JPH08323408A - Method and device for avoiding abnormal rolling state in tandem mill - Google Patents

Abstract

PURPOSE: To automatically avoid the unstable phenomenon of operation such as the variation in thickness and defects in shape of a product by judging the abnormal state of a rolling mill, estimating the factor of occurrence of abnormality and automatically correcting the state of control based on the estimating result. CONSTITUTION: The high-speed Fourier transformation of the thickness on the outlet side of the rolling mill 1 and time series data of the variation in interstand thickness and variation in interstand tension is executed with a frequency analyzer 10. The abnormal state of each measured value is judged according to the difference between each power spectrum and each threshold value determined from the present rolling speed with an abnormal rolling state judging device 11. The factor of the occurrence of the abnormal state and its degree are estimated from the degree of coincidence of the mutual juged results of abnormality and each power spectrum of the variation in the thickness on the inlet side and variation in rolling load and rolling speed with an abnormality occurrence factor estimating device 12. Control function that is the object of excess and deficiency of the state of control is judged from the rule of thumb with a control-state correcting/judging device 13. A control parameter or a control signal command value of the object control function is corrected with a rolling controller 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for avoiding an abnormal rolling state in a tandem rolling mill, and more particularly to a method and a method for realizing stable operation of the rolling mill while minimizing fluctuations in product sheet thickness in the tandem rolling mill. Regarding the device.

[0002]

2. Description of the Related Art Conventionally, in a tandem rolling mill such as a cold continuous rolling mill, when an abnormal variation in the finished sheet thickness appears, attention should be paid to the periodicity of the sheet thickness variation in identifying the cause of the abnormal variation. , The frequency is compared with the frequency of fluctuation factors such as the rotation speed of each roll.

[0003]

However, in the past, this work relied on human labor, so it took a considerable amount of time to identify the cause, and the amplitude of the abnormal fluctuation was small at the initial stage of the abnormality, so it was visually inspected. There was a problem in taking prompt action, such as difficulty in confirmation. Note that, for example, Japanese Patent Application Laid-Open No. 5-200421 proposes a system for automatically determining a factor of variation in the finished plate thickness, but it is limited to the identification of the factor of abnormality occurrence, There was a problem that it could not be avoided directly.

The present invention solves the problems of the prior art described above, and after determining the abnormal state, automatically corrects the control state based on an empirical rule to avoid the abnormal rolling state of the tandem rolling mill. It aims at providing the method and apparatus which do.

[0005]

Means for Solving the Problems The present invention measures the plate thickness on the entrance and exit sides of each stand and the inter-stand tension, the rolling load and roll speed of each stand of a tandem rolling mill equipped with a plurality of stands, A method for avoiding an abnormal rolling state in a tandem rolling mill equipped with a control system for controlling the strip thickness between the stands and the rolling mill exit side, the tension between the stands, and the rolling speed. And the difference between each power spectrum of the fluctuation of tension between stands and each threshold value determined from the current rolling speed to determine whether or not there is an abnormal state in each measured value. The band and the degree of its abnormality are determined, and the degree of coincidence between the determination results of the abnormal state and the power spectra of the inlet side plate thickness change and rolling load change and the rolling speed The factor and the degree of the abnormal state occurrence are estimated using an empirical rule from the authors, and the control function that is the target of the excess or deficiency of the control state is determined from the empirical rule based on the estimation result of the factor causing the abnormal state. A method for avoiding an abnormal rolling state in a tandem rolling mill, which is characterized in that a control parameter or a control command value is corrected.

Incidentally, it is preferable to add the degree of change of the rolling state due to the correction of the control parameter or control command value of the target control function to the estimation of the cause of the occurrence of the abnormal state, and the plate thickness between all stands or some stands. It is better to use the predicted plate thickness obtained by calculation. Further, the present invention is a tandem rolling mill equipped with a plurality of stands, a plate thickness gauge for measuring the plate thickness between the entrance and exit sides and stands, a tensiometer for measuring the tension between each stand, and a rolling load for measuring each stand rolling load. It has a gauge and a roll speed detector that detects the rolling speed of each stand, and it also controls a strip thickness control device that controls the strip thickness between stands and the rolling mill exit side and a tension control device that controls the tension between stands and the rolling speed. A device for avoiding abnormal rolling conditions in a tandem rolling mill equipped with a speed control device for controlling high speed by inputting time series data from the above-mentioned entrance / exit plate thickness gauge, stand thickness gauge, tensiometer, and rolling load gauge. A frequency analysis device that converts into a power spectrum by Fourier transform,
An abnormal rolling state determination device that determines whether there is an abnormal state of the rolling mill from the power spectrum of the plate thickness and tension obtained by the frequency analysis device, an abnormal rolling state determination result by the abnormal rolling state determination device, and the frequency An abnormality occurrence factor estimation device that estimates an abnormality occurrence factor of the rolling mill from the power spectrum of the inlet side plate thickness and rolling load from the analysis device and the rolling speed detected by the roll speed detector, and the abnormality occurrence factor estimation device In the control state correction determination device for determining the control function and the correction amount that requires the correction of the control state from the abnormality occurrence factor estimation result in, and the plate thickness of each stand based on the correction signal from the control state correction determination device and Tension between stands,
A rolling mill control device for controlling rolling speeds, respectively, and an abnormal rolling state avoidance device for a tandem rolling mill.

[0007]

[Operation] According to the method and apparatus of the present invention, by comparing the power spectrum of current strip thickness fluctuation and tension fluctuation with the power spectrum of strip thickness fluctuation and tension fluctuation in good rolling condition, The determination of the degree of the abnormal state is obtained, it is possible to estimate the abnormality occurrence factor by acting the degree of coincidence between the abnormality determination result and other changes in the actual rolling value to the estimation logic consisting of empirical rules, The control function that requires the correction of the control state is specified by acting the abnormality occurrence factor estimation result on the judgment logic based on the empirical rule, and the rolling mill is automatically corrected based on the result. It becomes possible to automatically shift the abnormal state of No. 2 to a good rolling state.

Further, if the degree of change of the rolling state due to the correction of the control state is added to the estimation of the cause of the abnormality, it is possible to immediately judge whether the correction of the control state is good or not. The transition to can be accelerated. Further, if the inter-stand plate thickness variation is predicted using a model, it is possible to shift to a good rolling state without necessarily requiring the measured value, that is, the measuring device.

[0009]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic diagram showing the overall configuration of an embodiment of the present invention. In the figure, 1 is a rolling mill,
The stands 1a to 1d each include a pair of upper and lower work rolls 2 and 2 and a pair of upper and lower backup rolls 3 and 3, respectively. Reference numeral 4a is an entrance side plate thickness gauge provided on the entrance side of the stand 1a, 4b to 4d are inter-stand plate thickness gauges provided between the stands 1a to 1d, and 4e is an exit side plate thickness gauge provided on the stand 1d exit side. 5a to 5c are tensiometers provided between the stands, 6a to 6d are rolling load meters provided to the stands 1a to 1d, and 7a to 7d are the stands 1a to 1
It is a roll speed detector provided in d.

Numeral 10 is the entrance side plate thickness gauge 4a and the stand-to-stand plate thickness gauge 4
This is a frequency analysis device for inputting time series data from b to 4d, delivery side plate thickness gauge 4e, tensiometers 5a to 5c, and rolling load gauges 6a to 6d and converting it into a power spectrum by fast Fourier transform. Reference numeral 11 is an abnormal rolling condition determination device that determines an abnormal condition of the rolling mill 1 from the power spectrum of the plate thickness and tension obtained by the frequency analysis device 10.

Reference numeral 12 denotes the abnormal rolling state determination result by the abnormal rolling state determination device 11, the power spectrum of the inlet side plate thickness and rolling load from the frequency analysis device 10, and the rolling speed detected by the roll speed detectors 7a to 7d. This is an abnormality occurrence factor estimation device that estimates an abnormality occurrence factor of the rolling mill 1 from the above. Reference numeral 13 is a control state correction determination device that determines the control function and the correction amount that require the correction of the control state from the abnormality generation factor estimation result of the abnormality generation factor estimation device 12.

Reference numeral 14 is a plate thickness of each stand and a tension between stands based on a correction signal from the control state correction judging device 13,
This is a rolling mill control device that controls rolling speeds. It should be noted that control functions such as a reduction device for operating each stand, a looper, and a roll drive motor are not shown. Here, the function of each operation control element that constitutes the device of the present invention will be described.

First, in the frequency analysis device 10, the time series data of the plate thickness H _i , the inter-stand tension T _i, and the rolling load P _i , which are the rolling results of the rolled plate 8, represent the strength at each frequency by the fast Fourier transform. Power spectrum P
S _Hi , PS _Ti , PS _Pi (where i is a stand number. In this example, i corresponds to four stands 1a to 1d.
= 1 to 4. ) Respectively.

As shown in FIG. 2, the abnormal rolling condition determination device 11 comprises a threshold value setting device 21, a reference threshold frequency shift device 22, an operator 23, and an abnormal condition frequency extraction device 24. The reference thresholds PS _{Hi S} and PS _TiS determined in advance in good rolling conditions are set in the threshold value setter 21, and the reference thresholds PS _HiS and PS _TiS are set in the reference threshold frequency shifter 22. The thresholds PS _HiS ^* and PS _TiS ^* corresponding to the current rolling speed V _i are changed, and the thresholds PS _HiS ^* and PS _TiS ^* and the stand-to-stand plate thickness, _delivery side plate thickness and stand-to-stand tension of operator 23 are changed. By comparing the power spectra PS _Hi and PS _Ti respectively, the abnormal part extraction power spectrum ΔPS _Hi , ΔP where the abnormal parts of the stand thickness and the stand tension are extracted
Output S _Ti .

Here, the threshold value PS_TiS ^*The basis for determining
Functions of the quasi-threshold frequency shifter 22 Stand
Taking the inter-tension as an example, the good tension shown in Fig. 3 (a)
Power spectrum PS in various rolling conditions_Ti ^*More positive
Strength at each frequency f that can be tolerated under normal rolling conditions
The upper limit of the reference threshold PS_TiSCreate as. this
Reference threshold PS_TiSIs, for example, by measurement value or pressure
It will be necessary to create by type of rolled steel, size of rolled sheet, etc.
It At this time, the peak appears as the roll eccentric component.
It is due to the components that change according to the rolling speed such as
It Therefore, the reference threshold frequency shift device 22 is
Current rolling speed V at time point_iAnd reference threshold PS _TiSDecide
It is based on the difference in rolling speed during good rolling
Threshold PS_{Ti S}Peaks a, b, c of the frequency f in the axial direction
Shift to the current pressure as shown in Fig. 3 (b).
Threshold PS in the extended state_TiS ^*Output as.

Similarly, regarding the function of the abnormal state frequency extraction device 24, when the tension between stands is similarly taken as an example, the input signal is the threshold value of the measured power spectrum PS _Ti as shown in FIG. 4 (a). The shaded portion exceeding PS _TiS ^* is determined to be an abnormal portion, and the intensity of only that portion is extracted and output as an abnormal portion extraction power spectrum ΔPS _Ti as shown in FIG. 4 (b).

The processing of the abnormality occurrence factor estimation device 12 will be described. As shown in FIG. 5, the abnormality occurrence factor estimation device 12 includes an abnormality occurrence factor estimation rule group storage device 31, an abnormality occurrence factor estimation preprocessing unit 32, and an abnormality occurrence device. The anomaly occurrence factor estimation rule group storage device 31 stores the anomaly occurrence factor estimation rule group determined by an empirical rule. Then, in the abnormality occurrence factor estimation preprocessing unit 32, the stand inter-plate thickness output from the abnormal rolling state determination device 11,
Calculate the degree of coincidence between the extracted power spectrums ΔPS _Hi and ΔPS _{Ti of the} outlet side plate thickness and tension between the stands and the power spectra PS _H0 and PS _Pi of the inlet side plate thickness and rolling load, and use the results to estimate the cause of abnormality The error occurrence factor estimation result is output to the abnormality occurrence factor estimation rule group storage device 31, which is input to 33, in comparison with the abnormality occurrence factor estimation rule.

Here, the processing function of the abnormality occurrence factor estimation pre-processing unit 32 will be described with reference to FIG. 6. In the case of the exit side plate thickness of the stand 1a, which is the No. 1 stand, as shown in FIG. ) Indicates the abnormal rolling condition determination result by the abnormal rolling condition determination device 11 shown in FIG.
PS _H1 and No. 1 stand (stand 1 shown in Fig. 6 (b)
power spectrum of thickness at entrance side of a) ΔPS _H0 (other anomalies of the power spectrum or the rolling load of the abnormal portion extracts the product of each frequency f also possible) and in the power spectrum
, And the result is shown by the shaded area in FIG. 6 (c). In addition,
The roll eccentricity components at the current rolling speed are f ₀ , f ₁ ,
f ₂ and the frequency bands related thereto are Δf ₀ , Δf ₁ , Δ
Let f ₂ . At this time, in FIG. 6 (c), it can be seen that a roll eccentricity component (A portion in the figure) at f ₀ and a variation component (B portion in the figure) due to variation of the inlet side plate thickness occur. The intensity is quantitatively expressed below.

Now, assuming that the function of the power spectrum ΔPS _H1 extracted from the abnormal portion of the outgoing side plate thickness is P ₁ (f) and the function of the power spectrum ΔPS _H0 of the incoming side plate thickness is P ₂ (f), the coincidence of both signals Is represented by an integral value S ₀ in the entire frequency range obtained by the following equation (1).

[0020]

[Equation 1]

In addition, special features such as low frequency range and roll eccentric part
S showing the agreement in the constant frequency range _f0Or S_fiNitsu
Are expressed by the following equations (2) and (3).

[0022]

[Equation 2]

Such calculation is performed between all or some power spectra. Upon receiving the preprocessing result in the abnormality occurrence factor estimation preprocessing unit 32, the abnormality occurrence factor estimation unit 33 uses the abnormality occurrence factor estimation rule group stored in the abnormality occurrence factor estimation rule group storage device 31, For example, the following anomaly occurrence factors are estimated by fuzzy inference. (1) Large high frequency component of No. 1 stand output side thickness and input side thickness ⇒ Large influence of high frequency of input side thickness disturbance (2) Backup roll of No. 1 stand output side thickness and No. 5 stand output side thickness Rotational speed component ⇒ No. 1 stand Backup roll Large effect of eccentric disturbance (3) No. 2 -No. 3 tension between stands and No. 3 -No. 4 high frequency component of tension between stands ⇒ No. 3 stand The function of the slip disturbance large control state correction determination device 13 will be described with reference to FIG. 7. The control state correction determination rule group determined from the empirical rule for the abnormality generation factor estimation result obtained by the abnormality generation factor estimation device 12. In the control state correction determination unit 42 using the control state correction determination rule group storage device 41 that stores the control state correction determination rule group storage device 41, for example, the control function requiring the correction of the control state and the correction rule are determined as the target. Control parameter to control function And output a control signal correction amount command. (1) Large high frequency component of entrance side plate thickness disturbance ⇒ No. 1 stand B
ISRA-AGC gain increased by 2% (2) No. 1 stand backup roll Eccentric disturbance greatly affected ⇒ No. 1 Stand roll eccentricity gain increased by 2% (3) No. 3 stand slip disturbance large ⇒ Rolling speed command 5 %
DOWN By configuring the control system in this way, the frequency analysis device 10 performs fast Fourier transform on the time series data of the outgoing side plate thickness of the rolling mill 1, the inter-stand plate thickness variation, and the inter-stand tension variation to determine the abnormal rolling state. The device 11 determines the abnormal state of each measured value by the difference between each power spectrum and each threshold value determined from the current rolling speed, and the anomaly occurrence factor estimation device 12 anomaly judgment results and the entrance side plate thickness change and rolling. The factor and the degree of the abnormal state occurrence are estimated using the rule of thumb from the degree of coincidence with each power spectrum of the load change and the rolling speed, and the control state correction determination device 13 determines the excess or deficiency of the control state based on the abnormal state factor estimation result. Judgment of the target control function from the empirical rule, and the rolling mill controller 14 corrects the control parameter or control signal command value of the target control function. It is possible.

By adding the change degree of the abnormality occurrence factor estimation result to the abnormality occurrence factor estimation rule group stored in the abnormality occurrence factor estimation rule group storage device 31 in the abnormality occurrence factor estimation device 12 described above, Determines whether the correction result of the control function is good or bad, and uses the result as a control state correction judging device.
The control state correction determination rule group of 13 may be added to the control state correction determination rule group of the storage device 41 to change the correction amount command of the control function. By changing the control state by each control function using the correction amount command of the control function,
By changing the abnormal state of the rolling mill and repeating the process every moment, the rolling mill can finally be brought into a good state.

Further, in the above embodiment, the description has been made on the assumption that the plate thickness gauges are installed between all the stands, but when the plate thickness gauges are not installed between all the stands or between some stands, It is possible to determine whether or not there is an equivalent abnormal rolling state by predicting the plate thickness on the stand-out side using a model and using the power spectrum of the predicted plate thickness.

That is, as shown in FIG. 8, the stand is a 1 _i stand, the preceding stage stand is a 1 _i-1 stand, and the stand inter-plate thickness gauge 4 _i-1 is on the exit side of the 1 _i-1 stand.
Will be described in detail with respect to the case where the stand is installed and there is no stand thickness gauge on the exit side of the 1 _i stand. First, in the predicted plate thickness calculation device 51, the outgoing side plate thickness measurement value H _i-1 of the 1 _i-1 stand from the inter-stand plate thickness gauge 4 _i-1 is set as the incoming side plate thickness measurement value H _i at the 1 _i stand. type, as entry side thickness H _i ^* of the portion of the plate thickness measurement of the rolled plate 8 were data transfer is delayed and time to arrive directly under the entry side of the 1 _i stand value immediately below the 1 _i stand Ask.

Next, each roll speed detector 7_i-1, 7_i
From each stand roll peripheral speed VR_i-1， VR_iWhen you enter
From the advanced rate calculator 52, the advanced rate of each stand
f_i-1, F _iEnter. And the one needed_iSu
Predicted plate thickness h on the outlet side_iUsing the law of constant mass flow
Then, it is calculated by the following equation (4). h_i= (VS_i-1/ VS_i) ・ H_i ^* = {VR_i-1(1 + f_i-1) / VR_i(1 + f_i)} ・ H_i ^* …… (4) Where VS_i-1; Outboard speed of front stand, VS_iThis
It is the exit plate speed of the stand.

When there is no plate thickness gauge on the entrance side of the stand, calculation is performed by using the estimated plate thickness of the preceding stand which is similarly obtained. Also, usually, No. 1
Since a plate thickness gauge that measures the plate thickness on the entrance side of the stand is generally installed, it is possible to predict the plate thickness on the exit side of all stands by this method.

[0029]

As explained above, according to the method and apparatus of the present invention, the abnormal condition of the rolling mill is judged, the factor causing the abnormal condition is estimated, and the abnormal condition is avoided on the basis of the result. Since the control state can be automatically corrected depending on the condition, it is possible to automatically avoid operational instability phenomena such as product quality fluctuations such as product thickness variation and shape defects due to abnormal rolling, and slip. It is possible.

[Brief description of drawings]

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

FIG. 2 is a block diagram illustrating a configuration of an abnormal rolling state determination device used in the present invention.

3 (a) and 3 (b) are explanatory views of the function of a reference threshold frequency shifter that constitutes an abnormal rolling condition determination device.

4 (a) and 4 (b) are explanatory views of the function of an abnormal state frequency extraction device that constitutes an abnormal rolling state determination device.

FIG. 5 is a block diagram illustrating a configuration of an abnormality occurrence factor estimation apparatus used in the present invention.

6A to 6C are explanatory diagrams of processing functions of an abnormality occurrence factor estimation pre-processing unit which constitutes an abnormality occurrence factor estimation device.

FIG. 7 is a block diagram illustrating a configuration of a control state correction device used in the present invention.

FIG. 8 is a block diagram showing an outline of a means for calculating a predicted plate thickness.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rolling machine 1a-1d Stand 2 Work roll 3 Backup roll 4a Entry side thickness gauge 4b-4d Stand thickness gauge 4e Exit side thickness gauge 5a-5c Tensiometer 6a-6d Rolling load meter 7a-7d Roll speed detector 8 Rolling plate 10 Frequency analysis device 11 Abnormal rolling condition determination device 12 Abnormality factor estimation device 13 Control condition correction determination device 14 Rolling mill control device 21 Threshold setting device 22 Reference threshold frequency shift device 23 Operator 24 Abnormal condition frequency Extraction device 31 Abnormality factor estimation rule group storage device 32 Abnormality factor estimation preprocessing unit 33 Abnormality factor estimation unit 41 Control state correction determination rule group storage device 42 Control state correction determination unit 51 Predicted plate thickness calculation device 52 Advanced ratio calculation apparatus

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B21C 51/00 8315-4E B21B 37/12 111B (72) Inventor Hiroshi Saito Omika Town, Hitachi City, Ibaraki Prefecture 5-2-1 Hitachi Ltd. Omika Plant (72) Inventor Satoshi Hattori 5-2-1 Omikacho, Hitachi City, Ibaraki Prefecture Hitachi Ltd. Omika Plant

Claims (4)

[Claims] 1. A plate thickness on an entrance side and an exit side of each stand of a tandem rolling mill having a plurality of stands and a tension between the stands,
A method for avoiding abnormal rolling conditions in a tandem rolling mill equipped with a control system that measures the rolling load and roll speed of each stand, and that controls the plate thickness between stands and between the stands, the tension between stands, and the rolling speed, respectively In addition, the presence or absence of an abnormal state of each measured value is determined by the difference between each power spectrum of the strip thickness variation between the rolling mill and the stand and between the stands and the tension variation between the stands and each threshold value determined from the current rolling speed. In addition, if it is determined to be abnormal, the frequency band that is abnormal and the degree of the abnormality are determined, and the degree of coincidence between the determination results of the abnormal state and the power spectra of the inlet side plate thickness change and rolling load change and rolling Estimate the factor and the degree of abnormal state occurrence from the speed using empirical rules,
A tandem rolling mill characterized by determining the control function that is the target of excess or deficiency of the control state based on the result of estimating the factors that cause this abnormal state, and correcting the control parameter or control command value of the target control function. Abnormal rolling condition avoidance method. 2. The abnormal rolling in the tandem rolling mill according to claim 1, wherein the degree of change of the rolling state due to the correction of the control parameter or the control command value of the target control function is added to the factor estimation of the abnormal state occurrence. State avoidance method. 3. The method for avoiding an abnormal rolling state in a tandem rolling mill according to claim 1 or 2, wherein a predicted plate thickness obtained by calculation is used for the plate thickness between all stands or a part between stands. 4. A plate thickness gauge for measuring the plate thickness between the entrance and exit sides of a tandem rolling mill equipped with a plurality of stands and a stand, a tensiometer for measuring tension between each stand, and a rolling load meter for measuring each stand rolling load. And a roll speed detector that detects the rolling speed of each stand, and a plate thickness control device that controls the plate thickness between the stands and on the delivery side of the rolling mill, a tension control device that controls the tension between the stands, and the rolling speed. An abnormal rolling state avoidance device in a tandem rolling mill equipped with a speed control device, which is a fast Fourier transform by inputting time series data from the above-mentioned entrance / exit plate thickness gauge, stand thickness gauge, tensiometer, and rolling load meter. A frequency analysis device for converting into a power spectrum by conversion, and the presence or absence of an abnormal state of the rolling mill is determined from the power spectrum of the plate thickness and tension obtained by the frequency analysis device. A normally rolled state determining device, an abnormal rolling state determination in the abnormal rolling state determining device,
An abnormality occurrence factor estimation device that estimates an abnormality occurrence factor of the rolling mill from the power spectrum of the entrance side plate thickness and the rolling load from the frequency analysis device and the rolling speed detected by the roll speed detector, and the abnormality occurrence factor A control state correction determining device that determines a control function and a correction amount that require the control state to be corrected based on an abnormality occurrence factor estimation result in the estimation device, and a plate of each stand based on a correction signal from the control state correction determining device. A rolling mill control device for controlling the thickness, tension between stands, and rolling speed, respectively, and an abnormal rolling state avoidance device for a tandem rolling mill.