JP3405499B2 - Thickness and tension control method in 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 plate thickness / tension control method for a tandem rolling mill, and particularly for a tandem rolling mill for cold work or the like, controlling the plate thickness of a material to be rolled to a target value and stabilizing the tension. The present invention relates to a plate thickness / tension control method for a tandem rolling mill, which is suitable for use at the time.

[0002]

2. Description of the Related Art The purpose of control in a rolling mill is to match the outlet plate thickness of a target stand with a predetermined target value.
When performing control to match the plate thickness with the target value in this way, for example, with a cold tandem rolling mill, the change in the tension on the inlet side of the target stand greatly affects the outlet side plate thickness of the stand. It is necessary to control the tension and the outlet plate thickness at the same time.

FIG. 5 shows a schematic structure of a conventional general plate thickness / tension control system for simultaneously controlling the outlet plate thickness and the inlet tension of a target stand.

FIG. 5 shows two rolling stands of the cold tandem rolling mill, a second stand (No. 2 in the figure) and a third stand (No. 3 in the figure) downstream thereof. The thickness gauges 82,
84, and a tensiometer 86 is installed between both stands. Further, each stand has a roll speed control device 88, 9
0, hydraulic pressure reduction control devices 92 and 94 are installed, respectively.

Further, FIG. 5 shows a control configuration when the third stand is a target stand, and a plate thickness control device 96 for controlling the plate thickness on the stand-out side and the same stand input device. A tension control device 98 for controlling the side tension is installed. That is, the plate thickness control device 96 outputs a control signal to the roll speed control device 88 based on the detection signal input from the plate thickness gauge 84 to operate the roll speed of the second stand, thereby 3 Control the plate thickness on the stand-out side. Further, the tension control device 98 uses the tension meter 86.
A control signal is output to the hydraulic pressure reduction control device 94 based on a detection signal input from the control unit to operate the pressure reduction position of the third stand to control the inter-stand tension.

Conventionally, in cold tandem rolling, the first stand, which is the most upstream, is excluded, and the thickness and tension control structure at the stand on the downstream side (hereinafter, referred to as an intermediate stand) is such that a rolling operation is performed on the target stand and from the degree of the front roll speed operation impact on the stand delivery side thickness and entry side tension, as in the third stand shown in FIG. 5, left for a side thickness deviation of the preceding second stand The roll speed operation is performed, and the deviation of the tension on the inlet side is dealt with by the operation of the pressing position of the third stand. The control loops for the outlet plate thickness and the inlet tension are independently configured, and proportional / integral control is performed. The feedback control was performed by.

On the other hand, as an automatic plate thickness control method (generally called AGC), there is a feedback control based on a plate thickness deviation detection value on the stand outlet side as described in, for example, JP-A-63-7848, The feed-forward control based on the detection value of the plate thickness deviation on the side, the mass flow plate thickness control based on the constant law of mass flow, etc. are known.
Is generally used in combination with inter-stand tension control.

Further, in the case of controlling the plate thickness and the tension at the same time, together with the feedback control, an unknown disturbance such as a stand-inside plate thickness variation and a material hardness variation is estimated in advance, and an operation is performed to compensate the influence of the estimated disturbance value. If the input can be added in a feedforward manner, the influence of disturbance on the output can be basically removed. Therefore, this method is useful in that the influence of disturbance on the output can be positively removed.

[0009]

However, as described above, when simultaneously controlling the plate thickness and the tension, the feedforward control for estimating the disturbance and compensating it in a feedforward manner is performed together with the feedback control as described above. When it is also performed, there is a problem that the model formula used for estimating the disturbance is accurate and a steady deviation remains in the output unless a correction error is generated.

The present invention has been made to solve the above-mentioned conventional problems, and is a feedforward method for compensating, in a feedforward manner, the influence of an unknown disturbance on the output side plate thickness and the input side tension of the target stand on each detection output. A plate thickness capable of controlling the above-mentioned outlet side plate thickness and inlet side tension with high accuracy by using control and feedback control for making the output follow a target value based on each detected output in cooperation with each other. -It is an object to provide a tension control method.

[0011]

DISCLOSURE OF THE INVENTION The present invention is directed to plate thickness / tension control in a tandem rolling mill that simultaneously controls the outlet side plate thickness and the inlet side tension of the target stand by the rolling operation of the target stand and the roll speed operation of the preceding stand. In the method, based on each detected value of the outlet side plate thickness and the inlet side tension of the target stand, and the deviation from these target values, feedback control that makes the detected values follow the target values, and the unknown disturbance is steady
Is estimated using a linearized model equation in the vicinity of the part, and is performed together with feedforward control for compensating the influence of the disturbance estimation value in a feedforward manner, and in the feedback control, the influence amount of the feedforward control is calculated. The problem is solved by making a prediction using a model and feeding back a value obtained by subtracting the predicted value from the actual value.

That is, in the present invention, when the feedback control is performed, the effect (influence amount) of the disturbance feedforward control described above is predicted using a model, and a value obtained by subtracting them from the detected actual value is used. Since the feedback is performed, the disturbance feedforward control and the feedback control can be operated in cooperation with each other, and the effects of each control can be sufficiently exerted.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a schematic structure of a main part of a plate thickness / tension control system applied to this embodiment. As in the case of FIG. 5, the target stand is a cold tandem rolling mill 10. In the third stand, the front stand is the second stand.

Plate thickness gauges 12 and 14 and tensiometers 16 and 18 are respectively provided on the downstream sides of the second and third stands, and the roll speed control device 2 is provided at each stand.
0 and 22 and hydraulic pressure reduction control devices 24 and 26 are attached respectively, and based on the detection values of the plate thickness gauge 14 and the tensiometer 16, the roll speed control device 20, and the measurement values of the hydraulic pressure reduction control device 26. A roll speed control device 20 and a plate thickness / tension control device 28 for calculating control signals for the hydraulic pressure reduction control device 26 are provided.

FIG. 2 is a block diagram showing the details of the control device 28. The control device 28 is a controlled object 50 corresponding to the third stand and the second stand of the preceding stage.
A feedback control unit 52, a disturbance estimator 56 and a disturbance compensator 58 that form a disturbance feedforward control unit 54, and a controlled object model 60.

That is, in this embodiment, the basis of the control device 28 is that the disturbance feedforward control section 54 for executing control based on the disturbance estimated value estimated by using the model, the detection output and their target values. A feedback control unit 52 that executes control based on the deviation of 1 and a state prediction unit (control target model) 60 that predicts the effect of disturbance feedforward control using a model.

As described above, the disturbance feedforward control section 54 is composed of the disturbance estimator 56 and the disturbance compensator 58. The former disturbance estimator 56 uses the former disturbance estimator 56 to detect unknown disturbances such as fluctuations in the inlet side plate thickness and material hardness of the target stand. Using the model, the amount of rolling position change of the target stand and the amount of roll speed change of the preceding stand that compensate for the unknown disturbance estimated by the latter disturbance compensator 58 are obtained, and are calculated.
By giving it as an operation command to 0, it has a function of suppressing the influence of unknown disturbance. The compensation control by the disturbance feedforward control unit 54 is disclosed in, for example, Japanese Patent Laid-Open No. 62-62
The technology disclosed in -214818, etc. can be used.

Further, the feedback control unit 52 is arranged to deviate the detected values of the stand outlet side plate thickness and the inlet side tension from the target values,
Alternatively, feedback control based on deviations from the target values of the rolling position, roll speed, etc. from the target value is executed, and the rolling position of the target stand and the roll speed of the preceding stand are corrected based on the feedback signal to adjust the plate thickness and tension. It has the function of following the target value.

For the feedback control unit 52, the plate thickness / tension non-interference control based on the multivariable control theory in which the interference between the plate thickness and the tension is taken into consideration is applied.

In order to realize highly accurate plate thickness / tension control by using the above-mentioned two control units 52 and 54 together, output due to unknown disturbance estimated by disturbance feedforward control (outlet plate thickness and inlet tension) And the change (influence amount) of the state quantity (roll down position, roll speed, etc.) is predicted using a model, and the value obtained by subtracting these predicted values from the actual value (detected output and measured state quantity) is feedback controlled. By using the feedback input of the section 52 to correct the correction error amount by the disturbance feedforward control by the feedback control, the plate thickness / tension control excellent in the disturbance suppression and the accompanying high-accuracy target value followability. The system is realized.

The control operation in this embodiment will be described in detail below. The detection values of the exit side plate thickness of the third stand detected by the plate thickness gauge 14 and the entrance side tension of the same stand (No. 2-3 stand tension) detected by the tensiometer are the plate thickness. It is input to the tension control device 28. The plate thickness / tension controller 28 performs various calculations to be described later, and the reduction command value for the third stand and the roll speed for the second stand to eliminate the deviation between these detected values and a predetermined target value. Command values are calculated, and these signals are output to the hydraulic pressure reduction control device 26 of the third stand and the roll speed control device 20 of the second stand, respectively. Thereby, the outlet side plate thickness and the inlet side tension of the third stand are appropriately controlled.

The calculation executed in the plate thickness / tension controller 28 will be described in detail. The disturbance estimator 56 constituting the disturbance feedforward controller 54 in FIG. 2 outputs the output of the control target 50, that is, the output of the target stand. The detected values of the side plate thickness and the entrance tension and the state quantities measurable in the controlled object 50, that is, the measured values of the rolling position of the target stand and the roll speed of the preceding stand are input, and control is performed from these input signals. An unknown disturbance including fluctuations in the plate thickness on the entrance side, fluctuations in material hardness, etc. is estimated using a model describing the target 50. In this embodiment, as the model for estimating the disturbance,
From the viewpoint that a simpler one is preferable when applied to an actual machine, a model formula linearized near a certain stationary part was used.

The estimated disturbance value obtained by the disturbance estimator 56 is output to the disturbance compensator 58. This disturbance compensator 58
Then, based on the model, the command value B corresponding to the operation change amount of the roll speed of the preceding stand and the command value A corresponding to the operation change amount of the stand for compensating the influence of these disturbance estimated values on the output. And are output to the respective control devices of the controlled object 50, that is, the roll speed control device 20 and the hydraulic pressure reduction control device 26, respectively.

The disturbance signal estimated by the disturbance estimator 56 is also output to the controlled object model 60. The controlled object model 60 is an estimation model in which the controlled object 50 is linearized in the vicinity of a certain stationary part, and has a disturbance compensation input calculated from the disturbance estimated value as its input, and the model causes the disturbance to the controlled object 50. Disturbance compensator 5 based on the estimated value
The output and the state quantity when the compensation command values A and B calculated in 8 are input are predicted.

On the other hand, as described above, the plate thickness / tension decoupling controller (feedback control section) 52 is constructed on the basis of the multivariable control theory as disclosed in, for example, Japanese Patent Laid-Open No. 5-31517. From the state feedback control based on the state quantity such as the rolling position of the third stand and the roll speed of the preceding stage stand, and the output integration type feedback control based on the detected output values of the outlet side plate thickness and the inlet side tension of the third stand. It is configured.

The feedback input of the plate thickness / tension decoupling controller 52 is the output value of the control target 50 and the actual value of the state quantity, and the disturbance estimator 56 of the disturbance feedforward control unit 54 is controlled by the control target model 60. The difference (C to E) between the output and the predicted value of the state quantity calculated on the basis of the disturbance estimated in 1. is used. Thus, the difference signals CE
By the feedback control with the input as the input, the influence of the disturbance on the output (thickness at the outlet side, tension at the inlet side) can be suppressed by the disturbance feedforward control unit 54, and can be suppressed by the control by the disturbance feedforward control unit 54. Effect on output due to undisturbed disturbance (correction error)
Can be compensated by the plate thickness / tension non-interference feedback control unit 52, so that it is possible to prevent a steady deviation from remaining in the output, and to make the output follow the target value with high accuracy. .

As described above in detail, according to the plate thickness / tension control method of this embodiment, the disturbance feedforward control for compensating the disturbance in a feedforward manner and the feedback control for making the output follow the target value are mutually performed. Since they can be operated in cooperation with each other, it is possible to obtain a product plate thickness with higher accuracy.

Further, according to this embodiment, there are the following advantages. As described above, in the conventional plate thickness / tension control method, one control section is assigned to each control system, and the control loops are separately configured so that the interference of each control system is small and can be ignored. However, for example, when rolling a thin material, the controllability of the inlet side tension due to the rolling down operation in the post stand becomes low, and as a result, the rolling down operation has a relatively large effect on the outgoing side plate thickness and interferes with both control systems. Therefore, there is a problem in control accuracy particularly in the acceleration / deceleration unit. Even in such a case, there is no interference between the control systems, and the conventional method such as AGC, etc., in which the plate thickness control system and the tension control system are configured by separate loops is more effective than ever. There is a problem that it is difficult to obtain the plate thickness accuracy.

On the other hand, according to this embodiment, since the plate thickness / tension non-interference controller is used as the feedback control section 52, it is possible to control even a thin material with sufficient accuracy. Compared with this, it is possible to control the outgoing plate thickness and the incoming tension with higher accuracy.

Next, in order to clarify the effect of the present invention, the control result according to this embodiment and the control result according to the conventional proportional-integral (PI) control method will be compared and described. Here, in the cold tandem rolling mill with a four-stage stand, in the tandem rolling in which the target plate thickness is 0.505 mm for the mother plate having the plate thickness of 2.3 mm and the plate width of 1,223 mm, the method according to this embodiment and the conventional method 3 and FIG. 4 show the results of examining the variation of the plate thickness on the outlet side of the final stand and the variation of the tension on the inlet side when and are applied to the final stand, respectively.

In each of the figures, the plate thickness variation is shown on the upper side, the tension variation is shown on the lower side, the horizontal axis shows time, and the vertical axis shows the deviation of each target value from the target value. As is apparent from FIGS. 3 and 4, it can be understood that the method of the present invention reduces the variation in plate thickness and the variation in tension to about 1/2 as compared with the conventional method.

Although the present invention has been specifically described above, the present invention is not limited to the one shown in the above embodiment, and various modifications can be made without departing from the spirit of the invention.

For example, as the feedback control section 52, the case where a plate thickness / tension non-interference controller is used is shown.
Since the present invention is a technique for cooperatively configuring feedback control and feedforward control, the method of feedback control is not particularly limited, and P of the conventional method is used.
Various methods such as I control and optimum control can be used.

[0035]

As described above, according to the present invention,
Feedforward control that compensates for the influence of unknown disturbance on the output thickness of the output side and the tension on the input side in a feedforward manner and feedback control that makes the output follow the target value based on the detected output are used together Therefore, it is possible to improve the control accuracy of the outlet plate thickness and the inlet tension of the target stand.

[Brief description of drawings]

FIG. 1 is a plate thickness applied to an embodiment according to the present invention.
Explanatory diagram showing the main configuration of the tension control system

FIG. 2 is a block diagram showing details of a plate thickness / tension control device used in the control system.

FIG. 3 is a diagram showing an example of control results by the method of the present invention.

FIG. 4 is a diagram showing a control result by a conventional method.

FIG. 5 is an explanatory diagram showing a main part configuration of a conventional plate thickness / tension control system.

[Explanation of symbols]

10 ... Cold tandem rolling mill 12, 14 ... Plate thickness gauge 16, 18 ... Tensiometer 20, 22 ... Roll speed control device 24, 26 ... Hydraulic pressure reduction control device 28 ... Plate thickness / tension control device 50 ... Controlled object 52 ... Feedback control unit 54 ... Disturbance feedforward control unit 56 ... Disturbance estimator 58 ... Disturbance compensator 60 ... Control target model

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B21B 37/00-37/78

Claims (2)

(57) [Claims] 1. A strip thickness / tension control method for a tandem rolling mill, wherein the strip thickness and strip tension of a strip stand at the same time are simultaneously controlled by a rolling operation of the strip stand and a roll speed operation of a preceding stand. Based on the detected values of thickness and inlet tension, and the deviations from these target values, feedback control that makes the detected values follow the target values, and unknown disturbance
Estimate using a linearized model formula in the vicinity of the stationary part and perform it together with feedforward control that compensates for the influence of the disturbance estimated value in a feedforward manner, and in the feedback control, the influence amount of the feedforward control. Is predicted using a model, and a value obtained by subtracting the predicted value from the actual value is fed back, and a plate thickness / tension control method in a tandem rolling mill is characterized. 2. The change amount of the feedforward control according to claim 1, wherein the influence amount of the feedforward control is related to an outlet plate thickness and an inlet tension of the target stand, and a state quantity including at least a rolling position of the target stand and a roll speed of the preceding stand. A method for controlling plate thickness / tension in a tandem rolling mill, which is characterized by the amount.