JPH0688058B2 - Adaptive control method in rolling mill - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a rolling mill control method, and more particularly to an adaptive control method for a rolling mill control device.

[Background of the Invention]

In the conventional method, for example, the rolling load is predicted by the following formula.

However, P _C i: rolling load (predicted) value Kfi (kp); average deformation resistance, kp is a deformation resistance parameter and is requested to the steel grade.

bt; Strip width Ri '; Flat roll radius Δhi; Reduction amount Qi (μ); Reduction function and friction coefficient μ.

(Note that the subscript i indicates the i-th stand. The same applies below.) The rolling load P _C i (kp, μ) predicted by Eq. (1) is accompanied by an error in the parameters kp and μ, and is therefore the calculated value P _C i. The measured values P _A i do not always match, and usually show considerable variations.

On the other hand, in the method described in Japanese Patent Publication No. 49-2273, the measured value
P _A i is always compared with the calculated value P _CA i, and P _C i according to equation (1) is used.
Is described while correcting as follows.

Pi ＝ Zi ・ P _C i (2) However, Pi: Rolling load P _C i: Rolling load calculation value by the formula (1) Zi: Load correction coefficient Then, this is usually exponentially smoothed and used as Zi = Zi ⁻¹ + δ (Z _A i −Zi ⁻¹ ).

However, in the above method, since the prediction error of the deformation resistance and the prediction error of the friction coefficient are not separated, it is not possible to use Zi that has been used until now for materials of different steel types (that is, different kp). There are problems such as not being able to do so, and it is clear that this is not a sufficient adaptive correction method.

[Object of the Invention]

An object of the present invention is to provide a highly accurate adaptive control method that solves the above problems.

[Outline of Invention]

As the rolling load P _C i is shown by the equation (1), the deformation resistance parameter kp and the friction coefficient μ are included. Advanced rate f _C i
Also includes kp and μ as in the following expression (3).

Where ri: Reduction ratio μi: Coefficient of friction hi: Plate thickness on the delivery side Ri: Work roll radius tfi: Front unit tension Sfi (kp): Deformation resistance at the delivery side (including parameter kp) tbi: Rear unit tension Sbi (kp ): Incoming deformation resistance (including the parameter kp) Here, the equations (1) and (3) can be transformed into the following by linear approximation in the vicinity of the reference value (subscript i is omitted for simplicity). ).

However, Is a partial differential of P _P , f _P with kp, μ. P _C0 and f _C0 are values obtained by directly calculating the equations (1) and (3). Δkp,
Δμ is the error. Using the plate speed detected by the high-accuracy plate speed meter installed on the output side of the rolling mill, using the plate thickness measured with high accuracy by mass flow measurement, the above P _C0 , f _C0 and Can be calculated with high precision. Furthermore, the actual P _A of rolling load measured by a rolling pressure gauge, a roll circumferential speed actual v
By calculating the advanced rate performance f _A from _RA vo _A : Actual value of plate speed It can be obtained by solving Δkp, Δμ as unknowns of the simultaneous equations of two elements using the above (4) and (5). As a result, it is possible to separate the error of kp and μ which could not be separated in the conventional method, and by adaptively correcting this error in the next set-up calculation, it is possible to realize better adaptive correction than the conventional one. This is a feature of this method.

Example of Invention

The present invention will be described by way of examples shown in the drawings. FIG. 1 shows an example in which the present invention is applied to a single stand mill, and each rolling mill comprises a pair of work rolls (A) and a back up roll (B). A device that controls the roll opening [1
1], device for controlling rolling roll speed [12], detector for detecting roll peripheral speed [13], plate thickness detector [4], plate speed detectors [15], [16], rolling load detector [17] is provided.

(1) Setting S and N (setting calculation) Based on the rolling command, S and N are calculated by the setting calculation device SET, and the set values are respectively set to the roll opening control device [1] and roll speed control device [12]. Set to. The set values S and N in this case are the predicted loads calculated by the rolling load prediction formula {(1) formula} described above.
Like P _C (kp, μ), the advanced rate f _C (k
p, μ) and calculated from the following formula To be done. Here, h is the target plate thickness on the delivery side K: Spring constant R: Work roll radius v _OF : Set plate speed on the delivery side. With this set value, P _C (kp, μ) and f _C (kp, μ) predicted to roll the applicable material, the actual load P _A measured by the detector [17], and the detector [15] Calculated from equation (6) from actual plate v _OA and roll peripheral velocity v _RA measured from [13]
It should match f _A , but it doesn't. It is considered that there is an error in the parameters Kp, μ included in the model of P _C , f _C , and the true value of each is expressed as Kp ^* , μ ^{* by the} following equation.

kp ^* = kp + Δkp (9) μ ^* = μ + Δμ (10) This Δkp and Δμ are calculated by the adaptive control calculation unit CAL in FIG.

(2) Calculation of adaptive correction coefficients Zk and Zμ.

Measured value obtained from the detector (Subscript A indicates the measured value.) As the measured value taken into the CAL device, from the output side plate thickness meter [14] h _{A From the} output side plate speed meter [15] v _OA Input side plate speed Vi _A from total [16] v Roll roll speed detector (13) v _RA Load detector (17) has P _A From the same mathematical model {ie (1) and (2)} calculated by SET, we obtain P _CA (kp, μ) and f _CA (kp, μ)
To calculate. Here, kp and μ use the same value as predicted by SET. Substitute the measured values P _A , f _A and the above P _CA , f _CA into the formulas (4) and (5) instead of P _C , f _C and P _C0 , f _C0 , respectively. If you also calculate The errors Δkp and Δμ can be obtained. Here, the matrix A is given by the following equation (13).

In equation (13), Pc = Pc _A , fc = fc _A , kp = kp, μ =
is μ. From the errors obtained from Eq. (12), (9) and (10)
The actual kp ^* and μ ^* are calculated using the formula, and each normalized correction coefficient And the correction coefficients Zk and Zμ in the next set-up calculation are obtained by using a known exponential smoothing method.

Zk = Zk ⁻¹ + δk (Zk _A −Zk ⁻¹ ) (16) Zμ = Zμ ⁻¹ + δμ (Zμ _A −Zμ ⁻¹ ) (17) where δk and δμ are smoothing gain 0 <δk <1.0 , 0 <δμ
<1.0, Zk ^-1 , Zμ ^-1 indicates the correction coefficient used last time.

Zk and Zμ obtained in (16) and (17) are sent from CAL to SET, which performs the next set-up calculation, and adaptive correction can be performed. In SET, Here, Ω means supplementary steel cord, and Ω ^-1 indicates the type of steel rolled last time. kp ^Ω is the nominal value of the first piece of steel that has changed. μ ^O
Is a nominal value corresponding to the type of rolling oil.

In ordinary rolling, the change in μ is a parameter unique to the mill unless the rolling oil or the like is replaced, and this method converges to a value unique to the mill and stabilizes. Therefore, the original deformation resistance error is detected, and good adaptive control can be realized as compared with the conventional method.

An embodiment in which the present invention is applied to a tandem mill is shown in FIG.

FIG. 2 shows an embodiment in which the present invention is applied to a continuous rolling mill having six rolling stands A, B ... F. Each rolling stand has a pair of rolls 1 for controlling the roll opening thereof, an electric motor 3 for driving the rolls 1, a speed control device 4, a roll speed detector 5, a rolling load detector 6 and a plate speed detector. Is provided. The subscripts A, B, ... F in the figure indicate the corresponding rolling stands.

The roll opening control device 2 receives the rolling-down position signal (S ₁ ) (Si) (S ₆ ) and the final stand (F) given by the computer.
It is composed of an automatic control system that controls the roll opening of each rolling stand based on the thickness deviation signal obtained from the finish plate thickness detector (TM) installed on the exit side of the.

Tension detectors (Rab), (Rbc), (Ref) for detecting the tension of the material are installed between the rolling stands, and signals from this loop detector are combined circuits (ORa), (ORb), ( OR
via f) to the speed control device 4 of the respective rolling stand. A roll speed setting signal (N ₁ ) ... (Ni) ... (N ₆ ) is given to each control device 4 from a computer, and the roll of the rolling stand is compared with the signal from the tension detector. Control the number of rotations. That is, an automatic speed control system is configured.

Both automatic plate thickness and automatic speed control systems have been used in the past, but such control systems have a limited control range, and if the set value is not appropriate, the specified operating conditions are not satisfied. Some are as described above.

When the adaptive control device according to the present invention is applied to the continuous rolling mill having this double-sided control system, it becomes as follows.

First of all, using the predictive calculation device (SET), the thickness of the material at the entrance side of the rolling mill, the composition, the width, the finishing thickness of the rolling specifications,
Considering the exit speed, roll radius, roll opening zero point, and other rolling conditions, the rolling position (Si) and roll speed of each stand (Si) required to obtain the required finished plate thickness in an ideal power distribution state ( Ni) is calculated using the following equations (20) and (21) and the above equation (1), and this setting signal is output through the output devices (OUT1) and (OUT2) respectively to the roll opening control device 2 And to the speed control device 4.

However, Ni; roll speed of the i-th stand N _F ; roll speed of the final stand Ri; roll radius of the i-th stand R _F ; roll radius of the final stand hi; exit plate thickness of the i-th stand h _F ; Finishing thickness fi; Advanced rate of i-th stand f _F ; Advanced rate of final stand However, Si; the rolling position of the i-th stand P _C i; rolling load of the i-th stand Ki; mill rigidity of the i-th stand S _O i; zero point of the roll opening of the i-th stand, and equation (21) holds. Numerical value Si-S _O i; unloaded reduction position Each rolling stand is rolled based on this setting,
Disturbances such as roll opening zero point and rolling load prediction error do not always lead to a satisfactory rolling state, and when the setting error exceeds a certain range, the tension detector (R) operates and the roll rotation speed changes.

When there is no change in the roll rotation speed, the measured value (N _A i) of the roll rotation speed is measured by the rotation speed detector 5, and the plate thickness deviation is measured by the finishing plate thickness detector (TM). System 7
Detected by. These pieces of information are given to the calculator (CAL1), and the inter-stand plate thickness (h _A i) is calculated by the equation (22), However, h _AF ; Measured value of finished plate thickness v _AF ; Measured value of final stand exit side plate speed v _A i; Measured value of stand exit side plate speed Also, according to equation (1), (P _CA i) is _{calculated according to} equation (3) ( f
_CA i) is calculated as (f _A i) by the equation (23).

However, v _A i; i stand output side plate speed actual value v _A i; i stand roll rotation number Ri; i stand roll radius Also, from P _CA i and P _A i, f _CA i and f _A i From equation (12) The error amount ΔkpiΔμi of each stand can be obtained.

From this simultaneous equation, ΔkpiΔμi can be obtained, and from this,
The correction coefficient Zki, μi is obtained in the same manner as in the first embodiment and is given to the prediction calculation device (SET).

CP1 calculates these correction coefficients Zki, μi.

In the present invention, in the conventional method, the error is separated and the error relating to the deformation resistance that has not been handled and the error relating to the friction coefficient are clearly separated and corrected, so that the effect becomes remarkable especially when the steel type of the rolled material changes. Appears. FIG. 3 shows the effect obtained in the cold tandem mill. The lower graph of FIG. 3 shows that the thickness deviation of the plate tip portion is within ± 5% as a result of adopting this method. On the other hand, when the conventional method is adopted, the deviation between the actual load and the predicted load is large when the steel type is changed (A → B) as shown in the upper graph of FIG. 3, and as a result, the plate thickness deviation is greatly affected. It is clear that this method is excellent.

It can be seen from FIG. 3 that the effect of this method is effective not only when the steel type changes but also when a large schedule change is performed even when rolling the same steel type (scheduler a → b in the figure). When changing). This is due to the thickness detection error of each stand due to the fact that the thickness detector cannot be installed in all stands in a tandem mill.In the conventional method, these detection errors are calculated and represented by a single correction coefficient. Therefore, if rolling of the same schedule is continued, it is good, but if there is a change to a large schedule, adverse effects will occur.

Furthermore, in this method, since both the load model and the advanced rate model are adaptively modified as adaptive correction targets, the correct advanced rate in the original sense is predicted at the time of set-up calculation, and the roll peripheral speed setting value better than the conventional method is set. Is obtained, and as a result, it is possible to improve the plate thickness accuracy.

〔The invention's effect〕

According to the present invention, an accurate plate thickness can be obtained even if there is a difference in steel type or a large change in schedule.

[Brief description of drawings]

FIG. 1 shows Example 1 in which the present invention is applied to a single stand mill. FIG. 2 shows Example 2 in which the present invention is applied to a 6-stand tandem mill. FIG. 3 is a graph showing a comparison between plate thickness accuracy and a conventional method when the present invention is applied to a cold stand dem mill. 1 ... Roll, 2 ... Device for controlling the opening degree of roll 1,
3 ... motor for driving roll 1, 4 ... speed control device, 5 ... roll speed detector, 6 ... rolling load detector, 7 ... plate speed detector, TM ... plate thickness detector, R ... Tension detector, ES ... Prediction calculation device, OR ... Synthesis circuit, OUT ...
… Setting signal output device, CAL …… Calculator, CP …… Comparator, 11 …… Roll opening setting device, 12 …… Roll speed setting device, 13 …… Roll peripheral speed detector, 14 …… Plate thickness detection Bowl, 15
…… Plate speed detector (outgoing side), 16 …… Plate speed detector (incoming side),
17 …… Load detector, SET …… Set-up calculator, CAL
…… Adaptive correction coefficient calculator, A …… Work roll, B…
Back-up roll, C ... Rolled material.

Claims (1)

[Claims] 1. An adaptive control method for a rolling mill, comprising a device for detecting the strip speed of a rolled material provided on the outlet side of the rolling mill, wherein the strip speed is detected and the strip thickness immediately below the roll of the strip is set to a constant mass flow rate. The first step obtained from the relationship, the second step obtaining the advanced rate (f _A ) from the strip speed and the roll peripheral speed of the rolling mill, and the third step measuring the load (P _A ) of the rolling mill From the step and the plate thickness of the first step, the load (P) and the advance rate (f) are calculated by a mathematical model, and the deformation resistance and the friction coefficient are developed as parameters in the vicinity of this calculation result. Primary influence coefficient 5th step for obtaining the error of the deformation resistance and friction coefficient from the 4th step for obtaining the load, the measured value of the load (P _A ) and the advance rate (f _A ) and the calculated value of the 4th step
And the deformation resistance and the friction coefficient error obtained by the first to fifth steps are used to correct the model of the load and the advanced rate, the adaptive control method in the rolling mill.