JPH0667522B2 - Automatic shape control method for rolling mill - Google Patents

Description

The present invention relates to an automatic shape control method for a rolling mill that automatically controls the shape of a rolled material.

<Prior Art> FIG. 4 is a block diagram of a four-high rolling mill that implements a conventional automatic shape control method. 1 is a rolling mill, 2 is a backup roll, 3 is a work roll, 4 is a roll bending device,
5 is a rolling down device, 6 is a rolled material, 7 is a shape detector, 8 is a shape calculation device, and 9a and 9b are controllers.

According to this rolling mill, the rolled material 6 detected by the shape detector 7
The first-order component A ₁ and the second-order component A ₂ are obtained by the shape calculation device 8 from the elongation distribution of the sheet width direction. The primary component A ₁ and the secondary component
As shown in the same figure, A ₂ represents the magnitude of asymmetrical elongation and symmetrical elongation, respectively, and as a method for obtaining these components A ₁ and A ₂ from the elongation rate distribution in the strip width direction, For example, a method using an orthogonal function as shown in Japanese Patent Application No. 60-97980 and a method using a power series as shown in JP-A-55-19401 are known.

Then, the controller 9a drives the pressure reducing device 5 so that the primary component A ₁ becomes the target value A ₁ ^* (normally A ₁ ^* = 0 is set). For example, when the elongation on the drive side is higher than the target value, the reduction on the drive side is released, and the work side is reduced to control A ₁ = A ₁ ^* . Further, the roll bending device 4 is driven by the controller 9b so that the secondary component A ₂ also has the target value A ₂ ^* (normally A ₂ ^* = 0 is set). For example, if the edge is slightly stretched with respect to the target value, the roll bending device 4 is driven in a direction of increasing the convex crown of the work roll 3 and controlled so that A ₂ = A ₂ ^* .

A PI controller is usually used as the controllers 9a and 9b, and the proportional gain and the integration time of the controllers 9a and 9b have been constant values in the past.

<Problems to be Solved by the Invention> The conventional automatic shape control device described above has the following problems.

FIG. 5 is a block diagram showing the control system of the secondary component A ₂ .
In the figure, 9b is a control system of a PI controller having a proportional gain Kp and an integration time Ti, and 4 is a control system of a roll bending device. The control system 4 of the roll bending device changes the shape (component) with respect to the command value F to the roll bending device.
A ₂ ), which represents the response, the dead time L due to the transfer delay from the rolling mill 1 to the shape detector 7, the constants K and S.
It consists of

Here, the distance between the rolling mill 1 and the shape detector 7 is usually 2
Since it is about 3 m, the dead time L is about 1.2 to 1.8 sec when the rolling speed is 100 mpm. In addition, the time constant T is determined from the responsiveness of the roll bending device 4, the shape detector 7, and the like.
Since it is about 0.5 sec, the control system shown in FIG. 5 is a system governing the dead time L when the rolling speed is low. In such a control system, the optimum values of the proportional gain Kp and the integral time Ti of the PI controller 9b when the dead time L is dominant vary depending on the dead time L (that is, the rolling speed). As an example, to get the minimum settling time without overshoot, Also, to get the minimum settling time with 20% overshoot, Etc. are known.

However, in the conventional automatic shape control method, since the proportional gain Kp and the integration time Ti are constant values regardless of the rolling speed, the values of Kp and Ti are the minimum rolling speed (in terms of stability of the control system). It is necessary to set the optimum value for the maximum dead time). Therefore, even if the rolling speed is high and the dead time is small, the response (settling time) is almost the same as that at low speed, so the settling length (rolling speed / stabilizing time) at high speed becomes long and high. There is a problem that accurate automatic shape control cannot be achieved. This situation also applies to the control of the first-order component A ₁ .

The present invention has been made in view of the above conventional circumstances, and an object of the present invention is to provide a method for achieving highly accurate automatic shape control regardless of changes in rolling speed.

<Means for Solving Problems> An automatic shape control method for a rolling mill according to the present invention automatically feeds back the shape of a rolled material by feeding back a detection signal of a shape detector installed separately on the downstream side of the rolling mill. A rolling mill for control is characterized by detecting a rolling speed and setting a proportional gain and an integration time of a control system according to the rolling speed.

<Operation> When the proportional gain and the integration time are set according to the rolling speed, the response time becomes shorter as the rolling speed becomes faster, and the optimum response can be obtained at each rolling speed.

<Example> An example in which the present invention is applied to a four-high rolling mill will be described with reference to the drawings.

FIG. 1 is a block diagram of a four-high rolling mill. Incidentally, the same parts as those of the conventional one are designated by the same reference numerals, and the duplicated description will be omitted. In FIG. 1, 11 is a speedometer, 12 is a speed correction calculation device, and the speed correction calculation device 12 calculates the proportional gain Kp and integration time of the controllers 9a and 9b from the rolling speed v detected by the speedometer 11 every moment. Ti is calculated every moment and set.

Here, assuming that the reference rolling speed is v ₀ , and the optimum values of the proportional gain and the integration time at the reference rolling speed v ₀ are Kp ₀ and Ti ₀ , respectively, the proportional gain Kp and the integration time Ti are calculated from the rolling speed v as follows. There are several ways to do this.

That is, , The rolling speed v or the square root of the rolling speed The proportional gain Kp is increased in proportion to the rolling speed v or the square root of the rolling speed. A method of reducing the integration time Ti in inverse proportion to. Further, as shown in FIG. 2, a method of obtaining by an approximate expression representing the relationship between the rolling speed v obtained by experiments, the optimum proportional gain Kp and the optimum integration time Ti. Also, instead of using the same approximate formula, a table is used.

As an example, the proportional gain is calculated by the equations (2) and (3).
FIG. 3 shows the response of the control system of the first-order component A ₁ when Kp and the integration time Ti are obtained. In Fig. 3, column a) shows the amplitude of 2 in the control system of the primary component A _{1 when} the rolling speed is v = 100 mpm.
This is the response when a step-like target value A ₁ ^* of × 10 ^-4 is input. As shown in the graph in the same column, the dead time is 1.5 seconds.
90% rise time is 7.5sec with (transfer distance is 2.5m)
Is. At this time, the constant of RI controller 9a is set to K _P0 , Ki
_{It was set to 0} . Then, in FIG. 3, columns b) and c) are the cases of rolling speed v = 200 mpm, v = 400 mpm, respectively.
The 90% rise times are as short as 4.2 seconds, 2 and 4 seconds, respectively, and it can be seen that there is an effect of correction by equations (2) and (3). Further, it is understood that the correction by the equation (1) is also effective by the equations (4) and (5) described above. Also,
It is clear that the corrections according to FIG. 2 also have their respective effects.

Although the above-mentioned embodiment applies the present invention to a four-high rolling mill, the present invention can of course be applied to other types of rolling mills.

<Advantages of the Invention> According to the present invention, in an automatic shape control system in which a dead time caused by a transfer delay between a rolling mill and a shape detector is dominant, a proportional gain and an integral time of a controller are set according to a rolling speed. Since it is set, the response time can be shortened as the rolling speed increases. Therefore,
Settling length with increasing rolling speed (rolling speed / settling time)
Can be suppressed, and highly accurate automatic shape control can be achieved.

[Brief description of drawings]

FIG. 1 is a block diagram of a four-high rolling mill to which the present invention is applied,
FIG. 4 is a characteristic diagram showing an optimum proportional gain and an optimum integration time with respect to a rolling speed, FIG. 3 is an explanatory view of the effect of the present invention, and FIG. FIG. 5 is a block diagram showing a conventional control system. In the drawings, 1 is a rolling mill, 6 is a rolled material, 7 is a shape detector, 11 is a speedometer, and 12 is a speed correction computing device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuhiro Abe 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries Ltd. Hiroshima Factory (72) Inventor Takayuki Kaji 1 Kawasaki-cho, Chiba-shi Chiba Prefecture Kawasaki Steelmaking Co., Ltd.Technical Research Headquarters (72) Inventor Takashi Misaki, 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd., Chiba Works (72) Inventor, Akihiko Fukuhara, 1 Kawasaki-machi, Chiba, Chiba In-house

Claims (1)

[Claims] 1. A rolling mill for automatically controlling the shape of a rolled material by feeding back a detection signal from a shape detector installed separately on the downstream side of the rolling mill, detects a rolling speed, and outputs a proportional gain of a control system. And an automatic shape control method for a rolling mill, wherein the integration time is set according to the rolling speed.