Meandering correction device and meandering correction method for metal strip

Abstract

Provided are a meandering correction device and a meandering correction method with which it is possible to perform meandering control with high responsiveness even when the distance between a steering roll and a position to be controlled is separated and a waste in time of transfer is large in meandering control of a metal band. This meandering correction device for a metal band includes: a first meandering amount detection part; a steering roll; a tilting device for the steering roll; a second meandering amount detection part; a first control part that corrects the shift amount of the position to undergo meandering control on the basis of the first meandering amount in consideration of the conveyance time from the steering roll position to the position to undergo meandering control; and a second control part that controls the width direction position of the metal band by means of the steering roll on the basis of the second meandering amount and the corrected shift amount.

Description

MEANING CORRECTION DEVICE AND MEANING CORRECTION METHOD FOR MEANING OF METAL STRIP

[0001] The present invention relates to a meandering correction device and a meandering correction method for suppressing meandering of a metal strip caused by a steering roll in a metal strip annealing or processing facility.

[0002] In the manufacturing process of a strip-shaped metal plate (also referred to as a "metal strip"), the metal strip is transported using a plurality of rolls in order to efficiently perform plastic working, heat treatment, surface chemical conversion treatment, etc. on the metal sheet. However, during this process, meandering of the metal strip occurs due to asymmetry of the metal strip itself (defective shape and residual stress) and asymmetry of the equipment (roll alignment). Therefore, to prevent meandering of the metal strip, it is common to provide a crown (profile) to the roll to center it, or to control the meandering using a steering roll based on the amount of meandering measured with a meander meter.

[0003] Patent Document 1 discloses a technology that uses multiple meandering detectors to predict the amount of meandering at a reference roll position, and corrects the amount measured by the master meandering amount detector, thereby enabling the amount of meandering at a target position to be controlled with a single steering roll.

[0004] Patent Document 2 discloses a technology that predicts the amount of meandering downstream of a steering roll using a model formula, and enables control of the upstream steering roll while taking into account the meandering downstream of the meander correction area.

[0005] JP 2020-164284 JP 5-208763

[0006] However, when attempting to apply the above-mentioned conventional technologies to suppress metal strip meandering, the following problems arise. Regarding Patent Document 1, the transport time of the metal strip between the master (meander amount detection unit: meander amount reference roll position) and the slave (meander amount detection unit: downstream of the steering roll in the strip threading line) is not taken into account. Therefore, if the metal strip vibrates and there are only two detectors, the meander amount at the reference roll position may diverge. Regarding Patent Document 2, there is no mechanism for applying correction based on the actual meander amount downstream of the steering roll, so the meandering is not necessarily corrected downstream. Furthermore, as shown in Figure 2, the conventional technology requires a dead time to correct the meander amount at the detector, which is the position to be controlled. If the control time interval is sufficiently shorter than the dead time, the controller repeats operations until the meander amount is corrected, resulting in an operation amount greater than the amount required for correction. Repeated excessive operation amount exacerbates meandering, leading to vibration and divergence of the meander amount, and if the metal strip comes into contact with surrounding equipment, the metal strip may break.

[0007] The present invention was developed in consideration of the above-mentioned problems of the prior art, and its purpose is to provide a meandering correction device and a meandering correction method that enable highly responsive meandering control even in situations where there is a restriction that a steering roll cannot be installed near the object of metal strip meandering amount control, and even when the steering roll and the object of control (the position of the metal strip meandering amount control object) are far apart and the transport time of the metal strip is long over that distance.

[0008] In order to solve the above problem, the inventors discovered that by performing feedback that takes into account the dead time due to the amount of meandering at the controlled position and calculating an appropriate manipulated variable as shown in Figure 3, it is possible to stably correct meandering without vibration or divergence even when the dead time is longer than the control interval, and this led to the present invention. The meandering correction device according to the present invention, which advantageously solves the above problem, is configured as follows.

[0009] [1] A meandering correction device for correcting meandering of a metal strip transported on a strip threading line, comprising: a first meandering amount detection unit disposed at a position targeted for meandering control of the metal strip and detecting a first meandering amount of the metal strip; a steering roll disposed to correct the first meandering amount; a tilting device for the steering roll; a second meandering amount detection unit disposed downstream of the steering roll position in the strip threading line and upstream of the position targeted for meandering control in the strip threading line and detecting a second meandering amount of the metal strip; a first control unit that corrects a shift amount of the position targeted for meandering control based on the first meandering amount, taking into account the transport time from the steering roll position to the position targeted for meandering control; and a second control unit that controls the widthwise position of the metal strip by the steering roll based on the second meandering amount and the corrected shift amount.

[0010] A meandering correction method according to the present invention that advantageously solves the above-mentioned problems is configured as follows: [2] A method for correcting meandering of a metal strip transported on a strip threading line, comprising the steps of detecting a first meandering amount at a meandering control target position of the metal strip, controlling a shift amount at the meandering control target position by tilting a steering roll, detecting a second meandering amount downstream of the steering roll position in the strip threading line and upstream of the meandering control target position in the strip threading line, correcting the shift amount of the meandering control target position based on the first meandering amount in consideration of the transport time from the steering roll position to the meandering control target position, and controlling the widthwise position of the metal strip by the steering roll based on the second meandering amount and the corrected shift amount.

[0011] According to the present invention, by taking the transport time into consideration, stable meandering control can be achieved with a single steering roll even when, due to equipment reasons, it is not possible to install a steering roll near the roll that serves as the reference for the meandering amount (the position where the metal strip is to be controlled for meandering) and when the distance from the roll that serves as the reference for the meandering amount to the steering roll that can be used is far.

[0012] 1 is a schematic diagram showing the configuration of a metal strip meandering correction device according to an embodiment of the present invention; FIG. 2 is an explanatory diagram of a metal strip meandering correction by meandering control of the prior art; and FIG. 3 is an explanatory diagram of a metal strip meandering correction by meandering control of the present invention. FIG. 4(a) is a graph showing a shift amount input (S) with respect to the passage of time at the point of the second detector. ２ ) change amount ΔS ２ , and (b) is a graph of the shift amount input (S １ ) change amount ΔS １ 1 is a graph showing a comparison of the maximum meandering amount with respect to actual data when the transport time L after meandering control is 60 s, with A (comparative example) being proportional control (without transport time compensation), B (example of the invention) being a combination of proportional control (with transport time compensation) and Smith compensation, and C (example of the invention) being a combination of sliding mode control (with transport time compensation) and Smith compensation.

[0013] The following describes a metal strip meandering correction device and method according to this embodiment. In this invention, in a device having two or more meandering detectors, feedback taking into account the transport time due to a first meander amount measured by a detector (hereinafter referred to as the first detector) at a position subject to meandering control (downstream of the strip threading line) is returned to the shift amount of the detector used for main control (hereinafter referred to as the second detector). Next, the target value of the metal strip position is shifted in advance at the position of the second detector, so that the metal strip position as measured by the first detector at the position subject to control is aligned with the target. Even in situations where there are constraints such as not being able to install a steering roll near the control target, and when the steering roll and the control target are far apart and the transport time over that distance is long, highly responsive meandering control is possible, thereby reducing problems such as metal strip breakage.

[0014] <Meandering Correction Device> The metal strip meandering correction device according to this embodiment includes a first meandering amount detection unit disposed at a meandering control target position of the metal strip and detecting a first meandering amount of the metal strip, a steering roll disposed to correct the first meandering amount, a steering roll tilting device, and a second meandering amount detection unit disposed downstream of the steering roll position in the strip threading line and upstream of the meandering control target position in the strip threading line and detecting a second meandering amount of the metal strip. The device further includes a first control unit that corrects a shift amount of the meandering control target position based on the first meandering amount taking into account the transport time from the steering roll position to the meandering control target position, and a second control unit that controls the widthwise position of the metal strip using the steering roll based on the second meandering amount and the corrected shift amount.

[0015] [First Meandering Amount Detection Unit] As shown in Figure 1, in the first meandering amount detection unit M1, a first meandering amount detector 1 is installed at a position on the strip threading line that is the target of meandering control of the metal strip (meandering control target position), i.e., at the position of the reference roll 8. The control target position of the first meandering amount detection unit M1 is a position that serves as a reference for controlling the meandering amount of the metal strip. The first detector 1 may be selected based on the measurement environment and equipment.

[0016] [Steering Roll and Tilting Device] As shown in Figure 1, in order to correct meandering of the metal strip at the position of the second detector 2, a steering roll 3 and its tilting device 4 (actuator 41, cylinder 42) are installed upstream of the strip threading line (meaning upstream of the strip threading line in the line traveling direction 11) from the position (position to be controlled) of the first meandering amount detector 1 of the first meandering amount detection unit M1. There is no particular limit on the distance between the steering roll 3 and the first meandering amount detector 1. In addition, strip threading equipment 9 may be provided between the steering roll 3 and the first meandering amount detector 1.

[0017] 1, in order to measure the amount of meandering upstream of the position of the first meandering amount detector 1 (the position subject to meandering control) of the first meandering amount detection unit M1 in the strip threading line, the second meandering amount detector 2 of the second meandering amount detection unit M2 is installed at a position upstream of the first meandering amount detector 1. Furthermore, since the second meandering amount detector 2 aims to control the amount of meandering caused by the steering roll, the second meandering amount detector 2 is installed downstream of the position of the steering roll 3 in the strip threading line and upstream of the position of the first meandering amount detector 1 (the position subject to meandering control).

[0018] [Control Unit] As shown in FIG. 1 , the control unit includes a first control unit and a second control unit. The first control unit 6 measures the position of the metal strip using a first meander amount detector 1 installed at the target position for meander control (the meander control target position). The first control unit 6 calculates the meander amount based on the relationship between the line center 12 and the shift amount of the metal strip at the target position for meander control, and sends the calculated meander amount to a calculation device. Because the transport time is significantly longer than the control interval, Smith compensation is added to the calculation process. To compensate for the low tolerance to external disturbances, which is a weakness of Smith compensation, stable meander control is achieved by determining the manipulated variable using highly robust sliding mode control. However, as long as the required performance of meander control is sufficiently met, conventional PID control can also be effective. The change in the metal strip shift amount calculated using the above method is added to the currently set metal strip shift amount for correction, and an updated shift setting for the first meander amount detector 1 position (the target position for meander control) is obtained.

[0019] The second control unit 7 controls the position of the second meander amount detector 2 so as to reduce the meander amount at the meander control target position (position of the first meander amount detector 1) based on the meander amount at the position of the second meander amount detector and the updated shift setting amount (corrected shift amount) transmitted from the first control unit 6. Based on this controlled value, the operating state of the steering roll is instructed so as to achieve the target position of the second meander amount detector 2 (set strip threading position). In this way, the strip threading position at the position of the second meander amount detector 2 is changed.

[0020] <Meandering Correction Method> The metal strip meandering correction method according to this embodiment is a method for correcting meandering of a metal strip being transported along a strip threading line, and includes the steps of detecting a first meandering amount at a meandering control target position of the metal strip, controlling a shift amount of the meandering control target position by tilting a steering roll, detecting a second meandering amount downstream of the steering roll position in the strip threading line and upstream of the meandering control target position in the strip threading line, correcting the shift amount of the meandering control target position based on the first meandering amount in consideration of the transport time from the steering roll position to the meandering control target position, and controlling the widthwise position of the metal strip by the steering roll based on the second meandering amount and the corrected shift amount.

[0021] [First Meandering Amount Detection Step] The first meandering amount detector 1 of the first meandering amount detection unit M1 measures a first meandering amount at a position that is a target of meandering control of the metal strip (meandering control target position).

[0022] [Second meandering amount detection step] The second meandering amount detector 2 of the second meandering amount detection unit M2 measures the second meandering amount at a position upstream of the strip threading line from a position targeted for meandering control (meandering control target position) and downstream of the steering roll position. The measurement by the second meandering amount detector 2 is for the purpose of performing meandering control using the steering roll.

[0023] [Control Step] The control step for meander correction is explained in detail with reference to Figure 1. The second meander amount detection unit M2 corrects the first meander amount measured in the first meander amount detection step by a shift amount of the meander control target position taking into account the transport time so that the metal strip passes through the set threading position. Next, the widthwise position of the metal strip is controlled by the steering rolls based on the meander amount at the set threading position and the corrected shift amount.

[0024] The preparation and calculation flow up to the introduction of control are shown below. Figure 4 shows the change in the position of the metal strip at the position of the first detector when the set value of the shift amount of the second detector is changed in a stepwise manner. The change in the position of the metal strip at the position of the first detector in response to the change in the shift amount is delayed from the time when the set value is changed by the transport time L (= D / V) determined by the distance D from the steering roll to the first detector and the transport speed V of the metal strip (t １ ). The response is further delayed by the operation of the cylinder and friction between the metal strip and the rolls on the way to the first detector. Taking this into account, a model is created to predict the position of the metal strip. First, it is assumed that the response delays due to the operation of the cylinder and friction with the rolls are all first-order lags. In this case, the transfer function at the first detector is －Ｌｓ The following equation (1) is obtained by including

[0025]

[0026] Here, n is the number of rolls that the metal strip including the steering roll passes through before the first detector, Ti is the time constant of the delay in the change due to the operation of the cylinder or the friction of the roll, and K is the change amount ΔS of the set value of the shift amount. ２ The amount of actual change in the metal band position ΔS at the position of the first detector relative to １ and can be expressed by equation (2).

[0027]

[0028] If there are two or more rolls, the delay will be third or higher order, but in normal control design, it is approximated by a second order delay even in such cases. Therefore, equation (1) is approximated as the following equation (3).

[0029]

[0030] Here, T Ｃ is the time constant of the delay due to the cylinder, T Ｒ is the time constant of the response delay due to roll friction. Ｃ can be obtained directly from the operation of the cylinder, or if the steering roll and the second detector are close enough, it can be estimated from the change in the position of the metal band at the second detector when the shift amount is input in steps. Ｒis the amount of change in the first detector when a step is input and the T obtained in the transfer function of equation (3) Ｃ The results into which the above equations are substituted are compared by simulation, etc., and the one closest to the actual behavior is selected. The amount of meandering of the metal strip in the future is predicted from the transfer function obtained. The transfer function obtained by equation (3) is used to calculate the transport time element e －Ｌｓ The state equation is obtained by performing an inverse Laplace transform on the result excluding the above. The state equation is the following equation (4). When using sliding mode control, equation (4) is used.

[0031]

[0032] Here, χ and χ (χ represents a symbol with a dot on χ) are the meandering amount and meandering speed measured by the first detector 1, respectively, and u is the shift change amount. Next, since Smith compensation uses a predicted value of the metal strip position after a transport time L for control, we consider an equation for predicting the metal strip position. As shown in Figure 5, it takes transport time L for the metal strip position to change at the position of the first detector 1 due to a change in the shift amount. u in Figure 5 （ｉ－ｎ） is the amount of past shift change, and the larger n, the further back in time it is. Therefore, the amount by which the position of the metal strip changes within L seconds is proportional to the total amount of change in the shift amount over the past L seconds. Also, since the total amount of change in the shift amount does not simply move immediately, and there is a response delay, the following equation (5) is used.

[0033]

[0034] Generally, the relationship between the operation amount (shift change amount in this embodiment) and the control amount (snaking amount in this embodiment) is expressed by equation (5) where t is the current time, and the predicted value of the metal strip position (including the corrected speed) can be expressed by the following equation (6) using the current measurement value and the past performance of the operation amount. Here, X ｉ、 X ｉ (X represents a symbol with a dot on top of it) is the meandering amount and meandering speed at the current time measured by the first detector 1. At this time, the transport time L is set to be an integer multiple of the control interval Δt (L=NΔt).

[0035]

[0036] In this embodiment, ω１ = 1 / T Ｃ , ω ２ = 1 / T Ｒ The second term can be substituted with only four arithmetic operations by using the numerical solution of the following differential equation. An example of the calculation flow is shown in Figure 6. Finally, the feedback of the difference between the current performance value in Smith compensation and the predicted value L seconds ago is added to equation (6) and input to the controller as equation (7).

[0037]

[0038] When using sliding mode control (SMC), the shift change amount is expressed by equation (8) using equation (4).

[0039]

[0040] In equation (8), S is a parameter that determines the hyperplane in sliding mode control, δ is a parameter for preventing chattering, and G is a gain setting value. Finally, the output u(i) (change in shift amount) from the controller is added to the current shift amount setting value to update the shift amount.

[0041] The effects of this embodiment will be specifically described below based on examples, but the present invention is not limited to these examples.

[0042] Figure 7 shows the results of a simulation using actual data on the maximum meander amount at the meander control target position, with a conveying time L of 60 seconds. Case A is proportional control without compensation for conveying time, and corresponds to a comparative example of the prior art. Cases B and C are examples of the present invention, with Case B using proportional control and Case C using sliding mode control (SMC). It was predicted that Cases B and C would improve the maximum meander amount by up to 12% compared to Case A, which does not compensate for conveying time. In fact, meander correction using Cases A, B, and C was performed on a strip threading line consisting of the equipment shown in Figure 1. As with the above simulation, the meander control method of the present invention, which takes conveying time into account, improved the maximum meander amount by up to 12% compared to the meander control method that does not take conveying time into account.

[0043] From the above examples, it has become possible to stably control the meandering using the steering roll when, due to equipment reasons, it is not possible to install a steering roll near the roll that is used as the reference for the meandering amount and when the distance from the steering roll is far from the roll that is used as the reference for the meandering amount.

[0044] M1 First meandering amount detection unit M2 Second meandering amount detection unit 1 First meandering amount detector 2 Second meandering amount detector 3 Steering roll 4 Tilting device 41 Actuator 42 Cylinder 6 First control unit 7 Second control unit 8 Reference roll 9 Equipment 11 Line travel direction 12 Line center

Claims

1. A meandering correction device for correcting the meandering of a metal strip transported on a strip passing line, comprising: a first meandering amount detection unit arranged at a meandering control target position of the metal strip and detecting a first meandering amount of the metal strip; a steering roll arranged to correct the first meandering amount; a tilting device for the steering roll; a second meandering amount detection unit arranged downstream of the steering roll position and upstream of the meandering control target position on the strip passing line and detecting a second meandering amount of the metal strip; a first control unit for correcting the shift amount of the meandering control target position based on the first meandering amount, taking into account the transport time from the steering roll position to the meandering control target position; and a second control unit for controlling the widthwise position of the metal strip by the steering roll based on the second meandering amount and the corrected shift amount.

2. A method for correcting the meandering of a metal strip transported on a strip passing line, comprising the steps of: detecting a first meandering amount at a position where the metal strip is subject to meandering control; controlling a shift amount at the position where the meandering control is subject by tilting a steering roll; detecting a second meandering amount downstream of the steering roll position and upstream of the position where the meandering control is subject to control, in the strip passing line; correcting the shift amount of the position where the meandering control is subject based on the first meandering amount, taking into account the transport time from the steering roll position to the position where the meandering control is subject to control; and controlling the widthwise position of the metal strip by the steering roll based on the second meandering amount and the corrected shift amount.

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