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JP-7854847-B2 - Control system and control method

JP7854847B2JP 7854847 B2JP7854847 B2JP 7854847B2JP-7854847-B2

Inventors

  • 萩原 泰志
  • 服部 哲

Assignees

  • 株式会社日立製作所

Dates

Publication Date
20260507
Application Date
20220428

Claims (9)

  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.

Description

This disclosure relates to technology for controlling controlled objects such as plants. In plant control, where a plant is the object of control, there are factors that cause changes in the plant's state variables. When these factors cause changes in the plant's state variables, the accuracy of the control results decreases. For example, in a rolling mill, a plant used to produce thin metal materials by rolling a workpiece, if there are variations in the hardness of the workpiece, this variation can cause variations in sheet thickness (poor sheet thickness) depending on the location. Hardness variation refers to the fact that the hardness of the workpiece is not uniform. Since the hardness of the workpiece acts as resistance to deformation during rolling, if there are variations in hardness in the rolling direction as the workpiece is transported, the way the workpiece is compressed will differ depending on the location. This results in variations in sheet thickness after rolling, causing sheet thickness fluctuations. Furthermore, in the production of metal materials by rolling, the rolled material is generally fed into the rolling mill multiple times to process the thickness from the original sheet thickness to the desired product thickness. Therefore, if there are variations in the hardness of the rolled material, the thickness will fluctuate each time it is fed into the rolling mill. 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 these 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 the deviation between a state variable such as plate thickness and a target value is large. Patent No. 3384330Patent No. 5581964Patent No. 6404195Japanese Patent Publication No. 2021-081772 This figure shows an example of a controlled plant according to this embodiment.This is a diagram to explain the rolling phenomenon.This figure shows a model representing the rolling phenomenon explained in Figure 2.This is a diagram illustrating an example of plate thickness control.This is a diagram illustrating an example of tension control.This diagram illustrates the phase difference between the controlled state variable and the control result under integral control.This diagram illustrates the phase difference between the controlled state variable and the control result under integral control.This diagram illustrates the phase difference between the controlled state variable and the control result under integral control.This diagram illustrates the effect of feedforward control on the controlled state variables.This figure shows the relationship between the control result, the control gain, and the phase shift amount.This is a schematic block diagram of the plant control system according to this embodiment.This is a block diagram of the control device 2.This figure shows an example of the control results of the control device 2 obtained through simulation.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.This figure shows an example of the offset removal result of the control device 2 obtained through simulation.This is a block diagram of control device 1.This figure shows an example of an FF control device.This is a diagram to explain the principle of offset correction.This is a diagram showing an example of an offset correction device.This figure shows an example of the control results of the control device 1 obtained through simulation.This figure shows an example of the control results of the control device 1 obtained through simulation.This is a diagram illustrating the plant control system.This diagram shows a configuration for evaluating hardness variations in rolled material.This is a flowchart of the process for calculating the estimated deformation resistance.This is a flowchart of the process for switching control devices.This diagram illustrates the switching from control device 2 to control device 1.This diagram shows the output of the control device 1.This figure shows an example of a waveform that illustrates the deviation of state variables. The embodiments of this disclosure will be described below with reference to the drawings. Here, we illustrate a configuration in which a plant control system controls a target plant. <<Controlled Plant>> First, let me explain the plant being