JPH0815608B2 - Plate thickness control method for steel strip rolling mill - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a plate thickness control method in a steel strip rolling mill, and more specifically, in rolling a steel strip using a rolling mill, a plate thickness sent from a plate thickness gauge for measuring the thickness of the steel strip. The present invention relates to a plate thickness control method for operating a reduction device based on a deviation signal to control the thickness of the steel strip by feedback.

[Prior art]

Conventionally, strip thickness control in a steel strip rolling mill has been performed by the method shown in FIG. That is, in FIG. 7, the thickness of the steel strip 10 is measured by the strip thickness gauge 12 installed on the outlet side of the steel strip 10 and the strip thickness deviation signal Δh sent from the strip thickness gauge 12 is measured.
Based on the proportional / integral control circuit 14, proportional / integral control is performed, and the commanding device ΔS sent from the control circuit 14 operates the reduction device 16 to change the positions of the rolling rolls 18a, 18b.
Ultimately, the strip thickness of the steel strip 10 was controlled by feedback. However, in the conventional example as shown in FIG. 7, there is a certain distance from immediately below the rolling roll 18c (that is, the neutral point where the rolling rolls 18b and 18c press the steel strip 10) to the plate thickness gauge 12. During that time, the steel strip transfer time was wasted. Further, since there is such a dead time, it takes a certain time from the start of the proportional / integral control until the steel strip 10 reaches the target plate thickness, and the steel strip 10 rolled during this time There was a problem that the thickness of the plate became an off gauge (out of plate thickness). However, the above-described adverse effect on the response of the control system on the up and down dead time was remarkable especially when the steel strip 10 was rolled at a low speed. On the other hand, in order to avoid the influence of the dead time on the control system and improve the responsiveness of the control system, control by the Smith compensation method as shown in Fig. 8 has also been attempted (OJMSmit
h: A Controller to Overcome Dead Time, ISA J., 6−2,2
See 8/33 (1959)). That is, the gain of control by the Smith compensation method is C, the tuning rate of BISRA-AGC (automatic thickness control) is α, the mill constant is M, the plastic constant of the rolled material (steel strip 10) is Q, and the rolling rolls 18b and 18c. The steel strip transfer time between the plate thickness gauges 12 is T _L , the gain of proportional control is K _P , the gain of integral control is
When K _I , T is the first-order lag time constant of the proportional term, P is the rolling load detected by the load cell 20, P ₀ is the rolling load setting value, and S ₀ is the gear setting value between the rolling rolls 18b and 18c. The configuration of the control by the Smith compensation method is as shown in FIG. The thickness is controlled in real time by making a certain correction in consideration. However, the control by the Smith compensation method has the following problems. That is, first, the mill constant M used in the Smith compensation method can be measured, but the plastic constant Q of the rolled material cannot be measured during rolling although it varies depending on the material. , I have no choice but to use the estimated value. However, if this estimated value does not always match the actual value of the plasticity constant Q and there is a difference between them (that is, an error in the plasticity constant Q), an error in the control by the Smith compensation method is caused, and the proportional / integral control is performed. However, there is a problem in that the plate thickness accuracy has a larger error than in the case of. Secondly, the steel strip transfer time T _L from immediately below the rolling rolls 18b and 18c to the plate thickness gauge 12 in FIG. 8 is obtained from the following equation (1). Unless the actual measurement is made, it is impossible to actually measure the advanced rate f, and the estimated value must be used. T _L = L / V (1 + f) (1) Here, L is the distance between the rolling rolls 18b and 18c and the plate thickness gauge 12, V is the peripheral speed of the rolling roll, and f is the advance rate. However, when the rolling speed changes, the friction coefficient between the steel strip 10 and the rolling rolls 18b and 18c changes, and the advance rate f changes accordingly. Therefore, the estimated value of the advanced rate f does not always match the actual value, and the difference between them (ie, the advanced rate f
There is also a problem that the error) directly causes a control error.

[Problems to be achieved by the invention]

The present invention has been made in view of the problems of the conventional example, and its object is to provide a plate having a fast response and stable plate thickness control when rolling a steel strip using a rolling mill. It is to provide a thickness control method.

[Means for Solving the Problems]

The present invention, when rolling a steel strip using a rolling mill, operates a reduction device based on a strip thickness deviation signal sent from a strip thickness gauge for measuring the thickness of the strip to adjust the thickness of the strip. In the plate thickness control method of controlling the feed back, when the plate thickness deviation exceeds a preset upper and lower limit value, the control by the Smith compensation method is performed, and when the plate thickness deviation is between the upper limit value and the lower limit value. Solves the above problem by performing proportional / integral control.

[Action]

The present invention sets the upper and lower limit values of the plate thickness deviation in rolling the steel strip in advance, and when the plate thickness deviation is a value larger than the upper limit value or a value smaller than the lower limit value, the Smith compensation method The plate thickness is corrected early within the upper and lower limits, and when the thickness deviation is within the upper and lower limits, proportional and integral control is performed to control the plate thickness. Is a stable control. That is, in the strip thickness control method in the steel strip rolling mill,
Focusing on the fact that the control by the Smith compensation method has a faster response than the proportional / integral control, if the sheet thickness deviation of the steel strip detected by the thickness gauge exceeds the preset upper and lower limits, Smith compensation is performed. If the plate thickness deviation is within the upper and lower limit values, proportional / integral control is performed to quickly and stably control the plate thickness.

【Example】

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration explanatory view for explaining an embodiment of the present invention. In this figure, a proportional / integral control circuit is included in a plate thickness control device (not shown in the drawing) such as a DDC (Direct Digital Control), which includes a plate thickness gauge 12 as a sensor.
14 and a Smith compensation method control circuit 20 are provided in parallel, and a determination circuit 22 that determines the thickness deviation by receiving the thickness deviation signal Δh sent from the thickness gauge 12 is provided. One of the switch circuits 24a and 24b is turned on by the output of the judgment circuit 22, and the output ΔS of the proportional / integral control circuit 14 or the Smith compensation method control circuit 20 is sent to the reduction device 16. ing. 2 and 3 are a logic circuit diagram showing the logic of the decision circuit 22 and an operation explanatory diagram thereof. In this figure, when the value of the thickness deviation Δh sent from the thickness gauge 12 in FIG. 1 is a value between the upper limit value Δh _U 1 and the lower limit value Δh _L 1 which are set in advance. Is caused by the plate thickness deviation Δh, the logic signal input to one of the AND circuits 100 (upper part of the figure) becomes high level, and the AND circuit 10 described later
The output of 6 is ANDed with the inverted signal, and then sent to the circuit 108 for performing proportional / integral control (more specifically, the switch circuit 24a in FIG. 1) to perform the proportional / integral control. Let me do it. Here, the logical product of the output of the AND circuit 106 and the negation of the output for performing the control by the Smith compensation method is taken as shown in FIG.
Even if h is a value between the upper limit value Δh _U 1 and the lower limit value Δh _L 1, if control by the Smith compensation method is being executed, this is prioritized to have hysteresis and control is switched. This is because it is prevented from being performed too frequently. On the other hand, when the value of the plate thickness deviation Δh is larger than the upper limit value Δh _U 1 or smaller than the lower limit value Δh _L 1, the plate thickness deviation Δh , One of the logical signals input to the logical sum circuit 102 becomes high level, the output of the logical sum circuit 102 is input to the logical circuit 104, and the output of the logical product circuit 106 to be described later is inverted. The logical sum operation is performed between. As a result, when the plate thickness deviation Δh is larger than the upper limit value Δh _U 1 or smaller than the lower limit value Δh _L 1, the Smith compensation method is used regardless of whether proportional / integral control is being executed. Switching to control is performed. Further, when the value of the plate thickness deviation Δh is a value between the upper limit value h _U 2 and the lower limit value h _L 2, it is inverted to one of the AND circuits 106 (downward in the figure) due to the plate thickness deviation Δh. The input logic signal becomes low level, and the logical product operation is performed with the output of the OR circuit 104. The output of the logical product circuit 106 is input to the logical sum circuit 104 and inverted to the logical product circuit 100, and is a circuit for performing control by the Smith compensation method.
110 (more specifically, the switch circuit 24b in FIG. 1) is sent to control by the Smith compensation method. That is, the determination circuit 22 of FIG. 1 described in detail with reference to FIG.
Causes the proportional / integral control circuit 108 to perform proportional / integral control at the start of control, and the plate thickness deviation Δh of the steel strip 10 is the upper limit value Δh _U.
When the value is larger than 1 or smaller than the lower limit value Δh _L 1, the Smith compensation method control circuit 110 is switched to perform Smith compensation method control. Further, when the plate thickness deviation Δh of the steel strip 10 falls between the upper limit value Δh _U 2 and the lower limit value Δh _L 2 by such Smith compensation method control, the proportional / integral control circuit 108 again.
To switch to proportional / integral control. In the embodiment as described above, when step-like disturbance is applied to the plate thickness deviation Δh sent from the plate thickness gauge 12 of FIG. 1, the step counter answer of the proportional / integral control by the proportional / integral control circuit 14 is For example, as shown in FIG. 4, the step response of Smith compensation method control by the Smith compensation method control circuit 20 becomes as shown in FIG. 5, for example. As is clear from the comparison between FIGS. 4 and 5, it can be seen that the control by the Smith compensation method has a faster response than the proportional / integral control. Therefore, as in the present embodiment, the plate thickness deviation Δh of the steel strip 10 is the upper limit value Δh _U 2
When the value is larger than (Δh _U 1) (or smaller than the lower limit value Δh _L 2 (Δh _L 1)), proportional
It can be seen that when the integral control is switched to the Smith compensation method control, the responsiveness is improved as compared with the case of the proportional / integral control alone, and as shown in FIG. 6, the responsiveness of the control is fast and stable throughout. .

【The invention's effect】

According to the present invention as described in detail above, upper and lower limit values are set in advance for the plate thickness deviation, and when the measured plate thickness deviation falls outside the range of the upper and lower limit values, control by the Smith compensation method is performed. The thickness of the rolling mill is corrected promptly, and when the thickness deviation falls within the upper and lower limits, proportional and integral control is performed to perform stable thickness control. When the steel strip is rolled by using, the plate thickness can be controlled quickly and stably. By the way, when the present invention was applied to the first stand of the complete continuous cold tandem rolling mill, it was possible to achieve an early on-gauge after changing the running plate thickness, and to achieve an off-gauge reduction of about Δ5 m / coil. . Further, when the present invention is applied to the first stand of a batch type cold tandem rolling mill, it is possible to achieve an off gauge reduction of about Δ13 m / coil by preventing the occurrence of off gauge in the low speed rolling section at the coil front and rear ends. I was able to.

[Brief description of drawings]

FIG. 1 is a configuration explanatory view for explaining an embodiment of the present invention, and FIG. 2 is a logic circuit diagram showing a logic of a judging circuit for judging a plate thickness deviation signal sent from a plate thickness gauge, and FIG. FIG. 4 is a diagram for explaining the operation of the judgment circuit, FIG. 4 is a diagram showing an example of step response of conventional proportional / integral control, and FIG. 5 is a line showing an example of step response of control by the Smith compensation method. FIG. 6 is a diagram showing an example of step response of plate thickness control according to the embodiment of the present invention, FIG. 7 is a configuration explanatory view for explaining a conventional example of plate thickness control, and FIG. FIG. 6 is a configuration explanatory view for explaining control by the Smith compensation method. 10 ... Steel strip, 12 ... Plate thickness gauge, 14 ... Proportional / integral control circuit, 16 ...
Rolling down device, 18a to 18d ... Rolling roll, 20 ... Smith compensation method control circuit, 22 ... Judgment circuit, 24a, 24b ... Switch circuit.

Claims (1)

[Claims] 1. When rolling a steel strip using a rolling mill, the reduction device is operated based on a strip thickness deviation signal sent from a strip thickness gauge for measuring the thickness of the strip, and the thickness of the strip is controlled. In the plate thickness control method for controlling the feed back, when the plate thickness deviation exceeds a preset upper and lower limit value, control is performed by a Smith compensation method, and the plate thickness deviation is between the upper limit value and the lower limit value. A plate thickness control method in a steel strip rolling machine characterized by performing proportional / integral control at times.