JPH0780522A - Method and device for controlling plate thickness in tandem rolling mill - Google Patents

Abstract

PURPOSE:To provide a method and device for controlling plate thickness in tandem rolling mill in which a load balance is not disturbed during a rolling. CONSTITUTION:A distribution gain at the time of distributing the plate thickness deviation signal, which is detected by a plate thickness meter 5 provided on the exit side of the stand 4 of a tandem rolling mill, to each stand as a speed correction signal is decided by a device 101 for deciding the distribution of quantity for correcting plate thickness, based on the signal for the loaded state of each stand taken in by motor controlling devices 21-24. This speed correction signal is added to the speed command value of each stand, which value is the output of speed command devices 31-34, and transmitted to the motor controlling devices 21-24, controlling the rotation of motors 11-14. Consequently, a stable rolling is made possible without disturbing the load balance, and improvement is expectable in the accuracy of the plate thickness of a product.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate thickness control method and device for a tandem rolling mill in which a plurality of rolling mills are continuously arranged, and more particularly to a highly accurate plate thickness control method and device.

[0002]

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

As shown in the figure, the conventional plate thickness control device has a speed command device 31 for determining the speed command value of each stand.
~ 34, 4 thickness gauges installed on the stand out side, the thickness deviation detected by the thickness gauge (deviation between the actual thickness of the rolled material 6 and the target thickness setting value) is applied to each stand. Distribution gains (G _{1 to} G ₃ ) 51 to 53 when distributing as the thickness correction amount, multipliers 61 to 63 for multiplying the plate thickness deviation and the distribution gain, the output of this multiplier and the speed command device 31 to. It was composed of adders 41 to 43 for adding speed command values set by 34, and motor control devices 21 to 24 for controlling the speed of the motor by using the output of this adder as a speed command.

Next, a conventional plate 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 entrance side and the exit side of the stand 4 are In the meantime, the following equation holds based on the law of constant mass flow.

H ₄ × V _4E = h ₄ × V _4D (Equation 1) Here, a plate thickness deviation Δ on the stand 4 exit side by a plate thickness meter
When h ₄ is detected, the plate thickness is corrected by the speed control of the stand preceding the stand 4.

For example, this plate thickness deviation Δh ₄ is determined by the stand 3
It is corrected by the output side plate speed, that is, the stand 4 input side plate speed. In this case, if the stand 4 entry side plate speed correction amount is ΔV _4E , H ₄ × (V _4E + ΔV _4E ) = (h ₄ + Δh ₄ ) × V _4D (Equation 2) (Equation 1) according to the law of constant mass flow. And the following equation is obtained from (Equation 2).

ΔV _4E = (Δh ₄ / h ₄ ) × V _4E (Equation 3) In this way, when the thickness deviation occurs on the stand 4 outlet side, the stand 4 inlet side plate speed, that is, the stand 3 outlet side plate speed. Is corrected by (thickness deviation / thickness set value).

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

As the above-mentioned prior art, Japanese Patent Laid-Open No. 63-14
Those described in JP-A-0722 and JP-A-1-202309 are relevant.

[0011]

In the conventional plate thickness control apparatus, since the distribution gain when distributing the plate thickness deviation to each stand is a fixed value, the load of a particular stand becomes excessive, and so on. There is a problem that the load condition becomes unbalanced, the slip causes the product quality to deteriorate, and the motor for driving the rolling mill deteriorates.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a strip thickness control method and apparatus for a tandem rolling mill, which can maintain a constant load balance during actual rolling. .

[0013]

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

[0014]

According to the above means, even if there is a large or small load on each rolling mill stand when a thickness deviation occurs, the distribution of the plate thickness correction amount is adjusted according to such load condition. By doing so, it is possible to control the plate thickness of each rolling mill stand so that the load of the stand with a large load does not become excessively large, so that it is possible to continuously operate the tandem rolling mill while keeping the load balance constant. .

[0015]

Embodiments of the present invention will be described below with reference to the drawings. The same or equivalent components in each drawing are designated by the same reference numerals.

FIG. 1 is an embodiment of a plate thickness control device for a tandem rolling mill to which the present invention is applied, and shows the main configuration in a block diagram. The present embodiment is an example of application to the monitor AGC.

This drawing shows the case of a tandem rolling mill having four rolling mill stands 1 to 4, in which a rolled material 6 is rolled in the direction from the stand 1 to the stand 4. Of the rolling mill stands 1 to 4, the final stand 4 is the speed command device 34.
Is driven at a constant speed by the electric motor 14 whose rotation is controlled by the electric motor controller 24 based on the speed command value set by. Therefore, in this embodiment, the plate thickness is controlled by correcting the speed of the stands 1 to 3.

The structure of the plate thickness control device is as follows. A plate thickness gauge 5 is provided on the exit side of the final stand 4 and detects the deviation between the actual value of the plate thickness of the rolled material 6 and the target set value. The detected plate thickness deviations are gains G _{1 to} G by the multipliers 61 to 63.
₃ (51 to 53), and the result is distributed as a plate thickness correction amount to the STD (stand) delivery side plate thickness control system. Here, the gains G _{1 to} G ₃ are, as will be described later, based on the plate thickness deviation and the load state of each stand, as will be described later, so that the load does not become unbalanced and the load of a particular stand does not become excessive. It is corrected by the plate thickness correction amount distribution determining device 101 as needed based on the plate thickness deviation and the load state of each stand. In the present 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 plate thickness correction amount distribution determination device 101
Is output to. Each output side plate thickness control system calculates the correction amount of the speed command based on the distributed plate thickness correction value, that is, the outputs of the multipliers 61 to 63, and the correction amount of the speed command and the speed command device 31.
The speed command values determined by ~ 34 are added by adders 41-43 to create a speed command. The electric motor control devices 21 to 23 control the rotation of the electric motors 21 to 23 that drive the stands 1 to 3 based on the generated speed command.

Next, a method of adjusting the gains G _{1 to} G ₃ by the plate thickness correction amount distribution determining device 101 will be described with reference to FIGS. 2 and 3.

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

First, a plate thickness gauge installed on the exit side of the stand 4 detects a plate thickness deviation of the rolled material (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 judged (step 230), the gain is adjusted according to the judgment result, and the speed correction amount is adjusted (step 230).
241-243).

When the plate thickness deviation is positive, that is, when the plate thickness actual value is larger than the plate thickness set value, the output plate speeds of the stands 1 to 3 preceding the stand 4 and therefore the input plate speeds of the stands 2 to 4 are set. To reduce the mass flow by lowering the outlet plate thickness of the stands 2 to 4 (step 24
1). Here, if the speed of the stand at the preceding stage is decreased in order to reduce the outlet plate thickness of a stand, the tension between these stands increases, and thus the load of the stand increases. Therefore, in the load state of FIG. 2, the 2STD output side plate thickness is set so that the correction amount of the output side plate thickness setting value of the stand 2 with the minimum load and large load margin (however, in the direction of reducing the plate thickness) becomes the largest. Set the maximum value of the distribution gain G ₁ of the correction amount of the plate thickness setting value given to the control system,
As a result, the speed correction amount of the stand 1 in the preceding stage (however, the direction in which the speed is reduced) is maximized. In addition, the correction amount of the plate thickness setting value given to the 3STD output side plate thickness control system is set so that the correction amount of the set value of the output plate thickness of the stand 3 having the maximum load (however, in the direction of reducing the plate thickness) is minimized. The value of the distribution gain G ₂ is set to the minimum so that the speed correction amount of the stand 2 in the preceding stage (however, the direction of decreasing the speed) is minimized. That is, in the loaded state of FIG. 2, when the actual plate thickness becomes larger than the target set value, the gain G ₁ >
By setting G ₃ > G ₂ , it is possible to prevent the load on the stand 3 from becoming excessively large, and it is possible to continue the continuous operation while maintaining the load balance of each stand.

Further, when the plate thickness deviation is negative, that is, when the plate thickness actual value is smaller than the plate thickness set value, the outlet plate speeds of the stands 1 to 3 preceding the stand 4 (stands 2 to 4).
Increase the mass flow rate by increasing the inlet plate speed of the stand 2 to increase the outlet plate thickness of the stands 2 to 4 (step
243). In this case, if the speed of the stand in the preceding stage is increased to increase the exit side plate thickness of a certain stand, the tension between the stands is reduced, so that the load of the certain stand is reduced.
Therefore, in the load state of FIG. 2, the plate applied to the 3STD output side plate thickness control system so that the correction amount of the set value of the output side plate thickness of the stand 3 having the maximum load (however, in the direction of increasing the plate thickness) becomes the largest. The value of the distribution gain G ₂ of the correction amount of the thickness set value is set to the maximum so that the speed correction amount of the stand 2 at the preceding stage (however, in the direction of increasing the speed) is maximized. In addition, the correction amount of the plate thickness setting value given to the 2STD output side plate thickness control system is set so that the correction amount (however, in the direction of increasing the plate thickness) of the output side plate thickness setting value of the stand 2 with the minimum load is minimized. The value of the distribution gain G ₁ is set to the minimum so that the speed correction amount (however, the speed increasing direction) of the stand 2 in the preceding stage is minimized. That is, when the actual plate thickness becomes smaller than the target set value in the load state of FIG. 2, the gain is set so that G ₂ > G ₃ > G ₁ so that the aforementioned plate thickness deviation is negative. As in the case of, continuous operation can be continued while maintaining the load balance.

When the plate 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 previously stored in the plate thickness correction amount distribution determining device, An appropriate value can be selected from the above based on the above method, or can be obtained by using a known fuzzy reasoning. Further, according to the method described above, when the load distributions of the plurality of rolling mills are preset, it is possible to control the plate thickness 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 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, and the sheet thickness set value of each rolling mill is adjusted based on the load condition.

[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 plate thickness set value can be corrected so that the balance is as set. Therefore, it is possible to constantly use the motor power for plate thickness control. The control limit due to load limitation during thickness control is greatly relaxed. Therefore, it is possible to improve the product plate thickness accuracy.

[Brief description of drawings]

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

FIG. 2 is a schematic diagram showing an example of a load state during a tandem rolling period.

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

FIG. 4 is a block diagram showing an outline of a conventional plate thickness control device.

[Explanation of symbols]

1 to 4 ... Rolling mill stand, 5 ... Plate thickness gauge, 6 ... Rolled material, 1
1-14 ... Electric motor, 21-24 ... Electric motor control device, 31
-34 ... Speed command device, 41-43 ... Adder, 51-5
3 ... Gain, 61-63 ... Multiplier, 101 ... Plate thickness correction amount distribution determining device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sumitaka Sato 5-2-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Omika factory

Claims (3)

[Claims] 1. A strip thickness control method for a tandem rolling mill having a plurality of rolling mill stands, wherein a load state signal is generated by monitoring a load state of each stand, and the load state signal and the rolled material strip thickness deviation signal are provided. Input and output the plate thickness correction amount distribution signal to each stand,
A plate thickness characterized by inputting the plate thickness correction amount distribution signal, calculating and outputting a speed command correction amount signal, adding the speed command correction amount signal to a speed command set value signal, and generating a speed command signal. Control method. 2. A strip thickness control device for a tandem rolling mill having a plurality of rolling mill stands and an exit side strip thickness control device for performing strip stand thickness on the outgoing side strip thickness, and a device for monitoring the load condition of each stand. A plate thickness correction amount distribution determining device for inputting a signal from the load condition monitoring device and a rolled material plate thickness deviation signal, calculating a plate thickness correction amount distribution signal, and outputting the result to the output side plate thickness control device. A plate thickness control device for a tandem rolling mill, which is characterized in that 3. A strip thickness control device for a tandem rolling mill having a plurality of rolling mill stands and an exit side strip thickness control device for performing strip stand stand-out strip thickness control, and a device for monitoring a load state of each stand. Input the signal from the load condition monitoring device and the rolled material strip thickness deviation signal on the exit side of the final rolling mill stand, calculate the strip gain correction amount distribution gain signal to the exit side strip thickness control device, and output the result. A strip thickness control device for a tandem rolling mill, comprising: a strip thickness correction amount distribution determining device for outputting to a side strip thickness control device.