Parameter adjustment device

Abstract

To shorten parameter adjustment time of a cascade control device.SOLUTION: A parameter adjustment device 3 adjusts a scaling lower limit and a scaling upper limit for calculating a target value RSP on a slave side in a cascade control device including a master-side control unit 1-1 and a slave-side control unit 1-2 from an operation amount MVm on a master side. The parameter adjustment device 3 comprises a parameter adjustment unit 31 which changes at least one of the scaling lower limit and the scaling upper limit until a controlled variable PVm is settled at a target value SPm based on a known slave-side controlled variable PVs=PVa when the controlled variable PVm is settled at the target value SPm and an operation amount MVm output from the master-side control unit 1-1 during cascade control when the controlled variable PVm is settled at a value different from the target value SPm during the cascade control.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a parameter adjustment device that adjusts parameters of a cascade control device in which a plurality of control units are cascade-connected. [Background technology]

[0002] A control method called cascade control is known for improving the disturbance response in a control system and reducing hunting (see Patent Document 1). Cascade control has been introduced in various situations, such as the control of semiconductor diffusion furnaces.

[0003] In cascade control, in addition to adjusting the PID parameters of the two control units (controllers), it is necessary to adjust the upper and lower scaling limits, which are parameters specific to cascade control. In order to adjust the upper and lower scaling limits, for example in the case of a temperature control system, it is necessary to repeat the operation->cooling cycle two or three times. This posed an issue in that it took a lot of time and manpower to adjust the parameters before control could begin. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-34357 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made to solve the above-mentioned problems, and has an object to provide a parameter adjustment device that can shorten the parameter adjustment time of a cascade control device. [Means for solving the problem]

[0006] The present invention provides a parameter adjustment device that adjusts a scaling lower limit value and a scaling upper limit value for calculating a slave-side target value from a master-side manipulated variable in a cascade control device in which a master-side control unit and a slave-side control unit are cascade-connected, The present invention is characterized in that it comprises a first parameter adjustment unit configured to dynamically change at least one of the scaling lower limit value and the scaling upper limit value, when the master side control amount is settled at a value different from the master side target value during cascade control, based on a known slave side control amount when the master side control amount is settled at the master side target value and a master side operation amount output from the master side control unit during the cascade control, until the master side control amount is settled at the master side target value.

[0007] Furthermore, in one configuration example of the parameter adjustment device of the present invention, the first parameter adjustment unit sets an initial value of the scaling lower limit value and an initial value of the scaling upper limit value before starting cascade control, and changes the scaling upper limit value based on a known slave-side control amount when the master-side control amount is settled at the master-side target value, a master-side operation amount output from the master-side control unit during the cascade control, and the initial value of the scaling lower limit value or a previous value of the scaling lower limit value; and changes the scaling lower limit value based on a known slave-side control amount when the master-side control amount is settled at the master-side target value, a master-side operation amount output from the master-side control unit during the cascade control, and the initial value of the scaling upper limit value or a previous value of the scaling upper limit value.

[0008] Furthermore, in one configuration example of the parameter adjustment device of the present invention, when calculating the changed scaling upper limit value SH, the first parameter adjustment unit calculates the changed scaling upper limit value SH by SH={PVa-SL+(MVm / 100)×SL} / (MVm / 100), where PVa is the known slave-side control amount when the master-side control amount is settled at the master-side target value, MVm is the master-side manipulated variable output from the master-side control unit during the cascade control, and SL is the initial value of the scaling lower limit value or the previous value of the scaling lower limit value; and when calculating the changed scaling lower limit value SL, SL is calculated by SL={PVa-(MVm / 100)×SH} / {-(MVm / 100)+1}, where PVa is the known slave-side control amount when the master-side control amount is settled at the master-side target value, MVm is the master-side manipulated variable output from the master-side control unit during the cascade control, and SH is the initial value of the scaling upper limit value or the previous value of the scaling upper limit value.

[0009] Furthermore, in one configuration example of the parameter adjustment device of the present invention, the cascade control device is characterized in that it includes the master-side control unit configured to calculate the master-side operation amount based on the master-side control amount and the master-side target value, the slave-side control unit configured to calculate the slave-side operation amount based on the slave-side control amount and the slave-side target value and output the slave-side operation amount to a control target, and a target value conversion unit provided between the master-side control unit and the slave-side control unit and configured to convert the master-side operation amount into the slave-side target value based on the scaling lower limit value and the scaling upper limit value. Furthermore, in one configuration example of the parameter adjustment device of the present invention, the target value conversion unit calculates the slave-side target value RSP by RSP=(MVm / 100)×(SH-SL)+SL, where MVm is the master-side manipulated variable output from the master-side control unit during the cascade control, SL is the scaling lower limit, and SH is the scaling upper limit.

[0010] Furthermore, one configuration example of the parameter adjustment device of the present invention is characterized in that it further includes a second parameter adjustment unit configured to calculate and set PID parameters of the slave-side control unit based on the response of the control amount of the slave side when auto-tuning of the slave-side control unit is executed before the start of cascade control, and to calculate and set PID parameters of the master-side control unit based on the response of the control amount of the master side when auto-tuning of the master-side control unit is executed. Effect of the Invention

[0011] According to the present invention, by providing a first parameter adjustment unit, at least one of the scaling upper limit value and the scaling lower limit value is updated during cascade control, making it possible to significantly shorten the parameter adjustment time compared to conventional parameter adjustment methods. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a block diagram showing a configuration of a cascade control device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a flowchart illustrating the control operation of the cascade control device according to the embodiment of the present invention. [Diagram 3] FIG. 3 is a diagram showing an example of a controlled object according to an embodiment of the present invention. [Figure 4] FIG. 4 is a flowchart illustrating the operation of the parameter adjustment device according to an embodiment of the present invention. [Diagram 5]FIG. 5 is a diagram showing an example of changes in the target value on the slave side, the controlled variable on the slave side, and the controlled variable on the master side when the scaling upper limit value is changed during control in the embodiment of the present invention. [Figure 6] FIG. 6 is a diagram showing an example of changes in the target value on the slave side, the controlled variable on the slave side, and the controlled variable on the master side when the scaling lower limit value is changed during control in the embodiment of the present invention. [Figure 7] FIG. 7 is a block diagram showing an example of the configuration of a computer that realizes the cascade control device and the parameter adjustment device according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a block diagram showing the configuration of a cascade control device according to an embodiment of the present invention. The cascade control device includes two cascade-connected control units (controllers) 1-1 and 1-2, a target value conversion unit 2 that is provided between the master control unit 1-1 and the slave control unit 1-2 and converts a manipulated variable MVm calculated by the master control unit 1-1 into a target value RSP of the slave control unit 1-2, a parameter adjustment device 3 that adjusts parameters of the control units 1-1 and 1-2 and the target value conversion unit 2, and an actuator 4 that operates a controlled object according to the manipulated variable MVs calculated by the slave control unit 1-2.

[0014] The parameter adjustment device 3 includes a parameter adjustment unit 30 that adjusts the PID parameters of the control units 1-1 and 1-2, and a parameter adjustment unit 31 that adjusts the scaling upper limit value and the scaling lower limit value of the target value conversion unit 2.

[0015] First, the control operation of the cascade control device will be explained before explaining the operation of the parameter adjustment device 3. Fig. 2 is a flowchart explaining the control operation of the cascade control device of this embodiment. The target value SPm of the master side control unit 1-1 is set, for example, by a user of the cascade control device and input to the master side control unit 1-1 (step S100 in FIG. 2).

[0016] The control amount PVm of the master-side control unit 1-1 is measured by a sensor (not shown) provided in the controlled object 5-1 on the master side, and is input to the master-side control unit 1-1 (Step S101 in FIG. 2).

[0017] The master side control unit 1-1 receives the target value SPm and the controlled variable PVm as input, and calculates the manipulated variable MVm by a known PID control calculation so that the controlled variable PVm coincides with the target value SPm (step S102 in FIG. 2).

[0018] The target value conversion unit 2 converts the manipulated variable MVm output from the master control unit 1-1 into a target value RSP for the slave control unit 1-2 by the conversion formula (1) and outputs it to the slave control unit 1-2 (Step S103 in FIG. 2). RSP=(MVm / 100)×(SH-SL)+SL ···(1)

[0019] In formula (1), SL is a scaling lower limit value, and SH is a scaling upper limit value. The control amount PVs of the slave-side control unit 1-2 is measured by a sensor (not shown) provided in the slave-side controlled object 5-2 and input to the slave-side control unit 1-2 (step S104 in FIG. 2).

[0020] The slave-side control unit 1-2 receives the target value RSP and the controlled variable PVs, and calculates the manipulated variable MVs by a well-known PID control calculation so that the controlled variable PVs coincides with the target value RSP (step S105 in FIG. 2). The manipulated variable MVs is output to the actuator 4. The above-described processing of steps S100 to S105 is repeatedly executed for each control period until the operation of the cascade control device is completed (YES in step S106 in FIG. 2).

[0021] Fig. 3 is a diagram showing an example of a controlled object of this embodiment. The heating device shown in Fig. 3 is composed of a heat treatment furnace 200 that heats an object to be heated, an electric heater 201, a temperature sensor 202 that measures the temperature (controlled variable PVm) near the air circulation outlet in the heat treatment furnace 200, a temperature sensor 203 that measures the temperature (controlled variable PVs) near the electric heater in the heat treatment furnace 200, a master side controller 1-1, a slave side controller 1-2, a target value converter 2, and an actuator 4. The actuator 4 supplies power to the electric heater 201 according to the manipulated variable MVs.

[0022] Next, the operation of the parameter adjustment device 3 will be described with reference to Fig. 4. First, before the start of normal control by the cascade control device, the parameter adjustment unit 30 performs auto-tuning of the slave-side control unit 1-2 in a single loop consisting of the slave-side control unit 1-2, the actuator 4, and the controlled object 5-2. The parameter adjustment unit 30 calculates the PID parameters (proportional band, integral time, derivative time) of the slave-side control unit 1-2, and sets the calculated PID parameters in the slave-side control unit 1-2 (step S200 in Fig. 4).

[0023] An example of autotuning is a limit cycle autotuning method in which a constant amplitude manipulated variable MVs is applied to the actuator 4 and PID parameters are calculated from the response of the controlled object 5-2 (amplitude and period of the controlled variable PVs).

[0024] Next, the parameter adjustment unit 31 sets initial values ​​of the scaling upper limit SH and the scaling lower limit SL for the target value conversion unit 2 as shown in equations (2) and (3) (step S201 in FIG. 4). SH = SPm + α (2) SL = SPm - β (3)

[0025] In formulas (2) and (3), α and β are preset constants. The values ​​of the constants α and β vary depending on the application, but if controllability is important, they should be set to small values ​​such as ±10.

[0026] Next, the parameter adjustment unit 30 performs auto-tuning of the master-side control unit 1-1 in two loops: a loop consisting of the master-side control unit 1-1, the target value conversion unit 2, the slave-side control unit 1-2, the actuator 4, and the controlled objects 5-2 and 5-1, and a loop consisting of the slave-side control unit 1-2, the actuator 4, and the controlled object 5-2. The parameter adjustment unit 30 calculates PID parameters for the master-side control unit 1-1 and sets the calculated PID parameters in the master-side control unit 1-1 (Step S202 in FIG. 4).

[0027] An example of autotuning is a limit cycle autotuning method in which a constant amplitude manipulated variable MVm is applied to the target value converter 2 and PID parameters are calculated from the response of the controlled object 5-1 (amplitude and period of the controlled variable PVm).

[0028] Next, after the cascade control device starts normal control, when the master side control variable PVm is settled at a value different from the master side target value SPm (YES in steps S203 and S204 in FIG. 4), the parameter adjustment unit 30 changes at least one of the scaling upper limit value SH and the scaling lower limit value SL (step S205 in FIG. 4).

[0029] When the master side control amount PVm is settled at a value below the master side target value SPm, the parameter adjustment unit 31 sets the scaling upper limit value SH as an unknown quantity, or sets both the scaling upper limit value SH and the scaling lower limit value SL as unknown quantities, and when the master side control amount PVm is settled at a value exceeding the master side target value SPm, the parameter adjustment unit 31 sets the scaling lower limit value SL as an unknown quantity, or sets both the scaling upper limit value SH and the scaling lower limit value SL as unknown quantities.

[0030] Specifically, when calculating the changed scaling upper limit value SH, the parameter adjustment unit 31 substitutes the known slave-side control amount PVs=PVa when the master-side control amount PVm is settled at the master-side target value SPm into equation (4) obtained from equation (1), and further substitutes the manipulated variable MVm output from the master-side control unit 1-1 and the initial value of the scaling lower limit value SL set in equation (3) or the previous value of the scaling lower limit value SL into equation (4) to calculate the changed scaling upper limit value SH. Equation (4) is a modification of equation (1) by replacing RSP with PVa. SH={PVa-SL+(MVm / 100)×SL} / (MVm / 100) (4)

[0031] When changing both the scaling upper limit value SH and the scaling lower limit value SL, the parameter adjustment unit 31 substitutes the initial value of the scaling lower limit value SL into equation (4) during the first calculation, and substitutes the previously calculated scaling lower limit value SL into equation (4) during the second or subsequent calculations.

[0032] Furthermore, when calculating the changed scaling lower limit value SL, the parameter adjustment unit 31 substitutes the known slave-side control amount PVs=PVa when the master-side control amount PVm is settled at the master-side target value SPm into equation (5) obtained from equation (1), and further substitutes the manipulated variable MVm output from the master-side control unit 1-1 and the initial value of the scaling upper limit value SH set in equation (2) or the previous value of the scaling upper limit value SH into equation (5) to calculate the changed scaling lower limit value SL. Equation (5) is a modification of equation (1) by replacing RSP with PVa. SL={PVa-(MVm / 100)×SH} / {-(MVm / 100)+1} (5)

[0033] When changing both the scaling upper limit value SH and the scaling lower limit value SL, the parameter adjustment unit 31 substitutes the initial value of the scaling upper limit value SH into equation (5) during the first calculation, and substitutes the previously calculated scaling upper limit value SH into equation (5) during the second or subsequent calculations.

[0034] The slave-side control amount PVs=PVa when the master-side control amount PVm is settled at the master-side target value SPm is an actual measurement value obtained by a prior test. This test may be performed after the initial values ​​of the scaling upper limit value SH and the scaling lower limit value SL are set as described above and auto-tuning of the slave-side control unit 1-2 and the master-side control unit 1-1 is completed.

[0035] When at least one of the scaling upper limit value SH and the scaling lower limit value SL is changed during the control operation described in FIG. 2, the slave-side target value RSP calculated by the target value conversion unit 2 using equation (1) changes, so that the slave-side operation amount MVs output to the actuator 4 changes, the slave-side control amount PVs changes, and further the master-side control amount PVm changes. The parameter adjustment unit 31 waits until the controlled variable PVm on the master side is stabilized (step S206 in FIG. 4).

[0036] In this manner, the processes of steps S204 to S206 are repeatedly executed until PVm=SPm, that is, until the controlled variable PVm on the master side is stabilized at the target value SPm on the master side. As described above, in this embodiment, at least one of the scaling upper limit value SH and the scaling lower limit value SL is updated during control, so there is no need to repeat the operation->cooling cycle two or three times as in the conventional parameter adjustment method, and it is possible to significantly shorten the parameter adjustment time.

[0037] An example of changes in the slave side target value RSP, the slave side control amount PVs, and the master side control amount PVm when the scaling upper limit SH is changed during cascade control in this embodiment is shown in Fig. 5. Also, an example of changes in the slave side target value RSP, the slave side control amount PVs, and the master side control amount PVm when the scaling lower limit SL is changed during cascade control in this embodiment is shown in Fig. 6.

[0038] 5 and 6, it can be seen that by changing the scaling upper limit value SH or the scaling lower limit value SL, the target value RSP on the slave side changes, the control amount PVs on the slave side changes toward the changed target value RSP, and the control amount PVm on the master side changes toward the target value SPm on the master side.

[0039] Fig. 5 is an example in which the scaling upper limit value SH is changed when the master side control amount PVm is settled at a value below the master side target value SPm, and Fig. 6 is an example in which the scaling lower limit value SL is changed when the master side control amount PVm is settled at a value exceeding the master side target value SPm, but as described above, both the scaling upper limit value SH and the scaling lower limit value SL may be changed. It is set in advance whether to change only one of them as in the examples of Fig. 5 and Fig. 6, or to change both the scaling upper limit value SH and the scaling lower limit value SL.

[0040] In this embodiment, the parameter adjustment device 3 is provided inside the cascade control device, but it may be provided outside the cascade control device. Further, in this embodiment, the controlled variables PVm and PVs are temperatures, but the present invention is not limited to this and may be applied to controlled variables other than temperature.

[0041] The cascade control device described in this embodiment can be realized by a computer equipped with a CPU (Central Processing Unit), a storage device, and an interface, and a program that controls these hardware resources. An example of the configuration of this computer is shown in FIG.

[0042] The computer includes a CPU 300, a storage device 301, and an interface device (I / F) 302. A sensor such as a thermometer, an actuator 4, and the like are connected to the I / F 302. In such a computer, a program for implementing the parameter adjustment method of the present invention is stored in the storage device 301. The CPU 300 executes the processing described in this embodiment in accordance with the program stored in the storage device 301. When the parameter adjustment device is provided outside the cascade control device as described above, the cascade control device and the parameter adjustment device may be realized by separate computers. [Industrial Applicability]

[0043] The present invention can be applied to a cascade control system. [Explanation of symbols]

[0044] 1-1, 1-2...control unit, 2...target value conversion unit, 3...parameter adjustment device, 30, 31...parameter adjustment unit.

Claims

1. A parameter adjustment device that adjusts a scaling lower limit value and a scaling upper limit value for calculating a slave-side target value from a master-side manipulated variable in a cascade control device in which a master-side control unit and a slave-side control unit are cascade-connected, a first parameter adjustment unit configured to dynamically change at least one of the scaling lower limit value and the scaling upper limit value, when a master-side control amount is settled at a value different from a master-side target value during cascade control, based on a known slave-side control amount when the master-side control amount is settled at the master-side target value and a master-side operation amount output from the master-side control unit during the cascade control, until the master-side control amount is settled at the master-side target value.

2. 2. The parameter adjustment device according to claim 1, the first parameter adjustment unit sets an initial value of the scaling lower limit value and an initial value of the scaling upper limit value before starting cascade control, and changes the scaling upper limit value based on a known slave-side control amount when the master-side control amount is settled at the master-side target value, a master-side operation amount output from the master-side control unit during the cascade control, and the initial value of the scaling lower limit value or a previous value of the scaling lower limit value; and changes the scaling lower limit value based on a known slave-side control amount when the master-side control amount is settled at the master-side target value, a master-side operation amount output from the master-side control unit during the cascade control, and the initial value of the scaling upper limit value or a previous value of the scaling upper limit value.

3. 3. The parameter adjustment device according to claim 2, When calculating the changed scaling upper limit value SH, the first parameter adjustment unit calculates the changed scaling upper limit value SH by SH={PVa-SL+(MVm / 100)×SL} / (MVm / 100), where PVa is a known slave-side control amount when the master-side control amount is settled at the master-side target value, MVm is a master-side manipulated variable output from the master-side control unit during the cascade control, and SL is an initial value of the scaling lower limit value or a previous value of the scaling lower limit value, the parameter adjustment device, when calculating a new scaling lower limit value SL, calculates the changed scaling lower limit value SL by SL = {PVa - (MVm / 100) x SH} / {-(MVm / 100) + 1}, where PVa is a known slave-side control amount when the master-side control amount is settled at the master-side target value, MVm is a master-side operation amount output from the master-side control unit during the cascade control, and SH is an initial value of the scaling upper limit value or a previous value of the scaling upper limit value.

4. 2. The parameter adjustment device according to claim 1, The cascade control device includes: the master-side control unit configured to calculate an operation amount of the master side based on a control amount of the master side and a target value of the master side; the slave-side control unit configured to calculate a slave-side operation amount based on the slave-side control amount and the slave-side target value, and output the operation amount to a controlled object; a target value conversion unit that is provided between the master-side control unit and the slave-side control unit and is configured to convert an operation amount on the master side into a target value on the slave side based on the scaling lower limit value and the scaling upper limit value.

5. 5. The parameter adjustment device according to claim 4, The parameter adjustment device is characterized in that the target value conversion unit calculates the target value RSP of the slave side by the formula RSP = (MVm / 100) x (SH - SL) + SL, where MVm is the master side operation amount output from the master side control unit during the cascade control, SL is the scaling lower limit value, and SH is the scaling upper limit value.

6. 2. The parameter adjustment device according to claim 1, a second parameter adjustment unit configured to calculate and set a PID parameter of the slave-side control unit based on a response of a control amount of the slave side when auto-tuning of the slave-side control unit is executed before start of cascade control, and to calculate and set a PID parameter of the master-side control unit based on a response of the control amount of the master side when auto-tuning of the master-side control unit is executed.

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