JPH10202308A - Sheet thickness control method and sheet thickness control device in continuous rolling mill - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To ensure the degree of freedom in setting the responsiveness to a target plate thickness while sufficiently securing the responsiveness to disturbance and the stability of a rolling operation, and to improve the responsiveness. SOLUTION: Using a comparison value: tb that becomes a target thickness: ta with a predetermined time delay, a deviation amount of a thickness detection value: tc: e.
To obtain a roll gap adjustment amount: x necessary to cancel the deviation amount: e, and a target value: td that becomes a target plate thickness: ta with a predetermined time delay from the roll gap adjustment amount: x. Is added to obtain a control signal for controlling the roll gap: Ya, while the control signal: Ya
Is multiplied by a predetermined time delay, the roll rotation speed of the upstream rolling stand is adjusted based on a tension compensation signal: Yb, which is obtained, so as to suppress the fluctuation in tension due to the roll gap adjustment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for controlling a thickness of a continuous rolling mill, and more particularly, to a technique for quickly and stably setting a rolled material thickness to a target thickness at the initial stage of rolling or when changing a target thickness. The present invention relates to a thickness control method and a thickness control device that can be controlled.

[0002]

2. Description of the Related Art Conventionally, in a rolling process using a continuous rolling mill, the thickness of a rolled material is one of the most important control items in terms of product quality, and thickness control is performed so that a target thickness can be obtained. . The thickness control is performed, for example, by adjusting the roll gap of the rolling stand.However, depending on the method of providing the target thickness, the rolling mill load increases due to a change in rolling conditions, or the rolling load limit is exceeded, The load efficiency of the electric motor for driving the rolling mill may be exceeded, thereby hindering the production efficiency or stopping the rolling, which may cause a decrease in productivity.

[0003] Japanese Patent Application Laid-Open No. 8-71626 discloses that the thickness of the delivery side of each rolling stand in a continuous rolling mill is calculated using a known mass flow equation, and the thickness of the delivery side of each rolling stand is calculated as follows. By performing feedback control to achieve the target value, the load is appropriately distributed to each rolling stand, and a large change operation of the roll gap in one rolling stand is avoided, so that the sheet surface quality and operability can be improved. A thickness control method for stabilization is disclosed.

[0004] However, even in such a conventional thickness control method, it is still not possible to sufficiently prevent the limitation of the rolling mill load caused by the operation of changing the roll gap in controlling the exit side thickness of the rolling stand. was there.

Further, in the conventional sheet thickness control method, it is extremely difficult to independently adjust the response to the disturbance and the response to the target sheet thickness. It was difficult to improve the responsiveness to the target sheet thickness at the beginning of rolling or at the time of changing the target sheet thickness while securing the same.

In addition, in a continuous rolling mill having a plurality of rolling stands, the control target is generally a multivariable and interference system, and the tension between stands also changes by adjusting the roll gap for controlling the sheet thickness. As a result, the dimensions and surface quality of the rolled material may be adversely affected, and the stabilization of the operation may be hindered.

[0007]

The inventions described in claims 1 to 5 are all made on the background of the above-mentioned circumstances, and the object of the invention is to solve the problems at the beginning of rolling and the target sheet thickness. To provide a thickness control method or a thickness control device in a continuous rolling mill capable of advantageously setting and securing the responsiveness to a target thickness at the time of change while securing a good responsiveness to disturbance. It is in.

In any of the first to fifth aspects of the present invention, the adverse effect on the rolling operation due to the change in the tension between stands caused by the adjustment of the roll gap for controlling the thickness of the sheet is advantageously reduced. It is also an object of the present invention to provide a method or apparatus for controlling the thickness of a continuous rolling mill, which can prevent the occurrence of cracks.

[0009]

In order to solve such a problem, the invention according to claim 1 is configured such that the delivery-side sheet thickness of a rolled material in a continuous rolling mill becomes a set or changed target sheet thickness. In performing the thickness control by adjusting the roll gap, a comparison value that becomes a target thickness with a predetermined time delay is used, a deviation amount between the comparison value and the thickness detection value is obtained, and the deviation amount is canceled. And a control signal is obtained by adding a target value which becomes a target plate thickness with a predetermined time delay to the roll gap adjustment amount, and the roll signal is adjusted based on the control signal. By adjusting the roll rotation speed of the upstream rolling stand based on the tension compensation signal obtained by multiplying the control signal by a predetermined time delay while adjusting the gap, The gauge control method the tension variation caused by the regulation of cap in suppressing continuous rolling mill, characterized.

According to the method of the first aspect of the present invention, the adjustment of the roll gap for obtaining the target thickness is performed by:
This is performed by feedback control based on two-degree-of-freedom control. Adjusting and setting the response to the target plate thickness by adjusting the transfer characteristics when obtaining the comparison value and the target value based on the target plate thickness. In addition, by adjusting the transfer characteristic when obtaining the roll gap adjustment amount based on the deviation amount, the response to the disturbance can be adjusted and set, so that the response to the target sheet thickness and the disturbance can be adjusted. Responsiveness can be set independently of each other.

Therefore, the responsiveness to the target sheet thickness can be adjusted while ensuring the responsiveness to the disturbance, and the roll gap can be adjusted so as to reach the target sheet thickness with an arbitrary responsiveness. Responsiveness to a target plate thickness can be realized.

Further, according to the method of the present invention, the roll rotation speed is adjusted in accordance with the adjustment amount of the roll gap for obtaining the target sheet thickness, so that the rolling speed can be reduced at the beginning of rolling or when the target sheet thickness is changed. Since the change in tension due to the change in the roll gap is suppressed, it is possible to arbitrarily set the response to the target sheet thickness while ensuring stable rolling properties without considering the adverse effect on the change in tension. You can.

The invention described in claim 2 is the first invention.
In the thickness control method in the continuous rolling mill according to the invention described in the above, using the output thickness of the final stand, based on the mass flow thickness formula, determine the output thickness of each stand, the output thickness of each stand is It is characterized in that the thickness control is performed by adjusting the roll gap of each stand so that the target thickness is obtained.

[0014] According to the method of the present invention, only the thickness gauge installed on the exit side of the final stand is used as the thickness gauge for actually measuring the thickness of the rolled material. Since the thickness can be obtained, the number of expensive thickness gauges to be installed can be reduced.

[0015] The invention described in claim 3 is based on claim 1.
Or in the method for controlling a thickness of a continuous rolling mill according to the invention described in 2, wherein the target thickness is changed when a rolling load or a current of a motor for driving a roll in each stand exceeds a predetermined limit value. Is the feature.

According to the third aspect of the present invention, when the target plate thickness is changed in order to avoid exceeding the load limit of the rolling mill due to an excessive rolling operation of the roll gap, etc. Appropriate responsiveness can be set for the set target plate thickness, and stable productivity can be advantageously secured.

According to a fourth aspect of the present invention, there is provided a sheet thickness control apparatus for a continuous rolling mill which has been made to solve the above-mentioned problems. And (b) first calculating means for obtaining a comparison value with a predetermined time delay from the target thickness given by the target thickness setting means, c) comparing means for comparing the comparison value obtained by the first calculation means with the detected thickness of the rolled material to obtain a deviation amount; and (d) canceling the deviation amount obtained by the comparison means. (E) third calculating means for obtaining a target value with a predetermined time lag to the target sheet thickness given by the target sheet thickness setting means, (F) the second computing means Adding means for obtaining a roll gap control signal by adding the target value obtained by the third calculating means to the roll gap adjustment amount obtained by the calculation, and (g) the roll obtained by the adding means. By multiplying the gap control signal by a predetermined time delay, the roll rotation speed in the upstream rolling stand is adjusted to change the tension of the rolled material caused by the roll gap change based on the roll gap control signal. Fourth calculating means for obtaining a tension compensation signal for suppressing
Thickness control device in a continuous rolling mill.

In the sheet thickness control device having the structure according to the fourth aspect of the present invention, the time delay amount in the first calculating means and the time delay amount in the third calculating means are used to set the target sheet thickness. And the response to the disturbance can be adjusted by setting the gain in the second calculation means, so that the response to the target plate thickness and the response to the disturbance Can be set independently of each other, and by adjusting the roll rotation speed based on the tension compensation signal obtained by the fourth calculating means, it is possible to prevent a change in the roll gap from adversely affecting the tension fluctuation. Is done.

Therefore, in such a thickness control apparatus, it is possible to advantageously obtain the responsiveness to the target thickness while securing the responsiveness to disturbance and the stable rolling property.

The invention described in claim 5 is the same as the invention in claim 4.
A thickness control device for a continuous rolling mill having a structure according to the invention described in (1), further comprising a thickness measuring means for determining a detected thickness of the rolled material based on a mass flow thickness formula.

In the continuous rolling mill having the structure according to the fifth aspect, it is not necessary to install the thickness gauge on each stand, and the thickness is measured only by the thickness gauge on the exit side of the final stand. Based on the mass flow plate thickness formula, the plate thickness on the exit side of each stand can be obtained.

Therefore, it is possible to reduce the number of expensive thickness gauges, to advantageously reduce the cost of the apparatus, simplify the structure, and improve the maintenance.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail based on specific structural examples of the present invention.

First, FIG. 1 shows a schematic model of a continuous rolling mill to which a thickness control device constructed according to the present invention is applied, and FIG. 2 shows a schematic configuration of the thickness control device. This is shown by the block diagram. The continuous rolling mill shown in FIG. 1 is a continuous rolling mill provided with a plurality of rolling stands, and only a final stand 10a and an upstream stand 10b immediately before the final stand 10a are shown in the drawing. Each of the stands 10a, 10b is provided with a work roll 12, 1 respectively.
And a rolling roll composed of a backup roll 14 and a backup roll 14. The roll is driven by a driving motor 16, so that an appropriate reduction amount determined by a reduction device 18 is passed between the work rolls 12 and 12. The rolling operation is performed on the rolled material 20 to be rolled. A looper roll 2 is provided between both stands 10a and 10b.
The looper roll 22 swings and is pressed against the rolled material 20 so that the rolled material 20 is
, An appropriate tension is applied. In addition, a load cell 24 is installed in each of the stands 10a and 10b so that the rolling load is measured. Further, a thickness gauge 26 is provided on the exit side of the final stand 10a so that the exit side thickness of the rolled material 20 is actually measured, and a deflector roll 28 is provided.
Is provided, and the rolled material 20 is supported. As the looper roll 22, the load meter 24, the thickness gauge 26, and the deflector roll 28, various known types can be used.

The roll gaps in the final stand 10a and the upstream stand 10b are adjusted by the thickness control devices 30a and 30b having the structure according to the present invention, so that the exit side thickness of the final stand 10a is controlled for rolling. The thickness control is performed so that the final target plate thickness given by the process computer 35 is given, and the roll rotation speed of the upstream stand 10b set by the roll rotation speed control device 33 is adjusted, so that the final stand 10a The change in the tension due to the change in the roll gap is suppressed.

The thickness control device 30
Both a and 30b are configured as shown in FIG. That is, each plate thickness control device 30 has a target plate thickness calculator 32 that gives a target plate thickness at the exit side of each stand 10, and in this target plate thickness calculator 32, a process computer 35 (FIG. With reference to the value of the final target plate thickness: t ₀ given in (1), each value of the rolling load: P in each stand 10 and the supply current to the rolling mill drive motor 16: I do not exceed the limit values. In consideration of the thickness change amount t ′ determined by the target thickness change amount calculator 34, each stand 10
At the delivery side target thickness ta. For example, based on the value of the final target plate thickness: t ₀ ,
If the rolling load: P is likely to exceed the limit value for some reason during rolling while giving the target thickness to each stand 10, the target thickness change amount calculator 34 calculates Rolling load: Thickness change amount required to avoid exceeding P limit value:
t ′ is calculated, and based on the result, the target thickness calculator 3
In 2, the exit target plate thickness of each stand 10 is changed and set. As is apparent from this, in the present embodiment, the target thickness calculator 32 and the target thickness change amount calculator 34 cooperate with each other to set the target thickness setting means for giving the target thickness of the rolled material. It is configured.

When the change value ta of the outlet target plate thickness in each stand 10 is determined in this way, the first arithmetic unit 36 reaches the outlet target plate thickness ta with a predetermined time delay. Comparative value: tb is determined. Here, the time delay amount from the comparison value: tb to the delivery-side target plate thickness: ta is arbitrarily determined in consideration of the responsiveness required for the change of the target plate thickness. As shown in the following (Equation 1) and FIG. 3, the first computing unit 36 is set with a first-order lag transfer characteristic: F _i (s).

F _i (s) = 1 / (T _FFi s + 1) (Equation 1) where i is a suffix representing a stand NO., S is a Laplace operator, and T _FF is a target thickness change. (Response adjustment coefficient).

Next, the comparison value: tb obtained by the first computing unit 36 is supplied to the
It is compared with the delivery side actual thickness value tc of the rolled material measured at 0, and as a difference between them, a deviation amount e from the comparison value tb of the delivery side actual thickness value tc is obtained.

Here, it is possible to install a thickness gauge on the output side of each stand 10 for the actual value of the output side sheet thickness: tc at each stand 10, but preferably, it is theoretically based on a mass flow method. In particular, in the hot rolling mill, since the thickness gauge is installed on the exit side of the final stand, the actual thickness of the exit side in each stand 10 is calculated using the measured value of the thickness gauge. The value: tc is advantageously calculated. More specifically, since the mass flow equation is expressed as the following (Equation 2), the roll rotation signal: R1 of the final stand 10a and the deflector roll 28 in the thickness calculator 40 as the thickness measuring means. Roll rotation signal: R2, each stand roll rotation signal: R3, rotation signal of each stand looper roll 22: R4, and the exit side thickness measurement signal tr by the thickness gauge 26 are input,
Using these input values, the exit plate thickness detection value of each stand is determined in order from the final stand 10a toward the upstream side based on the mass flow equation.

[0031] _{H i V i = h i v} i ∴ h i = (V i / v i) × H i ··· ( Equation 2) where, h _i is, NO. Thickness at delivery side of the i stand, V _i Is
NO. I (case interstand tension is constant, NO. I equals delivery side speed on the upstream side stand stand) entrance side speed stand, v _i is NO. I stand delivery side speed, H _i is It is the thickness of the entrance side of the NO.i stand (equal to the thickness of the exit side of the upstream stand of the NO.i stand when the tension between stands is constant).

Then, the deviation amount obtained by the comparator 38:
e is input to the second computing unit 42, and the second computing unit 4
In step 2, the deviation amount: e is canceled and each stand 10
Roll gap adjustment amount of each stand 10 required to set the output side plate thickness actual value: tc to the target plate thickness: tb: X
Is required. Here, as the second computing unit 42, a controller having various conventionally known control characteristics can be adopted as a control unit constituting the feedback control system. In addition to the control unit performing PI control, for example, As shown in the following (Equation 3) and FIG. 4, the one configured with the transfer characteristic: C _i (s) including the phase compensator set by using the robust control theory, etc. ,
It is preferably adopted.

C _i (s) = 1 / s × (n _3is ³ + n _2is ² + n _1is ¹ + n _0i ) / (s ³ + d _2is ² + d _1is ¹ + d _0i ) (formula) 3) where, i is the subscript of the stand NO., s is Laplace operator, n ₀ ~n ₃ and d ₀ to d ₂ are control gains, 1 / s is an integrator, (n _3i s ³ + N _2is ² + n _1is
¹ + n _0i ) / (s ³ + d _2is ² + d _1is ¹ + d _0i )
It is a phase compensator.

Further, a target value: td which reaches the delivery side target plate thickness: ta with a predetermined time delay is obtained by the third computing unit 44, and this target value :: td is obtained by the second computing unit 42. The roll gap control signal: Ya is obtained by adding the obtained roll gap adjustment amount: Xa by the adder 46. That is, in this specific configuration example, the first to third computing units 36, 42, and 44 are used to process the feedback signal (actual value): tc based on the target plate thickness: ta to control the roll gap. A two-degree-of-freedom control system for obtaining the signal: Ya is configured.

In the third computing unit 44, the amount of time delay between the target value: td and the output side target thickness: ta is set in consideration of the responsiveness required for a change in the target thickness. Generally, it is determined based on the time delay amount set in the first computing unit 36. More specifically, for example, as shown in the following (Equation 4) and FIG. 5, the transfer characteristic of the third calculator 44 is Q _i (s). : F _i (s)
And the transfer characteristic of the controlled object: P _i (s).

[0036] _{Q i (s) = P i} -1 (s) F i (s) = (T i s + 1) / (T FFi s + 1) ··· ( Equation 4) where, i represents the stand NO. The subscript, s is the Laplace operator, T _FF is the response specification value (response adjustment coefficient) of the target thickness change, and P _i ^-1 is the inverse model of the control object.
Here, the approximation was made using a simple first-order lag.

Then, as shown in FIG. 1, the operation of the rolling-down device 18 of each rolling stand 10 is controlled based on the control signal Ya thus obtained, so that each rolling stand 10 The delivery side plate thickness is adjusted so as to reach the target plate thickness: ta with a predetermined time delay, that is, responsiveness.

On the other hand, the obtained roll gap control signal: Ya is input to a fourth computing unit 48, and the fourth computing unit 48 multiplies the roll gap control signal by a predetermined time delay. : Roll rotation speed adjustment signal: Yb in the rolling stand one upstream of the rolling stand 10 whose roll gap is adjusted based on Ya is determined. The amount of delay time in the fourth computing unit 48 is determined in consideration of the operation of adjusting the roll gap in the rolling mill, the operation of adjusting the roll rotation speed of the upstream stand, and the transmission characteristics of the change in the tension of the rolled material. For example, as shown in the following (Equation 5) and FIG. 6, the transfer characteristic: K _i (s) in the fourth computing unit 48 is obtained from the roll rotation speed adjustment operation of the upstream stand. The transmission characteristic of the rolled material to the change in tension: Gv and the transmission characteristic from the roll gap adjustment operation to the change in the tension of the rolled material: Gs are determined.

K _i (s) = km _i × Gs _i (s) / Gv _i−1 (s) (Equation 5) where i is a suffix representing a stand NO., And km is an adjustment coefficient. Show.

That is, based on the roll rotation speed adjustment signal Yb obtained by the fourth calculator 48, the rolling stand 10 upstream of the rolling stand 10 in which the roll gap is adjusted (see FIG. 1). , Final stand 1
By adjusting the roll rotation speed in the upstream stand 10b (when the roll gap adjustment operation is performed at 0a), the fluctuation of the tension between stands caused by the roll gap adjustment can be suppressed.

Therefore, when the above-described thickness control device is used, when the rolling load of the rolling mill or the current of the electric motor for driving the rolling mill exceeds a predetermined limit value, there is a request from the operator to change the thickness target. In order to reduce the rolling mill load in cases such as when the thickness target value is changed automatically or manually, or when the thickness target value is newly set at the beginning of rolling, the rolls in each stand The gap can be advantageously adjusted so as to obtain the target plate thickness, and by adjusting the transfer characteristics in the first computing unit 36 and the third computing unit 44, the desired value response and the desired value response can be adjusted. Independently of the responsiveness to disturbance set by adjusting the transfer characteristic in the second computing unit 42,
It can be set arbitrarily.

Therefore, the output side plate thickness of each stand is advantageously controlled so that the changed or set target plate thickness can be obtained with the specified good response while ensuring sufficient response to disturbance. It becomes possible.

Hereinafter, examples of the present invention will be described. However, the present invention is not to be construed as being limited to the specific description based on the examples and the specific configuration examples described above. , Various changes and modifications based on the knowledge of those skilled in the art,
It can be implemented in an aspect with improvements and the like,
It goes without saying that all such embodiments are included in the scope of the present invention unless they depart from the gist of the present invention.

[0044]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a four-stand tandem rolling mill using a thickness control device having a structure according to the above specific configuration example,
A simulation in the case where the thickness control at the beginning of rolling was performed was performed under the conditions shown in the following (Table 1). In addition,
The thickness control was started when the rolled material bit into the final stand. The initial disturbance was such that the thickness error on the entrance side of the first stand (most upstream side stand) was 1 mm, and the target thickness on the exit side of the first stand was 50 μm when the rolling load was limited during rolling.
m. Further, a time constant in the first computing unit: T
_FF was specified to be 10 seconds. The result is shown in FIG.
Shown in

[0045]

As is clear from the results shown in FIG.
In addition to the advantage that the inter-stand tension fluctuation after the start of the thickness control and the change of the target thickness is advantageously suppressed, the target thickness at the first stand exit side after the target thickness change is the target thickness value after the change. , It is recognized that the rolling force at the first stand is advantageously reduced with the specified response.

On the other hand, as a comparative example of the present invention, FIG. 8 shows a simulation result in the case of performing PI feedback control with one degree of freedom in a rolling operation using the same rolling mill as in the above embodiment. In this comparative example, compared to the result of the embodiment shown in FIG. 7, the tension variation between the stands after the start of the thickness control is large, and the response to the target thickness cannot be specified even after the target thickness is changed. For this reason, it is clear from FIG. 8 that it takes time to reach the target plate thickness.

[0048]

As is apparent from the above description, in any of the first to third aspects of the present invention, the responsiveness to the target plate thickness and the responsiveness to the disturbance can be set independently of each other. In addition to this, the adverse effect on the tension fluctuation due to the change of the roll gap is prevented, and therefore,
It is possible to arbitrarily and advantageously obtain the responsiveness to the target plate thickness while sufficiently securing the responsiveness to disturbance and the stability of the rolling operation.

[0049] This also makes it possible to advantageously secure the degree of freedom of load distribution of each stand in the rolling mill while securing the thickness accuracy and the surface quality under excellent rolling stability. Yes, it is possible to improve production efficiency advantageously.

Further, in the sheet thickness control device according to the fourth or fifth aspect of the present invention, any one of the first and third operation units can advantageously execute the method of the present invention. By adjusting the transfer characteristics at, the target value responsiveness and the responsiveness to disturbance can be set independently and arbitrarily, so that the responsiveness to disturbance can be sufficiently secured while achieving the target plate thickness. Responsiveness can be advantageously secured, and quick and stable control of the thickness can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic model diagram of a continuous rolling mill to which a sheet thickness control device configured according to the present invention is applied.

FIG. 2 is a block diagram showing a schematic configuration of a sheet thickness control device in FIG.

FIG. 3 is a block diagram showing a first calculator in the plate thickness control device shown in FIG. 2;

FIG. 4 is a block diagram showing a second calculator in the plate thickness control device shown in FIG. 2;

FIG. 5 is a block diagram showing a third computing unit in the plate thickness control device shown in FIG. 2;

FIG. 6 is a block diagram showing a fourth computing unit in the plate thickness control device shown in FIG. 2;

FIG. 7 is a graph showing a simulation result as an example.

FIG. 8 is a graph showing a simulation result as a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Rolling stand 18 Rolling-down apparatus 20 Rolled material 26 Thickness gauge 30 Thickness control device 32 Target thickness calculator 34 Target thickness change amount calculator 36 First calculator 38 Comparator 40 Plate thickness calculator 42 Second Operation unit 44 Third operation unit 46 Adder 48 Fourth operation unit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B21B 37/26 B21B 37/12 BBP (72) Inventor Akira Takahashi 5-11-3 Shimbashi, Minato-ku, Tokyo Sumitomo Light Metal Industries (72) Inventor Michio Nonaka 5-11-3 Shimbashi, Minato-ku, Tokyo Sumitomo Light Metal Industries Co., Ltd.

Claims (5)

[Claims] When a roll gap is adjusted and a thickness control is performed such that a delivery side thickness of a rolled material in a continuous rolling mill becomes a set or changed target thickness, the target thickness is adjusted with a predetermined time delay. Using the comparative value that is thick,
The amount of deviation between the comparison value and the thickness detection value is obtained to obtain a roll gap adjustment amount necessary to cancel the deviation amount, and the target thickness is determined with a predetermined time delay from the roll gap adjustment amount. A control signal is obtained by adding a target value, and the roll gap is adjusted based on the control signal, while a tension compensation signal obtained by multiplying the control signal by a predetermined time delay is obtained. A thickness control method for a continuous rolling mill, wherein a roll rotation speed of an upstream-side rolling stand is adjusted to suppress a tension variation caused by adjusting the roll gap. 2. Using the actual output thickness of the final stand, the output thickness of each stand is determined based on the mass flow thickness formula, and the output thickness of each stand is set to the target thickness. The method according to claim 1, wherein the thickness control is performed by adjusting the roll gap of each stand. 3. The thickness control method according to claim 1, wherein the target thickness is changed when a rolling load or a current of a roll driving motor in each stand exceeds a predetermined limit value. 4. A first sheet thickness setting means for providing a target sheet thickness of a rolled material in a continuous rolling mill, and a first value for obtaining a comparison value with a predetermined time delay to the target sheet thickness given by the target sheet thickness setting means. Calculating means; comparing means for comparing the comparison value obtained by the first calculating means with the detected thickness of the rolled material to obtain a deviation amount; and for canceling the deviation amount obtained by the comparison means. A second calculating means for obtaining a required roll gap adjustment amount, a third calculating means for obtaining a target value with a predetermined time delay to the target thickness given by the target thickness setting means, Adding means for obtaining a roll gap control signal by adding the target value obtained by the third calculating means to the roll gap adjustment amount obtained by the calculating means; By multiplying the obtained roll gap control signal by a predetermined time delay, the roll rotation speed in the upstream rolling stand is adjusted, and the rolling generated by the roll gap change based on the roll gap control signal is controlled. And a fourth calculating means for obtaining a tension compensation signal for suppressing a change in the tension of the material. 5. The apparatus according to claim 4, further comprising a sheet thickness measuring means for obtaining the sheet thickness detection value of the rolled material based on a mass flow sheet thickness formula.
3. The plate thickness control device according to 1.