JPH0152084B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to tension detection in a rolled material during continuous rolling.

A conventional inter-stand tension detection method includes a method of determining the front tension between each stand from rolling torque, rolling force, and rear tension (front tension of the front stand).

The principle of the conventional tension detection method of this type will be explained below with reference to a continuous rolling apparatus shown in FIG. 1st
In the figure, 1 is the material to be rolled, 2 is the i-th stand, and 3
is the (i+1)th stand, Ti- ₁ is the rear tension of the i-th stand, Ti is the forward tension of the i-th stand, Gi
is the rolling torque of the i-th stand, and Pi is the rolling force of the i-th stand. At this time, the rolling torque Gi is expressed by the following formula.

Gi=ai・Pi+bi・Ti− ₁ −ci・Ti …(1) In equation (1), ai, bi, and ci are constants determined by one rolling condition, and ai, bi, and ci are the torque arm, We will call them the rear tension arm and the front tension arm.

From equation (1), the forward tension Ti can be calculated using the following equation.

Ti=(ai・Pi−Gi+bi・Ti− ₁ )/Ci (2) In equation (2), rolling force Pi, rolling torque Gi, and rear tension Ti− ₁ can be known by direct detection or calculation. On the other hand, ai, bi, and ci are constants determined by one rolling condition, but since they change during rolling, they are calculated as follows. First, bi and ci are calculated from the flat roll radius R'i, the inlet side plate thickness Hi, and the outlet side plate thickness hi using the following equation. bi=bi(R′i, Hi, hi)
...(3) ci = ci (R'i, Hi, hi) ...(4) Next, calculate the torque arm ai as ai = ai ^L + Δai ...(5). ai ^L is called the reference torque arm and is calculated as ai ^L = (Gi ^L −bi ^L・Ti ^L −1)/Pi ^L (6). Each value (Gi ^L , bi ^L , Ti ^L −1,
The timing to input (lock on) Pi ^L is as follows:
In order to set the standard torque arm ai ^L to the optimum value,
It is desirable that the forward tension Ti = 0 and immediately before the rolled material 1 is bitten by the i+1 stand 3. The timing at which each value is input in order to calculate the reference torque arm ai ^L in this way is called the lock-on timing at the i-stand. Δai is the amount of torque arm fluctuation after lock-on timing, and is calculated using the following formula.

Δai=Δai(ΔHi, Δhi, ΔRi′, Δkmi, ΔTi− ₁ ,
ΔTi) ...(7) However, in equation (7), ΔHi and Δhi are the amount of variation in thickness at the entrance and exit sides, ΔRi' is the amount of variation in the radius of the flat roll, and Δkmi
is the average deformation resistance variation, ΔTi− ₁ , ΔTi is backward,
This is the amount of front tension fluctuation. As mentioned above, the inter-stand tension Ti is obtained using equation (2), but in reality, for the torque caused by the rolling force in the first term on the right side of equation (1), (1) Since the tension torque in the second and third terms on the right side of the equation is quite small, the S/N ratio becomes small, and the calculated tension often contains considerable noise. Now, to explain this S/N ratio in a little more detail, in equation (1), the rolling torque Gi is the torque ai・Pi due to the rolling force and the torque due to the tension force.
Ci・Ti, bi・Ti― ₁ , but since we want to detect the torque due to tension, S (signal): Torque due to tension Ci・Ti, bi・Ti
- ₁ , N (noise): Torque ai・Pi due to rolling force. When viewed in this way, the actual S/N during rolling with a normal rolling mill is about a few percent, and the tension value (S) is detected from a very large noise (N).

Therefore, conventionally, as shown in Figure 2, the rear tension
Filter 4 with a fairly large time constant is applied to Ti- ₁ to remove noise from the waveform, and then at the lock-on timing, calculate the reference torque arm ai ^L using equation (6) using the reference torque arm calculation device 5. Also, during rolling, the tension calculation device 7 calculates a predetermined front tension based on the result of the torque arm variation calculation device 6 and the reference torque arm ai ^L based on equation (2).
I'm looking for Ti.

However, using the conventional method described above,
An online test revealed that an error occurred in front tension detection. That is, as shown in Fig. 3a, by applying a filter with a large time constant to the rear tension Ti- ₁ , the true rear tension waveform A1 after the rolled material is bitten by the i-th stand is filtered. Although the noise component is removed from the output signal waveform A2, since the phase is considerably delayed, there will be an error of ΔTi ^L - ₁ in the rear tension at the lock-on timing. Therefore, the following error will occur in the reference torque arm ai ^L expressed by equation (6): ai ^L = bi ^L ∆Ti ^L - ₁ / Pi ^L ...(8), and this error will cause the error in equation (2) ΔTi=bi・Pi・ΔTi ^L ― ₁ /ci・Pi ^L ……(9) will occur as a steady error in the forward tension calculated from The waveform at the next stand i+1 is shown in FIG. 3b. It is clear that the cause of this tension detection error is that the filter applying the rear tension causes a phase delay with respect to the true rear tension.

In the detection of the front tension in rolling stand i, the present invention provides a front tension in rolling stand i that is generated by filtering noise from the rear tension used in the detection, that is, the front tension in the previous rolling stand i-1. The purpose is to reduce detection errors.

Next, an embodiment of the present invention will be described. As shown in FIG. 4, the time constant of the rear tension filter 4 is made small before the lock-on timing to reduce the phase delay, and after the lock-on timing, the time constant of the rear tension filter 4 is made small. is equipped with a filter time constant changing device 8 for setting the time constant to an appropriate value in order to remove noise components of the detected tension waveform as much as possible.
As shown in , the filter time constant is made small before the lock-on timing, and the phase delay between the true rear tension waveform A1 after the rolled material is bitten by the i-th stand and the filter output side signal waveform A2 is made small. , reduce the rear tension error ΔTi ^L - ₁ . Therefore(9)
The steady error ΔTi of the forward tension given by the formula also becomes smaller.

Immediately before the lock-on timing, the filter time constant is made small, so the noise component increases relatively, but this is because errors due to noise can be absorbed by averaging multiple sampling values when performing lock-on. Can be done.

In this way, the filter time constant is made small until just before the lock-on timing to reduce the steady error in the forward tension, but after the lock-on timing, as is clear from equation (2), noise is added to the rear tension Ti- ₁ . and,
The noise is directly added to the calculated forward tension, and especially when considering unit tension, the thickness of the plate at the downstream stand becomes smaller, which tends to amplify the noise. Increase the constant to remove noise as much as possible.

In addition, FIG. 6 shows another example in which filters 4a and 4b having different time constants are used, and a filter switching device 9 is used to switch the filters at appropriate timing for the above purpose.

As described above, according to the present invention, the rolling load,
In tension detection that uses total torque and rear tension to determine front tension, a filter is provided for rear tension and the time constant of the filter is appropriately changed before and after locking on the reference torque arm, improving tension detection accuracy. .

To explain in more detail now, in the present invention,
For example, as shown in Fig. 7, the low time constant is switched to the high time constant at point P immediately after the lock-on timing at the i-th stand, but at this time, before switching, a high frequency signal is transmitted to some extent, but the fundamental wave signal rises quickly. , a value close to the true Ti ^R − ₁ , as shown in Figure 7.
Ti ^L - becomes ₁ . When determining the value Ti ^L - ₁ at this lock-on timing, multiple samplings are performed and averaged to reduce errors in high frequency components.

If a high time constant is used to cut out high frequency components from the beginning as in the conventional method, the tension Ti ^R - ₁ is the i-1th
Since the rise occurs with a first-order delayed response after the stand is engaged, the rise of the fundamental wave itself is also delayed, and the value Ti ^L ′- ₁ at the lock-on timing becomes the true value as shown in Fig. 7, although high frequency components can be cut out. This results in a large deviation.

It should be noted that high frequency noise can be cut by sampling, which is the same before and after switching, but the tension Ti- ₁ after the strip bites into the i-th stand becomes a step response waveform and changes rapidly, and before the lock-on timing, the tension Ti-1 changes rapidly. The closed-loop control that controls the
All you need to do is find the ai, and by averaging the sampling values multiple times during lock-on, you can obtain the accurate absolute value.
Dynamics of _{the tension Ti-1 is} not necessary, and there is sufficient time for sampling.

On the other hand, after switching, the closed-loop control of the tension Ti is started at a high speed and constant cycle when the strip is caught in the i+1th stand, so time-series dynamics of the tension Ti- ₁ are required, but the tension is maintained at a low time constant. If a Ti- ₁ signal is input, closed-loop control will be performed using a signal that includes high frequency components, which is unfavorable in terms of control system stability. In addition, the tension is filtered by sampling to cut out high frequency components.
Obtaining the dynamics of Ti- ₁ requires sampling time, which is difficult in terms of time compared to closed-loop control with high-speed constant cycles.

Therefore, after switching, it is necessary to remove high frequency components (noise) from the tension Ti- ₁ signal through a high time constant filter. Here, in terms of control response, passing through a high time constant filter tends to deteriorate the response, but it is preferable for operation to improve the stability of the control system even if this is sacrificed.

Note that the same concept can of course be used when determining the rear tension from the front tension at rolling stand i, and the same effect can be obtained even if the filter time constant is changed at the time of the i+1th stand. It is clear that there is hope.

[Brief explanation of drawings]

FIG. 1 is a side view showing the interrelationships among the front and rear tensions Ti, Ti- ₁ , rolling torque Gi, and rolling force Pi in the rolling stand 2. FIG. 2 is a block diagram showing the configuration of a conventional tension detection device. Third
Figures a and b are graphs showing the relationship between the stand-biting detection tension of the rolled material. FIG. 4 is a block diagram showing one apparatus configuration for implementing the present invention. FIGS. 5A and 5B are graphs showing the relationship between the change in filter time constant and the detected tension value when the present invention is implemented. FIG. 6 is a block diagram showing another apparatus configuration for implementing the present invention. FIG. 7 is a graph showing the relationship between the tension detection value obtained by the detection method of the present invention and the tension detection value obtained by the conventional detection method. 1: Rolled material, 2, 3: Rolling stand, 4: Filter device, 5: Reference torque arm calculation device,
6: Torque arm variation calculation device, 7: Tension calculation device, 8: Filter time constant changing device, 9: Filter switching device.

Claims (1)

[Claims] 1. In one rolling stand i, the forward tension of the rolling stand i is calculated based on its rolling torque, rolling force, and the forward tension in the previous rolling stand i-1 whose noise has been suppressed by a filter device. In the inter-stand tension detection method in continuous rolling, the noise removal time constant of the filter device is made small before the lock-on timing in rolling stand i, and the noise removal time constant is made large after the lock-on timing. Features: A method for detecting tension between stands in continuous rolling. 2. The inter-stand tension detection method in continuous rolling according to claim 2, wherein a plurality of filter devices have different time constants, and the noise removal time constant is changed by switching the filter devices.