Patent Grant
11055858
This disclosure relates to a method and apparatus for measuring a meandering amount of a strip during conveyance thereof and further to a method and apparatus for detecting abnormal meandering of the strip based on the measured results.
In the production of a steel sheet as a strip, the steel sheet may be conveyed over a long distance. For example, a furnace for annealing the steel sheet is disposed in a continuous annealing equipment for annealing the steel sheet subjected to rolling or the like, and a heating zone, a soaking zone, a cooling zone and so on are sequentially arranged in the furnace from an upstream side in the conveyance direction of the steel sheet. In conducting annealing in a vertical furnace while folding the steel sheet up and down, a central position of the steel sheet can be adjusted by deflector rolls, steering rolls and the like during the conveyance. On the other hand, in conducting annealing in a horizontal furnace as shown in
As a method of detecting meandering of the steel sheet during conveyance has hitherto been known a method wherein the steel sheet is shot with an imaging means such as CCD camera or the like and an edge position of the steel sheet is automatically detected by processing the shot image to obtain shifting amount of the edge position from the standard position as a meandering amount.
As such a technique, JP H04-225107 A proposes a method wherein CCD cameras are arranged above both edges of the steel sheet and light sources are arranged behind the steel sheet in correspondence to the CCD cameras and light is irradiated from the light source toward the CCD camera to detect the edge of the steel sheet.
In the method of JP '107, however, the CCD camera is arranged right above the steel sheet and the light source is arranged right below the steel sheet so that dust such as metal powder and the like scattering in association with the conveyance of the steel sheet is apt to be adhered to the lens of the CCD camera and the light source to cause operation failure, false detection or the like. To avoid this problem, the CCD camera and so on can be arranged on a truck capable of drawing toward the outside of the line, whereby the dust adhered to the CCD camera or the like can be periodically removed even in the operation. However, such a countermeasure has a drawback that the truck, laying of rails guiding the truck, securing existing floor to position the truck, improvement of beams and, if necessary, change of the existing pass line are required to bring about the excessive investment cost. In addition, as being arranged in places easily subjected to an influence of heat from the steel sheet, CCD camera and the light source may be damaged early due to heat from the steel sheet. Therefore, it necessary to separately arrange a water-cooling equipment to protect the CCD camera or the like by cooling.
It could therefore be helpful to provide a method and apparatus for measuring a meandering amount of a strip and a method and apparatus for detecting abnormal meandering of the strip capable of reducing troubles such as operation failure and false detection by suppressing adhesion of dust to the imaging means and lights and can decrease heat load to the imaging means and the lights to suppress an increase in cost.
We thus provide:
A method of measuring a meandering amount of a strip during conveyance thereof, wherein an imaging means is arranged in one side of the strip at a state of tilting an optical axis thereof to a pass line plane of the strip and a lighting is arranged in the other side of the strip to irradiate light to the strip from the back of the strip viewing from the imaging means, and the strip is shot by the imaging means from an obliquely side to include both edges of the strip and the edge of the strip is detected with an image shot by the imaging means and a meandering amount of the strip from a standard position is calculated based on the detected edge position information of the strip.
It is preferable that the lighting and the imaging means are arranged at the same positions in the conveyance direction of the strip and an optical axis of the lighting is shifted to an optical axis of the imaging means toward an upstream side or a downstream side in the conveyance direction of the strip.
It is preferable that the meandering amount of the strip is regressively measured from the detected edge position information of the strip.
The apparatus that measures a meandering amount of a strip during conveyance thereof, comprises
an imaging means arranged in one side of the strip and having an optical axis tilted to a pass line plane of the strip for shooting the strip from an obliquely side to include both edges of the strip,
a light irradiating light to the strip from the back of the strip viewing from the imaging means, and
an image processing device that processes an image shot by the imaging means to detect the edge of the strip and calculate a meandering amount of the strip from a standard position based on the detected edge position information of the strip.
It is preferable that the light and the imaging means are arranged at the same positions in the conveyance direction of the strip and an optical axis of the light is shifted to an optical axis of the imaging means toward an upstream side or a downstream side in the conveyance direction of the strip.
It is preferable that the image processing device is configured to regressively obtain the meandering amount of the strip from the detected edge position information of the strip.
The method of detecting abnormal meandering lies in that abnormal meandering is judged when a meandering amount measured in the aforementioned method of measuring a meandering amount exceeds a predetermined abnormal judgement value.
The apparatus that detects abnormal meandering comprises any one of the aforementioned apparatuses that measure a meandering amount and is configured so that the image processing device judges abnormal meandering when the measured meandering amount exceeds a predetermined abnormal judgement value.
In the method and apparatus for measuring a meandering amount, the lighting irradiates light to transmit the light from the edge of the strip, and the imaging means shoots the strip including the edge, and the image processing device detects the edge from the shot image and measures the meandering amount of the strip based on the detected edge position information. The abnormal meandering is judged by comparing the measured meandering amount with the predetermined abnormal judgement value.
The imaging means is arranged in one side of the strip, and the lighting is arranged in the other side of the strip, or the imaging means and the lighting are not located right above and below the strip so that there can be reduced operation failure due to the adhesion of dust and so on scattering in association with the conveyance of the steel sheet to lens of the imaging means and the lighting. Accordingly, the truck and rail that draws the imaging means and the light toward outside and the reconstruction of the existing equipment associated therewith can be made unnecessary, and cost required for the introduction of devices can be reduced. Also, even when the temperature of the strip is high, the side of the strip arranged with the imaging means and the light has a low temperature compared to positions right above and below the strip so that water cooling device for the imaging means and the light can be made unnecessary. Furthermore, the imaging means and the light are arranged outside the line so that there is a merit that repair and adjustment of the imaging means and the lighting can be performed during the operation without stopping the operation and maintenance thereof can be performed easily.
Therefore, it is possible to solve the problems of the conventional technique and provide the method and apparatus for measuring a meandering amount of a strip and the method and apparatus for detecting abnormal meandering of a strip which are capable of suppressing the adhesion of dust to the imaging means and the light to reduce trouble such as operation failure and false detection and reducing heat load to the imaging means and the lighting to suppress an increase in cost.
An example will be described in detail with reference to the drawings below.
In the continuous annealing equipment, a furnace body 1 as shown in
The apparatus 10 that detects abnormal meandering according to this example possesses a function as an apparatus 12 that measures a meandering amount. The apparatus 10 measures a meandering amount of the steel sheet as an example of a strip travelling a conveyance roll and detects abnormal meandering based on the measured meandering amount. As a constructional example thereof is shown in
The camera 14 is arranged in one side of the steel sheet (e.g., driving side) at a state of tilting its optical axis 14c to a pass line plane PL of the steel sheet. As an arrangement example is concretely shown in
The tilting angle θ of the optical axis 14c of the camera 14 to the pass line plane PL is preferably not less than 10 degrees but not more than 60 degrees. When the tilting angle θ is less than 10 degrees, an interval between both edges of the steel sheet becomes too narrow in a shooting area of the camera 14, and the edge of the steel sheet may not be detected accurately in the processing of the image. On the other hand, when the tilting angle θ exceeds 60 degrees, the arranging position of the camera 14 becomes higher, and a distance to the steel sheet is increased associated therewith, and hence the detecting accuracy of the edge may decrease. Also, it may be necessary to reconstruct the mount or the like to arrange the camera 14 in a high position, leading to the increase of the cost.
The light 16 is a bar type LED light, for example, formed by arranging plural LEDs in line. It is arranged in the other side of the steel sheet (a side opposite to the side arranging the camera, or an operation side in this example) and irradiates a light to the steel sheet from behind the steel sheet viewing from the camera 14. The light 16 is not limited to the LED light, and a bar type fluorescent lamp or the like may be used. The light 16 can be fixed to a pole or the like located between the adjacent conveyance rolls 24 in the conveyance direction through a clamp or the like and is preferable to be arranged at a state of tilting to the pass line plane PL to face the camera 14 as shown by an front view in
As shown by a plan view of the conveyance line in
The image processing device 18 is constructed with a computer comprising a memory for storing various programs, CPU for running these programs and so on, and has a function of automatically detecting the edge by processing an image shot by the camera 14, a function of measuring a meandering amount of the steel sheet from the detected edge, and a function of outputting the measured result to a monitor or the like. Therefore, the image processing device 18 constructs the apparatus 12 of measuring a meandering amount according to the example in cooperation with the camera 14 and the light 16. The image processing device 18 further has a function of judging abnormal meandering based on the measured meandering amount and a function of outputting a signal for decreasing a line speed to a line control device when the abnormality is judged. Therefore, the image processing device 18 constructs the apparatus 10 that detects abnormal meandering according to the example in cooperation with the camera 14 and the light 16.
The monitor 22 displays an image shot by the camera 14 and can further display a detection line passing through the detected edge position and extending along the conveyance direction in superimposition with the image (see
In step S1, images are first obtained by continuously shooting the steel sheet with the camera 14 from obliquely side to include both edges of the steel sheet.
In step S2, the image obtained in step S1 is processed to detect both edges of the steel sheet.
In step S3, positions of both edges of the steel sheet detected in step S2 and a central position of the steel sheet are calculated. The both edge positions and central position of the steel sheet can be determined described below, considering an inclination of the optical axis 14c of the camera 14 to the pass line plane PL.
First, a point where the optical axis 14c of the camera 14 intersects with the pass line plane PL is determined as the original point O. In this example, the original point O is also a point where a near side edge of the steel sheet viewed from the camera 14 is positioned in an accepted maximum meandering of the steel sheet (hereinafter called as a near side edge simply). Moreover, the original point O is not limited to the above and may be, for example, a central position of the strip in the widthwise direction.
When the pixel number of the image sensor of the camera 14 in the vertical direction (size in the longitudinal direction of the image sensor) is determined as Pv and a focal length is determined as f and a working distance is determined as WD and the pixel number of the edge position in the image sensor is determined as P and an angle between the optical axis 14c of the camera 14 and the pass line plane PL is determined as θ, distances Yp and Yd from the original point O to edge positions of the steel sheet in the widthwise direction along the pass line plane PL are measured by equation (1). Yp is a distance from the original point O to a near side edge along the pass line plane, and Yd is a distance from the original point O to a back side edge (hereinafter called as back-side edge simply) along the pass line plane.
Also, a distance Yc from the original point O to a widthwise central position of the steel sheet can be determined from an equation: Yc=(Yp+Yd)/2.
Accordingly, a meandering amount Sp of the steel sheet obtained from position information of the near side edge is determined from another equation: Sp=Yp−Ypb, wherein a distance from the original point O to a standard position of the near side edge is Ypb. Similarly, a meandering amount Sd of the steel sheet obtained from position information of the back side edge is determined from another equation: Sd=Yd−Ydb, wherein a distance from the original point O to a standard position of the rear side edge is Ydb. A meandering amount Sc of the steel sheet obtained from information of widthwise central position of the steel sheet is determined from another equation: Sc=Yc−Ycb, wherein a distance from the original point O to a standard position of widthwise center of the steel sheet is Ycb.
The detection line passing through the detected edge position (detected point) and extending in the conveyance direction can be displayed, for example, by green dotted line in the monitor 22 as shown in
In step S4, the judgement of abnormal meandering is conducted based on at least one of the meandering amounts measured in step S3. Concretely, the meandering is judged to be “large” or “abnormal” when the measured meandering amount surpasses a predetermined judgement value by comparing the measured meandering amount to the previously set judgement value. When the abnormal meandering is judged (“YES” in step S4), an alarm transmission such as an alarm lamp is generated and control signals for avoiding abnormal meandering such as line speed decreasing signal and line stop signal is output to a line control device in step S5. Also, when abnormal meandering is detected, green detection line showing each edge position can be changed to yellow or red in the monitor 22.
When the meandering amount is judged to be not more than the predetermined judgement value and within an acceptable range in step S4 (“NO” in step S4), the above treatment is continued after the returning to step S1.
By the aforementioned treatment, the meandering amount of the steel sheet can be measured and the abnormal meandering can be detected.
In the method and apparatus for detecting abnormal meandering according to this example, the camera 14 and the light 16 are arranged outside the line (at the side of the steel sheet) so that dust and so on scattering in association with the conveyance of the steel sheet are adhered to lens of the camera 14 and the light 16 to cause operation failure can be reduced. Thus, trucks and rails for drawing the camera 14 and the light 16 toward the outside of the line and reconstruction of the existing equipment associated therewith can be made unnecessary and the cost of introducing the devices can be suppressed. Even when the temperature of the steel sheet is high, the temperature of the side of the steel sheet arranging the camera 14 and the light 16 is lower than that of right above and below the steel sheet so that water cooling device for the camera 14 and the light 16 can be made unnecessary. Since the camera 14 and the light 16 are arranged outside the line, the repairing and adjustment of the camera 14 and the light 16 can be conducted during the operation without stopping the operation so that there is a merit that the maintenance can be conducted easily.
In step S3 of the preceding example, the meandering amount of the steel sheet is geometrically determined by equation (1), in consideration of the tilting θ of the optical axis 14c of the camera 14 to the pass line plane PL. In the method and apparatus 12 for measuring a meandering amount and the method and apparatus 10 for detecting abnormal meandering according to this example, the meandering amount is determined by applying the pixel number (pixel position) of the edge position of the steel sheet detected by the camera 14 to the regression formula. As shown, for example, in
In the method and apparatus 12 for measuring a meandering amount and the method and apparatus 10 for detecting abnormal meandering according to this example, the image processing device 18 is configured to obtain a pixel number of the detection position of the steel sheet edge in step S2 of
When the meandering amount of the steel sheet is determined regressively from the pixel number of the detection position of the steel sheet edge, the pixel numbers of the edge detection position at both the side portions of the steel sheet may be used, but the pixel number of the edge detection position at the one side portion may be used. In the latter example, the use of the pixel number of the edge detection position at the side near to the camera 14 (near side viewing from the camera 14) is preferable because error is small.
As an example, a meandering amount of a steel sheet having a width of 1000 mm, a thickness of 0.5 mm and a surface temperature of 150° C. is measured with an apparatus 12 for measuring a meandering amount having a configuration shown in
As an imaging means is used a CCD camera (area camera) 14 wherein the pixel number in the up and down direction (vertical direction) is 4096 pixels and the pixel number in the horizontal direction (lateral direction) is 5104 pixels. A tilting angle θ of an optical axis 14c of the CCD camera 14 to a pass line plane PL of the steel sheet is 20 degrees. As a light 16 is used a bar type LED light having a length of 2000 mm, which is tilted by 20 degrees to the pass line plane PL to face to the CCD camera 14 and arranged so that an optical axis 16c of the light 16 is shifted by 5 degrees toward an upstream side in the conveyance direction.
A standard position Ypb of near side edge of the steel sheet is at a position 417 mm from the original point O, and a central standard position Ycb of the steel sheet is at a position 917 mm from the original point O, and a standard position Ydb of the back side edge of the steel sheet is at a position 1417 mm from the original point O.
In this example, various coefficients set in the measurement of the meandering amount and the detection of abnormal meandering are shown in a coefficient setting table shown as Table 1. Moreover, each judgement value in this table is a distance from the original point O.
The measurement of a meandering amount and detection of abnormal meandering are performed by using the apparatus 10 that detects abnormal meandering with the above configuration and settings. The edges can be automatically detected at a detection accuracy of about 1.25 mm (pixel resolution of about 1.25 mm) in the near side edge position (driving side) and a detection accuracy of about 5 mm (pixel resolution of about 5 mm) in the back side edge position (operation side). As shown by a trend graph in
Therefore, meandering of the steel sheet can be detected by a simple device with a configuration using one CCD camera 14 and one lighting 16. Since the CCD camera 14 and the light 16 are arranged in the side of the steel sheet having a relatively low temperature, water cooling for the CCD camera 14 and the light 16 is unnecessary. Furthermore, the adhesion of dusts and so on to the lens of the CCD camera 14 and the light 16 is hardly recognized. Since the optical axis 16c of the light 16 is shifted by 5 degrees toward an upstream side in the conveyance direction, incident of reflected light of the lighting 16 to the CCD camera 14 can be prevented, and hence the edge detection can be performed well.
The imaging means and the lighting for detecting meandering of a strip are arranged outside the line (at the side of the strip), and the strip is shot at a state of tilting the imaging means to the pass line plane so that it is possible to suppress the adhesion of dusts to the imaging means and the light to reduce troubles such as operation failure and false detection, and also it is possible to decrease heat load to the imaging means and the lighting to suppress an increase in cost.
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| WO2018/168700 | 9/20/2018 | WO | A |
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