JP6079072B2 - Hot length measuring method and apparatus - Google Patents

Description

  The present invention relates to a method and an apparatus for measuring a length of a hot long material, and more specifically, a hot length that measures the length of a long material in a hot state (for example, a steel pipe, a steel bar, or a cast piece) in a non-contact manner. The present invention relates to a length measuring method and apparatus for a scale.

The following are known as conventional length measurement techniques for measuring the length of a long material in a non-contact manner.
(Prior Art 1) Both ends of a stationary long material to be measured are imaged by a plurality of cameras (a digital camera using an image sensor as an image sensor; the same applies hereinafter), and image processing of the captured images The length of the long material is calculated from the data obtained from the above and the distance data between the individual installation positions of the camera (for example, see Patent Document 1).
(Prior Art 2) The front end of the long material being transported is individually provided with a plurality of end detection sensors (referred to as end sensors; a light emitting / receiving photoelectric sensor is shown as a specific example). And the rear end is imaged by one camera, the image processing data of the captured image, and the end sensor of the camera through the first end detector. The length of the long material is calculated from the distance data between the individual installation positions (see, for example, Patent Document 2).
(Prior Art 3) In the prior art 2, as a means for correcting a length measurement error caused by the shape of the rear end portion being not a rectangular end shape but a spear shape, the upstream side close to the camera installation position is A second end detector comprising a plurality of end sensors for detecting both ends in the transport width direction at different transport height direction positions of the rear end of the long material (see, for example, Patent Document 3).

Japanese Patent Laid-Open No. 04-184205 JP-A-57-022507 Japanese Patent Laid-Open No. 10-082617

  According to the above-described prior art, in order to ensure the measurement accuracy, a plurality of the cameras are individually installed or used, or only one camera is installed and one end side of the long material or the other There are only two alternatives, or a combination of the two, to individually install a plurality of the end sensors on the end side, but in any case, the number of cameras and the end sensors to be installed However, it is difficult to increase the equipment cost.

  In other words, in the prior art, a large number of cameras and sensors must be installed in order to ensure measurement accuracy, and there is a problem that equipment costs increase.

  In order to solve the above-mentioned problems, the present inventors have intensively studied. As a result, when the entire long material being hot transported is captured in the imaging field by one imaging of one camera, the imaging trigger is 1 After detection of image data on an actual long material using detection signals from individual detectors (for example, a HMD (Hot Metal Detector)) and lens distortion (aberration) that increases as the imaging field of view increases. Acquired the knowledge that good length measurement accuracy can be obtained even if one camera and one detector are installed by dealing with the dimensional error of the image by length conversion based on the image data of the light spot scale. The present invention has been made.

That is, the present invention is as follows.
(1) A method for measuring a length of a hot long material having various outer diameter dimensions, which is conveyed along a conveyance path,
It has an imaging field of view where the entire length of the hot long material falls within the field of view, and it is detected that the hot long material has been transported within the field of view of one imaging means that images a specific area of the transport path. And
At the time of the detection, obtain a still image of the hot long material imaged by the imaging means,
Light spot imaging data obtained by imaging the position in the length direction of the hot long material in the still image and the light spot scale in which the scale is arranged in the length direction of the hot long material in the specific region From the length conversion coefficient different in the two or more areas in the length direction in the image according to the outer diameter dimension of the hot long material , which is derived in advance by image processing,
A method for measuring a length of a hot long material, comprising calculating a length of the hot long material.
(2) It is a length measuring device for hot long materials having various outer diameter dimensions that are transported along a transport path,
An imaging field having an imaging field in which the entire length of the hot long material falls within the field of view;
Detecting means for detecting presence or absence of a hot long material at a specific position of the transport path, and detecting that the entire length of the hot long material is transported in the specific region;
Based on the detection signal of the detection means, obtain a still image including the entire length of the hot long material imaged by the imaging means,
Light obtained by imaging the position of the hot long material in the length direction of the acquired still image and the light spot scale in which the scale is arranged in the length direction of the hot long material within the imaging field of view. From the length conversion coefficient different in two or more areas in the length direction in the image according to the outer diameter size of the hot long material , which is derived in advance by image processing the point imaging data,
Image processing means for calculating the length of the hot long material;
A length measuring apparatus for hot long materials, comprising:

  According to the present invention, it is possible to reduce the measurement error due to lens distortion with the aid of the image processing means by installing each one of the imaging means and the detection means, and ensure the measurement accuracy of the hot long material. And equipment cost savings.

It is a schematic diagram which shows the time of hot long material imaging in one Embodiment of this invention. It is a schematic explanatory drawing which shows the derivation | leading-out point of a long material image and a long material image length. It is a schematic diagram which shows the time of the light spot scale image pick-up in one Embodiment of this invention. It is a schematic explanatory drawing which shows the derivation | leading-out point of the length conversion coefficient from a light spot scale image. It is a schematic explanatory drawing which shows the derivation | leading-out point of a long material image and a long material image length.

  In FIG. 1, which is a schematic diagram illustrating imaging of a long hot material in one embodiment of the present invention, the long material 1 is, for example, a steel pipe 1 on the exit side of a piercer mill (not shown). The steel pipe 1 is conveyed 3 in one direction by a conveyance path 2 composed of a conveyance roller group that horizontally conveys a material to be conveyed in the material length direction. Since the steel pipe 1 is hot, heat can be observed by the heat sensor 4, and the heat sensor 4 detects the presence or absence of the steel pipe at the specific position PS in the conveyance path 2.

  A single camera 5, which is an imaging means, is arranged to image a specific area B of the transport path 2, and a camera line of sight 6 that is the central axis of the imaging field of view SA is specified on the transport path 2. The region B is in a state of being orthogonal to the tube center axis when the steel pipe 1 is conveyed. And when the imaging distance L which is the shortest objective distance of the camera 5 is a predetermined distance, for example, 6500 mm, a length range in which the tube length is a maximum of, for example, 8500 mm among the various steel pipes 1 that are conveyed on the conveying path 2 in the imaging field of view SA. To fit.

In the present embodiment, the camera 5 is installed obliquely above the transport path 2 due to installation space limitations, but the present invention is not limited to this.
The thermal sensor 4, for example, the HMD 4 directs the thermal observation line of sight 7 toward the entrance point to the imaging field of view SA of the conveyance path 2, sets the entrance point as the specific position PS, and sets the specific position PS as the heat observation point. While taking the heat observation data of the steel pipe 1 between the passing heat, the obtained heat observation data is transmitted to the sequence control means 11. The sequence control means 11 automatically transmits an imaging trigger signal 9 to the image processing means 8 in response to the fall of the heat observation data. That is, the thermal sensor (HMD) 4 and the sequence control means 30 detect the presence or absence of a hot long material at a specific position PS on the conveyance path, and the total length of the hot long material (steel pipe 1) is within the specific region B. The detection means which detects having conveyed is comprised, and the said imaging trigger signal 9 turns into a detection signal which notifies that the full length of a hot long material was conveyed in the specific area | region B. FIG. The image processing means 8 is obtained by installing commercially available image processing application software on a commercially available personal computer system.

  The camera 5 always images the specific area B, and the primary imaging data 10 that is a moving image is sent to the image processing means. When the image processing unit 8 receives the imaging trigger signal 9 from the sequence control unit 30, the image processing unit 8 acquires a still image at the time of receiving the imaging trigger signal from the primary imaging data 10 (moving image data) sent from the camera 5. To do. Since the time required from the transmission of the imaging trigger signal 9 until the image processing means 8 acquires a still image is extremely small and can be ignored, the tail end portion of the steel pipe 1 in which the falling of the thermal observation data is hesitant at the time of still image acquisition Is located at the heat observation point (specific position PS), and the entire steel pipe 1 is within the imaging field of view SA. Therefore, the still image includes luminance information about the entire steel pipe 1.

Further, since the still image is a one-shot image pickup at a high shutter speed (about 4 ms), the image pickup data is not disturbed even if the conveyance speed is changed.
The image processing means 8 performs image processing on the still image to derive a long material image, and derives the long material image length from the long material image. The derivation procedure is shown in FIG. First, the luminance image 11 obtained by visualizing the luminance information of the still image is displayed on the screen 8D. In the screen 8D, the normal line of the screen corresponds to the camera line of sight 6, the X axis which is the horizontal axis of the screen corresponds to the parallel axis to the transport path 2, and the Y axis which is the vertical axis of the screen is transported from the camera line of sight 6. The screen setting corresponds to an axis perpendicular to the parallel axis of the path 2 (the same applies hereinafter). Therefore, the long material portion 11A in the luminance image 11 is displayed at a position substantially at the center on the Y axis of the screen.

  In the luminance image 11, the luminance of the long material portion 11 </ b> A is significantly higher than the luminance of the portion 11 </ b> B other than the long material portion, and therefore the long material portion 11 </ b> A and the long material portion 11 </ b> A are The boundary with the portion 11B other than the long material portion can be determined. Therefore, using the threshold value set in advance, the luminance is inspected in the Y-axis direction for the entire screen X-axis to identify the Y-axis region (referred to as region AY) whose luminance is equal to or greater than the threshold value, and the luminance in the X-axis direction for the region AY Inspection is performed to identify an X-axis region (referred to as region AX) having a luminance equal to or higher than a threshold value. The common part of the obtained area AX and area AY is an image of the long material portion 11A, that is, a long material image.

  The image processing means 8 continues to obtain the length of the long material (steel pipe 1) from the long material image. First, the X-axis of the pixels located at both ends of the long material image in the X-axis direction is used. The coordinates, that is, the tip end X coordinate X1 and the tail end X coordinate X2 are read. Assuming that the pixel size is δ, the number of pixels between the coordinates X1 to X2 is (X2−X1) / δ (= N), and this is the long material image length (Image Length) in units of the number of pixels. In other words, IL = N.

In order to convert the IL into the actual length of a long material (referred to as RL, which is an abbreviation of Real Length), the actual length per pixel (referred to as RLPP, which is an abbreviation of Real Length Per Pixel) is required.
If the camera is an ideal lens camera without lens distortion (aberration), RLPP does not depend on the pixel position in the screen, is determined by the lens magnification M and the pixel size δ, and RLPP = M × δ.
RL = RLPP × N = M × δ × N = M × (X2−X1) (1)
It becomes.

However, since an actual camera has lens distortion, RLPP is different between the central portion and the end portion in the X-axis direction of the long material image. For example, 4 mm / pixel at the center and 3.7 mm / pixel at both ends.
In general, RLPP is almost the same as in the case of an ideal lens at the center, but the deviation from the ideal lens increases toward the end. Therefore, since it is necessary for the RLPP to take into account the length conversion coefficient K that is a coefficient representing the deviation, in the present embodiment, the RLPP is divided into a long material image and two or more areas in the length direction in the long material image. The length of the hot long material is calculated from the different length conversion factors K. However, since RLPP is almost the same as that of an ideal lens at the center as described above, K = 1.

  In order to calculate the long material length RL from the long material image by obtaining different RLPPs depending on the X-axis direction area of the long material image as described above, in the present invention, in the present invention, the light in the cold stationary state in advance by the camera is used. The light spot imaging data obtained by imaging the point scale is subjected to image processing, and different length conversion coefficients are derived in two or more areas in the length direction. Calculate the length of the material. A method for deriving the length conversion coefficient (hereinafter also simply referred to as coefficient) will be described below.

  As shown in FIG. 3, which is a schematic diagram showing light spot scale imaging in one embodiment of the present invention, the light spot scale 14 is a cold and stationary state across the imaging field SA of the conveyance path 2. Placed on the road. The light spot scale 14 has a plurality of light spots 15 (for example, LEDs or bean bulbs) on a light spot array line 18 provided in the longitudinal direction of the outer surface of a long light spot carrier (for example, a polyvinyl chloride tube). These light spots 15 form a scale. The light spot alignment line 18 is parallel to the transport direction when the steel pipe 1 is transported. That is, the light spot scale 14 has scales arranged in the length direction of the long material. The reason why the scale is formed at the light spot 15 is to give the scale a luminance that enables imaging by the camera 5. Here, the graduations formed by the light spots 15 are equally spaced, but may not necessarily be equally spaced as long as the spacing is set to a known value. Further, although the total number of the light spots 15 is nine, it is not limited to this.

However, the phase in the circumferential direction of the light spot scale 14 is a phase in which the light spot array line 18 is orthogonal to the camera line of sight 6, and the distance L0 from the camera 5 to the light spot array line 18 at this time is a known value. (See FIG. 3B).
The imaging trigger signal 19 to the camera 5 is manually transmitted by manual transmission means 16 such as a push button switch. Upon receiving the transmission, the camera 5 immediately executes imaging, and transmits the obtained light spot imaging data 12 to the image processing means 8. The light spot imaging data 12 includes luminance information of a point sequence of the light spot 15.

  As shown in FIG. 4, the image processing means 8 first displays the light spot scale image 22 in which the luminance information of the light spot imaging data 12 is visualized on the screen 8D. The light spot scale image 22 is an image in which nine light spot images 22A are arranged in the X-axis direction. Therefore, an input means such as a mouse (not shown) is operated to click 24 at the center position of each light spot image 22A. Then, the image processing means 8 records the X-axis coordinates X (i) (; i = 1 to 9) of each light spot image 22A from the left to the right, and the area j (; X (j) to X (j + 1). ); The number of pixels N (j) = (X (j + 1) −X (j)) / δ for j = 1 to 8) is calculated. Then, from this number of pixels N (j) and the actual light spot scale interval L (j) corresponding to the zone j, which was input and stored when preparing the light spot scale image, RLPP (j) = L ( j) / N (j) is calculated.

As a result of the calculation, RLPP (1) ≈RLPP (8)> RLPP (2) ≈RLPP (7)> RLPP (3) ≈RLPP (4) ≈RLPP (5) ≈RLPP (6).
Accordingly, the areas 3 to 6 in the light spot scale image 22 are set as the central part C, and the coefficient K is set to K (C) = 1, and the areas 2 and 7 are set as the second end part E2 and the above-described coefficient is set there. The coefficient K is K (E2) = Mean (RLPP (j) (; j = 2,7)) / Mean (RLPP (j) (; j = 3 to 6)), and the areas 1 and 8 are As the one end E1, the coefficient K is K (E1) = Mean (RLPP (j) (; j = 1,8)) / Mean (RLPP (j) (; j = 3 to 6)) Remember each one.

Using the different coefficients K (C), K (E1), and K (E2) respectively corresponding to the central portion C thus stored and the first and second end portions E1 and E2, the long material image shown in FIG. From this, the long material length RL is calculated.
First, the distance L between the steel pipe 1 and the camera 5 at the time of measuring the length of the steel pipe (when imaging a long hot material) is equal to the distance L0 between the camera 5 and the light spot array line 18 at the time of imaging the light spot scale. The case will be described.

It is determined whether the X-axis coordinates X1 and X2 of the pixels located at both ends in the X-axis direction read from the long material image 11 are located at the center C, the first end E1, or the second end E2. . In the example shown in FIG. 5, the X-axis coordinate X1 of the pixel located at the tip of the long material image in the X-axis direction and the X-coordinate X2 of the pixel located at the tail end in the X-axis direction are respectively the second end E2 and the first. Present at end E1. Accordingly, the position of the long material in the X-axis direction in the image is between X1 in the area 2 and the light spot coordinate X (3), between the entire area 3 to the area 7 (light spot coordinates X (3) to X ( 8)), between the light spot coordinates X (8) and X2 in the area 8. Therefore, the long material length RL is calculated by the following equation (2) from the X-axis coordinates X (i) and the coefficients K (C), K (E1), and K (E2) of each light spot image. Is done.
RL (mm) = M × (X (3) −X1) × K (E2)
+ M × (X (7) −X (3)) × K (C)
+ M × (X (8) −X (7)) × K (E2)
+ M × (X2−X (8)) × K (E1) (2)
That is, the long material length RL is calculated by summing the length of the long material in each X-axis direction area on the still image multiplied by the coefficient K and the magnification M for each area.

  The distance L (see FIG. 1B) between the steel pipe 1 and the camera 5 at the time of measuring the length of the steel pipe (at the time of imaging a hot long material) is an array line of the camera 5 and the light spot 15 at the time of imaging the light spot scale. For an assembly equal to the distance L0 (see FIG. 2B) with respect to 15a, the magnification M when displayed on the screen 8D is the same between the image of the steel pipe 1 and the image of the light spot scale 14. The RL obtained by the above equation (2) can be used as the measurement result of the steel pipe 1 as it is. For example, when the outer diameter of the steel pipe 1 conveyed by the conveyance path 2 is only one type, if the above L and L0 are set equal, the RL according to the above equation (2) is measured by the steel pipe 1. Long result.

  However, when there are various outer diameters as the steel pipe 1 conveyed through the conveyance path 2, the steel pipe 1 and the camera at the time of the side length of the steel pipe (at the time of hot long material imaging) according to the outer diameter dimension. Since the distance L to 5 changes, the magnification M when displayed on the screen 8D also changes. Therefore, when the steel pipe 1 to be conveyed has various outer diameters, the RL obtained by the above equation (2) is corrected according to the outer diameter.

  Specifically, the image processing means 8 is inputted with the value of the outer diameter D as information relating to the steel pipe 1 being conveyed from the above computer (not shown), and the image processing means 8 The distance L (D) between the camera 5 and the steel pipe 1 corresponding to the outer diameter D of the steel pipe 1 is registered in advance. Since the magnification when the distance between the camera 5 and the steel pipe 1 is L0 is M, the magnification M when the distance between the camera 5 and the steel pipe 1 is L (D) is M × L (D) / L0. Depending on the value of the outer diameter D, the true length measurement result can be obtained by correcting the value of RL obtained by the above equation (2) with the following equation (3) to obtain RL ′.

RL ′ = RL × L (D) / L0 (3)
Note that the value of L corresponding to the outer diameter of the steel pipe 1 may be geometrically calculated in advance and registered in the image processing means 5.

  In the seamless steel pipe production line, the steel pipes (hollows) that are hot transported on the piercer mill exit side are conventionally the most upstream side from the thermal observation data by HMD, HMD position coordinates and pipe transport speed arranged in the transport direction. The length was measured by interpolation calculation of the downstream HMD position coordinates that coincide with the pipe tip position at the time of HMD pipe tail end detection, but the length measurement accuracy is not sufficient, and the length measurement result is Sometimes rolling defects occurred in the operation used to set up the rolling mill.

  The present invention was implemented in the form of FIG. The camera used was Toshiba Terry CSC12M25BMP19, and the lens used was Nikon Nikkor 14 mm. It takes an extremely short time of 17 ms from the camera imaging of the steel pipe to the length calculation. After implementation of the present invention, the rolling defect no longer occurred. In addition, since one camera and one HMD were installed, the effect of reducing equipment cost and maintenance load was also realized.

1 Steel pipe (hot long material)
2 Conveying path (conveying roller group)
3 Transport 4 Thermal sensor (HMD)
5 Camera (imaging means)
6 Camera line of sight 7 Thermal observation line of sight 8 Image processing means 8D Screen 9 Imaging trigger signal 10 Primary imaging data 11 Luminance image 11A Long material part 11B Non-long material part 12 Light spot imaging data 14 Light spot scale 15 Light Point (LED or miniature bulb)
16 Manual transmission means (push button switch)
18 Light spot array line 19 Imaging trigger signal 22 Light spot scale image 22A Light spot image 30 Sequence control means PS Specific position (thermal observation point)
SA Imaging field of view B Specific area

Claims (2)

A method for measuring a hot long material of various outer diameters that is transported through a transport path,
It has an imaging field of view where the entire length of the hot long material falls within the field of view, and it is detected that the hot long material has been transported within the field of view of one imaging means that images a specific area of the transport path. And
At the time of the detection, obtain a still image of the hot long material imaged by the imaging means,
Light spot imaging data obtained by imaging the position in the length direction of the hot long material in the still image and the light spot scale in which the scale is arranged in the length direction of the hot long material in the specific region From the length conversion coefficient different in the two or more areas in the length direction in the image according to the outer diameter dimension of the hot long material , which is derived in advance by image processing,
A method for measuring a length of a hot long material, comprising calculating a length of the hot long material. It is a length measuring device for hot long materials of various outer diameters that are transported through a transport path,
An imaging field having an imaging field in which the entire length of the hot long material falls within the field of view;
Detecting means for detecting presence or absence of a hot long material at a specific position of the transport path, and detecting that the entire length of the hot long material is transported in the specific region;
Based on the detection signal of the detection means, obtain a still image including the entire length of the hot long material imaged by the imaging means,
Light obtained by imaging the position of the hot long material in the length direction of the acquired still image and the light spot scale in which the scale is arranged in the length direction of the hot long material within the imaging field of view. From the length conversion coefficient different in two or more areas in the length direction in the image according to the outer diameter size of the hot long material , which is derived in advance by image processing the point imaging data,
Image processing means for calculating the length of the hot long material;
A length measuring apparatus for hot long materials, comprising:

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