Method for controlling the thickness of a rolling mill

Abstract

To provide a plate thickness control method for a rolling mill capable of improving plate thickness accuracy.SOLUTION: A plate thickness control method for a rolling mill controls a rolling device 8 which presses down pressure rolls 21 so that a gap between the pressure rolls 21 becomes a pressure roll gap calculated on the basis of a thickness deviation on an inlet side, and corrects timing at which the rolling device 8 is controlled on the basis of a control delay time calculated from the thickness deviation on the inlet side. The method includes: decomposing the thickness deviation on the inlet side into a plurality of frequency components; calculating a delay time to be a control delay time for each frequency component; calculating amplitude of a thickness deviation on an outlet side of a rolled material W generated when the delay time is compensated by a compensation time for every frequency component; changing a compensation time and setting the compensation time when a total sum of absolute values of the amplitude becomes minimum as an optimum compensation time; and compensating the control delay time with the optimum compensation time.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present invention relates to a method for controlling the plate thickness of a rolling mill.

Background Art

[0002] Patent Document 1 discloses a method for controlling the plate thickness of a rolling mill that calculates the roll gap ΔS of a work roll for rolling a rolled material and outputs a command signal corresponding to the calculated roll gap ΔS to a rolling reduction device to control the plate thickness of the rolled material. In Patent Document 1, the deviation of the plate thickness on the inlet side of the rolled material (inlet side plate thickness deviation) is decomposed into frequency components, the overall delay time is calculated based on the delay time obtained for each frequency, and the timing of the command signal output to the rolling reduction device is corrected based on the calculated overall delay time.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the plate thickness control method of Patent Document 1, the overall delay time is constant, and inevitably, an outlet side plate thickness deviation (deviation of the plate thickness on the outlet side of the rolled material) remains. It is desirable to reduce the remaining outlet side plate thickness deviation and improve the plate thickness accuracy.

[0005] An object of the present invention is to provide a method for controlling the plate thickness of a rolling mill that can improve the plate thickness accuracy.

Means for Solving the Problems

[0006] The present invention detects the inlet side plate thickness deviation of a material to be rolled that is rolled by a pair of rolling rolls of a rolling mill, and controls a rolling reduction device that presses down the rolling rolls so that the gap between the rolling rolls becomes the roll gap calculated based on the inlet side plate thickness deviation.system In a method for controlling the thickness of a rolling mill, which corrects the timing of controlling the reduction device based on the delay time, the input thickness deviation is decomposed into multiple frequency components, and each of the frequency components The delay time is calculated, and the sum of the calculated delay times is the control delay time. Calculate, To determine the optimal compensation time for compensating the control delay time so that the amplitude of the phase lag or the deviation of the thickness deviation on the exit side of the rolled material is reduced, the following steps are performed for each frequency component. The aforementioned delay time The sum of any of the above is less than 1 or greater Compensation time We will tentatively set the delay time for each compensation time. This occurs when compensation is paid. Before Amplitude of the exit thickness deviation of the rolled material before Calculated for each frequency component, The calculated frequency components Sum of the absolute values ​​of the amplitudes Calculate the sum The compensation time that minimizes the control delay is set as the optimal compensation time, and the control delay time is compensated with the optimal compensation time. Furthermore, the timing for controlling the reduction device is corrected based on the control delay time compensated by the optimal compensation time. It is characterized by the following. [Effects of the Invention]

[0007] According to the present invention, the amplitude of the exit thickness deviation of the rolled material, which occurs when the control delay time for each frequency component is compensated by the compensation time, is calculated for each frequency component. The compensation time is then changed, and the compensation time at which the sum of the absolute values ​​of the exit thickness deviation amplitudes is minimized is set as the optimal compensation time. The control delay time is then compensated by the optimal compensation time. As a result, the timing of controlling the rolling device is corrected based on the control delay time compensated by the optimal compensation time. By compensating the control delay time with the optimal compensation time, the amplitude of the exit thickness deviation can be minimized. As a result, the exit thickness deviation can be minimized, and thus the thickness accuracy can be improved. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram of the rolling mill equipment. [Figure 2] This is a phase diagram showing the relationship between multiple frequency components obtained by decomposing the input plate thickness deviation and the phase lag. [Figure 3] This figure shows the change in the amplitude of the exit plate thickness deviation when there is no phase lag in controlling the rolling roll gap in response to the entry plate thickness deviation. [Figure 4]It is a diagram showing the change in the amplitude of the outlet-side plate thickness deviation when the control of the rolling roll gap with respect to the inlet-side plate thickness deviation is delayed by 30 degrees. [Figure 5] It is a diagram showing the change in the amplitude of the outlet-side plate thickness deviation when the control of the rolling roll gap with respect to the inlet-side plate thickness deviation is delayed by 90 degrees. [Figure 6] It is a diagram showing the change in the amplitude of the outlet-side plate thickness deviation when the control of the rolling roll gap with respect to the inlet-side plate thickness deviation is delayed by 180 degrees. [Figure 7] It is a diagram showing the relationship between the phase delay and the amplitude of the outlet-side plate thickness deviation. [Figure 8] It is a diagram showing the relationship between the frequency in Table 2 and the amplitude of the outlet-side plate thickness deviation for each frequency component. [Figure 9] It is a diagram showing the relationship between the frequency in Table 3 and the amplitude of the outlet-side plate thickness deviation for each frequency component. [Figure 10] It is a diagram showing the relationship between the frequency in Table 4 and the amplitude of the outlet-side plate thickness deviation for each frequency component. [Figure 11] It is a flowchart of the optimal compensation time calculation process.

Embodiments for Carrying Out the Invention

[0009] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[0010] (Configuration of Rolling Equipment) The plate thickness control method of the rolling mill according to the present embodiment is performed in rolling equipment. As shown in FIG. 1 which is a schematic view of the rolling equipment 1, the rolling equipment 1 is equipment for rolling the work material W. The work material W is the material (workpiece) to be rolled by the rolling equipment 1. The work material W is in a plate shape. The work material W is, for example, metal or the like.

[0011] The rolling equipment 1 includes a first reel 2, a second reel 3, a direction-changing roll 4, and a multi-stage rolling mill 5.

[0012] The first reel 2 and the second reel 3 are reels around which the material to be rolled W is wound. One of the first reel 2 and the second reel 3 is an unwinding reel for unwinding the material to be rolled W. The other of the first reel 2 and the second reel 3 (the one different from the unwinding reel) is a winding reel for winding the material to be rolled W. The material to be rolled W may be unwound from the first reel 2, rolled by the multi-stage rolling mill 5, and wound onto the second reel 3, or may be unwound from the second reel 3, rolled by the multi-stage rolling mill 5, and wound onto the first reel 2. The above two types of unwinding and winding may be performed alternately, or only one of them may be performed.

[0013] Hereinafter, the upstream side of the multi-stage rolling mill 5 in the moving direction of the material to be rolled W is referred to as the "inlet side", and the downstream side of the multi-stage rolling mill 5 in the moving direction of the material to be rolled W is referred to as the "outlet side".

[0014] The direction-changing roll 4 changes the moving direction (the direction of the path) of the material to be rolled W. In the example shown in FIG. 1, the direction-changing roll 4 is provided between the first reel 2 and the multi-stage rolling mill 5 (in the path of the material to be rolled W) and between the second reel 3 and the multi-stage rolling mill 5, respectively. The direction-changing roll 4 is a cylindrical or columnar member. For example, the direction-changing roll 4 is one provided with a deflector (deflector roll). <000,0101>

[0015] The multi-stage rolling mill 5 is a rolling mill for rolling the material to be rolled W. The multi-stage rolling mill 5 is a rolling mill (cluster rolling mill) provided with a large number of rolls. The multi-stage rolling mill 5 includes a rolling roll 21 and a backup roll 22. Note that the multi-stage rolling mill 5 may include an intermediate roll between the rolling roll 21 and the backup roll 22. <00,00105> Each of the rolls of the multi-stage rolling mill 5 is a cylindrical or columnar member. The roll is rotatably supported by a frame (for example, a housing) not shown. The roll is rotatable about a central axis extending in the longitudinal direction of the roll. Among the large number of rolls, any one roll is a driving roll. The driving roll is driven by a driving device (for example, a driving motor not shown) for driving the roll.

[0017] In this multi-stage rolling mill 5, the material to be rolled W, the rolling rolls 21, and the backup rolls 22 come into contact with each other in that order. The side opposite to the material to be rolled W in this order of contact is called the "roll back side." Specifically, the roll back side of the rolling rolls 21 is the side opposite to the side that contacts the material to be rolled W when viewed from the rolling rolls 21 (relative to the rolling rolls 21), and is the side with the backup rolls 22. The number of stages (number of rolls) in the multi-stage rolling mill 5 can be set in various ways.

[0018] The rolling rolls 21 contact the material to be rolled W and sandwich the material W. The rolling rolls 21 are provided in pairs (two rolls) on both sides of the material W in the thickness direction.

[0019] The backup roll 22 rotatably supports the rolling roll 21 from the rear side of the roll. If an intermediate roll is provided, the backup roll 22 supports the rolling roll 21 from the rear side of the roll via the intermediate roll. In this embodiment, an example of a four-stage rolling mill with one backup roll 22 per rolling roll 21 is shown, but the number of backup rolls 22 can be set in various ways, and it can also be applied to, for example, a 12-stage rolling mill or a 20-stage rolling mill.

[0020] Furthermore, the rolling mill 1 includes a plate thickness detection unit 6, a speed detection unit 7, and a reduction device 8.

[0021] The plate thickness detection unit 6 detects the plate thickness of the rolled material W. The plate thickness detection unit 6 is provided on both sides of the rolling roll 21: on the first reel 2 side (the first reel 2 side in the path of the rolled material W) and on the second reel 3 side. Of the two plate thickness detection units 6, 6, the one located on the entry side functions as the entry-side plate thickness detection unit. Of the two plate thickness detection units 6, 6, the one located on the exit side functions as the exit-side plate thickness detection unit. The entry-side plate thickness detection unit detects the plate thickness of the rolled material W before it is rolled by the rolling roll 21 (entry-side plate thickness). The exit-side plate thickness detection unit detects the plate thickness of the rolled material W after it has been rolled by the rolling roll 21 (exit-side plate thickness).

[0022] The speed detection unit 7 detects the moving speed v of the rolled material W. A speed detection unit 7 is provided on each of the two direction-changing rolls 4. The speed detection unit 7 is a device (sensor, speed detector) that detects the moving speed v. The moving speed v is the peripheral speed of the outer surface of the direction-changing roll 4 (the moving speed of the outer surface in the tangential direction of the outer surface), assuming that there is no slip between the rolled material W and the direction-changing roll 4.

[0023] The reduction device 8 is a device that reduces the rolling rolls 21. The reduction device 8 changes the rolling roll gap ΔS based on the plate thickness detected by the plate thickness detection unit 6. Here, the rolling roll gap ΔS is the gap between a pair of rolling rolls 21. The rolling roll gap ΔS is calculated using the following equation (1) with respect to the deviation of the entry-side plate thickness (entry-side plate thickness deviation) ΔH, etc., based on the entry-side plate thickness detected by the plate thickness detection unit 6. Here, m is the deformation resistance of the rolled material W, M is the Mill constant, and K is the control gain in the gauge meter type. ΔS = K·m / M·ΔH ···Equation (1)

[0024] Here, the rolling reduction device 8 includes a wedge, a hydraulic cylinder, a servo valve, and a servo amplifier. The wedge moves each backup roll 22 by movement, thereby changing the rolling roll gap ΔS. The hydraulic cylinder moves the wedge. The servo valve operates the hydraulic cylinder. Command signals from the control unit 9 are input to the servo amplifier. Based on the command signals input to the servo valve via the servo amplifier, the servo valve is activated, which in turn operates the hydraulic cylinder.

[0025] Furthermore, the rolling mill 1 includes a control unit 9. The control unit 9 is a computer that performs signal input / output, calculations (processing), and information storage. For example, the functions of the control unit 9 are realized by the execution of a program stored in the memory unit of the control unit 9 by the calculation unit. The control unit 9 may be installed inside the rolling mill 1 (within the equipment) or outside the rolling mill 1 (for example, in a control room). The control unit 9 may be a personal computer or may be installed in a control panel.

[0026] The control unit 9 controls the operation of the rolling mill 1. The control unit 9 controls the thickness of the rolled material W. The thickness of the rolled material W detected by the two thickness detection units 6 is input to the control unit 9. The moving speed v of the rolled material W detected by the two speed detection units 7 is also input to the control unit 9.

[0027] The control unit 9 detects the deviation of the thickness of the rolled material W on the entry side (entry side thickness deviation) based on the entry side thickness detection unit 6 of the rolled material W. The entry side thickness deviation is the difference between the actual (detected) thickness of the rolled material W on the entry side and the target thickness.

[0028] The control unit 9 sets the control delay time. The specific method for setting the control delay time is as follows.

[0029] First, the control unit 9 decomposes the input plate thickness deviation ΔH into multiple frequency components. The control unit 9 calculates a phase delay θd (degrees) for each decomposed frequency component. The phase delay θd is determined using a phase diagram, for example, as shown in Figure 2. The phase diagram shown in Figure 2 represents the relationship between the multiple frequency components obtained by decomposing the input plate thickness deviation ΔH and the phase delay θd. The memory unit of the control unit 9 stores a phase diagram like the one shown in Figure 2.

[0030] The control unit 9 calculates the delay time (Td) (seconds) for each frequency component based on the calculated phase delay θd. The delay time (Td) is calculated as (θd / 360) / f, where f is the frequency. Then, the control unit 9 calculates the control delay time (seconds) by summing the delay times (Td) for each frequency component.

[0031] The control unit 9 controls the reduction device 8. The control unit 9 controls the reduction device 8 so that the gap between the rolling rolls 21 becomes the rolling roll gap ΔS calculated based on the entry-side plate thickness deviation ΔH. Here, the control unit 9 corrects the timing of controlling the reduction device 8 based on the control delay time calculated from the entry-side plate thickness deviation ΔH. For example, since there is a delay element in the reduction device 8, the plate thickness accuracy can be improved by advancing the timing of controlling the reduction device 8 by the delay amount, i.e., the control delay time. In some cases, the plate thickness accuracy can also be improved by delaying the timing of controlling the reduction device 8 by the control delay time.

[0032] Here, the phase diagram shown in Figure 2 was obtained as follows. The plate thickness control system is broadly divided into a detection system including a plate thickness detection unit 6, a calculation system including a control unit 9, and a hydraulic system including a reduction device 8. Therefore, assuming that the maximum frequency when the input plate thickness deviation ΔH is decomposed into multiple frequency components is 30 Hz, examples of the phase delay of the detection system (detection phase delay), the calculation system (calculation phase delay), and the hydraulic system (hydraulic system phase delay) were calculated in the frequency range of 0.01 Hz to 30 Hz. The results are shown in Table 1.

[0033] [Table 1]

[0034] In this embodiment, the detection phase delay is approximated by a first-order lag system. The transfer function of the first-order lag system is given by 1 / (Ts+1), where s is the Laplace operator and T is the time constant (seconds). The time constant T is determined by the performance of the sensor. The phase delay of the first-order lag system is given by -atan(wT), where w is the angular frequency and w = 2πf (where f is the frequency).

[0035] The time constant is typically between 0.005 seconds and 0.1 seconds, but in Table 1, the detection phase delay was calculated using a time constant T of 0.01 seconds. For frequencies ranging from 0.01 Hz to 30 Hz, the detection phase delay varies from 0 degrees to -62.1 degrees. A negative detection phase delay indicates that the phase is lagging, not advancing.

[0036] In this embodiment, the calculation phase delay was treated as a constant. In Table 1, the calculation period is usually 0.001 seconds to 0.01 seconds, but in this example, the calculation period (seconds) was set to 0.0050. This calculation period (seconds) is a fixed value determined by the calculation processing capability of the control unit 9.

[0037] The calculation period of 0.0050 seconds was converted to a calculation phase delay (degrees). For example, a frequency of 10 Hz corresponds to a period of 1 / 10 second. Since it takes 1 / 10 second to complete one cycle of 360 degrees, converting 0.0050 seconds to a calculation phase delay gives a calculation phase delay of -0.005 / (1 / 10) × 360 = -18.0 (degrees). The calculation phase delay for frequencies from 0.01 Hz to 30 Hz was calculated in the same manner as described above. The calculation phase delay varies within the range of 0 degrees to -54.0 degrees.

[0038] In this embodiment, the hydraulic system phase lag is approximated by a second-order lag system. Alternatively, the hydraulic system phase lag may be approximated by a first-order lag system. The transfer function of the second-order lag system is wn 2 / (s 2 +2ζwns+wn 2 The phase lag of the hydraulic system is given by -atan(2ζu / (1-u 2 It is given by )), where u = w / wn. The natural frequency wn is given by 2π·fn, where fn is the 90-degree lag frequency (Hz).

[0039] The 90-degree lag frequency fn is typically 1Hz to 50Hz, but for this example, it was set to 50Hz, and the damping coefficient ζ is typically 0.5 to 1.5, but for this example, it was set to 1.0 to calculate the hydraulic system phase lag. Here, the 90-degree lag frequency fn and the damping coefficient ζ are determined by the mechanical structure of the reduction device 8. Therefore, the natural frequency wn is determined by the mechanical structure of the reduction device 8. In the frequency range of 0.01Hz to 30Hz, the hydraulic system phase lag varies from 0 degrees to -61.9 degrees. There is no phase lead in the hydraulic system phase lag; the phase is lagging.

[0040] As described above, by approximating the detection phase delay with a first-order lag system, treating the calculation phase delay as a constant, and approximating the hydraulic system phase delay with a second-order lag system, the detection phase delay, calculation phase delay, and hydraulic system phase delay can be determined with high accuracy.

[0041] The detection phase delay, calculation phase delay, and hydraulic system phase delay, obtained as described above, were summed for each frequency component to determine the phase delay θd for each frequency component. The phase delay θd ranges from -0.08 to -177.98 degrees. Since the value of the phase delay θd is negative, the phase is lagging.

[0042] From the relationship between multiple frequency components and phase lag θd obtained in Table 1, the phase diagram shown in Figure 2 was obtained. It can be seen that the phase lag θd changes in a clean, nearly linear shape. Note that the phase diagram in this embodiment is not limited to that shown in Figure 2.

[0043] The control unit 9 calculates the delay time (Td) (seconds) for each frequency component based on the phase delay θd obtained as described above. As described above, by determining the detection phase delay, which is the phase delay of the detection system, the calculation phase delay, which is the phase delay of the calculation system, and the hydraulic system phase delay, which is the phase delay of the hydraulic system, the delay time (Td) for each frequency component can be calculated with high accuracy.

[0044] Here, we explain that the larger the phase lag θd, the larger the exit-side thickness deviation (deviation in the exit-side thickness of the rolled material W). The exit-side thickness deviation is the value obtained by subtracting the rolling roll gap ΔS from the entry-side thickness deviation ΔH.

[0045] Figures 3 to 6 show the change in the amplitude of the exit plate thickness deviation. Here, we assume that the entry plate thickness deviation ΔH is a sine wave with an amplitude of ±1. The entry plate thickness deviation ΔH = 1·sin(wt) = sin(wt), where w is the angular frequency and t is the time (seconds). We also consider the rolling roll gap ΔS as a sine wave with an amplitude of ±1. The rolling roll gap ΔS = sin(wt-θd), where θd is the phase lag. The exit plate thickness deviation = sin(wt) - sin(wt-θd) = 2sin(θd / 2)·cos(wt+θd / 2). The amplitude of the exit plate thickness deviation is 2sin(θd / 2).

[0046] Figure 3 shows the change in the amplitude of the exit-side plate thickness deviation when there is no phase lag θd in controlling the rolling roll gap ΔS with respect to the entry-side plate thickness deviation ΔH. In this case, the rolling roll gap ΔS = sin(wt). In this case, the exit-side plate thickness deviation becomes 0. This is the optimal state.

[0047] Figure 4 shows the change in the amplitude of the exit thickness deviation when the control of the rolling roll gap ΔS with respect to the entry thickness deviation ΔH is delayed by 30 degrees. When the phase delay θd is 30 degrees, the amplitude of the exit thickness deviation is 2sin(30 / 2) = 0.52. In other words, an exit thickness deviation with an amplitude of ±0.52 remains.

[0048] Figure 5 shows the change in the amplitude of the exit thickness deviation when the control of the rolling roll gap ΔS with respect to the entry thickness deviation ΔH is delayed by 90 degrees. When the phase delay θd is 90 degrees, the amplitude of the exit thickness deviation is 2sin(90 / 2) = 1.41. In other words, an exit thickness deviation with an amplitude of ±1.41 remains.

[0049] Figure 6 shows the change in the amplitude of the exit plate thickness deviation when the control of the rolling roll gap ΔS with respect to the entry plate thickness deviation ΔH is delayed by 180 degrees. When the phase delay θd is 180 degrees, the amplitude of the exit plate thickness deviation is 2sin(180 / 2) = 2. In other words, an exit plate thickness deviation with an amplitude of ±2 remains. The state with a phase delay θd of 180 degrees is a resonance state, which is the worst state in which the amplitude of the exit plate thickness deviation is the largest.

[0050] Figure 7 shows the relationship between the phase lag θd and the amplitude of the exit plate thickness deviation. When the phase lag θd is less than 60 degrees, the amplitude of the exit plate thickness deviation improves, but when the phase lag θd is 60 degrees or more, the amplitude of the exit plate thickness deviation increases.

[0051] Therefore, the control unit 9 compensates the control delay time with a compensation time (Tc) (seconds) so that the phase delay θd (amplitude of the exit plate thickness deviation) becomes smaller. The control unit 9 provisionally sets the compensation time (Tc). Then, the control unit 9 calculates the amplitude of the exit plate thickness deviation of the rolled material W that occurs when the delay time (Td) is compensated with the compensation time (Tc), for each frequency component.

[0052] The control unit 9 changes the compensation time (Tc) to set the optimal compensation time (Tc) as the time at which the sum of the absolute values ​​of the amplitudes calculated for each frequency component is minimized.

[0053] First, Table 2 shows the amplitude of the output plate thickness deviation for each frequency component when the compensation time (Tc) is provisionally set to 0.0214 seconds.

[0054] [Table 2]

[0055] Table 2 shows the delay time (Td) (seconds) when the frequency is 0.01 Hz. The period is the reciprocal of the frequency, which is 100 seconds. Also, it takes 100 seconds to complete one cycle of 360 degrees. Therefore, the delay time (Td) when the frequency is 0.01 Hz is Td = (0.077 / 360) × 100 = 0.0214 seconds.

[0056] Next, the compensation time (Tc) was set. Ideally, Td + Tc = 0. Therefore, the compensation time (Tc) was set to 0.0214 seconds based on the delay time (Td) when the frequency is 0.01 Hz.

[0057] As shown in Table 2, the value of Td+Tc is 0 at a frequency of 0.01Hz, but increases as the frequency increases. θcd (degrees) is the angle equivalent of Td+Tc. θcd can be calculated as 360·(Td+Tc)·f.

[0058] The amplitude of the output plate thickness deviation for each frequency component was determined as follows. When the phase is shifted by θ, the subtraction of sin(wt) and sin(wt-θ) is sin(wt)-sin(wt-θ)=2sin(θ / 2)·cos(wt+θ / 2). Therefore, the maximum amplitude Δhmax is 2sin(θ / 2). Substituting θcd into 2sin(θ / 2) was used to find the maximum amplitude Δhmax.

[0059] Figure 8 shows the relationship between frequency and the amplitude of the exit plate thickness deviation for each frequency component in Table 2. It can be seen that the maximum amplitude Δhmax increases as the frequency value increases. Since all maximum amplitudes Δhmax are positive, it can be seen that the phase is advanced too much. The sum of the absolute values ​​of the maximum amplitudes Δhmax of the exit plate thickness deviation for each frequency component shown in Table 2 is 4.167, which is a large value. For a frequency of 0.01 Hz, the maximum amplitude Δhmax is 0, so Tc = 0.0214 seconds is optimal, but when viewed in the frequency range of 0 to 30 Hz, Tc = 0.0214 seconds is not optimal.

[0060] Next, Table 3 shows the amplitude of the output plate thickness deviation for each frequency component when the compensation time (Tc) (seconds) is set to 0.0165 seconds.

[0061] [Table 3]

[0062] Table 3 shows the delay time (Td) at a frequency of 30 Hz. Since the delay time (Td) at a frequency of 30 Hz is -0.0165 seconds, the compensation time (Tc) was set to 0.0165 seconds so that Td + Tc = 0 at a frequency of 30 Hz. Then, the amplitude of the exit plate thickness deviation was determined in the same manner as in Table 2.

[0063] Figure 9 shows the relationship between frequency and the amplitude of the exit plate thickness deviation for each frequency component, as shown in Table 3. The sum of the absolute values ​​of the maximum amplitude Δhmax of the exit plate thickness deviation for each frequency component shown in Table 3 is 1.933. The maximum amplitude Δhmax is a negative value in the entire frequency range from 0 to 30 Hz. Therefore, it can be seen that the phase is lagging too much.

[0064] Next, Table 4 shows the amplitude of the output plate thickness deviation for each frequency component when the compensation time (Tc) (seconds) is set to 0.0173 seconds.

[0065] [Table 4]

[0066] Table 4 shows that the compensation time (Tc) (seconds) was determined by trial and error to minimize the sum of the absolute values ​​of the amplitude of the output plate thickness deviation for each frequency component. The compensation time (Tc) when the sum of the absolute values ​​of the amplitudes for each frequency was the minimum of 1.493 was 0.0173 seconds.

[0067] Figure 10 shows the relationship between frequency and the amplitude of the output plate thickness deviation for each frequency component in Table 4. Up to around 20 Hz, the maximum amplitude Δhmax is a negative value, and above 20 Hz, the maximum amplitude Δhmax becomes a positive value. In other words, it can be seen that the phase is lagging or leading.

[0068] Based on the above, in this embodiment, 0.0173 seconds was set as the optimal compensation time (Tc).

[0069] The control unit 9 compensates for the control delay time with an optimal compensation time. The timing for controlling the reduction device 8 is corrected based on the control delay time compensated with the optimal compensation time. By compensating for the control delay time with an optimal compensation time, the amplitude of the exit plate thickness deviation can be minimized. This minimizes the exit plate thickness deviation, thus improving plate thickness accuracy.

[0070] (Operation) The rolling mill equipment 1 is configured to operate as follows. The method for controlling the thickness of the rolling mill is as follows.

[0071] A drive unit (not shown) drives the drive rolls, thereby driving the rolling rolls 21. The material to be rolled W is conveyed between the first reel 2 and the second reel 3 and rolled in the multi-stage rolling mill 5. At this time, the control unit 9 controls the rolling of the material to be rolled W by the multi-stage rolling mill 5. Specifically, the control unit 9 controls the thickness of the material to be rolled W. The control unit 9 controls the reduction device 8 so that the gap between the rolling rolls 21 becomes the rolling roll gap ΔS calculated based on the entry-side thickness deviation ΔH. The control unit 9 corrects the timing of controlling the reduction device 8 based on the control delay time calculated from the entry-side thickness deviation ΔH.

[0072] Here, the control unit 9 calculates the optimal compensation time (Tc) and compensates for the control delay time with the optimal compensation time. The following explanation will be given with reference to Figure 11, which is a flowchart of the optimal compensation time calculation process.

[0073] First, the control unit 9 reads the phase diagram registered in the memory unit of the control unit 9 (step S1). In this embodiment, the phase diagram shown in Figure 2 is read.

[0074] Next, the control unit 9 detects the entry-side plate thickness deviation ΔH (step S2). Specifically, it detects the deviation of the entry-side plate thickness of the rolled material W (entry-side plate thickness deviation) based on the entry-side plate thickness of the rolled material W detected by the entry-side plate thickness detection unit 6.

[0075] Next, the control unit 9 sets the maximum frequency fmax(Hz) of the input plate thickness deviation ΔH (step S3). Specifically, the maximum frequency fmax(Hz) is determined by decomposing the input plate thickness deviation ΔH into multiple frequency components and set as the control unit. Note that the operator may also set the maximum frequency fmax(Hz). In this case, the maximum frequency fmax(Hz) is set to a frequency that is unlikely to be higher than this frequency.

[0076] The control unit 9 sets the minimum frequency fmin(Hz) of the input plate thickness deviation ΔH to a value as close to zero as possible. While a minimum frequency fmin(Hz) of zero is desirable, calculations cannot be performed with zero. The frequency pitch between the minimum frequency fmin and the maximum frequency fmax is set as appropriate. For example, the pitch is set to 5Hz. Note that the pitch does not need to be constant.

[0077] Next, the control unit 9 calculates the delay time (Td) (seconds) for each frequency component of the input plate thickness deviation ΔH (step S4). The control unit 9 converts the phase delay θd for each frequency component, obtained from the phase diagram, into a delay time (Td) (seconds).

[0078] Next, the control unit 9 calculates the control delay time (seconds) (step S5). Specifically, it calculates the control delay time by summing the delay times (Td) for each frequency component.

[0079] Next, the control unit 9 provisionally sets the compensation time (Tc) (seconds) (step S6). For example, the compensation time (Tc) is provisionally set to 0.0165 seconds, which is the smallest delay time (Td) in Tables 2 to 4, which is -0.0165 seconds.

[0080] Next, the control unit 9 changes the compensation time (Tc) in small increments starting from 0.0165 seconds (step S7) to determine whether the amplitude of the exit plate thickness deviation has been minimized (step S8). If it is determined in step S8 that the amplitude of the exit plate thickness deviation has not been minimized (S8: NO), the control unit 9 returns to step S7. On the other hand, if it is determined in step S8 that the amplitude of the exit plate thickness deviation has been minimized (S8: YES), the control unit 9 sets the compensation time (Tc) that minimizes the amplitude of the exit plate thickness deviation as the optimal compensation time (Tc) (step S9). In this embodiment, as shown in Table 4, the optimal compensation time (Tc) is 0.0173 seconds.

[0081] Next, the control unit 9 determines whether or not to continue the calculation (step S10). If it determines in step S10 to continue the calculation (S10:YES), the control unit 9 returns to step S2. On the other hand, if it determines in step S10 not to continue the calculation (S10:NO), the control unit 9 terminates this flow.

[0082] (effect) As described above, according to the rolling mill thickness control method of this embodiment, the amplitude of the exit thickness deviation of the rolled material W, which occurs when the delay time (Td), which is the control delay time for each frequency component, is compensated by the compensation time (Tc), is calculated for each frequency component. The compensation time (Tc) is then changed, and the compensation time at which the sum of the absolute values ​​of the exit thickness deviation amplitudes is minimized is set as the optimal compensation time (Tc). The control delay time is then compensated by the optimal compensation time (Tc). As a result, the timing for controlling the rolling device 8 is corrected based on the control delay time compensated by the optimal compensation time (Tc). By compensating the control delay time with the optimal compensation time (Tc), the amplitude of the exit thickness deviation can be minimized. As a result, the exit thickness deviation can be minimized, and thus the thickness accuracy can be improved.

[0083] Furthermore, the phase delay θd includes the detection phase delay that occurs when detecting the entry-side plate thickness deviation ΔH, the calculation phase delay that occurs when calculating the rolling roll gap ΔS, and the hydraulic system phase delay that occurs due to the operation of the reduction device 8. The plate thickness control system can be broadly divided into a detection system that detects the entry-side plate thickness deviation ΔH, a calculation system that calculates the rolling roll gap ΔS, and a hydraulic system that includes the reduction device 8. Therefore, by determining the detection phase delay, which is the phase delay of the detection system, the calculation phase delay, which is the phase delay of the calculation system, and the hydraulic system phase delay, which is the phase delay of the hydraulic system, the delay time (Td) for each frequency component can be calculated with high accuracy.

[0084] In the above embodiment, the phase delay was divided into three parts: detected phase delay, calculated phase delay, and hydraulic system phase delay. However, since the calculated phase delay is a constant, it may be included in the calculation along with the detected phase delay or the hydraulic system phase delay.

[0085] Furthermore, the detection phase delay is approximated by a first-order lag system, the calculation phase delay is treated as a constant, and the hydraulic system phase delay is approximated by a second-order lag system. In the first-order lag system, the time constant T is determined by the performance of the sensor. The calculation period (seconds) when calculating the rolling roll gap ΔS is determined by the processing power. In the second-order lag system, the natural frequency wn and the damping coefficient ζ are determined by the mechanical structure of the reduction device 8. Therefore, by approximating the detection phase delay by a first-order lag system, treating the calculation phase delay as a constant, and approximating the hydraulic system phase delay by a second-order lag system, the detection phase delay, calculation phase delay, and hydraulic system phase delay can be determined with high accuracy.

[0086] In the above embodiment, the detection phase delay was approximated by a first-order lag system, the calculation phase delay was treated as a constant, and the hydraulic system phase delay was approximated by a second-order lag system. However, other phase delay models may also be applied.

[0087] Although embodiments of the present invention have been described above, these are merely illustrative examples and do not particularly limit the present invention. Specific configurations and other aspects can be modified as appropriate. Furthermore, the actions and effects described in the embodiments of the invention are merely a list of the most preferred actions and effects resulting from the present invention, and the actions and effects according to the present invention are not limited to those described in the embodiments. [Explanation of symbols]

[0088] 1. Rolling equipment 2. Reel 1 3. Reel 2 4-way change roll 5. Multi-stage rolling mill 6. Plate thickness detection unit 7 Speed ​​detection unit 8. Pressure reduction device 9. Control Unit 21 Rolling Rolls 22 Backup Roles

Claims

1. A method for controlling the thickness of a rolling mill, which involves detecting an entry-side thickness deviation of a rolled material being rolled by a pair of rolling rolls of the rolling mill, controlling a reduction device that reduces the rolling rolls so that the gap between the rolling rolls becomes the rolling roll gap calculated based on the entry-side thickness deviation, and correcting the timing of controlling the reduction device based on a control delay time, The input plate thickness deviation is decomposed into multiple frequency components, the delay time for each frequency component is calculated, and the control delay time, which is the sum of the calculated delay times, is calculated. To determine the optimal compensation time for compensating the control delay time so that the amplitude of the phase lag or the deviation of the thickness deviation at the exit side of the rolled material is reduced, the following steps are performed: A provisional compensation time of 1 or more is set such that the sum of the delay times for each frequency component is small, and for each compensation time, the amplitude of the exit thickness deviation of the rolled material that occurs when the delay time is compensated with that compensation time is calculated for each frequency component, the sum of the absolute values ​​of the calculated amplitudes for each frequency component is calculated, and the compensation time that minimizes the sum is set as the optimal compensation time. The control delay time is compensated by the aforementioned optimal compensation time. A method for controlling the thickness of a rolling mill, characterized by correcting the timing of controlling the reduction device based on the control delay time compensated by the optimal compensation time.

2. Based on the phase delay for each frequency component, the delay time for each frequency component is calculated. The method for controlling the thickness of a rolling mill according to claim 1, characterized in that the phase delay includes a detection phase delay that occurs when detecting the input plate thickness deviation, a calculation phase delay that occurs when calculating the rolling roll gap, and a hydraulic system phase delay that occurs due to the operation of the reduction device.

3. The detection phase delay is approximated by a first-order lag system, The aforementioned calculation phase delay is set to a constant, The method for controlling the plate thickness of a rolling mill according to claim 2, characterized in that the hydraulic system phase lag is approximated by a second-order lag system.

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