JPH08114425A - Method for optically detecting shape of rolled plate - Google Patents

Abstract

PURPOSE: To provide an optical method to detect the shape of rolled plate by which detection differences due to positional change of a mounted camera for picking up a picture of a bar-type light source projected on a plate material can be eliminated without using a special-purpose sensor and the shape of the rolled plate can be detected as a result. CONSTITUTION: In a rolling work of a plate material 1, a picture of a bar-type light source 2 installed along the widthwise direction of the material 1 is projected on the material 1, and a change in position of the picture thereof accompanied with a tilt of the material 1 in a lengthwise direction is sensored so as to detect the shape of the material 1. In such an operation, a picture S of bar- type light source at the time when the shape of the material 1 is flat is averaged. The averaged picture S thereof is set as a light source picture for a reference position by which a change in position of the bar-type light source is sensored.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detection method for optically detecting the shape of a rolled sheet material.

[0002]

2. Description of the Related Art In the rolling process of a metal plate material, for example, the rolling process of an aluminum plate material, as a result of various technical developments in the past, the plate thickness control of a rolling mill has reached a substantially satisfactory level. However, the remaining problems include the shape of the rolled plate and roll crown control.
As a cause of this, particularly during hot rolling, detection of the shape (flatness) of the plate material can be mentioned.

Among these, an optical shape detection method is mentioned as a detection method particularly suitable for hot rolling of aluminum sheet material. See "Plasticity and Machining" Vol.
12, No. 124, May 1971, pp. 353-35.
See page 8 of JP-A-63-198808.

In the optical shape detection method, when the shape of the plate material is defective, it is read that the position of the virtual image of the rod-shaped light source reflected on the plate material changes in proportion to the inclination of the plate material in the longitudinal direction due to the shape defect. This is a method of detecting a change in the shape of the plate material.

That is, in this optical shape detecting method, a light beam is emitted from a rod-shaped light source provided along the width direction of the plate member to the plate member, and a virtual image of the rod-shaped light source reflected on the plate member is photographed by a camera,
A bright line is obtained by binarizing the image into a dark part and a bright part by extracting a virtual image based on a certain brightness level, and the bright line is moved in the longitudinal direction of the plate at a plurality of points in the width direction of the plate. It has a step of obtaining a quantity. Then, calculation is performed based on the data obtained at this stage to obtain the shape of the plate material.

The reason why this optical shape detection method is particularly suitable for hot rolling of aluminum sheet material is as follows. One of them is that it is a non-contact type and does not scratch the surface of an aluminum plate that is very susceptible to scratches. In addition, the aluminum plate material has a high light reflectance by hot rolling, and can be easily subjected to optical treatment. In addition,
In the case of the contact roll type shape detection method, the contact roll and the plate material may not be in good contact with each other due to the high rigidity of the aluminum plate.

[0007]

However, the method conventionally adopted as the optical shape detecting method has the following problems. That is, it is easily affected by the variation in the mounting position of the camera that captures the image of the rod-shaped light source reflected on the plate material. When determining the shape of the plate material, the shape of the plate material at each position on the plate material is obtained from the difference between the position of the virtual image (reference bright line) of the reference rod-shaped light source and the position of the bright line that is currently obtained.
However, when the mounting position of the camera that captures the image of the rod-shaped light source reflected on the plate member changes from a predetermined position, the deviation of the camera position causes an error in the shape of the plate member to be detected.

That is, a virtual image of a bar-shaped light source on a plate material photographed by a camera is binarized with a certain luminance level or more as a criterion, and a longitudinal moving amount of the obtained bright line is obtained at a necessary point in the width direction. When the amount of movement of the plate material in the longitudinal direction is zero when viewed from the reference position, the shape of the plate material is good. For example, when the amount of movement in the longitudinal direction from the reference position is large at the center of the plate material in the width direction, it is determined that the plate material has medium elongation. This reference position indicates a case where the plate material has a flat shape, and is normally determined when the camera is attached.

However, in rolling a plate material, a large impact occurs when the rolling roll bites the plate material, and there is always a possibility that the mounting position of the camera slightly changes due to the impact. In addition, the surroundings of the rolling mill are usually in a high temperature and high humidity atmosphere, and it is possible to avoid distortion of the optical system over time due to thermal stress and corrosion occurring in the optical system parts including the lens under the influence of this atmosphere. Absent. In these cases, if the reference line is not constantly corrected, a large error will occur in the detected shape of the plate material. Therefore, it is necessary to calibrate the reference line of the camera at a certain time interval, and man-hours for that purpose and measurement errors other than calibration are weak points of the optical rolling plate shape inspection method.

If a specially provided sensor can detect a change in the camera position, it is possible to correct the result based on the result. However, the environment around the rolling mill is bad due to fumes and the like, and as a result, the reliability of the sensor is low, and the cost of the detection device increases due to the provision of the sensor.

The present invention has been made in view of the above circumstances, and it is possible to eliminate a plate material shape detection error due to a variation in the mounting position of a camera for capturing an image of a rod-shaped light source reflected on a plate material without using a special sensor. Therefore, it is an object of the present invention to provide an optical rolling plate shape detection method capable of satisfactorily detecting the shape of a rolled plate material.

[0012]

In order to achieve the above object, the optical rolled plate shape detecting method of the present invention is an image of a rod-shaped light source provided along the plate material width direction of the plate material in the process of rolling the plate material. When the shape of the plate material is flat when the shape of the plate material is flat when the shape of the plate material is detected by reading the change in the position of the image of the rod-shaped light source reflected on the plate material due to the inclination of the plate material in the longitudinal direction. An image of the rod-shaped light source is averaged, and the averaged image of the rod-shaped light source is used as a light source image that serves as a reference position for reading a change in the position of the image of the rod-shaped light source. And

[0013]

The inventors of the present invention have studied the method of automatically correcting the reference line and have proposed the present invention. The present invention focuses on the fact that the reference bright line can be a bright line when the shape of the plate is good, and the bright line obtained by averaging the bright lines obtained when the shape of the plate is good is an image of a rod-shaped light source. It is possible to easily obtain the reference bright line without using a sensor by using it as a reference bright line that serves as a reference position for reading the change in the position.

[0014]

EXAMPLE An example of the optical rolling plate shape detecting method of the present invention will be described. First, as shown in FIG. 1, in a process of rolling a plate material made of metal such as aluminum with a pair of rolling rolls 51, the plate material 1 rolled and moved is photographed by a camera. That is, the rod-shaped light source 2 such as a fluorescent lamp is provided along the plate material width direction with respect to the plate material 1 on the side of the passage through which the plate material 1 moves, and the television camera 3 is provided near the path of the plate material 1. Then, the rod-shaped light source 2 is turned on to irradiate the surface of the plate 1 with light rays. The television camera 3 captures a virtual image S of the rod-shaped light source 2 reflected on the surface of the plate material 1. Here, when the plate material 1 is flat over the entire surface as shown in FIG. Is a straight line. However, when part of the plate material 1 is distorted, the virtual image S on the plate material 1 is also distorted according to the distortion.

For example, as shown in FIG. 2B, in the case where the plate material 1 is distorted in the central portion in the width direction of the plate material 1,
The virtual image S on the plate material 1 is also deformed due to distortion occurring in the central portion in the plate width direction. FIG. 3 shows an image showing the plate material 1 displayed on the monitor screen and the virtual image (bright line) S imaged on the plate material 1. In FIG. 3, L is the left and right edges of the plate material 1, the Y direction is the rolling direction, that is, the plate material longitudinal direction,
The X direction is the width direction of the plate material.

The television camera 3 calculates the image signal of the virtual image S of the rod-shaped light source 2 reflected on the plate 1 by the arithmetic signal adjusting circuit 11
Send to Next, in the binarization circuit 12, the image signal of the virtual image S of the rod-shaped light source 2 is binarized into a dark portion and a bright portion on the basis of a certain brightness level to extract a virtual image, and then a bright line is extracted from the extracted image signal. Obtain the bright line by the extraction circuit 13,
The reference bright line calculation circuit 14 calculates the reference bright line Sa.

Here, when a defect occurs in the shape of the plate material 1, the virtual image of the rod-shaped light source 2 reflected on the plate material 1, that is, the position of the bright line is proportional to the inclination of the plate material 1 in the longitudinal direction due to the shape defect. Move in the longitudinal direction. Therefore, in the plate material shape calculation circuit 15, the shift amount of the bright line in the longitudinal direction of the plate material 1 is obtained at a plurality of points in the width direction of the plate material 1 to detect the change in the shape of the plate material 1. Finally, the output circuit 16 is used for the plate material 1
A signal representing the shape of the is output to a display device or a recording device.

Next, a specific processing method will be described.
FIG. 4 shows a virtual image, that is, a bright line S, which is reflected on the plate 1 when the plate 1 is irradiated with the light beam of the rod-shaped light source 2. FIG.
Then, as shown in FIG. 2B, the virtual image of the rod-shaped light source 3 reflected on the plate material 1, that is, the position of the bright line S when the plate material 1 is deformed at the central portion and is in the state of middle extension (center buckle) is shown. ing. In the state of medium elongation, the central portion in the width direction of the plate material 1 is excessively rolled and stretched in comparison with other portions,
As a result, a corrugated portion is generated at the center of the plate material 1 in the width direction. In this case, the reference bright line S along the width direction of the plate material 1
With respect to a, the bright line S at each time is shifted in the longitudinal direction of the plate material 1 in proportion to the size of the intermediate extension (wavy portion).

This will be described with reference to FIG.
That is, when the shape of the plate material 1 is flat and normal (the broken line in the drawing), the plate material 1 is irradiated by the light beam of the rod-shaped light source 3.
A virtual image (reference bright line Sa) is formed at position a on the camera 3
Takes a virtual image (reference bright line Sa) at the position a. When the plate material 1 is abnormal due to waviness (solid line in the figure), the reflection angle of the virtual image of the rod-shaped light source 3 changes, so that the bright line S is in the longitudinal direction of the plate material 1 with respect to the reference bright line Sa. It is displaced to the displaced b position. The camera 3 captures the virtual image (bright line S) at the position b.

Then, in order to detect the shape of the plate material 1 in such an example, the following processing is performed. The amount of change in the virtual image of the rod-shaped light source 3 caused by the defective shape of the plate material 1 can be geometrically determined.

It is assumed that the plate member 1 has a defective shape and is inclined at a certain angle with respect to the rod-shaped light source 3. Then, the virtual image of the rod-shaped light source 3 reflected on the surface of the plate 1, that is, the bright line S, is proportional to the magnitude of the gradient of the plate 1 with respect to the virtual image of the rod-shaped light source 3 reflected on the surface of the flat plate 1, that is, the reference bright line Sa. And then displace. As a result, the bar-shaped light source 3 reflected on the plate material 1 during rolling
The virtual image, that is, the bright line S, is displaced in a curved shape in proportion to the change in the shape of the plate material 1.

For example, if the shape of the plate 1 is given by a sine curve represented by the equation (1) as shown in FIG. 6 and is displaced in a curved shape, the displacement state of the virtual image of the rod-shaped light source 3 caused by this is As shown in FIG. 7, the amount is proportional to the equation (2) obtained by differentiating the equation (1).

[0023]

[Equation 1]

However, h: state of change of plate shape h ': state of plate shape optically detected H: amplitude of wave of plate P: period of wave of plate x: length of plate Due to the relationship between the relative positions of the light source 3, the plate member 1 and the camera 2, the amount of displacement that is optically amplified differs in the width direction of the plate member 1. For the virtual image of the rod-shaped light source 3 at a plurality of points in the width direction of the plate material 1, that is, the displacement amount qhz of the bright line S, the proportional constant determined geometrically and optically is set to 4 Kz, and the plate material 1
When the length x of is set to vt and is expressed on the time axis, it is expressed by Expression (3). FIG. 8 schematically shows such a virtual image of the rod-shaped light source 3, that is, a process of processing the bright line S (normal),
FIG. 8A is a perspective view showing a bright line in the plate material 1, FIG. 8B is a diagram showing a displacement of the bright line shown in the section taken along line A-A in FIG. 8A, and FIG. 8C is a treatment of the bright line. It is a figure which shows the result of.

[0025]

[Equation 2]

However, v: speed of plate material t: time T: time required for one cycle Kz: amplification factor different depending on each point in the width direction of the plate material Next, amplitude of displacement qhz of bright line from equation (3) = {4
If Kz · π · (H / P)} / 2 is known, Kz and π are known, and the desired steepness = H / P can be obtained. Therefore, when the absolute value of the equation (3) is averaged over an appropriate time, the result is a value proportional to the amplitude of the wave of the plate material. When this content is made into an expression, it is expressed by the following expressions (4) and (5).

[0027]

(Equation 3)

However, Qhz: the shape of the plate material passed in a unit time. As a result, in the optical rolling plate shape detection method, the plate material 1
In addition to binarizing the virtual image S of the bar-shaped light source 2 shown in FIG. 2 to obtain the bright line, and improving the processing speed and the detection accuracy in the stage of obtaining the displacement amount of the bright line S in the plate longitudinal direction at each point in the plate width direction. Can be planned.

By the way, in detecting the shape of the sheet material 1 rolled in this way, a large impact may occur when the rolling roll bites the sheet material, and the mounting position of the camera may change slightly due to the impact. Always exists. In addition, the surroundings of the rolling mill are usually in a high temperature and high humidity atmosphere, and it is possible to avoid distortion of the optical system over time due to thermal stress and corrosion occurring in the optical system parts including the lens under the influence of this atmosphere. Absent. In these cases, if the reference line is not constantly corrected, a large error will occur in the detected shape of the plate material.

As described above, as a phenomenon during rolling, a change in the mounting position of the camera 3 and distortion of the optical system often cause the behavior of the bright line during rolling as shown in FIG. That is, when the mounting position of the camera 3 is deviated from the preset position in the longitudinal direction of the plate material 1, the bright line S is shown in FIG.
9 with respect to the initially set reference bright line Sa shown by the solid line in FIG.
As shown by the broken line, the plate material 1 is displaced in the longitudinal direction.

Therefore, when the bright line S is processed by the above-described method to obtain the shape of the plate material 1, an error occurs as shown in FIG. 10, and the error increases with the amount of displacement of the mounting position of the camera 3. The shape Qhz of the plate material that has passed in a unit time when the amount of deviation is the minimum is the minimum value. FIG. 10 schematically shows a virtual image of such a rod-shaped light source 3, that is, a process of processing a bright line S (at the time of abnormality), and FIG. 10A is a perspective view showing a bright line in the plate 1, and FIG. Is the same (a) A
FIG. 7C is a diagram showing the displacement of the bright line represented in the cross section along the line A, and FIG. 8C is a diagram showing the result of the bright line processing.

Therefore, the following method is adopted as a countermeasure against the occurrence of an error in detecting the shape of the plate material 1 due to such a displacement of the mounting position of the camera 3.
That is, noting that the reference bright line can be approximated by the bright line when the shape of the plate material 1 is good (flat), the bright lines obtained when the shape of the plate material 1 is good (flat) are averaged,
The bright line obtained by this averaging process is used as a reference line. The method described below is adopted as the specific logic of this processing.

When the shape of the plate material 1 is not abnormal, the bright lines are averaged by the method described later, and the result is given as the reference bright line. Further, the determination as to whether the shape of the plate material 1 is abnormal or not is made based on the detection output of the above-mentioned sensor, or if necessary, using the detection output of a separately provided sensor, and further operation is performed. The recognition result obtained by a person's visual observation may be adopted.

There are various methods for averaging the bright lines, but the method described below is adopted in this embodiment. First
The processing method of is the exponential smoothing method. In this method, the position of the bright line is exponentially smoothed and the result is used as the reference bright line. At this time, noise is removed by reducing the exponential smoothing coefficient to some extent. In this processing method, the following equation (6) is used.

[0035]

[Equation 4]

However, Yi: current bright line Y ^* i-1: reference bright line (previous value) Y ^* i: standard bright line (previous value) β: exponential smoothing coefficient (<1) Yi, Y ^* i-1 And Y ^* i are shown in FIG. The second processing method is the moving average method. In this method, the positions of the bright lines are moving averaged and the result is used as the reference bright line. At this time, noise is removed by increasing the moving average number to some extent. In this processing method, the following equation (7) is used.

[0037]

(Equation 5)

However, m: number of moving averages The third processing method is a statistical processing method. in this way,
Focusing on the fact that the shape Qhz of the plate material that has passed through the unit time expressed by the above equation (4) is minimized without any error in the reference position, Qhz when the position of the reference bright line is changed is obtained, and Qhz Is a method of obtaining the position of the reference bright line that minimizes. This method is shown in FIG.

As described above, according to the present invention, the reference bright line Sa of the plate material 1 is accurately obtained, and the position of the obtained reference bright line Sa is compared with the actual position of the bright line S which varies depending on the shape of the plate material 1. As a result, the shape of the plate material 1 can be accurately obtained without using a special sensor. The subsequent processing is the same as in the conventional case.

This optical rolled plate shape detecting method can obtain an excellent effect when applied to a method for detecting a change in the plate material shape particularly when an aluminum plate material is hot rolled.

The present invention is not limited to the above-described embodiments, but can be implemented with various modifications. For example, the functional expression is determined based on various factors such as the rolling mill, rolling conditions, and deformation of the plate material.

[0042]

As described above, according to the optical rolled plate shape detecting method of the present invention, the camera for photographing the image of the bar-shaped light source reflected on the plate material at the stage of processing the virtual image of the bar-shaped light source reflected on the plate material. It is possible to eliminate the error in the plate detection due to the variation of the mounting position of the plate without using a special sensor.Therefore, the shape of the rolled plate can be detected quickly and with high accuracy. It greatly contributes to the improvement of quality and rolling efficiency.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an embodiment of a method of the present invention.

FIG. 2 is an explanatory diagram showing a process of photographing a bright line reflected on a plate material with a camera.

FIG. 3 is a diagram showing a virtual image of a rod-shaped light source taken by a camera.

FIG. 4 is a diagram showing an example of bright lines reflected on a plate material.

FIG. 5 is a diagram showing a relationship between a shape of a plate material and a bright line.

FIG. 6 is a diagram schematically showing the shape of a plate material.

FIG. 7 is a diagram schematically showing the inclination of the shape of a plate material.

FIG. 8 is a diagram schematically showing a process of processing bright lines when the plate material has a normal shape.

FIG. 9 is a diagram showing an example of a bright line when the camera position is displaced.

FIG. 10 is a diagram schematically showing a process of processing a bright line when a plate material has an abnormal shape.

FIG. 11 is a diagram showing an example of a method of processing bright lines.

FIG. 12 is a diagram showing another example of a method of processing a bright line.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Plate material, 2 ... Rod-shaped light source, 3 ... Camera, 11 ... Operation signal adjustment circuit, 12 ... Operation signal binarization circuit, 13 ... Bright line extraction circuit, 14 ... Reference bright line calculation circuit, 15 ... Plate shape operation circuit, S … Bright line.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B21B 38/02 B21C 51/00 L

Claims (1)

[Claims] 1. In the process of rolling a plate material, an image of a bar-shaped light source provided along the plate material width direction of the plate material is projected on the plate material, and the bar-shaped light source reflected on the plate material is associated with the inclination of the plate material in the longitudinal direction. When detecting the shape of the plate material by reading the change in the position of the image, the image of the rod-shaped light source when the shape of the plate material is flat is subjected to averaging, and the image of the rod-shaped light source subjected to the averaging is A method for detecting the shape of an optical rolling plate, wherein the light source image is used as a reference position for reading a change in the position of the image of the rod-shaped light source.