JPS61231403A - Apparatus for detecting position of edge part of steel plate strip running through furnace - Google Patents

Abstract

PURPOSE:To make it possible to detect the position of an edge part, by attenuating the wavelength of light generated from a steel plate by a filter and passing only the sensitivity region of the image pick-up element of an industrial television and the wavelength of illumination light coinciding with said sensitivity region. CONSTITUTION:A filter 8 attenuating light emitted from a steel plate 4 and permitting only the passage of the wavelength of an illumination light source (halogen lamp) and that of the region coinciding with the element sensitivity of the image pick-up tube of an industrial television 3 is attached to the front surface of the industrial television 3 to avoid the lowering in voltage change in a video signal wave form. When the steel plate 4 is heated in a furnace and a wavelength approaches a visible region from an infrared region, the visible light region of the light from the halogen lamp is passed but the heat radiation light from the surface of the steel plate 4 is perfectly cut and, therefore, the lowering in contrast is suppressed. Therefore, as the contrast of the surface of the steel plate and that of a reflective plate becomes stronger, the value of voltage difference becomes large and the signal proportional to the positional change of an edge part is formed on the basis of the change in voltage and set as a control signal for correcting a position.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a device for detecting the edges of a steel plate slit running in a high-temperature furnace such as an annealing furnace.

Conventional technology Conventionally, when a steel strip runs through an annealing furnace, etc., the strip may meander and come into contact with the furnace wall, causing damage, which is dangerous. Edge of the running strip (hereinafter referred to as the edge)
The current method is to stably detect and control the position.

The publication of Japanese Patent Publication No. Sho 51-36415, ``Ear end position control device using television,'' shown in FIG. 10, is an example of such a conventional technique.

To explain this simply, when l is a traveling steel strip in the furnace and travels in the y direction as shown by the arrow, it moves in the x direction, that is, it meanders. Therefore, the edge of the steel plate was imaged by an industrial television camera 2, and the output signal, that is, a video signal, was converted by a video signal to control signal converter 3 into a control signal proportional to the displacement of the steel plate in the X direction. Thereafter, this is converted into a hydraulic control signal by the electro-hydraulic converter 4, and this signal controls the hydraulic cylinder 5, drives the guide roll mechanism 6, and corrects the center position of the steel plate.

Problems to be Solved by the Invention However, in such an edge end position detection means, a reflector made of stainless steel or the like is placed on the rear surface of the steel plate, and a halogen lamp is used to shine light on the reflector to collect the reflected light. A contrast is created with the light area and the steel plate as the dark area, and the movement of the boundary line is detected as the positional displacement of the edge, so when the temperature inside the furnace rises, the steel plate emits light due to heat. Therefore, there was a drawback (problem) that the contrast deteriorated and detection of the edge end position of the steel plate became unstable.

The present invention eliminates the above-mentioned drawbacks of the conventional technology, takes measures to prevent the contrast of the detection part from decreasing due to light emission from the steel strip as the furnace temperature rises, and constantly and stably detects the position of the edge end. The object of the present invention is to provide a device for detecting a strip edge end of a steel plate running in a furnace.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides an optimal sensitivity characteristic area of the image pickup tube on the front side of the image pickup tube of an industrial television that detects the edge of the steel plate running in the furnace. It is equipped with a filter that allows only wavelengths to pass through.

Hereinafter, the configuration of the present invention will be explained with reference to the drawings. FIG. 1 is a cross section of the ear end position detection section of the present invention. 1 indicates the entire high-temperature furnace such as an annealing furnace, and 2 indicates the ceiling portion 1a of the furnace.
A glass window 3 indicates two industrial television cameras installed to detect the meandering of the steel strip 4 running inside the furnace through the glass window.

Reference numeral 5 denotes a glass window provided in the wall 1b of the furnace, through which a rear reflector plate 7 inside the furnace is illuminated by an illumination light source 6 using a halogen lamp. This rear reflector plate 7 is a traveling steel plate strip 4
This is a reflective plate made of stainless steel or other material installed on the rear surface of the vehicle.

In such a configuration, the image and video signal waveforms displayed on the two industrial televisions are as shown in FIGS. 2 to 5. In these, (a) is the left TV, (b)
) shall indicate the video or video signal waveform of television.

In this case, the reflected light from the rear reflector 7 is blocked at the center by the steel plate strip, so the steel plate appears dark and the reflectors on both sides appear bright, and the waveform of the video signal at that time is as shown in Figure 3. 4a and 4b, which are the edge end positions of the steel plate.
Position 4'a corresponding to .

A voltage change occurs at 4'b. When the temperature inside the furnace was 600° C. or lower, the voltage waveform E of this video signal was approximately 400 mV. In the present invention, the signal processing device generates a signal proportional to the change in the ear end position using this voltage change E, and this signal is used as a control signal for position correction.

That is, if the vertical axis is the threshold level voltage V1, and the horizontal axis is the time axis, then the voltage change 4'a at the tip end.

It is possible to obtain the detection signal of the edge of the ear at the threshold level voltage V determined in 4'b. In this case, the value of the voltage difference E of the video signal waveform is It is proportional to the difference in surface brightness of the steel plate 4 when viewed from the position.

In other words, the stronger the contrast between the steel plate surface and the reflector surface, the
The value of the voltage difference E is large, and stable signal processing can be performed when the signal is binarized using the threshold level voltage V.

However, as shown in FIG. 4, when the temperature inside the furnace reaches a high temperature, particularly 600° C. or higher, the steel plate is heated by the furnace temperature and begins to emit radiant light.

Therefore, the waveform of the video signal according to Industrial Television 3.31 becomes the waveform shown in FIG. 4, and the contrast between the reflected light from the steel plate surface and the reflector plate surface at the edge of the steel plate sharply decreases. The voltage difference E is 40mV
It decreases to 11 degrees. This means that when the video signal at the edge of the steel plate is binarized using the threshold level voltage V, the width of the threshold level voltage setting becomes very narrow, making the signal processing unstable, and the accurate measurement of the edge of the steel plate. This results in the aforementioned disadvantage of not being able to perform detection.

Generally, the spectral radiance of a perfect radiator increases as the temperature rises, as shown in FIG. 8, and at the same time, the spectral radiance extends from infrared to ultraviolet. As the temperature inside the furnace rises and the temperature on the surface of the steel plate becomes high, the surface of the steel plate gradually radiates heat at shorter wavelengths, and when it reaches the same wavelength range as the wavelength of the halogen lamp, light is reflected from the steel plate 4. It becomes difficult to distinguish the reflected light from the reflector 7, and the image of the industrial television camera loses contrast, making detection of the edge of the steel plate unstable as described above.

On the other hand, as shown in Figure 6, the sensitivity of the image sensor of industrial television is almost in the visible light range (wavelength 300 to 700 nm).
m), the spectral energy distribution of the halogen lamp is widely distributed from the ultraviolet to the infrared region including visible light, although the maximum value is slightly biased toward the infrared region, as shown in Figure 7. ing.

Therefore, as a practical matter, it can be seen that in industrial televisions, the edge end of a steel plate strip is detected using wavelengths in the visible light region (400 to 700 nm).

Therefore, in the present invention, in front of the industrial television 3, the radiation light emitted from the steel plate is attenuated, and the wavelength of the illumination light source (halogen lamp etc.)
By installing a filter 8 that passes only wavelengths in a region matching the element sensitivity of the image pickup tube, a decrease in the voltage change E in the video signal waveform is avoided.

FIG. 9 shows the spectral characteristics of the filter 8 attached to the front of the industrial television 3 in FIG.
It has the characteristic of allowing light of wavelengths from 0 to 700 r+m) to pass through, and making it difficult for light of other wavelengths to pass through.

When the steel plate is heated in a furnace, its surface temperature gradually rises, and the wavelength approaches the visible region from the infrared region.
Even if all wavelengths longer than 700 nm are cut, the light from the halogen lamp can still pass through the visible light range, but the thermal radiation from the surface of the steel plate is completely cut out, so a decrease in contrast can be suppressed.

FIG. 5 shows a video signal waveform when the filter according to the present invention is installed, and the signal level difference at the edge of the steel plate is 300.
It was possible to obtain stable contrast almost unaffected by mV and furnace temperature.

As described in detail, the present invention aims to prevent the contrast between the steel plate running in the furnace and the rear reflector plate from decreasing due to the generation of light due to the temperature inside the furnace. Taking advantage of this difference, we used a filter to attenuate the wavelength of the light emitted from the steel plate, allowing only the wavelength of the illumination light that matches the sensitivity range of the image sensor of an industrial television to pass through. By installing a steel plate edge detection device using an industrial television camera equipped with the above filter in a place where the temperature changes, the position of the steel plate edge edge can be automatically and stably detected while monitoring the inside of the furnace. In addition, it has the effect of allowing the steel plate to travel safely without coming into contact with the furnace wall.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the ear end position detection unit of the present invention, FIG. 2 is a diagram showing a video screen of an industrial television, and FIGS.
The figure is a video signal waveform diagram of an industrial television. Figure 6 is a diagram showing the sensitivity characteristics of an image sensor for an industrial television, Figure 7 is a spectral energy distribution diagram of a halogen lamp, Figure 8 is a spectral radiance diagram of a perfect radiator, and Figure 9 is a diagram of the spectral radiance of a perfect radiator. A filter spectral characteristic diagram, FIG. 10, is an explanatory diagram of the prior art. l...Halogen lamp 3...Industrial television camera 4...Steel plate 7...Rear reflector 8...Filter Figure 6 Wave 4 (4I#F+) Figure 7 Figure 8 Figure 9 figure

Claims (1)

[Claims] (1) A device for detecting the edge end position of an in-furnace steel sheet strip that travels while partially blocking light from a rear reflector illuminated by a halogen lamp, wherein the edge end position is detected by an industrial television camera. is imaged, and the displacement of the ear end position is detected by the difference in contrast between the ear end and the rear reflector using video signals from the image pickup tube. This is then converted into a control signal to control the position of the steel plate. 1. A device for detecting the edge end position of a steel strip running in a furnace, characterized in that a filter is provided on the front surface of the image pickup tube to allow only wavelengths in an optimum sensitivity characteristic region of the image pickup tube to pass through.