Control system and control method

Abstract

To provide technology that improves control accuracy.SOLUTION: A control system includes: a first control device that performs FF control on a controlled object using a first control output obtained by multiplying a factor value of a fluctuation factor by a control gain; a second control device that calculates a second control output by multiplying the factor value by a control gain, calculates a third control output by integrating a deviation between an actual value and a target value of state quantity, and performs FF control using the second control output and integral control using the third control output on the controlled object; a selection device that selects which control device should perform control on the controlled object; an unobservable variation factor prediction device that calculates an estimated factor value from the state quantity; and a control device switching determination device that determines which control device to select based on the estimated factor value.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present disclosure relates to a technique for controlling a controlled object such as a plant.

Background Art

[0002] In plant control in which a plant is controlled as a controlled object, there are factors that cause a state quantity related to the plant to vary. When the state quantity of the plant varies due to such factors, the accuracy of the control result decreases.

[0003] For example, in a rolling mill, which is a plant for producing a thin metal material by rolling a material to be rolled, if there is uneven hardness in the material to be rolled, the uneven hardness may cause the thickness of the material to be rolled to vary depending on the position (thickness defect). Uneven hardness means that the hardness of the material to be rolled is not uniform. Since the hardness of the material to be rolled becomes the deformation resistance during rolling, if there is uneven hardness in the rolling direction in which the material to be rolled is conveyed during rolling, the way the material to be rolled is crushed will vary depending on the position, and the thickness after rolling will change depending on the position, resulting in thickness variation.

[0004] Also, in the production of metal materials by rolling, generally, in order to process the thickness of the material to be rolled from the original plate thickness to the desired product thickness, the material to be rolled is fed into the rolling mill multiple times. Therefore, if there is uneven hardness in the material to be rolled, thickness variation will occur each time it is fed into the rolling mill.

[0005] Patent documents 1 to 3 disclose techniques for suppressing plate thickness fluctuations that occur in tandem rolling mills including multiple rolling mills. The techniques described in patent documents 1 to 3 suppress plate thickness fluctuations by detecting plate thickness fluctuations generated by the preceding rolling mill and performing feedforward control to control the subsequent rolling mill based on those plate thickness fluctuations. In such feedforward control, the control gain of the feedforward control is adjusted according to the plate thickness fluctuations caused by the preceding rolling mill. Furthermore, the technique described in patent document 3 adjusts the control output timing in addition to the control gain when there is a large deviation between a state variable such as plate thickness and a target value. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 3384330 [Patent Document 2] Patent No. 5581964 [Patent Document 3] Patent No. 6404195 [Patent Document 4] Japanese Patent Publication No. 2021-081772 [Overview of the project] [Problems that the invention aims to solve]

[0007] In general, plant control systems that control a controlled plant may employ feedback control to suppress long-term offset errors (the difference between the state variable and the command value) in state variables, in addition to feedforward control to suppress short-period state variable fluctuations such as plate thickness fluctuations.

[0008] Feedback control includes integral control, which uses a control output obtained by integrating state variables. However, integral control results in a 90-degree phase shift between the state variable fluctuation and the control output. Therefore, when both feedforward control and feedback control are performed, the phase shift caused by feedback control can cause the timing of the feedforward control output to deviate from an appropriate value, reducing the control effect of the feedforward control and potentially lowering the control accuracy. Patent documents 1 to 3 do not disclose anything regarding how feedback control can suppress the reduction in the control effect of feedforward control.

[0009] On the other hand, Patent Document 4 proposes a technique for reducing offset errors while suppressing the reduction in the control effect of feedforward control. However, even with the technique described in Patent Document 4, sufficient control accuracy is not always achieved, and further improvement in control accuracy is desired.

[0010] The purpose of this disclosure is to provide a technology for improving the accuracy of control. [Means for solving the problem]

[0011] A control system according to one aspect of the present disclosure is a control system that outputs a control output to a control object having a state variable, performing predetermined control and obtaining a control result, and comprises: a first control device that calculates a first control output by multiplying a factor value, which is a value relating to a fluctuation factor that causes the control result to fluctuate, by a control gain, and performs feedforward control on the control object using the first control output; a second control device that calculates a second control output by multiplying the factor value by a control gain, calculates a third control output by integrating the deviation between the actual value and the target value of the state variable, and performs feedforward control using the second control output and integral control using the third control output on the control object; a selection device that selects whether to have the first control device or the second control device perform control on the control object; an unobservable fluctuation factor prediction device that calculates an estimated factor value by predicting the factor value from the state variable; and a control device switching determination device that determines whether to select the first control device or the second control device based on the estimated factor value and instructs the selection device on the determination result. [Effects of the Invention]

[0012] According to one aspect of this disclosure, the accuracy of the control is improved. [Brief explanation of the drawing]

[0013] [Figure 1] This figure shows an example of a controlled plant according to this embodiment. [Figure 2] This is a diagram to explain the rolling phenomenon. [Figure 3] This figure shows a model representing the rolling phenomenon explained in Figure 2. [Figure 4] This is a diagram illustrating an example of plate thickness control. [Figure 5] This is a diagram illustrating an example of tension control. [Figure 6] This diagram illustrates the phase difference between the controlled state variable and the control result under integral control. [Figure 7] This diagram illustrates the phase difference between the controlled state variable and the control result under integral control. [Figure 8] This diagram illustrates the phase difference between the controlled state variable and the control result under integral control. [Figure 9] This diagram illustrates the effect of feedforward control on the controlled state variables. [Figure 10] This figure shows the relationship between the control result, the control gain, and the phase shift amount. [Figure 11] This is a schematic block diagram of the plant control system according to this embodiment. [Figure 12] This is a block diagram of the control device 2. [Figure 13] This figure shows an example of the control results of the control device 2 obtained through simulation. [Figure 14] This figure shows a state where the waveform, which represents the change in the deviation of the state variable's actual performance, is biased in the positive direction. [Figure 15] This figure shows an example of the offset removal result of the control device 2 obtained through simulation. [Figure 16] This is a block diagram of control device 1. [Figure 17] This figure shows an example of an FF control device. [Figure 18] This is a diagram to explain the principle of offset correction. [Figure 19] This is a diagram showing an example of an offset correction device. [Figure 20] This figure shows an example of the control results of the control device 1 obtained through simulation. [Figure 21] This figure shows an example of the control results of the control device 1 obtained through simulation. [Figure 22] This is a diagram illustrating the plant control system. [Figure 23] This diagram shows a configuration for evaluating hardness variations in rolled material. [Figure 24] This is a flowchart of the process for calculating the estimated deformation resistance. [Figure 25] This is a flowchart of the process for switching control devices. [Figure 26] This diagram illustrates the switching from control device 2 to control device 1. [Figure 27] This diagram shows the output of the control device 1. [Figure 28] This figure shows an example of a waveform that illustrates the deviation of state variables. [Modes for carrying out the invention]

[0014] Embodiments of this disclosure will be described below with reference to the drawings. Hereinafter, an example will be given of a configuration in which a plant to be controlled is controlled by a plant control system.

[0015] <<Controlled Plant>>

[0016] First, let me explain the plant that will be controlled.

[0017] Figure 1 shows an example of a controlled plant according to this embodiment.

[0018] Figure 1 shows a tandem rolling mill 100 equipped with multiple rolling mills for rolling the rolled material 200 as the controlled plant. The tandem rolling mill 100 shown in Figure 1 is a four-stand tandem rolling mill with four rolling mills 11-14 arranged in series, but the number of rolling mills is not limited to four.

[0019] Each rolling mill 11-14 is equipped with multiple rolls that hold the material to be rolled 200, and performs a rolling process by rolling the material using these rolls. In the example shown in the figure, each rolling mill 11-14 has a pair of work rolls 1 that directly hold the material to be rolled 200, a pair of intermediate rolls 2 positioned outside each work roll 1, and a pair of backup rolls 3 positioned outside each intermediate roll 2. The material to be rolled 200 is transported in the order of rolling mill 11, rolling mill 12, rolling mill 13, and rolling mill 14. Hereafter, rolling mill 11 may be referred to as #1 stand rolling mill 11, rolling mill 12 as #2 stand rolling mill 12, rolling mill 13 as #3 stand rolling mill 13, and rolling mill 14 as #4 stand rolling mill 14.

[0020] FIG. 2 is a diagram for explaining the rolling phenomenon occurring in the rolled material 200 by each of the rolling mills 11 to 14. As shown in FIG. 2, the rolling of the rolled material 200 is carried out by crushing the rolled material 200 with a pair of work rolls 1 sandwiching the rolled material 200. At this time, on the rolled material 200, an inlet side tension T acting toward the front stage side of the work roll 1 with respect to the rolling direction, which is the conveyance direction of the rolled material 200, b and an outlet side tension T acting toward the rear stage side of the work roll 1 f are applied. Further, a rolling load P determined according to the roll gap S, which is the distance between the work rolls 1, is applied to the rolled material 200 in the vertical direction. As a result, the rolled material 200 is rolled, and the plate thickness of the rolled material 200 changes from the inlet side plate thickness H to the outlet side plate thickness h. If the forward rate due to this rolling phenomenon is f and the backward rate is b, the inlet side speed V e and the outlet side speed V o of the rolled material 200 are such that when the work roll speed, which is the rotational speed of the work roll 1, is V R , V e = V R (1 + b), V o = V R (1 + f).

[0021] FIG. 3 is a diagram showing a model representing the rolling phenomenon described in FIG. 2. The inlet side tension T b and the outlet side tension T f applied to the rolled material 200 in the rolling mill change according to the inlet side speed V e and the outlet side speed V o of the rolling mill itself and the rolling mills before and after it. Further, when the tension changes, the rolling load P, the outlet side plate thickness h, the inlet side speed V e and the outlet side speed V o change. Therefore, the rolling phenomenon is a very complex phenomenon that takes the inlet side plate thickness H, the work roll speed V R and the roll gap S as inputs and the inlet side tension T b , the outlet side tension T f and the outlet side plate thickness h as outputs. Furthermore, since it is also related to the rolling phenomena in the rolling mills before and after via the tension, it is extremely complex.

[0022] Returning to the explanation of Figure 1, each rolling mill 11-14 is equipped with drive devices 21-24 for driving the work rolls and roll gap control devices 31-34 for controlling the roll gap of the work rolls 1. The drive devices 21-24 include, for example, an electric motor (not shown) for driving the work rolls 1 and an electric motor speed control device (not shown) for operating the electric motor to control the speed of the work rolls.

[0023] Furthermore, each rolling mill 11-14 is equipped with a thickness gauge 40-44 for measuring the thickness of the rolled material 200 and a tension gauge 50-54 for measuring the tension applied to the rolled material 200. The thickness of the rolled material 200 is important from the perspective of the quality of the products produced by rolling the rolled material 200. The tension applied to the rolled material 200 is important for the stability of the rolling operation and is also related to the accuracy of the thickness.

[0024] Furthermore, an exit bridle roll 15 is provided at the exit side of the rolling mill 14 to generate exit tension. The exit bridle roll 15 is provided with a drive device 25. The drive device 25 includes, for example, an electric motor (not shown) that drives the exit bridle roll 15 and an electric motor speed control device (not shown) that operates the electric motor to control the rotational speed of the exit bridle roll 15.

[0025] Furthermore, each rolling mill 11 to 14 is equipped with a plate thickness control device 61 to 64 and a tension control device 71 to 74 as a plant control device for controlling the rolling process.

[0026] The plate thickness control device 61, which corresponds to the rolling mill 11, controls the exit plate thickness of the rolling mill 11 by controlling the roll gap of the rolling mill 11 using the roll gap control device 31. The plate thickness control devices 62 to 64, which correspond to the rolling mills 12 to 14, control the exit plate thickness of each rolling mill 12 to 14 by controlling the preceding stand speed, which is the working roll speed of the preceding rolling mills 11 to 13, using the drive devices 21 to 23 of the preceding rolling mills 11 to 13.

[0027] The plate thickness control devices 62-64 perform feedforward control using the detection results of the plate thickness gauges 41-43 on the input side of the corresponding rolling mills 12-14 (plate thickness gauges on the output side of the preceding rolling mills 11-13), and feedback control using the detection results of the plate thickness gauges 42-44 on the output side of the corresponding rolling mills 12-14. For example, in the case of plate thickness control device 62, feedforward control using the detection result of plate thickness gauge 41 and feedback control using the detection result of plate thickness gauge 42 on the output side are performed.

[0028] Furthermore, tension control devices 71 to 73 control the exit tension of the corresponding rolling mills 11 to 13 by controlling the roll gap of the subsequent rolling mills 12 to 14 using roll gap control devices 32 to 34, based on the detection results of the exit tension gauges 51 to 53 of the corresponding rolling mills 11 to 13. For example, in the case of tension control device 71, the roll gap of rolling mill 12 is controlled based on the detection result of the exit tension gauge 51 of rolling mill 11. Also, tension control device 74 controls the exit tension of rolling mill 14 by controlling the rotational speed of the exit bridle roll 15 using the drive device 25, based on the detection result of the exit tension gauge 54 of the corresponding rolling mill 14.

[0029] Next, the plate thickness control performed by the plate thickness control devices 61-64 will be explained in more detail. In plate thickness control, the rolling mill where the plate thickness changes and the plate thickness gauge that detects the plate thickness are physically separated. Therefore, there is a delay between the detection of the deviation in the plate thickness at the entry side of the rolled material 200 and the time it takes for that point to reach the rolling mill where the actual control operation is performed. There is also a delay before the plate thickness changed in the rolling mill is detected by the plate thickness gauge at the exit side.

[0030] Figure 4 is a diagram illustrating an example of plate thickness control, showing an example configuration of a plate thickness control device 64 corresponding to the #4 stand rolling mill 14. In the example in Figure 4, the plate thickness gauge 43 measures and outputs the deviation between the exit plate thickness of the #3 stand rolling mill 13 and the target value as the entry plate thickness deviation ΔH, and the plate thickness gauge 44 measures and outputs the deviation between the exit plate thickness of the rolling mill 14 and the target value as the exit plate thickness deviation Δh. Each target value is predetermined.

[0031] The plate thickness control device 64 includes a transfer time compensation unit 201 that corrects the wasted time from the input plate thickness gauge to the rolling mill, a feedforward control unit 202, a proportional circuit 203, and an integral circuit 204.

[0032] The transfer time compensation unit 201 calculates the input thickness deviation ΔH output from the output thickness gauge 43 of the #3 stand rolling mill 13 by a phase shift amount T FF A transfer process is performed that shifts the phase by a certain amount T. FF is the transfer time T X3D-4 and the timing shift amount of the feedforward control output (hereinafter abbreviated as timing shift amount) ΔT FF Using T FF =T X3D-4 -ΔT FF It is represented by the transfer time T. X3D-4 This is the time it takes for the point in the rolled material 200 having an entry-side thickness deviation ΔH to move from the thickness gauge 43 to directly below the work roll 1 of the rolling mill 14. Timing shift amount ΔT FF This is determined according to the dead time until the control output 230 corresponding to the input plate thickness deviation ΔH reaches the drive unit 23, and the response time from when the control output 230 is input to the drive unit 23 until it responds.

[0033] The feedforward control unit 202 controls the input plate thickness deviation ΔH, which has been processed by the transfer time compensation unit 201, by applying a control gain G FF Multiply by this to generate the feedforward control output 210.

[0034] The proportional circuit 203 and the integrating circuit 204 constitute a feedback control unit that performs feedback control. The proportional circuit 203 controls the output thickness deviation Δh measured by the output thickness gauge 44 of the rolling mill 14 with a control gain G FB The output is obtained by multiplying by the value. The integrating circuit 204 performs integration on the output of the proportional circuit 203 to generate the feedback control output 220. Here, the control gain G FB This is determined by taking into account the dead time from the rolling mill to the thickness gauge at the exit.

[0035] The feedforward control output 210 and the feedback control output 220 are added together and input to the drive unit 23 of the rolling mill 13 as the control output 230 of the plate thickness control device 64.

[0036] Next, tension control by tension control devices 71-74 will be explained in more detail. Since the tension meter directly detects the tension applied to the rolled material, there is no need to consider dead time. Therefore, basically only feedback control is implemented. Figure 5 is a diagram illustrating an example of tension control, and shows an example configuration of the tension control device 73 corresponding to the #3 stand rolling mill 13.

[0037] In the example shown in Figure 5, the tension control device 73 has a proportional-integral unit 301. The proportional-integral unit 301 controls the actual tension value T, which is the tension measured by the tension meter 53 located on the exit side of the rolling mill 13. 34FB The tension command value T input from an external source. 34REF The deviation ΔT 34 The rolling mill 14 is controlled proportionally and integrally using the following. Specifically, the proportional-integral unit 301 controls the deviation ΔT 34 A proportional-integral process is performed on this to generate the control output 310 of the tension control device 73, which is then input to the roll gap control device 34 of the rolling mill 14. Note that proportional-integral control is a control method that combines proportional control and integral control, and here the proportional gain of the proportional control is C P The integral gain of the integral control is defined as C1.

[0038] As described above, the plate thickness control performed in the tandem rolling mill 100 is a combination of feedforward control, which is proportional control, and feedback control, which is integral control. Furthermore, tension control is configured as feedback control using proportional-integral control.

[0039] Generally, in integral control of a control state variable, the phase of the control output is shifted by 90 degrees relative to the phase of the control state variable. As a result, the phase of the control result obtained by integral control is shifted from the phase of the original control state variable. For example, in a tandem rolling mill 100, the phase of the exit plate thickness (plate thickness deviation) of the rolling mill 14, which is the control result, is shifted from the phase of the original deformation resistance (hardness).

[0040] Figures 6 to 8 are diagrams used to explain the phase difference between the control state variables and the control results due to integral control, and show the simulation results of the rolling phenomenon in the tandem rolling mill 100. Figures 6 to 8 show the simulation results of the fluctuations of the #4 stand entry side plate thickness deviation 410, the #4 stand exit side plate thickness deviation 420, the tension between the #3 stand and the #4 stand 430, the #4 stand exit side tension 440, and the #4 stand load 450, when the fluctuation of the deformation resistance 400 in the rolling direction of the rolled material 200 is represented as a sine wave.

[0041] Furthermore, the #4 stand entry-side plate thickness deviation 410 is the deviation between the plate thickness on the entry side of the #4 stand rolling mill 14 and the target value, the #4 stand exit-side plate thickness deviation 420 is the deviation between the plate thickness on the exit side of the #4 stand rolling mill 14 and the target value, the #3 stand to #4 stand tension 430 is the tension on the entry side of the #4 stand rolling mill 14, the #4 stand exit-side tension 440 is the tension on the exit side of the #4 stand rolling mill 14, and the #4 stand load 450 is the load applied to the rolled material 200 by the #4 stand rolling mill 14.

[0042] Figure 6 shows the simulation results when neither plate thickness control nor tension control is performed. In the example in Figure 6, the peak positions of the waveforms showing the fluctuations of the original control state variable, deformation resistance 400, and the plate thickness deviation 410 on the #4 stand entry side and plate thickness deviation 420 on the #4 stand exit side coincide, indicating that there is no phase difference between them.

[0043] Figures 7 and 8 show the simulation results when both tension control by tension control devices 73 and 74 and plate thickness control by plate thickness control device 64 are implemented. However, Figure 7 shows the case when only feedback control is implemented as plate thickness control (feedforward control gain G FF Figure 8 shows the simulation results when (where is set to 0), and Figure 8 shows the simulation results when both feedback control and feedforward control are implemented for plate thickness control.

[0044] In the example shown in Figure 7, where feedforward control is not implemented for plate thickness control, there is no phase difference between the deformation resistance 400 and the plate thickness deviation 410 on the #4 stand entry side. However, the control result, the plate thickness deviation 420 on the #4 stand exit side, exhibits a phase lead, meaning its phase is earlier than that of the deformation resistance 400. This is because the implementation of integral control for plate thickness control causes a 90-degree phase lag in the control output of the plate thickness control. As shown in Figures 9 to 10 and equations (1) to (3) described later, if there is a phase lag in the control output (i.e., the phase shift amount (Δ) due to the control output is negative), the phase shift amount (δ) of the control result, the plate thickness deviation 420 on the #4 stand exit side, becomes positive, resulting in a phase lead.

[0045] Therefore, by performing control such as plate thickness control, the phase relationship between the state variables of the controlled object (in the case of the tandem rolling mill 100, the plate thickness of the rolled material 200, the tension applied to the rolled material 200, and the rolling load) changes.

[0046] Furthermore, in the example shown in Figure 8 where feedforward control is implemented for plate thickness control, a phase lead occurs in the plate thickness deviation 410 on the #4 stand entry side, which is ahead of the deformation resistance 400. Therefore, when feedforward control of the plate thickness deviation 420 on the #4 stand exit side is implemented using the plate thickness deviation 410 on the #4 stand entry side, the phase difference between the deformation resistance 400 and the plate thickness deviation 410 on the #4 stand entry side prevents appropriate control according to the deformation resistance 400, resulting in a reduced control effect.

[0047] Therefore, when implementing feedforward control, the control gain G in feedforward control is as shown in Figure 4. FF and phase shift amount T FF (Specifically, timing shift amount ΔT FF By adjusting these parameters, a feedforward control output is generated that matches the phase and amplitude of the controlled state variable, thereby increasing the control effect.

[0048] Figure 9 illustrates the effect of feedforward control on a controlled state variable. In Figure 9, the control deviation, which is the difference between the controlled state variable and the target value, is taken as input, and it is assumed that the fluctuation of this control deviation is represented by a sine wave sin(ωt). Furthermore, the difference between the control deviation and the feedforward control output, to which a phase shift and control gain have been applied, is output as the control result y. If the phase shift amount is Δ and the control gain is G, the control result y is expressed by the following equation (1).

[0049]

number

[0050] Here, the amplitude X of the control result y is expressed by equation (2) below, and the phase shift amount δ from the control deviation of the control result y is expressed by equation (3) below.

[0051]

number

[0052]

number

[0053] Figure 10 shows the relationship between the control result y, the control gain G, and the phase shift amount Δ. Specifically, Figure 10(a) shows the relationship between the phase shift amount Δ and the phase shift amount δ of the control result y for each control gain G, and Figure 10(b) shows the relationship between the phase shift amount Δ and the amplitude X of the control result y for each control gain G.

[0054] As shown in Figure 10, as the phase shift amount Δ increases, the amplitude X also increases, reducing the control effect. Furthermore, depending on the control gain G, if the phase shift amount Δ exceeds 60 degrees, the amplitude X exceeds 1. In other words, not only is no control effect obtained, but it also has a counterproductive effect. In addition, the phase of the control result y deviates from the original sine wave sin(ωt) depending on the phase shift amount Δ.

[0055] Therefore, in feedforward control, the control gain G (control gain G FF ) and phase shift amount Δ(timing shift amount ΔT FF ) and need to be adjusted to appropriate values. These appropriate values ​​vary depending on the parameters related to the controlled object and other controls performed on the controlled object. In the case of a tandem rolling mill 100, the parameters related to the controlled object include the rolling speed at which the rolled material 200 is rolled. When the rolling speed changes, the fluctuation frequency of the plate thickness deviation changes, and the response time of the drive unit 23, which is the control operation end of the control output, changes. Other controls include plate thickness control performed on other rolling mills.

[0056] However, in cases where both feedforward control and feedback control are implemented, such as in the tandem rolling mill 100, the phase of the control state variable changes due to the feedback control, which is an integral control, making it difficult to adjust the control gain and phase shift amount in the feedforward control to appropriate values.

[0057] <<Plant Control System>>

[0058] <System Overview>

[0059] Figure 11 is a schematic block diagram of the plant control system of this embodiment.

[0060] Referring to Figure 11, the plant control system of this embodiment includes an unobservable disturbance prediction device 604, a control device switching determination device 926, a control correction device 925, and a plant control device 900. The plant control device 900 includes a control device 1 601, a selection device 902, and a control device 2 901. The controlled plant 600 in Figure 11 is the tandem rolling mill 100 shown in Figure 1. The plant control system is a control system that outputs a control output to the controlled plant. In the rolling of the rolled material 200 by the rolling mill, variations in the hardness of the rolled material 200 become a disturbance dACT and are a factor that causes fluctuations in the plate thickness, which is the control result. Hardness variations refer to variations in hardness at different points in the rolled material 200.

[0061] The control device 1 601 calculates a first control output by multiplying a factor value, which is the value of a variable factor that causes the control result to change, by a control gain, and uses the first control output to perform feedforward control on the controlled plant 600.

[0062] The control device 2901 calculates a second control output by multiplying the factor value of the fluctuating factor by the control gain, and calculates a third control output by integrating the deviation between the actual value and the target value of a predetermined state variable. The control device performs feedforward control using the second control output and integral control using the third control output on the controlled plant 600.

[0063] The selection device 902 is a device that selects whether control device 1 601 or control device 2 901 will perform the control of the plant 600 to be controlled.

[0064] The unobservable disturbance prediction device 604 calculates an estimated factor value by predicting the factor value from at least one of the state variables and control results, and inputs the estimated factor value to the control device 1 601.

[0065] The control device switching determination device 926 determines whether to select control device 1 601 or control device 2 901 based on the estimated factor values, and instructs the selection device 902 of the determination result.

[0066] In this embodiment, the controlled plant consists of multiple control processes (stands) arranged in a sequence from upstream to downstream. The unobservable disturbance prediction device 604 inputs estimated factor values ​​calculated from state variables in the upstream processes to the control devices in the downstream processes. The control device switching determination device 926 then uses the estimated factor values ​​from the upstream processes to determine whether to use control device 1 601 or control device 2 901 in the downstream processes.

[0067] According to the plant control system of this embodiment, it becomes possible to control the target plant 600 using an appropriate control device.

[0068] The above is an overview of the plant control system; further details will be provided later.

[0069] <Control device 2>

[0070] The control device 2901 described above is a control device that performs both feedforward control and feedback control.

[0071] Figure 12 is a block diagram showing two examples of the control device 2901.

[0072] Figure 12(a) shows the controlled plant 600, the control device 2901 that controls the controlled plant 600, and the phase shift factor 602 that shifts the state quantity actual xFB, which is the state quantity of the controlled object output from the controlled plant 600, by the amount of detection dead time. The control device 2901 also includes a PI control device 511 that performs proportional-integral control on the controlled plant 600 based on the deviation between the state quantity actual xFB and the state quantity command value xREF, which is the command value of the state quantity input from an external source.

[0073] The controlled plant 600 is, for example, a tandem rolling mill 100, and outputs a state quantity actual xFB related to the controlled plant. A phase shift occurs in the state quantity actual xFB due to a phase shift factor 602. The phase shift factor 602 is, for example, that the location where the controlled plant 600 performs processing on the material and the location where the state quantity actual xFB, which is the result of that processing, is detected are physically separated. In Figure 11, the phase shift factor 602 is shown to be located outside the controlled plant 600, but it may also be located inside the controlled plant 600.

[0074] Furthermore, the controlled plant 600 is affected by the controlled disturbance dACT, which is a disturbance to the controlled plant 600 generated by the controlled disturbance source 603. Therefore, the controlled disturbance dACT becomes a factor that causes the state variable actual xFB to change. The controlled disturbance dACT is known. In this case, it is sufficient that a statistical value such as the mean value of the controlled disturbance dACT is known.

[0075] The actual state variable xFB has an offset error due to modeling errors and disturbances in the controlled plant 600. The integral control included in the proportional-integral control by the PI control device 511 is a control that corrects the offset error of the actual state variable xFB and maintains the actual state variable xFB at the state variable command value xREF.

[0076] The example in Figure 12(b) differs from the example in Figure 12(a) in that the control device 2901 includes an I control device 521 that performs integral control (feedback control) on the controlled plant 600 and an FF control device 522 that performs feedforward control on the controlled plant 600, instead of the PI control device 511.

[0077] The plant control system shown in Figure 12(b) corresponds to the plate thickness control in the rolling mill. Compared with Figure 4, the disturbance source 603 corresponds to the plate thickness deviation at the entry side of the rolling mill, which is detected by the entry side plate thickness gauge 43 and becomes the control disturbance dACT. The FF control device 522 corresponds to the transfer time compensation unit 201 and the feedforward control unit 202, and the I control device 521 corresponds to the proportional circuit 203 and the integrating circuit 204.

[0078] In the example shown in Figure 12(b), the controlled disturbance dACT, which is a disturbance to the controlled plant 600 generated by the controlled disturbance source 603, is known. When the controlled disturbance dACT is known in this way, the FF control device 522 performs feedforward control on the controlled plant 600 based on the deviation between the controlled disturbance dACT and the disturbance command value dREF for the controlled disturbance dACT. In addition, the I control device 521 performs integral control on the controlled plant 600 based on the deviation between the actual state variable xFB and the state variable command value xREF.

[0079] The detection delay occurs because the location where the controlled plant 600 performs processing on the material and the location where the results of that processing are detected are physically separated. In the case of the tandem rolling mill 100, as shown in Figure 2, the rolling mills 11-14 where the rolled material 200 is processed by rolling and the thickness gauges 41-44 that detect the thickness of the rolled material 200 are physically separated. The rolled material 200 is transported from the rolling mills 11-14 to the thickness gauges 41-44, and the processing result (thickness) of the rolled material 200 is detected. The time required for this transport of the rolled material 200 becomes the detection delay.

[0080] Thus, in the control device 2901, feedback control including integral control is implemented to eliminate offset errors caused by disturbances and the like. This integral control is a control that generates a phase delay in the control output that is the sum of a 90-degree phase delay from the control state variable and a phase delay due to detection dead time. If the control output becomes large due to a large disturbance, it interferes with the control output of the feedforward control, and the phase shift amount of the feedforward control deviates from the set value. As a result, the control effect of the feedforward control is reduced.

[0081] Figure 13 shows an example of the control result of the control device 2901 obtained through simulation. Figure 13 shows the time evolution of the control disturbance dACT and the control result, which is the actual state variable xFB (specifically, the deviation between the actual state variable xFB and the commanded state variable xREF).

[0082] Figure 13(a) shows the simulation results when only integral control is performed without feedforward control, using the configuration example shown in Figure 12(b). The detection delay time is set to 0.25 seconds, and the time constant for integral control is set to 0.5 seconds. Furthermore, the control disturbance dACT is assumed to fluctuate in a step-like manner. In this case, the actual state variable xFB shows a very small undershoot, indicating that there are no problems with integral control.

[0083] Figure 13(b) shows the simulation results when only feedforward control is performed without integral control, in the configuration example shown in Figure 12(b). The control disturbance dACT was assumed to fluctuate sinusoidally with a period of 1.0 Hz and an amplitude of 1.0. The control gain for feedforward control was set to 0.5. In this case, the control disturbance dACT is suppressed by the feedforward control, and the amplitude of the state variable actual xFB is 0.5.

[0084] Figure 13(c) shows the simulation results when the same integral control as in Figure 13(a) is further applied in the situation shown in Figure 13(b). In this case, the amplitude of the state variable actual xFB becomes 0.7, which is larger than when integral control is not applied. In other words, it can be said that the control effect of feedforward control is reduced by integral control.

[0085] In the case of the tandem rolling mill 100, the detection delay of 0.25 seconds corresponds to a rolling speed of 10 m / s = 600 mpm for the rolled material 200, assuming a distance of 2.5 m between the rolling mill and the thickness gauge. Furthermore, the period of the control disturbance dACT, 1.0 Hz, corresponds to a period of 10 m when converted to the length of the rolled material 200. This can be considered a disturbance from a rotating body with a diameter of approximately 1.6 m. Moreover, a diameter of approximately 1.6 m is about the diameter of the rolling mill's backup rolls. For this reason, the simulation conditions in Figures 13(b) and 13(c) are reasonable.

[0086] Furthermore, integral control is a control method that removes the offset and sets the average of the deviations of the state variables to zero. Therefore, depending on the waveform that shows the change in the deviation of the original control state variable, the waveform that shows the change in the deviation of the state variable after removing the offset may be biased upwards or downwards under integral control.

[0087] Figure 14 shows a state where the waveform indicating the change in the deviation of the state variable performance is biased towards the positive direction (upward), that is, the absolute value of the positive peak value is smaller than the absolute value of the negative peak value. In this case, as will be described later, the state variable performance may exceed the acceptable range in the positive peak value portion, which can lead to product defects. Note that fluctuations in the change resistance of the rolled material 200 often appear as a waveform like the one shown in Figure 14(a).

[0088] Figure 15 shows an example of the offset removal result of the control device 2901 obtained by simulation. In Figure 15, the time evolution of the control disturbance dACT and the control result, the state variable actual xFB (specifically, the deviation between the state variable actual xFB and the state variable command value xREF), is shown. The fluctuation of the control disturbance dACT was assumed to be a square wave fluctuation.

[0089] Figure 15(a) shows the control result when only integral control is performed in the configuration example shown in Figure 12(b), where the time ratio of the time when the control disturbance dACT is positive to negative is 50:50. In this example, as a result of integral control, the magnitudes of the positive peak value and the negative peak value of the state variable actual xFB are equal.

[0090] Figure 15(b) shows the control result when only integral control is performed, with the above time ratio being positive:negative = 30:70. In this example, the positive peak value of the state variable actual xFB is greater than the negative peak value, resulting in a state where the state variable actual xFB is biased in the positive direction.

[0091] The state variables of products produced in a controlled plant typically have tolerance ranges determined according to product specifications, and within these tolerance ranges, the tolerance range in the positive direction from the target value and the tolerance range in the negative direction from the target value are considered to be equal. In this case, as shown in Figure 14(a), if the deviation of the state variable results in a waveform that is biased in the positive direction, the state variable may exceed the upper limit of the tolerance, potentially leading to product defects.

[0092] In contrast, even with waveforms of similar amplitude, by removing the offset and adjusting the state variables so that the maximum and minimum values ​​of the state variables fall within the acceptable range, and by matching the median value to the command value, as shown in Figure 14(b), it is possible to prevent product defects.

[0093] As explained above, when both feedforward control and feedback control (integral control) are performed in the control device 2901, the phase of the control output of the feedforward control is shifted due to the feedback control (integral control), reducing the control effect of the feedforward control. In addition, with feedback control (integral control), the waveform showing the change in the deviation of the state variable actuals may be biased in the positive or negative direction, causing the state variable actuals to fall outside the acceptable range.

[0094] <Control device 1>

[0095] Figure 16 is a block diagram of the control device 1601. The control device 1601 shown in Figure 16 controls the controlled plant 600.

[0096] The control device 1 601 includes an FF control device 611 and an offset correction device 612.

[0097] The FF control device 611 performs feedforward control of the processing operations performed by the controlled plant 600 (for example, rolling operations by the rolling mills 11-14) based on the disturbance deviation, which is the difference between the control disturbance dACT and the disturbance command value dREF. Specifically, the FF control device 611 performs feedforward control of the processing operations performed by the controlled plant 600 using a control output obtained by multiplying the disturbance deviation by a correction gain. The disturbance deviation is a factor value related to the control disturbance dACT, which is a variable that causes the state variable actual xFB to change.

[0098] The offset correction device 612 corrects the offset that occurs in the controlled state variables of the controlled plant 600 through feedforward control by the FF control device 611.

[0099] Figure 17 shows an example of an FF control device 611. In Figure 17, the FF control device 611 includes a difference circuit 701, a positive filter circuit 702, a negative filter circuit 703, multipliers 704 to 707, and an integrating circuit 708.

[0100] The difference circuit 701 outputs the difference in disturbance deviation, which is the deviation between the controlled disturbance dACT and the disturbance command value dREF. Specifically, the difference circuit 701 has a delay circuit 711 that delays the disturbance deviation by a unit of time (for example, the period if the controlled disturbance dACT changes periodically), and outputs the value obtained by subtracting the signal delayed by the delay circuit 711 from the original disturbance deviation as the difference in disturbance deviation.

[0101] The positive filter circuit 702 outputs the difference when the difference output from the difference circuit 701 has a positive value. The negative filter circuit 703 outputs the difference when the difference output from the difference circuit 701 has a negative value.

[0102] Multiplier 704 multiplies the difference output from the positive filter circuit 702 by the positive correction gain G+ as a correction gain and outputs it. Multiplier 705 multiplies the difference output from the negative filter circuit 703 by the negative correction gain G- as a correction gain and outputs it. Multiplier 706 multiplies the sum of the output signals from multiplier 704 and multiplier 705 by the control suppression gain Gpre and outputs it. Multiplier 707 multiplies the output signal from multiplier 706 by the control gain GFF and outputs it.

[0103] The integrating circuit 708 integrates the output signal from the multiplier 707 to produce a feedforward control output S. FFNEW Output as follows.

[0104] In the above operation, the positive correction gain G+ and the negative correction gain G- are calculated by the offset correction device 612 and set in the multipliers 704 and 705. By appropriately setting the positive correction gain G+ and the negative correction gain G-, it becomes possible to correct the offset that occurs in the state variables. The control suppression gain Gpre is calculated by the control correction device 925 and set in the multiplier 706.

[0105] Figure 18 is a diagram illustrating the principle of offset correction. Figure 18 shows the result of changing the control gain of the FF control device 522 in the response (control result) shown in Figure 13(b) when the time change of the state variable actual xFB is positive. As shown in the lower part of Figure 18, the control gain (G) is set to positive in the first region A, and to negative in the second region B.

[0106] As shown in the upper part of Figure 18, in the first region A, the actual state variable xFB increases, and then the actual state variable xFB is offset on the positive side. In the second region B, the actual state variable xFB decreases, and then the actual state variable xFB is offset on the negative side.

[0107] In this feedforward control, by changing the control gain depending on whether the time evolution of the state variable actual xFB is positive or negative, the offset position can be adjusted without changing the position where the waveform of the state variable actual xFB peaks, that is, without changing the phase of the state variable actual xFB.

[0108] Using the above principle, the offset correction device 612 calculates the offset amount based on the actual state variable xFB, and calculates the positive correction gain G+ and negative correction gain G- to suppress the offset amount, so that the midpoint (median) between the maximum and minimum amplitudes of the actual state variable xFB becomes zero.

[0109] Figure 19 shows an example of an offset correction device 612. The offset correction device 612 shown in Figure 19 includes a state quantity offset measuring device 801 and a correction gain calculation device 802.

[0110] The state variable offset measuring device 801 measures the maximum value x, which is the positive peak value of the deviation between the actual state variable xFB and the target value, the state variable command value xREF, over a certain period (for example, one period of the controlled disturbance dACT). + And the minimum value x is the negative peak value. - The state variable offset measuring device 801 determines its maximum value x. + and minimum value x - Based on this, the median (maximum value x) of the state variable actual xFB. + and minimum value x - The bias Δx (midpoint) DIFF =x + ―|x - Calculate |.

[0111] The correction gain calculation device 802 calculates the bias Δx of the median value calculated by the state quantity offset measuring device 801. DIFF And the amplitude Δd of the controlled disturbance dACT ACT Based on this, the positive side correction gain G+ and the negative side correction gain G- are calculated.

[0112] Specifically, the correction gain calculation device 802 first calculates the amplitude Δd of the control disturbance dACT. ACT The bias of the median Δx DIFF If the conversion gain for this transformation is β, then the change in the correction gain α is given by α = |Δx DIFF | / |β·Δd ACT It is calculated from |. Note that since feedforward control is a control for known control disturbances, it is possible to calculate the amplitude of the control disturbance in advance, and the relationship between the control disturbance dACT and the state variable can also be predicted. Therefore, it is possible to calculate the conversion gain β in advance.

[0113] Next, the correction gain calculation unit 802 calculates the positive correction gain G+ and the negative correction gain G- based on the change amount α.

[0114] Specifically, the bias Δx DIFF If the result is positive, the correction gain calculation device 802 increases the positive correction gain G+ to more than 1 and the negative correction gain G- to less than 1, in order to suppress the control output in the positive direction and increase the control output in the negative direction. Specifically, the correction gain calculation device 802 sets the positive correction gain G+ = 1 - α and the negative correction gain G- to G- = 1 + α.

[0115] On the other hand, bias Δx DIFF If the result is negative, the correction gain calculation device 802 increases the control output in the positive direction and suppresses the control output in the negative direction by making the positive correction gain G+ less than 1 and the negative correction gain G- greater than 1. Specifically, the correction gain calculation device 802 sets the positive correction gain G+ = 1 + α and the negative correction gain G- = 1 - α.

[0116] The positive correction gain G+ and negative correction gain G- calculated by the correction gain calculation device 802 are output to the FF control device 611 and set in the multipliers 704 and 705.

[0117] Figures 20 and 21 show examples of control results for the control device 1601 obtained through simulation. Figures 20 and 21 show the control disturbance dACT and the actual state variable xFB (specifically, the deviation between the actual state variable xFB and the commanded state variable xREF).

[0118] Figure 20(a) shows the uncontrolled disturbance dACT and the actual state variable xFB when control is not performed by the control device 1601. Here, the actual state variable xFB is offset to the negative side with respect to the uncontrolled disturbance dACT up to 2.5 seconds, and then offset to the positive side thereafter.

[0119] Figure 20(b) shows the control disturbance dACT and the actual state variable xFB when only feedforward control by the control device 2901 shown in Figure 12(b) is performed. In this case, the amplitude of the actual state variable xFB decreases, but the offset of the actual state variable xFB remains.

[0120] Figure 21(a) shows the control disturbance dACT and the actual state variable xFB of the controlled object when both feedforward control and integral control are performed by the control device 2901 shown in Figure 12(b). In this case, the offset of the actual state variable xFB is reduced, but the amplitude of the actual state variable xFB increases.

[0121] Figure 21(b) shows the control disturbance dACT and the actual state variable xFB when control is performed by the control device 1601 shown in Figure 16. In this case, the amplitude and offset of the actual state variable xFB decrease, and furthermore, the positive peak value and the negative peak value of the actual state variable xFB become approximately the same.

[0122] When the upper limit tolerance for the state quantity performance is set to +0.5 and the lower limit tolerance is set to -0.5, in control device 2901, as shown by the arrow in Figure 21(a), the state quantity performance xFB exceeds the tolerance multiple times, but in control device 1601, as shown by the arrow in Figure 21(b), the state quantity performance xFB exceeds the tolerance only when the maximum value of state quantity performance xFB is reached x + and minimum value x -This occurred only once, before it was discovered. Therefore, the control device 1601 has a higher control effect compared to the control device 2901.

[0123] According to the control device 1 601, the FF control device 611 multiplies the disturbance deviation by a positive correction gain when the disturbance deviation is changing in the positive direction, increasing the state variable actual xFB, and by a negative correction gain when the disturbance deviation is changing in the negative direction, decreasing the state variable actual xFB. This makes it possible to correct the offset error without performing feedback control including integral control, and thus makes it possible to reduce the offset error while suppressing the reduction in the control effect of feedforward control, even when the disturbance is large.

[0124] Furthermore, according to the control device 1601, the offset correction device 612 adjusts the correction gain based on the median of the deviation between the actual state variable xFB and the target state variable command value xREF. This makes it possible to reduce the bias of the actual state variable xFB.

[0125] Furthermore, according to the control device 1601, when the median is positive, the positive correction gain is set to less than 1 and the negative correction gain is set to more than 1, and when the median is negative, the positive correction gain is set to more than 1 and the negative correction gain is set to less than 1. This makes it possible to appropriately reduce the bias of the actual state variable xFB.

[0126] Furthermore, according to this embodiment, the offset correction device 612 adjusts the correction gain so that the median value becomes zero. This makes it possible to more appropriately reduce the bias of the actual state variable xFB.

[0127] <Plant control equipment>

[0128] Figure 22 is a diagram illustrating the plant control system.

[0129] The plant control device 900 includes the control devices 1 601 and 2 901, which have already been described in detail, and a selection device 902.

[0130] Specifically, the control device 2901 performs feedforward control of the machining process performed by the controlled plant 600 using a control output obtained by multiplying the disturbance deviation by a control gain, and also performs integral control of the machining process performed by the controlled plant 600 using a control output obtained by integrating the deviation between the actual state variable xFB and the commanded state variable xREF.

[0131] Based on the disturbance deviation, the selection device 902 causes either the control device 1 601 or the control device 2 901 to execute control of the machining process performed by the controlled plant 600.

[0132] For example, if a control disturbance is very large compared to other disturbance frequency components, such as hardness unevenness in rolling, and the state variable results are difficult to keep within an acceptable range with control device 2 901, then control by control device 1 601 is preferable. However, if the state variable results can be sufficiently kept within an acceptable range with control device 2 901, then control by control device 2 901 may be used. In this embodiment, the selection device 902 selects either control device 1 601 or control device 2 901 based on at least one of the frequency and amplitude of the control disturbance, and executes control over the controlled plant 600. Details of the process of switching control devices will be described later.

[0133] <Unobservable disturbance forecast>

[0134] Figure 23 shows a configuration for evaluating hardness unevenness in the rolled material. In this embodiment, as shown in Figure 11, the hardness (deformation resistance) of each part of the rolled material 200 is calculated from data obtained in the rolling mill 11 in the upstream process.

[0135] The rolling load P in the rolling phenomenon occurring in the rolled material 200 shown in Figure 2 is expressed by the following equation (4).

[0136]

number

[0137] Thickness gauges 40 and 41 for measuring the thickness of the rolled material 200 and tension gauges 50 and 51 for measuring the tension applied to the rolled material are installed at the inlet and outlet of the rolling mill 11. A load cell 80 is also installed to measure the load applied to the rolled material 200 by the rolling mill 11.

[0138] The measured values ​​from the plate thickness gauge 40, tension gauges 50 and 51, and load cell 80 are transferred to the position of the plate thickness gauge 41, processed and calculated 903 and 904, and input into the calculated load calculation device 905 of the unobservable disturbance prediction device 604. The calculated load calculation device 905 uses equation (4) to calculate the load P expressed by the following equation (5) from the input rolling results. cal Calculate.

[0139]

number

[0140] Figure 24 is a flowchart of the process for calculating the estimated deformation resistance. This flowchart shows an example of a Newton-Raphson method program that uses a computational load Pcal to calculate the estimated deformation resistance k' using the estimated deformation resistance calculator 906 of the unobservable disturbance prediction device 604. The calculation process for the estimated deformation resistance k' will be explained below according to this flowchart.

[0141] When the program starts execution, it first sets the number of calculation trials i to 0 (907).

[0142] Next, the deformation resistance k is calculated as k0 and the load P cal Substitute (908). Using k0 from equation (4), calculate the load P cal Calculate (909). As a result, the calculated load P cal and actual load P act If the absolute value of k is less than the convergence criterion ε (YES at 910), then k i Output as the estimated deformation resistance k' (913), and if it is greater than the convergence criterion ε (NO at 910), ki+1 Calculate (911). Let i be the number of calculation trials i+1 (912), k i Using the calculated load P cal Calculate (909), and calculate the load P cal and actual load P act The calculation is repeated until the absolute value of k is smaller than the convergence criterion ε. i Output this as the estimated deformation resistance k' (913).

[0143] The estimated deformation resistance k' is input to the control correction device 925. The estimated deformation resistance k' may also be used in place of the known control disturbance dACT in the control device 1 601. For example, by using the estimated deformation resistance k' for each location on the rolled material 200 instead of the average value control disturbance dACT, the control device 1 601 can perform precise control for each location, improving the accuracy of the control.

[0144] <Automatic control system switching>

[0145] Figure 25 is a flowchart of the process for switching control devices. This flowchart shows the automatic switching method of the control device switching determination device 926 in the selection device 902, which automatically switches between control device 1 601 and control device 2 901 using the estimated deformation resistance k'. The process of the selection device 902 will be described below according to this flowchart.

[0146] For every 1 mm the rolled material 200 advances in the rolling direction, the estimated deformation resistance k' calculated by the estimated deformation resistance calculation device 906 is recorded in a tracking table having a memory area for every 1 mm distance (914).

[0147] Next, the judgment region L is defined as three times the length of the hardness unevenness occurrence period using the estimated deformation resistance k', and the fluctuation amount D is calculated by dividing the difference between the maximum value k'max and the minimum value k'min of the estimated deformation resistance k' recorded within the judgment region L by the average value k'ave of the judgment region L (915). The threshold a for automatic switching using the fluctuation amount D is set after verifying an appropriate switching criterion by conducting a simulation that generates fluctuations in deformation resistance in advance using control devices 1 601 and 2 901 (916). When the fluctuation amount D is greater than the threshold a (917 is YES), the control is switched to control device 2 901 (918), and when the fluctuation amount D is less than the threshold a (917 is NO), the control is switched to control device 1 601 (919).

[0148] Figure 26 is a diagram illustrating the switching from control device 2 901 to control device 1 601. An example is shown where the control device is switched to control device 1 601 by an automatic switching process performed by the selection device 902 based on the estimated deformation resistance k' output from the unobservable disturbance prediction device 604.

[0149] The estimated deformation resistance k' output from the unobservable disturbance prediction device 604 is recorded in the estimated deformation resistance table 920 for a certain period of time, the periodic component of the waveform is extracted, and used in the calculations of the control command maximum change rate simulation device 921, which pre-calculates the output amount of the control device 1 601 and calculates the maximum value of the rate of change, and the disturbance waveform control start point calculation device 922, which calculates the start timing of control by the control device 1 601 without offset. The control gain suppression device 923 of the control device 1 compares the maximum value of the rate of change calculated by the control command maximum change rate simulation device 921 with the maximum speed for controlling the controlled equipment and suppresses the control gain of the control device 1 601. The control input timing command device 924 outputs a command to the selection device 902 for the timing at which the control device 1 601 starts control, based on the control start timing calculated by the disturbance waveform control start point calculation device 922.

[0150] Figure 27 shows the calculated load P, expressed by equation (5), using the estimated deformation resistance k' of the estimated deformation resistance table 920. cal Calculate the calculated load P calThis figure shows the output quantity s(t) of the control device 1601, calculated by dividing by the Mill constant M.

[0151] The control command maximum change rate simulation device 921 determines the maximum value Max in the determination region L of the absolute value |s'(t)| of s'(t)|, which is calculated by differentiating s(t) from the calculation results shown in Figure 27. t Perform the calculation (s'(t)) and output the result.

[0152] The disturbance waveform control start point calculation device 922 is a device that calculates the start timing of control by the control device 1601, which does not produce an offset.

[0153] Figure 28 shows an example of a waveform illustrating the deviation of state variables calculated using the estimated deformation resistance table 920.

[0154] The maximum value of the estimated deformation resistance k' in the determination region L is defined as Max(k'(t)) and the minimum value as Min(k'(t)). The point where the deviation of the state variable is 0 is calculated as the point where the estimated deformation resistance k' = (Max(k'(t)) + Min(k'(t))) / 2. As shown in Figure 28, by starting control by the control device 1601 at the point where the deviation of the state variable from the command value is 0 or at the point where the state variable takes its median value, it becomes possible to perform control without offset, and the table identification number Index(n) of the nth starting point is output.

[0155] The control device 1 control gain suppression device 923 controls the maximum value of the rate of change output from the control command maximum change rate simulation device 921 Max t The suppression rate Gpre, which suppresses the control gain, is calculated using (s'(t)). The maximum value of the rate of change is Max. t When (s'(t)) is less than or equal to the maximum speed ACTrate used to control the controlled device, control gain suppression is not performed, and a suppression rate Gpre=1 is output. Maximum value of rate of change Max t When (s'(t)) is greater than the maximum speed ACTrate used to control the controlled device, control gain suppression is performed, and the suppression rate Gpre = ACTrate / Max t(s'(t)) is output.

[0156] The control activation timing command device 924 outputs a command FLAGpre=1 to the selection device 902 when the table identification number Index(n) of the nth starting point calculated by the disturbance waveform control start point calculation device 922 reaches the corresponding stand, indicating the timing at which the control device 1 601 will start control.

[0157] The embodiments described above are illustrative for the purpose of explaining the Disclosure and are not intended to limit the scope of the Disclosure to those embodiments only. Those skilled in the art can carry out the present invention in various other forms without departing from the scope of the Disclosure.

[0158] In this embodiment, the plant control system is applied to a tandem rolling mill 100, but it can also be applied to other controlled objects. For example, the plant control system disclosed can be applied to plants where control disturbances are large and feedforward control is required. For example, the plant control system disclosed can be applied to other plants such as plate thickness control in hot rolling mills and tension control in steel lines.

[0159] Furthermore, the embodiment described above includes the following matters. However, the matters included in this embodiment are not limited to those listed below.

[0160] (Item 1) A control system that outputs a control output to a controlled object that has state variables, performs predetermined control, and obtains a control result, A first control device calculates a first control output by multiplying a factor value, which is a value related to a variable factor that causes the control result to change, by a control gain, and performs feedforward control of the controlled object using the first control output. A second control device calculates a second control output by multiplying the aforementioned factor value by a control gain, calculates a third control output by integrating the deviation between the actual value and the target value of the state variable, and performs feedforward control using the second control output and integral control using the third control output on the controlled object. A selection device for selecting whether to have the first control device or the second control device perform the control of the control object, An unobservable variable factor prediction device that calculates estimated factor values ​​by predicting factor values ​​from the aforementioned state variables, A control device switching determination device that determines which of the first control device and the second control device to select based on the estimated factor values, and instructs the selection device on the determination result, A control system having According to this method, the accuracy of the control can be improved by predicting factor values ​​from state variables and selecting whether or not to use control, including integral control, based on the predicted estimated factor values.

[0161] (Item 2) In the control system described in item 1, The controlled object consists of multiple steps, from upstream to downstream, in which a state variable is given, a predetermined control is performed, and a control result is obtained. The aforementioned unobservable variable factor prediction device calculates the estimated factor value from the state variables in the upstream process, The control device switching determination device uses the estimated factor values ​​in the upstream process to determine whether to use the first control device or the second control device in the downstream process located downstream of the upstream process.

[0162] (Item 3) In the control system described in item 2, The controlled object performs machining on the same workpiece in both the upstream and downstream processes. The aforementioned variable factors are those whose value changes depending on the location of the workpiece. The control correction device further includes a control correction device that calculates the median value of the estimated factor value over a predetermined time range in the upstream process, identifies a location in the workpiece where the estimated factor value is the median value, calculates the timing at which that location reaches the position where processing is performed on the workpiece in the downstream process, and instructs the selection device to switch at the timing when switching from the second control device to the first control device. According to this method, the switch from the second control unit to the first control unit occurs when the variable factors reach their median value, thus suppressing the occurrence of offset during the switch.

[0163] (Item 4) In the control system described in item 2, The system further includes a control correction device that estimates the time change of the first control output in the downstream process based on the estimated factor value in the upstream process, and corrects the control gain of the first control device by a ratio calculated based on the time change of the first control output and the maximum speed at which the controlled object is controlled. According to this matter, the control gain of the first control device is suppressed in accordance with the time change of the first control output, so that the accuracy of the control can be improved by appropriate control according to the degree of fluctuation of the first control output.

[0164] (Item 5) In the control system described in item 1, The control device switching determination device determines which of the first control device and the second control device to select based on at least one of the frequency and amplitude of the estimated factor value.

[0165] (Item 6) In the control system described in item 1, The control device switching determination device instructs the selection device to switch between the first control device and the second control device at the timing when the estimated factor value matches the command value. According to this provision, the control device is switched when the fluctuating factor matches the command value, thus suppressing the occurrence of offset during switching.

[0166] (Item 7) In the control system described in item 1, The unobservable fluctuation factor prediction device inputs the calculated estimated factor value to the first control device. The first control device calculates the first control output by multiplying the input estimated factor value by the control gain. According to this matter, the control accuracy of the first control device can be improved.

[0167] (Item 8) In the control system described in item 1, The first control device multiplies the factor value by a positive correction gain when the factor value is changing in a positive direction that increases the state quantity, and multiplies the factor value by a negative correction gain when the factor value is changing in a negative direction that decreases the state quantity. According to this, the first control unit corrects the feedforward control offset, so the offset is well suppressed when the first control unit is selected.

[0168] (Item 9) In the control system described in any one of items 1 to 8, The controlled object is a rolling mill that processes the rolled material by rolling, The state quantity is at least one of the thickness of the rolled material and the tension applied to the rolled material. [Explanation of symbols]

[0169] 1…Working roll, 2…Intermediate roll, 3…Backup roll, 11-14…Rolling mill, 15…Outbound bridle roll, 21…Drive unit, 23…Drive unit, 25…Drive unit, 31-34…Roll gap control device, 40-44…Thickness gauge, 50-54…Tension gauge, 61-64…Thickness control device, 71-74…Tension control device, 80…Load cell, 100…Tandem rolling mill, 200…Rolled material, 201…Transfer time compensation unit, 202…Feedfor Word control unit, 203...Proportional circuit, 204...Integral circuit, 210...Feedforward control output, 220...Feedback control output, 230...Control output, 301...Proportional-integral section, 310...Control output, 400...Deformation resistance, 410...Stand in-side plate thickness deviation, 420...Stand out-side plate thickness deviation, 430...Stand-to-stand tension, 440...Stand out-side tension, 450...Stand load, 511...PI control device, 521...I control device, 522...FF control Your device, 600...Controlled plant, 601...Control device 1, 602...Phase shift factor, 603...Controlled disturbance source, 604...Unobservable disturbance prediction device, 611...FF control device, 612...Offset correction device, 701...Difference circuit, 702...Positive filter circuit, 703...Negative filter circuit, 704~707...Multiplier, 708...Integration circuit, 711...Delay circuit, 801...State quantity offset measuring device, 802...Correction gain calculation device, 900...Plan Control device 901...Control device 2, 902...Selection device, 903...Transfer processing calculation, 904...Transfer processing calculation, 905...Calculated load calculation device, 906...Estimated deformation resistance calculation device, 920...Estimated deformation resistance table, 921...Control command maximum change rate simulation device, 922...Disturbance waveform control start point calculation device, 923...Control gain suppression device, 924...Control input timing command device, 925...Control correction device, 926...Control device switching determination device

Claims

1. A control system that outputs a control output to a control target in which a process of obtaining a control result is carried out in a sequence from upstream to downstream, in which state variables are given, predetermined control is performed, and a control result is obtained, A first control device calculates a first control output by multiplying a factor value, which is a value related to a variable factor that causes the control result to change, by a control gain, and performs feedforward control on the controlled object using the first control output. A second control device calculates a second control output by multiplying the factor value by a control gain, calculates a third control output by integrating the deviation between the actual value and the target value of the state variable, and performs feedforward control using the second control output and integral control using the third control output on the controlled object. A selection device for selecting whether to have the first control device or the second control device perform the control of the control object, An unobservable fluctuation factor prediction device that calculates estimated factor values ​​by predicting factor values ​​in a downstream process located downstream of the upstream process from the state quantities of the inlet and outlet in the upstream process, A control device switching determination device that uses the estimated factor values ​​to determine which of the first control device and the second control device to select in the downstream process, and instructs the selection device on the determination result, A control system having

2. The controlled object performs machining on the same workpiece in both the upstream and downstream processes. The aforementioned variable factors are those whose value changes depending on the location of the workpiece. The control correction device further includes a control correction device that calculates the median value of the estimated factor value over a predetermined time range in the upstream process, identifies a location in the workpiece where the estimated factor value is the median value, calculates the timing at which that location reaches the position where processing is performed on the workpiece in the downstream process, and instructs the selection device to switch at the timing when switching from the second control device to the first control device. The control system according to claim 1.

3. The control correction device further comprises an upstream process that estimates the time change of the first control output in the downstream process based on the estimated factor value, and corrects the control gain of the first control device by a ratio calculated based on the time change of the first control output and the maximum speed at which the controlled object is controlled. The control system according to claim 1.

4. The control device switching determination device determines which of the first control device and the second control device to select based on at least one of the frequency and amplitude of the estimated factor value. The control system according to claim 1.

5. The control device switching determination device instructs the selection device to switch between the first control device and the second control device at the timing when the estimated factor value matches the command value. The control system according to claim 1.

6. The unobservable fluctuation factor prediction device inputs the calculated estimated factor value to the first control device. The first control device calculates the first control output by multiplying the input estimated factor value by the control gain. The control system according to claim 1.

7. The first control device multiplies the factor value by a positive correction gain when the factor value is changing in a positive direction that increases the state quantity, and multiplies the factor value by a negative correction gain when the factor value is changing in a negative direction that decreases the state quantity. The control system according to claim 1.

8. The controlled object is a rolling mill that processes the rolled material by rolling, The aforementioned state quantity is at least one of the thickness of the rolled material and the tension applied to the rolled material. The control system according to any one of claims 1 to 7.

9. A control system that outputs a control output to a control target having multiple steps in a sequence from upstream to downstream, in which a state variable is given, a predetermined control is performed, and a control result is obtained, comprising: a first control device that calculates a first control output by multiplying a factor value, which is a value relating to a variable factor that causes the control result to change, by a control gain, and performs feedforward control on the control target using the first control output; and a second control device that calculates a second control output by multiplying the factor value by a control gain, calculates a third control output by integrating the deviation between the actual value and the target value of the state variable, and performs feedforward control using the second control output and integral control using the third control output on the control target, wherein the control system outputs a control output to the control target, Estimated factor values ​​are calculated by predicting the factor values ​​in the downstream process, which is downstream of the upstream process, from the state quantities of the inlet and outlet in the upstream process. Using the estimated factor values, the system selects whether to use the first control device or the second control device to perform control on the controlled object in the downstream process. Control method.

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