Coating weight control apparatus and coating weight control method
An apparatus for controlling coating weight coated on a strip by using an air knife disposed in a travelling direction of the strip in a continuous plating process in which the strip is dipped in a molten metal pot and is coated includes: a prediction model unit including a prediction model in which a neural network is trained with accumulated operation conditions; and an optimum air knife condition calculation unit configured to derive an absolute value of at least one of an air knife gap and an air knife pressure by using the prediction model based on an input operation condition.
1. An apparatus for controlling coating weight coated on a steel strip by using an air knife disposed in a travelling direction of the steel strip in a continuous plating process in which the steel strip is dipped in a molten metal pot and is coated, the apparatus comprising:
a prediction model unit including a coating weight prediction model in which a neural network is trained with accumulated operation conditions; and
an optimum air knife condition calculation unit configured to derive an absolute value of at least one of an air knife gap and an air knife pressure by using the coating weight prediction model based on an input operation condition,
wherein the accumulated operation conditions and the input operation condition comprise: a line speed of the steel strip; an air knife gap; and an air knife pressure,
wherein the optimum air knife condition calculation unit includes:
an air knife gap derivation unit which derives an air knife gap based on the input operation condition by using the coating weight prediction model; and
an air knife pressure derivation unit which derives an air knife pressure based on the input operation condition and the derived air knife gap by using the coating weight prediction model,
wherein the air knife gap derivation unit derives a first air knife gap for one surface of the steel strip based on the input operation condition, and derives a second air knife gap for the other surface of the steel strip based on the input operation condition, and
wherein the air knife pressure derivation unit includes a first prediction model for one surface of the steel strip and a second prediction model for the other surface of the steel strip, derives a first air knife pressure for the one surface of the steel strip by applying at least the input operation condition and the first air knife gap to the first prediction model, and derives a second air knife pressure for the other surface of the steel strip by applying at least the input operation condition and the second air knife gap to the second prediction model.
2. The apparatus of claim 1 , wherein:
the air knife pressure derivation unit
compares the first air knife pressure and the second air knife pressure, and
outputs each of the first air knife pressure and the second air knife pressure when a difference between the first air knife pressure and the second air knife pressure is smaller than a predetermined threshold value.
3. The apparatus of claim 2 , wherein:
when the difference between the first air knife pressure and the second air knife pressure is larger than the predetermined threshold value, the air knife pressure derivation unit derives a corrected first air knife pressure and a corrected second air knife pressure by adjusting the first air knife pressure and the second air knife pressure.
4. The apparatus of claim 1 , wherein:
the air knife pressure derivation unit
performs an operation of deriving a corrected first air knife pressure and a corrected second air knife pressure by adjusting a difference between the first air knife pressure and the second air knife pressure to be equal to or smaller than a predetermined threshold value, and
the optimum air knife condition calculation unit
further includes an air knife gap correction unit which derives a corrected air knife gap for each of the one surface and the other surface of the steel strip based on the corrected first and second air knife pressures by using the coating weight prediction model.
5. The apparatus of claim 1 , wherein:
the air knife pressure derivation unit
derives an average of the first air knife pressure and the second air knife pressure as an optimum air knife pressure, and
the optimum air knife condition calculation unit
further includes an air knife gap correction unit which derives an air knife gap for each of the one surface and the other surface of the steel strip based on the optimum air knife pressure.
6. The apparatus of claim 1 , wherein:
a coating weight of the steel strip is measured, and the coating weight prediction model is corrected if a difference between the coating weight measurement value and a coating weight prediction value predicted by using the coating weight prediction model is determined.
7. The apparatus of claim 6 , wherein:
after the steel strip moves by a predetermined distance, a prediction value of the coating weight prediction model or a target coating weight input to the coating weight prediction model are corrected if a difference between the coating weight measurement value and the coating weight prediction value is determined.
8. The apparatus of claim 7 , further comprising:
a memory array which stores each of the coating weight prediction value or the target coating weight and the coating weight measurement value in a corresponding cell while the steel strip moves by the predetermined distance.
9. The apparatus of claim 1 , wherein:
the coating weight prediction model is a model which uses the input operation condition as an input and predicts and outputs a coating weight.
10. The apparatus of claim 1 , wherein:
the air knife gap derivation unit derives the derived air knife gap by using a look-up table.
11. The apparatus of claim 1 , wherein:
coating weight of the steel strip is measured, and the coating weight prediction model is corrected if a difference between the coating weight measurement value and a target coating weight included in the input operation condition is determined.
12. The apparatus of claim 11 , wherein:
after the steel strip moves by a predetermined distance, a prediction value of the coating weight prediction model or the target coating weight input to the coating weight prediction model are corrected if a difference between the coating weight measurement value and the target coating weight is determined.
13. The apparatus of claim 1 , wherein:
the accumulated operation conditions and the input operation condition further comprise: an air knife height; air knife angle; and at least one of a kind of the steel strip, a thickness of the steel strip, a width of the steel strip, a vibration of the steel strip, and a tension of the steel strip.