JPS6225444B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plate thickness control device that detects the absolute value of a plate thickness without time delay and controls the absolute value of the plate thickness to match a target value in a rolling mill having one or more rolling stands.

In steel plate rolling mills, the thickness of the rolled plate at the outlet generally fluctuates considerably, so automatic thickness control (abbreviated as AGC) is used to control the plate thickness to a constant value.
will be carried out.

This is broadly divided into (a) those using a thickness gauge and (b) those using a gauge meter, but each has its own problems.

(b) AGC using a thickness gauge The thickness gauge is installed at a location away from the rolling stand in order to protect the thickness gauge from damage in the event of breakage of the plate material, or for maintenance management of the thickness gauge. . Therefore, the plate thickness change that occurs directly below the rolling rolls is detected after the dead time t _L has elapsed, and this dead time is expressed by the following equation.

t _L = L ₀ /V where L ₀ is the distance from just below the roll to the installation position of the thickness gauge, and V is the average value of the steel plate moving speed on the exit side.

Generally, it is difficult to implement stable control with a control circuit that has dead time, so sample value control is performed in which control is performed by observing the response to the roll reduction as it appears on the thickness gauge. Furthermore, since the amount of dead time varies greatly depending on the moving speed of the steel plate, that is, the rolling speed, the sampling interval is set to be inversely proportional to the rolling speed. However, it is difficult to correct sudden changes in plate thickness.

(b) AGC using a gauge meter Assuming the rolling mill as an elastic body with a constant spring constant, calculate the outlet side plate thickness from the roll gap (set value) and rolling reaction force (parameter) at no load using Hook's law. However, this control method adjusts the roll gap so that this value matches the target value, and unlike the case using a thickness gauge, there is no dead time.

If the rolling force detected by the load cell is P, the roll gap under no load is R, and the spring constant is M, considering that the rolls and formwork are distorted according to Hook's law, then the load The roll gap, that is, the exit plate thickness _h2 at the time is expressed as follows.

h ₂ =R+P/M (1)' However, it is impossible to directly measure the roll gap R under no load, and it is measured as the moving distance of the rolling cylinder from a certain base point.

Therefore, the measured value of R includes (i) roll wear;
(ii) Roll thermal expansion, (iii) Changes in back-up roll bearing oil film due to rolling speed, (iv) Roll eccentricity, etc. are not included, so the true roll gap under no load is the same as these (i) to (iv). This means that the error of the component is included. In other words, it is necessary to always correct the components (i) to (iv).

The method using a gauge meter can instantaneously detect changes in plate thickness due to changes in rolling force, so it is a highly responsive control method, but the mill stiffness coefficient M
has a property that changes depending on the magnitude of the rolling force P, the width of the plate material, etc., so there is a limit to the control accuracy of the plate thickness.

As described above, the gage meter method has the drawback that it cannot essentially detect the true plate thickness, so even if a target value for the outlet plate thickness is given, the deviation between this value and the calculated plate thickness value is set to zero. Even if this is done, it is meaningless as the absolute value of the exit plate thickness cannot be measured. Therefore, in view of these problems, a control method was devised to improve the control accuracy of plate thickness and bring the absolute value of plate thickness into agreement with the target value. This is the lock-on value correction control method that will be explained next.

(c) Lock-on value correction control method This method does not directly use the detected value of outlet plate thickness by the thickness gauge for control, but uses it indirectly to improve the absolute accuracy of the gauge meter. Yes, the plate thickness detection value h _G by the gauge meter and the plate thickness detection value h _R by the thickness gauge are always compared.

As mentioned above, the error components of the plate thickness detected by the gauge meter include roll wear and thermal expansion, but since these error components change gradually by their nature, it is important to calculate the thickness detected by the gauge meter. If the gauge meter is calibrated, when a new plate is inserted, the gauge meter can immediately indicate the absolute value of the plate thickness, and correction operations can be performed according to the deviation from the target value.

In other words, if the calibrated detection error of the gauge meter is ΔR=h _G −h _r ………(2)′, then the deviation of the true plate thickness from the target value is Δh=h _G +ΔR ………(3 )′, and the true deviation Δh can be found from the detected value h _G of the gauge meter.

Furthermore, when there is a deviation Δh in plate thickness, the deviation ΔR in the set value of the roll gap at no load is
(Here, ΔR=R-R _L , where R _L is the lock-on value of the roll gap at no load) is determined accurately.

In other words, use the following formula.

ΔR=(1+Q/M)Δh……(4)′ However, Q is the plasticity coefficient of the plate material, and M is the mill rigidity coefficient which is the spring constant of the rolling mill.

By the way, in the known technique, the plasticity coefficient Q of the plate material is determined from the value of the inlet plate thickness, the value of the plate thickness detected by a gauge meter, and the value of the rolling force. Moreover, the mill stiffness coefficient M is constant and its value is assumed to be given.

Δh is the plate thickness value detected by the gauge meter,
The deviation from the target thickness value, Δ based on equation (4)′
R is calculated and a new no-load roll gap setting value R' is given as R'=R+ΔR.

FIG. 1 is a block diagram showing the configuration of a known device, in which an appropriate plate thickness correction gain is determined from the variations in rolling force, rolling position, outlet side plate thickness, and inlet side plate thickness at each sampling point mentioned above, that is, at the control timing. This enables highly accurate plate thickness control.

First, to explain the block configuration, 1a is the i-th
+1 stand plate thickness calculation device, 1b is an i-th stand plate thickness calculation device, which calculates the outlet side plate thickness of the i+1 and i-th rolling mills based on equation (1)', respectively. 2a and 2b have this plate thickness,
In order to cause a delay in transportation to the next rolling mill, which is determined from the circumferential speed of the rolling mill rolls and the distance between the two,
This is a delay storage device. 3a is the i+th rolling mill in which the outlet side plate thickness of the i-th rolling mill is delayed by the transportation delay.
A gain calculation device that calculates a plate thickness correction gain from the plate thickness at the entrance side of a rolling mill and the output of a plate thickness calculation device 1a. Similarly, 3b calculates the outlet side plate thickness of the i-1st rolling mill, the inlet side plate thickness of the i-th rolling mill delayed by the transportation delay from the i-1st to the i-th rolling mill, and the i-th rolling machine plate thickness calculation. From the output with device 1b, the i-th
This is a gain calculation device that calculates the plate thickness correction gain of a rolling mill.

4a is a reduction correction value calculation device that determines a reduction correction value from the deviation from the target plate thickness of the i+1st rolling mill and the obtained plate thickness correction gain, and 4b is also the i+th rolling mill.
A rolling correction value calculation device that determines a rolling correction value for one rolling mill, and these are the i+1th
It is connected to the stand lowering control device 5a and the i-th stand lowering control device 5b.

With this no-load roll gap setting method,
The online measurement of the plasticity modulus Q of the plate material is used in the gain calculation to calculate ΔR.

Therefore, it is inevitable that the accuracy of this online measurement value Q will have a direct influence.

Q depends on the properties of the material and varies significantly with plate temperature.

Moreover, although it is based on the assumption that the plasticity coefficient for changes in outlet plate thickness and that for changes in inlet plate thickness are the same, in an actual machine the two take different values, making it difficult to improve the measurement accuracy of Q.

Furthermore, the mill stiffness coefficient M is not a constant value, but actually varies.

Further, the difference between the gauge meter display and the thickness meter output is not a constant value, but changes each time the magnitude of the rolling force changes, and also changes depending on the shape of the plate material. And calibrating a gauge meter with a thickness gauge is not simple.

For this reason, the conventional lock-on value correction control system has the drawback that the accuracy of the absolute value of the plate thickness is not sufficient.

In addition, in some known technologies, in order to cope with the diversification of the characteristics of the plate material to be controlled, a summary table of past data under various sheet threading conditions is stored, and the current processing is performed based on this data. The plasticity modulus and thickness modification gain of the plate material are determined by extracting the one that is suitable for the rolling conditions and making some modifications, but it is actually very difficult to determine the exact thickness modification gain. That's true.

This invention improves the above situation by estimating the value of the outlet plate thickness without time delay using a mathematical model of the outlet plate thickness in a rolling mill having one or more rolling stands, thereby achieving high accuracy and stability. The present invention provides an automatic plate thickness control device that is highly flexible and responsive.

The automatic plate thickness control device of the present invention is an automatic plate thickness control device for a rolling mill equipped with one or more rolling stands having a pair of reduction rolls. , a reduction cylinder connected to one of the reduction rolls, a position detector energized by the reduction cylinder to detect the reduction cylinder position of the reduction cylinder, and a position detector attached to the reduction cylinder to detect the reduction force of the reduction cylinder. a plate length detector connected to the reduction roll to determine the length of the plate material after rolling; and a pass schedule for controlling the exit plate thickness, the rolling force, the position of the reduction cylinder, and the length of the plate material. the exit plate thickness, rolling force, rolling cylinder position, and plate material length input from the pass schedule calculating device, and the rolling force cylinder position, rolling force, and plate material during rolling input from each of the detectors. a deviation rate measuring device that calculates an estimated value of the mill stiffness coefficient from the deviation from the measured value of the length; a deviation rate of the mill stiffness coefficient input from the deviation rate measuring device; and a deviation rate of the mill stiffness coefficient input from the path schedule calculation device. Estimating the deviation of the outlet plate thickness from the reference value based on the deviation between the reference values of the rolling force and the position of the rolling cylinder and the measured values of the rolling force and the position of the rolling cylinder input during rolling input from the rolling force detector and the position detector. an exit plate thickness estimating device that calculates the value; a control device that calculates the magnitude of the reduction amount from the estimated value input from the estimation device and controls the drive device of the reduction cylinder based on the magnitude of the reduction amount; It is equipped with the following.

Hereinafter, this invention will be explained in detail based on an embodiment of the apparatus shown in FIG.

In FIG. 2, 7 is a pair of reduction rolls for rolling the plate material 19, and 10 is an exit plate thickness detector. The rolling roll 7 is an equivalent spring (representing the deformation of the roll) 1
8, and one of the roll-down rolls 7 is further connected to the roll-down cylinder 6 via this equivalent spring 18. The reduction cylinder 6 is provided with a reduction cylinder position detector 8 and a reduction force detector 9. 11 is a plate length detector connected to the reduction roll 7, 12 is a pass schedule calculation device, 13 is a deviation rate measuring device for mill stiffness coefficient, 14 is an exit plate thickness estimation device, 15 is a control device, and 16 is a hydraulic pipe line. 17
The hydraulic flow control valves are connected as shown. The control valve 17 is connected to a drive device (not shown), which applies a predetermined reduction force to the reduction cylinder 6.

Now, when the plate material 19 is bitten by the reduction roll 7, the value of the moved cylinder position S is obtained by the cylinder position detector 8. Further, the magnitude P of the rolling force is detected by the rolling force detector 9. The number of rotations of the reduction roll 7 is taken into the plate length detector 11, and the length L of the plate after rolling is determined from the number of roll rotations N _P from the time of biting the plate and the advance rate f of the plate during rolling. Desired.

In other words, it can be obtained from the formula below.

L=a(1+f)N _P a: Coefficient On the other hand, in the pass schedule calculation device 12, the reference value P of the rolling force P, cylinder position S, and outlet plate thickness _h2
i , S _i and h _2i are calculated from the so-called pass schedule of the rolling plan. A reference value M _i of the mill stiffness coefficient M, which is the spring constant of the equivalent spring 18, is also calculated.

The combination of the rolling forces obtained in this way is P, P
_i , the combination of cylinder positions is S, S _i , the combination of outlet plate thickness is h ₂ , h _2i , and the combination of mill stiffness coefficients is M, M _i , then the following relational expression holds between these: .

h ₂ =S+P/M……(1) h _2i =S _i +P _i /M _i ……(2) Furthermore, Δh ₂ =h ₂ −h _2i , ΔS=S−S _i , ΔP=
If P−P _i and ΔM=M−M _i , then equation (3) can be approximately derived from the above equation, and this becomes the basic relational expression in this invention.

Δh ₂ =ΔS+ΔP/M _i +(−ΔM/M _i )P/M _i
………(3) Also, from the combination of data measured at the current and past time t (h ₂ (t), S(t), P(t)), h ₂ is delayed by the movement time of the plate. Taking into account that observed, (h ₂ (t), S(t'), P
(t′)) is a combination of measurement data at the same point on the board.

As a result of the above, the combination of data at the same point of the current and past plates (h ₂ (t), S (t'), P
(t')), the combination of data (Δh ₂ , ΔS, ΔP) is obtained, and the deviation rate of the mill stiffness coefficient (-ΔM/M _i ) _{est is} calculated from the relationship of equation (4) below. be done. This is the calculation content of the device 13.

(−ΔM/M _i ) _est = M _i /P _i (Δh ₂ −ΔS−ΔP
/M _i )......(4) Next, using the estimated value of -ΔM/M _i (-ΔM/M _i ) _est obtained from equation (4), Δ is calculated based on equation (3).
The current estimated value Δh _2est of the outlet plate thickness Δh ₂ is determined from the current values of S and ΔP. That is, P〓P _i
The calculation contents of the following equation (5) are the calculation contents of the exit plate thickness estimating device 14.

Δh _2est = ΔS+ΔP/M _i +(−ΔM/M _i ) _est P
_i /M _i ......(5) Next, in order to make the deviation Δh ₂ of the outlet plate thickness from the reference value zero, the control device 15 sets K to the control gain, and K
The flow control valve 16 of the hydraulic system is operated according to the magnitude of Δh ₂ . The position of the reduction cylinder 6 is the hydraulic line 1
It is determined by the oil flow rate flowing through 7.

According to the configuration of the embodiment described above, it is possible to further improve the accuracy of Δh _2est by correcting the oil film at the reduction cylinder position S and incorporating drift due to roll wear, etc.

Next, the effects of this invention will be explained in detail in comparison with the conventional technology.

With the conventional AGC method, the plate thickness at the top of the plate can be adjusted by lock-on operation after the plate has been bitten.
It is detected by the BISRA method (gauge meter method), and if it is equal to a predetermined value _h20 , the cylinder position _S0 and the reduction force _P0 at that time are taken as the respective reference values. Then, for the subsequent measured values h ₂ , S, and P, control is performed to make Δh ₂ expressed by equations (6), (7), and (8) zero.

h ₂₀ = S ₀ + P ₀ /M ₀ ………(6) Δh ₂ = ΔS+kΔP/M ₀ ………(7) Δh ₂ =h ₂ −h ₂₀ , ΔS=S−S ₀ , ΔP=P−P ₀
………(8) Here, M ₀ is the setting value of the mill stiffness coefficient,
It cannot be said that it necessarily represents the equivalent spring constant of the rolling mill at that time, and zero point correction of the cylinder position must also be performed.

Therefore, the absolute value of the detected plate thickness always includes an error of several hundred microns, and this value varies from pass to pass or from slug to slug. In this way, in the conventional lock-on BISRA method, the reference value detected by lock-on is
Control is performed to reduce Δh ₂ , which is the sum of the deviations from S ₀ and P ₀ , and it is very effective in suppressing the fluctuations from h ₂₀ , but the absolute value of h ₂₀ , which is the base, is It is said that it is unavoidable that there will be a large measurement error. Therefore, by taking measures such as making the lock-on points the same, the variation in _h20 between passes can be suppressed and reduced, but the variation in plate thickness between plates can be reduced. It was difficult to suppress the differences in standard value _h20 between boards.

On the other hand, in the present invention, first, the reference plate thickness value and the value of the rolling force applied thereto are precisely determined by pass schedule calculation, taking into account the properties of the plate material, and the reference values are set as h _2i and P _i , respectively.

The accuracy of recent pass schedule calculations is high, so it is possible to calculate a value close to the rolling force in actual rolling machines for a given plate material.

Next, an oil film correction value is calculated based on data such as the rotational speed of the roll, and zero point correction of the cylinder position is performed.

Once the reference value M _i of the mill rigidity coefficient of the rolling device is set, the reference value S _i of the cylinder position is calculated according to equation (2).

S _i = h _2i - P _i /M _i If the target value of the absolute value of the plate thickness is h _2i , then the corresponding rolling force P _i and cylinder position S
The value of _i is precisely calculated. Furthermore, even if M _i is different from the actual machine value M of the rolling down device, the deviation rate ΔM/M _i
As mentioned above, the correction is made for. Since it is expected that the rolling force will converge to a value that takes into account the shape of the plate, etc., this has the effect of improving the quality of the plate after rolling.

Furthermore, in this invention, based on the relational expression (3) regarding the deviation from the reference value, when the exit plate thickness deviation Δh ₂ is known, the deviation rate of the mill stiffness coefficient is calculated from the measured data of Δh ₂ , ΔS, and ΔP. −ΔM/M _i is calculated. On the other hand, when the exit plate thickness deviation Δh ₂ is an unknown amount, Δh ₂ is calculated using the measured data of ΔS and ΔP and the value of the deviation rate of the mill stiffness coefficient −ΔM/M _i . In this manner, the present invention uses the basic relational expression to calibrate the mill stiffness coefficient, and calculates a precise numerical value for the outlet plate thickness according to the magnitude of the deviation rate of the coefficient. The above-mentioned basic relational expression (3) is exclusively related to the rolling characteristics of the rolling mill, and it is considered that the sheet material characteristics are related to the dimensions of the sheet, that is, the sheet width, and the value of the mill rigidity coefficient. This measurement therefore requires less time to calibrate the mill stiffness coefficient, since it uses only data that can be measured on the rolling mill.

Therefore, compared to the conventional method, the control device of the present invention statistically accumulates rolling data and compiles rolling mill setting values for each type and size of plate material into a statistical table.
It is possible to perform control that is simple and can quickly respond to fluctuations.

Furthermore, by measuring the deviation rate of the mill rigidity coefficient as described above, it is possible to calculate the numerical value of the mill rigidity coefficient of the actual rolling mill and the zero point correction value of the rolling cylinder position.

In other words, if the fluctuation of P in equation (3) is large, Δh ₂ ,
By applying the least squares method using ΔS, ΔP/M _i and P as measured values, a term ΔS ₀ is detected in addition to the coefficient (−ΔM/M _i )1/M _i of P.

In this way, each value of the mill rigidity of the rolling characteristic and the zero point of the cylinder position can be statistically determined from the measured values of the actual machine. Next, the value of the outlet plate thickness is estimated from the constant value obtained in this way. From this value, a plate thickness control system is constructed that makes the deviation of the outlet plate thickness from the target value zero.

As detailed above, the automatic plate thickness control device of the present invention uses a mathematical model of the outlet plate thickness to estimate the value of the outlet plate thickness without time delay, thereby achieving high accuracy and
This allows for plate thickness control that satisfies stability and quick response. Conventional control systems have been applied to multi-stand tandem rolling mills, and have never been applied to single-stand plate rolling mills, but the control system of the present invention can be applied to multi-stand as well as single-stand rolling mills. It is possible.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram of a conventional rolling mill plate thickness automatic control device, and FIG. 2 is a configuration diagram of a rolling mill plate thickness automatic control device showing an embodiment of the present invention. 1a...I+1st stand plate thickness calculation device, 1b
...I-th stand plate thickness calculation device, 2a, 2b...
Delay device, 3a, 3b...gain calculation device, 4a,
4b... Rolling correction value calculation device, 5a... i+1st
Stand lowering control device, 5b...I-th stand lowering control device, 6... Rolling cylinder, 7... Rolling down roll, 8... Rolling down cylinder position detector, 9... Rolling force detector, 10... Outlet plate thickness Detector, 11...
Plate length detector, 12... Pass schedule calculation device, 13... Deviation rate measuring device for mill stiffness coefficient, 1
4...Exit plate thickness estimation device, 15...Control device, 1
6...Hydraulic flow control valve, 18...Equivalent spring, 19
...Plate material.

Claims (1)

[Claims] 1. In an automatic plate thickness control device for a rolling mill equipped with one or more rolling stands having a pair of reduction rolls, an exit plate thickness detector for measuring the exit plate thickness of the rolling stand, and an outlet thickness detector connected to one of the reduction rolls. a lowering cylinder, a position detector attached to the lowering cylinder and detecting the position of the lowering cylinder, a lowering force detector attached to the lowering cylinder and detecting the lowering force of the lowering cylinder, and the lowering roll. a plate length detector that is connected to and calculates the length of the plate material after rolling; a pass schedule calculation device that calculates a pass schedule for control amounts of the exit plate thickness, rolling force, rolling cylinder position, and plate length; The mill is calculated based on the deviation between the exit plate thickness, rolling force, rolling cylinder position, and plate material length input from the calculation device and the measured values of the rolling force cylinder position, rolling force, and plate material length during rolling input from each of the above-mentioned detectors. A deviation rate measuring device for calculating an estimated value of the stiffness coefficient, a deviation rate of the mill stiffness coefficient inputted from the deviation rate measuring device, and a reference value of the rolling force and the rolling cylinder position inputted from the path schedule calculation device. an exit plate thickness estimating device that calculates an estimated deviation of the exit plate thickness from a reference value based on a deviation from a measured value of the rolling force and the position of the rolling cylinder inputted from the rolling force detector and the position detector; A rolling mill characterized by comprising a control device that calculates the magnitude of the rolling reduction amount from the estimated value input from the estimation device and controls the driving device of the rolling cylinder based on the magnitude of the rolling reduction amount. Automatic plate thickness control device.