Metal plate shape measuring device and metal plate shape measuring method

Abstract

The metal plate shape measuring device according to the present invention is a metal plate shape measuring device for measuring the shape of a moving metal plate, comprising: a measuring unit that measures a point cloud of a measurement area including the surface of the metal plate; and a calculation unit that calculates the position of the boundary of the metal plate from the point cloud measured by the measuring unit, extracts a point cloud of the surface of the metal plate from the point cloud based on the calculated boundary position, and calculates the curved surface of the metal plate from the extracted point cloud of the surface of the metal plate.

Description

Technical Field

[0001] The present invention relates to a metal plate shape measuring device and a metal plate shape measuring method for measuring the shape of a traveling metal plate.

Background Art

[0002] When the shape of a thin steel plate is poor, the thin steel plate meanders in a continuous process line, and contact scratches occur at the widthwise ends of the thin steel plate, which may reduce the yield. In addition, when the thin steel plate breaks during cold rolling, the production efficiency may decrease. Therefore, it is important to manage the shape (or flatness) of the thin steel plate being manufactured well. To manage the shape of the thin steel plate, a shape meter for measuring the shape of the thin steel plate online is required. Against this background, Patent Document 1 proposes a method of measuring the shape of a steel plate by installing a plurality of laser displacement meters below the steel plate.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention was made to solve the above problems, and its objective is to provide a metal plate shape measuring device and a metal plate shape measuring method that can measure the shape of a metal plate at low cost and with high maintainability. [Means for solving the problem]

[0006] The metal plate shape measuring device according to the present invention is a metal plate shape measuring device for measuring the shape of a moving metal plate, comprising: a measuring unit that measures a point cloud of a measurement area including the surface of the metal plate; and a calculation unit that calculates the position of the boundary of the metal plate from the point cloud measured by the measuring unit, extracts a point cloud of the surface of the metal plate from the point cloud based on the calculated boundary position, and calculates the curved surface of the metal plate from the extracted point cloud of the surface of the metal plate.

[0007] The calculation unit may perform the calculation of the boundary position at the measurement cycle of the measurement unit, and the extraction of the point cloud on the surface of the metal plate and the calculation of the curved surface of the metal plate at a cycle longer than the measurement cycle.

[0008] The calculation unit converts the coordinate system of the point cloud measured by the measurement unit from the measurement coordinate system of the measurement unit to the coordinate system of the metal plate, extracts a point cloud within a predetermined range including the point cloud on the surface of the metal plate based on the coordinate system of the metal plate, calculates a histogram of the number of extracted point clouds in the width direction of the metal plate, and sets the position in the width direction of the metal plate where the number of point clouds is greater than a predetermined value as the boundary position in the width direction of the metal plate.

[0009] The calculation unit may apply a low-pass filter at the boundary position in the width direction of the metal plate.

[0010] The calculation unit extracts a point cloud from the surface of the metal plate based on the boundary position in the width direction of the metal plate, divides the extracted point cloud into multiple regions along the longitudinal direction of the metal plate, calculates a quadratic function of the height of the metal plate using the least squares method from the point cloud in each region, with the position in the width direction of the metal plate as a variable, deletes point clouds that are more than a predetermined distance from the calculated quadratic function, divides the remaining point cloud into multiple regions along the longitudinal direction of the metal plate, calculates polar coordinate values ​​in a vertical plane with the position of the measurement unit as the origin for the point cloud in each region, sorts the point cloud by the angle of the calculated polar coordinate values, assigns a point cloud number to each point cloud in the sort order, extracts the point cloud from the point cloud number where the position in the width direction of the metal plate is maximum to the last point cloud number, and uses the extracted point cloud as the point cloud of the surface of the metal plate.

[0011] The present invention relates to a metal plate shape measurement method, which is a metal plate shape measurement method for measuring the shape of a moving metal plate, and includes a measurement step of measuring a point cloud of a measurement area including the surface of the metal plate, and a calculation step of calculating the boundary of the metal plate from the point cloud measured in the measurement step, extracting a point cloud of the surface of the metal plate from the point cloud using the calculated boundary, and calculating the curved surface of the metal plate from the extracted point cloud of the surface of the metal plate. [Effects of the Invention]

[0012] According to the metal plate shape measuring apparatus and metal plate shape measuring method of the present invention, the shape of a metal plate can be measured at low cost and with high maintainability. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a block diagram showing the configuration of a metal plate shape measuring device, which is one embodiment of the present invention. [Figure 2] Figure 2 is a schematic diagram illustrating the configuration of the measuring unit shown in Figure 1. [Figure 3] Figure 3 is a flowchart showing the flow of a metal plate shape calculation process, which is one embodiment of the present invention. [Figure 4]FIG. 4 is a diagram showing an example of a point group in the coordinate system of the measurement unit. [Figure 5] FIG. 5 is a diagram showing an example of a point group in the coordinate system of the metal plate. [Figure 6] FIG. 6 is a diagram showing an example of a point group within a predetermined rectangular parallelepiped region including the point group on the surface of the metal plate. [Figure 7] FIG. 7 is a diagram showing an example of a histogram of the number of point groups in the width direction of the metal plate. [Figure 8] FIG. 8 is a diagram for explaining a method of calculating the lower width boundary value. [Figure 9] FIG. 9 is a diagram showing an example of a point group on the surface of the metal plate. [Figure 10] FIG. 10 is a diagram showing a state in which the point group on the surface of the metal plate is divided into a plurality of regions along the longitudinal direction of the metal plate. [Figure 11] FIG. 11 is a diagram showing the point group on the surface of the metal plate after deleting the point group using a quadratic function. [Figure 12] FIG. 12 is a diagram for explaining a method of calculating the point group on the surface of the metal plate. [Figure 13] FIG. 13 is a diagram showing the point group on the surface of the metal plate after deleting the point group using polar coordinate values. [Figure 14] FIG. 14 is a diagram showing the curved surface on the surface of the steel plate calculated in the embodiment.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, referring to the drawings, the configuration and operation of a metal plate shape measuring device according to an embodiment of the present invention will be described.

[0015] 〔Configuration〕 First, referring to FIGS. 1 and 2, the configuration of a metal plate shape measuring device according to an embodiment of the present invention will be described. FIG. 1 is a block diagram showing the configuration of a metal plate shape measuring device according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing the configuration of the measurement unit 2 shown in FIG. 1.

[0016] As shown in Figure 1, the metal plate shape measuring device 1, which is one embodiment of the present invention, is a device that measures the three-dimensional shape of the surface of a moving metal plate online, and comprises a measuring unit 2 and a calculation unit 3.

[0017] The measurement unit 2 is composed of a three-dimensional shape measuring instrument such as a three-dimensional laser scanner. The measurement unit 2 measures a point cloud representing the three-dimensional shape of the measurement area, including the surface of the moving metal plate, at predetermined measurement intervals, and inputs the measured point cloud data (coordinate values) to the calculation unit 3. Specifically, as shown in Figure 2, the measurement unit 2 is installed above the metal plate S being transported by the transport roll R. The measurement unit 2 measures a point cloud representing the three-dimensional shape of the measurement area, including the surface of the metal plate S, at predetermined measurement intervals, and inputs the measured point cloud data to the calculation unit 3. By installing the measurement unit 2 above the metal plate S as shown in Figure 2, it is not necessary to stop the line when maintaining the measurement unit 2, so the three-dimensional shape of the surface of the metal plate S can be measured with high maintainability.

[0018] Returning to Figure 1, the calculation unit 3 is composed of an information processing device such as a computer, and calculates the curved surface of the metal plate from the point cloud data input from the measurement unit 2 by performing the metal plate shape calculation process described later using the point cloud data input from the measurement unit 2.

[0019] In the metal plate shape measuring device 1 having this configuration, the calculation unit 3 performs the metal plate shape calculation process shown below, making it possible to measure the shape of a metal plate at low cost and with high maintainability. The operation of the calculation unit 3 when performing the metal plate shape calculation process will be explained in detail below with reference to Figures 3 to 10.

[0020] [Metal plate shape calculation process] Figure 3 is a flowchart showing the flow of a metal plate shape calculation process according to one embodiment of the present invention. The flowchart shown in Figure 3 starts when the point cloud data (coordinate values) measured by the measurement unit 2 is input to the calculation unit 3, and the metal plate shape calculation process (hereinafter abbreviated as calculation process) proceeds to step S1. The calculation unit 3 should perform the boundary calculation process in step S1 at the measurement cycle of the measurement unit 2 (e.g., 10 Hz), and perform the surface point cloud extraction process in step S2 and the metal plate curved surface calculation process in step S3 at a longer cycle than the measurement cycle of the measurement unit 2 (e.g., 1 Hz). The calculation accuracy of the boundary calculation process in step S1 increases as the calculation cycle is shortened, so the boundary calculation process in step S1 should be kept as short as possible. On the other hand, since the calculation of curved surfaces is complex, the surface point cloud extraction process in step S2 and the metal plate curved surface calculation process in step S3 are performed at a longer cycle than the measurement cycle of the measurement unit 2.

[0021] In step S1, the calculation unit 3 uses the point cloud data measured by the measurement unit 2 to calculate the boundary of the metal plate S in order to extract the point cloud of the surface of the metal plate S from the point cloud measured by the measurement unit 2 (boundary calculation process). Specifically, first, the calculation unit 3 uses a rotation matrix to transform the coordinates of the point cloud data of the measurement unit 2's coordinate system shown in Figure 4 to the point cloud data of the metal plate S's coordinate system (longitudinal direction: x-axis, width direction: y-axis, height direction: z-axis) shown in Figure 5. The rotation matrix is ​​determined in advance based on the positional relationship between the measurement unit 2 and the metal plate S.

[0022] Next, the calculation unit 3 extracts points from the point cloud after coordinate transformation that are located within a predetermined rectangular parallelepiped region, including the point cloud of the surface of the metal plate S. The predetermined rectangular parallelepiped region is set in advance according to the measurement area of ​​the measurement unit 2. Specifically, an example of a predetermined rectangular parallelepiped region is one in which the length in the longitudinal direction is within the range of 1 to 3 m, the length in the width direction is slightly larger than the width of the transport roll R, and the length in the height direction is within the range of ±200 mm of the pass line so that the metal plate S remains within the rectangular parallelepiped region even if the metal plate S undergoes out-of-plane deformation, and the lower limit position of the transport roll R is not included. An example of the extracted point cloud located within the predetermined rectangular parallelepiped region, including the point cloud of the surface of the metal plate S, is shown in Figure 6. The point cloud shown in Figure 6 includes a point cloud that represents a part of the transport roll R shown in Figure 2. In addition, noise originating from the measurement principle exists near the widthwise end of the metal plate S (the right end of the metal plate S shown in Figure 2(b)) (around y < -1.6), which is far from the position of the measurement unit 2. Therefore, in order to extract the point cloud of the metal plate S from the point cloud shown in Figure 6, it is necessary to remove unnecessary point clouds and noise.

[0023] In the top view (point cloud projected onto the xy plane), if the metal plate S is tilted, the accuracy in subsequent processing will be reduced. Therefore, the tilt angle of the metal plate S can be calculated, and the point cloud can be rotated around its centroid using the tilt angle to make the metal plate S appear straight. In this case, the tilt angle of the metal plate S is the tilt angle of the edge of the metal plate S closest to the measurement unit 2. Specifically, in the top view, the point cloud of the metal plate S in a certain range not on the roll is divided into regions along the longitudinal direction, and the point closest to the measurement unit 2 within each region is found. These points are the edges of the metal plate S closest to the measurement unit 2, so the tilt angle is calculated using the least squares method, assuming the edges are straight. Since the noise in the tilt angle is large, the noise can be removed using a low-pass filter. The tilt angle of the metal plate S can also be saved as positional information of the metal plate S.

[0024] Next, the calculation unit 3 calculates a histogram of the number of points in the width direction of the metal plate S, as shown in Figure 7. Then, for the side closer to the measurement unit 2, the calculation unit 3 calculates the smallest y-coordinate value (indicated by the arrow) for which the frequency of the histogram is equal to or greater than a predetermined value (the value of the solid line in the figure), and uses this as the coordinate value (upper width boundary value) of one end (one boundary position) in the width direction of the metal plate S. For the side further from the measurement unit 2, the calculation unit 3 finds the largest y-coordinate value for which the frequency of the histogram is equal to or greater than a predetermined value, and the smallest y-coordinate value (indicated by the arrow) for which the frequency of the histogram is equal to or greater than a predetermined value. Then, the calculation unit 3 calculates the y-coordinate value with the shorter distance between this value and the coordinate value (lower width boundary value) of the other end (other boundary position) in the width direction of the metal plate S calculated in the previous calculation process, and uses this value as the lower width boundary value in the current calculation process.

[0025] However, this method may result in calculating a lower width boundary value that is too small. For example, as shown in Figure 8, if positions where the histogram frequency is above a predetermined value are shown in gray, and positions where the histogram frequency is below a predetermined value are shown in white, then if there are positions below the predetermined value within positions where the histogram frequency is above the predetermined value, an incorrect lower width position A will be calculated. On the other hand, if we define the lower width position B as the position just before the first position below the predetermined value appears when searching the histogram frequency from right to left on the drawing, then both lower width positions A and B could be lower width boundary values, but in some cases both could be incorrect lower width boundary values. Therefore, we may define the lower width position C as the lower width position from which the error has been removed by the lowbus filter calculated in the previous calculation (described later), and set the median of lower width positions A, B, and C as the lower width boundary value. With this method, if both lower width positions A and B are incorrect, lower width position C will be selected, making it easier to calculate the correct lower width boundary value. Furthermore, we may set the median of the lower width position that is the median of the lower width positions A, B, and C from the previous two calculations and the current calculation as the lower width boundary value. This makes it less likely for the suddenly changing width position to be selected.

[0026] Due to the measurement principle, the error in the lower width boundary value, which is the boundary value on the side farther from the measurement unit 2, becomes large. Therefore, it is advisable to remove the error in the lower width boundary value using a low-pass filter. Specifically, the calculation unit 3 should calculate the lower width boundary value using the following formula (1) for each measurement cycle. This completes the process of step S1, and the calculation process proceeds to the process of step S2.

[0027]

number

[0028] y is the width lower boundary value calculated from the histogram, y n is the width lower boundary value after error removal in the previous calculation process, y n+1 The value shown represents the lower boundary value of the width after error removal in this calculation process. α is a real number between 0 and 1; a smaller α makes error removal easier, but it introduces a time delay, making it difficult to respond to meandering fluctuations and changes in plate width of the metal plate S. Half the sum of the upper and lower boundary values ​​is the amount of meandering of the metal plate S, and the difference between the upper and lower boundary values ​​is the plate width of the metal plate S. The amount of meandering of the metal plate S may be stored as positional information for the metal plate S. Furthermore, the calculated plate width may be stored, as comparing it with the actual plate width allows for verification of whether the calculation process was successful.

[0029] In step S2, the calculation unit 3 extracts a point cloud of the surface of the metal plate S using the boundary values ​​in the width direction of the metal plate S calculated in the boundary calculation process (surface point cloud extraction process). Specifically, as shown in Figures 9(a) and (b), at the width direction end of the metal plate S on the side closer to the measurement unit 2, a point cloud unrelated to the surface of the metal plate S remains on the underside of the metal plate S due to the measurement principle (within the dotted line area shown in Figure 9(b)), so it is necessary to delete this point cloud. Therefore, first, the calculation unit 3 uses the boundary values ​​in the width direction of the metal plate S calculated in step S1 to extract the point cloud of the surface of the metal plate S from the point cloud within a predetermined rectangular parallelepiped area extracted in step S1.

[0030] Next, as shown in Figure 10, the calculation unit 3 divides the point cloud on the surface of the metal plate S into multiple regions along the longitudinal direction of the metal plate. Then, for the point cloud within each region, the calculation unit 3 calculates a quadratic function in the height direction of the metal plate S using the least squares method, with the coordinate values ​​in the width direction of the metal plate S as variables, and deletes point clouds that are more than a predetermined distance from the quadratic function. The point cloud on the metal plate surface after deletion is shown in Figure 11. As shown by the dotted line in Figure 11, it can be seen that a point cloud unrelated to the surface of the metal plate S remains on the underside of the metal plate S. Next, the calculation unit 3 divides the point cloud on the surface of the metal plate S into multiple regions along the longitudinal direction of the metal plate, and calculates the polar coordinate value (r,θ) in the vertical plane (yz plane) with the position of the measurement unit 2 as the origin for the point cloud within each region. Next, the calculation unit 3 sorts the point cloud by the angle θ of the calculated polar coordinate value and assigns a point cloud number to each point cloud in the sorted order. The calculation unit 3 then identifies the point cloud from the point cloud number with the maximum widthwise position to the last point cloud number as the point cloud representing the surface of the metal plate. For example, in the example shown in Figure 12, the calculation unit 3 identifies the point cloud from point cloud P3 (point cloud number 3), which has the maximum widthwise position, to point cloud P6 (point cloud number 6) as the point cloud representing the surface of the metal plate. The point cloud after this process is shown in Figure 13. As shown in Figure 13, it can be seen that irrelevant point clouds under the metal plate have been deleted. With this, the process in step S2 is completed, and the calculation process proceeds to the process in step S3.

[0031] In step S3, the calculation unit 3 uses the point cloud of the metal plate S surface extracted in step S2 to remove measurement errors using the smoothed thin plate spline method and calculate the curved surface of the metal plate S (metal plate curved surface calculation process). Since the calculation using the smoothed thin plate spline method is time-consuming, it is advisable to use the technology described in Patent Document 2 to speed up the calculation. With this, the process of step S3 is completed, and the series of calculation processes is finished.

[0032] As is clear from the above explanation, in the metal plate shape calculation process, which is one embodiment of the present invention, the measurement unit 2 measures a point cloud of the measurement area including the surface of the metal plate. Then, the calculation unit 3 calculates the boundary of the metal plate from the point cloud measured by the measurement unit 2, extracts a point cloud of the metal plate surface from the point cloud using the calculated boundary, and calculates the curved surface of the metal plate from the extracted point cloud of the metal plate surface. This makes it possible to measure the shape of the metal plate at low cost and with high maintainability. [Examples]

[0033] In this embodiment, a measuring unit 2 was installed on the entry side of a cold rolling mill to measure the shape of the steel plate on the entry side. If the measured shape of the steel plate was unsatisfactory, rolling was stopped to prevent the steel plate from breaking. The width of the steel plate was set to 900 mm to 1.3 m. A three-dimensional laser scanner with a measurement cycle of 10 Hz was used in the measuring unit 2, and boundary calculation processing was performed every 10 Hz. The value of α in equation (1) was set to 0.1. Since the curved surface calculation processing takes time, the surface point cloud extraction processing and curved surface calculation processing were performed every 1 Hz. As a result, the curved surface of the steel plate shown in Figure 14 could be calculated.

[0034] The embodiments of the invention made by the present inventors have been described above, but the present invention is not limited by the descriptions and drawings that constitute part of the disclosure of the present invention in this embodiment. For example, the present invention may be used for measuring the shape of a steel sheet in the meandering control method in a looper described in Patent Document 3. The present invention may be used for measuring the shape of a steel sheet in the leveling control method for cold rolling described in Patent Document 4. The present invention may be used for measuring the shape of the steel sheet at the entry side and exit side of the annealing furnace in order to monitor changes in the shape of a steel sheet in the annealing furnace. The present invention may be used for measuring the shape of a steel sheet when determining the cutting length of a defective part of the shape by measuring the shape of the steel sheet. Thus, all other embodiments, examples, and operational techniques made by people skilled in the art based on this embodiment are included in the scope of the present invention. [Industrial applicability]

[0035] According to the present invention, it is possible to provide a metal plate shape measuring device and a metal plate shape measuring method that can measure the shape of a metal plate at low cost and with high maintainability. [Explanation of symbols]

[0036] 1 Metal plate shape measuring device 2 Measuring part 3 Calculation section R Conveyor Roll S Metal plate

Claims

1. A metal plate shape measuring device for measuring the shape of a moving metal plate, A measuring unit that measures a point cloud of a measurement area including the surface of the metal plate, A calculation unit calculates the position of the boundary of the metal plate from the point cloud measured by the measurement unit, extracts a point cloud of the surface of the metal plate from the point cloud based on the calculated boundary position, and calculates the curved surface of the metal plate from the extracted point cloud of the surface of the metal plate. A metal plate shape measuring device equipped with the following features.

2. The metal plate shape measuring device according to claim 1, wherein the calculation unit performs the calculation of the boundary position at the measurement cycle of the measurement unit, and performs the extraction of a point cloud on the surface of the metal plate and the calculation of the curved surface of the metal plate at a cycle longer than the measurement cycle.

3. The metal plate shape measuring device according to claim 1 or 2, wherein the calculation unit converts the coordinate system of the point cloud measured by the measurement unit from the measurement coordinate system of the measurement unit to the coordinate system of the metal plate, extracts a point cloud within a predetermined range including the point cloud on the surface of the metal plate based on the coordinate system of the metal plate, calculates a histogram of the number of extracted point clouds in the width direction of the metal plate, and sets the position in the width direction of the metal plate where the number of point clouds is greater than a predetermined value as the boundary position in the width direction of the metal plate.

4. The metal plate shape measuring device according to claim 3, wherein the calculation unit applies a low-pass filter at the boundary position in the width direction of the metal plate.

5. The calculation unit extracts a point cloud from the surface of the metal plate based on the boundary position in the width direction of the metal plate, divides the extracted point cloud into a plurality of regions along the longitudinal direction of the metal plate, calculates a quadratic function of the height of the metal plate from the point cloud in each region using the least squares method, removes point clouds that are more than a predetermined distance from the calculated quadratic function, divides the remaining point cloud into a plurality of regions along the longitudinal direction of the metal plate, calculates polar coordinate values ​​in a vertical plane with the position of the measurement unit as the origin for the point cloud in each region, sorts the point cloud by the angle of the calculated polar coordinate values, assigns a point cloud number to each point cloud in the sort order, extracts the point clouds from the point cloud number where the position in the width direction of the metal plate is maximum to the last point cloud number, and makes the extracted point cloud the point cloud of the surface of the metal plate, as described in claim 3.

6. The calculation unit extracts a point cloud from the surface of the metal plate based on the boundary position in the width direction of the metal plate, divides the extracted point cloud into a plurality of regions along the longitudinal direction of the metal plate, calculates a quadratic function of the height of the metal plate from the point cloud in each region using the least squares method, removes point clouds that are more than a predetermined distance from the calculated quadratic function, divides the remaining point cloud into a plurality of regions along the longitudinal direction of the metal plate, calculates polar coordinate values ​​in a vertical plane with the position of the measurement unit as the origin for the point cloud in each region, sorts the point cloud by the angle of the calculated polar coordinate values, assigns a point cloud number to each point cloud in the sort order, extracts the point clouds from the point cloud number where the position in the width direction of the metal plate is maximum to the last point cloud number, and makes the extracted point cloud the point cloud of the surface of the metal plate, as described in claim 4.

7. A method for measuring the shape of a moving metal plate, A measurement step of measuring a point cloud of a measurement region including the surface of the metal plate, A calculation step which involves calculating the boundary of the metal plate from the point cloud measured in the measurement step, extracting a point cloud of the surface of the metal plate from the point cloud using the calculated boundary, and calculating the curved surface of the metal plate from the extracted point cloud of the surface of the metal plate, A method for measuring the shape of a metal plate, including the method described above.

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