JPH0722769B2 - Automatic gain adjustment method for plate thickness controller - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to an automatic gain adjusting method for a plate thickness control device in a rolling mill that enables highly accurate plate thickness control.

[Prior art]

Conventionally, as one of the common plate thickness control methods, Bisura (BISR
A) There is an AGC (Automatic Gauge Control) system.
Fig. 5 shows the Mill constant M [t
is a diagram showing the relationship among rolling load P [ton], rolling position S [mm], inlet side plate thickness H [mm], and outlet side plate thickness ho [mm] in an on / mm] rolling mill. In the above-mentioned Visla AGC, as shown in FIG. 5, for example, when the material (deformation resistance) of the material to be rolled on the rolling mill entrance side changes and the strip thickness on the rolling mill exit side changes, the exit side sheet thickness ho
Is given by the following equation (1). ho = S + P / M (1) Considering the difference of the basic formula (1) of the mill, the following formula (2)
Is obtained. Δho = ΔS + ΔP / M (2) In the above-mentioned Bisler AGC, the reduction system is controlled so that the output side plate thickness variation Δho = O expressed by the above equation (2). That is, the rolling load fluctuation ΔP is detected and the rolling position fluctuation ΔS is controlled so that the following expression (3) is established. Where k
Is the gain. ΔS = −k · ΔP / M (3) The control by the above formula (3) is, for example, because the deformation resistance of the material to be rolled (material) on the entrance side of the rolling mill becomes large,
If the plate thickness of the rolled material on the exit side increases,
The rolling position is tightened based on the rolling load variation ΔP increased accordingly, and the goal is to set the delivery side plate thickness variation Δho = O. Therefore, for the change of the rolling load P that can be sufficiently responded to by the control of the above formula (3), the apparent mill constant Me represented by the following formula (4) becomes extremely large, and this apparent mill constant Me becomes extremely large. The Mill constant Me can be used as the equivalent Mill constant. Me = M / (1-k) (4) On the other hand, in the above control method, if an eccentric component exists in the backup roll of the rolling mill, the rolling position fluctuation ΔS _B is always generated every time the backup roll makes one revolution. Although it occurs, the rolling load fluctuation ΔP _{B at} that time is a sufficiently slow fluctuation and can be expressed by the following equation (5). ΔP _B = Me · ΔS _B (5) Substituting the above equation (5) into the above equation (3), and substituting the above equation (4) into the result, the following equation (6) is obtained. To be ΔS = −k · ΔP _B / M = −k · M · ΔS _B / M = −k · ΔS _B / (1-k) (6) Therefore, from the above formula (6), the backup roll is eccentric. If it exists, it is understood that when the gain k of the plate thickness control device is increased, a large disturbance is generated in control. Therefore, in contrast to this, conventionally, the eccentric amount of the backup roll is measured online or offline, and the rolling position fluctuation ΔS _B is input in the antiphase to the rolling device, and the rolling load caused by the eccentricity of the backup roll is measured. Variation ΔP _B is almost 0
The method was taken.

[Problems to be Solved by the Invention]

However, the accuracy of correction for the eccentricity of the backup roll is insufficient, and it has become clear from recent research that the eccentricity of the intermediate roll and work roll is also a disturbance for the above-mentioned plate thickness control. It was In other words, the eccentric components of the backup roll, the intermediate roll, and the work roll are present, so that there is a situation in which the gain of Visla AGC cannot be increased. In this way, when there is a slight eccentricity of the backup roll that cannot be completely corrected by the conventional correction of the eccentricity of the backup roll, a work roll, and an eccentricity of the intermediate roll, the gain of the Bisla AGC is simply changed. There is a problem in that a good plate thickness accuracy cannot be obtained because the eccentricity amount of each roll becomes a disturbance only by increasing it. Further, if the gain of the Bisler AGC is made too small in order to reduce the disturbance due to the eccentricity of each roll, it is impossible to prevent the variation in the thickness on the outlet side due to the variation in the thickness of the material on the inlet side and the hardness. There was a problem. The present invention has been made to solve the above problems,
Optimal Bisler AGC that always enables highly accurate thickness control
It is an object of the present invention to provide an automatic gain adjusting method for a plate thickness control device capable of obtaining the above gain.

[Means for achieving the object]

The present invention detects a load fluctuation of a rolling mill and sets a feedback gain of a plate thickness control device that feedback-controls a rolling position so that a plate thickness fluctuation on the delivery side of the rolling mill obtained from the load fluctuation is zero. In doing so, frequency analysis the output of the plate thickness gauge located on the rolling mill output side, to determine whether the main factor of the plate thickness variation from the unfolding result is roll eccentricity or rolled material, these The above-mentioned object is achieved by setting the gain of the feedback so that the influences of the two on the plate thickness variation are substantially equal.

[Action and effect]

In the present invention, frequency analysis of the output of the strip thickness gauge on the delivery side of the rolling mill determines the main factor of the strip thickness variation at that time, and the variation of the material of the rolled material (mother plate) on the entry side and , The influence on the output side plate thickness variation due to the sheet thickness variation and the influence on the output side sheet thickness variation due to the disturbance caused by the eccentricity of the rolling mill roll such as the backup roll, the intermediate roll, and the work roll are always the same. By doing so, the optimum Bisler AGC gain (feedback gain) is automatically adjusted. This will be described in detail with reference to a specific example. For example, when rolling a material having a large variation in hardness of the mother plate, a frequency analysis of variation in the outgoing plate thickness is performed, and from the results shown in FIG. The machine recognizes that the gauge variation due to frequency components such as hardness variation of the mother plate is larger than the thickness variation component due to the intermediate roll and the work roll, and the component due to the hardness variation of the mother plate and the rolling mill By increasing the gain k of the Bisla AGC until the eccentricity component of any one of the rolls is substantially the same,
Allows optimum gain adjustment of Bisla AGC. Further, for example, when rolling in a state where the eccentricity of the intermediate roll is large, as shown by the frequency analysis result of the output side plate thickness variation in FIG. 2, the rotation frequency component of the intermediate roll is the main factor of the plate thickness variation. However, this is automatically recognized by the computer, until the plate thickness fluctuation component of any one of the intermediate roll, the work roll and the backup roll and the frequency component due to other hardness fluctuations have substantially the same strength, The gain k of the Bisla AGC is reduced. This makes it possible to automatically adjust the optimum gain of the Bisla AGC while the intermediate roll is being used. The frequency analysis is generally performed by performing a fast Fourier analysis (FFT) on the variation of the outgoing plate thickness. Further, since the diameters of the rolling rolls such as the backup roll, the intermediate roll, and the work roll are known, the frequency of each roll can be calculated from the roll diameter and the rolling speed. If the spectrum intensity has a maximum value at a frequency other than the frequency of the rolling roll, these factors are due to factors other than the rolling roll, such as hardness variation of the material to be rolled. As described above, according to the present invention, frequency analysis is performed on the output signal of the strip thickness gauge on the delivery side of the rolling mill, so that the optimum Bisler AGC is always obtained.
Since the gain of can be set automatically, it depends on whether the main factor of the plate thickness fluctuation on the delivery side of the rolling mill is the rolled material (base material) or roll eccentricity, that is, the hardness of the base material. Which of the magnitude of fluctuation, the magnitude of thickness fluctuation of the base material, or the eccentricity of each of the backup roll, work roll, and intermediate roll mounted on the rolling mill is the main factor of the thickness fluctuation? Therefore, the most accurate plate thickness control becomes possible.

【Example】

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 3 is a schematic configuration diagram showing a rolling mill applied to one embodiment of the present invention. The rolling mill includes a pair of work rolls 10 and 10 arranged to face each other for rolling the material S to be rolled, and a pair of backup rolls 12 and 12 adjacent to the upper and lower positions of the work rolls 10 and 10, respectively. It is a rolling mill equipped with a four-high roll stand. A lowering device 14 for adjusting the roll lowering position is installed below the backup roll 12 located in the lower stage, and a screwing device for outputting a lowering signal is output to the lowering device 14.
AGC computer 16 is connected. On the exit side of the rolling mill, an X-ray plate thickness gauge 18 for measuring the plate thickness of the rolled material S after rolling which runs in the direction of the arrow 18
The X-ray plate thickness gauge 18 is
The frequency analysis computer 20 continues to perform the frequency analysis of the input signal from the device to calculate the gain of the Bisla AGC and output the result to the Bisla AGC computer 16 to set the gain.
The X-ray plate thickness gauge 18 has a pair of measuring units 18A, 18A arranged above and below the material to be rolled. Next, the operation of this embodiment will be described. First, in the rolling mill, at a constant rolling speed,
The sheet thickness of the rolled material S after rolling is measured by the X-ray sheet thickness gauge 18, and at the same time, the output signal of the sheet thickness gauge 18 at that time is input to the frequency analysis computer 20. Frequency analysis of the output signal of the plate thickness gauge 18 is performed. As a result of this frequency analysis, the rotation frequency component strength (g _B ) caused by the eccentricity of the backup roll 12 or the work roll
When 10 (g _W ) due to eccentricity is larger than other frequency component strength (g m) due to hardness variation of the material S to be rolled, that is, g _B > gm or g _W > gm (1 ), The Bisla AGC in the rolling mill is satisfied.
To reduce the gain k of. Conversely, during the above-described components strength, gm> g _B or gm> g _W ... (2) when the relationship is established, increasing the gain k of the Vistula AGC. Rotational frequency component strength (g _B , g _W ) due to eccentricity of backup roll 12 and work roll 10 and the material to be rolled (material)
From the comparison of the magnitude with the other frequency component intensity (gm) due to the physical properties of the above, by repeating the operation of increasing or decreasing the gain k as described above, the maximum value of each component intensity is substantially equal, that is, The relation of the following formula (3) is always established. MAX (g _B , g _W ) ≈MAX (gm) (3) By setting the gain so that the above (3) is always satisfied, it is possible to obtain the optimum gain k of the Bisla AGC in the rolling condition at that time. It will be possible. FIG. 4 is a flow chart summarizing the operation of this embodiment described above. Frequency analysis is performed on the plate thickness signal output from the plate thickness meter 18 (step 100). As a result of the above analysis, backup roll 12, work roll
When the maximum values of the rotational frequency component strengths (g _B , g _W ) due to the eccentricity of 10 are approximately equal to the maximum values of the other frequency component strengths (gm), that is, when the following equation (4) is satisfied, , The gain at that time is set as the gain k of the Bisla AGC (step 10
2). MAX (gm) −Δg ≦ MAX (g _B , g _W ) ≦ MAX (gm) + Δg Δg: Allowable amount (4) If the above expression (4) does not hold, the following (5) holds in step 104. It is determined whether to do. MAX (g _B , g _W )> MAX (gm) + Δg (5) When the relationship of the above equation (5) is established, the gain is reduced and the gain k of the Bisler AGC is set to k−Δk (step 106). On the other hand, if the above equation (5) is also not satisfied, the gain is increased and set as k = k + Δk (step
108). According to this embodiment described in detail above, the strip thickness gauge 18 on the delivery side of the rolling mill is
Since the optimum Visla AGC gain can always be automatically set by frequency analysis of the output signal of, the magnitude of the hardness variation of the base material (rolled material), the magnitude of the plate thickness variation of the base material, or Depending on which of the backup roll of the rolling mill and the eccentricity of the work roll is the main factor of the strip thickness variation on the exit side, the strip thickness can be controlled most accurately under each rolling condition. Although the present invention has been specifically described above, it is needless to say that the present invention is not limited to the above-mentioned embodiments. For example, the rolling mill applicable to the present invention is not limited to the four-high rolling mill shown in the embodiment, and may be a six-high rolling mill having an intermediate roll.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a frequency analysis result of the outlet side plate thickness variation, FIG. 2 is a diagram showing another example of a frequency analysis result of the outlet side plate thickness variation, and FIG. 3 is a diagram showing the present invention. FIG. 4 is a schematic configuration diagram showing a rolling mill applied to one embodiment, FIG. 4 is a flow chart for explaining the operation of the above embodiment, and FIG. 5 is a diagram for explaining characteristics of the rolling mill. 10 ... Work roll, 12 ... Backup roll, 14 ...
… Reduction device, 16 …… Visla AGC calculator, 18 …… X-ray plate thickness gauge, 20… Frequency analysis calculator, S… Rolled material.

Claims (1)

[Claims] 1. A feedback gain of a strip thickness control device for detecting a load variation of a rolling mill and performing feedback control of a reduction position so that a strip thickness variation on the delivery side of the rolling mill obtained from the load variation is zero. When setting, frequency analysis the output of the plate thickness gauge located on the rolling mill exit side, to determine whether the main factor of the plate thickness variation is the roll eccentricity or the material to be rolled from the analysis result, these An automatic gain adjusting method for a plate thickness control device, characterized in that the feedback gain is set so that the two influences on the plate thickness variation are substantially equal.