared camera, the evaluation means 13 can determine the sharp transitions from small to large intensity values ​​in image B and determine each transition as the representations K1 and K2 of the strip ends 4 and 5. Corresponding methods for determination for end detection are generally known to those skilled in the art. Figure 6 shows the determined representations K1 and K2 using purely illustrative examples. Naturally, the representations K1 and K2 can also have different characteristics of the strip ends 4 and 5.

[0058] In step S14, the evaluation means 13 determines the value of one coordinate y as a function of the other coordinate x for the worker-side strip end 4 or its representation K1. Therefore, in step S14, the evaluation means 13 determines, with respect to image B and the coordinate system, the characteristics of each strip end 4 or its representation K1 as a function of coordinate x with respect to image B. K1: y=f1(x)

[0059] In step S15, the evaluation means 13 performs the same procedure for the drive-side strip end 5 or its representation K2. K2: y=f2(x)

[0060] Next, in step S16, the evaluation means 13 uses the characteristics of the functions of each strip end 4, 5 or the corresponding representations K1, K2 to determine the measured quantities M1, M2 for the end curvature of each strip end 4, 5. In this case, the evaluation means 13 evaluates the characteristics of each function only within each evaluation range 16 of image B. To determine the measured quantity M1, the evaluation means 13 uses the characteristics of the function of representation K1, and to determine the measured quantity M2, the evaluation means 13 uses the characteristics of the function of representation K2.

[0061] In the following, only the operator-side strip end 4, the associated function characteristics for expression K1, and the resulting measured quantity M1 are considered in the overall explanation. For the drive-side strip end 5, the associated function characteristics for expression K2, and the resulting M2, a similar overall explanation applies in each case.

[0062] In some cases, the evaluation means 13 individually determines a measured quantity M1 for the end undulation of the worker-side strip end 4, i.e., for each image B. For example, in step S21, as shown in Figure 7, the evaluation means 13 can select one of the images B. Next, in step S22, the evaluation means 13 determines the position spectrum SPA of the function characteristics of the worker-side strip end 4 or its representation K1. Figure 8 shows an example of a possible position spectrum SPA. To determine the dimension M1, in step S23, the evaluation means 13 evaluates the spatial spectrum SPA. For example, as depicted in Figure 8, the evaluation means 13 can determine the maximum amplitude AA and the associated position frequency fA in the spatial spectrum SPA, and these two values ​​can be used to determine the measured quantity M1. The measured quantity M1 depends at least on the maximum amplitude AA, and as the maximum amplitude AA increases, the measured quantity also increases. The dependence on the associated position frequency fA is usually smaller. Other types of evaluation are also possible.

[0063] However, as a general rule, the evaluation means 13 utilizes a sequence of captured images B of the metal strip 2 to determine a measured amount M1 for the end curvature of the strip end 4. When a sequence of captured images B is used, the contents of the images B must be comparable to each other. Modified characteristics are determined in a preliminary procedure to enable or allow visualization of the functional characteristics of the images B, or the operator-side strip end 4 or their respective representations K1 contained in the images B. This procedure is described below in conjunction with Figure 9.

[0064] As shown in Figure 9, in step S31, the evaluation means 13 selects one of the images B in the sequence. In step S32, the evaluation means 13 determines the mean value yM of the function properties of the operator-side strip end 4 or each representation K1 within the evaluation range 16 of this image B. Thus, this is done by taking the y values ​​that result for various x values, adding them together, and dividing the sum by the number of x values. The mean value yM for representation K1 is also plotted in Figure 6. In step S33, the evaluation means 13 determines the modified function properties of the operator-side strip end 4 in each image B by subtracting the mean value yM determined in step S32 from the y values. The y values ​​of the modified function properties are shown below by the reference indicator y'.

[0065] In step S34, the evaluation means 13 checks whether steps S31 to S33 have already been performed for all images B in the sequence. If not, the evaluation means 13 returns to step S31. In the re-execution of step S31, the evaluation means 13 selects one of the images B in the sequence for which steps S32 and S33 have not yet been performed. If not, preparation is complete. Thus, in step S35, the evaluation means 13 can perform further evaluation of the sequence of images B based on the modified characteristics, and specifically, can determine the measured quantity M1.

[0066] Various possible designs for step S35 are described below.

[0067] For example, as shown in Figures 10 and 11, step S35 may provide a statistical evaluation of the modified characteristics of the operator-side strip end 4. Specifically, the evaluation means 13 can perform a statistical evaluation of the y' values ​​that occur at a given x-coordinate x0 of image B. Figure 10, purely as an example, shows the possible frequency distribution H of y' values ​​across the sequence of image B for a given x0. Figure 11 shows the y' values ​​that occur for a given x0. For example, the mean value of the y' values ​​for a given x0 and the dispersion or variance of this mean value may be used as statistical variables. The evaluation means 13 can perform decisions for multiple given x0s separately from each other. This allows for a positional decomposition of the statistical evaluation in the x-direction.

[0068] Therefore, the evaluation means 13 determines the measured quantity M1 based on the determined statistical value. For example, if the dispersion or variance is greater, the measured quantity M1 may be greater. The mean may be used and evaluated in a similar manner to the mean in Figures 7 and 8.

[0069] As an alternative to statistical evaluation, evaluation means 13 can perform a time-based evaluation of the y' value that occurs at a constant x-coordinate x0 of image B. For example, evaluation means 13 may evaluate the change over time of the y' value for a constant value x0 over a sequence of image B. Figure 12 shows an example of possible time-based properties of the y' value for a specific constant value x0. For example, as also depicted in Figure 12, evaluation means 13 can determine the time spectrum SPB of the change over time of the y' value. The determination of the time spectrum SPB is indicated in Figure 12 by the letters "FOU" for the Fourier transform.

[0070] For example, the evaluation means 13 can determine the maximum AB in the time spectrum SPB and the associated time frequency fB, and can determine the measured quantity M1 based on these two values. The measured quantity M1 depends at least on the maximum amplitude AB, and as the maximum amplitude AA increases, the measured quantity also increases. The dependence on the associated time frequency fB is usually smaller. Other types of evaluation are also possible.

[0071] The evaluation means 13 can perform time-based evaluations separately for multiple constant values ​​x0, such as the types of evaluations depicted in Figure 12. Therefore, the determination can be made by positional decomposition in the x-coordinate. Next, based on the determination of the time-based characteristics, or based on the time-based characteristics and positional decomposition, the evaluation means 13 can determine the measured amount M1 for the end curvature of the worker-side strip end 4.

[0072] Various procedures for determining the measured quantity M1 have been described above for the operator-side strip end 4 and the characteristics of the associated function for representation K1. As already mentioned, a similar general description applies to the drive-side strip end 5 and to the characteristics of the associated function for representation K2 and the resulting determined dimension M2, in their respective cases.

[0073] As previously explained in relation to Figure 4, dimensions M1 and M2 are determined repeatedly. Therefore, the determined values ​​for the measured quantities M1 and M2 may change over time. The evaluation means 13 can immediately accept the newly determined values ​​as valid. However, preferably, the evaluation means 13 proceeds as described below in relation to Figure 13.

[0074] As shown in Figure 13, the evaluation means 13 determines dimensions M1 and M2 in step S41. Step S41 essentially corresponds to the sequence of steps S1 to S7 in Figure 4.

[0075] In step S42, the evaluation means checks whether there has been a change in the measured quantities M1 and M2. If not, the evaluation means 13 returns to step S41. If not, in step S43, the evaluation means 13 checks whether the change in the measured quantities M1 and M2 has already occurred for a predetermined period T. If not, the evaluation means 13 returns to step S41. If not, the evaluation means 13 returns to step S41. Alternatively, in step S44, the evaluation means 13 accepts the changed measured quantities M1 and M2 as valid. Only when step S44 is performed, the changed measured quantities M1 and M2 are used and output, for example, to operator 17 (see Figure 1). From step S44, the evaluation means 13 returns to step S41 again.

[0076] The evaluation range 16 should be clearly defined. In its simplest form, the evaluation range 16 of the evaluation means 13 can be determined by a fixed method, for example, by defining a lower limit x1 and an upper limit x2. The limits x1 and x2 are shown in Figure 6. Alternatively, the evaluation means 13 can receive the evaluation range 16 or its limits x1 and x2 from the operator 17. Similarly, the evaluation means 13 can automatically determine the evaluation range 16 based on the received image B. Possible procedures for this are described below in conjunction with Figure 14.

[0077] As shown in Figure 14, in step S51, the evaluation means 13 defines the evaluation range 16 by setting a lower limit x1 and / or an upper limit x2. The definition of step S51 is only provisional.

[0078] In step S52, the evaluation means 13 determines the dispersion or variance of the function characteristics in the y-direction for the operator-side strip end 4 for multiple images B within a defined evaluation range 16, usually for all images B in a sequence that have been evaluated consecutively. In step S53, the evaluation means 13 determines the dispersion or variance for the drive-side strip end 5 using a similar method.

[0079] In step S54, the evaluation means 13 changes the lower limit x1 and / or upper limit x2. In the subsequent step S55, the evaluation means 13 again determines the dispersion or variance of the operator-side strip end 4 and the drive-side strip end 5 for the evaluation range 16 which is now being changed. Step S55 corresponds to a combination of steps S52 and S53, except that it is performed for the changed evaluation range 16.

[0080] In step S56, the evaluation means 13 determines the change in scattering or dispersion separately for the operator-side strip end 4 and the drive-side strip end 5. Depending on the change, in step S57, the evaluation means 13 decides whether to return to step S54 and consequently change the lower limit x1 and / or upper limit x2, or to proceed to step S58. In step S58, the evaluation means 13 finally adopts the most recently determined values ​​for the lower limit x1 and / or upper limit x2. Step S58 concludes the determination of the evaluation range 16.

[0081] The verification in step S57 may specifically include the degree to which the dispersion or variance is changed. For example, if a large evaluation range 16 is selected in step S51 and then gradually decreased, the evaluation means 13 may proceed to step S58 if the change in dispersion or variance becomes sufficiently small. Conversely, if a small evaluation range 16 is selected in step S51 and then gradually increased, the evaluation means 13 may proceed to step S58 if the change in dispersion or variance becomes too large.

[0082] Camera 8 may vibrate during operation, and consequently when capturing image B. Such vibrations affect the captured image B. Therefore, preferably, the procedure in Figure 4 is modified as shown in Figure 15.

[0083] As shown in Figure 15, in step S61, the evaluation means 13 receives image B of the metal strip 2 captured by the camera 8 from the camera 8. Step S61 corresponds to step 1 in Figure 4.

[0084] In step S62, information I about the movement of camera 8 is provided to the evaluation means 13. Information I originates, for example, from a sensor (not depicted) located on camera 8. In this case, the evaluation means 13 receives information I from the sensor. Alternatively, information I can be extracted by the evaluation means 13 from image B received in step S61. A combination of these two steps is also possible.

[0085] In step S63, the evaluation means 13 uses information I to determine the movement of the camera 8 when capturing the image B received in step S61. In step S64, the evaluation means 13 corrects the position of the coordinate system in the image B received in step S61. Figure 16 shows an example of possible positions of the coordinate system after correction made by the evaluation means 13.

[0086] Next, the evaluation means 13 proceeds to step S65. Step S65 corresponds to the entirety of steps S2 to S7 in Figure 4. From step S65, the evaluation means 13 returns to step S61.

[0087] The present invention has many advantages. Specifically, it allows for simple and robust evaluation. Error-prone evaluation of periodic intensity changes is not required. Instead, transitions from non-strip to strip and from strip to non-strip need to be recognized. The camera 8 does not need to be positioned on the metal strip 2. Lateral (only) positioning above the metal strip 2 is even more advantageous.

[0088] Although the present invention is illustrated and described in more detail by preferred embodiments, the present invention is not limited by the examples disclosed, and other modifications may be derived from those examples by those skilled in the art without departing from the scope of protection of the present invention. [Explanation of Symbols]

[0089] 1.7 Rolling stand 2 metal strips 3-6 Strip ends 8 cameras 9, 11 connecting lines 10, 12 Vertical plane 13. Evaluation methods 14 Computer Programs 15 Machine Codes 16. Evaluation Scope 17 Workers AA, AB amplitude b Strip width Image B fA position frequency fB Time Frequency H frequency distribution I Information K1, K2 expression M1, M2 measured values S1~S65 Step SPA, SPB spectrum T duration xB Direction of transport x0 is a constant value yB width direction x, y coordinates x1, x2 limit y' value yM average value α1, α2 angle

Claims

1. A method for determining the end curvature of a metal strip (2) that extends in the width direction (yB) over the strip width (b) from the worker-side strip end (4) to the drive-side strip end (5), and that moves outward from the rolling stand (1) in the transport direction (xB), In a determination method in which the evaluation means (13) repeatedly receives an image (B) of the metal strip (2) captured by the camera (8) from the camera (8), The camera (8) is positioned laterally above the metal strip (2), The evaluation means (13) determines, with respect to the operator-side strip end (4) and the drive-side strip end (5), the value of one coordinate (y) as a function of the other coordinate (x) in the two-dimensional coordinate system associated with each image (B), thereby determining the characteristics of each strip end (4, 5) as a function of the other coordinate (x) in each image (B). The evaluation means (13) uses the characteristics of the function of each strip end (4, 5) within each evaluation range (16) of the image (B) to determine the measured amounts (M1, M2) for the end curvature of each strip end (4, 5) and A decision-making method characterized by the following.

2. The method for determining the coordinates according to claim 1, characterized in that the direction of the other coordinate (x) of the coordinate system substantially extends in the direction of transport (xB).

3. The method for determining according to claim 1 or 2, characterized in that each pixel of the image (B) forms a constant orthogonal grid having two mutually orthogonal preferred directions, and the other coordinate (x) of the coordinate system substantially coincides with one of these two preferred directions.

4. The method for determining the evaluation range (16) of the evaluation means (13) is predetermined by a fixed method, or the evaluation means (13) receives the evaluation range (16) from the worker (17), as described in any one of claims 1 to 3.

5. The method for determining the evaluation range (16) according to any one of claims 1 to 3, characterized in that the evaluation means (13) automatically determines the evaluation range (16) based on the received image (B).

6. The evaluation means (13) is used for the purpose of automatically determining the evaluation range (16), A provisional lower limit (x1) and / or provisional upper limit (x2) are determined for the other coordinate (x), and for each of the multiple images (B), the dispersion or variance of the characteristics of each of the functions in the direction of the one coordinate (y) is determined between the provisional lower limit (x1) and the provisional upper limit (x2) for each of the strip ends (4, 5), The provisional lower limit (x1) and / or the provisional upper limit (x2) are changed, and with respect to the plurality of images (B), the dispersion or variance of the characteristics of each of the functions in the direction of one of the coordinates (y) is determined again within the changed provisional lower limit (x1) and provisional upper limit (x2). The method for making a determination according to claim 5, characterized in that, based on the change in the dispersion or variance of the characteristics of each of the functions in the direction of one of the coordinates (y), it is determined in which direction to change the provisional lower limit (x1) and / or the provisional upper limit (x2) again, or to definitively adopt the provisional lower limit (x1) and / or the provisional upper limit (x2) as the upper limit (x1) and / or lower limit (x2).

7. The method for determining the measurement according to any one of claims 1 to 6, characterized in that the evaluation means (13) individually determines the measurement amounts (M1, M2) for the end undulation of each of the strip ends (4, 5) with respect to the image (B).

8. The method for determining the function according to claim 7, wherein the evaluation means (13) determines the position spectrum (SPA) of the function characteristics of each strip end (4, 5) in each image (B) for the purpose of determining the measured amount (M1, M2) of the end undulation of each strip end (4, 5), and evaluates the determined position spectrum (SPA).

9. The method for determining the value according to any one of claims 1 to 6, characterized in that the evaluation means (13) utilizes a sequence of captured images (B) of the metal strip (2) for the purpose of determining the measured amounts (M1, M2) for the end undulation of each of the strip ends (4, 5).

10. The method for determining the function according to claim 9, wherein the evaluation means (13) determines, for each image (B) of the sequence for the purpose of evaluating the characteristics of the function of each strip end (4, 5), the average value (yM) of the characteristics of each function in the direction of one coordinate (y) in the evaluation range (16) of each image (B), subtracts the determined average value (yM) from the characteristics of the function of each strip end (4, 5) determined in each image (B), thereby determining the modified characteristics of the function of each strip end (4, 5) in each image (B), and performs a further evaluation of the sequence of images (B) based on the modified characteristics.

11. The method for determining according to claim 10, wherein the further evaluation includes a statistical evaluation of the modified characteristics of each of the strip ends (4, 5) in the image (B) of the sequence.

12. The method for making a determination according to claim 11, characterized in that the statistical evaluation includes determining the statistical variables of the characteristics of each of the modified functions in the direction of the one coordinate (y) by position decomposition in the other coordinate (x).

13. The method for determining the measurement amount (M1, M2) for the end undulation of each of the strip ends (4, 5), characterized in that the evaluation means (13) determines the change over time in the direction of the one coordinate (y) over a sequence of images (B) of the modified characteristics of the function of the strip ends (4, 5) by position decomposition in the other coordinate (x), the method for determining the measurement amount (M1, M2) for the end undulation of each of the strip ends (4, 5).

14. The method for determining the time spectrum (SPB) of the change over time in the direction of one of the coordinates (y), characterized in that the evaluation means (13) determines the time spectrum (SPB) and evaluates the time spectrum (SPB).

15. The method for determining according to any one of claims 1 to 14, characterized in that the evaluation means (13) accepts the changes in the measured amounts (M1, M2) for the end undulation of each of the strip ends (4, 5) as valid only if these changes persist over a period of time longer than the shortest period of time (T).

16. The method for determining the location of each of the coordinate systems in the captured image (B) according to any one of claims 1 to 15, characterized in that the evaluation means (13) determines the movement of the camera (8) while capturing the image (B), and corrects the position of each of the coordinate systems in the captured image (B) by the movement of the camera (8) before determining the characteristics of the function of each of the strip ends (4, 5).

17. A computer program for a software-programmable evaluation means (13), the computer program comprising machine code (15) that can be directly processed by the evaluation means (13), wherein the processing of the machine code (15) by the evaluation means (13) causes the evaluation means (13) to perform a determination method according to any one of claims 1 to 16.

18. An evaluation means, wherein the die evaluation means is programmable by software and is programmed by using the computer program (14) according to claim 17 to perform the determination method according to any one of claims 1 to 16.

19. A rolling means, The rolling means includes a rolling stand (1) for rolling a metal strip (2) such that the metal strip (2), which extends in the width direction (yB) over the strip width (b) from the worker-side strip end (4) to the drive-side strip end (5), moves out of the rolling stand (1) in the transport direction (xB). The rolling means has a camera (8) positioned laterally above the path line through which the metal strip (2) moves out of the rolling stand (1), The rolling means includes an evaluation means (13) connected to the camera (8) via a data link for the purpose of receiving an image (B) captured using the camera (8), which is implemented as the evaluation means (13) described in claim 18, and performs the method of determination described in any one of claims 1 to 16.

20. The rolling means according to claim 19, wherein the rolling means has a further rolling stand positioned on the exit side of the first-mentioned rolling stand (1), and the camera (1) is positioned between the first-mentioned rolling stand (1) and the further rolling stand (7) when viewed in the direction of transport (xB) of the metal strip.

21. The rolling means according to claim 19 or 20, characterized in that the camera (8) is arranged such that the operator-side connection line (9) from the camera (8) to the operator-side strip end (4) forms an operator-side angle (α1) between 30° and 70° with the operator-side vertical plane (10) including the operator-side strip end (4), and / or the drive-side connection line (11) from the camera (8) to the drive-side strip end (5) forms a drive-side angle (α2) between 30° and 70° with the drive-side vertical plane (12) including the drive-side strip end (5).

Images