JP2010253501A - Method and device for controlling tension in multistage rolling mill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the stability of operation and also to improve the accuracy of a product by controlling interstand tension at the target tension value. <P>SOLUTION: The method for controlling tension is a method for controlling the tension of a rolled stock 6 which is rolled with a rolling stand 2 provided in a multistage rolling mill 1 and includes a target orbit calculating step where the target orbit data stipulating change by time in the tension of the rolled stock 6 is beforehand calculated and a tension controlling step for controlling the tension of the rolled stock 6 on the basis of the deviation between the actual value of the tension of the rolled stock 6 and the target orbit data. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a tension control method and a tension control that are used when hot rolling a rolled material continuously in a multi-stage rolling mill equipped with a plurality of rolling stands, and that can improve operational stability and product accuracy. Relates to the device.

  Conventionally, rolled materials such as thin steel plates and thin aluminum plates have been manufactured by a multi-stage rolling device (continuous rolling device) having a plurality of rolling stands. As one of the evaluation criteria of the final product in hot rolling and cold rolling in multi-stage rolling equipment, there are plate thickness and plate width, but this plate thickness and plate width are affected by the tension applied to the material during rolling, It is important to control the tension to the target value. In particular, the rolled material in hot rolling is heated to a high temperature, and the deformation resistance of the rolled material is reduced. Therefore, if a large tension is applied, the material may break, so the controlled variable is the tension. It has great significance.

When the control amount is tension, the control operation amount includes a roll speed, a looper angle, or a roll gap amount. Regarding the tension control in such a rolling apparatus, there are the following techniques.
Japanese Patent No. 3041155 (Patent Document 1) measures the height of a looper installed between rolling stands, operates a roll speed control device based on the difference between the looper height and a target height, and rolls between stands. Operate the looper current control device based on the difference between the material tension and the target tension, estimate the resonance frequency and damping coefficient of the looper control system from multiple measured values, and set the roll speed control device to the set value according to the estimated value. A looper control device is disclosed in which changes are made, the resonance frequency and the damping coefficient are corrected to appropriate values, and the rolling equipment is stabilized.

  Further, Japanese Patent No. 3451919 (Patent Document 2) detects the stand entry side plate thickness fluctuation caused by an unspecified cause by using a gauge thickness calculation value or a gauge meter plate thickness calculation value in the preceding stand, and enters the side plate thickness fluctuation. Calculate the rearward rate (= rear tension) fluctuation of the stand by calculating the output side thickness change amount to suppress the fluctuation, and perform the reduction operation or change the output side thickness target value according to the calculation result In addition, a tension control method between stands in a hot continuous rolling apparatus that suppresses the occurrence of fluctuations in tension due to the entry side plate thickness is disclosed.

Japanese Patent No. 3041155 Japanese Patent No. 3451919

In the looper control device disclosed in Patent Document 1 described above, only the steady portion after passing the rolling material tip is assumed, and only the stabilization of the tension control system and the looper height control system is emphasized. However, it is difficult to suppress fluctuations in tension and thickness at the front and rear ends of the rolled material.
Furthermore, in the tension control method disclosed in Patent Document 2, the thickness deviation cannot be suppressed only by suppressing the occurrence of the plate thickness fluctuation caused by the tension fluctuation. In addition, this technology assumes slight fluctuations in tension at the steady part of the rolled material, and it is difficult to deal with large fluctuations in tension at the unsteady part (front end and rear end) of the rolled material. It has become.

  Therefore, in view of the above problems, the present invention adjusts the roll speed, the looper angle, or the roll gap amount as the control operation amount in the multistage rolling mill, so that the tension between the rolling stands becomes the target tension value with a preferable time change. It is an object of the present invention to provide a tension control method and a tension control device that improve the operation stability and improve the product accuracy by controlling as described above.

In order to achieve the above-described object, the present invention takes the following technical means.
That is, the tension control method for a multi-high rolling mill according to the present invention is a method for controlling the tension of a rolled material that is rolled by a rolling stand provided in a multi-high rolling apparatus, and defines the time change of the tension of the rolled material. A target trajectory calculation step for preparing the target trajectory data in advance, and a tension control step for controlling the tension of the rolled material based on a deviation between the actual tension value of the rolled material and the target trajectory data. And
As a normal tension control method, a target tension value is set as a control target value, and PI control is sometimes performed. In this case, the measured tension value suddenly increases when the leading end of the rolled material is caught. However, the control operation amount may change greatly, and the controllability may be remarkably deteriorated (for example, a large overshoot). According to the tension control method of the present invention, target trajectory data (data indicating a preferable temporal change in tension) prescribing a temporal change in the tension of the rolled material (tension between rolling stands) is calculated in advance, and the target tension value is calculated. Instead, the target trajectory data is used. Then, the tension of the rolled material is controlled based on the deviation between the actual tension value and the target trajectory data. For this reason, unstable control in which the tension value greatly overshoots is avoided, and the tension is stably controlled. As a result, operational stability (through plate stability) is improved, and product accuracy can be improved.

In addition, when the deviation between the actual tension value of the rolled material and the target tension value is small, the tension control step controls the tension of the rolled material based on the deviation, and the actual tension value and the tension of the rolled material. When the deviation from the target value is large, the tension of the rolled material may be controlled based on the deviation between the actual tension value and the target trajectory data.
By doing so, the technique of the present invention can be applied only when necessary (when the deviation between the actual tension value of the rolled material and the target tension value is large), and for example, the calculation load of the control device can be reduced.

Preferably, in the tension control step, the tension of the rolled material is controlled by operating any one of a roll speed, a roll gap amount, and a looper angle of a rolling stand, which are control operation amounts.
More preferably, the target trajectory calculation step may calculate the target trajectory data after applying a constraint condition to the amount of change in the control operation amount.
The constraint condition may be set based on a characteristic value of the rolling stand or a tension value of the rolled material.

  Further, the tension control device of the multi-high rolling mill according to the present invention is a device for controlling the tension of the rolled material rolled by the rolling stand provided in the multi-high rolling device, and regulates the time change of the tension of the rolled material. A target trajectory calculation unit that preliminarily creates the target trajectory data, and a tension control unit that controls the tension of the rolled material based on a deviation between the actual tension value of the rolled material and the target trajectory data. Features.

  By using the tension control method for a multi-high rolling mill and the tension control device for a multi-high rolling mill according to the present invention, the tension between rolling stands is controlled so as to become a target tension value with a preferable time change, thereby improving operational stability. At the same time, the product accuracy can be improved.

It is a figure which shows the whole structure of the multistage rolling apparatus which concerns on embodiment of this invention. It is the figure which expanded a part of multi-stage rolling apparatus concerning the embodiment of the present invention. It is a flowchart which shows the process performed by a control part. It is a figure which shows the simulation result using the tension control method of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.
FIG. 1 is a diagram schematically showing a multi-stage rolling apparatus (hot continuous rolling apparatus) according to the present embodiment, and FIG. 2 is a view showing a part of the multi-stage rolling apparatus.
As shown in FIGS. 1 and 2, the multi-stage rolling mill 1 includes a plurality of rolling stands 2 (in FIG. 2, an upstream i-th rolling stand 2 and a downstream (i + 1) -th rolling stand 2). And a control unit 11 that controls the speed of the rolling roll 4A so that the tension between the rolling stands (sometimes referred to simply as tension) is appropriate. In this multi-stage rolling apparatus 1, the rolled material 6 is rolled into a product plate having a desired plate thickness, plate width and plate crown by passing through a plurality of rolling stands 2, and taken up by a coil winder 3. It is conveyed to the next process.

The rolling roll 4 </ b> A (work roll) of the rolling stand 2 is driven by an electric motor 7, and the electric motor 7 can freely rotate at a rotational speed by a roll speed control unit 5 that operates based on a command from the target trajectory calculation unit 8. It can be adjusted. Further, the gap between the upper and lower rolling rolls 4 </ b> A has a structure in which the gap can be freely adjusted by hydraulic pressure or a reduction device (not shown) driven by the electric motor 7.
Each of the upper and lower rolling rolls 4A includes a backup roll 4B. On the exit side of the final rolling stand 2, a plate thickness detector (not shown) for detecting the plate thickness of the rolled material 6 is provided. Further, a looper 9 for detecting the tension between the rolling stands 2 is provided.

The control unit 11 includes a roll speed control unit 5, a target trajectory calculation unit 8, and a trajectory table storage unit 10.
The roll speed control unit 5 is based on the tension between the rolling stands measured by the looper 9 and the output of the target trajectory calculation unit 8, and the roll speed (control operation amount) of the previous stage (the i-th rolling stand 2 on the upstream side). Is operated to control the tension (control amount) between the rolling stands.
The target trajectory calculation unit 8 creates target trajectory data (time change curve of the target tension) based on the measured tension value input from the looper 9 and product information such as plate thickness and width, and roll speed control. It is to be sent to part 5. Further, the target trajectory data can be written in the trajectory table storage unit 10 and the target trajectory data calculated in the past can be read out from the trajectory table storage unit 10.

In summary, a major feature of the present embodiment is that the roll speed control unit 5 adjusts the roll speed so as to change the tension along the target track data calculated by the target track calculation unit 8.
FIG. 3 is a flowchart showing a tension control process executed in the control unit 11. The tension control method according to the present embodiment will be described with reference to this flowchart. In the roll speed control unit 5 according to the present embodiment, feedback control based on PI control is executed.

  In step 1 (hereinafter, step is described as S), the target trajectory calculation unit 8 calculates target trajectory data by offline calculation. The target trajectory data is represented by the following formula (1).

Hereinafter, a method for calculating the target trajectory data will be described, but the method is not limited to this method. The operator may arbitrarily set it.
First, it is assumed that the characteristics of the rolling stand 2 and the characteristics of the roll speed control unit 5 are expressed by Expression (2).

  Here, a case where a restriction on the roll speed command value is adopted as a restriction condition (constraint condition) and this is expressed by Expression (3) is considered.

Β is a constant determined from the equipment specification or control specification, and is a numerical value determined by the operator in advance.
For such a restraint system, a reference governor design method is used as a method for calculating a control operation amount (roll speed and looper torque) for stabilizing the tension control system so that the constraint of the expression (3) is satisfied. By applying, the target trajectory data of the formula (1) can be calculated.
Furthermore, assuming a general situation, consider a case where there is a restriction on the rate of change of the roll speed command value. This constraint is shown in Equation (4).

  Here, if the purpose of the control is to set the tension value to the target tension before the M sampling time, the following equation (5) is satisfied, and the constraint on the rate of change of the above equation (equation (4)) is satisfied. Can be satisfied.

Here, as the initial value of the operation amount, for example, a pass schedule value in the rolling setting calculation is used. The target trajectory data is calculated by a reference governor design method using Expression (5) instead of Expression (3) as a constraint expression related to the operation amount. Thereby, the target trajectory data that satisfies the restriction on the change rate can be obtained.
On the other hand, as the restriction on the rate of change, not only the hardware aspect of the rolling stand 2 but also the rolling state may be noticed.
For example, the following formula (6) is applied in consideration of the restriction on the tension between the stands from the viewpoint of securing the plate passing property in a good state.

  The target trajectory data may be calculated by the reference governor design method using Expression (7) as a constraint expression related to the control operation amount.

By performing control so as to follow the obtained target trajectory data, the expression (6) is satisfied, and the restriction of the sheet passing property is satisfied. This calculation is performed according to the value of the tension deviation and further according to the type and size of the rolled material.
In S <b> 2, the target trajectory calculation unit 8 stores the value of the target trajectory data obtained in S <b> 1 in the trajectory storage table of the trajectory table storage unit 10. In this case, the target trajectory table is updated by storing in a table corresponding to six types of rolled material, dimensions, or tension deviation. S1 described above is the target trajectory calculation step.

  In S3, the roll speed control unit 5 determines that the tip of the rolled material 6 is the rear stand (downstream side) between the target stands (here, between the upstream i-th stand and the downstream (i + 1) stand). The inter-stand tension value (tension measurement value) measured after biting into the (i + 1) th stand) is obtained, and the deviation (tension deviation value) between the tension measurement value and the target tension value is expressed by the following formula ( Calculate according to 8). After S3, online calculation is performed.

  In S4, whether or not the roll speed control unit 5 refers to the target trajectory data stored in the trajectory table storage unit 10 in S2 according to the equation (9) using the tension deviation value calculated in S3. Determine. This is because it is not necessary to calculate the control operation amount with reference to the target trajectory data according to this embodiment because the control operation amount does not become a large value when the tension deviation value is low. .

In the equation (9), α is a predetermined threshold value in consideration of the characteristics of the rolling stand 2 and the like. If the tension deviation value is larger than threshold value α in S4 (YES in S4), the process proceeds to S5A. If not (NO in S4), the process proceeds to S5B.
In S5A, the target trajectory calculation unit 8 refers to the target trajectory data stored in the trajectory table storage unit 10. The target trajectory data is expressed by equation (10), which indicates that the target trajectory data up to the sampling time ahead is given.

  Here, since Expression (11) is established, it can be understood that the final value of the referenced target trajectory data matches the tension target value.

  In S5B, the target trajectory calculation unit 8 sets the target trajectory data as a target tension value (a constant value). The target trajectory data at this time can be expressed by Expression (12).

  In S6, the roll speed control unit 5 calculates a control calculation amount as shown in Expression (13) using an arithmetic expression applied in PI control.

  In S7, the roll speed control unit 5 adds the previous speed command value of the roll speed control unit 5 to the control calculation amount calculated in S6, and changes the roll speed as shown in Expression (14). .

S3 to S7 described above are tension control steps.
In S8, the roll speed control unit 5 determines whether or not the rolling is finished. At this time, the target trajectory data calculation unit 1 determines the end of rolling based on whether or not the tail end portion of the rolled material 6 has passed the corresponding rolling stand 2. If it is determined that rolling has ended (YES in S8), this process ends. If not (NO in S8), the process returns to S6 to repeatedly calculate the control operation amount.
The tension control operation by the target trajectory calculation unit 8 having the above-described structure and flowchart will be described in comparison with the prior art.

FIG. 4 shows the result of the control operation according to the prior art (dotted line) and the result of the control operation according to the present embodiment (solid line).
First, in the prior art, when the looper 9 rises when the tip of the rolled material 6 is bitten, the measured tension value suddenly rises, and the roll speed command value is lowered by the tension controller accordingly. At that time, because the mass flow between the stands is greatly disturbed due to a rapid change in the roll speed, the thickness deviation also changes greatly, and if the change is large, it falls below the target tension value, and the roll thickness control system responds accordingly. The gap is corrected, resulting in further mass flow disturbances. For this reason, after the plate thickness deviation fluctuates oscillating for a while with the target plate thickness in between, the result follows the target plate thickness.

On the other hand, in the target trajectory calculation unit 8 according to the present embodiment, target trajectory data (one-dot chain line) is calculated from the target tension value and the measured tension value at the tip when the tip of the rolled material 6 is passed. It can be seen that the target trajectory data is drawn by a gentle curve extending from the tip tension value toward the target tension value.
Since control is performed so that the tension value follows the target trajectory data, a rapid change in tension at the tip of the rolled material 6 is suppressed and control is performed so as to change gradually as compared with the above-described conventional technique. This confirms that the target trajectory data is being followed. Further, at this time, the deviation between the tension value and the target trajectory data is small as compared with the prior art, so that the roll speed command value at the tip of the rolled material 6 is not changed suddenly and is changed gently. I can confirm. Due to these effects, the plate thickness deviation and the roll gap correction amount also change gently, and the rapid change of the plate thickness deviation seen in the prior art does not occur.

As described above, according to the tension control method and apparatus according to the present embodiment, when the tip of the rolled material 6 is caught in the roll of the upstream rolling stand 2, the measured tension value and the target tension value are If the tension deviation is large, the control operation amount is calculated with reference to the target trajectory data, so that unstable control such as a large overshoot is avoided and the tension is stabilized. Thereby, the tension between the stands is controlled so as to become a target tension value with a preferable time change, and it is possible to improve the operational stability (plate stability) and the product accuracy.
It should be thought that embodiment disclosed this time is an illustration and restrictive at no points. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims. For example, the control operation amount is not limited to the roll speed, and may be a looper angle or a roll gap amount.

DESCRIPTION OF SYMBOLS 1 Multi-stage rolling apparatus 2 Rolling stand 3 Coil winder 4A Rolling roll 4B Backup roll 5 Roll speed control part 6 Rolled material 7 Electric motor 8 Target track | orbit calculation part 9 Looper 10 Track table memory | storage part 11 Control part

Claims (6)

A method of controlling the tension of a rolled material rolled by a rolling stand provided in a multi-stage rolling apparatus,
A target trajectory calculation step for preliminarily creating target trajectory data defining a time change in tension of the rolled material;
A tension control method for a multi-high rolling mill, comprising: a tension control step for controlling the tension of the rolled material based on a deviation between the target track data and the actual tension value of the rolled material.   When the deviation between the actual tension value of the rolled material and the target tension value is small, the tension control step controls the tension of the rolled material based on the deviation, and the actual tension value and the target tension value of the rolled material. 2. The tension control method for a multi-high rolling mill according to claim 1, wherein the tension of the rolled material is controlled based on a deviation between the actual tension value and the target trajectory data.   The tension control step controls the tension of the rolled material by operating any one of a roll speed, a roll gap amount, and a looper angle of a rolling stand, which are control operation amounts. The tension control method of the multi-high rolling mill described in 1.   The multi-stage rolling mill according to any one of claims 1 to 3, wherein the target trajectory calculation step calculates the target trajectory data after applying a constraint condition to a change amount of the control operation amount. Tension control method.   The tension control method for a multi-high rolling mill according to claim 4, wherein the constraint condition is set based on a characteristic value of a rolling stand or a tension value of a rolled material. An apparatus for controlling the tension of a rolled material rolled by a rolling stand provided in a multi-stage rolling apparatus,
A target trajectory calculation unit that preliminarily creates target trajectory data that prescribes a change in the tension of the rolled material, and the tension of the rolled material is controlled based on a deviation between the actual tension value of the rolled material and the target trajectory data. A tension control unit for the multi-high rolling mill.

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