JPS6272418A - Automatic control device for plate thickness - Google Patents

Abstract

PURPOSE:To improve a control accuracy of plate thickness by equipping plate thickness gauges on inlet and outlet sides of a rolling mill respectively, comparing plate thickness deviations of corresponding inlet and outlet sides and based on this comparison, controlling the outlet plate thickness predicitively. CONSTITUTION:The plate thickness meters 12, 16 are equipped on the inlet and outlet sides of the rolling mill 10 and a frequency analyzing filter 22 for deviation of plate thickness and a rolling reduction controlling controller 24 are installed. The inlet plate thickness of a rolling material 20 is compared with a set value by he plate thickness meter 12 to output a plate thickness deviation DELTAH0 on the inlet side to the filter 22 and the controller 24. The deviation DELTAh0 of the outlet plate thickness is outputted by the outlet plate thickness meter 16 to the filter 22. Each plate thickness deviation DELTAH, DELTAh is compared by the filter 22 to input signals DELTAH, DELTAh of the thickness deviations to an arithmetic part 26 comparing a damping coefficient of the plate thickness deviation with the set value to correct. In this control method, the accuracy of plate thickness control is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a plate thickness control device for a rolling mill, and in particular, measures the inlet side plate thickness and predictably controls the outlet side plate thickness. This invention relates to a so-called feed-forward type automatic plate thickness control device.

[Background of the invention]

There are two methods for controlling the thickness of rolled material in a rolling mill: one is to indirectly measure the thickness directly under the rolls of the rolling mill from the gap between the rolls, etc., and control the thickness deviation; There is a method of directly measuring the thickness of the material using a thickness gauge and controlling the thickness deviation. In the former case, it is possible to improve plate thickness controllability by improving the accuracy of rolling load, rolling speed, etc., and in the latter case, it is possible to improve the thickness controllability by improving the accuracy of rolling load and rolling speed. By improving the accuracy of compensating for deviations, it is possible to improve plate thickness controllability.

Ready-made white! 11] Further improvement in accuracy of W thickness control technology or a new sheet thickness control method is required. In the conventional plate thickness control method in which the plate thickness is indirectly determined, the plate thickness control accuracy is almost determined by the accuracy of the detector, and the accuracy of the detector is insufficient. Thickness control methods that directly measure plate thickness include a method in which the signal of the detected exit plate thickness is fed back to control the rolling position (including the gap between the rolls), and a method in which the detected signal of the input plate thickness is fed back to control the rolling position (including the gap between rolls). There is a method of tracking in the rolling direction, determining the plate thickness immediately below the rolling position, and controlling the inter-roll gap in advance so that the exit side plate thickness deviation becomes zero. The method of measuring the outlet side plate thickness is structurally based on feedback control with a delay time, so it has the drawback that it cannot maintain a high control gain and cannot follow disturbances with a fast change period. Moreover, in order to compensate for this delay time, complicated control including estimation of the rolling state using a rolling model is required. On the other hand, plate thickness control using the entry side plate thickness signal is well known as feed-forward automatic plate thickness control (F-FAGC), and it is possible to control by compensating for the delay time of each control device, so feedback Compared to control, it can follow fast change cycles and has high controllability.

However, in feed-forward automatic plate thickness control (hereinafter sometimes referred to as predictive control), the exit side plate thickness must be predicted in advance in principle, and control accuracy is determined by the accuracy of this estimated value.

In this conventional predictive control, the exit side plate thickness estimated from rolling theory is preset before the start of rolling (for example, Japanese Patent Application Laid-Open No. 57-22811), and the input data itself is Since the accuracy of the rolling process and the accuracy of the rolling 8 del itself are insufficient, it is not possible to make predictions with sufficient accuracy, and furthermore, it is impossible to follow changes in conditions during rolling.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an automatic plate thickness control device using a feedforward method that can control plate thickness with high accuracy.

[Summary of the invention]

In controlling plate thickness in a rolling mill, it is first necessary to quantitatively analyze the type and magnitude of disturbances that affect the exit side plate thickness. As shown in Fig. 2, rolling is a state in which the tμ deformation of the rolled material whose entry side thickness is H and the elastic deformation of the rolling mill are balanced under load P, and the exit side thickness is generated. means. The factor that disrupts this equilibrium state is disturbance, and the second
From the figure, there are three (3) rolling load fluctuations ΔP due to factors other than ΔH2ΔS. The entrance plate thickness deviation ΔH is the effect of the disturbance generated in the pre-rolling process on the rolled material,
ΔS and ΔP are disturbances generated during rolling that affect the rolled material.

The magnitude of the disturbance is quantified by the amount of disturbance and the period of occurrence, and the disturbances ΔH9ΔS and ΔP each independently generate the exit side plate thickness deviation.

However, with the improvement of rolling mill accuracy in recent years, the rolling position fluctuation Δ
S and rolling load fluctuation ΔP are becoming smaller, and the influence of the inlet side thickness deviation ΔI (on the exit side plate thickness is particularly large. Therefore, if this Δ■-( can be effectively controlled, the Plate thickness accuracy can be greatly improved.

FIG. 3 is a block diagram of conventional predictive control.

In FIG. 3, reference numeral 1 is an influence coefficient of the entrance side plate thickness deviation on the outlet side plate thickness deviation, numeral 2 is a tracking model, and numeral 3 is a reduction control controller model.

Reference numeral 4 indicates a reduction control device model.

That is, in the conventional predictive control, a material to be rolled having an entry side plate thickness deviation ΔH is rolled into a plate having a thickness h including an exit side plate thickness detection error Δhd. −・ direction, entry side plate thickness deviation ΔH
is incorporated into the tracking model 2 together with the entrance side plate thickness detection error ΔH4. These ΔH and ΔH1 are calculated by the pressure reduction control controller model 3 and the pressure reduction control device model 4.
It is outputted as a plate thickness control amount Δhc via , and the exit side plate thickness deviation is set to Δh.

The ideal responsiveness to the entrance plate thickness deviation ΔH in such predictive control is as shown in FIG. In the block diagram of predictive control shown in FIG. 3, the following are predictively determined: (1) Tracking deviation Tz of the plate; (2) Dead time Ta of the down gauge.

■There are three factors that influence the inlet side plate thickness deviation on the outlet side plate thickness.

If (2) and (2) are collectively defined as the difference Δτ from the proper control advance time, and (2) is defined as the ratio U between the in-computer estimated constant and the true value, then when examining the response due to U, the result is as shown in the figure. As is clear from Figure 1, when the value of the in-computer estimated constant differs from the true value and the value of U becomes smaller, the plate thickness deviation attenuation rate Δh/ΔH
decreases uniformly from low to high frequencies. Therefore, if the in-computer estimated constant differs from the true value, the original controllability of feedforward automatic plate thickness control (when u=1) will be lost.

This is easier to understand if you think about it as follows.

Now, even though we have to perform the reduction control for 10, if we only control 5, 5 will remain on the exit side. Another fact is that conventional predictive control intentionally lowers the control gain in order to prevent excessive control. This is nine lines in response to the recent demand for highly accurate plate pressure control, and it is necessary to make the control as close to ten as possible.

In particular, in rolling, due to the work hardening properties of the rolled material, when rebus rolling is performed, in the younger passes,
In tandem rolling, it is advantageous to reduce the thickness deviation in rolling stands with lower numbers. However, there are limits to improving the estimated control gain of predictive control.
The characteristics of predictive control could not be fully utilized.

On the other hand, according to experiments conducted by the inventors, it was found that there is a correlation between the entrance side plate thickness deviation ΔH and the exit side plate thickness deviation Δh, as shown in FIG. Figure 6 shows the frequency spectrum of the inlet thickness deviation and the frequency spectrum of the outlet thickness deviation.The peak of the outlet thickness deviation indicated by ■ in Figure 6 is the same as the inlet thickness deviation. ΔS caused by rolling.

This is thought to be due to the influence of disturbances such as ΔP. and.

The peak of the spectrum that occurs in common on the inlet and outlet sides indicated by the mark is due to the influence of the inlet side plate thickness deviation ΔH.

In addition, as shown in Figure 5, the uncertainty of the control gain causes a decrease in the thickness deviation attenuation rate especially in the low frequency region, so the part of the entrance side thickness deviation in the low frequency region is of interest. .

The present invention has been made based on the above knowledge, and includes plate thickness gauges arranged at the entrance and exit sides of a rolling mill to determine the entrance-side thickness deviation and the exit-side thickness deviation. The attenuation rate of the thickness deviation is determined by comparing the inlet side thickness deviation and the corresponding outlet side thickness deviation at a given frequency, and the rolling conditions (thickness control gain) are changed to increase this attenuation rate. , which is configured to improve the accuracy of plate thickness control in predictive control.

[Embodiments of the invention]

A preferred embodiment of the automatic plate thickness control device according to the present invention is as follows:
The details will be explained according to the attached drawings.

FIG. 1 is a block diagram showing an embodiment of an automatic plate thickness control device according to the present invention.

In Fig. 1, the entrance side of the rolling mill IO has an entrance side plate thickness gauge of 1
A detection unit 14 of the rolling stock 20 is arranged, and a detection unit 18 of an exit side plate thickness gauge 16 is arranged on the exit side, so that the entrance side plate thickness and the exit side plate thickness of the rolled material 20 can be detected. There is. The entry side plate thickness gauge 12 compares the entry side plate thickness of the rolled material 2o detected by the detection unit 14 with a set value, and sends the entry side plate thickness deviation ΔHo to the plate thickness deviation frequency analysis filter 22 and the rolling reduction control controller 24. Output. Further, the outlet side plate thickness detector 16 compares the outlet side plate thickness of the rolled material 20 detected by the detection unit 18 with a predicted value, and outputs the outlet side plate thickness deviation Δha to the plate thickness deviation frequency analysis filter 22 .

The plate thickness deviation frequency analysis filter 22 cuts the high frequency region of plate thickness deviations ΔHo and Δho on the inlet and outlet sides, discriminates only the same frequency components of both, and detects disturbances caused by rolling (disturbances due to ΔS and ΔP). distinguish between Signals ΔH9Δh of the inlet and outlet thickness deviations discriminated by the thickness deviation frequency analysis filter 22 are input to the thickness deviation attenuation rate calculation unit 26, respectively. The plate thickness deviation attenuation rate calculation unit 26 calculates the plate thickness deviation attenuation rate Δ for several appropriately selected frequencies.
I:/ΔH is determined and inputted to the reduction control controller 24. The roll-down control controller 24 compares the input value of the plate thickness deviation attenuation rate Δh/ΔH with a set value to find an error in the estimated value, and corrects the roll-down control gain (for example, the gap between rolls via the cylinder). This correction can be performed continuously or intermittently at appropriate timing. When correction is performed intermittently, the timing of the correction can be determined by an operator or automatically.

After correcting the roll-down control gain, the roll-down control controller 24 feeds back this correction value to the roll-down control device 28t to control the roll-down control device. Further, the rolling control controller 24 stores the results obtained by this correction as rolling results, and inputs them to the preset model (rolling control parameter determination device 30) as data for improving preset accuracy for the next pass and next coil. The plate thickness deviation frequency analysis filter 22 may be configured using hardware or may be configured using software.

In this way, according to this embodiment, the thickness of the outlet side of the material to be rolled can be controlled with high accuracy. Also.

If the exit plate thickness deviation does not attenuate even after correction is performed in the reduction control controller 24, it can be determined that the plate tracking or dead time compensation of the reduction gauge is inappropriate.
In this way, inappropriate control conditions can be corrected at an early stage.

〔Effect of the invention〕

As described above, according to the present invention, by increasing the attenuation rate of the exit side plate thickness deviation with respect to the inlet side plate thickness deviation, it is possible to improve the accuracy of plate thickness control using the feedforward method.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the automatic plate thickness control device according to the present invention, Fig. 2 is an explanatory diagram showing the principle of rolling, Fig. 3 is a block diagram of a conventional slave side control, and Fig. 4 is a block diagram showing an embodiment of the automatic plate thickness control device according to the present invention. Response characteristic diagram for entry side plate thickness deviation that can be expected in slave side reduction control,
Fig. 5 is a response characteristic diagram when there is an error in estimating the control parameters in predictive reduction control, and Fig. 6 is a diagram showing the frequency function analysis results of plate thickness deviation on the entry side and exit side.91
0...Rolling mill, 12...Entry side plate thickness gauge, 14.18.
...Detection section, 16.. Output side plate thickness meter, 20.. Rolled material, 22.. Thickness deviation frequency analysis filter, 24.. Rolling control controller, 26.. Thickness deviation attenuation rate calculation section. , 28... Reduction control device, 30... Preset model.

Claims (1)

[Scope of Claims] 1. An entry side plate thickness gauge that detects the thickness of the rolled material entering the rolling mill; Entry side deviation calculation that calculates the difference between the detected value of the entry side plate thickness gauge and the entry side plate thickness setting value an outlet side plate thickness gauge that detects the thickness of the rolled material coming out of the rolling mill; an outlet deviation calculator that calculates the difference between a detected value of the outlet plate thickness gauge and a predicted value of the outlet plate thickness. and; A deviation attenuation rate that compares the inlet thickness deviation at a given frequency of the inlet thickness deviation calculated by the inlet deviation calculator with the corresponding outlet thickness deviation to determine the attenuation rate of the plate thickness deviation. An automatic plate thickness control device comprising: a calculator; and a controller that changes a plate thickness control gain based on the output signal of the deviation decay rate calculator. 2. The automatic plate thickness control device according to claim 1, wherein the inlet side plate thickness gauge and the outlet side plate thickness gauge are each equipped with a low-pass filter.