JP7168444B2 - Plating deposition control device and control method - Google Patents

Description

The present invention relates to a coating weight control device and a control method for depositing a desired thickness of coating on a steel plate in a continuous plating line of a steel plant, and performs control in consideration of the coating weight assurance standards that differ for each steel plate. Thus, the present invention relates to a plating deposition amount control apparatus and a control method that realize the production of high-quality plated steel sheets and the saving of the raw material unit consumption.

Coating weight control involves immersing a steel sheet that is continuously sent in a bath of a hot-dip coating bath, allowing the hot-dip coating bath to adhere to the steel sheet, and after lifting it out of the bath, the front and back nozzles installed on the front and back of the steel sheet. It is a control to deposit a desired thickness of the hot dipping bath on the steel plate by blowing gas on the steel plate from the nozzle to remove the hot dipping bath that has adhered excessively.

There are upper and lower limit values for the thickness of the coating applied to steel sheets, which are required by end users. Due to the diversification of end-user demands in recent years, the guarantee rules for the upper and lower limits of the coating weight have also diversified. There are steel sheets for which upper and lower limits are stipulated in , and steel sheets for which each part in the width direction of the steel sheet must satisfy the upper and lower limits. On the other hand, in order to improve the yield of the plating raw material, it is desirable to avoid depositing more than necessary coating on the steel sheet. is set as the target value of the coating weight, and the actual coating weight is controlled so as to match the target value.

As a conventional method for controlling the coating amount in consideration of preventing the lower limit cracking of the coating, in Patent Document 1, the current steel sheet being processed is switched to the next steel sheet to be processed next time, and the target coating amount is set. When the value is changed, an intermediate coating weight target value is calculated in consideration of the lower limit of the next steel plate, and through this target value, the coating weight target value of the current steel plate is changed to the coating weight of the next steel plate. An example is shown in which the target value of the coating amount is switched while preventing the lower limit cracking by shifting to the target value.

In addition, in Patent Document 2, a special management material that deposits a thick zinc adhesion amount of about 10 to 20 [g/m ² ] for specific users and a general zinc adhesion amount lower limit value with priority on reducing the zinc unit consumption A method of saving plating raw materials while preventing quality deterioration by performing control that distinguishes materials is shown.

JP-A-2001-59150 JP-A-7-180020

However, what is considered in the method of Patent Document 1 is that when the target value of the coating weight is changed, the lower limit of the sum of the coating weights on the front and back surfaces is controlled so as not to fall below this. , there was no consideration for the various guarantee regulations of the lower limit of the plating amount. For example, upper and lower limits are specified for each front and back of the next steel sheet, and if the coating weight on the front side of the current steel sheet is a certain amount less than on the back side, calculate an intermediate coating weight target value in consideration of this point. Therefore, there was a problem that the risk of cracking at the lower limit of the coating amount on the surface of the next steel sheet increased.

Similarly, even in the method of Patent Document 2, consideration is not given to various guarantee rules for the lower limit of the plating amount, and cracking of the lower limit in general materials aiming at the lower limit and unnecessary plating adhesion in special management materials There is a possibility that the yield of the plating raw material may be lowered.

Therefore, the problem to be solved by the present invention is to improve the quality of the coating amount and to save the plating raw material by performing control in consideration of various quality standards that differ for each steel sheet. It is in.

In order to solve the above-described problems, in the plating deposition amount control apparatus of the present invention, the continuously sent steel sheet is immersed in a hot dipping bath bath, the hot dipping bath is attached to the steel plate, and the hot dipping bath is lifted out of the bath. Later, gas is blown onto the steel sheet from front nozzles and back nozzles provided on the front and back sides of the steel sheet to remove the excessively adhered hot dipping bath, and the plating plant is controlled to adhere the hot dipping bath to a desired thickness on the steel sheet. In the coating weight control device, the coating weight prediction model that describes the relationship between the plate speed, nozzle pressure, distance between the nozzle and the steel plate, and the coating weight that adheres to the steel plate, the current steel plate that is currently being plated, and the welding point and a preset control unit that calculates the nozzle pressure and nozzle position for depositing the desired plating on the next steel sheet to be plated next to the current steel sheet by calculation using the plating amount prediction model, The preset control unit includes a preset coating amount estimating unit that estimates the plating coating amount of the steel sheet obtained as a result of the preset control, and a first warranty standard determination unit that determines which of the multiple warranty standards of the next steel sheet. Then, from the estimated coating amount and the guaranteed standard of the steel sheet, as a result of the preset control, the occurrence of the non-standard risk that the next steel sheet is out of the guaranteed standard is determined, and the non-standard risk value is calculated. A risk calculation unit, a target adhesion amount correction unit that corrects the target plating adhesion amount of the next steel sheet with the non-standard risk value output by the first non-standard risk calculation unit, and the corrected target adhesion amount as the desired adhesion amount , a first manipulated variable calculation unit that calculates at least one of a nozzle pressure command value and a nozzle position command value for realizing this by calculation using the plating amount prediction model, and the first non-standard risk calculation The department has a first margin table in which the first margin is stored in association with the guarantee standard and the coating weight, and the difference between the value determined as the guarantee standard of the steel sheet and the estimated coating weight is the It is characterized in that, when the value of the first margin extracted from the first margin table becomes equal to or less than the value of the first margin, it is determined that the next steel plate is at risk of being out of specification .

According to the present invention, when the control command for the next steel sheet is calculated by preset control, if there is a risk of non-conformance with respect to the guaranteed standard of the coating amount of the steel sheet, the coating amount is determined according to the magnitude of the risk of non-standard. Correct the target value of

For example, when the guaranteed standard is the lower limit specification, if there is a risk of cracking the lower limit of the coating weight in preset control, the target value of the coating weight is corrected in the thickness direction according to the magnitude of the risk of cracking the lower limit.

By such a treatment, it is possible to avoid deviation of the coating weight of the plating and improve the quality. The correction amount of the target coating amount and the correction amount of the coating amount deviation can be set to the minimum value considering the guarantee standard for each steel sheet, so it is not necessary to deposit more plating than necessary on the steel sheet in order to avoid deviation from the guarantee standard. do not have. As a result, it is possible to improve both the quality and the yield of the plating raw material.

It is an explanatory view showing a plating plant. This is the configuration of the instruction information table. This is the processing of the preset adhesion amount estimator. This is the configuration of the first margin table. This is the processing of the one-side guarantee calculation unit. This is the processing of the double-sided one-point guarantee calculation unit. This is the processing of the one-sided one-point guarantee calculation unit. This is processing of the thinnest point guarantee calculation unit. This is the processing of the target adhesion amount correction unit. This is the processing of the first manipulated variable calculation unit. This is the configuration of the second margin table. This is the processing of the one-side guarantee calculation unit. This is the processing of the double-sided one-point guarantee calculation unit. This is the processing of the one-sided one-point guarantee calculation unit. This is processing of the thinnest point guarantee calculation unit. This is the processing of the adhesion amount deviation correction unit. FIG. 4 is an explanatory diagram showing a preset control section of the present invention; FIG. 4 is an explanatory diagram showing a feedback control section of the present invention;

Both quality improvement and cost reduction can be achieved in the coating weight control described in the following examples.

FIG. 1 shows an embodiment of the invention. The plating deposition amount control device 100 controls a plating plant 150 to deposit plating of a desired thickness on a steel plate (strip) 151 .

First, the plating plant 150 will be explained. A pot (bathtub) 152 of a plating plant 150 stores a hot-dip plating bath, and steel plates 151 connected at welding points 156 are continuously sent. The steel plate 151 that is currently being plated is called the current steel plate (preceding material), and the steel plate 151 that is welded and connected to the current steel plate at welding points 156 is called the next steel plate (following material). Leading and trailing material are switched at weld point 156 . The steel plate 151 is supported by an in-bath roll 160 and controlled to a constant tension value predetermined for each steel plate between itself and a top roll 161 . As the weld point 156 is passed, the tension changes from that of the leading member to that of the trailing member.
The steel plate 151 is immersed in the hot-dip galvanizing bath, and after being pulled out, gas is blown from nozzles 153 consisting of a front nozzle and a back nozzle provided on the front and back of the steel plate 151 to remove excessive coating. , the amount of deposited plating is controlled to the desired value. The amount of plating adhered to the steel plate 151 is generally determined by the speed of the steel plate 151 (plate speed), the pressure of the gas blown from the nozzle 153, and the distance between the nozzle 153 and the steel plate 151. Considering the vibration of the steel plate 151, the pressure of the front nozzle and the pressure of the back nozzle are usually the same. The adhesion amount on the front and back can be set to the same value.
Further, by operating the bath rolls 160, the warpage of the steel sheet 151 in the width direction can be changed. When the steel sheet 151 warps, this causes the coating amount of the steel sheet 151 in the width direction to differ in the width direction. However, the position of the bath rolls 160 should be controlled so that the steel sheet 151 does not warp. can correct the phenomenon of different values.
The relationship between the amount of plating deposited on the steel plate 151, the plate speed, the nozzle pressure, and the nozzle gap (the distance between the nozzle and the steel plate) is represented by Equation 1, for example.

In this embodiment, Equation 1 is hereinafter referred to as a plating deposit prediction model. In addition to this, the model for predicting the coating amount may also consider the nozzle height, the temperature of the steel sheet, the temperature of the hot-dip coating bath, and the like. Welding point 156 usually corresponds to a switching point of the coating weight target value. The coating amount detector 155 is a device that measures the amount of coating that is actually attached, detects how much coating is attached to the steel sheet 151 on each of the front and back sides of the steel sheet 151, and outputs the detected amount. In this embodiment, assuming a general coating amount detector, the measurement values of three points in the width direction, left, center, and right, are output for each of the front and back sides of the steel plate 151 (a total of six points on the front and back sides). ), and a case in which the width-direction coating weight distribution (coating weight profile) is output for each of the front and back surfaces will be described as an example. As a way of naming the parts in the width direction, one side may be called the work side (or operator side) and the other side may be called the drive side. The coating amount detector 155 is attached at a distance of several tens to hundreds of meters from the nozzle 153, and usually moves the steel sheet in the width direction, performs averaging as necessary, and then outputs the value. . For this reason, it usually takes several tens of seconds to two minutes until the amount of deposited plating corresponding to P, V, and D of the nozzle position can be measured.

Next, the configuration of the plating deposition amount control device 100 will be shown. In this embodiment, the case of lower limit guarantee will be described below as an example of the guarantee standard of the steel sheet. The coating weight control device 100 receives from the host computer 140 instruction information for the next steel plate, including the steel plate number, steel type, thickness, width, target values for the coating weight, and the like. The pressure and position of the steel plate 151, the speed of the steel plate 151, and the actual results of the coating weight detected by the coating weight detector 155 are received. A preset control unit 101 that calculates a position command and a nozzle pressure and position command for the current steel sheet so that the actual coating weight detected by the coating coating weight detector 155 matches the target coating weight. A feedback control unit 121 is provided to calculate .

As shown in FIG. 17, a preset control unit 101 includes a preset coating amount estimating unit 102 that estimates the coating amount distribution of the next steel sheet after preset control from the distribution of the actual coating amount of the current steel sheet. A first guarantee standard determination unit 103 that determines the lower limit guarantee standard, a first guarantee standard determination unit 103 that calculates the non-standard risk of the coating amount processed for this steel sheet from the estimation result of the preset adhesion amount estimation unit 102 and the lower limit guarantee standard. A non-standard risk calculation unit 104, a target coating amount correction unit 110 that calculates a correction amount of the plating coating amount target value necessary to avoid non-standard using the calculated non-standard risk, and a plating coating amount prediction model 112 , a first manipulated variable calculation unit 111 is provided for calculating the pressure and position of the nozzle 153 so as to achieve the corrected target plating amount.
Furthermore, the preset controller 101 has a first margin table 109 that is used by the first nonstandard risk calculator 104 . 17, the first margin table 109 is connected to the outside of the first non-standard risk calculation unit 104, but the first margin table 109 is connected inside the first non-standard risk calculation unit 104. It is good also as a structure provided.
When calculating the nozzle pressure in the first manipulated variable calculation unit 111, after solving Equation 1 for ln(P), the corrected plating adhesion amount target value is input to W, and the nozzle gap and the plate are input to D and V. By inputting the actual value of the velocity and obtaining ln(P) and converting it to P, the manipulated variable of the nozzle pressure can be calculated. When the nozzle position is calculated by the first manipulated variable calculation unit 111, the same procedure can be used for calculation.
The first nonstandard risk calculator 104 is composed of a one-sided guarantee calculator 105 , a double-sided one-point guarantee calculator 106 , a one-sided one-point guarantee calculator 107 , and a thinnest point guarantee calculator 108 .

As shown in FIG. 18, a feedback control unit 121 includes an adhesion amount deviation calculation unit 122 that calculates the difference between the target value and the actual value of the plating adhesion amount, and a second guarantee standard determination unit that determines the lower limit guarantee standard of the current steel sheet. 123, a second non-standard risk calculating unit 124 for calculating the non-standard risk of the plating coating amount processed on this steel sheet from the output of the second guaranteed standard determining unit 123 and the lower limit standard, a coating amount deviation calculating unit An adhesion amount deviation correction unit 130 that corrects the adhesion amount deviation output by 122 according to the output of the second nonstandard risk calculation unit, and a nozzle 153 pressure and position that eliminates the corrected adhesion amount deviation. 2 operation amount calculation units 131 are provided.
Furthermore, the feedback control section 121 has a second margin table 129 that is used by the second nonstandard risk calculation section 124 . In FIG. 18, the second margin table 129 is connected to the outside of the second non-standard risk calculation unit 124, but the second margin table 129 is connected inside the second non-standard risk calculation unit 124. It is good also as a structure provided.
The second nonstandard risk calculator 124 is composed of a one-sided guarantee calculator 125 , a double-sided one-point guarantee calculator 126 , a one-sided one-point guarantee calculator 127 , and a thinnest point guarantee calculator 128 .

The function of each part will be described in detail below with reference to the drawings. FIG. 2 shows an example of instruction information received by the plating deposition amount control device 100 from the host computer 140. As shown in FIG. The instruction information 201 is composed of basic information such as the steel plate number of the next steel plate, steel type, steel plate thickness, steel plate length, etc., control target values, etc., and is sent before the steel plate is processed. In the example of the instruction information shown in FIG. 2, the steel plate number, thickness, width, attribute values such as lower limit guarantee standard, control command values such as target adhesion amount, upper limit adhesion amount, lower limit adhesion amount, etc., nozzle gap and in-bath roll position command values related to control operating points such as Here, at least one of the bath rolls is movable in the horizontal direction, and the position of the bath roll is the horizontal position of the movable roll or the vertical overlap amount of the two bath rolls. is the amount of intermesh.
Actually, in addition to this, there are cases where the chemical composition of the steel sheet, the delivery destination, information on the next process, etc. are included. In the example of Fig. 2, the target coating weight of the steel plate with steel plate number KYR19600110 is A [g/m ² ] per side, the lower limit guarantee standard is for one side, and the lower limit for one side is B [g/m ² ]. ing. In other words, with this steel sheet, the coating weight is controlled with the target of A [g/ ^{m 2} ] per side. It shows that

FIG. 3 shows the processing of the preset adhesion amount estimator 102. As shown in FIG. A preset coating amount estimation unit 102 estimates the coating amount distribution of the next steel sheet when preset control is performed based on the plating coating amount distribution of the current steel sheet, the target coating amount of the current steel sheet, and the target coating amount of the next steel sheet. In the actual plating process, there is a differential thickness plating in which different thicknesses are applied to the front surface and the back surface. In S3-1, the value of the coating weight of the current steel sheet is taken in. A set ξc of the adhesion amount distribution of the current steel sheet is represented by Equation (2).

A set ξc of the adhesion amount distributions of the steel plate is composed of three adhesion amount distributions ξc1, ξc2, and ξc3. ξc1 consists of the amount of adhesion at three points in the width direction on each of the front and back surfaces. Wt_ws is the adhesion amount on the left side of the front surface, Wt_cn is the adhesion amount at the center of the front surface, Wt_ds is the adhesion amount on the right side of the front surface, Wb_ws is the adhesion amount on the left side of the back surface, Wb_cn is the adhesion amount on the center of the back surface, and Wb_ds is the adhesion amount on the right side of the back surface. . In addition, ξc2 is the adhesion amount distribution in the width direction of the surface of the steel plate, and ξc3 is the adhesion amount distribution in the width direction of the back surface of the steel plate.

Next, in S3-2, the preset adhesion amount estimator 102 uses ξc to estimate the adhesion amount distribution of the next steel sheet. The adhesion amount distribution ξn can be estimated by Equation (3).

As an example, the case of Wt_ws_p will be described. (Wt_ws-Wave) is the variation from the average coating weight on the left side of the table of the current steel sheet, and is the ratio of the target coating weight between the current steel sheet and the next steel sheet (W*n/W*c). By multiplying by , it can be converted to a variation value corresponding to the target value of the next steel plate. By adding this value to the target adhesion amount W*n of the next steel sheet, the adhesion amount on the left side of the table when preset control is performed on the next steel sheet can be estimated. Similarly, as an example, the case of the adhesion amount distribution ξn2 in the width direction of the steel sheet surface will be described. (Wt_width(w)-Wave) is the variation from the average coating weight distribution of the plating coating weight distribution on the surface of the current steel sheet, and is the ratio of the target coating weights of the current steel sheet and the next steel sheet (W*n/W By multiplying by *c), it is possible to convert to a variation value corresponding to the target value of the next steel plate. By adding this value to the target adhesion amount W*n of the next steel sheet, the adhesion amount distribution in the width direction of the surface of the steel sheet can be estimated when preset control is performed on the next steel sheet.

In S3-2, according to Equation 3, similar calculations are performed for each portion of the steel plate and the adhesion amount distribution in the width direction, thereby estimating the adhesion amount distribution after the preset control. In S3-3, the one-sided adhesion amount is estimated by Equations (4) and (5).

That is, the estimated surface adhesion amount is obtained by averaging the left, center, and right side surfaces, and the back surface adhesion amount estimation value is obtained by averaging the left, center, and right side surfaces of the back surface. Next, in S3-4, the adhesion amount per point on both sides is estimated by Equations (6) to (8).

That is, the one-point deposit on both sides consists of three points on the left, center, and right sides of the steel sheet, and is obtained by averaging the deposit on the surface and the deposit on the back of each corresponding portion. In S3-5, the one-side one-point adhesion amount is estimated. The one-side one-point adhesion amount is a total of six points, Wt_ws_p, Wt_cn_p, Wt_ds_p, Wb_ws_p, Wb_cn_p, and Wb_ds_p, which are adhesion amounts at three points in the width direction for each of the front and back sides. In S3-6, the distribution of the adhesion amount in the sheet width direction is estimated. The plate width direction adhesion amount distribution on the front surface is expressed by ξn2 of Equation 3, and the plate width direction adhesion amount distribution on the back surface is expressed by Equation 3 by ξn3.

Next, the first guaranteed standard determination unit 103 determines which of the multiple guaranteed standards of the next steel sheet. In this embodiment, the guaranteed standard is the lower guaranteed value. The example of the instruction information 201 in FIG. 2 indicates that the lower limit guarantee standard is one-sided, and the one-sided lower limit is B [g/m ² ]. That is, with this steel sheet, if either the front surface or the back surface is below B [g/m ² ], the quality is poor.

Before explaining the first non-standard risk calculator 104, FIG. The first margin table 109 determines that if the adhesion amount estimated by the preset adhesion amount estimating unit 102 exceeds the lower limit value for each guaranteed standard and the target value of the plating adhesion amount, there is no risk of breaking the lower limit. The value of whether or not is stored as the margin. In FIG. 4, for example, when the adhesion amount target value is (B-20) [g/m ² ] or less with one-sided guarantee, if both the estimated adhesion amount on the front side and the back side are larger than the lower limit value than δW11, This indicates that it is judged that there is no lower limit cracking risk for this steel plate.

Next, processing of the first nonstandard risk calculation unit 104 will be described. FIG. 5 shows the processing of the one-sided guarantee calculation unit 105. As shown in FIG. First, in S5-1, the smaller value Wr_11 of the coating weight on the front and back surfaces estimated for the next steel sheet by Equation 9 is taken.

Next, in S5-2, using Wr_11, the single-side lower limit guaranteed value Wmin1 taken in from the instruction information 201, and the value δWj1 extracted from the corresponding stratification from the first margin table 109, according to Equations 10 and 11, Calculate the lower limit cracking risk Wr_12 (nonstandard risk value) of the adhesion amount.

When Wtemp is a negative value, Wr_11 is greater than the guaranteed lower limit plus a margin, indicating that there is no risk of breaking below the lower limit. That is, when Wr_12 is 0, there is no risk of cracking at the lower limit when the one-side guarantee is applied to this steel plate. On the other hand, when Wtemp is a positive value, it indicates that Wr_11 is smaller than the value obtained by adding a margin to the guaranteed lower limit value. That is, when Wr_12 is a positive value, it indicates that there is a risk of breaking the lower limit depending on the magnitude of the value.

FIG. 6 shows the processing of the double-sided one-point guarantee calculation unit 106. As shown in FIG. First, in S6-1, the smallest (thinest) value Wr_21 of the left, center, and right both-side single-point adhesion amounts estimated for the next steel sheet by Equation 12 is taken.

Next, in S6-2, using Wr_21, the double-sided one-point guaranteed value Wmin2 taken in from the instruction information 201, and the value δWj2 taken out from the corresponding stratification from the first margin table 109, according to Equations 13 and 14, Calculate the lower limit cracking risk Wr_22 (nonstandard risk value) of the adhesion amount.

When Wtemp is a negative value, Wr_21 is greater than the guaranteed lower limit plus a margin, indicating that there is no risk of breaking below the lower limit. That is, when Wr_22 is 0, there is no risk of lower limit cracking when the double-sided one-point guarantee is applied to this steel plate. On the other hand, when Wtemp is a positive value, it indicates that Wr_21 is smaller than the lower limit guaranteed value plus a margin. That is, when Wr_22 is a positive value, it indicates that there is a risk of breaking the lower limit depending on the magnitude of the value.

FIG. 7 shows the processing of the one-sided one-point guarantee calculation unit 107. As shown in FIG. First, in S7-1, the smallest (thinest) value Wr_31 among the left, center, and right one-point adhesion amounts on the front and back surfaces estimated for the next steel sheet by Equation 15 is taken.

Next, in S7-2, using Wr_31, the single-sided one-point guaranteed value Wmin3 taken from the instruction information 201, and the value δWj3 taken from the corresponding stratification from the first margin table 109, according to Equations 16 and 17, Calculate the lower limit cracking risk Wr_32 (nonstandard risk value) of the adhesion amount.

When Wtemp is a negative value, Wr_31 is greater than the guaranteed lower limit plus a margin, indicating that there is no risk of breaking below the lower limit. That is, when Wr_32 is 0, there is no risk of cracking at the lower limit when one-sided one-point guarantee is applied to this steel plate. On the other hand, when Wtemp is a positive value, it indicates that Wr_31 is smaller than the value obtained by adding a margin to the guaranteed lower limit value. That is, when Wr_32 is a positive value, it indicates that there is a risk of breaking the lower limit depending on the magnitude of the value.

FIG. 8 shows the processing of the thinnest point guarantee calculation unit 108. As shown in FIG. First, in S8-1, the smallest (thinest) value Wr_41 is obtained from each of the adhesion amount distributions on the front and back sides estimated for the next steel sheet by Equations 18 to 20.

Next, in step S8-2, using Wr_41, the minimum thinnest point value Wmin4 taken in from the instruction information 201, and the value δWj4 taken out from the corresponding stratification from the first margin table 109, the following equations 21 and 22 are used: , the lower limit cracking risk Wr_42 (non-standard risk value) of the adhesion amount is calculated.

When Wtemp is a negative value, Wr_41 is greater than the guaranteed lower limit plus a margin, indicating that there is no risk of breaking below the lower limit. That is, when Wr_42 is 0, there is no lower limit cracking risk when the thinnest point guarantee is applied to this steel sheet. On the other hand, when Wtemp is a positive value, it indicates that Wr_41 is smaller than the value obtained by adding a margin to the guaranteed lower limit value. That is, when Wr_42 is a positive value, it indicates that there is a risk of breaking the lower limit depending on the magnitude of the value.

Next, processing of the target adhesion amount correction unit 110 will be described. The target deposit correction unit 110 determines the guarantee standard of the next steel sheet, and corrects the target value of the plating deposit using the value of the lower limit cracking risk of the applicable standard that is taken in from the first nonstandard risk calculation unit 104 . FIG. 9 shows the processing of the target adhesion amount correction unit 110. As shown in FIG. First, in S9-1, the target coating weight is taken in from the instruction information 201 of the next steel sheet. Next, in S9-2, the lower limit guarantee standard of the next steel sheet is read from the instruction information 201, and the lower limit cracking risk value (non-standard risk value) of the item requiring guarantee is read according to the lower limit guarantee standard. In the example of FIG. 2, the lower limit guarantee standard of the steel plate is one side guarantee, and the guarantee lower limit value is B [g/m ² ]. Finally, in S9-3, the target coating amount is corrected by the lower limit cracking risk value to calculate the target coating amount used for control. Specifically, the target adhesion amount used for control is calculated by Equation (23).

On the other hand, depending on the steel plate, it may be guaranteed at one point on both sides or at the thinnest point. There are also steel sheets to which multiple guarantee standards are applied with different minimum guarantee values. For example, there are steel sheets that are guaranteed by a complicated combination of standards, such as guaranteeing the lower limit of one side with B [g/m ² ] and guaranteeing the lower limit of the thinnest point with E [g/m ² ] at the same time. For steel sheets to which multiple guarantee standards are applied with different lower guarantee values, for example, if one-sided guarantee and minimum thinnest point guarantee are applied, it is used for control as shown in Equation 24 Calculate the target adhesion amount.

As in the example shown in this formula 24, even for a steel sheet that is guaranteed by a combination of multiple standards, the target value of adhesion amount taken in from the instruction information 201 is By adding the maximum values, the target adhesion amount used for control can be calculated in the same procedure.

Next, processing of the first manipulated variable calculation unit 111 will be described. The first manipulated variable calculation unit 111 determines the values of the pressure and the gap of the nozzle 153 that achieve the target coating weight used for control for the next steel sheet, using the coating coating weight prediction model 112 . Formula 1 is stored in the plating deposit prediction model 112 . FIG. 10 shows the processing of the first manipulated variable calculator 111 .

At S10-1, the current plate speed Vc is read from the plating plant 150. Next, in S10-2, from the instruction information 201, the target adhesion amount W* of the next steel sheet and the nozzle gap preset value Dref are read. Finally, in S10-3, the plating deposit prediction model 112 is taken in, the plate speed Vc, the target deposit W*, and the nozzle gap Dref are substituted into Equation 1, and the nozzle pressure P is solved to obtain the nozzle pressure preset value Pref Calculate The nozzle gap preset value Dref and the nozzle pressure preset value Pref are output to the plating plant 150 at a predetermined timing when the welding point 156 approaches and the next steel plate 151 approaches the nozzle 153, and the operation amount is switched.

According to the present invention, by correcting the plating adhesion amount target value using a value corresponding to the risk, it is possible to prevent the plating adhesion amount from falling below the lower limit and to calculate the plating adhesion amount deviation risk for each guarantee standard. Therefore, as a result, a large amount of correction is made for a strict guarantee, and a small amount of correction is made for a lax guarantee. Therefore, excessive plating is not caused by performing many corrections unnecessarily. Therefore, it is possible to improve the yield of the plating raw material.

In this embodiment, the case where the target values of the plating deposits on the front and back sides are the same has been described as an example, but in actual operation, so-called differential thickness plating, in which the target coating weights on the front and back sides are different, is also processed. Even in this case, the present invention can be applied as it is if different values can be specified for the front side and the back side for the target adhesion amount, single-sided lower limit, single-sided one-point lower limit, thinnest point lower limit, etc. of the instruction information 201 . Further, in this embodiment, an example of correcting the adhesion amount target value in consideration of the risk of breaking the lower limit with respect to the guaranteed lower limit standard is shown, but the present invention can be applied to the guaranteed upper limit standard based on the same concept. The present invention can also be applied to a steel sheet in which the lower limit guarantee specification and the upper limit guarantee specification are mixed according to the same idea.

Next, the processing of feedback control section 121 will be described. First, from the deposit amount lower limit value corresponding to each standard taken from the instruction information 201 and the plating deposit actual value of each part taken from the plating deposit amount detector 155, the deposit amount lower limit deviation is calculated. The adhesion amount lower limit deviation can be calculated by subtracting the adhesion amount lower limit value from the adhesion amount actual value. A set ζc of the adhesion amount lower limit deviation distribution of the current steel sheet is expressed by Equation (25).

A set ζc of the lower limit deviation distribution of the deposit amount of the steel sheet is composed of four values of the lower limit deviation of the deposit amount ζc1, ζc2, ζc3, and ζc4. .zeta.c1 is a value obtained by subtracting the lower limit value Wmin_1 of the single-sided guarantee standard from the smaller average adhesion amount for each of the front and back surfaces. ζc2 is a value obtained by subtracting the lower limit value Wmin_2 of the double-sided one-point guarantee standard from the smallest of the left average adhesion amount, the central average adhesion amount, and the right average adhesion amount. ζc3 is a value obtained by subtracting the lower limit value Wmin_3 of the one-side one-point guarantee standard from the smallest adhesion amounts on the left, center, and right sides of each of the front and back surfaces. ζc4 is a value obtained by subtracting the lower limit value Wmin_4 of the standard for guaranteeing the thinnest point from the smaller amount of adhesion at the thinnest point on the front and back sides. Wmin_1 to Wmin_4 are fetched from the corresponding items of the instruction information 201 .

Next, the second guarantee standard determination unit 123 determines the lower limit guarantee standard of the current steel sheet being processed. The example of the instruction information 201 in FIG. 2 indicates that the lower limit guarantee standard is one-sided, and the one-sided lower limit is B [g/m ² ].

Next, the second nonstandard risk calculator 124 and the second margin table 129 will be described. FIG. 11 shows the configuration of the second margin table 129. As shown in FIG. The second margin table 129 stores, for each guaranteed standard and the target value of the coating weight, how much the coating weight deviation exceeds the lower limit to determine that there is no risk of falling below the lower limit as a margin. It is In FIG. 11, for example, when the adhesion amount target value is (B-20) [g/m ² ] or less with one-side guarantee, if the estimated adhesion amount deviation is larger than δY11 with respect to the lower limit value, there is no lower limit cracking risk. It shows that it judges.

FIG. 12 shows the processing of the one-sided guarantee calculation unit 125. As shown in FIG. First, in S12-1, the smaller value Wf_11 of the coating weight on the front and back surfaces measured on the current steel sheet is taken in by Equation (26).

Next, in S12-2, using Wf_11, the single-side lower limit guaranteed value Wmin1 taken in from the instruction information 201, and the value δYj1 extracted from the corresponding stratification from the second margin table 129, according to Equations 27 and 28, Calculate the lower limit cracking risk Wf_12 (nonstandard risk value) of the adhesion amount.

When Wtemp is a negative value, Wf_11 is greater than the guaranteed lower limit plus a margin, indicating that there is no risk of breaking below the lower limit. That is, when Wf_12 is 0, there is no risk of cracking at the lower limit when one-sided one-point guarantee is applied to this steel plate. On the other hand, when Wtemp is a positive value, it indicates that Wf_11 is smaller than the value obtained by adding a margin to the guaranteed lower limit. That is, when Wf_12 is a positive value, it indicates that there is a risk of breaking the lower limit depending on the magnitude of the value.

FIG. 13 shows the processing of the double-sided one-point guarantee calculator 126 . First, in S13-1, the smallest (thinest) value Wf_21 among the single-point deposits on the left side, the center, and the right side, measured on the current steel sheet by Equation 29, is fetched.

Next, in S13-2, using Wf_21, the double-sided one-point guarantee value Wmin2 taken in from the instruction information 201, and the value δYj2 taken out from the corresponding stratification from the second margin table 129, according to Equations 30 and 31, A lower limit cracking risk Wf_22 (non-standard risk value) of the adhesion amount is calculated.

When Wtemp is a negative value, Wf_21 is greater than the guaranteed lower limit plus a margin, indicating that there is no risk of breaking below the lower limit. That is, when Wf_22 is 0, there is no risk of cracking at the lower limit when the double-sided one-point guarantee is applied to this steel plate. On the other hand, when Wtemp is a positive value, it indicates that Wf_21 is smaller than the value obtained by adding a margin to the guaranteed lower limit value. That is, when Wf_22 is a positive value, it indicates that there is a risk of breaking the lower limit depending on the magnitude of the value.

FIG. 14 shows the processing of the one-sided one-point guarantee calculator 127. As shown in FIG. First, in S14-1, the smallest (thinest) value Wf_31 among the left, center, and right one-point adhesion amounts on the front and back sides measured by Equation 32 on the current steel sheet is fetched.

Next, in S14-2, using Wf_31, the one-sided one-point guaranteed value Wmin3 taken from the instruction information 201, and the value δYj3 taken from the corresponding stratification from the second margin table 129, according to Equations 33 and 34, A lower limit cracking risk Wf_32 (non-standard risk value) of the adhesion amount is calculated.

When Wf_32 is 0, it indicates that there is no risk of cracking at the lower limit when one-sided one-point guarantee is applied to this steel plate. On the other hand, when Wf_32 is a positive value, it indicates that there is a risk of breaking the lower limit depending on the magnitude of the value.

FIG. 15 shows the processing of the thinnest point guarantee calculation unit 128. As shown in FIG. First, in S15-1, the smallest (thinnest) value Wf_41 of the thinnest point deposits of the current steel sheet is obtained from the deposit amount distribution on each of the front and back surfaces estimated by Equations 35 to 37 for the current steel sheet.

Next, in S15-2, using Wf_41, the minimum thinnest point value Wmin4 taken in from the indication information 201, and the value δYj4 taken out from the corresponding stratification from the second margin table 129, the following equations 38 and 39 are used: , the lower limit cracking risk Wf_42 (non-standard risk value) of the adhesion amount is calculated.

When Wtemp is a negative value, Wf_41 is greater than the guaranteed lower limit plus a margin, indicating that there is no risk of breaking below the lower limit. That is, when Wf_42 is 0, there is no lower limit crack risk when the thinnest point guarantee is applied to this steel sheet. On the other hand, when Wtemp is a positive value, it indicates that Wf_41 is smaller than the value obtained by adding a margin to the guaranteed lower limit value. That is, when Wf_42 is a positive value, it indicates that there is a risk of breaking the lower limit depending on the magnitude of the value.
Next, the processing of the adhesion amount deviation correction unit 130 will be described. The coating amount deviation correction unit 130 determines the guarantee standard of the next steel sheet, and corrects the plating coating amount deviation using the value of the lower limit cracking risk of the corresponding standard taken in from the second nonstandard risk calculation unit 124 . FIG. 16 shows the processing of the adhesion amount deviation correction unit 130. As shown in FIG. First, in S16-1, the plating amount deviation is calculated. The plating adhesion amount deviation ΔW is the actual value Wact of the plating adhesion amount detected by the plating adhesion amount detector 155 for the steel sheet being processed, and the target plating adhesion taken in from the instruction information 201 corresponding to the steel sheet being processed. It is calculated by the difference in the amount W* (Equation 40).

Next, in S16-2, the lower limit guarantee standard of the next steel sheet is read from the instruction information 201, and the lower limit cracking risk value (non-standard risk value) of the item requiring guarantee is read according to the lower limit guarantee standard. In the example of FIG. 2, the lower limit guarantee standard of the steel plate is one side guarantee, and the guarantee lower limit value is B [g/m ² ]. Finally, in S16-3, the target plating amount is corrected by the lower limit cracking risk value, and the target plating amount (plating amount deviation) used for control is calculated. Specifically, the target adhesion amount used for control is calculated by Equation 41.

On the other hand, depending on the steel plate, it may be guaranteed at one point on both sides or at the thinnest point. There are also steel sheets to which multiple guarantee standards are applied with different minimum guarantee values. For example, there are steel sheets that are guaranteed by a complicated combination of standards, such as guaranteeing the lower limit of one side with B [g/m ² ] and guaranteeing the lower limit of the thinnest point with E [g/m ² ] at the same time. For a steel sheet to which multiple guarantee standards are applied with different lower guarantee values, for example, if one-side guarantee and the lowest guarantee of the thinnest point are applied, it is used for feedback control as shown in Equation 42. Calculate the target adhesion amount.

As in the example shown in this formula 42, even for steel sheets that are guaranteed by a combination of multiple standards, the smallest value among the calculated adhesion amount deviation and the lower limit cracking risk value calculated according to each standard is selected. By doing so, the adhesion amount deviation used for feedback control can be calculated in the same procedure.
Next, processing of the second manipulated variable calculation unit 131 will be described. The second manipulated variable calculation unit 131 determines the values of the pressure and gap of the nozzle 153 that achieve the target coating weight for the steel plate being processed and that take into consideration the risk of cracking the lower limit of the coating coating weight. For example, if this is achieved by manipulating the nozzle pressure, the nozzle pressure Pref can be calculated as shown in Equation (43).

On the other hand, if this is to be achieved by manipulating the nozzle positions, the nozzle gap Dref can be calculated as shown in Equation (44).

As described above, the feedback control unit 121 in FIG. 18 corrects the adhesion amount deviation according to the magnitude of the risk of non-conformance when there is a risk of non-conformity with respect to the guarantee standard of the plating adhesion amount. Furthermore, the feedback control unit 121 corrects the plating adhesion amount deviation in accordance with the risk of cracking the lower limit of the plating adhesion amount, and calculates a control command that causes the plating to adhere thickly.
In this embodiment, the case where the target values of the plating deposits on the front and back sides are the same has been described as an example, but in actual operation, so-called differential thickness plating, in which the target coating weights on the front and back sides are different, is also processed. Even in this case, the present invention can be applied as it is if different values can be specified for the front side and the back side for the target adhesion amount, single-sided lower limit value, single-sided single point lower limit value, thinnest point lower limit value, etc. of the instruction information 201. . Further, in this embodiment, an example of correcting the adhesion amount target value in consideration of the risk of breaking the lower limit with respect to the guaranteed lower limit standard is shown, but the present invention can be applied to the guaranteed upper limit standard based on the same concept. Also, the present invention can be applied to a steel sheet in which the lower limit guarantee specification and the upper limit guarantee specification are mixed.

It can be widely applied to the control of coating weight in steel process lines.

REFERENCE SIGNS LIST 100 Plating adhesion amount control device 101 Preset control unit 102 Preset adhesion amount estimation unit 103 First guarantee standard determination unit 104 First non-standard risk calculation unit 105 Single-sided guarantee calculation unit 106 Double-sided one-point guarantee calculation unit 107 Single-sided one-point guarantee calculation unit 108 thinnest point guarantee calculation unit 109 first margin table 110 target adhesion amount correction unit 111 first manipulated variable calculation unit 112 plating adhesion amount prediction model 121 feedback control unit 122 adhesion amount deviation calculation unit 123 second guarantee standard determination Section 124 Second non-standard risk calculator 125 Single-sided guarantee calculator 126 Double-sided one-point guarantee calculator 127 Single-sided one-point guarantee calculator 128 Thinnest point guarantee calculator 129 Second margin table 130 Adhesion amount deviation corrector 131 Second Operation amount calculator 150 Plating plant 151 Steel plate (strip)
153 nozzle 155 plating deposit detector 156 welding point

Claims (8)

A continuously sent steel sheet is immersed in a bath of a hot-dip coating bath, the hot-dip coating bath is applied to the steel sheet, and after being lifted out of the bath, gas is supplied to the steel sheet from the front nozzle and the back nozzle provided on the front and back of the steel sheet. is sprayed to remove the excessively adhered hot dipping bath to adhere the hot dipping bath of the desired thickness to the steel sheet.
A coating weight prediction model that describes the relationship between the plate speed, nozzle pressure, distance between the nozzle and the steel plate, and the coating weight that adheres to the steel plate;
The nozzle pressure and nozzle position for depositing the desired plating on the next steel sheet that is connected to the current steel sheet that is currently being plated at the welding point and that is to be plated next to the current steel sheet is determined using the coating amount prediction model. Equipped with a preset control unit that calculates
The preset control unit
a preset adhesion amount estimating unit for estimating the plating adhesion amount of the steel sheet obtained as a result of the preset control;
a first guarantee standard determination unit that determines which of a plurality of guarantee standards of the next steel sheet is one;
Based on the estimated coating weight and the guaranteed standard of the steel sheet, as a result of the preset control, the occurrence of the non-standard risk that the next steel sheet is out of the guaranteed standard is determined, and the non-standard risk value is calculated. First non-standard risk calculation Department and
A target adhesion amount correction unit that corrects the target plating adhesion amount of the next steel sheet with the non-standard risk value output by the first non-standard risk calculation unit;
A first manipulated variable calculation for calculating at least one of a nozzle pressure command value and a nozzle position command value for realizing the corrected target deposit amount as a desired deposit amount by calculation using the plating deposit amount prediction model. having a department ,
The first non-standard risk calculation unit
Equipped with a first margin table in which the first margin is stored in association with the guaranteed standard and the coating weight,
When the difference between the value determined as the guarantee standard of the steel sheet and the estimated coating amount is equal to or less than the first margin value extracted from the first margin table, the next steel sheet is out of specification. Determining the occurrence of risk
A plating adhesion amount control device characterized by: A feedback control unit that calculates the deviation between the actual value of the coating amount measured from the steel sheet and the target coating amount, and changes the operation amount of at least one of the nozzle pressure and the nozzle position so that the deviation becomes small. prepared,
The feedback control unit is
an adhesion amount deviation calculation unit that calculates the deviation between the actual value of the plating adhesion amount measured from the steel sheet and the guaranteed standard value of the steel sheet;
Based on the outputs of the second guarantee standard determination unit that determines the guarantee standard of the current steel sheet, the adhesion amount deviation calculation unit, and the second guarantee standard determination unit, it is determined whether the current steel sheet is out of the guarantee standard. , a second non-standard risk calculation unit that calculates the non-standard risk value;
an adhesion amount deviation correction unit that corrects the deviation with the nonstandard risk value output by the second nonstandard risk calculation unit;
a second operation amount calculator that changes at least one of the nozzle pressure command value and the nozzle position command value so that the absolute value of the corrected deviation becomes small ;
The second non-standard risk calculation unit
Equipped with a second margin table in which the second margin is stored in association with the guaranteed standard and the coating weight,
When the difference between the actual value of the coating amount measured from the steel sheet and the value determined as the guarantee standard of the steel sheet is equal to or less than the second margin value extracted from the second margin table, the current steel sheet to determine the occurrence of out-of-specification risks for
The plating deposition amount control device according to claim 1, characterized by: The first non-standard risk calculation unit
A one-side guarantee calculation unit that calculates a non-standard risk value using the thinner value of the coating amount predicted on the front and back sides of the steel sheet;
A double-sided one-point guarantee calculation unit that calculates a non-standard risk value using the smallest value among the average adhesion amounts on the front and back of the three points in the width direction of the steel plate consisting of the left side, the center, and the right side;
a one-sided one-point guarantee calculation unit that calculates a nonstandard risk value using the smallest value among the left, center, and right adhesion amount distributions in the width direction of the front and back surfaces of the steel plate;
a thinnest point guarantee calculation unit that calculates a non-standard risk value using the smallest value of the adhesion amount distribution in the width direction of the front surface and the back surface of the steel plate,
The target adhesion amount correction unit
The plating adhesion amount control according to claim 1 , wherein the target plating adhesion amount of the next steel sheet is corrected with the largest risk value among the non-standard risk values output by the first non-standard risk calculation unit. Device. The second non-standard risk calculation unit
A one-side guarantee calculation unit that calculates a non-standard risk value using the thinner value of the plating adhesion amounts measured on the front and back sides of the steel sheet;
A double-sided one-point guarantee calculation unit that calculates a non-standard risk value using the smallest value among the average adhesion amounts on the front and back of the three points in the width direction of the steel plate consisting of the left side, the center, and the right side;
a one-sided one-point guarantee calculation unit that calculates a nonstandard risk value using the smallest value among the left, center, and right adhesion amount distributions in the width direction of the front and back surfaces of the steel plate;
a thinnest point guarantee calculation unit that calculates a non-standard risk value using the smallest value of the adhesion amount distribution in the width direction of the front surface and the back surface of the steel plate,
The adhesion amount deviation correction unit
The deviation between the actual value of the plating adhesion amount and the target plating adhesion amount is corrected by the largest risk value among the non-standard risk values output by the second non-standard risk calculation unit. Item 3. The plating deposition amount control device according to item 2. A continuously sent steel sheet is immersed in a bath of a hot-dip coating bath, the hot-dip coating bath is applied to the steel sheet, and after being lifted out of the bath, gas is supplied to the steel sheet from the front nozzle and the back nozzle provided on the front and back of the steel sheet. and removing the excessively adhered hot dipping bath to adhere a hot dipping bath of a desired thickness to the steel plate.
The coating weight control device is
A coating weight prediction model that describes the relationship between the plate speed, nozzle pressure, distance between the nozzle and the steel plate, and the coating weight that adheres to the steel plate;
The nozzle pressure and nozzle position for depositing the desired plating on the next steel sheet that is connected to the current steel sheet that is currently being plated at the welding point and that is to be plated next to the current steel sheet is determined using the coating amount prediction model. Equipped with a preset control unit that calculates
The preset control unit includes a preset adhesion amount estimation unit, a first guaranteed standard determination unit, a first nonstandard risk calculation unit, a target adhesion amount correction unit, and a first manipulated variable calculation unit. cage,
The preset adhesion amount estimating unit estimates the plating adhesion amount of the steel sheet obtained as a result of the preset control,
The first guarantee standard determination unit determines which one of a plurality of guarantee standards of the next steel sheet is,
The first non-standard risk calculation unit determines the occurrence of a non-standard risk that the next steel sheet is out of the guaranteed standard as a result of the preset control from the estimated coating amount and the guaranteed standard of the steel sheet, and determines the non-standard risk. Calculate the value of
The target adhesion amount correction unit corrects the target plating adhesion amount of the next steel sheet with the non-standard risk value output by the first non-standard risk calculation unit,
The first operation amount calculation unit uses the corrected target adhesion amount as the desired adhesion amount, and calculates at least one of the nozzle pressure command value and the nozzle position command value that realizes the desired adhesion amount using the plating adhesion amount prediction model. It is calculated by arithmetic operation ,
The first non-standard risk calculation unit
Equipped with a first margin table in which the first margin is stored in association with the guaranteed standard and the coating weight,
When the difference between the value determined as the guarantee standard of the steel sheet and the estimated coating amount is equal to or less than the first margin value extracted from the first margin table, the next steel sheet is out of specification. Determining the occurrence of risk
A plating adhesion amount control method characterized by: The plating deposition amount control device is
A feedback control unit that calculates the deviation between the actual value of the coating amount measured from the steel sheet and the target coating amount, and changes the operation amount of at least one of the nozzle pressure and the nozzle position so that the deviation becomes small. prepared,
The feedback control unit includes an adhesion amount deviation calculation unit, a second guarantee standard determination unit, a second out-of-standard risk calculation unit, an adhesion amount deviation correction unit, and a second manipulated variable calculation unit. cage,
The adhesion amount deviation calculation unit calculates the deviation between the actual value of the plating adhesion amount measured from the steel sheet and the guaranteed standard value of the steel sheet,
The second warranty standard determination unit determines the warranty standard of the current steel sheet,
The second non-standard risk calculation unit determines the occurrence of a non-standard risk that the current steel sheet is out of the guaranteed standard from the output of the adhesion amount deviation calculation unit and the second guaranteed standard determination unit, and determines the non-standard risk. Calculate the value of
The adhesion amount deviation correction unit corrects the deviation with the non-standard risk value output by the second non-standard risk calculation unit,
The second operation amount calculation unit changes at least one of the nozzle pressure command value and the nozzle position command value so that the absolute value of the corrected deviation becomes small ,
The second non-standard risk calculation unit
Equipped with a second margin table in which the second margin is stored in association with the guaranteed standard and the coating weight,
When the difference between the actual value of the coating amount measured from the steel sheet and the value determined as the guarantee standard of the steel sheet is equal to or less than the second margin value extracted from the second margin table, the current steel sheet to determine the occurrence of out-of-specification risks for
The plating deposit control method according to claim 5, characterized by: The first non-standard risk calculation unit
A one-side guarantee calculation unit that calculates a non-standard risk value using the thinner value of the coating amount predicted on the front and back sides of the steel sheet;
A double-sided one-point guarantee calculation unit that calculates a non-standard risk value using the smallest value among the average adhesion amounts on the front and back of the three points in the width direction of the steel plate consisting of the left side, the center, and the right side;
a one-sided one-point guarantee calculation unit that calculates a nonstandard risk value using the smallest value among the left, center, and right adhesion amount distributions in the width direction of the front and back surfaces of the steel plate;
a thinnest point guarantee calculation unit that calculates a non-standard risk value using the smallest value of the adhesion amount distribution in the width direction of the front surface and the back surface of the steel plate,
The target adhesion amount correction unit
The plating adhesion amount control according to claim 5, wherein the target plating adhesion amount of the next steel sheet is corrected with the largest risk value out of the nonstandard risk values output by the first nonstandard risk calculation unit. Method. The second non-standard risk calculation unit
A one-side guarantee calculation unit that calculates a non-standard risk value using the thinner value of the plating adhesion amounts measured on the front and back sides of the steel sheet;
A double-sided one-point guarantee calculation unit that calculates a non-standard risk value using the smallest value among the average adhesion amounts on the front and back of the three points in the width direction of the steel plate consisting of the left side, the center, and the right side;
a one-sided one-point guarantee calculation unit that calculates a nonstandard risk value using the smallest value among the left, center, and right adhesion amount distributions in the width direction of the front and back surfaces of the steel plate;
a thinnest point guarantee calculation unit that calculates a non-standard risk value using the smallest value of the adhesion amount distribution in the width direction of the front surface and the back surface of the steel plate,
The adhesion amount deviation correction unit
The deviation between the actual value of the plating adhesion amount and the target plating adhesion amount is corrected by the largest risk value among the non-standard risk values output by the second non-standard risk calculation unit. Item 7. The method for controlling the amount of plating deposited according to Item 6.

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