MEANING CORRECTION DEVICE AND MEANING CORRECTION METHOD FOR MEANING OF 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

[Technical Field]

[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. [Background technology]

[0002] In the manufacturing process of strip-shaped metal sheets (also called "metal strips"), the metal strips are transported using multiple rolls in order to efficiently perform plastic working, heat treatment, surface chemical conversion treatment, etc. However, during this process, the metal strips tend to meander due to asymmetries in the metal strip itself (defective shape and residual stress) and asymmetries in the equipment (roll alignment). Therefore, in order to prevent the metal strip from meandering, it is common to give the roll a crown (profile) to center it, or to control the meandering with 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 control of the amount of meandering at a target position 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. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-164284 [Patent Document 2] Japanese Patent Application Publication No. 5-208763 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when the above-mentioned conventional technology is applied to suppressing meandering of a metal strip, the following problems arise. In Patent Document 1, the transport time of the metal strip between the master (meandering amount detection unit: meandering amount reference roll position) and the slave (meandering amount detection unit: downstream side of the steering roll in the strip threading line) is not taken into consideration, and if the metal strip vibrates and there are about two detection units, the meandering amount at the reference roll position may diverge. In Patent Document 2, there is no mechanism for applying correction based on the actual amount of meandering downstream of the steering roll, and the meandering is not necessarily corrected on the downstream side. Furthermore, with conventional technology, as shown in Figure 2, it takes time for the amount of meandering at the detector, which is the position to be controlled, to be corrected by the amount of dead time, and if the control time interval is sufficiently shorter than the dead time, the controller will repeat operations until the amount of meandering is corrected, resulting in an operation amount greater than that required for correction. Repeated excessive operation amounts will encourage meandering, leading to vibration and divergence of the meandering amount, and if it comes into contact with surrounding equipment, the metal strip will 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 constraint that a steering roll cannot be installed near the object to be controlled for the amount of meandering of the metal strip, and even when the distance between the steering roll and the object to be controlled (the position of the object to be controlled for the amount of meandering of the metal strip) is large and the transport time of the metal strip is long over that distance. [Means for solving the problem]

[0008] To solve the above problems, we have discovered that by performing feedback that takes into account the dead time due to the amount of meandering of the control target position as shown in Figure 3 and calculating an appropriate manipulated variable, it is possible to stably correct meandering without oscillation or divergence even when the dead time is longer than the control interval, which led to the present invention. The meandering correction device according to the present invention, which advantageously solves the above-mentioned problems, is configured as follows.

[0009] [1] A meandering correction device for correcting the 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 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 the 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] The meandering correction method according to the present invention, which advantageously solves the above problem, 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, taking into account 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. [Effects of the Invention]

[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 is used 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 is used as the reference for the meandering amount to the steering roll that can be used is far. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram showing the configuration of a metal strip meandering correction device according to an embodiment of the present invention; [Figure 2] 1 is an explanatory diagram of a meandering correction of a metal strip by a meandering control of the prior art; [Figure 3] 1 is an explanatory diagram of a meandering correction of a metal strip by the meandering control of the present invention. FIG. [Figure 4] (a) is a graph of the change ΔS2 in the shift amount input (S2) over time at the point of the second detector, and (b) is a graph of the change ΔS1 in the shift amount input (S1) over time at the point of the first detector. [Figure 5] FIG. 2 is an explanatory diagram of an example of a meandering prediction model in the meandering correction method of the present invention. [Figure 6] This is the calculation flow of formula (6,4) for predicting the position of the metal band. [Figure 7] This graph compares and evaluates the maximum meandering amount against actual data when the transport time after meandering control is L = 60 seconds, with A (comparison example) being proportional control (without transport time compensation), B (example of invention) being a combination of proportional control (with transport time compensation) and Smith compensation, and C (example of invention) being a combination of sliding mode control (with transport time compensation) and Smith compensation. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, a description will be given of a metal strip meandering correction device and a meandering correction method according to this embodiment. In this invention, in an apparatus having two or more meandering detectors, feedback that takes into account the transport time due to the first meandering amount measured by a detector (hereinafter referred to as the first detector) at the 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 at the first detector at the position subject to control is set to the target. Even in situations where there are constraints such as not being able to install a steering roll near the control target, and 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 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 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 Tilt Device] As shown in Figure 1, in order to correct the 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 travel 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 installed between the steering roll 3 and the first meandering amount detector 1.

[0017] [Second meandering amount detection unit] As shown in Figure 1, in order to measure the amount of meandering upstream of the position of the first meandering amount detector 1 of the first meandering amount detection unit M1 (the position subject to meandering control) in the strip threading line, the second meandering amount detector 2 of the second meandering amount detection unit M2 is installed at that upstream position. 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 steering roll 3 position 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 meandering amount detector 1 installed at the target position for meandering control (meandering control target position), calculates the amount of meandering from the relationship between the line center 12 and the shift amount of the metal strip at the meandering control target position, and sends the calculated amount of meandering to the calculation device. Because the transport time is sufficiently longer than the control interval, Smith compensation is added to the calculation process. In addition, to compensate for the low resistance to disturbances, which is a weakness of Smith compensation, stable meandering control is possible by determining the manipulated variable using sliding mode control, which has excellent robustness. However, if the required performance of meandering control is sufficiently met, ordinary PID control can also be effective. The change in the shift amount of the metal band calculated using the above method is added to the currently set shift amount of the metal band for correction, and an updated shift setting amount for the first meandering amount detector 1 position (position subject to meandering control) is obtained.

[0019] The second control unit 7 controls the position of the second meandering amount detector 2 so as to reduce the meandering amount at the meandering control target position (position of the first meandering amount detector 1) based on the meandering amount at the position of the second meandering 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 meandering amount detector 2 (set strip passing position). In this way, the strip passing position at the position of the second meandering amount detector 2 is changed.

[0020] <Meandering correction method> The method for correcting meandering of a metal strip 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 position where meandering control is to be performed for the metal strip, controlling the shift amount of the position where meandering control is to be performed 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 position where meandering control is to be performed for the metal strip, correcting the shift amount of the position where meandering control is to be performed based on the first meandering amount, taking into account the transport time from the steering roll position to the position where meandering control is to be performed, 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 (a meandering control target position).

[0022] [Second meander 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 on the strip threading line upstream of the position targeted for meandering control of the metal strip (meandering control target position) and downstream of the steering roll position. Measurement by the second meandering amount detector 2 is performed to control meandering using the steering roll.

[0023] [Control Step] FIG. 1 shows the control steps for meandering correction in detail. The second meandering amount detection unit M2 corrects the first meandering amount measured in the first meandering amount detection step by a shift amount of the meandering control target position taking into account the transport time so that the metal strip passes through the set strip passing position. Next, the width direction position of the metal strip is controlled by the steering roll based on the meandering amount of the set strip passing position and the corrected shift amount.

[0024] The preparation and calculation flow leading up to the introduction of control is shown below. Figure 4 shows the change in the metal strip position at the first detector position when the set value for the shift amount of the second detector is changed in steps. The change in the metal strip position at the first detector position in response to a change in the shift amount is delayed (t1) from the time the set value is changed by the transport time L (= D / V), which is determined by the distance D from the steering roll to the first detector and the transport speed V of the metal strip. The response is further delayed by the operation of the cylinder and friction between the metal strip and the rolls between the metal strip and the first detector. Taking this into account, a model is developed to predict the position of the metal band. First, it is assumed that the response delay due to the operation of the cylinder and friction with the roll is all first-order lag. The transfer function at the first detector at this time is -Ls This results in the following equation (1).

[0025]

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[0026] Here, n is the number of rolls that the metal strip, including the steering roll, passes through before reaching the first detector, Ti is the time constant for the delay in change due to cylinder operation or roll friction, and K is the ratio of the actual change in the metal strip position at the first detector position, ΔS1, to the change in the set value of the shift amount, ΔS2, and can be expressed by equation (2).

[0027]

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[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]

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[0030] where 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. T 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. R is the change in the first detector when a step is input and the T obtained from the transfer function of equation (3) C The results into which the above is substituted are compared using simulations, etc., and the one that is closest to the actual behavior is selected. The amount of future meandering of the metal strip is predicted from the transfer function obtained. The transfer function obtained by equation (3) is the transport time element e -Ls The state equation is obtained by performing an inverse Laplace transform on the equation excluding the above. The state equation is given by the following equation (4). When using sliding mode control, equation (4) is used.

[0031]

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

[0033]

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[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 an X) is the meandering amount and meandering speed measured by the first detector 1 at the current time. At this time, the transport time L is set to be an integer multiple of the control interval Δt (L=NΔt).

[0035]

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[0036] In this embodiment, ω1=1 / T C , ω2=1 / T R is. The second term can be substituted using 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]

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

[0039]

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[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 the gain setting. Finally, the output u(i) (change in shift amount) from the controller is added to the current shift amount setting to update the shift amount. [Example]

[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 when the transport time L at the target location for meander control is 60 seconds. Case A is proportional control without transport time compensation and corresponds to a comparative example of conventional technology. Cases B and C are examples of the invention, with Case B using proportional control and Case C using sliding mode control (SMC). Cases B and C were predicted to improve the maximum meander amount by up to 12% compared to Case A, which does not compensate for transport time. In fact, meandering corrections using cases A, B, and C were carried out on a strip threading line consisting of the equipment shown in Figure 1. As with the above simulation, the meandering control method of the present invention, which takes transport time into consideration, improved the maximum meandering amount by up to 12% compared to a meandering control method that does not take transport time into consideration.

[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 between the steering roll and the roll that is used as the reference for the meandering amount is far. [Explanation of symbols]

[0044] M1 First meandering amount detector M2 Second meandering amount detector 1. First meander detector 2. Second meander detector 3 Steering Roll 4 Tilt device 41 Actuator 42 cylinders 6. First Control Section 7 Second control section 8 Reference Roles 9 Equipment 11 Line direction 12 Line Center

Claims

1. A meandering correction device for correcting meandering of a metal strip conveyed on a strip threading line, comprising: a first meandering amount detection unit disposed at a position where meandering control is to be performed on the metal strip, and configured to detect 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 meandering control target position in the strip threading line, the second meandering amount detection unit detecting a second meandering amount of the metal strip; a first control unit that corrects a shift amount of the meandering control target position based on the first meandering amount, taking into consideration at least one of a response delay of the tilting device and a response delay due to friction between the rolls of the strip threading line and the metal strip, as well as a transport time from the steering roll position to the meandering control target position; a second control unit that controls the width direction position of the metal strip by the steering roll based on the second meandering amount and the corrected shift amount; A metal strip meandering correction device comprising:

2. A method for correcting meandering of a metal strip being transported on a strip threading line using the metal strip meandering correction device described in claim 1, comprising: a step in which a first meandering amount detection unit detects a first meandering amount at a meandering control target position of the metal strip; a step of controlling the shift amount at the meandering control target position by tilting the steering roll with a tilting device; a second meandering amount detection unit 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; a first control unit correcting a shift amount of the meandering control target position based on the first meandering amount, taking into consideration at least one of a response delay of the tilting device and a response delay due to friction between the rolls of the strip threading line and the metal strip, as well as a transport time from the steering roll position to the meandering control target position; a second control unit controlling the width direction position of the metal strip by the steering roll based on the second meandering amount and the corrected shift amount; A method for correcting meandering of a metal strip, including:

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