JPS6257706A - Method for measuring roll eccentricity of rolling mill - Google Patents

Abstract

PURPOSE:To eliminate superfluous processing and to measure eccentricity without errors by correcting predicted load by the DC component which does not depend on the rotating angular frequency of a roll, among the results of high- speed Fourier transform. CONSTITUTION:The basic component, second-order higher harmonic wave component - of the fluctuations of rolling load are derived with the rotating angular frequency of the roll as the basic frequency when the high-speed Fourier transform is executed. The DC component which does not depend on the rotating angular frequency of the roll is determined at the same instant and since this component corresponds to the predicted load, said component can be used for correction. More specifically, the Fourier transform 45 is preliminarily calculated with regard to the fluctuation of the predicted load and is substrated from the high-speed Fourier transform 46 of the measurement data. The high-speed Fourier transform 44 which is the true load fluctuation can be thereby determined. The need for making the superfluous processing with a central processing unit is thus eliminated and the errors of the high-speed Fourier transform are eliminated.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention provides a roll eccentricity removing device that uses a fast Fourier transform technique to prevent variations in rolled plate thickness due to eccentricity of rolls of a rolling mill. This paper relates to a method for accurately measuring fluctuations in

[Technical background of the invention and its problems]

BACKGROUND ART In recent years, rolling mills have adopted rolling devices with a fast response speed, such as hydraulic rolling devices.

Furthermore, various AGC (automatic gain control) methods have been devised as control methods, and plate thickness accuracy has improved.

With the development of such rolling technology, fluctuations in rolled sheet thickness due to roll eccentricity have become apparent, and this fluctuation could not be removed by the above-mentioned control alone.

A roll eccentricity removing device has been proposed to eliminate variations in rolled plate thickness due to roll eccentricity.

This roll eccentricity removing device measures the fluctuation of the rolling load, uses some method to remove the roll eccentricity from this measurement result, adjusts the rolling head of the hydraulic rolling device based on this calculation result, and removes the roll eccentricity. This is a means to eliminate fluctuations in the rolling plate pressure caused by the rolling plate pressure.

Recently, fast Fourier transform techniques have been increasingly used as a method for calculating roll eccentricity. There are various methods for calculating the roll eccentric group using fast Fourier transform and controlling methods using the calculation results.

A block diagram showing the circuit configuration representing the basic rolling load measurement method is shown in FIG.

In FIG. 2, a material to be rolled 13 is sandwiched between an upper roll 11 and a lower roll 12 and rolled.

In general, rolling mills are multi-staged, consisting of an upper work roll, a lower work roll that directly contacts the material to be rolled, and an upper back-up roll and lower back-up roll that apply rolling load to these work rolls. These are omitted above.

The rolling load is converted into a voltage corresponding to the load by the rolling load converter 21, and is input to the AD (analog to digital) converter 31 of the roll eccentricity removing device 30. The rotation angle of the roll is converted into a pulse signal corresponding to the rotation angle by rotation angle converters 22 and 23, and is input to the pulse input section 32 of the roll eccentricity removing device 30. Based on these input signals, the central processing unit 33 of the roll eccentricity removing device 30 calculates the eccentricity of the roll using a fast Fourier transform technique.

When measuring variations in rolling load in this way, it is necessary to reduce measurement errors.

However, the fluctuation of the rolling load is several tens of minutes compared to the rolling load.
Since it is very small, ranging from - to several hundred valves, for example, when a 12-bit AD converter is used, the resolution is 1/4096, and conversion cannot be performed with sufficient accuracy.

For this reason, the roll eccentricity removing device 30 uses a calculation means shown in FIG. 3.

That is, the central processing unit 33 outputs the predicted load from the DA converter 36, calculates the difference from the rolling load 34, amplifies this in the amplifier 35, and inputs it to the AD converter 31. By doing so, only the variation of the rolling load is subjected to A/D conversion by the AD converter 31, and the width of the AD converter 31 can be used effectively.

Therefore, the method of calculating the predicted load is usually that the rolling load when the rolling mill (rolls 11 and 12) bits the rolled material 13 is used as the first predicted load, and then the predicted load and the rolling load are combined. The method used was to correct the predicted load when the difference exceeded a certain limit.

In the conventional method as described above, the central processing unit 33 of the roll eccentricity removing device 30 had to perform an extra calculation of the amount of correction of the predicted load.

In other words, input the rolling load, perform operations such as taking an average over a certain period to remove the fluctuations, and combine this with the prediction direction.
It was necessary to compare the values and correct the predicted load if the difference exceeded a certain value.

In addition, if it becomes necessary to correct the predicted load as described above while measuring rolling load fluctuations in order to perform one fast Fourier transform, changing the predicted load will cause the measured data to change accordingly. This has the drawback of reducing the accuracy of the fast Fourier transform results because it causes a disturbance.

[Purpose of the invention]

The present invention overcomes the drawbacks of the conventional method as described above, eliminates the extra process of correcting the predicted load, and provides a rolling mill that does not deteriorate the accuracy of fast Fourier transform due to the correction of the predicted load. The purpose is to provide a method for measuring roll eccentricity.

[Summary of the invention]

In order to achieve the above object, the present invention performs fast Fourier transform multiple times and corrects the predicted load using the direct current component of the previous fast Fourier transform results. It is.

That is, by performing fast Fourier transform, the fundamental wave component and the second harmonic component of the rolling load fluctuation are determined by using the rotational angular frequency of the roll as the fundamental frequency.

At the same time as the third harmonic base component is derived,
The DC component that does not depend on the rotational angular frequency of the roll is determined,
Since this DC component itself corresponds to the difference between the average rolling load and the predicted load, this DC component is used to correct the predicted load.

[Embodiments of the invention]

FIG. 1 shows a block diagram showing the principle circuit configuration of an embodiment of the present invention.

In this embodiment, if the predicted load is corrected during the measurement of rolling load fluctuations, this will cause a disturbance to the measurement data and reduce the accuracy of the fast Fourier transform. Let's do it.

When the predicted load correction 42 is performed on the true rolling load variation 41 as shown in FIG. 1, the measured rolling load variation 43 becomes as shown in the block.

However, the fast Fourier transform 44 that is originally required must be for the true rolling load variation 41.

Therefore, by subtracting the fast Fourier transform 45 for the predicted load correction from the fast Fourier transform 46 for the measurement data, the fast Fourier transform 44 that is the true load variation to be sought can be obtained.

It should be noted here that since the predicted load is corrected in steps, the fast Fourier transform 45 does not need to be performed by the central processing unit 33 of the roll eccentricity removal device 30, but can be calculated in advance on a desk. There is a point where you can leave it.

In other words, to simplify the explanation, if we assume that the time axis is t, the measurement period is T, and the predicted load correction amount is -1, and the correction is performed at the midpoint of the measurement period, the Fourier transform result is expressed as It is expressed as

π T3 T 5T By subtracting this value from the value calculated by the fast Fourier transform 46 for the measurement data, the value of the fast Fourier transform 44, which is the true load fluctuation, is derived.

In the previous example, we explained the case where there was a -1 correction at the midpoint of the measurement period, but in another example of the present invention, when the correction amount is different, the correction is not at the midpoint but at another timing. It is also easy to apply the correction when the correction is performed multiple times during the measurement period.

〔Effect of the invention〕

Thus, by using the measurement method according to the invention,
The extra calculation of determining the amount of correction of the predicted load is unnecessary, and the load on the central processing unit 33 of the roll eccentricity removing device 30 can be reduced.

Further, by using the Fourier transform 45 for the fluctuation of the predicted load calculated in advance and correcting the fast Fourier transform 46 for the measurement data, it is possible to eliminate errors in the fast Fourier transform caused by correction of the predicted load.

Therefore, the present invention greatly contributes to this field.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the principle circuit configuration of an embodiment of the present invention, Fig. 2 is a diagram showing a method for measuring rolling load of a roll eccentricity removing device, and Fig. 3 is a circuit for improving measurement accuracy. It is an explanatory diagram. 11... Upper roll, 12... Lower roll, 13...
Rolled material, 21... Rolling load converter, 22... Upper roll rotation angle converter, 23... Lower roll rotation angle converter,
30... Roll eccentricity removal device, 31... AD conversion section, 32... Pulse input section, 33... Central processing unit,
34... Rolling load, 35... Amplifying section, 36... D
A conversion unit, 41... Load variation of decay, 42... Correction of predicted load, 4, 3... Load variation to be measured, 44...
・Fast Fourier transform for measurement data, 45...Fast Fourier transform for correction of predicted load, 46...Fast Fourier transform to obtain. Applicant's agent Mr. Sato Figure 1

Claims (1)

[Claims] 1. When the material to be rolled is caught between the upper roll and lower roll of the rolling machine and rolled, the deviation between the rolling load and the predicted load is detected by AD conversion, and the upper roll and the rotation angle of the lower roll are converted into pulse signals and derived via pulse input means, and from the deviation between these rolling loads and predicted loads and the rotation angles of the upper roll and lower roll, fast Fourier transform is performed in the central processing unit. In the method of calculating the amount of roll eccentricity using the method described above, the predicted load is corrected using a DC component that does not depend on the rotational angular frequency of the roll calculated by fast Fourier transform, and the measured load fluctuation is expressed. A rolling method characterized in that a fast Fourier transformed value indicating the desired amount of roll eccentricity is calculated by calculating a value of the fast Fourier transformed result for the correction of the predicted load from a value of the fast Fourier transformed result for the measurement data. How to measure machine roll eccentricity. 2. The method for measuring roll eccentricity of a rolling mill according to claim 1, wherein the predicted load consisting of the DC component is corrected in steps.