JPH0739914A - Method for controlling plate thickness of hot rolling mill - Google Patents

Abstract

PURPOSE:To provide a plate thickness control method of a hot rolling mill which can approach to an objective plate thickness and restrain its variation. CONSTITUTION:When the plate thickness is set to an objective thickness by controlling rolling reduction so that a plate thickness measured by a thickness meter provided on the outlet side of a hot rolling mill is fed back to remove the deviation from the objective plate thickness, a roll gap is corrected by feed back control in accordance with an average thickness of the tip part of a stock to be rolled through an initial rolling-down corrective control system 9. Then, PI compensation is made according to a measured thickness fed back by a corrective rolling-down corrective control system 10 at every sampling time of the thickness meter to correct the roll gap. Consequently, the plate thickness on the outlet side can be approached quickly to the objective thickness and its variation be restrained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strip thickness control method for a hot rolling mill.

[0002]

2. Description of the Related Art In ordinary hot strip rolling, automatic strip thickness control (hereinafter, referred to as "plate thickness distribution" in order to reduce the strip thickness distribution in the longitudinal direction of the material to be rolled and bring the strip thickness on the delivery side of the rolling mill to a target thickness. A
(Referred to as GC) has been introduced. As this AGC, a lock-on type gauge meter AGC is generally used (see, for example, Japanese Patent Laid-Open No. 2-11205).

In this gauge meter AGC, the mill constant of the rolling mill, the predictive accuracy of the deformation resistance of the rolled material (so-called gauge meter accuracy) is not sufficient, so that an error occurs between the average thickness of the outlet side plate and the target thickness. However, there is a problem that the variation of the deformation resistance in the longitudinal direction due to the skid marks causes the variation of the delivery side plate thickness to remain. Therefore, in order to correct the error between the rolling mill exit side plate thickness and the target thickness caused by the gauge meter error, the measured thickness h measured by the thickness gauge and the target thickness h
_The monitor AGC is performed to feed back the difference Δh from the _aim to the hydraulic pressure reduction device and correct the roll gap (correction reduction) to bring the target thickness closer to the target thickness.

In the conventional monitor AGC, the measured thickness h is fed back at every sampling time of the thickness gauge to obtain the target thickness h.
PI (proportional-integral) control is performed so that the difference from the _aim is zero.

[0005]

However, the monitor AGC by the PI control described above has the following problems. That is, since the output side plate thickness and the reduction correction amount are out of phase due to the dead time caused by the distance between the rolling mill and the thickness gauge, if the control gain is increased to quickly approach the target thickness, the solid line in FIG. As shown in (3), the original plate thickness variation is increased, and the variation of the delivery side plate thickness near the target thickness becomes large. On the other hand, if the control gain is lowered, the variation of the delivery side plate thickness near the target thickness is suppressed as shown by the dotted line in the figure, but the target thickness becomes slower to approach. In the figure, T ₁ is the control start time of the monitor AGC. As described above, it is difficult for the conventional monitor AGC by PI control to satisfy both the target thickness and the plate thickness variation.

The present invention has been made to solve the above-mentioned problems of the prior art, and is capable of quickly approaching the target thickness and suppressing fluctuations in the outlet plate thickness near the target thickness. An object of the present invention is to provide a strip thickness control method for a hot rolling mill.

[0007]

SUMMARY OF THE INVENTION The present invention is a heat control system that controls the amount of reduction so that the deviation from the target thickness becomes zero by feeding back the thickness measured by a thickness gauge installed on the delivery side of the rolling mill. In the method of controlling the plate thickness of a hot rolling mill, a PI process is performed based on the process of correcting the roll gap by feedback control based on the average thickness of the plate tip of the material to be rolled, and the measured thickness fed back at each sampling time of the thickness gauge. And a step of compensating and correcting the roll gap by feedback control.

[0008]

[Operation] According to the present invention, an initial reduction correction control system that performs feedback control based on the average thickness of the plate front end, and PI compensation based on the measured thickness that is fed back at each sampling time of the thickness gauge are fed back. Since the correction reduction correction control system to be controlled is provided in parallel, it is possible to quickly bring the delivery side plate thickness closer to the target thickness and suppress the fluctuation thereof.

[0009]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing an embodiment of the present invention. In the figure, 1 is a hot rolling mill, which is a pair of upper and lower work rolls 3a and 3b facing each other with a material 2 to be rolled therebetween,
A pair of upper and lower backup rolls 4a rolling on these,
4b, and the amount of reduction of the lower backup roll 4b is controlled by the hydraulic cylinder 5.

Reference numeral 6 is a plate thickness gauge, such as a gamma ray thickness gauge, which is attached to the outlet side of the hot rolling mill 1 and measures the plate thickness of the material 2 to be rolled. The controller is a controller for inputting the plate thickness detection value h of the rolled material 2, and the calculation result is output to the hydraulic pressure reduction control device 8 which controls the hydraulic cylinder 5. As shown in the block diagram of FIG. 2, the controller 7 feedbacks the initial roll-down correction control system 9 that feedback-controls the roll gap based on the initial plate thickness of the plate tip portion, and feedbacks at every sampling time of the plate thickness gauge 6. It is constituted by two feedback control systems in parallel with a correction reduction correction control system 10 which feedback-controls the roll gap based on the measured thickness. The roll gap correction amount (ΔS ₁ + ΔS ₂ ) output from the two parallel control systems 9 and 10 by the controller 7 is sent to the hydraulic pressure reduction controller 8 to move the hydraulic cylinder 5 to control the roll gap.

In the controller 7 thus constructed, the initial reduction correction control system 9 first calculates the average thickness of the plate thickness h of the plate tip portion at the sampling point measured by the plate thickness meter 6 at each sampling time t. It is input to the circuit 11 and the average thickness h ^* of the several points is calculated. After that, the deviation Δh ₁ from the target thickness h _aim is calculated (FIG. 3 (a)), and this deviation Δh ₁ is promptly output as the roll gap correction amount ΔS ₁ (FIG. 3 (b)) for feedback control. The roll gap is corrected by. After the output, the roll gap correction amount ΔS _{1 which} is the initial reduction correction amount is held until the rolled material 2 bites through the work roll 3, whereby the delivery side plate thickness h quickly approaches the target thickness.

Since the average thickness h ^* of the tip of the plate is different from the average thickness h ^{** of the} entire plate length, the output ΔS ₁ from the initial reduction correction control system 9 alone causes an error between the output side plate thickness and the target thickness. Will occur. Therefore, the correction reduction correction control system 10 is a function necessary to correct the error between the average thickness h ^* of the plate front end portion and the average thickness h ^{** of the} entire plate length, whereby the target thickness is adjusted by the correction reduction correction amount ΔS _2. Accuracy is improved.

That is, in the correction reduction correction control system 10, the deviation Δh ₂ between the measured thickness h fed back by the plate thickness gauge 6 and the target thickness h _aim is calculated for each sampling time t (FIG. 4 (a)). PI compensation is performed in the PI calculation circuit 12, and a roll gap correction amount ΔS ₂ (FIG. 4 (b)) as the correction reduction correction amount is output after the initial reduction correction amount ΔS ₁ is output (FIG. 4 (c)).

As a result, since the exit side plate thickness approaches the target thickness by the initial reduction correction amount ΔS ₁ , the control gain of the PI control in the correction reduction correction control system 10 is more than the control gain of the monitor AGC by the conventional PI control. It is possible to reduce the thickness, and it is possible to suppress the variation of the outlet plate thickness near the target thickness. FIG. 5 shows the transition of the outgoing side plate thickness when the monitor AGC by PI control of the present invention is applied. Roll gap correction amount ΔS ₁ at time T ₁
Is output to start the initial reduction correction, and the roll gap correction amount ΔS ₂ is output at time T ₂ to start the reduction correction by PI control, and the target thickness accuracy is improved.

[0015]

As described above, according to the present invention,
An initial reduction correction control system that performs feedback control based on the average thickness of the plate front end and a correction reduction correction control system that performs PI compensation and feedback control based on the measured thickness fed back at each sampling time of the thickness gauge are provided in parallel. As a result, the delivery side plate thickness can be quickly brought close to the target thickness, and its fluctuation can be suppressed, whereby the plate thickness accuracy of the product can be improved.

[Brief description of drawings]

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

FIG. 2 is a block diagram of a controller used in the present invention.

FIG. 3 is an explanatory diagram of an operation of an initial reduction correction control system.

FIG. 4 is an explanatory diagram of an operation of a correction reduction correction control system.

FIG. 5 is a characteristic diagram showing changes in the outlet plate thickness controlled by the method of the present invention.

FIG. 6 is a characteristic diagram showing changes in the outlet plate thickness controlled by a conventional method.

[Explanation of symbols]

 1 Hot Rolling Mill 2 Work Roll 3 Work Roll 4 Backup Roll 5 Hydraulic Cylinder 6 Plate Thickness Gauge 7 Controller 8 Hydraulic Reduction Controller 9 Initial Reduction Correction Control System 10 Corrected Reduction Correction Control System 11 Average Thickness Calculation Circuit 12 PI Calculation Circuit

Claims (1)

[Claims] 1. A plate thickness control method for a hot rolling mill, which feeds back the plate thickness measured by a thickness gauge installed on the delivery side of the rolling mill to control the reduction amount so that the deviation from the target plate thickness becomes zero. In the above, in the step of correcting the roll gap by feedback control based on the average thickness of the plate front end portion of the rolled material, and by performing PI compensation based on the measured thickness fed back at each sampling time of the thickness gauge, and performing roll control by feedback control. A plate thickness control method for a hot rolling mill, characterized by combining a step of correcting a gap.