JPH07236954A - Powder shortage detecting method of inside of mold inlet and device therefor - Google Patents

Abstract

PURPOSE:To eliminate influence of operational condition, external disturbance state, etc., by detecting a time depending change rate of the image signal photographing the inside of mold inlet so as to detect occurrence of powder shortage. CONSTITUTION:The image signal from ITV camera is inputted in a spatial average value arithmetic unit 5 through A/D conversion device 3 and pre- processing unit 4. An average luminance value of the spatial average value arithmetic unit 5 is averaged in the lapse of time by a elapsing averaging processing unit 6. A time delayed type recording device 7 stores an averaged luminance, a difference relative to an average luminance at present time is calculated by a difference arithmetic unit 8, the influence of change of operating condition, etc., is removed. When powder shortage occurs, a difference luminance value shows abrupt change, a comparing arithmetic unit 9 detects abrupt change, it is informed to an alarm raising device 10, and then, the alarm is sent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for detecting a powder shortage in a mold mouth for detecting the occurrence of powder shortage based on a video signal obtained by imaging the inside of the mold mouth.

[0002]

2. Description of the Related Art In a continuous casting machine, a granular or powdery powder is used to prevent the oxidation of molten steel by blocking the molten steel from the outside air and to lubricate between the mold and the slab. Added to the surface. Conventionally, for the supply of powder, an operator on the machine side visually judges the consumption amount of powder,
Appropriate amount of powder was added appropriately. However, on the machine side, the working environment is poor due to high temperature and high humidity, dust, etc., which is not a preferable working environment for human beings.In addition, the worker should detect powder shortage and put in powder in parallel with other work. It had to be done and the working conditions were even more severe.

On the other hand, when the detection of the powder shortage is delayed, not only the quality of the product is adversely affected, but also in the operation,
There is a high risk of causing a breakout leading to a serious accident, and it is highly necessary to accurately detect and inject powder. Therefore, methods and devices for automatically loading a fixed amount of powder in a fixed cycle have been developed to reduce the burden on the operator as much as possible. Since the casting situation is monitored and it is decided by the judgment based on the monitoring result, the worker had to continue the visual monitoring inside the mold mouth under the bad environment.

Therefore, recently, as a method of monitoring the inside of the mold mouth by a machine rather than by a human, for example, a temperature distribution measurement inside the mold mouth by a radiation thermometer (Japanese Patent Laid-Open No. 3-248752) and an infrared camera are used. A method has been proposed in which a powder shortage is detected by temperature distribution measurement, remote monitoring of the mold mouth by an ITV camera, and the like, and the powder is appropriately charged.

[0005]

However, the above-mentioned method has a problem in that erroneous detection occurs due to powder combustion flame, molten steel scattering, change in operating conditions, etc., and reliable powder shortage cannot be detected. It was By the way, as an apparatus for removing the effects of such powder combustion flames and molten steel scattering, for example, there is an apparatus described in JP-A-61-132250 as a apparatus for detecting a molten steel level. However, although the publication discloses a technique for removing the influence of powder combustion flame, molten steel scattering, etc. in the molten steel level detection, there is no suggestion of detection of powder shortage on the molten steel surface. Even if this technology is applied to powder shortage detection, sufficient detection capability will not be obtained when level fluctuations occur on the molten steel surface, and the effects of external disturbances such as changes in operating conditions can be effectively eliminated. I can't. From this, the influence of disturbances such as powder combustion flame, molten steel scattering or changes in operating conditions is eliminated,
There was a demand for the development of a highly reliable powder shortage detection technology.

The present invention has been made to solve the above problems, and eliminates the influence of external disturbances such as powder combustion flame, molten steel scattering or changes in operating conditions, and highly reliable detection of powder shortage in the mold mouth. The aim is to obtain a method and its device.

[0007]

A method for detecting powder shortage in a mold mouth according to the present invention includes a step of detecting a time change rate of a video signal, and a powder shortage occurrence based on the detected time change rate of the video signal. And a step of detecting.

The image pickup means for picking up the image inside the mold mouth, the A / D conversion means for changing the video signal output from the image pickup means into a digital signal, and the digital signal output from the A / D conversion means Spatial average value calculating means for calculating a spatial average brightness value from a brightness signal, temporal averaging processing means for averaging the spatial average brightness values calculated by the spatial average value calculating means with time, and the spatial average Difference calculating means for calculating a difference value between the spatial average luminance value at the current time calculated by the value calculating means and the temporal average luminance value at the previous time before the current time, and the difference calculated by the difference calculating means It is provided with a comparison operation means for detecting a powder shortage by comparing the value with a preset powder shortage detection set value.

[0009]

In the method for detecting powder insufficiency in the mold according to the present invention, by obtaining the time change rate of the video signal,
It is possible to detect only the change in the amount of radiant light from the surface of the molten steel that has passed through the powder layer, excluding the effects of operating conditions and disturbance conditions.

In the mold mouth powder shortage detection device according to the present invention, the ITV camera takes an image of the inside of the mold mouth and outputs the image signal inside the mold mouth to the A / D conversion means. A
The / D conversion means converts the image signal inside the mold mouth into a digital signal, and the spatial average value calculation means calculates a spatial average luminance value from the luminance signal of the digital signal.
The temporal averaging processing means averages the spatial average luminance values calculated by the spatial average value computing means over time, and the difference computing means calculates the spatial average luminance value at the current time calculated by the spatial average value computing means and the current time. The difference value with the temporal average luminance value at the previous time before is calculated. The comparison calculation means detects the powder shortage by comparing the difference value calculated by the difference calculation means with a preset powder shortage detection setting value.

[0011]

EXAMPLES Before explaining specific examples, the principle of the present invention will be described. Imaging the inside of the mold mouth I
The video signal I from the TV camera is expressed as shown in the following expression (1).

[0012]

[Equation 1]

However, the subscript i is an item relating to operating conditions such as the type of powder, x and y are measurement positions in an image obtained from an ITV camera, t is time, and each element has the following contents. ing. epsilon: quantity radiation efficiency f _i from the mold mouth: Radiation amount from the transmitted molten steel surface powder layer g _i: Radiation amount h _i from the casting nozzle face: light amount k _i from the flame caused by powder burning: template mouth Amount of disturbance light from other than the above, each of the above elements has different characteristics as shown below. ε: Constant or gently changing over a very long time. f _i: powder is substantially zero in Takashimitsu normal state, abruptly increases as the powder shortage occurs. g _i : constant or changes slowly over a long period of time. h _i : It changes instantaneously, but the time average value at a fixed position becomes 0. k _i : constant

[0014]

[Equation 2]

[0015]

[Equation 3]

Here, if the change amount D of the video signal is defined as a difference value of the video signal every moment, the change amount D of the video signal can be expressed by the following equation (4).

[0017]

[Equation 4]

As can be seen from the equation (4), the change amount D of the video signal is represented only by the amount of radiated light from the surface of the molten steel which has passed through the powder layer. Therefore, by obtaining the amount of change D of the video signal, the amount of radiant light from the molten steel surface that has passed through the powder layer is eliminated by excluding the amount of light h _i from the flame generated by powder combustion and the amount of disturbance light k _i from outside the mold mouth. Only changes can be detected. Further, f _i in the equation (4) exhibits a behavior as shown in the following equation (5) when the powder is densely present. f _i (x, y, t) = ay (x, y, t) (5) where a is a constant and y () is a linear function. On the other hand, when a powder shortage occurs, as shown in the following equation (6). Behaves differently. f _i (x, y, t) = by ⁿ (x, y, t) (6) where b is a constant

Therefore, the change amount D of the video signal in each case is approximately expressed by the following equation. Δf _i (x, y, t) = a (7) Δf _i (x, y, t) = nby ^n-1 (x, y, t) (8) However, Δf _i is f _i every moment Therefore, (8)
As can be seen from the equation, the amount of change D of the video signal due to the powder shortage is expressed as a (n-1) th power function with respect to y (x, y, t), and therefore the amount of radiation from the molten steel surface that has passed through the powder layer. Can be detected very sensitively, and it becomes possible to accurately judge the powder shortage situation. Also,
Even when the expression (8) is substituted for the expression (4), the variation amount of ε can be ignored.

Next, specific examples will be described.
FIG. 1 is a functional block diagram showing an embodiment of the present invention. In the figure, 1 is an ITV camera for imaging the inside of a mold mouth, and 2 is a signal processing device for inputting a video signal from the ITV camera 1. Reference numeral 3 is an A / D conversion device for converting an analog video signal into a digital signal, 4 is a pre-processing device for arranging the digital signal input from the A / D conversion device 3 so as to be suitable for subsequent processing, and 5 is an entire screen or A spatial average value computing device for calculating a spatial average luminance value from the luminance signal component of the video signal in a certain region, and 6 is a temporal averaging for calculating a temporal average value from the spatial average luminance value of the video signal at the current time. The processing device 7 is a delay type recording device for temporarily storing the temporal average luminance value calculated by the temporal averaging processing device 6. 8 is a difference calculation device for calculating the difference between the temporal average brightness value at the previous time recorded in the delay type recording device 7 and the spatial average brightness value at the current time output from the spatial average value calculation device 5, and 9 is a calculation A comparison calculation device 10 for comparing the difference value calculated by the device 8 with a preset powder shortage detection set value is an alarm generation device for generating an alarm signal indicating the powder shortage based on the result of the comparison calculation device 9. is there.

Next, the operation of the embodiment configured as described above will be described. The video signal from the ITV camera 1 is A / D
The signal is converted into a digital signal by the conversion device 3 and input to the preprocessing device 4, and the signals are organized by the preprocessing device 4 and input to the spatial average value calculation device 5. The spatial average value calculator 5 calculates the spatial average luminance value of the video signal in the entire screen or in a fixed area. FIG. 2 is a diagram showing a relationship between the spatial average luminance value output from the spatial average value computing device 5 and time in an ideal state where there is almost no disturbance.
As shown in FIG. 2, in the ideal state, the luminance value in the normal state (the state where the powder is dense, that is, the state of a in FIG. 2) is almost constant, and therefore, the luminance value is more than this value based on the luminance value. The powder shortage detection set value may be set to a high level.

However, in practice, operating conditions (powder type, product quality standard, etc.), disturbance conditions (lighting in the factory, etc.)
, The brightness value in the normal state is not constant, and the brightness value output from the spatial average value calculation device 5 is a value in which a bias component rising to the right is superimposed as shown in FIG. By comparing with the preset powder shortage detection setting value, erroneous detection may occur by detecting the brightness value in the normal state (FIG. 3).
reference). Therefore, it is necessary for the worker to grasp the situation such as the operating condition and change the powder shortage detection setting value to suit the situation, but it is difficult to appropriately perform such work.

Therefore, in the present embodiment, the luminance values of the spatial average value computing device 5 are averaged over time by the temporal averaging processing device 6 and stored in the delay type recording device 7. Then, by calculating the difference between the temporal average luminance value at the previous time and the spatial average luminance value at the current time stored in the delay type recording device 7 by the difference calculating device 8, the powder shortage is detected by the above-described principle. Eliminate the effects of fluctuations in operating conditions, etc. FIG. 4 is a diagram showing the relationship between the difference brightness value calculated by the above-described arithmetic device 8 and time. As shown in FIG. 4, even when the operating condition or the disturbance condition changes, the difference luminance value in the normal state (the state of a in FIG. 4) is almost constant, while when the powder shortage occurs, The difference luminance value shows a sharp change. Therefore, by performing the powder shortage detection based on the difference luminance value, it is possible to eliminate the influence of the fluctuation of the operating conditions and the like. In the comparison calculation device 9, the preset powder shortage detection setting value (broken line in FIG. 4) is compared with the difference brightness value calculated by the calculation device 8,
When the calculated difference brightness value exceeds the powder shortage detection setting value, the alarm generation device 10 is notified of that fact. The alarm generation device 10 that has received this notification issues an alarm to, for example, a powder insertion robot or the like (not shown).

Further, as can be seen from FIG. 4, when the powder is normally put into the mold, the polarity of the differential luminance value switches from positive to negative. Therefore, by paying attention to this change, the powder can be properly put into the mold. The input time can be accurately detected. Therefore, for example, it is possible to know the powder loading time without inputting a powder loading signal from an external device such as a powder loading robot, and it is possible to construct an extremely inexpensive and reliable powder shortage detection system. .

[0025]

As described above, according to the present invention, the time change rate of the video signal is obtained, and the powder shortage is detected based on the time change rate. Therefore, the influence of the operating condition, the disturbance situation, etc. is eliminated. , It becomes possible to detect the lack of powder with high accuracy by only changing the amount of radiation light from the surface of the molten steel that has passed through the powder layer.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a luminance value and time in an ideal state where there is almost no disturbance.

FIG. 3 is a diagram showing a relationship between a luminance value and time when there is a disturbance.

FIG. 4 is a diagram showing a relationship between a difference luminance value and time according to the present invention.

[Explanation of symbols]

 1 ITV camera 2 signal processing device 3 A / D conversion device 4 pre-processing device 5 spatial average value calculation device 6 temporal averaging processing device 7 delay type recording device 8 difference calculation device 9 comparison calculation device 10 alarm generation device

Claims (2)

[Claims] 1. A powder shortage in a mold mouth comprising: a step of detecting a time change rate of a video signal; and a step of detecting occurrence of powder shortage based on the detected time change rate of a video signal. Detection method. 2. An image pickup means for picking up an image of the inside of the mold mouth, an A / D conversion means for converting a video signal outputted from the image pickup means into a digital signal, and a digital signal outputted from the A / D conversion means. A spatial average value calculating means for calculating a spatial average brightness value from a brightness signal; a temporal averaging processing means for averaging the spatial average brightness values calculated by the spatial average value calculating means over time; Difference calculation means for calculating a difference value between the spatial average brightness value at the current time calculated by the value calculation means and the temporal average brightness value at the previous time before the current time; and the difference calculated by the difference calculation means A powder mouth shortage detection device in a mold mouth, comprising: a comparison calculation unit that detects a powder shortage by comparing a value with a preset powder shortage detection set value.