JPH08197117A - Controller for continuous rolling mill - Google Patents

Abstract

PURPOSE: To control plate thickness, tension and rolling load without influencing one another by calculating the operation command quantity of a plate thickness controller from a deviation between the detected value of a detector and a set value by a setup device. CONSTITUTION: Tension and setting load between rolling mill stands are calculated by a setting-up controller 15 from plate thicknesses on the outlet sides of respective target stands 1A to 1D. Based on a calculated result, the interval of rolling rolls and the speeds of rolling mills of respective rolling mill stands from 1A to 1D are determined, and they are outputted to drawing down controllers 4A to 4D and speed controllers 5A to 5D. Controls are performed by the drawing down controllers 4A to 4D so that the interval of the rolling rolls coincides with a rolling roll interval command. In the same way, controls are performed by the speed controllers 5A to 5D so that the peripheral speeds of the rolling rolls coincide with a rolling speed command.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to rolling of a material to be rolled by a rolling mill, and relates to a controller for controlling the plate thickness and tension of the material to be rolled and the rolling load of the rolling mill.

[0002]

2. Description of the Related Art In rolling a material to be rolled by a rolling mill, a setup system for performing rolling roll intervals, speed distribution, tension setting, etc. based on a rolling schedule, and an operating point determined by the setup system, It can be classified into automatic rolling control for controlling rolling mills.

Further, automatic rolling control includes automatic sheet thickness control (AGC) for controlling the sheet thickness in the central portion in the sheet width direction of the rolled material, automatic tension control (ATR) for controlling the tension acting on the rolled material, It is divided into automatic strip width control (AWC) for controlling strip width and automatic shape control (ASC) for controlling flatness of rolled material.

In recent years, in order to improve the accuracy of rolled products, it is becoming more common to apply a plurality of functions to automatic rolling control. This is explained in detail in Chapters 11 and 12 of "Theory and Practice of Sheet Rolling" (edited by the Iron and Steel Institute of Japan). Further, a non-interference control for suppressing interference between a plurality of automatic rolling controls adapted to strip rolling has also been proposed (JP-A-62-214818).

The above-mentioned publication describes a tension adjusting method and a roll gap adjusting method by adjusting the rolling roll speed for suppressing the sheet thickness disturbance for improving the sheet thickness accuracy. Since the rolling tension and the roll gap affect each other and deteriorate the plate thickness accuracy, in the invention described in the above publication, the plate thickness change, tension change,
From the detected amount of the rolling force change, the roll gap that suppresses the disturbance of the plate thickness and the roll speed control amount are calculated.

[0006]

As described above, rolling control includes a setup system that linearly approximates the rolling phenomenon and gives an operating point of control, and an automatic control system that performs control in the vicinity of a given operating point. is there. AGC, A for automatic control system
There are various controls such as SC and ATR, and in rolling control, it is general to use some of them in combination. These controls can operate independently of each other if the operating point of the sepp-up system is correct, but it is generally difficult to give the correct operating point, and the rolling phenomenon itself is a non-linear system. It is often impossible to obtain sufficient accuracy at the operating point of. Therefore, in the automatic rolling control system, interference may occur between the applied systems. As an example of this, let us consider a rolling mill to which AGC and ATR are applied, where there is a setup failure at a set load.

If the set load given as the setup is too wide to obtain appropriate plate thickness accuracy, AGC
Tries to increase the tension to absorb the error.
However, if the tension is greater than the set value at this time, the ATR
Operates to reduce the tension. As a result, desired accuracy cannot be obtained for both plate thickness and tension. Therefore, in the current rolling control, the accuracy of the strip thickness is given priority, and the tension is
By controlling the band, the problem of interference is avoided. However, even if such a band control method is adopted, there is a problem that the control is saturated when the setup deviation is large.

For this reason, recently, an attempt has been made to improve the control accuracy by decoupling the system by applying a multivariate theory using a mathematical model of the system. However, the rolling phenomenon itself has not been fully clarified, the rolling mill itself is non-linear, and the parameters of the rolling mill and the material to be rolled change during rolling. It is impossible to give, and sufficient accuracy cannot be obtained by decoupling with a mathematical model of the system.

An object of the present invention is, in rolling by a rolling mill, interference between a plurality of control systems adapted to automatic rolling control according to the priority of control accuracy required for each control amount of strip thickness, tension and load. The purpose is to prevent the above and realize a desired control accuracy.

Further, as a means for achieving the above object, the present invention aims to construct a control system which is not affected by model uncertainty and non-linearity by using a qualitative relationship of state quantities of the system. To aim.

[0011]

In order to solve the above problems, in the present invention, a means for recognizing a deviation of each control amount of plate thickness, tension and rolling force from a set value, and a qualitative relation between each control amount. Control rule for coordinating between the control systems according to the priority order of control accuracy required for each control amount from the dynamic mutual relation, and the recognition amount as an input, and the control of each control system is performed using the control rule. It has a control calculation unit that calculates command values, controls tension and load simultaneously, and controls plate thickness and tension in coordination with each other.

[0012]

In the present invention, the deviation from the set value of the state quantity is recognized from the respective detected amounts of the plate thickness, tension and rolling force and the respective set values, and the plate thickness and the tension are coordinated from the recognized amount. By calculating the control amounts of the tension and the load for the control, the plate thickness, the tension, and the load can be controlled according to the priority order without interfering with each other.

[0013]

FIG. 1 shows an embodiment of the present invention. Rolling is performed by passing a material to be pressured between a pair of upper and lower rolling rolls 2. The rolling mill includes a rolling roll 2, a backup roll 3 for giving a rolling force to the rolling roll 3, a speed controller 5 for controlling the rotation speed of the rolling roll 2, a rolling roll 2
Control device 4 for controlling the interval between the rolls, and a load detector 7 for detecting the rolling force as a load that is a reaction force of the rolls.
The rolling mill stand 1 is configured with the above as one set. Figure 1
A four-stand continuous rolling mill in which four pairs of rolling mill stands are arranged in series is shown, and reference numerals 1 to 7 are shown with suffixes A to D corresponding to the 1 to 4 stands.

The rolling mill has rolling stands 1 to 4 and a payoff reel 9 for feeding the rolled material to the rolling mill stand 1.
And a tension reel 10 for winding the rolled material. A plate thickness gauge 6 and a tensiometer 8 are generally used as detectors attached to the rolling mill. In this embodiment, the No. 1 stand entrance side plate thickness gauge 6A on the 1 stand 1A entrance side, the No. 4 stand exit side plate thickness gauge 6B on the 1 stand 1A exit side, and the No. 4 exit side plate thickness gauge on the 4 stand 4A exit side 6
C is tension meter 8A between No. 1 stand and No. 2 stand between 1 stand 1A and 2 stand 1B, and tension meter 8B between No. 2 stand and No. 3 stand between 2 stand 1B and 3 stand 1C. No. between stand 1C and 4 stand 1D.
It is assumed that a tensiometer 8C between 3 stands and No. 4 stands is attached.

When rolling is performed, first, the setup control device 15 determines the tension between the rolling mill stands and the set load from the target delivery side plate thickness of each stand (1A to 1D) (referred to as the delivery side plate thickness setting value). It calculates and determines the space | interval of the rolling roll 2 and the rolling mill speed of each rolling mill stand 1A-1D based on it, and outputs them to the rolling-down controllers 4A-4D and speed controllers 5A-5D. Roll-down control devices 4A to 4D
Performs control so that the distance between the rolling rolls 2 matches the rolling roll distance command. Similarly, the speed control devices 5A to 5D
Performs control so that the peripheral speed of the rolling roll 2 matches the rolling speed command.

In rolling, the plate thickness is controlled by changing the tension applied to the rolled material before and after the rolling mill stand 1 or by changing the interval between the rolling rolls to change the rolling pressure applied to the rolled material. . In this case, with respect to the tension, the fluctuation of the tension becomes larger when the entrance tension of the rolling mill stand is changed, so that the rolling roll peripheral speed of the rolling mill stand i at the preceding stage is usually operated. No.i stand ~ No. (i +
1) When considering the tension between stands, the tension is changed by operating the rolling roll peripheral speed of the No. i stand or by operating the rolling roll interval of the No. (i + 1) stand. For example, when it is desired to change the delivery side plate thickness of the No. 4 rolling mill stand 1D, the interval between the rolling rolls 2D of the No. 4 rolling mill stand 1D is changed, or the circumferential speed of the rolling roll 2C of the No. 3 rolling stand 1C is changed. By changing the tension between No. 3 stand and No. 4 stand to change the delivery side plate thickness of No. 4 rolling stand 1D.

From the above viewpoints, No. 1 is used as automatic rolling control for strip thickness and tension of a 4-stand continuous rolling mill.
The No. 1 stand pressure reduction F.FAGC11 which controls the No. 1 strip stand outlet side plate thickness by operating the interval of the rolling rolls 2A using the detection signal of the entrance side plate thickness gauge 6A of the 1 rolling stand 1A , And No. 1 rolling stand outlet side plate thickness gauge 6B is used to operate the interval between the rolling rolls 2A to control the No. 1 rolling mill stand outlet side plate thickness in a monitor manner. , No. 4 Rolling mill stand 1D, using the detection signal of the output side plate thickness gauge 6C, N
o.3 No. 4 stand speed monitor AGC13, No. 4 that controls the peripheral speed of the rolling rolls 2C of the rolling mill stand 1C to control the outlet thickness of the No. 4 rolling mill stand 1D in a monitor manner.
Using the detection signal of the rolling mill stand 1D delivery side plate thickness gauge 6C, the spacing between the rolling rolls 2D of the No. 1 rolling mill stand 1D is operated to control the No. 4 rolling mill stand 1D delivery side plate thickness in a monitor manner. .4 Stand pressure reduction monitor AGC16, N
O.i to No. (i + 1) rolling mill stands (i = 1 to 3) between tension gauges 8A to 8C are used to detect No. i rolling mill stands (1A to 1C) rolling rolls 2A to 2C peripheral speeds. By using PI control to control the tension between No.i to No. (i + 1) stands between stands ATR 14A to 14C.
However, this configuration is for this embodiment, and various other configurations are possible.

Now, let us consider the problem in the case where the output side plate thickness control of the No. 4 rolling mill stand 1D is performed only by the No. 4 stand speed monitor AGC. At this time, the No. 4 stand speed monitor AGC13 is controlling in the vicinity of the set speed given by the setup, and the ATR 14 between No. 3 and No. 4 stands is a band of the set value to which tension is applied. It is assumed that the limit control that is put inside is being performed. Here, consider a case where the spacing between the rolling rolls 2D of No. 4 stand 1D is too narrow to obtain the required plate thickness due to a setup error. This situation is
Since the rolling phenomenon is not completely understood in the setup control system and the state changes during rolling, this is a phenomenon that is likely to occur in the setup control performed only once before the start of rolling. At this time, No. 4 stand speed monitor A
The GC 13 increases the circumferential speed of the rolling roll 2C of the No. 3 stand 1C and decreases the tension between the No. 3 to No. 4 stands, thereby increasing the No. 4 stand 1D delivery side plate thickness,
Try to bring the actual plate thickness closer to the set plate thickness. However, No.
If the 3-roll 1D rolling roll interval is too narrow, the control amount of No. 4 stand speed monitor AGC becomes too large.
o.4 Stand 1D No. 3 before the outlet plate thickness reaches the set value
~ No.4 Stand ATR14C exceeds the lower limit bandwidth, ATR
13 begins to work. At this time, the output of AGC 13 and ATR
The outputs of 14 cancel each other out, and sufficient control accuracy cannot be obtained with the former.

Next, as shown in FIG. 1, it is considered to solve the above-mentioned problem by adding a reduction monitor AGC to the No. 4 stand.

FIG. 2 shows the mutual relationship between the rolling load P of the No. 4 stand 1D and the reduction roll 2D, the tension T between the No. 3 to No. 4 stand, and the No. 4 stand delivery side plate thickness h. It is shown by the deviation from the set value. In the figure, the load deviation ΔP is positive (ΔP> 0), and the tension deviation is ΔT <
Consider a state where 0 and the plate thickness deviation are Δh> 0. As a method of reducing the plate thickness deviation from this state, either increasing the rolling load P or increasing the entrance tension T can be considered. When the rolling load is increased, the exit side plate thickness is reduced due to the increasing rolling load. Further, the tension is reduced because the plate thickness is reduced (state). As a result, in the state, the sheet thickness deviation Δh decreases with an increase in the rolling load, but the tension deviation ΔT increases. On the other hand, when the entry side tension is increased, the plate thickness is reduced due to the increase in tension (state). (The rolling load also decreases due to the reduction of the plate thickness, but it is negligible here because it is a small value.) Further, like the state, in the state of ΔP <0, ΔT> 0, Δh> 0, On the contrary to the above example, the tension deviation and the plate thickness deviation can be made close to zero by increasing the rolling load (state). On the other hand, when the tension is increased from the state (1), the plate thickness deviation decreases, but the tension deviation increases (state).

From the above, regarding the tension between No. 3 to No. 4 stands described above, the No. 4 stand speed monitor AG
Consider a case where interference occurs between the C13 and the ATR 14 between the No. 3 and No. 4 stands. Using the same expression as in FIG. 2, this state is shown like the state in FIG. FIG.
2 is equivalent to the case where the signs of the values in the state of FIG. 2 are reversed. Therefore, contrary to the state of FIG. 2, by reducing the rolling load, the deviation of the tension and the plate thickness can be reduced (see FIG. 3).
State).

According to this method, the tension and rolling load are controlled not only in the state where each value is on the control limit but also in any rolling state, so that the deviations of both the plate thickness and the tension converge to zero. It is possible to control the direction.

The plate thickness due to the tension and rolling load described above,
The tension control is hereinafter referred to as cooperative control for simplicity. In this embodiment, a method using fuzzy control is shown as a means for realizing cooperative control.

The fuzzy control is a method that enables control using a rule that is not clearly quantified such as the experience of an expert or a qualitative procedure, and is used to realize the control shown in FIG. It can be said that it is suitable. FIG. 4 shows a control flow of cooperative control using fuzzy control.
In FIG. 4, the input actual detection values of the rolling load P, the tension T, and the strip thickness h are compared with the respective set values P ₀ , T ₀ , and h _0, and are output as deviations to the element inference unit 27. Element inference unit 2
In 7, a membership function for fuzzifying a predetermined non-fuzzy amount is used to calculate the certainty factor indicating the degree of deviation from the set value for each amount from the deviations of rolling load, tension and strip thickness. In the fuzzy inference unit 28, the element inference unit 27 is used by using a predetermined fuzzy inference rule.
The control output is calculated from each of the certainty factors calculated in. Here, as the control output in this embodiment, the plate thickness control gain by the entrance tension, that is, the No. 4 stand speed monitor is used.
It is the amount of change in the AGC control gain α _s and the plate thickness control gain due to rolling load, that is, the gain α _g of the No. 4 stand reduction monitor AGC. The fuzzy inference unit 28 uses the fuzzy inference rule unit in which the qualitative control law described in FIG. 3 is converted into a fuzzy rule, and the certainty factor of the degree of change in each gain obtained by the fuzzy inference to determine the actual amount of change in gain. It consists of a non-fuzzy part that calculates.

FIG. 5 shows an apparatus for performing cooperative control.
FIG. 5 is a diagram in which the last two stages are taken out from the entire configuration of FIG. 1 and rewritten in detail.

The tension T between No. 3 to No. 4 stands is detected by the tensiometer 8C, and the element inference unit 27 and No. 3 to N.
o.4 Input to the ATR14C section of the stand. The No. 4 stand rolling load P is detected by the load cell 7D, and the element inference unit 2
7 and the reduction device 4D. Further, the No. 4 stand outgoing side plate thickness h is detected by the plate thickness gauge 6C and input to the element inference unit 27 and the No. 4 stand pressure reduction monitor AGC16. The element inference unit 27 calculates the certainty factor of the deviation of the actual detection values and the set values of the plate thickness, tension, and rolling load input from the setup controller 15, and outputs them to the fuzzy inference unit 28. In the fuzzy reasoning section, the element reasoning section 2
The control gain α _s of the No. 4 stand speed monitor AGC 13 and the control gain α _g of the No. 4 stand pressure monitor AGC 16 are calculated from the certainty factors input from 7. However,
It is necessary that α _s and α _g satisfy the relation of α _s + α _g = 1. N
o.4 Stand reduction monitor AGC16 determines the rolling load command from the sheet thickness deviations Δh and α _g and outputs it to the reduction control unit 40.
Plate thickness is controlled by reduction. In addition, the No. 4 stand speed monitor AGC13 determines the No. 3 stand speed command from Δh and α _s and outputs it to the speed control unit 5C, and controls the No. 3 stand speed to control the No. 3 to No. 4 stand. The tension is controlled to control the plate thickness.

Next, details of the element inference unit 27 will be described. FIG. 6 is an example of a membership function forming the element inference unit 27. Inputs to the element inference unit 27 are actual detection values and set values of sheet thickness, tension and rolling load. Each detected value is compared with each set value, and the degree of certainty smaller than the set value, the degree equal to the set value, and the certainty degree larger than the set value are calculated. As an example, consider the plate thickness. When the actual detected plate thickness is h _{1 as} shown in FIG. 6, the certainty factor HN with a negative plate thickness deviation is a _N , and the certainty factor HZ with a zero plate thickness deviation is a _z , which is positive. Certainty H
P is calculated to be 0. The same applies to the tension and the rolling load, and the confidences of the positive tension deviation, the zero tension deviation, and the negative tension deviation are TP, TZ, and TN, and the rolling deviation is positive and zero. Certain degrees of certainty and negative degrees are indicated by PP, PZ, and PN.

Next, details of the fuzzy inference unit 28 will be described. First, FIG. 7 shows a control procedure which is the basis of the fuzzy inference rule. In the figure, the + symbol indicates that the state quantity, that is, the plate thickness, rolling load, and tension are larger than the set values. In addition, ± indicates a case of zero and − indicates a case of negative. In FIG. 7, for example, the state in which the plate thickness is + and the load is + tension is − is the same as the state in FIG. 2, and as shown in FIG. You can turn it to zero.

In this embodiment, as a method for realizing this operation, a method of making the ratio of plate thickness control by tension larger than the ratio of plate thickness control by load (corresponding to symbol T> P in the figure) is adopted. .

A fuzzy inference rule for performing cooperative control from the control procedure of FIG. 7 is given as shown in FIG. In the figure,
HP, PP, etc. in the antecedent part are the certainty factors obtained in the element inference part. Further, the consequent part indicates the certainty factor of the magnitude of the gain α _s , and SB, SM, and SS indicate that the certainty factor of the degree of α _s is large, medium, and small, respectively. .

Fuzzy reasoning is generally IF-THEN-
It is expressed in the form of. The inference rule of FIG. 8 is set to IF-THE
In the N-type, for example, when the plate thickness is HP, the tension TP, and the rolling load is PN, IF (plate thickness deviation is positive) (HP) & (tension deviation is positive) (TP) &
(Negative rolling load) (PN) THEN (reduce α _s ) (SS). In the present embodiment, the rules are determined for the 27 ways shown in FIG. 7, and for each, S
B, SM, SS are calculated. These calculated certainty factors are defuzzified, and the magnitude of the gain α _s is calculated as a control output. At this time, α _g is calculated using α _s from the relationship of α _s + α _g = 1.

The above control implicitly gives priority to the plate thickness accuracy. However, in the rolling process, tension may be prioritized over strip thickness. In such a case, in the cooperative control, the fuzzy inference rule of FIG. 8 is modified as shown in FIG.

[0033]

As described above, according to the present invention,
The plate thickness, tension, and rolling load that affect each other can be controlled independently without using an accurate model. Also, the plate thickness,
It is possible to prioritize the control accuracy of tension and load and to control them cooperatively according to the priority.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing a qualitative relationship among rolling load, tension, and plate thickness.

FIG. 3 is a diagram showing an example of cooperative control.

FIG. 4 is a diagram showing a control flow of cooperative control.

FIG. 5 is a diagram showing an example of a configuration of plate thickness tension cooperative control.

FIG. 6 is a diagram showing a configuration example of an element inference unit.

FIG. 7 is a diagram showing an example of a control procedure of cooperative control.

FIG. 8 is a diagram showing an example of a fuzzy inference rule for cooperative control.

FIG. 9 is a diagram showing a fuzzy inference rule when tension is prioritized.

[Explanation of symbols]

1 ... Rolling mill stand, 13 ... No.4 stand speed monitor AGC, 14C ... ATR between No.3 and No.4 stands, 1
5 ... Setup control device, 19 ... Rolling load / tension cooperative control device, 27 ... Element inference unit, 28 ... Fuzzy inference unit.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B21B 37/00 8315-4E B21B 37/00 113 C 37/12 BBP (72) Inventor Hiroshi Saito Ibaraki 5-2-1 Omika-cho, Hitachi City, Hitachi, Ltd. Inside the Omika Plant, Hitachi Ltd. (72) Inventor Masaaki Nakajima 5-2-1, Omika-cho, Hitachi City, Ibaraki Prefecture (72) Inventor at Omika Plant, Hitachi Ltd. Kyata Katayama 7-1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi, Ltd. Hitachi Research Laboratory

Claims (1)

[Claims] 1. A plate thickness control device for a material to be rolled by a rolling load of a rolling roll of a target rolling mill and a tension of the material to be rolled between the rolling mill and a rolling mill at a stage before the rolling mill. There is a setup control device that determines the set value of the plate thickness, the rolling load, and the tension, and a detection device for each of the plate thickness, the tension, and the rolling load, and a detection value of the detection device. And a rolling mill control device capable of calculating the operation command amount of the strip thickness control device from the deviation of the set value by the setup device and controlling the strip thickness, the tension, and the rolling load without affecting each other.