JP5585033B2 - Plate temperature control system, method and program in continuous heat treatment furnace - Google Patents

Description

  The present invention relates to a plate temperature control system, method, and program in a continuous heat treatment furnace that controls the plate temperature of a strip-shaped steel plate heat-treated in a continuous heat treatment furnace in a continuous annealing factory, a continuous hot dip galvanizing factory, or the like of an ironworks.

  For example, in a continuous annealing plant of a steel mill, a steel sheet (strip) after cold rolling is sent to an annealing process and annealed. In the annealing step, for example, as shown in FIG. 4, the steel plate 1 is inserted into the direct fire heating zone L by the drive roll 2 and heated directly. Subsequently, after being indirectly heated through the indirect heating zone M, it is cooled through the cooling zone N. In the direct heating zone L, the combustion gas and air are blown out from the combustion burner 4 to directly heat the steel plate 1 by direct fire combustion, and in the indirect heating zone M, the steel plate 1 is indirectly heated by the radiant tube 5. Thermometers 6 and 7 are arranged on the exit side of the direct fire heating zone L and the exit side of the indirect heating zone M, respectively, and measure the actual plate temperature.

  Regarding a plate temperature control method in this type of continuous heat treatment furnace, for example, Patent Documents 1 and 2 disclose a method of predicting a plate temperature on the furnace exit side using a model formula and determining an operation amount.

JP-A-1-259131 JP 7-278682 A

  By the way, in the continuous heat treatment furnace, when the target plate temperature on the outlet side of the furnace side is changed (near the center of the steel plate) when the pretreatment process (referred to as the previous step) or the target plate temperature on the outlet side of the continuous heat treatment furnace changes. The degree of variation in the plate temperature in the longitudinal direction differs.

  In addition, at the tip and tail end of the steel plate that is passed through the annealing furnace, the measured value by the plate thermometer may show a sudden change different from the true plate temperature due to the influence of the surface properties of the steel plate. is there.

  In the prior art, plate temperature control is not performed in accordance with variations in plate temperature in the longitudinal direction of the steel plate and sudden plate temperature fluctuations that occur at the tip and tail ends of the steel plate. Even in the methods disclosed in Patent Documents 1 and 2 and the like described above, model formulas associated with fluctuations in sheet temperature variation in the longitudinal direction of the steel sheet, and rapid sheet temperature fluctuations occurring at the tip and tail ends of the steel sheet. It does not have the correction function.

  The present invention has been made in view of the above points, and is a plate that responds to variations in the plate temperature in the longitudinal direction of the steel plate, and sudden plate temperature fluctuations that occur at the tip and tail ends of the steel plate. The purpose is to enable temperature control.

The plate temperature control system in the continuous heat treatment furnace of the present invention is a plate temperature control system in a continuous heat treatment furnace that feedback-controls the plate temperature of a strip-shaped steel plate that is heat-treated in the continuous heat treatment furnace, and includes pre-process information of the continuous heat treatment, Feedback control gain storage means for storing the target plate temperature on the furnace exit side in association with the feedback control gain, and feedback read from the feedback control gain storage means in accordance with the previous process information and the target plate temperature on the furnace exit side A feedback control means for determining an operation amount for causing the actual plate temperature on the delivery side of the continuous heat treatment furnace to follow the target plate temperature on the delivery side based on the control gain, and executing feedback control; According to the actual plate temperature variation information in the longitudinal direction of the steel plate based on the actual plate temperature on the delivery side and the plate temperature change amount for each feedback control cycle An update means for obtaining a temperature change influence coefficient, and updating the feedback control gain stored in the feedback control gain storage means in accordance with the actual board temperature variation information and the plate temperature change influence coefficient; based on the results metal temperature furnace exit side, the sheet temperature variation information computing means for the actual plate temperature variation sigma _a is a proven plate temperature variation information in the longitudinal direction of the steel sheet according to expression (1), exits the furnace Plate temperature change influence coefficient calculating means for calculating a plate temperature change influence coefficient β according to the amount of change in plate temperature for each feedback control cycle based on the actual plate temperature on the side, using equation (2) , and the plate temperature variation Using the actual plate temperature variation σ _a calculated by the information calculation means and the plate temperature change influence coefficient β calculated by the plate temperature change influence coefficient calculation means, a new feedback control gain FB _{g is obtained} by Expression (3). _{ain (new)} is calculated, and the feedback control gain stored in the feedback control gain storage means is updated.
σ _a = sqrt (Σ (TS _ave −TS _a (i)) ² / j) (1)
Where TS _ave = ΣTS _a (i) / j
TS _a : Actual temperature at the furnace exit side
i: Order of control cycle, 1, 2,...
Σ: Sum from i = 1 to j
β = k1 × exp (−k2 × (TS _a (j) −TS _a (j−1))) (2)
Where k1, k2: constants set in advance by the operator
FB _{gain (new)} = FB _{gain (old)}
−β × ln (σ _a / σ _T ) × ((Δu−DNC) / DNC) (3)
Here, Δu = u (j) −u (j−1)
FB _{gain (old)} : Feedback control gain before update
σ _T : Target plate temperature variation
DNC: Manipulation amount change amount limit value
u (j): Actual operation amount (actual value of the amount of fuel to be input)
j: jth control period from the tip of the coil to be controlled The plate temperature control method in the continuous heat treatment furnace of the present invention is a plate temperature control in a continuous heat treatment furnace that feedback-controls the plate temperature of a strip-shaped steel plate heat-treated in the continuous heat treatment furnace. A feedback control gain storage means for storing the pre-process information of the continuous heat treatment furnace, the target plate temperature on the furnace exit side, and the feedback control gain in association with each other. Based on the feedback control gain read in response to this, the amount of operation for causing the actual sheet temperature on the outlet side of the continuous heat treatment furnace to follow the target plate temperature on the outlet side is determined and executed in a predetermined fixed period and feedback control is executed. Plate temperature variation influence information in the longitudinal direction of the steel plate based on the actual plate temperature on the furnace exit side and the plate temperature variation influence coefficient according to the plate temperature variation amount for each feedback control cycle And obtaining a feedback control gain stored in the feedback control gain storage means in accordance with the actual plate temperature variation information and the plate temperature change influence coefficient. Based on the actual plate temperature of the steel plate, feedback based on the procedure for calculating the actual plate temperature variation σ _a , which is actual plate temperature variation information in the longitudinal direction of the steel plate, using the formula (1) and the actual plate temperature on the furnace exit side And calculating the plate temperature change influence coefficient β according to the plate temperature change amount for each control cycle according to the equation (2). The calculated actual plate temperature variation σ _a and the calculated plate temperature change influence coefficient β and calculating a new feedback control gain FB _{gain (new new)} by equation (3) using, to and updates the feedback control gain stored in the feedback control gain storage unit .
The program of the present invention is a program for feedback control of the plate temperature of a strip-shaped steel plate heat-treated in a continuous heat treatment furnace, and includes information on the previous process of the continuous heat treatment furnace, a target plate temperature on the furnace exit side, and feedback control. Based on the feedback control gain read in accordance with the previous process information and the target plate temperature on the furnace outlet side from the feedback control gain storage means for storing the gain in association with each other, the outlet side of the continuous heat treatment furnace at a predetermined constant cycle The process of determining the operation amount for causing the actual plate temperature of the steel plate to follow the target plate temperature on the delivery side and executing feedback control, the actual plate temperature variation information in the longitudinal direction of the steel sheet based on the actual plate temperature on the furnace exit side, and A plate temperature change influence coefficient corresponding to the plate temperature change amount for each feedback control cycle is obtained, and the feedback control gain is determined according to the actual plate temperature variation information and the plate temperature change influence coefficient. To execute a process of updating the feedback control gain stored in the storage unit in a computer, the process of the update, based on the actual plate temperature of the furnace exit side, in actual plate temperature variation information in the longitudinal direction of the steel sheet Based on the process of calculating a certain actual plate temperature variation σ _a by the equation (1) and the actual plate temperature on the furnace exit side, the plate temperature change influence coefficient β corresponding to the plate temperature change amount for each feedback control cycle is expressed by the equation ( 2), and _a new feedback control gain FB _{gain (new)} is calculated by Equation (3) using the calculated actual plate temperature variation σ _a and the calculated plate temperature change influence coefficient β. Then, the feedback control gain stored in the feedback control gain storage means is updated.

  According to the present invention, the plate temperature change influence coefficient corresponding to the plate temperature variation information in the longitudinal direction of the steel plate based on the plate temperature on the furnace exit side and the plate temperature change amount for each feedback control cycle is obtained, and the plate temperature Since the feedback control information stored in the feedback control information storage means is updated according to the variation information and the plate temperature change influence coefficient, the plate temperature variation in the longitudinal direction of the steel plate and the plate for each feedback control cycle The plate temperature can be controlled according to the amount of temperature change, and the plate temperature control accuracy can be improved.

It is a figure which shows schematic structure of the plate | board temperature control system in the continuous heat processing furnace of this embodiment. It is a flowchart which shows the update process of the FB control gain in the plate | board temperature control system in the continuous heat processing furnace of this embodiment. It is a figure for demonstrating the content of the control gain database. It is a figure for demonstrating the example of an annealing process.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.
In FIG. 1, it is a figure which shows schematic structure of the plate temperature control system in the continuous heat processing furnace of this embodiment. The plate temperature control system in the continuous heat treatment furnace of the present embodiment controls the plate temperature of a strip-shaped steel plate (not shown) to be heat treated in the continuous heat treatment furnace 200, and includes a control gain calculation unit 101, feed forward (FF). A controller 102 and a feedback (FB) controller 103 are provided.

  Further, a control gain database (DB) 104, a constant DB 105, a process performance DB 106, and a manufacturing instruction DB 107 are provided. In FIG. 1, for convenience, the DB is illustrated by function, but the number is not limited.

The control gain DB 104 stores an FF control gain FF _gain [−] for FF control by the FF controller 102 and an FB control gain FB _gain [−] for FB control by the FB controller 103. Regarding the FB control gain FB _gain , in the control gain DB 104, as shown in FIG. 3, according to the FB control gain table, the previous process information X _{1 to} X _m [−], the target plate temperature TS _s [° C. on the furnace exit side. ] In relation to n regions (α _k (k = 1, 2,..., N−1) is a target plate temperature threshold [° C.]) and FB control gain FB _gain (m, n). doing. Pre-process the information X _1, ···, X _m is information indicating the type of the previous step of heat treatment in a continuous heat treatment furnace, pickling and cold-rolling process and the like if the previous step annealing process. Moreover, even if it is the same pickling process, you may handle as a mutually different previous process depending on the processing content. In the present embodiment, the FB control gain FB _gain corresponds to the feedback control information referred to in the present invention, and the control gain DB 104 functions as feedback control information storage means referred to in the present invention.

The constant DB 105 stores initial data which are set values on continuous heat treatment such as a target plate temperature variation σ _T [° C.], an operation amount change amount limit value DNC [−] (constant), and the like. For example, for the target plate temperature variation σ _T , a value corresponding to the plate temperature variation in the longitudinal direction (plate passing direction) of an allowable steel plate is preset for each coil to be controlled for each type of coil to be controlled. Yes.

The process performance DB 106 is the total performance data in the plate temperature control for each FB control cycle for the control target coil, specifically, the actual plate temperature TS _a (i) [° C.] on the furnace exit side, and the FB controller 103 outputs The actual operation amount u (i) [−] is stored (i: control cycle, i = 1, 2,..., N). In addition, i which shows the order of a control period is attached | subjected with 1, 2, ... from the front-end | tip of a control object coil.

The manufacturing command DB 107 stores manufacturing command data such as a plate width, a plate thickness, a target plate temperature TS _s on the furnace exit side, and preprocess information X _{1 to} X _m for the control target coil. In many cases, the manufacturing order data is input from a host computer that manages the production plan via a network.

The control gain calculation unit 101 reads the FF control gain FF _gain and the FB control gain FB _gain from the control gain DB 104, outputs the FF control gain FF _gain to the FF controller 102, and outputs the FB control gain FB _gain to the FB controller 103. . Regarding the FB control gain FB _gain , for example, when the previous process information acquired from the manufacturing instruction DB 107 is X ₁ and the target plate temperature on the furnace exit side is α ₁ ≦ TS _s <α ₂ , as shown in FIG. The FB control gain FB _gain (1, 2) is read from the control gain DB 104 (FB control gain table).

Further, the control gain calculation unit 101 will be described in detail later, but the actual plate temperature variation σ _a [° C.] in the longitudinal direction of the steel plate based on the actual plate temperature TS _a (i) on the furnace exit side, and the feedback control cycle The FB control gain stored in the control gain DB 104 is determined for each plate temperature change amount, and the plate temperature change influence coefficient β calculated from the actual plate temperature variation σ _a and the plate temperature change amount for each feedback control cycle. Update FB _gain in real time. In other words, in the present embodiment, the control gain calculation unit 101 functions as an updating unit referred to in the present invention. The control gain calculation unit 101 includes a plate temperature variation information calculation unit that calculates the actual plate temperature variation σ _a [° C.], and a plate temperature that calculates the plate temperature change influence coefficient β from the plate temperature change amount for each feedback control cycle. Change influence coefficient calculation means.

The FF controller 102 determines an operation amount for the continuous heat treatment furnace 200 based on the FF control gain FF _gain received from the control gain calculation unit 101, and executes FF control. The FF controller 102 receives welding point passage information on the furnace entry side and exit side and speed change information on the line speed, and conditions such as welding point passage (coil change) and speed change on the furnace entry side and exit side. FF control is executed when there is a change.

The FB controller 103 determines an operation amount for the continuous heat treatment furnace 200 based on the FB control gain FB _gain received from the control gain calculation unit 101, and executes FB control. That is, in this embodiment, the FB controller 103 functions as a feedback control means in the present invention. The FB controller 103 executes FB control at a constant cycle of, for example, about 30 seconds.

  FIG. 2 is a flowchart showing the update processing of the FB control gain in the plate temperature control system in the continuous heat treatment furnace of the present embodiment. The update process shown in the flowchart of FIG. 2 is executed by the control gain calculation unit 101 at the FB control timing (fixed period).

First, in step S101, initial data of setting values relating to control of continuous heat treatment such as the target plate temperature variation σ _T and the manipulated variable change amount limit value DNC is read from the constant DB 105. Here, step S101 is described in the flowchart of FIG. 2 that is executed at regular intervals, but the initial data that has been read once is retained, and the process of step S101 is performed only when the initial data is changed. May be executed.

In step S102, the FB control gain FB _gain is read from the control gain DB 104 based on the pre-process information X _{1 to} X _m for the control target coil acquired from the manufacturing instruction DB 107 and the target plate temperature TS _s on the furnace exit side. For example, when the previous process information acquired from the manufacturing instruction DB 107 is X ₁ and the target plate temperature on the furnace exit side is α ₁ ≦ TS _s <α ₂ , as shown in FIG. 3, the control gain DB 104 (FB control gain table) The FB control gain FB _gain (1, 2) is read from.

Next, in step S103, when it is the i = jth control cycle in order from the tip of the control target coil, all the actual data for each FB control cycle for the control target coil from the process performance DB 106, specifically, The actual operation plate temperature TS _a (j) on the furnace exit side and the actual operation amount u (i) output from the FB controller 103 are read (i = 1, 2,..., J). Here, the actual operation amount u (j) is the actual value of the amount of fuel to be input.

Next, in step S104, the actual sheet temperature variation σ _a in the longitudinal direction of the steel sheet for the control target coil is reduced based on the furnace-side actual sheet temperature TS _a (i) read in step S103. Calculation is performed according to equation (1). This step S104 is an example of processing as the plate temperature variation information calculating means referred to in the present invention. Note that Σ is the sum of i = 1 to j.
σ _a = sqrt (Σ (TS _ave −TS _a (i)) ² / j) (1)
Where TS _ave = ΣTS _a (i) / j
Further, an average value of absolute values of (TS _ave −TS _a (i)) may be used instead of the equation (1).

Next, in step S105, the plate temperature change influence coefficient β for the coil to be controlled is calculated according to the following (2) based on the furnace-side actual plate temperature TS _a (j) read in step S103. . This step S105 is a processing example as a plate temperature change influence coefficient calculating means in the present invention. Here, k1 and k2 are constants set in advance by the operator, may be determined based on the performance of the control performance, or may be set by numerical simulation.
β = k1 × exp (−k2 × (TS _a (j) −TS _a (j−1))) (2)

Next, the process proceeds to step S106, and a new FB control gain FB _{gain (new)} is calculated by the following equation (3).
FB _{gain (new)} = FB _{gain (old)}
−β × ln (σ _a / σ _T ) × ((Δu−DNC) / DNC) (3)
Here, Δu = u (j) −u (j−1)

Here, in the right side of the equation (3), ln (σ _a / σ _T ) is a plate temperature fluctuation influence coefficient representing the effect of plate temperature variation in the longitudinal direction of the steel plate, and (Δu−DNC) / DNC is an operation. This is a manipulated variable fluctuation influence coefficient representing the influence of the quantity fluctuation.

Thereafter, in step S107, the FB control gain FB _{gain (old)} stored in the control gain DB 104 is updated using the _new FB control gain FB _{gain (new)} calculated in step S106.

As described above, the actual sheet temperature variation σ _a and the sheet temperature change influence coefficient β in the longitudinal direction of the steel sheet based on the actual sheet temperature TS _a (i) on the furnace exit side are expressed by the equations (1) and (2) , respectively. ) , And _a new feedback control gain FB _{gain (new)} is calculated by Equation (3) according to the actual plate temperature variation σ _a and the plate temperature change influence coefficient β, and stored in the control gain DB 104. Since the FB control gain FB _{gain (old)} is updated, it is possible to dynamically control the plate temperature according to the variation in the plate temperature in the longitudinal direction of the steel plate according to the furnace shape. Thereafter, when the continuous heat treatment of the coil to be controlled is not completed, the process returns to step S103 and the process is repeated.

  The control gain calculation unit 101, the FF controller 102, and the FB controller 103 can be specifically realized by a computer device including a CPU and various memories, and may be configured by one device or a plurality of devices. It may be constituted by.

  The object of the present invention can also be achieved by supplying a storage medium storing software program codes for realizing the functions of the above-described embodiments to a system or apparatus. In this case, the computer (or CPU or MPU) of the system or apparatus reads and executes the program code stored in the storage medium.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the program code itself and the storage medium storing the program code constitute the present invention. As a storage medium for supplying the program code, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

DESCRIPTION OF SYMBOLS 101 Control gain calculation part 102 Feedforward controller 103 Feedback controller 104 Control gain database 105 Constant database 106 Process performance database 107 Manufacturing command database 200 Continuous heat treatment furnace

Claims (4)

A plate temperature control system in a continuous heat treatment furnace for feedback control of the plate temperature of a strip-shaped steel plate heat-treated in a continuous heat treatment furnace,
Feedback control gain storage means for storing the pre-process information of continuous heat treatment, the target plate temperature on the furnace exit side, and the feedback control gain in association with each other;
Based on the feedback control gain read from the feedback control gain storage means according to the previous process information and the target plate temperature on the furnace exit side, the actual sheet temperature on the exit side of the continuous heat treatment furnace is output on the output side at a predetermined fixed period. Feedback control means for determining an operation amount for following the target plate temperature and executing feedback control;
The actual plate temperature variation information in the longitudinal direction of the steel sheet based on the actual plate temperature on the furnace exit side and the plate temperature change influence coefficient corresponding to the plate temperature change amount for each feedback control cycle are obtained, and the actual plate temperature variation information and the plate Updating means for updating the feedback control gain stored in the feedback control gain storage means according to the temperature change influence coefficient,
The updating means includes
Based on the actual sheet temperature on the furnace exit side, the sheet temperature variation information calculating means for calculating the actual sheet temperature variation σ _a which is the actual sheet temperature variation information in the longitudinal direction of the steel sheet according to the equation (1) ;
A plate temperature change influence coefficient calculating means for calculating a plate temperature change influence coefficient β according to the plate temperature change amount for each feedback control cycle based on the actual plate temperature on the furnace exit side according to the equation (2) ;
Using the actual plate temperature variation σ _a calculated by the plate temperature variation information calculation means and the plate temperature change influence coefficient β calculated by the plate temperature change influence coefficient calculation means, a new feedback control gain FB _{gain is obtained} by Expression (3). _(new) is calculated to update the feedback control gain stored in the feedback control gain storage means.
σ _a = sqrt (Σ (TS _ave −TS _a (i)) ² / j) (1)
Where TS _ave = ΣTS _a (i) / j
TS _a : Actual temperature at the furnace exit side
i: Order of control cycle, 1, 2,...
Σ: Sum from i = 1 to j
β = k1 × exp (−k2 × (TS _a (j) −TS _a (j−1))) (2)
Where k1, k2: constants set in advance by the operator
FB _{gain (new)} = FB _{gain (old)}
−β × ln (σ _a / σ _T ) × ((Δu−DNC) / DNC) (3)
Here, Δu = u (j) −u (j−1)
FB _{gain (old)} : Feedback control gain before update
σ _T : Target plate temperature variation
DNC: Manipulation amount change amount limit value
u (j): Actual operation amount (actual value of the amount of fuel to be input)
j: jth control cycle from the tip of the coil to be controlled The feedback control means executes feedback control at a constant cycle,
2. The plate temperature control system in a continuous heat treatment furnace according to claim 1, wherein the updating means executes a feedback control gain updating process at a feedback control timing by the feedback control means. A plate temperature control method in a continuous heat treatment furnace for feedback control of the plate temperature of a strip-shaped steel plate heat-treated in a continuous heat treatment furnace,
Reads according to the previous process information and the target plate temperature on the furnace exit side from the feedback control gain storage means for storing the pre-process information of the continuous heat treatment furnace, the target plate temperature on the furnace exit side, and the feedback control gain. Based on the feedback control gain, a procedure for performing feedback control by determining an operation amount for causing the actual plate temperature on the outlet side of the continuous heat treatment furnace to follow the target plate temperature on the outlet side at a predetermined fixed period;
The actual plate temperature variation information in the longitudinal direction of the steel sheet based on the actual plate temperature on the furnace exit side and the plate temperature change influence coefficient corresponding to the plate temperature change amount for each feedback control cycle are obtained, and the actual plate temperature variation information and the plate Updating the feedback control gain stored in the feedback control gain storage means according to the temperature change influence coefficient,
The updating procedure is as follows:
Based on the actual sheet temperature on the furnace exit side, a procedure for calculating the actual sheet temperature variation σ _a which is the actual sheet temperature variation information in the longitudinal direction of the steel sheet by the equation (1) ;
And a procedure for calculating a plate temperature change influence coefficient β according to the plate temperature change amount for each feedback control cycle based on the actual plate temperature on the furnace exit side according to the equation (2) ,
Using the calculated actual plate temperature variation σ _a and the calculated plate temperature change influence coefficient β , a new feedback control gain FB _{gain (new)} is calculated by Equation (3) , and the feedback control gain storage means A plate temperature control method in a continuous heat treatment furnace, wherein a stored feedback control gain is updated.
σ _a = sqrt (Σ (TS _ave −TS _a (i)) ² / j) (1)
Where TS _ave = ΣTS _a (i) / j
TS _a : Actual temperature at the furnace exit side
i: Order of control cycle, 1, 2,...
Σ: Sum from i = 1 to j
β = k1 × exp (−k2 × (TS _a (j) −TS _a (j−1))) (2)
Where k1, k2: constants set in advance by the operator
FB _{gain (new)} = FB _{gain (old)}
−β × ln (σ _a / σ _T ) × ((Δu−DNC) / DNC) (3)
Here, Δu = u (j) −u (j−1)
FB _{gain (old)} : Feedback control gain before update
σ _T : Target plate temperature variation
DNC: Manipulation amount change amount limit value
u (j): Actual operation amount (actual value of the amount of fuel to be input)
j: jth control cycle from the tip of the coil to be controlled A program for feedback control of the plate temperature of a strip-shaped steel plate heat-treated in a continuous heat treatment furnace,
Reads according to the previous process information and the target plate temperature on the furnace exit side from the feedback control gain storage means for storing the pre-process information of the continuous heat treatment furnace, the target plate temperature on the furnace exit side, and the feedback control gain. Based on the feedback control gain, a process for determining an operation amount for causing the actual plate temperature on the outlet side of the continuous heat treatment furnace to follow the target plate temperature on the outlet side at a predetermined fixed period, and executing feedback control;
The actual plate temperature variation information in the longitudinal direction of the steel sheet based on the actual plate temperature on the furnace exit side and the plate temperature change influence coefficient corresponding to the plate temperature change amount for each feedback control cycle are obtained, and the actual plate temperature variation information and the plate temperature are obtained. In response to the change influence coefficient, the computer executes a process of updating the feedback control gain stored in the feedback control gain storage means,
The update process is as follows:
Based on the actual sheet temperature on the furnace exit side, a process of calculating the actual sheet temperature variation σ _a which is the actual sheet temperature variation information in the longitudinal direction of the steel sheet by the equation (1) ;
A process of calculating a plate temperature change influence coefficient β according to the plate temperature change amount for each feedback control cycle based on the actual plate temperature on the furnace exit side by the equation (2) ,
Using the calculated actual plate temperature variation σ _a and the calculated plate temperature change influence coefficient β , a new feedback control gain FB _{gain (new)} is calculated by Equation (3) , and the feedback control gain storage means A program for updating a stored feedback control gain.
σ _a = sqrt (Σ (TS _ave −TS _a (i)) ² / j) (1)
Where TS _ave = ΣTS _a (i) / j
TS _a : Actual temperature at the furnace exit side
i: Order of control cycle, 1, 2,...
Σ: Sum from i = 1 to j
β = k1 × exp (−k2 × (TS _a (j) −TS _a (j−1))) (2)
Where k1, k2: constants set in advance by the operator
FB _{gain (new)} = FB _{gain (old)}
−β × ln (σ _a / σ _T ) × ((Δu−DNC) / DNC) (3)
Here, Δu = u (j) −u (j−1)
FB _{gain (old)} : Feedback control gain before update
σ _T : Target plate temperature variation
DNC: Manipulation amount change amount limit value
u (j): Actual operation amount (actual value of the amount of fuel to be input)
j: jth control cycle from the tip of the coil to be controlled

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