JPH048123B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for controlling the width of a rolled material in a rolling mill such as a hot strip mill.

[Conventional technology]

Generally, the rolling width (hereinafter referred to as plate width) W in a rolling mill is determined by adding an additional width of a certain size to a predetermined product width. This additional width is the extra width determined by taking into account cutting margins, thermal expansion margins, etc., as well as variations in width, and is the part that will eventually be discarded, so the board should keep this additional width as small as possible. It is preferable to improve the material yield by controlling the width.

Conventional strip width control methods for so-called tandem rolling mills having multiple stands of hot strip mills include the method proposed in JP-A-57-139414 and JP-A-57-58910. There is a way. In other words, the former measures the width and temperature of the strip at the entrance to the stand of the rolling mill, predicts the strip width at the exit from the final stand according to the model formula, and changes the tension between the stands based on this predicted value. This is feed-forward type control that keeps the plate width constant. However, this requires a large-scale arithmetic device to perform a large amount of complex calculations in a short time. On the other hand, the latter measures the strip width at the exit side of the final stand of the rolling mill, and changes the tension between the stands according to the deviation between this measured strip width value and a preset strip width target value to increase the strip width. This is a feedback type control that keeps the current constant, and the system is simpler than the former.

FIG. 3 is a schematic system diagram of the feedback control of strip width in this conventional rolling mill. In the figure, 1 is the final stand of the rolling mill, 2 is the upstream stand,
3 is an electric looper located between the stands 1 and 2 for controlling the tension of the strip 4 which is the material to be rolled;
is a torque motor that adjusts the torque of this looper 3. Reference numeral 6 denotes a width gauge consisting of a photodetector disposed on the exit side of the final stand 1, which measures the edge of the strip by receiving the self-emission of the high-temperature strip 4 or the light from an unillustrated light source provided below the strip 4. By this detection, the plate width W is detected.

The plate width W detected by the width gauge 6 and the plate width target value W ₀ from a plate width setter (not shown) are inputted to the comparison section 7,
The plate width deviation W−W ₀ =ΔW is determined and input into the PI control device 8. The PI control device 8 outputs a PI operation signal corresponding to the plate width deviation ΔW to the tension control device 9 as a correction value Δσ of the tension reference value σ ₀ corresponding to the width target value W ₀ . The tension control device 9 uses this tension reference correction value Δσ
Based on this, a tension control signal for controlling the torque of the looper motor 5 is output to the looper motor 5. This changes the looper torque and
As a result, the plate width W is corrected to a normal value.

[Problem that the invention seeks to solve]

However, in the above-mentioned conventional strip width control method using feedback control, the strip tension is PI-controlled via a looper according to variations in strip width. It is impossible to control the

In other words, the strip tension σ between the stands and the strip width deviation ΔW between the stands have an exponential function relationship expressed by the following equation (1). I can't.

ΔW∽σ ⁿ ...(1) Also, to compensate for this, by using PI control to reduce the proportional gain and increase the integral gain,
If an attempt is made to increase the control ability, the integral action becomes stronger, so the overshoot on the negative side (that is, closer to the product width) with respect to the width target value W ₀ becomes larger, as shown in FIG. Moreover, the final stand 1
Since the control position by the looper 4 placed on the upstream side with the two wheels in between and the detection position by the width meter 6 placed on the downstream side are different from each other, the delay time (dead time) is large.
The recovery of the control output is delayed and the overshoot is amplified.

As a result, it is necessary to set the plate width target value W ₀ that takes into account the large overshoot -ΔW.
There was a problem in that the margin increased accordingly, making it impossible to improve the yield.

This invention was made by focusing on the above-mentioned conventional problems, and instead of the method of PI controlling the strip tension via a looper according to the deviation amount of the strip width,
By providing a strip width control method that calculates the logarithm of the strip width deviation and proportionally controls the strip tension via a looper accordingly, it is possible to control overshoot and improve yield. The purpose is to

[Means for solving problems]

In order to achieve the above object, the present invention provides a rolling mill that has a plurality of stands for rolling a material to be rolled and controls the width of the material at the exit side of the final stand. The plate width is detected by a width meter, the logarithm of the deviation between the plate width detection value and a preset plate width target value is calculated, and the plate tension of the rolled material between the stands is proportionally controlled based on the calculated value. It is characterized by controlling the width to be constant.

[Effect]

In this invention, the logarithm of the deviation between the actual board width value detected by the width meter and the preset board width target value is calculated, and the correction amount of the board tension is determined based on the calculation result. By using the logarithm value of the plate width deviation as the standard for the amount of correction in this way, the relationship between the plate width deviation value and plate tension, which is expressed by an exponential function, is converted into a proportional equation, so it becomes possible to control with simple proportional control. Therefore, excessive overshoot associated with conventional integral operation does not occur.

〔Example〕

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

FIG. 1 is a system diagram showing an embodiment of the present invention. Note that in the figure, 1 to 7 are the same as the conventional one. 10 is a logarithm calculator for calculating the logarithm logΔW of the sheet width deviation amount ΔW. Reference numeral 11 denotes a proportional control device, which calculates a tension correction value Δσ for proportionally controlling the plate tension σ based on the calculated value logΔW of the logarithm calculator 10, and calculates a tension correction value Δσ for proportionally controlling the plate tension σ.
Output to. In this case, if we convert the relationship ΔW∞σ ⁿ between plate width change ΔW and plate tension σ expressed by the above equation (1) into a logarithmic expression, the proportional expression logΔW=k・nlogσ (however,
k is a proportional gain), so the logarithm calculator 1
By multiplying the input logΔW from 0 by the coefficient 1/k·n, logΔW/k·n=logσ is obtained. The tension correction command Δσ can be obtained by performing anti-logarithmic transformation on the obtained plate tension logarithm value logσ. Here, the proportional gain k needs to be varied depending on the temperature of the strip 4 to be rolled, the type of steel, etc., and is given from the host computer 12.

A tension control device 13 controls the output torque of the looper motor 5 based on the plate tension correction command value Δσ from the proportional control device 11, thereby adjusting the looper torque and correcting the tension of the strip 4.

FIG. 2 shows the results of sheet width control using the system shown in FIG. 1 (solid line) in comparison with conventional PI control (dashed line).

When the plate width W detected by the width gauge 6 is equal to the target value _W0 , the deviation signal ΔW output from the comparator 7 becomes zero, so the output of the logarithm calculator 10 also becomes zero, and the proportional control device Since the correction command value Δσ of 11 also becomes zero, a tension control signal corresponding to the tension target value is output from the tension control device 13 to the looper motor 5, and the torque of the looper motor 5 is controlled to a predetermined value.

In this state, the width W of strip 4 is set to the target value.
When the width changes from W ₀ , the width change is immediately detected by the width gauge 6 and output to the comparison section 7. Therefore, the comparator 7 calculates the deviation W−W ₀ =ΔW between the changed actual plate width W and the preset target value W ₀
The output is sent to the logarithm calculator 10 to calculate the logarithm logΔW of the deviation, and the result of the calculation is input to the proportional control device 11. This proportional control device 11 calculates the tension correction value Δσ by calculating the input deviation logarithm value logΔW based on the proportional gain k set according to the steel type, strip temperature, etc. supplied from the host computer 12. This is supplied to the tension control device 13. Therefore, in the tension control device 13, the tension control signal is changed according to the tension correction value Δσ, thereby changing the driving torque of the looper motor 5, so that the tension of the strip 4 is directed in a direction that corrects the change in the strip width W. will be corrected. That is, when the width W of the strip 4 changes in a direction larger than the target value W ₀ , the strip tension σ is increased to decrease the width W, and the width W of the strip 4 changes in the opposite direction from the target value W ₀ . When the strip tension changes in the direction of decreasing, the strip tension σ is decreased to increase the strip width W.
increase.

By controlling the width W of the strip 4 as described above, excessive overshoot can be prevented. In this case, the amount of variation in the plate width is not controlled as shown by the dotted line in Fig. 2 due to the presence of wasted time due to the relationship between the placement positions of the width gauge 6 and the tension control device, and the presence of temperature fluctuations due to skid marks. Although the amount of overshoot is slightly larger than that in the conventional example, since the integral operation as in the conventional example is not performed, the amount of overshoot is much smaller than in the conventional example. Therefore, the target plate width W ₀ can be set closer to the required product width, the surplus width can be reduced, and the material yield can be improved.

Although the above embodiment describes the case where feedback control is performed, the present invention is not limited to this. For example, a width gauge may be provided between the final stand 1 and its upstream stand 2, or further upstream of the upstream stand 2. Of course, the present invention can also be applied to the case where the width detection signal is used to perform feed forward control.

〔Effect of the invention〕

As explained above, according to the present invention, the plate width can be adjusted by proportionally controlling the plate tension based on the logarithm of the deviation between the actual plate width detected by the width meter and the preset plate width target value. Since the fluctuations are controlled, the overshoot of the control amount can be much reduced compared to the conventional PI control, and as a result, it is possible to set the margin of the board width small, which improves the yield. This has the effect of improving.

[Brief explanation of drawings]

FIG. 1 is a schematic system diagram for realizing the sheet width control method according to the present invention, FIG. 2 is a graph showing an example of the control results, and FIG. 3 is a schematic system diagram for the conventional sheet width control method. FIG. 4 is a graph showing conventional control results. 1 is the last stand, 2 is the upstream stand, 3
is a looper, 4 is a stripper, 5 is a looper motor,
6 is a width gauge, 10 is a logarithm calculator, 11 is a proportional control device, and 13 is a tension control device.

Claims (1)

[Claims] 1 It has a plurality of stands for rolling the material to be rolled,
In a rolling mill that controls the strip width at the exit side of the final stand, the width of the rolled material near the stand is detected by a width meter, and the logarithm of the deviation between the detected strip width value and a preset strip width target value is calculated. A method of controlling strip width in a rolling mill, characterized in that the strip width is controlled to be constant by calculating and proportionally controlling the strip tension of the material to be rolled between the stands based on the computed value.