JP2024010811A - Method and device for measuring movement speed of metal object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive and simple technique for measuring movement speed of a metal body without having to attach rollers and other incidental devices for measurement to line equipment itself.

SOLUTION: A method of measuring movement speed of a metal object being conveyed along a pass line P is provided, the method involving use of a camera 2 for capturing images of a surface 1a of a metal object being conveyed from a fixed position, and comprising deriving a displacement of a pattern 11 on the measurement target surface 1a between two captured images of the measurement target captured by the camera 2, and deriving the movement speed of the measurement target from the displacement and an elapsed time period between two captured images.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a technique for measuring the moving speed of a transported metal object such as a steel plate or a steel pipe. The present invention is a technique suitable for measuring the moving speed (conveying speed) during conveyance of a steel plate in a steel plate production line such as a hot-rolled steel plate rolling line, a cold-rolled steel plate rolling line, a steel pipe production line, etc., for example.

Conventional methods for measuring the speed of steel plates include, for example, the methods described in Patent Documents 1 to 3.
Patent Document 1 describes a method of calculating the speed of a steel plate using rotation pulses of a roll motor in a roll that comes into contact with a steel plate installed on a production line.

Further, Patent Document 2 describes a non-contact steel plate speed measuring method. The measurement method is to irradiate the surface of the steel plate with laser light and utilize the speed change of the reflected light frequency due to the Doppler effect.

Further, Patent Document 3 describes a speed calculation method using a camera as a speed measurement method other than a steel plate. The method is to mark the object to be measured and calculate the moving speed of the object from the relationship between the mark interval on the captured image and the actual mark interval.

Japanese Patent Application Publication No. 51-032658 Japanese Patent Application Publication No. 5-123749 Japanese Patent Application Publication No. 2001-108695

However, in the method of measuring the speed of a steel plate using rotational pulses of a roll motor, it is necessary to install a measuring roll and other incidental equipment on a large scale in the manufacturing equipment to be measured. For this reason, there is a problem in that the measuring device cannot be easily installed on some lines (manufacturing equipment).

Furthermore, in the method of measuring the speed of a steel plate using a laser beam utilizing the Doppler effect, since the measurement is performed without contact, the measuring device can be retrofitted to the line to be measured. However, this measurement method is expensive to introduce. Furthermore, this measurement method requires the installation of accessories such as an air purge device in order to prevent influences from the rolling line environment, and there are restrictions on the installation position. That is, this measurement method has problems with cost and simplicity.

Furthermore, the measurement method as disclosed in Patent Document 3 requires marking the object to be measured as a mark, and also requires the introduction of incidental equipment such as a marking device.

The present invention has been made with attention to the above points, and is an inexpensive and simple technique for measuring the moving speed of a metal object without installing rolls or other incidental devices for measurement on the line equipment itself. The purpose is to provide

In order to solve the problem, one aspect of the present invention is a method for measuring the moving speed of a metal body being conveyed along a path line, the method comprising using a camera that images the surface of the metal body being conveyed at a fixed position. calculate the amount of movement of the pattern on the surface of the metal object between the two images taken by the camera, and calculate the movement of the metal object from the amount of movement and the imaging time interval of the two images. The gist is to calculate the speed.

According to the aspect of the present invention, the moving speed of the metal object is calculated by image processing of two captured images of the surface of the metal object being transported in a non-contact manner. As a result, according to the aspect of the present invention, there is no need to attach rolls or other incidental devices for measurement to the line equipment itself. According to the aspect of the present invention, it is possible to provide an inexpensive and simple technique for measuring the moving speed of a metal body.

FIG. 1 is a schematic diagram for explaining a moving speed measuring device according to an embodiment of the present invention. FIG. 3 is a diagram illustrating the configuration of a speed calculation section according to an embodiment based on the present invention. FIG. 3 is a diagram illustrating areas such as image areas. FIG. 3 is a schematic diagram illustrating a method of calculating a movement amount by image processing. It is a figure explaining the effect of an Example.

Next, embodiments based on the present invention will be described with reference to the drawings.
This embodiment will be described using a steel plate as an example of the metal body. Further, in this embodiment, a case will be described using as an example a case where the conveyance speed (moving speed) of a steel plate to be rolled is measured in a steel plate rolling line. The conveying speed may be measured before rolling, during rolling, or after rolling.
Note that steel plates and other metal plates have texture patterns unique to metals over their entire surface. Furthermore, even when surface treatment is applied, a texture pattern is formed due to the surface treatment.

Further, in the following description, a cold-rolled steel plate rolling line will be assumed, but the applied line may be a hot-rolled steel plate rolling line, a surface treatment line, or the like. Further, the target metal body is not limited to a flat steel plate, but may be a metal body such as a steel pipe or a shaped steel. The present invention is applicable to any object that is a metal object that is transported along a preset path line and has a predetermined surface.

(composition)
In this embodiment, it is assumed that the steel plate 1 is conveyed along a pass line P, as shown in FIG. In FIG. 1, the steel plate 1 (metal band) moves from right to left.
The moving speed measuring device of this embodiment includes a camera 2, a strobe light source 3, a strobe device 5, a synchronization control section 6, and a speed calculation section 8, as shown in FIG.

<Camera 2>
The camera 2 images the surface 1a (the top surface in FIG. 1) of the steel plate 1 being transported. In this embodiment, the camera 2 captures an image every time a synchronization signal is input from the synchronization control unit 6. That is, the camera 2 images the surface 1a of the steel plate 1 at a preset sampling period. In FIG. 1, the reference numeral 9 indicates a fixed arm that supports the camera 2, and the reference numeral 10 indicates a pan head.

In this embodiment, the imaging axis of the camera 2 is oriented in a direction perpendicular to the surface 1a of the steel plate 1 being conveyed (vertical direction in this embodiment). In order to increase the imaging range, the imaging axis of the camera 2 may be inclined toward the transport direction with respect to the above-mentioned vertical direction. When the imaging axis is tilted, the captured image may be standardized (an image viewed from directly above) by projective transformation of the image.

<Strobe light source 3>
The strobe light source 3 is installed so that it can emit light toward the surface 1a of the steel plate 1 in the imaging area. In FIG. 1, reference numeral 4 indicates a tripod that supports the strobe light source 3. The strobe light source 3 is capable of emitting light in synchronization with the imaging by the camera 2 in response to a signal from the strobe device 5.

<Synchronization control unit 6>
The synchronization control unit 6 synchronizes and sends signals to the camera 2 and the strobe device 5 at predetermined sampling.

For example, as shown in FIG. 1, the synchronization control section 6 includes a function generator 6A and a signal conversion circuit 6B.

Function generator 6A generates a trigger signal. The signal conversion circuit 6B converts the trigger signal (analog signal) into a digital signal and outputs the converted digital signal to the strobe device 5 and camera 2. Function generator 6A is connected to personal computer 7 by wire.

Then, a trigger signal is generated at intervals of ΔT seconds, and strobe light emission and imaging by the camera 2 are simultaneously performed by the trigger signal generated from the function generator 6A. As a result, imaging is performed at intervals of ΔT seconds, and the captured images are transferred to the personal computer 7.

<Speed calculation section 8>
The speed calculation section 8 is configured as a program executed by the personal computer 7. The personal computer 7 has an image processing function.
As shown in FIG. 2, the speed calculation section 8 includes an image acquisition section 8A, an image processing section 8B, and a speed calculation section 8C.

[Image acquisition unit 8A]
The image acquisition unit 8A acquires images captured by the camera 2 at a predetermined sampling period.

Here, the imaging area captured by the camera 2 includes, for example, the entire area in the width direction of the steel plate 1, and as shown in FIG. Set to . Alternatively, the sampling period may be set depending on the length of the imaging area in the transport direction.

For example, the length of the imaging region in the conveyance direction is relatively set to be equal to or greater than the value obtained by multiplying the assumed upper limit value of the conveyance speed of the steel plate 1 by the sampling time. For example, it is set to a value obtained by multiplying the assumed upper limit value of the conveyance speed of the steel plate 1 by twice the sampling time.
By setting in this way, the upstream half of the steel plate 1 in one captured image can be reliably present in the next captured image.

Furthermore, edge enhancement processing and the like are performed on the acquired captured image, and cutting processing (image processing) of the area of the steel plate 1 (steel plate area ARA2) is executed. This processing may be performed by the image processing section 8B. The steel plate area ARA2 is set so that the center of the steel plate area ARA2 and the center of the image area ARA1 coincide with each other, and is a rectangular area whose long sides are parallel to the pass line P, as shown in FIG. Thereafter, processing is performed based on this steel plate area ARA2. This steel plate area ARA2 may include the outside of the steel plate 1 in the width direction, or the steel plate area ARA2 may be set inside the widthwise ends of the steel plate 1. That is, the widthwise dimension of the steel plate area ARA2 may be wider or narrower than the width of the steel plate 1.

In addition, the captured image is subjected to brightness unevenness removal through shading correction and brightness enhancement processing, so that the steel plate texture pattern can be easily identified. In addition, strobe photography was also carried out to make it easier to identify the texture pattern of the steel plate.

[Image processing unit 8B]
The image processing section 8B performs image processing on two captured images obtained by the image acquisition section 8A and taken at different imaging times. Specifically, the image processing unit 8B calculates the amount of movement of the pattern on the measurement target surface 1a between the two captured images using a digital image correlation method. The two captured images are the first captured image (first captured image) and the next captured image ΔT seconds later (second captured image) acquired by the image acquisition unit 8A.

The image processing unit 8B repeatedly executes this process. For example, the following image processing is repeated using the second captured image as the first captured image. Alternatively, for example, a set is formed for every two captured images that are consecutively acquired, and the above image processing is executed for each set.

An example of a method for calculating the amount of movement in the image processing unit 8B will be described.
In this embodiment, it is assumed that a texture pattern unique to the steel plate 1 is detected and the amount of movement is calculated.

A template area ARA3 is set in advance at a predetermined position (a preset position) in the steel plate area ARA2 (see FIG. 3). It is preferable that the template area ARA3 is set at the center in the width direction of the steel plate area ARA2. Further, the size of the template area ARA3 is set so that a pattern that can be distinguished from other texture patterns can be obtained.
Note that the template area ARA3 may be directly set in the image area ARA1 without setting the steel plate area ARA2.

Then, the image processing unit 8B acquires the texture pattern 11 (pattern of the steel plate 1) located in the template area ARA3 from the image area ARA1 of the first captured image, as shown in FIG. 4(a).

Next, the image processing unit 8B uses the digital image correlation method to recognize, in the steel plate area ARA2 of the second captured image, the area where the area of the acquired pattern of the steel plate 1 is located as the correlation area ARA3-1 (FIG. (see (b)). Then, the amount of movement along the path line P from the template area ARA3 to the correlation area ARA3-1 in the steel plate area ARA2 is calculated as the amount of moving pixels, and the amount of movement of the steel plate 1 is determined based on the amount of movement per pixel.
Note that the extraction of the correlation area ARA3-1 does not need to be performed over the entire image area ARA1, and may be performed at least only within the steel plate area ARA2. In addition, if the amount of swinging (meandering amount) in the width direction of the steel plate when moving along the pass line P is within a predetermined range, the width is wider than the template area ARA3 by the safety margin of the predetermined range. The area may be set to the width of the steel plate area ARA2. In this case, the width of the steel plate area ARA2 is set narrower than the width of the steel plate 1.

[Speed calculation unit 8C]
The speed calculation unit 8C calculates the moving speed of the measurement target from the movement amount calculated by the image processing unit 8B and the imaging time interval ΔT of the two captured images. Specifically, the speed calculating unit 8C calculates the moving speed (=moving amount/ΔT) by dividing the moving amount by ΔT.

(Other operations)
According to the present embodiment, in order to measure the moving speed (transport speed) of the steel plate 1, there is no need to install ancillary equipment on the transport equipment (line) itself. In this embodiment, a captured image captured by the camera 2 in a non-contact manner is used as information for measuring the conveyance speed.

In this embodiment, in order to easily identify the steel plate texture pattern 11 in the captured image, strobe photography is used, but the strobe light source 3 may not be used. Furthermore, the camera 2 may include the strobe light source 3. However, when light is emitted by a strobe, the texture pattern 11 on the surface 1a of the steel plate 1 becomes clearer, and the measurement accuracy is further improved.

In this way, in this embodiment, the optical equipment configuration including the camera 2 and the strobe light source 3, which can be installed on the production line, is simply installed near the line in a non-contact manner. As a result, the device of this embodiment can be easily installed and can easily measure the speed of one steel plate.

In the present embodiment, the amount of movement of the texture pattern 11 on the surface 1a of the steel plate 1 in the two sets of captured images acquired at different times is calculated by image processing, so there is no need to perform marking processing in advance. Further, at this time, by setting the template area ARA3 in advance for the area in the captured image, it becomes easy to select the texture pattern 11 and to recognize the position of the texture pattern 11 after movement.

In this way, in this embodiment, the speed of the object is determined by capturing the pattern 11 unique to the measurement object included in the captured image and calculating the amount of movement of the pattern 11 seen on the measurement object between the captured images. Calculate.

As described above, according to the present embodiment, the moving speed of the metal body is calculated by image processing of two captured images of the surface 1a of the metal body being transported. As a result, according to this embodiment, there is no need to attach rolls for measurement or other incidental devices to the line equipment itself. According to this embodiment, it is possible to provide an inexpensive and simple technique for measuring the moving speed of a metal body.

(others)
The present disclosure can also take the following configuration.
(1) A method for measuring the moving speed of a metal object conveyed along a pass line, the method comprising:
It has a camera that images the surface of the metal object being transported at a fixed position,
The amount of movement of the pattern on the surface of the metal object between the two images taken by the camera is calculated, and the speed of movement of the metal object is calculated from the amount of movement and the imaging time interval of the two images. do.
(2) The calculation of the amount of movement based on the two captured images is performed by a digital image correlation method.
(3) The above pattern is a pattern unique to the metal body that is present on the surface of the metal body.
(4) Of the above two captured images, the image existing in the template area ARA3 preset in the image area of the captured image with the earlier time is set as the above pattern, and image processing is performed to create an image that is the same as the pattern pattern of the pattern. The amount of movement is calculated by extracting the area from the image area of the captured image taken at a later time.
(5) Captured images are acquired at a predetermined sampling period, and the calculation of the moving speed is continuously performed.
(6) A moving speed measuring device for a metal body being conveyed along a path line, comprising a camera that images the surface of the metal body being conveyed;
an image acquisition unit that acquires an image taken by the camera;
an image processing unit that performs image processing using a digital image correlation method on two captured images acquired by the image acquisition unit at different imaging times, and calculates the amount of movement of the pattern on the surface of the metal body between the two captured images; ,
A speed calculating section that calculates the moving speed of the measurement target from the moving amount calculated by the image processing section and the imaging time interval of the two captured images.
(7) a strobe light source that emits light at the imaging position of the camera;
A synchronization control unit that activates the strobe light source in synchronization with imaging by the camera.
(8) The above-mentioned pattern is a pattern unique to the metal body, which is formed on the surface of the metal body.

Next, an example based on this embodiment will be described.
This example was applied to a cold-rolled steel plate rolling line as shown in FIG. 1, and fast reading measurements were performed using the apparatus configuration as shown in FIG.

Specifically, on a cold-rolled steel plate rolling line, a fixed arm 9 is provided to position the camera 2 at a height of 1250 mm from the steel plate 1 on the line, and a free pan head 10 is used to set the camera 2 at a fixed position on the fixed arm 9. Fixed. Further, a strobe light source 3 was installed on a tripod 4 on the side of the line. The strobe light source 3 was installed at a position 400 mm behind the camera 2 on the line and at a height of 1250 mm from the steel plate 1. Further, the camera was installed so that the angle between the imaging axis of the camera 2 and the light emitting axis of the strobe light source 3 was 60°. With this, both the camera 2 and the strobe light source 3 can be easily installed.

In this way, installation around the line only requires installing the camera 2 and strobe light source 3 and wiring each device. As a result, the equipment can be installed with approximately 6 hours of shutdown.
After installation, the camera 2 was adjusted by adjusting the amount of light by adjusting the aperture. Additionally, as part of the strobe light emission adjustment, we made fine adjustments to the irradiation direction. Since these adjustments are also minimal, it is a simple measurement method.

As another measurement method (comparative example), we adopted a Doppler plate speed meter, which is relatively easy to modify during installation. Comparing this comparative example and the present example, the present example could be introduced at 1/3 of the cost of the comparative example.

Further, the strobe light emission and camera 2 imaging cycle was set to 100 Hz (100 times per second), and the calculation cycle in the image processing unit 8B was set to 50 Hz to perform correlation calculation between the previous and previous images using software. In this case, the measurements provided velocity data at 0.02 second intervals.

At this time, the strobe light emission and the imaging period of the camera 2 were determined based on the captured image and the maximum speed of the measurement object (steel plate 1). It is sufficient if the cycle is such that the steel plate texture pattern 11 located in the template area ARA3 in the captured image falls within the captured image after ΔT seconds.

FIG. 5 is a graph comparing the speed of an existing speedometer (comparative example) in order to verify the speed accuracy measured when implementing the present invention. The speed of the existing speedometer was measured using the rotation pulse of the roll motor.

The graph in FIG. 5 plots the existing shape meter roll speed in the speed range where the conveyance speed of the steel plate 1 is in a steady state. In addition, median filter processing using the previous 50 data was performed on the velocity data at 0.02 second intervals in the velocity range where the velocity obtained by measurement was in a steady state. That is, the processed data was sampled at 0.2 second intervals, a moving average of three points before and after was calculated, and the values obtained by sampling the calculated data at 1 second intervals were plotted.

The difference between the two average values was 0.04%. From this, it can be seen that the measurement in this example achieved good results with accuracy comparable to speed measurement results using rotation pulses of a conventional roll motor.

1 Steel plate (metal body)
1a Surface 2 Camera 3 Strobe light source 5 Strobe device 6 Synchronization control unit 7 Personal computer 8 Speed calculation unit 8A Image acquisition unit 8B Image processing unit 8C Speed calculation unit 11 Texture pattern ARA1 Image area ARA2 Steel plate area ARA3 Template area P Pass line

Claims (8)

A method for measuring the moving speed of a metal object conveyed along a path line, the method comprising:
It has a camera that images the surface of the metal object being transported at a fixed position,
The amount of movement of the pattern on the surface of the metal object between the two images taken by the camera is calculated, and the speed of movement of the metal object is calculated from the amount of movement and the imaging time interval of the two images. do,
A method for measuring the moving speed of a metal object, characterized in that: The calculation of the amount of movement based on the two captured images is performed by a digital image correlation method.
The method for measuring the moving speed of a metal body according to claim 1. The pattern is a pattern unique to the metal body on the surface of the metal body,
The method for measuring the moving speed of a metal body according to claim 1. Of the above two captured images, an image existing in a template area preset in the image area of the captured image with the earlier time is used as the above pattern, and by image processing, an area of the image that is the same as the pattern pattern of the pattern is created. Calculating the amount of movement by extracting from the image area of the captured image at a later time;
4. The method for measuring the moving speed of a metal body according to claim 3. acquiring captured images at a predetermined sampling period and continuously calculating the moving speed;
The method for measuring the moving speed of a metal body according to any one of claims 1 to 4. A device for measuring the moving speed of a metal object being conveyed along a path line, comprising: a camera that images the surface of the metal object being conveyed;
an image acquisition unit that acquires an image taken by the camera;
an image processing unit that performs image processing using a digital image correlation method on two captured images acquired by the image acquisition unit at different imaging times, and calculates the amount of movement of the pattern on the surface of the metal body between the two captured images; ,
a speed calculation unit that calculates the moving speed of the measurement target from the movement amount calculated by the image processing unit and the imaging time interval of the two captured images;
An apparatus for measuring the moving speed of a metal body, comprising: a strobe light source that emits light at the imaging position of the camera;
a synchronization control unit that activates the strobe light source in synchronization with imaging by the camera;
7. The moving speed measuring device for a metal body according to claim 6, further comprising: The pattern is a pattern unique to the metal body on the surface of the metal body,
The apparatus for measuring the moving speed of a metal body according to claim 6 or claim 7.

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