JPH04361816A - Method for controlling plate thickness of rolled stock in rolling mill - Google Patents

Abstract

PURPOSE:To control the main component of variation of plate thickness caused by the eccentricity of a roll in a rolling stand by changing the timing of output of a control signal. CONSTITUTION:When a plate thickness between the i-th stand 2 and the +1-th stand 3 in cold tandem rolling mills is detected by a thickness meter 4, the deviation of this detected thickness to a target thickness is tracked by a tracking circuit 6, a thickness control signal is outputted at a specified timing to control the speed controlling part 8 of a main motor and to control the thickness of a rolled stock 1, a time correction is carried out to the output timing of this thickness deviation signal considering the response characteristics of the main motor to control the thickness so that the maximum depression effect can be obtained with a specified frequency.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention detects or estimates the thickness of a rolled material, tracks the detected or estimated thickness, and uses the rotational speed or rolling position of a roll of a rolling stand or the position of a reel at a specific timing. The present invention relates to a method for controlling the thickness of a rolled material in a rolling mill, which is suitable for controlling the thickness by controlling the rotation speed in a feedforward manner.

0002

2. Description of the Related Art Various thickness control techniques are employed in rolling mills for the purpose of controlling the thickness of rolled material to a target value. Many ideas for such plate thickness control techniques have been put into practical use.

However, there are a limited number of plate thickness control techniques that are versatile, widely known, and used. For example, feedforward automatic gauge control (hereinafter abbreviated as FF/AGC) is a widely used sheet thickness control method in cold rolling.
There is.

[0004] Here, FF/AGC (FF/AGC between stands) has been adopted to control plate thickness between stands of a cold tandem rolling mill.
Taking FF/AGC as an example, the operation of FF/AGC will be explained below.

That is, the plate thickness of the rolled material (between the i-th to i+1 stands) is detected between certain stands, the detected plate thickness is tracked by the tracking circuit of the plate thickness control device, and the plate thickness detection point is set at the next stage. When the i-th stand is directly below the roll, the roll rotation speed of the i-th stand in the previous stage is controlled. As a result, the rear tension of the i+1st stand where the applicable plate thickness detection point exists in the roll bite is changed, and the rolling reduction rate at which the applicable plate thickness detection point is rolled by the i+1 stand is changed, and the applicable plate thickness detection point is The target thickness is obtained at the exit side of the i-th +1 stand.

[0006]

[Problems to be Solved by the Invention] However, in the conventional inter-stand FF/AGC, since dynamic correction is not taken into account in the tracking circuit, the rolling speed is particularly high when the rolling speed changes. When this occurs, a delay in the detection signal of the plate thickness gauge and a delay in response to the speed command of the rolling mill main motor become obvious.

Therefore, the conventional inter-stand FF/AGC
In this case, there is a problem in that the suppressing function of plate thickness variation is degraded due to the influence of the delay in the plate thickness-related detection signal and the response delay of the main motor.

That is, in the frequency response characteristics of the plate thickness detector and the main motor of the rolling mill during rolling, the gain generally decreases and the phase lags in a high frequency region. Usually, the response characteristic is approximated by a first-order delay or the like.

Further, the tracking circuit of the FF/AGC and the output timing adjustment of the control signal are normally fixedly adjusted on the premise of a specific detector response and traction motor response.

[0010] Also, most of the variation in plate thickness at the exit side of the rolling mill is caused by eccentricity of the rolls of the rolling mill, and therefore most of the variation in plate thickness is caused by periodicity approximated by a sine wave synchronized with the roll rotation frequency. has. Therefore, normally, the plate thickness variation has a dominant frequency that is approximately the same as the corresponding frequency fundamental wave of the backup roll of each stand.

From the above, when considering the tracking of FF/AGC, as the rolling speed increases, the phase delay in the plate thickness detection response of the plate thickness detector and the response to the speed command of the traction motor becomes large. turn into. Therefore, there is a delay in the correction operation of the roll circumferential speed of the rolling mill, which is expected to control plate thickness fluctuations, and as a result, the correction timing is delayed and the effectiveness of plate thickness control is reduced. This results in a decline in the inhibitory function.

The present invention has been made to solve the above-mentioned conventional problems, and is capable of accurately controlling plate thickness without being affected by delays in detecting or estimating plate thickness or delays in response of the rolling mill main motor. An object of the present invention is to provide a method for controlling the thickness of a rolled material in a rolling mill.

[0013]

[Means for Solving the Problems] The present invention detects or estimates the thickness of a rolled material, tracks the detected or estimated thickness, and outputs a thickness control signal at a specific timing to control the rolling stand. Response characteristics when detecting or estimating the thickness of a rolled material in a method of controlling the thickness of a rolled material in a rolling mill by manipulating the rotational speed or rolling position of a roll or the rotational speed of a reel, or the response characteristics of a main motor. The above problem is solved by taking at least one of these into consideration and performing time correction on the output timing of the plate thickness control signal.

[0014]

[Operation] The present inventor created the present invention by focusing on the fact that the plate thickness variation between the intermediate stands of a cold rolling mill is dominated by a sinusoidal periodicity that is approximately synchronized with the roll eccentricity. This is what I did.

The principle of the present invention will be explained below.

For example, FIG. 1 shows a general speed FF/AGC adopted in a cold tandem rolling mill (FF
・A configuration example of an automatic plate thickness control system (performing AGC) is shown below.

In FIG. 1, reference numeral 1 indicates a rolled material. Further, 2 and 3 are the rolling stands of the i-th and i-th +1st stages, and the figure shows the stands of the entire tandem rolling mill in which the sheet thickness is to be controlled by FF/AGC. The rolling stands 2 and 3 roll the rolling material 1 while conveying it in the direction of the arrow.

Further, 4 is a thickness gauge, and the i-th stand 2
The thickness of the rolled material 1 on the outlet side is detected and input to the tracking circuit 6.

The tracking circuit 6 tracks the detected plate thickness signal on the rolled material 1 and inputs it to the control circuit 5. The control circuit 5 tracks the detected plate thickness signal to within the roll bite of the i-th +1 stand 3 based on the tracking input, and sends a speed change command to the i-th stand 2 to the traction motor speed control unit in accordance with fluctuations in the outlet side plate thickness. Enter 8.

The main motor speed control unit 8 changes the speed of the i-th stand 2 according to the input speed change command, and
The tension of the rolled material 1 between the stand 2 and the i+1 stand 3 is changed. As a result, the thickness of the plate immediately below the i-th +1 stand 3 is controlled, and fluctuations in the thickness of the outlet side of the stand 3 are suppressed.

[0021] Next, an example of a method for calculating the speed change command will be described.

Assuming that there is no change in the strip width before and after rolling,
Since the mass flow is constant at the entrance and exit sides of a specific stand, if the speed vi of the i-th stand is changed by Δvi (amount of change in rolling speed of the i-th stand), the i-th +1
The stand exit side plate thickness change amount Δhi+1 is expressed by the following equation (1).

[0023]

[Math 1]

[0024] However, hi: i stand exit side plate thickness;
fi: i stand advancement rate, fi+1: i +1 stand advancement rate, vi+1: i +1 stand rolling speed.

Further, in the i+1st stand, the exit side plate thickness variation Δhi+1 has a relationship with the inlet side plate thickness variation ΔHi+1 of the i+1st stand 3 as shown in the following equation (2).

[0026]

[Math 2]

However, Mi+1: i +1 stand mill constant, Qi+1: i +1 stand plastic constant.

From the above equations (1) and (2), the ratio Δ of the rolling speed variation Δvi of the i-th stand to the rolling speed vi is
vi/vi is expressed as the following equation (3).

[0029]

[Math 3]

Furthermore, since the mass flow is constant, there is a relationship approximately expressed by the following equation (4) between the exit side plate thicknesses hi and hi+1 of the i-th stand and the i-th stand, respectively.

[0031]

[Math 4]

[0032] Also, considering the advance rate fi, etc., the following equation (5)
However, the following equation (6) is further obtained.

[0033]

[Math 5]

[0034]

[Math 6]

As a result, the following relationship (7) is established.

[0036]

[Math 7]

Therefore, approximately speaking, if a speed change amount with the same ratio as the ratio Δhi/hi of plate thickness change on the exit side of the i-th stand and opposite in polarity is given as a speed change command, the i-th +1
Fluctuations in the plate thickness on the exit side of the stand can be suppressed. A typical speed FF/FF controls plate thickness using such speed change commands.
This is the principle of the ACG system.

However, when applying this speed FF/AGC to an actual machine, as shown in FIG. It is necessary to consider the existence of delays.

FIG. 3 shows a typical example of the plate thickness detection response of the thickness gauge 4. FIG. 3 shows an example of the frequency characteristics of a gamma ray thickness meter with a detection time constant of 50 msec. In this case, the measured plate thickness is approximately 0.1 mm for the base and approximately 0.01 mm for the change in plate thickness.
Met. Further, a typical example of the response characteristics of the main motor of a rolling mill is shown in FIG. In this case, the response angular frequency ω=20rad/
s, time constant T=0.05 when approximating first-order lag (
sec) was shown.

As shown in FIGS. 3 and 4, each response has a frequency characteristic that approximates a first-order lag. Further, in the thickness gauge 4 shown in FIG. 3, the gain decreases and the phase lags in the high frequency range.

FIG. 5 shows an example of the results of frequency analysis of plate thickness fluctuations in a cold tandem rolling mill. FIG. 5 shows the spectral intensity with respect to the board thickness deviation variation frequency, and shows each roll (for example, the third stand backup roll (#3BUR)) corresponding to the analyzed frequency component. As can be seen from FIG. 5, most of the plate thickness variations are caused by roll eccentricity of one of the stands. Further, the waveform of this plate thickness variation is a sine wave that is synchronized with the roll rotation frequency.

[0042] The principle and plate thickness of the above speed FF/AGC system,
The present invention will be explained based on the relationship between motor speed deviations.

First, the traction motor response is approximated as a first-order lag element. For example, the angular frequency of the traction motor response ωm = 1
If 0 (rad/s), response frequency fm=ωm
/2π=1.592 (Hz), and period Tm=
1/ωm = 0.1 (second). In general, the first-order lag response characteristic H(s) is expressed by the following equation (8), its gain is expressed by the following equation (9), and its phase angle H is expressed by the following equation (10).

[0044]

[Math. 8]

[0045]

[Math. 9]

[0046]

[Math. 10]

[0047] However, s is a Laplace operator.

Further, the plate thickness deviation Δhd signal is expressed as a sine wave as shown in the following equation (11).

[0049]

[Math. 11]

This plate thickness deviation Δhd signal is given as a speed change command for the main motor of the rolling mill according to the above equation (7),
If an attempt is made to suppress the plate thickness deviation Δhd, the plate thickness response Δhm at the main motor output end is expressed by the following equation (12).

[0051]

[Math. 12]

##EQU1## where G is a gain and φ is a phase delay.

The plate thickness deviation Δhc remaining after performing the suppression control on the plate thickness deviation Δhd as described above is calculated by the following formula (
13).

[0054]

[Math. 13]

Note that the angle ψ is determined by the following equation (14).

[0056]

[Math. 14]

With respect to the sinusoidal plate thickness deviation Δhd of the angular frequency ω, the remaining plate thickness deviation Δhc is finally calculated by the following equation (1
5).

[0058]

[Math. 15]

T is a time constant.

Here, FIG. 6 shows the residual plate thickness deviation Δhc
An example of the frequency characteristics of the suppression rate is shown below. In the example shown in the figure, the main motor response frequency ωm = 10 (rad/s) (approximately 1.5Hz
), the case where gain C=1.0 is shown.

As mentioned above, since the main motor of a rolling mill has a response delay, it is impossible to completely suppress plate thickness fluctuations (having a roll eccentricity frequency) caused by roll eccentricity, as shown in FIG. 6, for example. Can not do it.

Therefore, the inventor came up with the idea of correcting the output timing of the plate thickness control signal. For example, in the case of a main motor of a rolling mill, the output timing is accelerated by the time required for the motor to respond.

[0063] The ability to suppress fluctuations in the frequency range of plate thickness fluctuations caused by roll eccentricity can be improved. This signal output timing can be corrected by appropriately time-correcting the tracking of the FF/AGC. In this timing correction, the following assumptions are made.

That is, a gain C is given to the plate thickness control output. Also, the effect of correcting FF/AGC tracking is as follows.
In expressing the control output, it is expressed as a phase delay φ0.

The control output Δhm' when the output timing at the main motor output end is corrected is expressed by the following equation (16).

[0066]

[Math. 16]

Control output Δhm expressed by this equation (16)
The residual thickness deviation Δhc' with respect to ' is calculated by the following formula (17)
becomes.

[0068]

[Math. 17]

[0069] However, the angle ψ' is expressed by the following equation (18).

[0070]

[Math. 18]

The gain C in equations (16) and (17),
When the phase delay φ is expressed by the angular frequency ω, the residual amount Δ
The absolute value of hc' is expressed by the following equation (19).

[0072]

[Math. 19]

However, ω0 is the phase shift delay φ0 expressed in terms of angular frequency.

For example, when attempting to suppress plate thickness deviation in an actual machine, ω0 (corrected angular frequency) in equation (19) may be set as the roll eccentric frequency. FIG. 7 shows an example of the correction results when the roll eccentricity frequency ωc = 10 (rad/s) is approximately 1.5 Hz. In addition, in FIG. 7, correction was made under the same rolling conditions as in FIG. 6.

It is understood from FIG. 7 that the suppressing effect is remarkable.

An example of the calculation results when the plate thickness changing frequency is 1.5 Hz will be explained with reference to FIGS. 6 and 7. This plate thickness variation frequency corresponds to the backup roll eccentricity frequency of the front stage stand in a cold tandem rolling mill. If no correction is made, the frequency is 1.5Hz as shown in Figure 6.
With respect to sinusoidal fluctuations in the thickness, only about 15% of the fluctuation suppression effect (85% of the plate thickness fluctuation remains) can be obtained. On the other hand, if the output timing of the FF/AGC control signal is corrected, as shown in FIG. 7, it is possible to suppress almost 100% of a specific fluctuation frequency. However, the effect of suppressing plate thickness fluctuations in other frequency ranges is low, but as mentioned earlier, plate thickness fluctuations in rolling mills can be controlled at a specific frequency synchronized with the roll rotation speed. A component having synchronization as a fundamental wave component is dominant, and suppressing fluctuations in a specific frequency is more effective in controlling the plate thickness.

[0077] In the above explanation, the lag that exists between the rolling mill types of the control signal is taken into consideration on the premise that the response of the rolling mill main motor to the control signal can be approximated to a first-order lag. . Similarly, when detecting plate thickness with a thickness gauge or estimating plate thickness, there are also problems particularly with phase lag.

An example of the response of the thickness gauge is shown in FIG. 3 above. According to FIG. 3, the response of the thickness gauge is approximately a first-order lag.

In the case of a thickness gauge, since the signal is a detection signal for plate thickness, only its phase delay is particularly problematic from the viewpoint of FF/AGC. If this delay is considered as a first-order delay, the final equation will be similar to equation (15) above.

The present invention was created based on the above knowledge. According to the present invention, it is possible to perform control so that the suppression ability in a specific frequency range corresponding to the sinusoidal disturbance that is the main cause of plate thickness variation is maximized, and
It is possible to suppress plate thickness fluctuations, which was difficult in F-AGC from the viewpoint of response speed, and thereby improve plate thickness accuracy.

[0081]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In this embodiment, in the cold tandem rolling mill shown in FIG. Tracking of plate thickness signal is described above (17
This is a plate thickness control device that includes a time correction circuit 7 that performs correction based on equations such as ).

The time correction circuit 7 inputs the rolling speed from the traction motor speed control section 8, and calculates the detection response delay of the thickness gauge 4, the calculation delay of the control circuit, and the traction motor response of the rolling mill from the rolling speed at that time. The correction time is determined by calculating the delay, and the correction time is input to the tracking circuit 6, and the timing of outputting the control signal to the control circuit 5 is changed according to the correction time.

The operation of the embodiment will be explained below.

During rolling with the cold tandem rolling mill shown in FIG. The tracking circuit 6 tracks the plate thickness deviation between the detected plate thickness and the target plate thickness on the rolled material 1, and inputs a tracking signal to the control circuit 5.

Based on the input plate thickness signal, the control circuit 5 outputs a speed change command to the traction motor speed control unit 8 when the plate thickness detection point reaches the next stand, i+1th stand 3. , change the roll rotation speed of the i-th stand 2. As a result, the i-th stand 2 and the i-th stand +1
Correcting the tension between the stands 3, and thus the i-th +1
Controls the plate thickness directly below stand 3.

Here, the rolling speed is input from the main motor speed control section 8 to the time correction circuit 7, and the correction circuit 7 calculates the detection response delay of the thickness gauge 4 from the rolling speed at the time of input, The correction time is determined by calculating the calculation delay of the control circuit 5 and the formula response delay of the rolling mill. Since the correction is made at the output timing, applying the correction angular frequency ω0 from the above equations (16) to (18) makes it possible to attenuate a specific residual plate thickness deviation by up to nearly 100% as shown in FIG. 7 above.

[0088] Although the above embodiments show the case where the present invention is adopted in a cold tandem rolling mill, the rolling mill that adopts the present invention to control plate thickness is applicable to this type of cold tandem rolling mill. The present invention is not limited to this rolling mill, but can be implemented in various other types of rolling mills.

[0089] Furthermore, in the above embodiment, the above (16) to (1)
Although the tracking correction of the detected plate thickness was carried out from equation 8) in consideration of the response delay of the rolling mill main motor, the scope of application of the present invention is not limited to this.

That is, tracking correction can be performed by considering both the response delay of the rolling mill main motor and the response delay of the thickness gauge, or by considering either of them independently. Further, the thickness gauge in this case is not limited to one that directly detects the plate thickness, but the present invention can also be applied to a case where the thickness gauge is used to estimate the plate thickness by calculation or the like.

[0091]

As explained above, according to the present invention, it is possible to suppress plate thickness fluctuations over a wide range of rolling speeds, which was impossible with conventional feedforward AGC from the viewpoint of response speed, and in particular to suppress roll eccentricity. It is possible to suppress plate thickness fluctuations with high precision. Therefore, excellent effects such as improvement in plate thickness accuracy can be obtained.

[Brief explanation of drawings]

FIG. 1 is a layout diagram including a partial block diagram showing the configuration of a plate thickness control device for a cold tandem rolling mill according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an example of a control signal delay element for explaining the principle of the present invention.

FIG. 3 is a diagram similarly showing an example of a detection signal frequency characteristic of a thickness gauge.

FIG. 4 is a diagram showing an example of the step response characteristic of the rolling mill main motor.

FIG. 5 is a diagram showing an example of an analysis result of output side plate thickness deviation signal output of a cold tandem rolling mill.

FIG. 6 is a diagram showing an example of the effect of suppressing plate thickness variation when no tracking correction is performed.

FIG. 7 is a diagram showing an example of the effect of suppressing plate thickness variation when tracking correction is performed.

[Explanation of symbols]

1...Rolled material, 2...I-th stand, 3...i-th +1 stand, 4...thickness gauge, 5...control circuit, 6...tracking circuit, 7...Tracking time correction circuit, 8...Rolling mill main motor speed control section.

Claims (1)

[Claims] Claim 1: Detecting or estimating the plate thickness of a rolled material, tracking the detected or estimated plate thickness, and outputting a plate thickness control signal at a specific timing to determine the rotational speed of the roll of a rolling stand, the rolling position, or the reel. In the method of controlling the thickness of the rolled material in the rolling mill by manipulating the rotation speed of the rolling mill, at least one of the response characteristics when detecting or estimating the thickness of the rolled material or the response characteristics of the traction motor is considered. A method for controlling the thickness of a rolled material in a rolling mill, comprising: time-correcting the output timing of a thickness control signal.