KR0158580B1 - Thickness Prediction Method of Cold Rolled Steel Sheet - Google Patents

Abstract

The present invention relates to a method for estimating the thickness of a cold rolled steel sheet in a cold rolling process, and more accurately predicts the thickness of a cold rolled steel sheet by a thickness control system model that can consider the feedback effect due to the rear tension of the first stand. We want to provide a way to do that, and that's the purpose.

The present invention relates to a method for predicting the thickness of a cold rolled steel sheet, in which a conventional thickness control system model for each rolling mill is configured for a winding machine, and then system matrix and control are performed in a state in which the parameters related to the roll gap mode are removed from the thickness control system. Obtaining a matrix and a disturbance matrix; The thickness control system considering the rear tension of each rolling mill by substituting the system matrix, the control matrix and the disturbance matrix obtained from the thickness control system model for the winder as described above into the system matrix term of the thickness control system model formula for the rolling mill. Obtaining a model equation; Setting a speed and a roll gap initially by a normal setup model based on the input performance data; Obtaining the coefficient of influence on the rolling conditions by linearizing the initial set as described above with respect to the speed and the roll gap; And calculating the plate thickness and tension by substituting the influence coefficient obtained as described above into a thickness control system model formula considering rear tension.

Description

Thickness Prediction Method of Cold Rolled Steel Sheet

1 is a conceptual diagram showing the relationship between the strip thickness control device of the strip, the object to be controlled and the disturbance in continuous cold rolling.

2 is a graph showing the deviation of the plate thickness and the front tension predicted according to the present invention and the conventional method.

* Explanation of symbols for main parts of the drawings

1: winder 2: stand No.1

3: 2nd stand

The present invention relates to a method for estimating the thickness of a cold rolled steel sheet (hereinafter also referred to as a cold rolled steel sheet) in a cold rolling process, and more specifically, a thickness control system model configured through a roll gap, a roll speed, and a tension mode. It relates to a method of predicting the thickness of the cold rolled steel sheet using.

Usually, in the automated cold rolling process, the rolling operation is controlled by a computer, and a control model is required to actually drive these process control computers.

The control model is known to produce the desired product. The thickness control system model consists of several theoretical formulas that dynamically modulate the physical phenomena of the cold rolling process. It is an important model.

The thickness control system model described above is usually expressed in the form of a differential equation of the matrix through the roll gap, the roll speed, and the front tension of the rolling parameters.

In the above formulas (1a) and (1b), the subscript _i represents the _i- th stand, _{i + 1} represents the influence of the _{i +} 1th stand on the _i- th stand, and A is a system matrix according to the state variable vector X. , B is a control matrix according to the control variable vector U, E represents a disturbance matrix according to the disturbance variable vector W.

And C and F are output matrices according to state and disturbance variables, respectively.

These matrices are values determined from the rolling mill's specifications and dynamic characteristics. The integration of the thickness control system models (1a) and (1b) over time is used to determine the change of state variables during rolling, especially the exit thickness and tension, in the time domain. Dynamically predictable.

The thickness control model of the type (1a) and (1b) is based on a multivariable control theory and is the most commonly used for mass flow plate thickness control (MASS FLOW AGC) and optimum control.

Therefore, the thickness quality depends on how accurately the thickness and tension are predicted by the thickness control model.

On the other hand, A _i-1 of the formula (1a) is a system matrix indicating the effect of the _i-1 th stand on the _i th stand is configured as follows.

In a conventional method, the term A _i-1 exists only in stands # 2-5 and becomes 0 (Zero) in stand # 1. That is, since the rear tension of the first stand is not included as a state variable, there is a problem in that the influence thereof cannot be predicted.

Therefore, the use of a formula capable of predicting the influence due to the rear tension of stand No. 1 has been required in estimating plate thickness and inter-stand tension during rolling.

Accordingly, the present inventors conducted a study and experiment on the thickness control system model considering the influence of the rear tension of the first stand, and proposed the present invention based on the results, the present invention is a coiler By constructing the control model through the roll gap, the roll speed and the tension mode in the same way as the rolling mill, and removing the variables related to the roll gap mode from the control model, the feedback effect by the rear tension of the stand 1 The purpose of the present invention is to provide a method for more accurately predicting the thickness of a cold rolled steel sheet by considering a thickness control system model.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

The present invention provides a method for predicting the thickness of a cold rolled steel sheet,

Constructing a thickness control system model for each rolling mill through a roll gap, a roll speed and a tension as in the following formulas (1a) and (1b);

After the thickness control system model is configured for the winding machine, the system matrices A ' _i-1 , A' _i and A ' _{i + 1} ) and the control matrix ( B ′ _i ) and disturbance matrix E ′ _i , E _{i + 1} ;

As described above, the system matrices A ' _i-1 , A' _i and A ' _{i + 1} obtained from the thickness control system model for the winder, the control matrix B' _i and the disturbance matrix E ' _i , E _{i + 1} ) substituting the system matrix, the control matrix and the disturbance matrix term of the thickness control system model formula (1a) for the rolling mill to obtain a thickness control system model formula (1a ') considering the tension of the winding machine;

Inputting performance data on the cold rolled coil and the rolling mill;

Setting an initial roll speed and a roll gap by a normal setup model based on the historical data;

Calculating the coefficient of influence on the rolling conditions by linearizing the initial roll speed and the roll gap set as described above;

And calculating the plate thickness and tension by substituting the influence coefficients obtained as described above into the thickness control system model formulas (1a ') and (1b).

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

As shown in FIG. 1, the thickness disturbance in the continuous cold rolling mill basically causes a change in the rear tension, which affects the front tension and the exit thickness. On the contrary, when the effects of the disturbance and the reduction are passed through the first stand 2, the front tension and the exit thickness dh ₁ are affected, which affects the rear tension dtb ₁ . It is a physical mechanism that changes the plate thickness by changing the front tension by the influence on the rear tension again.

At this time, in particular, if the rear tension for the first stand (2) is ignored, the exit thickness deviation and the front tension fluctuation caused by the aforementioned feedback effect cannot be predicted. That is, since the roll gap dS ₁ , the roll speed dVr ₁ , and the front tension dtf _{1 of the} stand are state variables, the influence of the rear tension may not be considered at all in the case of the stand 1.

In FIG. 1, reference numeral 1 denotes a winding machine, 3 denotes a stand No. 2, dH, dk, and dSr denote a side thickness, deformation resistance, and roll eccentricity, respectively, and dS ₂ , dVr ₂ , dtf ₂ , dh ₂ represents roll spacing, roll speed, forward tension and exit thickness for stand # 2, respectively.

Therefore, the present invention is described as a method for estimating the thickness of the cold rolled steel sheet in consideration of the influence of the rear tension of the first stand.

In order to predict the thickness of the cold rolled steel sheet according to the present invention, first, a thickness control system model through a roll gap, a roll speed, and a tension is configured for each rolling mill as in the following formulas (1a) and (1b).

The thickness control system model is common practice in the art.

Next, the thickness control system model is configured for the winding machine, and then the system matrices A ' _i-1 , A' _i and A ' _{i + 1} are removed with the variables related to the roll gap mode among the thickness control system models. It obtains the control matrix (B _'i) and the disturbance matrix _{(E' i, E 'i} + 1).

The system matrix, the control matrix and the disturbance matrix can be obtained as follows when i = 0 (winder).

The system matrices A ' _i-1 , A' _i and A ' _{i + 1} obtained above, the control matrix B' _i and the disturbance matrices E ' _i , E _{i + 1} represent a preferred example.

Next, the system matrix A ' _i-1 , A' _i and A ' _{i + 1} obtained as described above, the control matrix B' _i and the disturbance matrix E ' _i , E _{i + 1} are described. Substituting the system matrix, control matrix and disturbance matrix term of the thickness control system model formula (1a) for the rolling mill, the thickness control system model formula (1a ') considering the tension of the winding machine is obtained.

Next, performance data about a cold rolling coil and a rolling mill are input.

Next, the initial roll speed and roll gap are set by a normal setup model based on the entered performance data.

At this time, it is preferable to use a roll load formula and an advanced rate formula.

Next, from the nonlinear rolling theory, the linearization is performed through the partial derivative and the coefficient of influence for each rolling variable is calculated.

Next, the plate thickness prediction method of the present invention is completed by substituting the influence coefficients obtained as described above into the thickness control system model formulas (1a ') and (1b) to calculate the plate thickness and tension.

Hereinafter, the present invention will be described in more detail with reference to Examples.

EXAMPLE

Using the actual rolling conditions of Table 1 below, the thickness of the cold rolled steel sheet was predicted according to the present invention, and the results are shown in FIG.

In FIG. 2, the results predicted for five stands are shown. In FIG. 2, (a) shows the deviation of the thickness of the exit plate and (b) shows the deviation of the front tension.

2 shows the values predicted by the conventional method.

As shown in (a) of FIG. 2, it can be seen that the method of the present invention is improved by about 17% in the variation in the thickness of the second stand plate compared to the conventional method.

On the other hand, in the case of the front tension as shown in (b) of Figure 2, it can be seen that the present invention is improved by about 90% in the case of the first stand, 26% in the case of the second stand compared to the conventional method.

As described above, in the cold rolling method, the thickness of the cold rolled steel sheet may be more accurately predicted by considering the rear tension of the first stand when the thickness of the cold rolled steel sheet is predicted.

Claims (1)

A method for estimating the thickness of a cold rolled steel sheet, comprising: constructing a thickness control system model for each rolling mill through a roll gap, a roll speed, and a tension as in the following formulas (1a) and (1b); After the thickness control system model is configured for the winding machine, the system matrices A'i-1, A'i and A'i + 1 and control matrix Obtaining B'i) and disturbance matrices (E'i, E'i + 1); As described above, the system matrices A'i-1, A'i and A'i + 1, the control matrix B 'and the disturbance matrix E'i, Ei + 1 obtained from the thickness control system model for the winder Obtaining a thickness control system model (1a ') considering the tension of the winding machine by substituting the system matrix, the control matrix, and the disturbance matrix term of the thickness control system model formula (1a) for the rolling mill as described above; Inputting performance data on the cold rolled coil and the rolling mill; Setting an initial roll speed and a roll gap by a normal setup model based on the historical data; Calculating the coefficient of influence on the rolling conditions by linearizing the initial roll speed and the roll gap set as described above; And calculating the plate thickness and tension by substituting the influence coefficients obtained as described above into the thickness control system model equations (1a ') and (1b).