JP3501982B2 - Sheet width control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strip width control device, and more specifically, it is measured on the exit side of a certain rolling stand of a hot continuous rolling mill for rolling a material to be rolled using a plurality of rolling stands. A strip width controller for calculating a tension command value by a proportional integrator so as to eliminate the strip width deviation between the measured strip width and the target strip width, and operating the entry side tension of the rolling stand based on the tension command value. It is about.

[0002]

2. Description of the Related Art In a hot continuous rolling mill for rolling a material to be rolled using a plurality of rolling stands, there has been conventionally known a method of using an edger to control the strip width of the material to be rolled ( For example, see Japanese Patent Publication No. 6-18653 and Japanese Patent Publication No. 6-36928). However,
Since there is a limit to the control accuracy in the plate width control by the edger, a technique for feeding back the plate width and actively controlling the tension between the rolling stands has also been proposed, for example, Japanese Patent Laid-Open No. 9-155421. Gazette and Japanese Patent Laid-Open No. 9-
It is disclosed in Japanese Patent No. 155422. JP-A-9-
In the technique described in Japanese Patent No. 155421, the strip width of the material to be rolled is detected by a strip width meter installed on the exit side of a certain intermediate stand, and the deviation between the strip width detection value of the strip width meter and the target strip width is calculated. Based on this, the proportional-plus-integral control amount is calculated. Basically, this proportional-plus-integral control amount is used as a control command value, but when the deviation is positive and less than a predetermined value, the previous control amount and a predetermined set value are set to prevent overshoot on the product width side. The alternative control amount calculated on the basis of is used as a control command value. Then, the entrance side tension of the rolling stand is controlled by the control command value. In addition, JP-A-9
The technique described in Japanese Patent No. 155422 similarly detects the strip width of a material to be rolled by a strip width meter installed on the exit side of a certain rolling stand, and detects the strip width detected by the strip width meter and the target strip width. The entrance side tension of the rolling stand is controlled based on the deviation of the rolling stand. The strip width deviation ΔW, the entrance side tension σ, and the inter-stand transfer time Δt are used to obtain the tension change amount ΔσFBK. A tension change command value is calculated by a proportional integrator based on the tension change amount ΔσFBK.

[0003]

[Means for Solving the Problems] Japanese Patent Laid-Open No. 9-155421
In the technique described in Japanese Patent Publication, the measured plate width actually measured on the outlet side of a certain intermediate stand is fed back to perform proportional-integral control, and the plate width control range is widened to ensure control responsiveness. However, since there is still a dead time corresponding to the rolling speed, a low control gain must be used to ensure the stability of the control system, and there is a limit to improving the responsiveness. is there. In addition, the control gain must be determined by trial and error, and enormous effort is required for tuning and maintenance. In addition, JP-A-9-155
In the technique described in Japanese Patent No. 422, the tension command value is determined based on the transfer time between the stands, so that, for example, compared with the technique described in Japanese Patent Laid-Open No. 9-155421,
It is possible to set a higher control gain, but the effect of the transfer time on the measured strip width is complicated, and some loss of control performance is unavoidable. In addition, setting the control gain also requires trial and error, which requires a great deal of effort for tuning and maintenance. Further, the conventional techniques relating to strip width control as described in both the above publications cannot compensate for stability when conditions such as strip thickness, rolling speed, strip temperature change. In order to solve the above problems in the conventional technique, the present invention improves the plate width control device and uses a mathematical model that represents the characteristics from the tension command value to the actually measured plate width to determine the plate width deviation. A predictor that calculates a predicted value online and corrects the control input of the proportional integrator based on the predicted value, and stability of the control system based on the prediction accuracy of the predicted value calculated by the predictor By providing a gain adjusting unit that adjusts the gain of the proportional integrator so as to compensate, there is a dead time from when the entrance side tension of a rolling stand is operated until it is reflected in the measured strip width. Even in such a case, it is an object of the present invention to provide a strip width control device that can automatically obtain a control gain that realizes high responsiveness while compensating for stability without trial and error. Another purpose is to compensate the stability of the control system by adjusting the control gain according to the changes in the set operating conditions such as strip thickness, rolling speed, strip temperature, etc. .

[0004]

In order to achieve the above object, the invention according to claim 1 provides a rolling stand of a hot continuous rolling mill for rolling a material to be rolled using a plurality of rolling stands. Side, the tension command value is calculated by a proportional integrator so as to eliminate the plate width deviation between the measured plate width and the target plate width, and the entry side tension of the rolling stand is operated based on the tension command value. In a strip width control device, a predicted value of the strip width deviation is calculated online using a mathematical model expressing the characteristics from the tension command value to the measured strip width, and the proportional integrator of the proportional integrator is calculated based on the predicted value. A prediction unit that corrects the control input, and a gain adjustment unit that adjusts the gain of the proportional integrator so as to compensate the stability of the control system based on the prediction accuracy of the predicted value calculated by the prediction unit Characterized by And it is configured as a plate width controller. The gist of the invention according to claim 2 is that in the plate width control device according to claim 1, the mathematical model includes a dead time element. The invention according to claim 3 is the plate width control device according to claim 1 or 2, wherein the gain adjusting unit includes at least a plate thickness, a rolling speed, a plate temperature, or a combination thereof. The gist is that the gain of the proportional integrator is changed during rolling based on the conditions. According to the plate width control device of any one of claims 1 to 3, the predicted value of the plate width deviation is online by using a mathematical model that represents the characteristics from the tension command value to the actually measured plate width. To correct the control input of the proportional integrator based on the prediction value, and to compensate the stability of the control system based on the prediction accuracy of the prediction value calculated by the prediction unit. By including a gain adjusting unit that adjusts the gain of the proportional integrator, even when there is a dead time from when the entrance tension of a rolling stand is operated to when it is reflected in the measured strip width, It is possible to automatically obtain a control gain that achieves high responsiveness while compensating for stability without trial and error. Moreover, according to the strip width control device of the third aspect, even when the set operating conditions such as strip thickness, rolling speed, strip temperature and the like are changed, the gain of the proportional integrator is changed according to the change. Since it is changed during rolling, the stability of the control system can be maintained.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention.
The following embodiments are specific examples of the present invention, and are not of the nature to limit the technical scope of the present invention. 1 is a control block diagram showing a schematic configuration of a strip width control device A1 according to an embodiment of the present invention, and FIG. 2 is a diagram showing a relation between the strip width control device A1 and a hot continuous rolling mill. . As shown in FIGS. 1 and 2, the strip width control device A1 according to the embodiment of the present invention is, for example, a plurality of rolling stands #.
1, # 2, the continuous hot rolling machine for rolling a material being rolled using ..., certain rolling stand # sheet width between the measured actual measurement strip width W _sen and the target plate width W _ref at 2 outgoing side a proportional integrator 1 to eliminate the deviation ΔW calculate the tension command value .DELTA..sigma _ref, is embodied as a plate width controller for operating the inlet side tension of the rolling stand # 2 based on the tension command value .DELTA..sigma _ref . The feature of the plate width control device A1 is that
The predicted values ΔWp1 and ΔWp2 of the plate width deviation ΔW are calculated online using a mathematical model that represents the characteristics from the tension command value Δσ _ref to the measured plate width W _sen , and based on the predicted values ΔWp1 and ΔWp2. Prediction unit 2 that corrects the plate width deviation ΔW, which is the control input of the proportional integrator 1.
And a gain adjusting unit 3 that adjusts the gains Kp and Ki of the proportional integrator 1 so as to compensate the stability of the control system based on the prediction accuracy Δ (s) of the predicted value calculated by the predicting unit 2. It is a point which comprises and.

The details of the plate width control device A1 will be described below. The plate width controller A1 is rolling stands, for example, by feeding back the detected actual plate width W _sen by rolling stand # strip width detector 101 installed in the second outlet side in, based on the measured strip width W _sen Tension command value Δσ
_Ref is determined for each control cycle, and the roll speed of one of the rolling stands # 1 and # 2 is adjusted to adjust the entrance tension of the rolling stand # 2 according to the tension command value Δσ _ref . In the above feedback system, the measured width W
_In order to eliminate the deviation ΔW between the _sen and the target plate width W _ref , the proportional integrator 1 (proportional gain Kp, integral gain K
i) is provided. However, the control target of the feedback system is the dead time L depending on the rolling speed.
Is included, and in order to stabilize the system by adjusting the proportional gain Kp and the integral gain Ki of the proportional integrator 1, the proportional gain Kp and the integral gain Ki must be set small, and high response is obtained. It is not possible. Now, it is assumed that the actual characteristics from the tension command value Δσ _ref to the measured plate width W _sen detected by the detector 101 can be described by the following equation (1).

[Equation 1] Here, ΔW represents the deviation of the plate width, Δσ represents the tension deviation, and D represents the width change due to factors other than the tension fluctuation. The transfer function G (s) is a function such as rolling speed, strip temperature, strip thickness, rolling load, strip width absolute value, deformation resistance of the material to be rolled, and absolute tension value between rolling stands. The above formula (1) is
It is a model that represents a true process, and in general, there is no model that faithfully reproduces the above equation (1).

Therefore, the predicting unit 2 uses the nominal model, which is generally known to be suitable for the true process represented by the above equation (1), as the control model to measure the actual plate width. while predictive control for W _sen, suppressing the influence of the actual output appearing after the dead time L has elapsed in the feedback loop of the measured strip width W _sen. For the nominal model, for example, the following equation (2) is used.

[Equation 2] Here, Gm (s) is a nominal model corresponding to the transfer function G (s), but the dead time L and the tension deviation Δσ
Can be measured strictly. Although a linear model is used in the equation (2), a non-linear model may be used in practice, and it is desirable that the equation (1) can be reproduced as faithfully as possible. If the predicted plate width ΔWp1 including the dead time and the predicted plate width ΔWp2 that does not include the dead time are obtained with respect to the above formula (2), the predicting unit 2 is calculated by the following formula (3),
It can be designed as in (4).

[Equation 3]

[Equation 4] Therefore, the configuration of the control system including the proportional integrator 1 and the predictor 2 is as shown in the control block diagram of FIG. In the predicting unit 2, the inner loop (the loop of the predicted plate width ΔWp2) performs the predictive control regarding the measured plate width W _sen . Also, the outer loop (loop with predicted plate width ΔWp1)
As a result, the influence of the actual output that appears after the dead time L has elapsed in the feedback loop of the measured strip width W _sen is eliminated.

Using the plate width deviation ΔW and the calculation results of the above equations (3) and (4), the tension command value Δσ is calculated by the following equation (5).
_ref is calculated.

[Equation 5] Further, the above equation (5) can be converted into the following equation (6) using the above equations (1) and (2).

[Equation 6] If Gm (s) and G (s) and D and Dm are completely equal, the above equation (6) is the model output Δ that does not include the dead time.
It can be interpreted as a control system for controlling Wp2 to the target value 0 (see FIG. 3). In that case, the proportional gain Kp,
The integral gain Ki may be adjusted for Gm (s) that does not include dead time. When the proportional-plus-integral control is performed on Gm (s) that does not include the dead time, the proportional gain Ki and the integral gain Kp can be made larger than when the dead time is included, and the control system has a high response. Gm (s) = G (s),
The assumption that D = Dm is unrealistic, and even if some difference actually occurs between the two, the prediction unit 2
By using, for a control system including dead time,
The responsiveness can be increased by an amount corresponding to the small difference. Here, if the difference (prediction accuracy) between the true model and the control model is represented by Δ (s) in the following equation (7) (see FIG. 4),

[Equation 7] The control system can be interpreted as a product of the multiplicative error Δ (s) / Gm (s) on the controlled object Gm (s), as shown in FIG.

Therefore, the proportional gain Kp of the proportional integrator 1,
If the integral gain Ki is determined so as to always stabilize the nominal model Gm (s) in the presence of a modeling error of Δ (s) / Gm (s), a stable response of the control system is ensured and a high response is obtained. Can be realized. Gain adjuster 3
Is for this purpose, and the proportional gain Kp and the integral gain Ki are adjusted so as to compensate the stability of the control system based on the prediction accuracy of the prediction unit 2, that is, the difference Δ (s).
Regarding the set operating conditions that are determined by the strip thickness, rolling speed, strip temperature, etc., for some cases, the upper limit of the above multiplicative error Δ (s) / Gm of the control model is identified off-line using the ordinary identification method. Keep it. For example, the identification can be performed by obtaining the difference Δ (s) from the difference between the spectrum analysis of the true process and the frequency characteristic of the nominal model. This is to ensure stability even if the actual set operating conditions change during operation. In addition, of the above set operating conditions,
For a plurality of different cases, the above-mentioned multiplicative error Δ (s) / G is calculated by using the estimated plate thickness, the measured rolling speed, and the estimated plate temperature beforehand.
m is tabulated (function may be used). This is to flexibly respond to changes in set operating conditions at the time of operation and maintain high responsiveness. Multiplicative error Δ
Robust stabilization of the PI controller for (s) / Gm is
Established as robust PI control (Saiki: PID control system design method for H∞ control problem, system / control / information, Vo
l.42, No1, pp.29-34, 1998). By using this method, the applicable range of proportional gain Kp and integral gain Ki can be automatically obtained as shown in FIG. You can Here, FIG. 6A shows the setting range of each gain Kp, Ki in the first half of rolling where the rolling speed is slow, and FIG.
The setting ranges of the gains Kp and Ki in the latter half of rolling at a high rolling speed are shown. Comparing FIG. 6A and FIG. 6B, it can be understood that the gain can be set larger because the rolling speed is faster and the dead time is shorter in the latter half of rolling.

Before the rolling, the gain adjusting section 3 judges the set operating conditions by using the information of the temperature distribution of the material to be rolled, the rolling speed command value, and the strip thickness distribution, and determines each set as shown in FIG. The gain Kp and Ki setting ranges and their changes are automatically calculated, points within the setting ranges are selected, and the gains Kp and Ki are set.
Determine. In the control system according to this embodiment, as shown in FIG.
By selecting a point in the lower left direction in the setting range of, approximately higher gains Kp and Ki can be obtained. For example, the center of gravity is selected by approximating the setting range into a triangle and each gain Kp, Ki A point obtained by multiplying the maximum settable value of Ki by a predetermined coefficient between 0 and 1 may be selected. The gains Kp and Ki determined by the gain adjusting unit 3 are sent to the proportional integrator 1 during rolling, and the proportional gain Kp and the integral gain Ki are adjusted. Simulation results of the plate width control device A1 according to this embodiment and a conventional technique based on PI control are shown in FIGS. 7 (a) and 7 (b), respectively. 7 (a),
The vertical axis of (b) is plate width, and the horizontal axis is time. As shown in FIG. 7, the response time was improved by about 40% without destabilization in the presence of rolling speed, strip temperature and strip thickness fluctuations. Thus, according to the plate width control device according to the embodiment of the present invention,
A prediction unit that calculates a predicted value of the plate width deviation online using a mathematical model that represents the characteristics from the tension command value to the measured plate width, and corrects the control input of the proportional integrator based on the predicted value. And a gain adjusting unit that adjusts the gain of the proportional integrator so as to compensate the stability of the control system based on the prediction accuracy of the predicted value calculated by the predicting unit. Even if there is a dead time after the entry side tension of the is operated to be reflected in the measured strip width, the control gain that achieves high responsiveness while compensating for stability can be obtained without trial and error. You can get it automatically. In addition, even if the set operating conditions such as strip width, rolling speed, strip temperature, etc. are changed, the gain of the proportional integrator is changed during rolling, so the stability of the control system is maintained. can do.
In the above embodiment, two rolling stands are shown for the sake of simplicity, but the technical scope of the present invention is not limited to this. It is of course possible to apply the present invention to a continuous rolling mill. Furthermore, the present invention can be applied not only to one rolling stand but also to a plurality of rolling stands in a hot continuous rolling mill.

[0011]

As described above, according to the plate width control device of any one of claims 1 to 3, a mathematical model expressing the characteristics from the tension command value to the measured plate width is used. A prediction unit that calculates the predicted value of the plate width deviation online and corrects the control input of the proportional integrator based on the predicted value; and a prediction accuracy of the predicted value calculated by the prediction unit. By including a gain adjusting unit that adjusts the gain of the proportional integrator so as to compensate for the stability of the control system, after the entry side tension of a certain rolling stand is manipulated, it is reflected in the measured strip width. Even when there is a dead time, the control gain that achieves high response while compensating for stability can be automatically obtained without trial and error. Moreover, according to the strip width control device of the third aspect, even when the set operating conditions such as strip thickness, rolling speed, strip temperature and the like are changed, the gain of the proportional integrator is changed according to the change. Since it is changed during rolling, the stability of the control system can be maintained.

[Brief description of drawings]

FIG. 1 is a control block diagram showing a schematic configuration of a plate width control device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between the strip width control device A1 and a hot continuous rolling mill.

FIG. 3 is a diagram showing an equivalent control block of the plate width control device A1.

FIG. 4 is a diagram for explaining a prediction error in the plate width control device A1.

FIG. 5 is a diagram for explaining a multiplicative error in the plate width control device A1.

FIG. 6 is a diagram for explaining a gain setting range.

FIG. 7 is a diagram comparing simulation results of the plate width control device A1 and a conventional technique using PI control.

[Explanation of symbols]

1 ... Proportional integrator 2 ... Predictor 3 ... Gain adjustment section

─────────────────────────────────────────────────── ─── Continuation of front page (72) Yoshinori Fujita Inventor Yoshinori Fujita 1 Kanazawa-machi, Kakogawa-shi, Hyogo Kobe Steel Co., Ltd. Kakogawa Works (56) Reference JP-A-9-182908 (JP, A) JP-A-57 -44410 (JP, A) JP 62-289307 (JP, A) JP 7-214127 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B21B 37/00- 37/78

Claims (3)

(57) [Claims] 1. A strip width deviation between a strip width and a strip width actually measured on the exit side of a rolling stand of a hot continuous rolling mill for rolling a material to be rolled using a plurality of rolling stands is eliminated. In the strip width control device that calculates the tension command value by the proportional integrator and operates the entry side tension of the rolling stand based on the tension command value as described above, a mathematical expression expressing the characteristic from the tension command value to the actually measured strip width. Using the model, the predicted value of the plate width deviation is calculated online, and the prediction unit that corrects the control input of the proportional integrator based on the predicted value, and the predicted value calculated by the prediction unit A plate width control device comprising: a gain adjusting unit that adjusts the gain of the proportional integrator so as to compensate the stability of the control system based on the prediction accuracy. 2. The strip width control device according to claim 1, wherein the mathematical model includes a dead time element. 3. The gain adjusting unit comprises a plate thickness, a rolling speed,
Alternatively, the strip width control device according to claim 1 or 2, wherein the gain of the proportional integrator is changed during rolling based on a set operating condition including at least the strip temperature or a combination thereof.