JPH02166235A - Method for controlling sheet temperature in metallic sheet heating furnace - Google Patents

Abstract

PURPOSE:To precisely heat a metallic sheet in a heating furnace to a desired temp. by obtaining a sheet temp. predicted value to minimize the difference from a sheet temp. command from the time sequential data related to the metallic sheet to be annealed and the heat-transfer model in the heating furnace at the time of annealing a metallic sheet in the continuous annealing furnace. CONSTITUTION:When a long-sized metallic sheet is continuously annealed in the heating furnace 1 such as a continuous annealing furnace, a sheet temp. predicted value to minimize the difference from a sheet temp. command is obtained by a sheet temp. root computing element 5 based on the time sequential data 2 storing the size, specific heat, and sheet temp. command of a metallic sheet to be heated and the physical transfer model 3 expressing the relative heat-transfer shape among the radiant tube, hearth roll, steel sheet, etc., in the heating furnace 1. The temp. of the heating furnace 1 is appropriately controlled by an adaptive controller 10 with the sheet temp. command as the set value to control the heating (annealing) of the metallic sheet with high efficiency in the heating furnace 1, hence the generation of defective steel sheets is reduced, and the yield of the annealed steel sheets is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for controlling the temperature of a grating plate in a metal plate heating furnace such as a continuous annealing furnace.

[Prior Art] Conventionally, as a method of controlling the plate temperature in a metal plate heating furnace such as a continuous annealing furnace, feedback control based on a target value of the plate temperature and an actual value, i.e., a target value of the plate temperature. A strategic control method is to perform PID control based on the magnitude, integral value, and differential value of the deviation (sv-pv) between SV and the actual value PV in the heating furnace.

Further, when future data such as change time and variation amount of the target plate temperature value is known, feedforward control is also applied in addition to the feedback control described above, taking into account the slow response of the heating furnace.

[Problem to be solved by the invention]

However, in conventional feedforward control, the change time and variation amount of the target value or control output (fuel supplied to the heating furnace, etc.) are expressed using tables or mathematical formulas, but they are Since it is difficult to create tables and formulas, it is difficult to always minimize the difference between the target value and the measured value of plate temperature.

Furthermore, even if it is possible to set a plate temperature change route that minimizes the difference between the target value and the actual value of plate temperature, the time constant of the heating furnace is large, and parameter tuning of PID control is difficult. It is extremely difficult to perform parameter tuning, and since parameter tuning is performed by humans while monitoring the operating status of the heating furnace, it is extremely rare to achieve optimal control under all conditions.

For this reason, it has been extremely difficult to improve control accuracy when PID control is used for feedbank control.

The present invention has been made in view of the technical problems in the prior art, and an object of the present invention is to provide a control method that can improve the accuracy of plate temperature control in a heating furnace.

[Means to solve the problem]

In order to achieve the above object, the present invention provides time-series data such as the dimensions of a metal plate heated in a heating furnace and target plate temperature values,
Based on a heat transfer model expressing the heat transfer form of the heating furnace, a predicted plate temperature value that minimizes the difference from the target plate temperature value is obtained in advance, and attention is paid only to the response of the heating furnace. The heating furnace is controlled by an adaptive control system having a mathematical model such that the plate temperature in the heating furnace becomes equal to the predicted plate temperature value.

[Effect]

Time-series data on the conditions of the metal plate heated in the heating furnace (metal plate dimensions, specific heat, plate temperature target value, etc.) and a heat transfer model (physical model) that expresses the heat transfer form of the heating furnace. Based on this, a predicted plate temperature value that minimizes the difference from the target plate temperature value is calculated, and mathematics that focuses only on the response of the heating furnace is used to match the predicted plate temperature value to the actual plate temperature in the heating furnace. Input (supply fuel) to the furnace by an adaptive control system with a model.

(line speed of metal plate, etc.) is controlled.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

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

First, to explain the configuration, in FIG. 1, time series data 2 in which dimensions, specific heat, plate temperature target values, etc. of a metal plate to be heated in the future in a heating furnace 1 such as a continuous annealing furnace are stored;
A plate temperature target ( 11! Predicted plate temperature value (plate temperature Roux) that minimizes the difference from T's
There is a plate temperature route calculator 5 that calculates the temperature.

In this example, a function J shown in equation (1) below was used as an evaluation function indicating the magnitude of the difference between the target value of plate temperature and the root. However, in order to avoid insufficient firing of the metal plate, To
A constraint condition of s(t)≦Ti5(t) was set.

J-=lXN(Tos(t)-T, 1s(t))2at
- (1) Then, there is an adaptive control device 10 as an adaptive control system that controls the heating furnace 1 using the plate temperature TR5 determined by the plate temperature route calculator 5 as a set value. .

This adaptive control device 10 focuses only on the response between the input and output to the heating furnace 1, and uses a mathematical model 11 representing the dynamic characteristics of the heating furnace 1, and this mathematical model 11 using actual human output. a state estimator 13 that estimates a state quantity (having no physical meaning) representing the internal state of the heating furnace 1 represented by the mathematical model 11 from the actual input/output; A controller 14 is provided to appropriately control the flow rate of fuel supplied to the heating furnace 1 in consideration of the dynamic characteristics of the heating furnace 1 based on the state quantity.

The heating furnace 1 is also provided with a measuring device 15 for measuring the dimensions of the actual metal plate and a plate thermometer 16 for measuring the actual plate temperature. The output is from the identifier 12. It is supplied to a state estimator 13 and a controller 14.

In this example, the following models [2] and (3) No. 6 were used as the mathematical model 11.

z(t+Δt)=A:z(t)+Bu(t)
--(2) y(t+Δt)=Cz(t+Δt)
(3) However, y(t) is the plate temperature on the exit side of the heating furnace 1, and is. (LS is the line speed of the metal plate, D is the plate thickness, W is the plate width, and ■ is the fuel flow rate.

) Furthermore, in this embodiment, the least squares method was applied to the identifier 12, the Kalman filter was applied to the state estimator 13, and the finite settling control method was applied to the controller 14.

Next, the operation of the above embodiment will be explained.

Now, in the heating furnace 1, three types of coils C,...
C2 and C3 are to be heated, and these coils C+,
The plate temperature target values for each of Cz and C3 are T o 1+
TO! and T. 3.

That is, as shown in FIG. 2, in the heating furnace 1, the coils C1 to C
3 is heated continuously. Therefore, the plate temperature target value T for each coil. Based on time series data 2 such as l + T (12 and T., dimensions of each coil, etc.) and heat transfer model 3,
When the optimum plate temperature route TR5(t) is determined using the evaluation function J of formula (1) in the plate temperature route calculator 5, it becomes as shown by the solid line in FIG.

In other words, when determining the plate temperature (R)TRs(U), the relationship between the plate temperature target value (T O2 < T o + < T O
3) is taken into account (if the temperature is lowered too much when heating coil C2, the temperature will not rise in time when moving to coil C3), so the plate temperature route T □ ( 1) is the target value T. It is set so that it does not fall below 3.

Then, the adaptive control device 10 performs control using the obtained plate temperature route T*5(t) as a set value.

That is, the plate temperature (L)Ta2(t) is adjusted by the controller 1 at each elapsed time.
4, the actual dimensions and plate temperature of the metal plate are supplied from the measuring device 15 and the plate thermometer 16 to the identifier 12, the state estimator 13, and the controller 14. The identifier 12 tunes the mathematical model 11 by uncovering the supplied actual dimensions and plate temperatures, and the mathematical model 11 tunes the state estimator 1.
3 and the controller 14, and the state estimator 13 estimates the state quantity representing the internal state of the heating furnace 1 represented by the mathematical model 11 from the supplied actual dimensions and plate temperature. is supplied to the controller 14.

Then, the controller 14 appropriately considers each supplied value, determines an appropriate fuel flow rate, and controls the heating furnace 1.

Then, the actual plate temperature of the metal plate approximately corresponds to the plate temperature route Ti5(t), as shown by the chain line in FIG.

Moreover, since the actual plate temperature does not fall below the actual plate temperature target value in any of the coils C1 to C1 having different plate temperature target values, undercooking does not occur.

In this way, in the above embodiment to which the present invention is applied,
Control accuracy is improved, the risk of undercooking is eliminated, and the incidence of defective products can be reduced.

As a comparative example, the same coils C and -C as in FIG. 2 are used.

FIG. 3 shows the results of plate temperature control using conventional feedback control and feedforward control.

In this conventional control, in order to perform feedback control based on the deviation between the plate temperature target value (dashed line) and the actual plate temperature (dashed line), and to compensate for the slow response of the heating furnace 1, the coil C2 is switched to the coil C4. Feedforward control is performed to raise the temperature before coil C2, but since the temperature has dropped too much in the process of coil C2, it is not possible to raise the temperature sufficiently when moving to coil C3. As a result, the coil C4 becomes undercooked.

〔Effect of the invention〕

As explained above, according to the present invention, based on time-series data such as the dimensions of the metal plate heated in the heating furnace and the plate temperature target value, and a heat transfer model expressing the heat transfer form of the heating furnace, , the plate temperature prediction value that minimizes the difference from the plate temperature target value is determined in advance, and an adaptive control system with a mathematical model that focuses only on the response of the heating furnace is used to predict the plate temperature in the heating furnace. Since the heating furnace was controlled to be equal to the value,
The control accuracy for the heating furnace can be improved, and as a result, the effect of reducing the incidence of defective products can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of an embodiment of the present invention, Fig. 2 is a graph showing changes in plate temperature when three types of coils are heated in this embodiment, and Fig. 3 is a conventional control method. 2 is a graph showing changes in plate temperature when the same three types of coils as in FIG. 2 are heated. ■...Heating furnace, 2...Time series data, 3...Heat transfer model, 5...Plate temperature route calculator, 10...Adaptive control device (adaptive control system), 11... Mathematical model, 12.
...Identifier, 13...State estimator, 14...Controller, 15...Dimension measuring device, 16...Plate thermometer.

Claims (1)

[Claims] (1) Based on time-series data such as the dimensions and plate temperature target value of the metal plate heated in the heating furnace, and a heat transfer model that expresses the heat transfer form of the heating furnace, the plate temperature target value is calculated. A predicted plate temperature value with which the difference is minimized is determined in advance, and an adaptive control system having a mathematical model that focuses only on the response of the heating furnace is used to make the plate temperature in the heating furnace equal to the predicted plate temperature value. 1. A method for controlling a plate temperature in a metal plate heating furnace, characterized in that the heating furnace is controlled so as to