JP2760264B2 - Method and apparatus for controlling thickness of tandem rolling mill - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for controlling a thickness of a tandem rolling mill in which a plurality of rolling mills are continuously arranged, and more particularly to a method and an apparatus for controlling a thickness of a sheet with high precision.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing an outline of the most basic monitor AGC in the thickness control of a conventional tandem rolling mill. Here, a case where the number of rolling mill stands is four will be described as an example.

[0003] As shown in the figure, a conventional plate thickness control device includes a speed command device 31 for determining a speed command value of each stand.
-34, thickness gauge 5 installed on the exit side of 4 stands, thickness deviation detected by the thickness gauge (deviation between actual thickness of rolled material 6 and target thickness setting value) The distribution gains (G _{1 to} G ₃ ) 51 to 53 when distributing as the thickness correction amount, multipliers 61 to 63 for multiplying the thickness deviation and the distribution gain, the output of this multiplier and the speed command device 31 to 53 The adder 41 includes adders 41 to 43 for adding the speed command value set by the controller 34, and motor controllers 21 to 24 that control the speed of the motor using the output of the adder as a speed command.

Next, a conventional thickness control method will be described.

Assuming that the entrance side plate thickness and the exit side plate thickness of the stand 4 are H ₄ and h ₄ , respectively, and the entrance side plate speed and the exit side plate speed of the stand 4 are V _4E and V _4D , respectively, The following equation holds between the constant mass flow rules.

H ₄ × V _4E = h ₄ × V _4D (Equation 1) Here, the thickness deviation Δ on the exit side of the stand 4 by the thickness gauge.
When h ₄ is detected, modifying the thickness by the speed control of the front of the stand than the stand 4.

For example, the thickness deviation Δh ₄ is
The correction is made based on the outboard speed, that is, the inboard speed of the stand 4. In this case, _assuming that the amount of plate speed correction on the entrance side of the stand 4 is ΔV _4E , H ₄ × (V _4E + ΔV _4E ) = (h ₄ + Δh ₄ ) × V _4D (Equation 2) And (Equation 2) gives the following equation.

ΔV _4E = (Δh ₄ / h ₄ ) × V _4E (Equation 3) As described above, when the thickness deviation occurs on the exit side of the stand 4, the sheet speed on the entrance side of the stand 4, that is, the sheet speed on the exit side of the stand 4. Is corrected by (the thickness deviation / the thickness setting value).

However, in general, when a thickness deviation occurs on the exit side of the stand 4, not only the speed of the stand 3 is corrected, but the thickness deviation is distributed to each stand, and a speed correction amount corresponding to the thickness deviation is provided. Stand 1, Stand 2, Stand 3
Was corrected by giving it.

The above prior art is disclosed in JP-A-63-14 / 1988.
No. 0722 and Japanese Patent Application Laid-Open No. 1-2202309 are related.

[0011]

In the conventional plate thickness control device, the distribution gain when distributing the plate thickness deviation to each stand is a fixed value. There has been a problem that the load state becomes unbalanced, the product quality is reduced due to the occurrence of slip, and the motor driving the rolling mill is deteriorated.

The present invention has been made in view of the above problems, and has as its object to provide a method and an apparatus for controlling the thickness of a tandem rolling mill capable of maintaining a constant load balance during actual rolling. .

[0013]

The above problem is solved by monitoring the load condition during actual rolling at each rolling mill stand of a tandem rolling mill, and when a thickness deviation occurs, each load condition is determined according to the load condition at that time. This can be achieved by adjusting the distribution of the thickness correction amount to the rolling mill stand and correcting the thickness setting value in the thickness control system of the rolling mill stand.

[0014]

According to the above-mentioned means, even if the load of each rolling mill stand is large or small when a thickness deviation occurs, the distribution of the thickness correction amount is adjusted according to such a load state. This makes it possible to control the thickness of each rolling mill stand so that the load on the stand with a large load does not become excessively large, so that it is possible to continuously operate the tandem rolling mill while maintaining a constant load balance. .

[0015]

Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding components are denoted by the same reference numerals.

FIG. 1 is a block diagram showing an embodiment of a plate thickness control device of a tandem rolling mill to which the present invention is applied. This embodiment is an example of application to a monitor AGC.

FIG. 1 shows a case of a tandem rolling mill having four rolling mill stands 1 to 4, in which a rolled material 6 flows from the stand 1 to the stand 4 and is rolled. Of the rolling mill stands 1-4, the final stand 4 is provided with a speed command device 34.
The motor 14 is driven at a constant speed by the electric motor 14 whose rotation is controlled by the electric motor control device 24 based on the set speed command value. Therefore, in this embodiment, the thickness control is performed by correcting the speed of the stands 1 to 3.

The configuration of the plate thickness control device is as follows. A thickness gauge 5 is provided on the exit side of the final stand 4, and detects a deviation between the actual value of the thickness of the rolled material 6 and the target set value. The detected plate thickness deviation is calculated by gains G _{1 to} G by multipliers 61 to 63.
₃ (51 to 53) are multiplied, and the result is distributed to the 2 to 3 STD (stand) exit side thickness control system as a thickness correction amount. Here, as described later, the gains G _{1 to} G ₃ are determined based on the thickness deviation and the load state of each stand so that the load does not become unbalanced and the load on a specific stand does not become excessive. Based on the thickness deviation and the load state of each stand, the thickness correction amount distribution determining device 101 corrects the value as needed. In this embodiment, the load state is detected by the motor control devices 21 to 24, for example, by measuring the load current of the motor, and the thickness correction amount distribution determining device 101
Output to Each exit side thickness control system calculates a correction amount of the speed command based on the distributed thickness correction value, that is, the output of the multipliers 61 to 63, and corrects the speed command correction amount and the speed command device 31.
The speed commands are created by adding the speed command values determined by .about.34 by adders 41-43. The motor control devices 21 to 23 control the rotation of the motors 21 to 23 that drive the stands 1 to 3 based on the created speed command.

Next, a method of adjusting the gains G _{1 to} G ₃ by the thickness correction amount distribution determining device 101 will be described with reference to FIGS.

FIG. 2 schematically shows one example of the rolling mill stands 1 to 4 and their load states, in which the load on the stand 3 is maximum and the load on the stand 2 is minimum. FIG. 3 shows a flow of a gain adjustment method in such a load state.

First, the thickness deviation of the rolled material is detected by a thickness gauge installed on the exit side of the stand 4 (step 210).
At the same time, the load state of each rolling mill stand as shown in FIG. 2 is detected (step 220). Next, whether the detected thickness deviation is positive or negative is determined (step 230), and the gain is adjusted according to the determination result to adjust the speed correction amount (step 230).
241-243).

When the sheet thickness deviation is positive, that is, when the sheet thickness actual value is larger than the sheet thickness set value, the exit side sheet speeds of the stands 1 to 3 in front of the stand 4, and therefore the entrance side sheet speeds of the stands 2 to 4. To reduce the mass flow by reducing the thickness of the outlet side plates of the stands 2 to 4 (step 24).
1). Here, if the speed of the preceding stand is reduced in order to reduce the thickness of the exit side plate of a certain stand, the tension between these stands increases, and therefore the load of the certain stand increases. Therefore, in the load state of FIG. 2, the 2STD output side plate thickness is set so that the amount of correction of the output side plate thickness set value (in the direction of reducing the plate thickness) of the stand 2 with the minimum load and large load margin is the largest. the value of the distribution gain G ₁ of the amount of correction of the plate thickness setting value given to the control system and the largest set,
Thereby, the speed correction amount (however, the direction of decreasing the speed) of the preceding stand 1 is made maximum. Also, the correction amount of the thickness setting value given to the 3STD exit thickness control system is set so that the amount of correction of the outlet thickness setting value of the stand 3 with the maximum load (in the direction of reducing the thickness) is minimized. the value of the distribution gain G ₂ is set to the minimum, the speed correction amount of the previous stage of the stand 2 (where the direction of reducing the speed) is set to be a minimum. That is, when the actual plate thickness is larger than the target set value in the load state of FIG. 2, the gain is set to G ₁ >
By setting so that G ₃ > G ₂ , the load on the stand 3 is prevented from being further increased, and the continuous operation can be continued while maintaining the load balance of each stand.

Further, when the sheet thickness deviation is negative, that is, when the sheet thickness actual value is smaller than the sheet thickness set value, the exit side sheet speeds of the stands 1 to 3 in front of the stand 4 (stands 2 to 4)
Of the stand 2 to 4 by increasing the mass flow by increasing the inlet plate speed of the
243). In this case, if the speed of the preceding stand is increased in order to increase the thickness of the exit side plate of a certain stand, the tension between the stands is reduced, so that the load on the certain stand is reduced.
Therefore, in the load state shown in FIG. 2, a plate provided to the 3STD output side plate thickness control system is set so that the amount of correction of the output side plate thickness set value of the stand 3 where the load is the maximum (however, the direction of increasing the plate thickness) becomes the largest. the greatest set the value of the distribution gain G ₂ of the correction amount of the thickness set value, thereby speed correction amount of the stand 2 of the preceding stage (where the direction of increasing the speed) is set to be maximized. Further, the correction amount of the thickness setting value given to the 2STD output side thickness control system is set so that the correction amount of the output side thickness setting value of the stand 2 with the minimum load (in the direction of increasing the thickness) is minimized. the value of the distribution gain G ₁ is set to the minimum, the speed correction amount of the previous stage of the stand 2 (where a direction to increase the speed) is set to be a minimum. That is, when the actual thickness is smaller than the target set value in the load state shown in FIG. 2, the gain is set so that G ₂ > G ₃ > G ₁ , so that the above-described thickness deviation becomes negative. As in the case of, the continuous operation can be continued while maintaining the load balance.

If the thickness deviation is zero, the speed is not corrected (step 242).

The distribution gain is set by the method as described above. As the actual gain value, a plurality of empirically used values are stored in advance by the thickness correction amount distribution determining device, and the actual gain value is stored. An appropriate value can be selected from the above based on the above-described method, or can be obtained by using known fuzzy inference. According to the above-described method, when the load distribution of a plurality of rolling mills is set in advance, the thickness control can be performed while maintaining the set load distribution. Further, the present invention can be applied not only to the monitor AGC but also to other AGC such as mass flow AGC. In the case of mass flow AGC,
The speed of the rolling mill is controlled based on the deviation between the sheet thickness and the sheet thickness set value obtained by the mass flow calculation. The sheet thickness set value of each rolling mill is adjusted based on the load state.

[0026]

As described above, according to the present invention, there is an effect that stable continuous rolling can be performed without disturbing the load balance during actual rolling. Also, in the steady rolling state, the load balance can be monitored and the sheet thickness set value can be corrected so as to achieve the set balance, so that the motor power can always be used to the maximum in the sheet thickness control. The control limit due to the load limit during thickness control is greatly relaxed. Therefore, the product thickness accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main configuration of a sheet thickness control device to which the present invention is applied.

FIG. 2 is a schematic view showing an example of a load state in a tandem rolling period.

FIG. 3 is a flowchart showing a method for adjusting a distribution gain.

FIG. 4 is a block diagram schematically showing a conventional plate thickness control device.

[Explanation of symbols]

1-4: rolling mill stand, 5: thickness gauge, 6: rolled material, 1
1 to 14 motor, 21 to 24 motor controller, 31
... 34 ... speed command device, 41-43 ... adder, 51-5
3 Gain, 61 to 63 Multiplier, 101 Plate thickness correction amount distribution determining device

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor, Sumitaka Sato 5-2-1 Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. Omika Plant (56) References JP-A-2-92411 (JP, A) Open Sho 62-16810 (JP, A) Actual open Sho 51-65064 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) B21B 37/18-37/20

Claims (3)

(57) [Claims] 1. A method for controlling the thickness of a tandem rolling mill having a plurality of rolling mill stands, wherein a load state of each stand is monitored to generate a load state signal, and the load state signal and the rolled sheet thickness deviation signal are generated. Input, calculate and output the thickness compensation amount distribution signal to each stand,
The thickness correction amount distribution signal is input, a speed command correction amount signal is calculated and output, and the speed command correction amount signal is added to a speed command set value signal to generate a speed command signal. Control method. 2. A thickness control device for a tandem rolling mill having a plurality of rolling mill stands and an output thickness control device for controlling an output thickness of a rolling mill stand, comprising: a device for monitoring a load state of each stand; A thickness correction amount distribution determining device that receives a signal from the load condition monitoring device and a rolled material thickness deviation signal, calculates a thickness correction amount distribution signal, and outputs the result to an output side thickness control device. A thickness control device for a tandem rolling mill. 3. A thickness control device for a tandem rolling mill having a plurality of rolling mill stands and an output thickness control device for controlling an output thickness of a rolling mill stand, comprising: a device for monitoring a load state of each stand; A signal from the load condition monitoring device and a rolled sheet thickness deviation signal on the output side of the final rolling mill stand are inputted, and a distribution gain signal of the thickness correction amount is calculated by the output side thickness control device, and the result is output as described above. A thickness control device for a tandem rolling mill, comprising: a thickness correction amount distribution determining device that outputs to a side thickness control device.