JPH0363443B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a monitoring automatic plate thickness control method for a rolling mill.

(Prior art) There are various automatic plate thickness control systems (AGC) for rolling mills. Among them, the monitor automatic plate thickness control system (monitor AGC) is a method for controlling the hardness unevenness of rolled materials.
Calculation processing to detect exit side plate thickness deviation in order to suppress variations in exit side plate thickness caused by thermal crowns, etc., and perform proportional action, integral action, or proportional + integral action using a PI controller, etc. based on this deviation. This method is known as a method in which the output is input to a reduction control device and fed back to control the plate thickness.

Specifically, as shown in FIG. 5, a thickness deviation ΔH on the exit side of the rolled material 3 is detected by a thickness gauge 2 installed on the exit side of the rolling mill 1, and is input to the PI controller 4. The PI controller 4 calculates the control amount roll gap ΔS using the following equation.

ΔS=k _p (ΔH+1/T _I ∫ΔHdt) Here, kp: proportionality constant T _I : integral time This ΔS is input to a reduction control device 5 such as a hydraulic reduction type, and is controlled by adjusting the roll gap of the rolling mill 1. Control plate thickness.

(Problem to be Solved by the Invention) However, in this monitor AGC, the thickness gauge 2, which is the signal detection end, is installed at the rear (output side) of the center of the rolling mill, which is the control amount control end. Since the correction operation starts after the thickness gauge 2 detects the thickness deviation on the exit side, the lower the rolling speed, the longer the detection delay time, that is, the dead time. In this respect, in the conventional method, it is not possible to obtain a large gain due to this wasted time, and the response of the monitor control system is therefore slow, especially when the acceleration up to the steady rolling speed or the threading speed from the steady rolling speed When decelerating up to 100 degrees, off-gauge parts occur at welding points and other areas where the thickness deviation on the exit side is large, resulting in a reduction in productivity.

The present invention solves the above-mentioned drawbacks of the conventional technology, reduces as much as possible off-gauge parts such as acceleration/deceleration parts of rolled materials and parts with large exit plate thickness deviations, and improves productivity by automatically monitoring rolling mills. The purpose of this invention is to provide a method for controlling plate thickness.

(Means for solving the problem) In order to achieve the above object, the inventor has developed a monitor
Considering that dead time in AGC is a factor that causes hunting in the control system, we conducted various studies on ways to compensate for this, and after introducing a dead time compensation model to find the amount of compensation, we applied this to the PI controller as a positive feed. The idea was that this would be possible by using a back-up system.

That is, the present invention detects the thickness deviation of the exit side of the rolled material, performs arithmetic processing to perform proportional operation, integral operation, etc. in the controller based on this, and inputs the output to the rolling control device for feedback. In the monitor automatic plate thickness control method for adjusting the roll gap, a dead time compensation model is created in advance from the monitor control system model, and the dead time is calculated by detecting the exit rolling speed of the rolling mill. and the output of the controller are input into the dead time compensation model to obtain a compensation amount, and this compensation amount is input to the controller as positive feedback. That is.

The present invention will be explained in detail below based on examples.

(Embodiment) FIG. 1 is a block diagram of the entire rolling mill system, and this system is composed of a negative feedback system and a positive feedback system incorporated therein.

In the conventional monitor AGC, first, the outlet side plate thickness deviation ΔH detected by the thickness gauge 2 installed on the outlet side of the rolling mill is compared with the outlet side plate thickness deviation set value ΔH ₀ in the comparator 6, and the result is sent to the PI controller 4. is input. Then, in the PI controller 4, calculations for proportional operation, integral operation, or proportional + integral operation are performed based on the above formula, and the output is input to the rolling reduction control device of the rolling mill 1 to adjust the roll gap.
Plate thickness control is performed, but a delay time occurs between detecting the plate thickness and adjusting the roll gap, which causes hunting in the system.

In contrast, in the method of the present invention, the essential part is to insert a positive feedback system for compensating for dead time using dead time compensation circuit 7 into the above system. In this positive feedback system, first, according to the flowchart illustrated in Fig. 2, the following formula x ₂ = 1-e ^-LS / kp (1 + 1 / T _I S) x ₁ ... is based on the dead time compensation model (described later). The compensation amount x ₂ is calculated by... In other words, the data required to calculate the compensation _amount
and reading of the integration time T _I is executed. Further, in step, the output value _x1 of the PI controller is read, and in step, the exit rolling speed v(t) detected by a sensor installed on the exit side of the rolling mill is read. In the step, data l, v(t)
Then, the dead time L(t) is calculated by the following formula L(t)=l/v(t), and in step, the data L, kp,
The compensation amount x ₂ is calculated from T _I and x ₁ using the above equation (1).
In the step, the amount of compensation calculated in the step
x ₂ is output to the input of the PI controller. In addition,
The step is a judge of whether to continue the operation; if YES, the operation continues from the step; if NO, the operation is stopped, that is, it ends.

The dead time compensation model H(s) used in the above calculation is derived as follows based on FIG. In other words, the input is the disturbance R(s), the output is the thickness deviation Y(s) directly under the roll, and R(s), Y(s)
Assuming that the transfer function is G(s), G(s) is obtained to obtain the following equation.

G(s)=Y(s)/R(s)=1+G ₁
(s)H(s)/1+G ₁ (s)H(s)+G ₁ (s)G ₂ (
s)G ₃ (s)e ^-LS ... On the other hand, the transfer function G(s) of a system without dead time is given by the following equation with H(s) = 0 and e ^-LS = 1 in Fig. 1.

G (s) = 1/1 + G ₁ (s) G ₂ (s) G ₃ (s) ... Therefore, the formula = formula, 1 + G ₁ (s) H (s) / 1 + G ₁ (s) H (s )+G ₁
(s) G ₂ (s) G ₃ (s) e ^-LS = 1/1 + G ₁ (s) G ₂ (s
)G ₃ (s)... Solving the equation for H(s), we get H(s)=e ^-LS -1/G ₁ (s)... and this equation has G ₁ (s)=kp(1+1 /T _I S), H(s) is obtained as follows.

H(s)=e ^-LS -1/kp(1+1/T _I S)... Negative feedback system including a positive feedback system that outputs the compensation amount x ₂ obtained as above to the input of the PI controller works as follows.

That is, the plate thickness deviation value ΔH ₀ is set to ΔH ₀ =0 because the goal is for the deviation to be zero. This ΔH ₀ is compared with the outlet side plate thickness deviation value ΔH detected by the thickness gauge 2 in a subtracter 6, and the result is added to the compensation amount x ₂ , which is the output of the dead time compensation circuit 7, in an adder 8. and input to the PI controller 4. The PI controller 4 performs arithmetic processing in the same way as the conventional method, but takes into account the compensation amount x ₂ , and uses the output to adjust the roll gap through the reduction suppression device to suppress the plate thickness. Even if there is a dead time of L seconds between the time of detection by the thickness gauge 2 and the time of roll gap adjustment, hunting in the system is prevented since the compensation amount _x2 is taken into account.

Incidentally _, Figures 3 and 4 show an example of the results of a simulation conducted to confirm the effect of dead time compensation _. ), set the respective constants of G ₂ (s), G ₃ (s), and e ^-LS appropriately, and examine the response of the plate thickness deviation Y (s) using the disturbance R (s) as a step input. This is the result. Note that the step input has a magnitude of 1 at time 0.

FIG. 3 shows the results of dead time compensation according to the present invention, and it can be seen that the plate thickness converges to the target value more quickly than in the conventional method without compensation shown in FIG.

In addition, although the above description has been made regarding the case where the controller is a PI controller, it goes without saying that the present invention can also be applied to a PID controller or a PD controller as in the past.

(Effects of the Invention) As described in detail above, according to the present invention, the wasted time associated with the detection of the outlet side thickness deviation in monitor automatic thickness control is compensated for using the dead time compensation model. Hunting of the system can be prevented, and the gain can therefore be further increased, allowing a high-speed monitor control system to be configured, improving followability in the acceleration/deceleration section, and reducing the deviation of the exit side plate thickness. Convergence at that part becomes faster, making it possible to significantly reduce off-gauge parts.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the entire rolling mill system according to the present invention, Fig. 2 is an example of a flowchart for calculating the amount of compensation for dead time, and Figs. FIG. 3 shows the case of the present invention, FIG. 4 shows the case of the conventional method, and FIG. 5 is an explanatory diagram showing the monitor automatic plate thickness control system of the rolling mill. 1...Rolling machine, 2...Thickness gauge, 3...Rolled material,
4...PI controller, 5...pressure control device,
7...Dead time compensation circuit.

Claims (1)

[Claims] 1. Detect the thickness deviation of the rolled material on the exit side, and based on this, the controller performs arithmetic processing to perform proportional action, integral action, etc., and inputs the output to the rolling control device for feedback and adjusts the roll gap. In the monitor automatic plate thickness control method, a dead time compensation model is created in advance from the monitor control system model, and the dead time is determined by detecting the rolling speed on the exit side of the rolling mill, and the dead time and the output of the controller are calculated. A monitoring automatic plate thickness control method for a rolling mill, characterized in that the amount of compensation is obtained by inputting the amount of compensation into the dead time compensation model, and the amount of compensation is inputted to the controller as positive feedback.