JP2583815B2 - Thickness control device for cold rolling mill - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet thickness control device for detecting a work roll gap with a contact roll gap detection device and feeding it back to a rolling mill.

[0002]

2. Description of the Related Art Conventionally, as a method of controlling the thickness of a rolling mill, there are the following methods for detecting a thickness deviation. (1) The change in the thickness of the entry side is determined from the result of detection by the thickness detection means attached to the entry side of the rolling mill, and the amount of reduction control is determined. Feed-forward AGC that adjusts the amount of rolling down. (2) A monitor AGC that detects a change in sheet thickness by means of a sheet thickness detecting means attached to the exit side of the rolling mill and adjusts the rolling reduction by proportional integral control based on the detected change in sheet thickness. (3) Mill constant control for detecting the change in the thickness of the entry side as a change in the rolling load and adjusting the roll reduction amount in accordance with the detected change in the load. (4) AGC that detects the gap between the work rolls in a non-contact manner and feeds back to the rolling mill.

[0003] However, each of the above control methods has the following disadvantages. FF-AG of the above (1)
C is limited to control only the mill entry side thickness variation. In the monitor AGC of the above (2), since there is a dead time element until the plate thickness is detected, the response frequency range of the control becomes low. In the mill constant control of (3) above, the roll eccentricity is promoted in the case of the high mill constant control, and in the case of a material having a low deformation resistance, the change in the rolling load due to a change in the sheet thickness is small, so that the detection cannot be performed due to the detection limit of the rolling load meter. Or the change in the rolling load is attenuated by the friction loss between the roll chock and the housing before reaching the rolling load cell, and the thickness variation itself cannot be detected. In the above (4), a laser displacement meter, an eddy current displacement meter, or the like is used as a sensor for detecting the roll gap in a non-contact manner. However, since the detection is performed in an environment in which rolling oil, roll coolant, or the like is scattered, the rolling is performed. The detection error due to oil or roll coolant is large, and it is difficult to control the thickness accurately. Further, when the entire frequency range that constitutes the change in the outlet side plate thickness is controlled using one control gain, there is a problem that the control effect is reduced because the control gain is excessive or insufficient depending on the frequency. The conventional thickness control method has the above-mentioned drawbacks, and it has been difficult to achieve high-precision thickness accuracy.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, the present invention uses a contact-type roll gap detecting device in which a detection error due to rolling oil or roll coolant is unlikely to occur, has no dead time factor relating to sheet thickness detection, and It is an object of the present invention to provide a thickness control device capable of controlling a disturbance other than the mill thickness variation on the mill entrance side.

[0005]

According to the present invention, as a means for detecting a change in sheet thickness, a change in the gap between upper and lower work rolls directly linked to a change in sheet thickness is directly detected by a contact-type roll gap detection means. The rolling mill is controlled so that the detected value of the roll gap becomes a constant value. In this way, the plate thickness constant control is to be performed. Further, in the frequency range below the maximum controllable frequency which is inevitably determined by the roll gap detector and the operation end (rolling position adjusting means, rolling speed adjusting means, etc.), the signal of the thickness change is separated by the frequency band. An optimum control gain can be added by extracting only a specific frequency range.

That is, according to the present invention, there is provided a contact-type roll gap detecting means for detecting a roll gap between upper and lower work rolls at a body end of a work roll, and a roll gap detection signal from the roll gap detecting means. Calculation means for determining the operation amount of any of the rolling position adjustment means for adjusting the roll position of the work roll, or the rolling speed adjustment means for adjusting the roll rotation speed of the work roll,
A thickness control device for a cold rolling mill, which is provided with a thickness detecting means disposed on the exit side of the rolling mill.

Further, each means will be described in detail with reference to FIG. Contact type roll gap detecting means 3
As the rolling position adjusting means 4, a hydraulic rolling cylinder or an electric rolling device is used, and the rolling speed adjusting means 5 is used.
For example, a motor for driving a rolling mill is used.

Further, the calculating means 6 comprises lock-on-hold circuits 9 and 12, a low-pass filter circuit 10, a band-pass filter circuit 13, and proportional-integral control calculating devices 11 and 14.

The lock-on-hold circuits 9 and 12 are circuits for generating a deviation signal τ of the roll gap detector signal δ from a certain reference. The certain reference is the roll gap detector signal δ at the start of the control or the changed roll gap detector signal δ when the operation end is manually intervened.

The low-pass filter circuit 10 has a frequency fa
This is a circuit for cutting a signal of 1 (Hz) or more.
Here, fa1 is the upper limit value of the frequency to be controlled, and can be arbitrarily determined.

The band pass filter circuit 13 has a frequency f
This is a circuit for cutting signals of b1 (Hz) or less and fb2 (Hz) or more. Although fb1 may be determined arbitrarily, fb2 is determined by the phase delay characteristics of the contact-type roll gap detection means 3 and the operation end, the transfer function characteristics of the bandpass filter 13, and the like. An example of determining fb2 will be described below. The transfer functions of the contact-type roll gap detecting means and the operation terminal 4 or 5 are represented by Gg (S) and Gr, respectively.
Assuming that (S), the phase delay θ of the signal due to this can be expressed by the following equation. θ = θg + θr Here, θg indicates a phase delay caused by the contact-type roll gap detecting means 3, and θr indicates a phase delay caused by the operation end. Here, if the frequency f90 (Hz) at which θ = −90 ° is considered as a measure of the response, fb2 = f90 can be obtained. Also, the bandpass filter circuit 1
Gf (s) = T1 · S / (1 + T1 · S) (1 + T2 ·
S) (where T1 and T2 are constants), the constant T2 that determines the high frequency cutoff frequency of the bandpass filter circuit 13 is expressed by the following equation. T2 = 1 / (2 · π · f90) Similarly, the constant T1 is T1 = 1 / (2 · π · fb1).

The proportional-integral control arithmetic unit 11 has a control output ε
This is a device for calculating 1 and performs a calculation represented by the following equation. ε1 = Δδ1 · α · G1 · (1 + P1 · S) / S Here, α is an influence coefficient, and is expressed as follows. α = dc / dh (in the case of adjusting the rolling position) α = dv / dh (in the case of adjusting the rolling speed) Here, c is the rolling position, v is the rolling speed, h is the exit side plate thickness,
Δδ1 is an output signal of the low-pass filter circuit 10, G1 and P1 are control gains, and S is a Laplace operator. The switches 21 and 23 are operation end selection switches. When the switch 21 is closed, the rolling position adjusting means 4 operates, and when the switch 23 is closed, the rolling speed adjusting means 5 operates. The rolling position adjusting means 4 and the rolling speed adjusting means 5 operate selectively, and which adjusting means is operated is determined by a plastic coefficient, a frequency of a thickness variation to be controlled, and the like.

The proportional-integral control arithmetic unit 14 has a control output ε
2 is a device for calculating ε2, and ε2 performs a calculation represented by the following equation. ε2 = Δδ2 · α · G2 · (1 + P2 · S) / S Here, Δδ2 is an output signal of the band-pass filter circuit 13, and G2 and P2 are control gains. The switches 19 and 20 are selection switches for the filter circuit and the subsequent proportional-integral control operation device 14, and the switch 2
Reference numerals 2 and 24 are selection switches at the operation end.

As the sheet thickness detecting means 7, both non-contact type and contact type sheet thickness detecting means can be used. For the non-contact type, a measuring instrument using, for example, X-rays, gamma rays, β-rays, etc. is used, and for the contact type, a former gauge (trade name of Former), a flying micrometer, or the like can be used.

The proportional-integral control arithmetic unit 8 calculates a control output ε3 for adjusting the rolling position adjusting means 4 or the rolling speed adjusting means 5 from the thickness detection signal Δδ3 detected by the thickness detecting means 7. Here, ε3 is represented by the following equation. ε3 = △ δ3 · α · G3 · (1 + P3 · S) / S The switches 25 and 26 are switches for selecting the operation terminal 4 or 5.

[0016]

The operation of the present invention will be described with reference to FIGS. The upper and lower work roll body end gaps a are detected by the contact type roll gap detection means 3 installed on both body ends 2 of the work roll 1.
The output signal δ corresponding to the variation of the data is supplied to the arithmetic unit 6.
Arithmetic unit 6 has switches 19 and 2 for switching control methods.
0, and an arbitrary control method can be selected by a switching device (not shown). In general, if the factors of the thickness variation are raised, (1) the thickness variation occurring in the process before the target process (so-called thickness variation on the mill entry side) (2) the thickness variation occurring during rolling in the rolling process ( (Roll eccentricity, change in oil film thickness of oil film bearing of counter roll, etc.) The cycle of the plate thickness fluctuation by the above is approximately 0.1 second (10H
It is distributed over a wide frequency band from z) to several tens of seconds. In particular, in the case of (1), the frequency of plate thickness variation becomes wide due to the number of stands, reduction ratio distribution, and the like in the pre-rolling step. Further, in many cases, a tandem-type rolling mill having multiple stands is usually used in the pre-rolling process, which causes a thickness variation at various frequencies. Which combination circuit is used to use the sheet thickness control device of the present invention is determined by a frequency of sheet thickness fluctuation to be controlled, a plastic coefficient, and the like. 4 below
Here are the types of operation combinations.

Switch 19 Switch 20 Switch 25 or 26 Circuit 1: On, Off, Off Circuit 2: Off, On, Off Circuit 3: On, On, Off Circuit 4: Off, On, On

In the arithmetic unit 6, δ is output by the lock-on-hold circuits 9 and 12 as a deviation signal τ from the control start time or the change time when the operation end is manually interposed. When a plurality of contact-type roll gap detecting means 3 are installed, output signals from each means are averaged and used as a deviation signal τ.

When the circuit 1 is used, the average deviation signal τ is converted to a frequency fa1 (H
z) The above components are cut and input to the proportional-integral-control arithmetic unit 11 as a signal 制 御 δ1. Here, fa1 is the upper limit of the frequency to be controlled. In the proportional-integral control arithmetic unit 11, the signal △ δ
The control output ε1 is calculated and output using the influence coefficient (calculated independently in the case of adjusting the rolling position and the case of adjusting the rolling speed) and the gain for proportional integration. The control output ε1 is output to the rolling-down position adjusting means 4 by closing the operation end selection switch 21. When the selection switch 23 is closed, the output is output to the rolling speed adjusting means 5, and the sheet thickness is automatically controlled by adjusting the rolling position and the rolling speed, respectively. The signal will be schematically described with reference to FIG. The signal δ detected by the roll gap detecting means 3 has various frequencies. Then, by passing through the roll-pass filter circuit 10, high-frequency components are removed, and △ δ1 is obtained. When this signal △ δ1 is input to the proportional-integral control arithmetic unit 11, a control output ε1 for a disturbance of an arbitrary low-frequency component is output. FIG. 4 schematically shows the results of these signal processings.

When the circuit 2 is used, the average deviation signal τ is
The frequency fb1 (H
z) The signal below fb2 (Hz) and above is cut off,
The signal △ δ2 is input to the following proportional-integral control arithmetic unit. Here, fb1 may be arbitrarily determined. However, fb2 is limited by the roll gap detecting means, the phase delay characteristics of the operation ends, the transfer function characteristics of the band-pass filter, and the like. The proportional-integral control arithmetic unit 14 receives the input △ δ2
Then, as shown in the above equation, the control output ε2 is calculated and output using the influence coefficient, the gain for proportional integration control, and the like. The control output ε2 is output to the rolling-down position adjusting means 4 by closing the operation end selection switch 22. When the selection switch 24 is closed, the output is output to the rolling speed adjusting means 5, and the thickness is automatically controlled by adjusting the rolling position and the rolling speed, respectively. The signal will be schematically described with reference to FIG. The signal δ detected by the roll gap detecting means 3 passes through a band-pass filter circuit 13, from which low-frequency components and high-frequency components are removed, and an arbitrary frequency component signal △ δ2 is extracted. When this signal △ δ2 is input to the proportional-integral control arithmetic unit 14, a control output ε2 for disturbance of an arbitrary frequency component is output. FIG. 6 schematically shows the results of these signal processings.

When the circuit 3 is used, the average deviation signal τ is
The low-pass filter circuit 10 described in the case of using the circuit 1 and the band-pass filter circuit 13 described in the circuit 2 are output in parallel to each other. The operating end adjusters 21, 22, 23, 2 with ε2 respectively selected
4 is output to one or a plurality of adjusters, and the thickness is automatically controlled by adjusting the rolling position and the rolling speed.

When the circuit 4 is used, the average deviation signal τ is input to the band-pass filter circuit 13, and the subsequent operation is as described in the case where the circuit 2 is used. Also,
The thickness detection signal Δδ3 detected by the thickness detection means 7 provided on the rolling mill exit side separately from the average deviation signal τ is output to the proportional-integral control arithmetic unit 8. In this case, as the sheet thickness detection signal Δδ3, a deviation signal from the set sheet thickness (the deviation becomes 0 when the set sheet thickness is reached) is usually used.
When the thickness detection signal Δδ3 is the absolute value of the thickness, the thickness deviation signal Δδ4 may be calculated and output, for example, by the following equation. Δδ4 = (absolute value of measured plate thickness) − (set plate thickness) The proportional-integral control calculating device 8 calculates the control output ε3 using the influence coefficient, the proportional-integral gain, and the like as shown in the above-described formula. In this output control, the control result can be monitored by measuring the thickness after rolling by the thickness detecting means 7 on the exit side of the rolling mill, so that the thickness after rolling is as expected with respect to the target value. Can be guaranteed whether or not. That is,
Always monitor the deviation between the control result, the thickness and the target thickness,
Since the correction is performed, there is an advantage that the control with the target plate thickness as the center value can be more reliably performed. Control output ε3
Is output to the rolling-down position adjusting means 4 by closing the operating end selection switch 25, and is output to the rolling speed adjusting means 5 by closing the selection switch 26. Are combined with the control output ε2 created by the above, and the thickness is automatically controlled by adjusting the rolling position and the rolling speed, respectively.
In any of the above methods, any one of the rolling position and the rolling speed can be selected as the control operation end. Can be determined by

[0023]

Embodiments of the present invention will be described below. Example 1 Roll gap detection value δ by contact roll gap detection means 3
Into the deviation signal τ by the lock-on-hold circuit 9,
Further, only an arbitrary low-frequency component was extracted through the low-pass filter circuit 10, and the roll gap constant control was performed by the proportional-integral control arithmetic unit 11 via the rolling position adjusting means 4 or the rolling speed adjusting means 5. Conventional monitor AG
C performs plate thickness control in a low frequency band which is a control target. Since there is no dead time for detecting the plate thickness, the degree of freedom in control system design is increased, and the responsiveness of control can be easily improved. As a result of this example,
Approximately 7% variation in thickness accuracy without C control
Improved. A regular monitor with dead time AGC is
Only low frequency components of about 0.1 Hz or less can be controlled. On the other hand, the present embodiment is effective when the main purpose is to further enhance the ability to remove low frequency components because there is no dead time and the control response is fast.

Example 2 Roll gap detected value δ by contact roll gap detector 3
Is converted into a deviation signal τ by a lock-on-hold circuit 12, and an arbitrary high-frequency component and a low-frequency component are cut through a band-pass filter circuit 13 to extract only an arbitrary frequency disturbance. Via the adjusting means 4 or the rolling speed adjusting means 5,
Roll gap constant control was performed. As a result of this embodiment, the variation in the thickness accuracy when no AGC control was performed was improved by about 15%. The circuit according to the present embodiment works effectively when the frequency constituting the thickness variation is concentrated in a certain region and the frequency is a middle frequency (for example, 0.5 Hz to 5 Hz). In the first and second embodiments, the rolling speed adjusting stand may be an installation stand of the roll gap detecting device, or a stand before and after the stand, a tension reel, or the like.

Example 3 The roll gap constant control was performed by using both the circuits 1 and 2 described above. The respective control frequencies fa1, fb1, fb2 can be arbitrarily selected, but may be set to fa1 ≦ fb1 in order to prevent overcontrol. As a result of the present embodiment, the variation in plate thickness accuracy when no AGC control was performed was improved by about 22%.
The circuit of the present embodiment is effective when controlling the low frequency component and the middle frequency component simultaneously.

Embodiment 4 In this embodiment, the circuit 2 and the thickness detecting means are used in combination. That is, by using the rolling position adjusting means 4 or the rolling speed adjusting means 5 together with the rolling position adjusting means 5 by the proportional integral control arithmetic unit 8 based on the sheet thickness detecting means 7 provided on the rolling mill exit side. Constant control was implemented. Here, the thickness detecting means 7
If the upper limit of the control frequency is set to fm (a value that is inevitably determined as the configuration of the control system), the low-pass band of the band-pass filter circuit 13 of the second embodiment is prevented in order to prevent overcontrol as in the third embodiment. The cut frequency fb1 may be set to fm ≦ fb1. As a result of the present embodiment, the variation in plate thickness accuracy when no AGC control was performed was improved by about 20%.
In the circuit of this embodiment, the target thickness control at the exit side of the rolling mill is performed by a monitor AGC which is a conventional thickness control method, the absolute value of the thickness is guaranteed, and the thickness deviation of the mid-range frequency is further improved. This is an effective circuit when it is desired to remove the noise.

[0027]

According to the present invention using the contact-type roll gap detector, it is possible to perform high-response and high-accuracy plate thickness control without dead time relating to plate thickness detection. This can overcome the drawbacks of the conventional automatic thickness control as described below. (1) No dead time for detecting thickness change (monitor A
Overcoming GC). (2) Since the detected value of the roll gap detector corresponds to the change in the output-side sheet thickness itself, the disturbance that causes the change in the output-side sheet thickness is not limited to only the change in the original sheet thickness (overcoming FF-AGC). (3) It is not affected by the magnitude of the rolling load caused by the change in the thickness (overcoming the control of the mill constant). (4) Roll gap detection error due to rolling oil or coolant hardly occurs (overcoming AGC by detecting non-contact roll gap).

[Brief description of the drawings]

FIG. 1 is a flowchart of a sheet thickness control device of the present invention.

FIG. 2 is a schematic explanatory view of a sheet thickness control device of the present invention.

FIG. 3 is a signal flow diagram when the circuit 1 is used.

FIG. 4 is a schematic diagram of a signal processing result when the circuit 1 is used.

FIG. 5 is a signal flow diagram when the circuit 2 is used.

FIG. 6 is a schematic diagram of a signal processing result when the circuit 2 is used.

[Explanation of symbols]

 3 Contact roll gap detecting means 4 Roll-down position adjusting means 5 Rolling speed adjusting means 6 Calculating means 9, 12 Lock-on / hold circuit 10 Low-pass filter circuit 13 ……… Band pass filter circuit 8, 11, 14… Proportional integral control arithmetic unit

Claims (1)

(57) [Claims] A contact-type roll gap detecting means for detecting a roll gap between upper and lower work rolls at a body end of the work roll; and a roll gap detection signal from the roll gap detecting means, and calculating the work roll. Calculation means for determining the operation amount of either the rolling position adjustment means for adjusting the roll position, or the rolling speed adjustment means for adjusting the roll rotation speed of the work roll, and A thickness control device for a cold rolling mill, wherein the thickness control means is provided.