JPS59183918A - Gage meter type automatic controlling method of plate thickness - Google Patents

Abstract

PURPOSE:To obtain satisfactory accuracy in the control of plate thickness while maintaining the stability of a gage meter type automatic controlling system for plate thickness by calculating momentarily the coefft. M of mill stiffness from the specific equation and determining successively the estimated value for controlling and calculating M in said system. CONSTITUTION:A coefft. M of mill stiffness is momentarily calculated by the equation M = dp/dh dp/ds = (dp/dt)/(ds/dt) from the time differential dp/dt of rolling load P and the time differential of a roll gap (s) with respect to the differential value by the outlet side plate thickness (h) of rolling load P, i.e., the change of the coefft. M with time. The estimated value Mc for controlling and calculating the M in the control system is successively determined in accodance with the calculated value of the M.

Description

Detailed Description of the Invention (Technical Field of the Invention) The present invention relates to a method for controlling plate thickness in rolling of steel plates, etc.
More specifically, the present invention relates to a gauge meter type automatic plate thickness control method.

(Technical profile of the invention and its problems) In general, the control system in the gauge meter type plate thickness control method is shown in Figure 1 using a line diagram. Based on Figure 1, the characteristic equation for is TI T2 T3 S' + (TI T2 +T2
T3 +T3 Tl ) S3+(TI +T2=0
(2) Here, 'L, T2, T3... Time setting S... Laplace variable G... Feedforward gain M... Mill stiffness coefficient Me... Calculation Mill constant (estimated value for control calculation of M) Q
...Plastic modulus KA of the rolled material...Represented as scale factor. Regarding this custom-made equation (2), when determining the stability of the control system using the Routh method, first of all, even if the time constants T+, T2, and T3 are reasonable values in terms of actual division, It is clear that even if we assume a case where the value changes considerably beyond the normal range, it cannot be a factor that influences the stability of the system.

Therefore, in reality, the necessary and sufficient condition for the plate thickness control system to be stable is as follows for the last coefficient in equation (2): By the way, if the mill stiffness coefficient, that is, the differential value M of the rolling load with respect to the mill elongation amount, and its estimated value Me for control calculation are almost equal, and it can be considered that M=Mc, then 1 M4 people - -One-button illusion=〉0 and then KU=1 (M+Q) Mc M+Q -M-th-Q) K A In the range of (4), the scale factor I (A exceeding 1 indicates stability of the control system. It is also possible from a gender perspective.

However, when we examine the relationship between rolling load and mill elongation, we find that when the rolls are not rotating, the mill constant M (the slope of the tangent to the curve) changes relatively smoothly, but when the rolls are not rotating, the mill constant M (the slope of the tangent to the curve) changes relatively smoothly. During rotation, as shown in FIG. 3, although it is approximately periodic, it changes extremely irregularly and locally extremely steeply. Figure 2 shows the relationship between the load and the elongation of the mill, that is, the elongation of the roll opening, when the rolls are brought into contact with each other while the rolls are stationary without rotating, and the amount of roll tightening is increased. The load is the result measured by a load cell. FIG. 3 shows the results of similar measurements with the roll rotating. When actually rolling a steel plate or the like, it is an essential condition to rotate the rolls, and the mill rigidity coefficient M changes greatly over time as shown in FIG. 3. However, in conventional automatic plate thickness control systems, when determining Me in control calculations, the above-mentioned realistic transition of the M value is not reflected at all, and Me is almost fixedly determined. However, in reality, no matter where the value of Me is set, as long as it is fixed, as mentioned above, the M value changes from moment to moment, so there are cases where M=MC is not true, and sometimes the value of M There are cases where the change is so extreme that it is completely unreasonable to consider it as M-Mc. In fact, if M also has a large value McJ:9, which is the estimated value for calculation on the control side, then 1--J history-≦0(M+Q)Mc, and the above stability condition formula (3) was no longer satisfied, and the plate thickness control system was therefore unstable.

Therefore, in order to avoid system instability, M
The value of e is the maximum value Mm that can be assumed among the changing values of M.
Settings are being made to correspond to ax. Although this method can ensure the stability of the system, it has the disadvantage that good plate thickness control accuracy cannot be obtained.

In addition, there is a method to ensure the stability of the system regardless of the mismatch between M and the estimated value Mc of M by setting the scale factor KA low, but the scale factor KA is
Setting ^ to a low value for the thickness is equivalent to making the control system work less efficiently, so the accuracy of plate thickness control could not be achieved.

As mentioned above, in the conventional automatic plate thickness control system, the estimated value MC for calculating the control a1i1 of the mill stiffness coefficient M is set as substantially constant in the control calculation, and is made to follow the actual change in the M value. Therefore, in order to ensure the stability of the system, the accuracy of plate thickness control had to be sacrificed. The failure stems from the fact that the momentary changes in the M value are not reflected in the determination of the Mc value, and that achieving stable and highly accurate sheet thickness control depends on the consistency of the M and Mc values. It was made based on knowledge,
An object of the present invention is to provide an automatic plate thickness control method that can set the scale factor to a substantially ideal value while maintaining the stability of the control system, and thus can obtain good plate thickness control accuracy. It is in.

(Summary of the invention) That is, the present invention provides a gauge meter type automatic plate thickness control system in which the differential value M of the rolling load p with respect to the exit side plate thickness is
The time derivative d p of the rolling load p corresponds to the temporal change in
/d t and the time differential of the roll gap S, calculate M moment by moment using the following formula: Estimated value Me for control calculation of M in the system
This method is characterized by sequentially determining .

Next, the present invention will be explained in more detail with reference to the drawings.

In the gauge meter type automatic plate thickness control system as shown in FIG. Based on this, the estimated value Me for control calculation of M is determined. That is, the time differential value dp/dt of the rolling load p and the time differential value ds/dt of the roll spacing S, which can be considered as the plate thickness, are measured moment by moment, and from the following equation, the actual value is calculated. Calculate M sequentially during rolling, and add M to the value of M.
The value of the estimated value Me for control calculation is sequentially followed and determined,
The embodiment of sheet thickness control using this Mc value will be described in more detail.As shown in FIG. 4, a load measuring means 2 such as a load cell is attached to a hydraulic cylinder 1 that controls the roll rolling position of the rolling mill. The rolling load p is taken into the controller side. on the other hand,
A roll interval measuring means 7 is provided between the loaf and crevice for measuring the interval S between the upper work roll 4 supported by the upper backup roll 3 and the lower work roll 6 supported by the lower backup roll 5. As the zero roll spacing measuring means 7 for measuring the roll spacing S, which can be substantially regarded as the sheet thickness on the exit side, an optical method such as using a laser beam is particularly effective. Load measuring means 2
The rolling load p and the roll spacing S, which are measured moment by moment by the roll spacing measuring means 7 and taken into the controller side, are differentiated by differentiating circuits 8 and 9, respectively, and the time differential value dp/dt of the rolling load p and the roll spacing S are Time differential value d of interval S
s/dt is output every moment. These differential values are then input to the divider 1 and 10, where they are divided to give d s/d -
M is obtained. Based on this M value, the Me setting device 11 sets p
The value of Mc is set sequentially. The controller side performs control calculations every moment based on this Mc value, and operates the hydraulic cylinder 1 accordingly to change the roll-down position of the roll and control so that the thickness of the sheet on the exit side remains constant.

By determining the value of Me as described above, plate thickness control is determined by the mill rigidity coefficient M, scale factor KAI, and plasticity coefficient Q, which is a parameter determined by the composition, temperature, etc. of the rolled material and represents its hardness. System stability conditions 11
〉1RA M+Q is applied to the rolling intermediate t4, and the stability of the plate thickness control system is ensured. Furthermore, since it can be assumed that M = Me, even if KA = 1 is set, the stability condition of equation (4) "Q/Q > I (A is satisfied 0. Therefore, the stability of the control system will be impaired. It is also possible to set the KAO value to its ideal value, KA = 1, without any problems, and it is possible to obtain extremely good plate thickness control accuracy.

Next, the effects of the present invention will be explained using Examples and Reference Examples.

In Fig. 3, the Mill constant M is 300 at the part where the slope of the chart is the greatest (for example, the part marked with a circle in the figure).
0 t/mm, but now the controller side uses the calculated mill constant Me = 500 t/mm, and assuming that the plastic at constant Q of the slab to be rolled is 1200 t/mm, the plate thickness control system can be obtained by substituting the values of M, Me, and Q into the equation indicating the stability limit. Therefore, the scale factor KA at the stability limit is calculated as follows. However, in actual rolling,
In order to further ensure the stability of the control system, KA was set to 055 for safety reasons.

As a result, the thickness control characteristics are as follows:
Only 5% could be controlled, and a plate thickness variation of 110μ remained.

On the other hand, when setting the calculated Mill constant Me using the method of the present invention, stability can be ensured even if a large value of ■(A) is used.
．． For the example set to 90 fd, plate thickness variation is 244μ
was able to be reduced to

[Brief explanation of drawings]

Figure 1 is a block diagram of the gauge meter automatic plate thickness control system, and Figure 2 is the load and roll tightening amount when the roll is not rotating (
FIG. 3 is a similar diagram during roll rotation, and FIG. 4 is a schematic diagram showing the method of setting the calculated mill constant in the present invention. 1.Hydraulic cylinder 2.Load measuring means 3.Upper bar, qua, blow roll 4.Upper work roll 5..Lower bar,
Kur, Brol 6. Lower work roll 7. Roll interval measuring means 8.9. Differentiator circuit 10. Divider
11...Me setting device patent applicant Yoshihisa Nagai, patent attorney representing Sumitomo Metal Industries Co., Ltd.

Claims (1)

[Claims] (1) In the gauge meter type automatic plate thickness control system, the differential value of the rolling load p with respect to the outlet plate thickness, that is,
Corresponding to the temporal change in the mill stiffness coefficient M, M is calculated moment by moment from the time differential d p/d t of the rolling load p and the time differential of the roll gap S using the following formula % formula % (1). An estimated value Mc for control calculation of M in the control system based on the calculated value of M.
A gauge meter type automatic plate thickness control method characterized by sequentially determining the thickness of the plate.