JPH0724850B2 - Shape control method in multi-high rolling mill - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a shape control method in a multi-high rolling mill that automatically controls the strip shape in thin strip rolling using, for example, a 12-high or 20-high rolling mill. .

(Prior art and its problems) In a conventional 4-high rolling mill or 6-high rolling mill, since the work roll has a large diameter, the amount of deflection of the work roll is small, and the plate shape of the rolled material is a quadratic or It can be sufficiently approximated by a quartic equation. Therefore, there are few parameters indicating the quality of the plate shape, and the influence coefficient in shape control can be small. Therefore, the influence coefficient can be easily obtained by calculation or experiment (JP-A-55-4214).
(See Japanese Patent Laid-Open No. 3-42164).

However, in the multi-high rolling mill, since the work roll has a small diameter, the amount of deflection of the roll cannot be ignored, and the plate shape changes intricately in the plate width direction. It is necessary to detect the plate shape over the entire plate width direction using a shape detector composed of a sensor. Moreover, not only that, but there are many mechanisms for controlling the plate shape (taper roll shift mechanism, backup roll pushing mechanism), and they interfere with each other, so that simultaneous and proper operation is required.

In this way, when complicated deformation occurs and each control mechanism interferes with each other, it is difficult to appropriately determine the influence coefficient in the shape control, and therefore, it is necessary to quickly control the roll deformation. However, there was a problem that stable control could not be performed.

(Object of the Invention) The present invention has been made in view of the above conventional problems,
An object of the present invention is to provide a shape control method for a multi-high rolling mill that can easily correct the shape control even if there are many influence coefficients, improve the convergence of shape control, and enable stable shape control.

(Structure of the Invention) In order to achieve the above object, the present invention provides a shape detector including n sensors that detect a plate shape, a shape control drive unit that changes the plate shape, and the shape detector. In the shape control method in the multi-stage rolling mill equipped with the control device for controlling the drive means based on the signal of, the influence coefficient aij previously calculated or experimentally determined, and the initial value is appropriately determined, and then measured by the respective sensors. Input gain W that is changed based on the signal to reduce the difference from the target value
i, the output gain gi, and the virtual controlled variable increment δj is However, εlob: Measured elongation difference rate at the l-th sensor position [δj]: Vector of m rows [εlob]: Vector of n rows However, ▲ ε ^* _i ▼: Determine the output gain gj again from the shape evaluation value σ represented by the target elongation difference rate at the i-th sensor position, and calculate the control amount increment Δxj from the following equation Δxj = gj · δj. Then, the drive means is controlled based on this value, and thereafter, the calculation and control are repeated while updating the input gain Wi and the output gain gj.

(Embodiment) Next, an embodiment of the present invention will be described with reference to the drawings.

The present invention relates to a shape detector including n sensors for detecting a plate shape, a shape controlling drive means for changing the plate shape, and a control means for controlling the driving means based on a signal from the shape detector. It is applied to a multi-high rolling mill equipped with and.

First, the theoretical background of the control method according to the present invention will be described.

First, based on the signal output from the shape detector, the shape evaluation function φ for making it correspond to the value for evaluating the plate shape of the rolled material is defined as follows.

However, εi: elongation difference rate at i-th sensor position ▲ ε ^* _i ▼: target elongation difference rate at i-th sensor position Wi: input gain value at i-th sensor position n: sensor used for shape control The number (described above).

Further, the elongation difference rate εi is approximated as follows.

However, εiob: Measured elongation difference rate at the i-th sensor position aij: Effect coefficient on the elongation difference rate by the control amount of the j-th taper roll shift mechanism, backup roll pushing mechanism, etc. at the j-th sensor position (calculation or Determined by experiment) δj: jth virtual control amount increment m: number of control actuators used for shape control (described above).

By the way, when a rolled material is rolled, it is stretched in its length direction, but if the elongation is uneven at each position in the width direction of the rolled material, rolling at a certain position in the width direction (i-th position) is performed. The amount of elongation (Δ1i) in the length direction with respect to the previous initial length (1) and a reference position that can be arbitrarily determined (eg, the position with the smallest elongation in each position in the width direction, or the center in the width direction) At the position (), the difference between the initial length before rolling (1) and the amount of elongation in the length direction (Δ1 ₀ ) is calculated as the difference in elongation (Δ1i−
.DELTA.1 ₀₎ and said (differential expansion rate divided by the _{1) ((Δ1i-Δ1 0} ) This initial length before rolling the differential expansion _{/ 1 = (1i-1 0} ) /
1,1I: length of i-th rolled material after rolling at position, 1 _0: length of the rolled material after rolling in the reference position) and said, is a term widely used in the field of rolling . It should be noted that, of the positions in the width direction, the position at which the elongation is the smallest or the center position in the width direction is usually selected as the reference position. The value of the influence coefficient aij changes depending on which one is selected as the reference position, but the other equations are exactly the same.

Therefore, the virtual control amount increment δ that minimizes the shape evaluation function φ
When i (j = 1 to m) is obtained, the following equation is obtained from the condition that ∂φ / ∂δi = 0. Strictly speaking, the formula (3) is a formula for obtaining the minimum value, but since there is no general method for obtaining the minimum value, the minimum value is considered as the minimum value as the best method. It can be expressed by the following equation using a matrix.

However, [δj]: Vector of m rows [εlob]: Vector of n rows Is called a control matrix.

Next, from the virtual control amount increment δj obtained as described above, the control amount increment Δxj of the drive means by the control device is obtained.
Is introduced as follows by introducing the value of output gain gj.

Δxj = gj · δj (5) This output gain gj reflects the guideline for changing the control amount increment Δxj. Therefore, if the plate shape is poor, increase it to speed up the convergence of the shape detection signal. When the plate shape is good, it is necessary to reduce the size in order to stabilize the control.

Therefore, the shape evaluation value σ is expressed as follows, The output gain gj (σ) is represented as a function of the shape evaluation value σ, or is divided into, for example, 5 stages according to the size of the shape evaluation value σ, and the output gain g may be predetermined for each division. .

For example, when σ <σ ₀ , gj (σ) = gi ₀ σ ₀ <σ <σ ₁ gj (σ) = gi ₁ σ ₁ <σ <σ ₂ gj (σ) = gi ₂ σ ₂ < When σ <σ ₃ gj (σ) = gi _{3 When} σ ₃ <σ gj (σ) = gi _{4 where} gj ₀ ~ gj ₄ and σ ₀ ~ σ _{3 are} empirically determined constants. Can be determined as

Next, the control method according to the present invention will be described with reference to the flowchart shown in FIG.

First, in the first step (# 1), the influence coefficient aij stored in advance in the control device is read.

In the second step (# 2), the values of the input gain Wi and the output gain gj are read.

However, initially, all of the input gain Wi (i = 1 to n) and the output gain gj (j = 1 to m) are set to 1.0.

In the third step (# 3), the control matrix in the above fourth equation is calculated.

In the fourth step (# 4), the measured elongation difference rate εiob from each sensor of the shape detector is read.

In the fifth step (# 5), the virtual control amount increment δj is calculated by the above-mentioned fourth equation.

In the sixth step (# 6), the output gain gj is determined from the shape evaluation value σ shown in the sixth equation.

In the seventh step (# 7), the control amount increment Δxj
Is calculated and a control signal corresponding to this value is output to the drive means of the rolling mill to control the plate shape.

In the eighth step (# 8), the input gain Wi is corrected.

That is, only the input gain Wi for the sensor at the position where the distribution of the difference in elongation in the plate width direction is greatly different from the target value is made larger than 1.0.

Then, after that, the process returns to the second step (# 2) again, and the same control as above is repeated thereafter.

Next, FIGS. 2 and 3 (horizontal axis: rolling time t, vertical axis: shape evaluation value σ) show examples of changes in the control characteristics depending on the input gain Wi and the output gain gj.

FIG. 2 shows changes in the shape evaluation value σ depending on the rolling time by the input gain (Wi) with the output gain (gi = 1.0) being constant. From this, it is shown that adjusting the input gain improves the convergence of the shape, but causes hunting and deteriorates the stability.

Further, FIG. 3 is a diagram comparing the case where the input / output gain is fixed (solid line) and the case where the input / output gain is adjusted (broken line), and the convergence is improved by adjusting the input / output gain. Moreover, it is shown that stable control is performed.

(Effect of the Invention) As is clear from the above description, according to the present invention, the influence coefficient is corrected by the input / output gain after the influence coefficient is theoretically or experimentally determined. Even if the accuracy of the influence coefficient is difficult to determine well, adjusting the input / output gain improves the convergence of the shape detection signal and enables stable control. As a result, the influence coefficient can be easily determined. Can be converted.

Further, the number of influence coefficients is much smaller than that of the non-linear control, the time required to calculate the control amount once can be shortened, and the load on the control device can be reduced.

Furthermore, compared to non-linear control, the influence coefficient is smaller,
For each pass schedule such as the material of rolled material and plate thickness,
Even if the influence coefficient is not included, it is sufficient to include only the input / output gain for each schedule, so that the required variables are reduced and the control can be simplified.

[Brief description of drawings]

FIG. 1 is a flow chart showing the procedure of the control method according to the present invention, and FIGS. 2 and 3 are diagrams showing examples of changes in control characteristics due to input / output gain.

Claims (1)

[Claims] 1. A shape detector comprising n sensors for detecting a plate shape, a shape control driving means for changing the plate shape, and a control for controlling the driving means based on a signal from the shape detector. In the shape control method in the multi-stage rolling mill equipped with a device, the influence coefficient aij previously calculated or experimentally determined, and the initial value is appropriately set, and then the difference between the target value and the target value is reduced based on the signals measured by the sensors. Using the input gain Wi and the output gain gj that are changed to However, εlob: Measured elongation difference rate at the l-th sensor position [δj]: Vector of m rows [εlob]: Vector of n rows However, ▲ ε ^* _i ▼: Determine the output gain gj again from the shape evaluation value σ expressed by the target elongation difference ratio at the i-th sensor position, and calculate the control amount increment Δxj from the following equation Δxj = gj · δj. Then, the shape control method in the multi-high rolling mill is characterized in that the driving means is controlled on the basis of this value, and thereafter, the calculation and control are repeated while updating the input gain Wi and the output gain gj.