JP2004037253A - Method for measuring thickness of metal strip - Google Patents

Method for measuring thickness of metal strip Download PDF

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Publication number
JP2004037253A
JP2004037253A JP2002194746A JP2002194746A JP2004037253A JP 2004037253 A JP2004037253 A JP 2004037253A JP 2002194746 A JP2002194746 A JP 2002194746A JP 2002194746 A JP2002194746 A JP 2002194746A JP 2004037253 A JP2004037253 A JP 2004037253A
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Japan
Prior art keywords
thickness
radiation
measurement result
laser
gage
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JP2002194746A
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Japanese (ja)
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JP3940327B2 (en
Inventor
Hiroyasu Mitsuoka
光岡 宏恭
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Nippon Steel Corp
新日本製鐵株式会社
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a thickness measuring method for metal strips which measures the thickness of a metal strip of high temperature being conveyed with high precision stably, by combining a radiation thickness gauge and a laser thickness gauge. <P>SOLUTION: The thickness of approximately the same positions of the metal strip being conveyed are measured with the radiation thickness gauge and the laser thickness gauge, and a drift error of the laser thickness gauge is compensated by using a measurement result of the radiation thickness gauge. In a period when the radiation thickness gauge is stable, a thickness value obtained by passing a measurement result of the radiation thickness gauge through a low pass filter at a specific time after its passage, can be used as a final measurement result of the radiation thickness gauge. Besides, in a period when the radiation thickness gauge is stable, a thickness value obtained by passing a measurement result of the radiation thickness gauge through the low pass filter, is used as its final measurement result. To this value, a measurement result of the laser thickness gauge having been passed through a high pass filter, is added to obtain a final measurement result. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a metal plate thickness measuring method capable of stably and accurately measuring the thickness of a conveyed high-temperature metal plate.
[0002]
[Prior art]
As a method for measuring the thickness of a metal plate having a high temperature in a non-contact manner, a method using a radiation thickness gauge as shown in FIG. 6 or a laser thickness gauge as shown in FIG. 7 is generally known. I have. A radiation thickness gauge is a device in which a radiation source that generates radiation and a detector that detects radiation are opposed to each other with a metal plate to be measured interposed between them. Is used to measure the thickness of the metal plate. This radiation thickness gauge has the advantage that the measurement result is stable against temperature changes, but the time constant is large, for example, about 0.4 seconds, so it cannot respond to fine plate thickness fluctuations of the measurement target, and the beam diameter is, for example, Since the beam is as large as about 50 mm, the beam partially misses the metal plate at the front and rear ends of the metal plate, and there is a problem that an error occurs at the front and rear ends of the metal plate due to a large time constant. Was.
[0003]
On the other hand, the laser thickness gauge has a laser displacement gauge attached to a frame opposed to a metal plate to be measured. A laser displacement meter irradiates a metal plate with laser light and measures the distance from the reflected light to the metal plate based on the principle of triangulation. The thickness of the metal plate is determined from the distance to the metal plate. The laser thickness meter has a small time constant of, for example, about 0.01 second, so that it can measure a short-term plate thickness variation of a measurement object. There is an advantage that the error generated at the end portion is small, but there is a problem that a temperature change causes the frame on which the laser displacement meter is mounted to bend and the distance between the laser displacement meters changes, thereby causing a drift error.
[0004]
[Problems to be solved by the invention]
The present invention combines a radiation thickness gage and a laser thickness gage which have these contradictory advantages and disadvantages, and can measure the thickness of a metal plate with a high temperature being conveyed stably and accurately. This was done to provide a way.
[0005]
[Means for Solving the Problems]
The thickness measurement method for a metal plate of the present invention made in order to solve the above-described problem is to measure a thickness of a metal plate to be transported at almost the same position by using a radiation thickness gauge and a laser thickness gauge, and The drift error of the laser thickness gauge is corrected using the measurement result of the thickness gauge. The measurement results of the radiation gage used for correcting drift errors of the laser thickness gage are calculated at a specific point in time after the measurement results of the radiation gage are passed through a low-pass filter during the period when the gage is unstable. The measurement result of the radiation gage used for correcting drift errors of the laser thickness gage is a low-pass measurement result of the radiation thickness gage when the radiation gage is stable. The measurement result of the laser thickness meter passed through the high-pass filter can be added to the data.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described with reference to the drawings.
FIGS. 1 to 3 show an example of the configuration of a measuring apparatus used in carrying out the present invention, in which a radiation thickness gauge and a laser thickness gauge are arranged as shown in FIG. That is, the metal plate W to be measured is transported through the opening of the U-shaped frame 1 in a direction perpendicular to the plane of the drawing by transport means (not shown). A first laser displacement gauge 3 forming a laser thickness gauge is provided on the lower side of the frame 1, and a detector 4 forming a radiation thickness gauge and a second laser displacement meter 5 forming a laser thickness gauge are mounted on the frame. 1 are installed on the upper side. Here, the radiation thickness gauge and the laser thickness gauge are arranged so as to measure almost the same position on the metal plate.
[0007]
When it is difficult to arrange the radiation thickness gage and the laser thickness gage to measure almost the same position on the metal plate due to restrictions on the physical dimensions of the radiation gage and the laser thickness gage, It is preferable to arrange a radiation thickness gauge and a laser thickness gauge as shown in FIG. FIG. 2 is a view from the side, in which the metal plate W is conveyed rightward or leftward in the figure, and the radiation thickness gage and the laser thickness gage are separated from each other in a straight line in the conveyance direction of the metal plate W. It is arranged. Thereby, the radiation thickness gauge and the laser thickness gauge measure the same position of the metal plate W at different times.
[0008]
By processing the detection signal of the detector 4 constituting the radiation thickness gage arranged as described above, the measurement result of the plate thickness by the radiation thickness gage is obtained, and the first laser displacement constituting the laser thickness gage is obtained. By processing the detection signals of the total 3 and the second laser displacement meter 5, the measurement result of the plate thickness by the laser thickness gauge can be obtained. The configuration for obtaining the measurement result of the plate thickness from the detection signal of the detector 4 and the configuration for obtaining the measurement result of the plate thickness from the detection signals of the first laser displacement meter 3 and the second laser displacement meter 5 are conventionally known. It is the same as the thickness gauge and the laser thickness gauge, and the description is omitted.
[0009]
The measurement results of the obtained radiation thickness gage and laser thickness gage have been input to the arithmetic unit 6. The arithmetic unit 6 is configured as shown in FIG. 3, for example. The measurement result by the radiation thickness meter is input to the low-pass filter 7, and the measurement result of the laser thickness meter is input to the low-pass filter 8 and the high-pass filter 9, respectively. Outputs of the low-pass filters 7 and 8 and the high-pass filter 9 are input to memories 10, 11 and 12, respectively, and are stored in time series by the memories 10, 11 and 12, respectively. The measurement results of the laser thickness gauge are simultaneously input to the memory 13 and stored by the memory 13. The outputs of the memories 10, 11, 12, and 13 are input to an adder / subtractor 14. Such an arithmetic unit 6 can be configured by a combination of computer hardware and software.
[0010]
When a metal plate whose thickness changes in the length direction is passed through the measuring device configured as described above, the plate thickness at the measurement point is obtained as time-series data that changes with time. When passing through a metal plate having a thickness such that a measurement result is obtained with a waveform as shown in FIG. 4A when measured with an ideal measuring instrument, the radiation thickness meter measures the waveform as shown in FIG. 4B. As a result, a measurement result of a waveform as shown in FIG. 4C is obtained by the laser thickness meter. Since the radiation thickness meter has a large time constant and a large beam diameter, an error occurs in the measurement result at the leading end and the trailing end of the metal plate, and the plate thickness fluctuation having a short cycle cannot be accurately measured. Further, in the laser thickness meter, the frame 1 is heated by the metal plate having a high temperature to bend, and the distance between the laser displacement meters changes, thereby causing a long-period drift error in the measurement result. When the radiation thickness meter and the laser thickness meter are arranged as shown in FIG. 2, the waveform of the measurement result by the radiation thickness meter and the waveform of the measurement result by the laser thickness meter are shifted on the time axis. The time axis can be easily adjusted when the data is stored in or read from the memories 10, 11, 12, and 13.
[0011]
Since each measurement result and other waveforms can be represented by a function of time, the measurement result by the radiation thickness meter is f (t), the measurement result by the laser thickness meter is g (t), and the low pass filter 7 The output is f LP (t), the output of the low-pass filter 8 is g LP (t), the output of the high-pass filter 9 is g HP (t), and the final measurement result is h (t). The measurement result of the radiation thickness gauge becomes stable a certain time after the measurement of the metal plate is started, and becomes unstable after a certain time before the measurement of the metal plate is completed. Therefore, the time when the radiation thickness gauge started measuring the metal plate is Ta, the time when the measurement result is stable is Tb, the time when the measurement result is maintaining a stable state is Tc, and the time when the measurement is finished is Td. I do.
[0012]
Since it is difficult to actually specify the time Tb at which the measurement result is stabilized and the time Tc at which the measurement result is maintained at a stable state, Tb and Tc are determined from the measurement start time Ta and the measurement end time Td. Assuming that the time constant of the radiation thickness meter is τ, Tb is the time after elapse of τ from Ta, and it is assumed that Tb = Ta + τ + α after elapse of a certain time α in consideration of sufficient stability. Tc is a time point before Td, and Tc = Td−β is set for a further predetermined time β in consideration of sufficient stability.
[0013]
5A and 5B show waveforms of various parts in the arithmetic unit 6. FIG. 5A shows the output f LP (t) of the low-pass filter 7, FIG. 5B shows the output g LP (t) of the low-pass filter 8, and FIG. The output is g HP (t). The output f LP (t) of the low-pass filter 7 is obtained by extracting only a change in a long cycle of the measurement result f (t) by the radiation thickness meter, and from the time Tb to Tc, an accurate average of the metal plate is obtained. This means that the thickness has been measured. The output g LP (t) of the low-pass filter 8 is obtained by extracting only a long-period change of the measurement result g (t) by the laser thickness meter, and the average thickness of the metal plate is measured. However, the drift of the laser thickness gauge is included. The output g HP (t) of the high-pass filter 9 is obtained by excluding the change in the long cycle of the measurement result g (t) by the laser thickness meter, and is the change in the thickness in the short cycle.
[0014]
The outputs f LP (t) and g LP (t) of the low-pass filters 7 and 8 and the output g HP (t) of the high-pass filter 9 are stored in the memories 10, 11 and 12 in time series. The measurement result g (t) by the laser thickness gauge is stored in the memory 13. The waveforms stored in the memories 10, 11, 12, and 13 are calculated by the adder / subtractor 14 to obtain a final thickness measurement result h (t) shown in FIG. 5D.
[0015]
Until Tb, the measurement result of the radiation thickness gauge is not sufficiently stable, and the measurement result of the laser thickness gauge includes a drift error. Therefore, the error of the laser thickness gauge is corrected using the measurement result of the average thickness by the radiation thickness gauge at the time point Tb. Next, during the period from Tb to Tc, the measurement result of the radiation thickness meter is sufficiently stable, so that the error of the laser thickness meter is corrected based on the measurement result of the average thickness by the radiation thickness meter. Furthermore, since the measurement result of the radiation thickness gauge is not sufficiently stable after Tc, the error of the laser thickness gauge is corrected using the measurement result of the average thickness by the radiation thickness meter at the time of Tc.
[0016]
When this is expressed and expressed and arranged,
When t <Tb h (t) = g (t) −g LP (Tb) + f LP (Tb)
When Tb ≦ t ≦ Tc h (t) = g HP (t) + f LP (t)
When Tc <t h (t) = g (t) −g LP (Tc) + f LP (Tc)
Thus, the adder / subtractor 14 takes in the required signal at each point in time, performs an operation, and outputs a final measurement result. It goes without saying that this final measurement result can be stored in a memory.
[0017]
In the above equation, f LP (Tb) and the like represent the value of f LP (t) at the time of t = Tb, and data of the time-series stored f LP (t) at the time of Tb is read. Is obtained by As described above, the measurement result is obtained by calculating from the waveforms stored in the memories 10, 11, 12, and 13 after the actual measurement is completed, and is not intended to perform real-time measurement. During the period from Tb to Tc, a measurement value for correction is obtained at the time point of Tb, so that measurement in real time is possible. Further, before Tb, the elapsed time after the start of measurement is short, and the accumulation of drift error is small. Therefore, if a slight error is allowed, the measurement can be performed in real time using the measurement result of the laser thickness gauge as it is. Furthermore, a measurement value for correction can be obtained by detecting the time point of Tc, for example, by providing a sensor for detecting the rear end of the metal plate in the transporting device, and measurement in real time can be performed after Tc. It becomes possible and all measurements can be made in real time.
[0018]
【The invention's effect】
As described above, according to the present invention, a radiation thickness gage that is stable with respect to a temperature change is obtained by using a laser thickness gage that can accurately measure a short-period plate thickness variation and a front end and a rear end of a metal plate. The thickness of the metal plate can be stably and accurately measured because the correction is made based on the measurement result of (1). Therefore, the present invention provides a method for measuring the thickness of a metal plate that has solved the conventional problems, and has a great industrial value.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of an arrangement of a thickness gauge of a measuring device used when carrying out the present invention.
FIG. 2 is a diagram showing another example of the arrangement of the thickness gauge.
FIG. 3 is a block diagram illustrating an example of a configuration of an arithmetic device.
FIG. 4 is a diagram showing a measurement result by a thickness gauge.
FIG. 5 is a diagram showing a waveform inside an arithmetic unit.
FIG. 6 is a diagram showing an example of a radiation thickness meter.
FIG. 7 is a diagram showing an example of a laser thickness gauge.
[Explanation of symbols]
1 Frame 2 Source 3 First laser displacement meter 4 Detector 5 Second laser displacement meter 6 Computing device 7, 8 Low-pass filter 9 High-pass filter 10, 11, 12, 13 Memory 14 Adder / subtractor

Claims (3)

  1. Measure the thickness of the conveyed metal plate at almost the same position using the radiation thickness gage and the laser thickness gage, and correct the drift error of the laser thickness gage using the measurement results of the radiation thickness gage. Characteristic metal plate thickness measurement method.
  2. The measurement result of the radiation gage used to correct the drift error of the laser thickness gage is calculated at a specific point in time after the measurement result of the gage is passed through a low-pass filter during the period when the gage is unstable. The method for measuring the thickness of a metal plate according to claim 1, wherein:
  3. The measurement results of the radiation gage used to correct drift errors of the laser thickness gage shall be obtained by passing the measurement results of the radiation gage through a low-pass filter during the period when the radiation gage is stable. The method according to claim 1, further comprising adding a measurement result of the laser thickness gauge through a filter.
JP2002194746A 2002-07-03 2002-07-03 Metal plate thickness measurement method Active JP3940327B2 (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008071337A1 (en) * 2006-12-15 2008-06-19 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Method and device for thickness measurement
KR100856276B1 (en) 2007-05-15 2008-09-03 주식회사 포스코 Detecting device for thickness of rolled material
JP2010107213A (en) * 2008-10-28 2010-05-13 Jfe Steel Corp Device and method for measuring corrosion depth in metal plate
CN102022987A (en) * 2009-09-11 2011-04-20 株式会社东芝 Radiation thickness gauge
CN105371773A (en) * 2015-11-30 2016-03-02 广东长盈精密技术有限公司 Thickness measurement method

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104729415A (en) * 2015-03-26 2015-06-24 南京师范大学 High-precision super-high temperature real-time thickness measuring device and method

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008071337A1 (en) * 2006-12-15 2008-06-19 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Method and device for thickness measurement
JP2010512524A (en) * 2006-12-15 2010-04-22 フラウンホッファー−ゲゼルシャフト ツァ フェルダールング デァ アンゲヴァンテン フォアシュンク エー.ファオ Method and apparatus for thickness measurement
US8064072B2 (en) 2006-12-15 2011-11-22 Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E.V. Method and apparatus for thickness measurement
US8228488B2 (en) 2006-12-15 2012-07-24 Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E.V. Method and apparatus for thickness measurement
KR100856276B1 (en) 2007-05-15 2008-09-03 주식회사 포스코 Detecting device for thickness of rolled material
JP2010107213A (en) * 2008-10-28 2010-05-13 Jfe Steel Corp Device and method for measuring corrosion depth in metal plate
CN102022987A (en) * 2009-09-11 2011-04-20 株式会社东芝 Radiation thickness gauge
CN105371773A (en) * 2015-11-30 2016-03-02 广东长盈精密技术有限公司 Thickness measurement method

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