JPH11197726A - Method for correcting load distribution of tandem rolling mill and controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dynamically correct the outlet side plate thickness of each stand so that the load distribution of the tandem rolling mill is kept in an optimum state, and to improve the production efficiency of a tandem rolling equipment. SOLUTION: All the stands 101-1 to -4 of the tandem rolling mill 100 are equipped with speed controllers 120 for plate thickness control and rolling down controllers 121 for tension control, and are controlled respectively by plate thickness control part 122 and tension control part 123. According to the actual result value of a current for each stand from the speed controller 120 and the actual result values of inlet side and outlet side tension from the tension meter 126 of each stand, deviated quantities from the target values or rated values of rolling torque and load torque for each stand, are found by a load distribution correction control part 150 added to these controllers. The changed quantity of an outlet side plate thickness set value for optimizing a load balance state by which each deviated quantity has been evaluated, is operated, and the change command of a rate flowable to the response of the speed controller 120 is outputted to the plate thickness control part 122.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control system for a tandem rolling mill, and more particularly to a control system for dynamically correcting an imbalance in load distribution of each stand.

[0002]

2. Description of the Related Art In a tandem rolling mill in which rolling mills are continuously arranged, the use of each rolling mill is optimized.
It is necessary to produce a large number of products in a short time,
When determining the outlet plate thickness of each stand in the schedule calculation, the load distribution of all stands is optimally determined according to the type of product.

However, the thickness and hardness of the inlet coil of the tandem rolling mill are not uniform from the leading end to the trailing end.
The roughness of the work roll also changes as it is used for rolling.
For this reason, even if the delivery side plate thickness optimally determined by the schedule calculation is left as it is, a load is concentrated on a specific stand or slip occurs. When such abnormal rolling phenomenon occurs, the operator manually changes the speed while watching the rolling load of each stand and the driving current of the rolling mill, corrects the load distribution, and strives to avoid it.

[0004]

In recent years, systems for introducing thickness control to all stands for the purpose of improving the thickness accuracy have become widespread. However, in this system, the above-described speed correction by the operator interferes with the thickness control and is canceled. Even if a method of manually correcting the plate thickness set value by the operator is used together, it is difficult to correct the plate thickness set value of all the stands at the same time, so that there is a problem that the above abnormal phenomenon cannot be properly avoided. Was.

Further, in a rolling mill such as a Sendzimir mill which does not have a means for detecting a rolling load, the accuracy of schedule calculation is low in the first place, and a true rolling current cannot be determined only by the driving current of the rolling mill. Modifications were difficult.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to use only the motor drive current and the entrance and exit tensions of the rolling mill, so that the output side plate thickness of each stand can be kept optimally. And a control device that dynamically corrects the load in the coil to increase the production efficiency of the tandem rolling equipment.

[0007]

According to the present invention, a rolling torque obtained by subtracting a loss torque, an acceleration / deceleration torque, and a tension torque from a motor torque converted from a motor current for each stand is first set in order to match operating conditions of a rolling mill. The amount of change in the outlet thickness setting value of the stand is determined based on the deviation between the rolling torque and the rolling torque target value calculated by the schedule.

Further, in order to satisfy the capacity condition of the tandem rolling mill facility, a load torque obtained by subtracting a loss torque and an acceleration / deceleration torque from a motor torque converted from a motor current for each stand is obtained, and the load torque is determined by the rated load. The amount of change in the set value of the outlet side thickness of the stand is determined so as not to exceed.

In the above, the rolling torque is obtained based on the rolling current obtained by subtracting the loss current, the acceleration / deceleration current and the tension current from the motor current, and based on the load current obtained by subtracting the loss current, the acceleration / deceleration current from the motor current. The load torque may be obtained.

Further, the present invention is characterized in that the change amount of the outlet sheet thickness set value based on the deviation between the rolling torque balance and the load torque balance is combined to determine the amount of change of the outlet sheet thickness set value of each stand. In addition, the change amount of the exit side sheet thickness set value is determined by fuzzy inference as to the degree to which the exit side sheet thickness set value of each stand is desired to be changed.

Further, in order to minimize the fluctuation of the sheet thickness (product sheet thickness) on the exit side of the final stand, the change rate is determined with a change cycle longer than the control cycle of the sheet thickness control and capable of following the response of the sheet thickness control means. In addition, dynamic and optimal load distribution correction is performed in the coil while maintaining the stability of the load distribution control.

According to the present invention, the tandem rolling mill uses only the electric motor current and the incoming and outgoing tensions, does not concentrate the load on a particular stand, and has an optimum schedule determined in consideration of the shape of the plate in the schedule calculation. Since all stands can be balanced in the coil to the rolling schedule, the unbalance in the tandem rolling mill due to changes in the thickness and hardness of the incoming coil, schedule calculation errors caused by aging of the rolling mill, etc. The correction can be made automatically and the tandem rolling mill can always be maintained in an optimum operating state.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below using an example applied to a Sendzimir tandem rolling mill. FIG.
Shows a control system for a four-stand Sendzimir tandem rolling mill. The tandem rolling mill 100 has a plurality of stands 1
It is composed of 01-1 to 01-4. The material to be rolled 200 is prepared as an entry coil, and is rolled by passing between the upper and lower work rolls 110-1 to 110-4 of each stand 101 from the entry side of the tandem rolling mill.

Each of the stands 101 of the tandem rolling mills # 1 to # 4 has a speed control device 120 for controlling the work roll speed to match the command value, and the roll gap between the work rolls to match the command value. Is provided with a pressure reduction control device 121 for controlling the pressure. Further, between each stand, a thickness gauge 125 for detecting the exit side plate thickness and a tension meter 126 for detecting the tension between the stands (inter-stand tension) are provided.

The rolling control device includes a tension control unit 123 that controls the roll gap of the stand via the rolling-down control device 121 so that the deviation between the actual tension value measured by the tension meter 126 and the set value becomes zero. And a thickness controller 122 for controlling the speed of the preceding stand via the speed controller 120 such that the deviation between the actual thickness value measured by the thickness gauge 125 and the set value becomes zero. Note that, depending on the rolling state at a low speed or the like, there is also a configuration in which the speed of the preceding stand is controlled by the tension control unit 123 and the roll gap of the stand is controlled by the plate thickness control unit 122.

The setting of the target values of the plate thickness and the tension for the plate thickness control unit 122 and the tension control unit 123 is performed by the setup control unit 1.
Performed from 30. The schedule calculation is performed based on the rolling model 131 based on the information on the incoming coil of the material to be rolled and the product specifications, and the output side plate thickness and the input / output side tension of each stand for stably and efficiently producing the product. The target value is determined and output to the plate thickness control unit 122 and the tension control unit 123.

In this embodiment, in particular, the load distribution correction control unit 1
50 has been added. Here, the rolling torque actual estimated value calculated using the actual driving current value of the rolling mill sent from the speed control device 120 of each stand and the actual tension value measured by the tensiometer 126 is used as a reference for the above schedule calculation. The deviation from the rolling torque target value, the deviation between the motor load torque and the rated load torque, which are also calculated using the actual drive current value, determines the load imbalance between rolling mills, and corrects it. Change the outlet plate thickness of each stand.

FIG. 2 shows the configuration of the load distribution correction control unit. The load distribution correction control unit 150 includes a load torque calculation unit 151 for converting input data and a rolling torque calculation unit 15.
2. A load torque balance determination unit 153 and a rolling torque balance determination unit 154 that performs classification by a membership function, an output side thickness change degree inference unit 155, an output side thickness change amount determination unit 156, and an output side thickness change command output unit 157.
Consists of

The load torque calculating section 151 calculates the load torque GL applied to the electric motor for each stand based on the actual speed value ω and the actual current value I from the speed control device 120 according to equation (1).

[0020]

(Equation 1)

Where Δφ: torque coefficient of motor, I:
The actual current value of the electric motor, J: the moment of inertia of the rolling mill (electric motor + mechanical component), dω / dt: the acceleration / deceleration rate of the electric motor, and gl: the torque loss of the electric motor including the mechanical component.

The rolling torque calculator 152 includes a tension meter 126
The rolling torque GP generated by the rolling load P of the rolling mill is calculated by Equation 2 in consideration of the entry-side tension Tb and the exit-side tension Tf.

[0023]

(Equation 2)

Here, 1 is a torque arm coefficient, and R is a work roll radius.

Next, the load torque balance judging section 153 and the rolling torque balance judging section 154 respectively calculate the deviation from the target value or the rated value, and evaluate the balance state by a membership function composed of a plurality of fuzzy sets. I do.

Normally, the operating conditions of the motor for driving the rolling mill are selected so that the load torque GL is equal to or less than the rated value (100%) in all rolling schedules.
For this reason, it is necessary to monitor the load torque GL during rolling and balance the tandem rolling mills so that the load torque GLi of each stand does not exceed the rated value. On the other hand, since the rolling torque GP indicates a torque generated by a vertical force (rolling load P) of each rolling mill, each stand of the tandem rolling mill is considered in consideration of operating conditions such as the shape of the rolled material on the delivery side. The ratio (balance between stands) assigned to each station is determined by schedule calculation.

For this reason, the load torque balance determining unit 153 calculates the deviation% ΔGLi of the load torque from the rated torque determined by the equipment capacity for each stand according to Equation 3, and the rolling torque balance determining unit 154 calculates
The deviation% ΔGPi of the rolling torque actual value GP from the rolling torque target value determined from the operating conditions is calculated by the following equation (4).

[0028]

(Equation 3)

[0029]

(Equation 4)

Here, G0i: a rated load torque value of the i-th stand, GPREFi: a target rolling torque value of the i-th stand, i: a stand # (here, i = 1 to 4).

FIG. 3 shows an example of a membership function for evaluating the balance state. (A) shows the load torque balance, and (b) shows the rolling torque balance. The membership function of the load torque balance includes a load torque that is too small (LN), a load torque that is just right (LZ), and a load torque that is too large (LP). 0.0-1.
0). Similarly, the membership function of the rolling torque balance indicates that the rolling torque is too small (P
N), the rolling torque is just right (PZ), and the rolling torque is too large (PP), and each represents the degree of certainty with respect to the deviation% GPi of the rolling torque. These membership functions are set empirically and determined by tuning.

Next, the outlet sheet thickness change degree inferring unit 155 determines the balance state based on the evaluation result from both the rolling torque and the load torque as "the degree to which the outlet sheet thickness hi of each stand is desired to be changed". Fuzzy reasoning. The inference rule is based on the evaluation result of the balance state of both stands, taking into account that if the outlet side thickness setting value of the i-stand is changed, the influence will be exerted on the i + 1-th stand.

In the case of load torque balance, inference is started when the load of a specific stand exceeds the rated torque. At this time, the degree of change of the outlet plate thickness of the i-stand is classified into three stages of PBi, ZOi, and NBi, and the outlet plate thickness of the i-stand is to be changed according to the load torque state of the stand and the next stand. Infer the degree αi. Here, PBi: “i is the thickness of the exit side plate of the stand.
i is to be changed to be thicker, ZOi: "I want to keep the exit side plate thickness hi of the i stand as it is", and NBi: "I want to change the exit side plate thickness hi of the i stand to be thinner".

The inference rule is based on the state of the i-stand (LP
i, LZi, LNi) and the state of the i + 1 stand (LPi
+1, LZi + 1, LNi + 1),
The maximum is 9 ways.

FIG. 4 shows a matrix table of inference rules. (A) is a table of load torque balance, and (b) is a table of rolling torque balance. For example, in the load torque balance, "the load on the i-stand is large (LPi),
And the load of the i + 1 stand is just right (LZi +
1) ", the degree αi at which it is desired to change the outlet side plate thickness of the i-stand is“ I want to increase the outlet side plate thickness of the i-stand (PB
i) ”and“ If (LPi and LZi + 1) t
hen αi = PBi ”. At this time, P
The certainty factor of Bi is obtained from the minimum value of the conditional term as shown in Expression 5.

[0036]

(Equation 5)

For example, LPi = 0.2 and LZi + 1 =
If it is 0.8, PBi = 0.2.

On the other hand, the rolling torque balance is always inferred. As in the case of load torque balance,
PBi, Z is the degree to which you want to change the outlet plate thickness of each stand.
Oi and NBi are classified into three stages, and the degree αi at which it is desired to change the exit side plate thickness of the i-stand is inferred in accordance with the state of the rolling torque of the stand and the next stand. As shown in FIG. 4B, the inference rule is the state of the i-stand (PP
i, PZi, PNi) and the state of the i + 1 stand (PPi
+1, PZi + 1, PNi + 1)
The maximum is 9 ways.

As described above, the outlet thickness change degree inference unit 155 determines the “degree of change of the outlet thickness hi of each stand” for each of the load torque balance and the rolling torque balance by the class of PBi, ZOi, and NBi. Is obtained as the confidence in Outgoing side plate thickness change amount determination unit 156
Is the change amount Δhi of the outlet plate thickness set value from the certainty factors.
Is quantified.

First, the maximum value of the certainty factor is obtained from Equation 6 for each class of the load torque balance and the rolling torque balance. When the load torque balance is also inferred, the example of FIG. 4 includes the inference results of six rules for each class.

[0041]

(Equation 6)

Next, the degree αh at which it is desired to change the thickness setting value
REFi is obtained for each stand according to Equation 7.

[0043]

(Equation 7)

Here, ρPB: weight coefficient for Δhi = PBi, ρZO: weight coefficient for Δhi = ZOi,
ρNB: Δhi = weighting coefficient for NBi.

Next, using the degree αhREFi for which the thickness setting value of each stand is desired to be changed and the results of Expressions 3 and 4, the output side thickness setting value change amount ΔhREFi is calculated by Expression 8.

[0046]

(Equation 8)

Here, δhi / δGPi is the reciprocal of the influence coefficient of the rolling torque change on the plate thickness change.

Finally, the control output based on the change amount ΔhREFi of the outlet-side sheet thickness set value of each stand i is determined. When outputting the control command, it is necessary to correct the load distribution between the tandem rolling mills without disturbing the exit thickness of the final stand. For this reason, the output side sheet thickness change command output unit 157
The change cycle and the change rate of the outlet thickness setting value of each stand are determined so that the thickness control means of all stands can follow.

The change period ΔT is set to at least one time the maximum value of the plate thickness control periods of all the stands. Change rate Δhi / ΔT
In consideration of the thickness control closed-loop response of all stands, when the outlet thickness is changed, the thickness deviation becomes a constant value X% (for example, 0.1%).
%). When the thickness control is performed by the integral control, there is a restriction due to the integration time constant TI, and the exit side thickness change step width ΔΔhi for each change period ΔT is obtained by Expression 9.

[0050]

(Equation 9)

As described above, the output side plate thickness change command output unit 15
7 is a Δh change step width Δh for each change period ΔT.
Until REFi, the output side thickness change command is output.

[0052]

According to the present invention, the load torque of a specific stand is monitored by monitoring the load torque during rolling, which is restricted as a condition of the equipment capacity, by using only the motor current and the input and output tensions of the tandem rolling mill. The load distribution between the tandem rolling mills should be adjusted to the optimum load distribution of the rolling schedule (balance between stands) determined by the schedule calculation in consideration of the operating conditions such as the shape of the plate, etc. so as not to exceed the predetermined value. Since it can be maintained, it is possible to avoid load concentration on a specific stand. In addition, it is possible to correct the load distribution without disturbing the product thickness of the product on the delivery side in the coil in all the stands. As a result, it is possible to optimally control the load distribution in the tandem rolling mill due to a change in the thickness or hardness of the incoming coil of the rolled material, an error in the schedule calculation caused by the aging of each rolling mill, and the like, The tandem rolling mill equipment can always be maintained in an optimal operation state.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a control system of a tandem rolling mill according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a load distribution correction control unit according to one embodiment.

FIG. 3 is a conceptual diagram illustrating a membership function of a balance determination unit according to one embodiment.

FIG. 4 is an inference table diagram showing inference rules of a load distribution modification control unit according to one embodiment.

[Explanation of symbols]

100: tandem rolling equipment; 101-1 to 4: Stands # 1 to # 4 of tandem rolling mills; 110-1 to 4: work rolls; 120: speed control device; 121: reduction control device;
122: thickness control unit, 123: tension control unit, 125: thickness gauge, 126: tension meter, 130: setup control unit,
131: rolling model, 150: load distribution correction control unit, 1
51: load torque calculator, 152: rolling torque calculator,
153: load torque balance determination unit, 154: rolling torque balance determination unit, 155: output side thickness change degree inference unit, 156: output side thickness change amount determination unit, 157: output side thickness change command output unit, 200: rolled Wood.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B21B 37/00 BBP B21B 37/12 BBP (72) Inventor Toshihide Shinoda 5-2-1 Omikacho, Hitachi City, Ibaraki Pref. Inside Hitachi Omika Plant (72) Inventor Shinichi Ikeda 4976 Nomura Minami-cho, Shinnanyo-shi, Yamaguchi Nisshin Steel Co., Ltd. Shunan Steel Works Co., Ltd.

Claims (6)

[Claims] 1. A method for correcting a load distribution of a tandem rolling mill in which a thickness control is performed on all stands, wherein a rolling torque is obtained by subtracting a loss torque, an acceleration / deceleration torque and a tension torque from a motor torque converted from a motor current of each stand. A load distribution correction method for a tandem rolling mill, wherein the load thickness is optimized by changing the set value of the outlet side thickness of the stand based on the deviation between the determined rolling torque and the target value. 2. A method for correcting a load distribution of a tandem rolling mill in which a thickness control is performed on all stands, wherein a load torque is obtained by subtracting a loss torque and an acceleration / deceleration torque from a motor torque converted from a motor current of each stand. A load distribution correcting method for a tandem rolling mill, characterized in that when the load torque exceeds its rated load torque, the outlet thickness setting value of the stand is changed based on the deviation to optimize the load balance. 3. A load distribution correcting method for a tandem rolling mill in which a thickness control is performed on all stands, wherein a load torque during rolling calculated based on an electric motor current of each rolling mill and an actual value of an input side and an output side tension. From the rolling torque,
For each stand, determine the load torque deviation from the rated load and the rolling torque deviation from the rolling torque target value, respectively.
For each deviation, the balance state is evaluated by a predetermined membership function, and the degree of change of the outlet side plate thickness of the stand is determined based on the combination of the evaluation of the stand and the next stand to make the balance state appropriate. A load distribution correcting method for a tandem rolling mill, characterized in that inference is performed in accordance with the inference rule of (1), and the inference result is quantified to determine an amount of change in a set value of an outlet side thickness of each stand. 4. The inference according to claim 3, wherein the inference is always performed on the rolling torque balance, and starts when the load on each stand exceeds the rated value for the load torque balance, and both inferences are performed. A load distribution correction method for a tandem rolling mill, wherein the results are combined in such a case. 5. The apparatus according to claim 1, wherein, when changing the set value of the outlet side thickness of each stand, the change period is longer than the thickness control cycle and the response of the thickness control means is followed. A load distribution correction method comprising determining a change rate that can be changed. 6. A control device for a tandem rolling mill having a thickness control means in all stands, a means for detecting a motor current and an entrance / exit tension on each stand, Means for evaluating the load balance state between the stands based on the tension, calculating the amount of change in the outlet plate thickness set value of each stand to optimize the load balance based on the evaluation, and the outlet plate of each stand A control device for a tandem rolling mill, further comprising means for dynamically changing a thickness setting value in response to a response of said thickness control means.