JP6974142B2 - Control device and control method - Google Patents

Description

The present invention relates to a technique for additionally applying feedforward control to a feedback controller, and more particularly to a control device and a control method suitable for performing arbitrary operation amount addition or operation amount subtraction by an operator's operation.

A multifunctional general-purpose feedback controller (temperature controller) may be used to handle a device including one or more control loops (see Patent Document 1). FIG. 27 shows an example of a heating device targeted by a general-purpose feedback controller (temperature controller).

In the example of FIG. 27, the heating device is heated by a heat treatment furnace 100 for heating an object to be heated, a plurality of heaters H1 to H4 installed inside the heat treatment furnace 100, and heaters H1 to H4, respectively. A plurality of temperature sensors S1 to S4 for measuring the temperature of the temperature control zones Z1 to Z4 in the heat treatment furnace 100, a regulator 101 for calculating the operation amounts MV1 to MV4 to be output to the heaters H1 to H4, and a regulator 101. It is composed of power regulators 102-1 to 102-4 that supply power corresponding to the operation amounts MV1 to MV4 output from the heaters H1 to H4. The controller 101 calculates the operation amounts MV1 to MV4 so that the temperatures PV1 to PV4 measured by the temperature sensors S1 to S4 coincide with the temperature set values SP1 to SP4. In the heating device shown in FIG. 27, four control loops for controlling the temperatures PV1 to PV4 are formed.

In a device including a plurality of control loops, the occurrence of interference between control zones may make it impossible to obtain a desired control result by feedback control alone. Further, even if only one control loop is used, a desired control result may not be obtained only by feedback control due to the influence of strong non-linearity or the like.

Therefore, a method of adding a feedforward amount to PID control, which is a typical feedback control, has been proposed (see Patent Document 2). The feedforward control + PID control disclosed in Patent Document 2 has a particular problem of not causing an overshoot (improvement of the control result).

When realizing feedforward control + PID control, it is practically a good idea to use a commercially available general-purpose feedback controller (temperature controller) for temperature control as a feedback control function part (PID control function part). .. In this case, since intermediate variables and the like in the PID calculation inside the temperature controller cannot be manipulated, it is not always possible to simply additionally apply the feedforward control, and problems may occur, so improvement is required.

Japanese Unexamined Patent Publication No. 2012-048370 Japanese Unexamined Patent Publication No. 2007-102816

The present invention has been made to solve the above problems, and is a control device capable of reducing the occurrence of defects when feedforward control is additionally applied to a general-purpose feedback controller (for example, a PID-controlled temperature controller). And to provide a control method.

The control device of the present invention has an operation amount calculation unit configured to calculate an operation amount by PID control calculation by inputting a set value and a control amount, and an operation amount calculated by this operation amount calculation unit. The limit processing unit configured to perform limit processing that limits based on the limit value, the operation amount output unit configured to output this limit processed operation amount to the control target, and the feed forward are not executed. A normal limit value storage unit configured to store the normal value of the manipulated variable limit value applied at the time of normal control in advance, and a manipulated variable limit target which is a value obtained by changing the normal value by the feed forward. When the limit value acquisition unit configured to acquire the value and the operation amount limit target value different from the normal value are acquired, the operation amount limit target value is approached and then gradually converges to the normal value. A limit value changing unit for calculating the manipulated variable limit value and setting it in the limit processing unit is provided , and the limit value changing unit calculates the manipulated variable with a first parameter relating to the time of the manipulated variable limit value. It is characterized in that it is automatically determined in conjunction with the PID parameter of the unit.
Further, the control device of the present invention has an operation amount calculation unit configured to calculate an operation amount by PID control calculation by inputting a set value and a control amount, and an operation amount calculated by this operation amount calculation unit. A limit processing unit configured to perform limit processing that limits based on the operation amount limit value, an operation amount output unit configured to output this limit processed operation amount to the control target, and feedforward. An operation amount that is a normal limit value storage unit configured to store the normal value of the operation amount limit value applied at the time of normal control that is not executed in advance, and a value obtained by changing the normal value by feedforward. When the limit value acquisition unit configured to acquire the limit target value and the operation amount limit target value different from the normal value are acquired, the operation amount limit target value is approached and then gradually increased to the normal value. The operation amount limit target value is provided with a limit value change unit that calculates the operation amount limit value that converges to the limit value and sets it in the limit processing unit, and the operation amount limit target value is a value obtained by step-changing the normal value by a feedforward amount.

Further, in one configuration example of the control device of the present invention, the operation amount limit value is the operation amount upper limit value, and the limit processing unit uses the operation amount calculated by the operation amount calculation unit as the operation amount upper limit value. Limit processing is performed to limit to the following values, the normal limit value storage unit stores the operation amount upper limit normal value in advance as the normal value of the operation amount limit value, and the limit value acquisition unit stores the operation amount limit target. The operation amount upper limit target value is acquired as a value, and when the limit value acquisition unit acquires the operation amount upper limit target value different from the operation amount upper limit normal value, the operation amount upper limit target value is obtained. It is characterized in that the operation amount upper limit value that gradually converges to the operation amount upper limit normal value after approaching is calculated and set in the limit processing unit.
Further, in one configuration example of the control device of the present invention, the operation amount limit value is the operation amount lower limit value, and the limit processing unit uses the operation amount calculated by the operation amount calculation unit as the operation amount lower limit value. The limit process for limiting to the above values is performed, the normal limit value storage unit stores the operation amount lower limit normal value in advance as the normal value of the operation amount limit value, and the limit value acquisition unit stores the operation amount limit target. The operation amount lower limit target value is acquired as a value, and when the limit value acquisition unit acquires the operation amount lower limit target value different from the operation amount lower limit normal value, the operation amount lower limit target value is obtained. It is characterized in that the operation amount lower limit value that gradually converges to the operation amount lower limit normal value after approaching is calculated and set in the limit processing unit.

Further , in one configuration example of the control device of the present invention, the limit value changing unit is characterized in that a second parameter defining the size of the feedforward is automatically determined in conjunction with the first parameter. Is to be .

Further, in the control method of the present invention, a first step of calculating an operation amount by a PID control calculation with a set value and a control amount as inputs, and a limit process of limiting the operation amount based on the operation amount limit value are performed. The feed forward portion is added to the second step, the third step of outputting the limit processed operation amount to the control target, and the normal value of the operation amount limit value applied at the time of normal control in which feed forward is not executed. The fourth step of acquiring the manipulated variable limit target value which is the changed value, and when the manipulated variable limit target value different from the normal value is acquired, after approaching the manipulated variable limit target value, the normal look including a fifth step of setting calculates the operation amount limit value gradually converges to a value, the fifth step, the first parameter relating to time of the operation amount limit value, the PID It is characterized by including a step of automatically determining in conjunction with the PID parameter of the control calculation.
Further, in the control method of the present invention, a first step of calculating an operation amount by PID control calculation with a set value and a control amount as inputs, and a limit process of limiting the operation amount based on the operation amount limit value are performed. The feedforward amount is added to the second step, the third step of outputting the limit processed operation amount to the control target, and the normal value of the operation amount limit value applied at the time of normal control in which feedforward is not executed. The fourth step of acquiring the manipulated variable limit target value which is the changed value, and when the manipulated variable limit target value different from the normal value is acquired, after approaching the manipulated variable limit target value, the normal The operation amount limit target value includes a fifth step of calculating and setting the operation amount limit value that gradually converges to a value, and the operation amount limit target value is a value obtained by step-changing the normal value by a feedforward amount.

According to the present invention, when the feedforward control is additionally applied to the feedback control by the operation amount calculation unit by providing the normal limit value storage unit, the limit value acquisition unit, and the limit value change unit, there is a problem with the feedback control. Can be reduced.

Further, in the present invention, by automatically determining the first parameter regarding the time of the manipulated variable limit value in conjunction with the PID parameter of the manipulated variable limit value, the change of the manipulated variable limit value by the feed forward is controlled. It roughly matches the cycle when the vertical movement occurs, and the elapsed time from the start of the change of the manipulated variable limit value to the time when the feed forward amount reaches the maximum applied amount is roughly matched with the time of the first parameter. be able to.

Further, in the present invention, by automatically determining the second parameter that defines the size of feedforward in conjunction with the first parameter, the maximum application amount for feedforward is roughly set to the operation amount limit target value. Can be matched.

FIG. 1 is a block diagram showing a configuration of a control device according to an embodiment of the present invention. FIG. 2 is a block diagram of a control system according to an embodiment of the present invention. FIG. 3 is a flowchart showing the operation of the operation amount calculation unit, the limit processing unit, and the operation amount output unit of the control device according to the embodiment of the present invention. FIG. 4 is a flowchart illustrating the operation of the FF upper limit value acquisition unit and the upper limit value change unit of the control device according to the embodiment of the present invention. FIG. 5 is a flowchart illustrating the operation of the FF lower limit value acquisition unit and the lower limit value change unit of the control device according to the embodiment of the present invention. FIG. 6 is a diagram showing an example of changes in the controlled variable and the manipulated variable when the temperature is controlled without executing feedforward. FIG. 7 is a diagram showing an example of an operation amount lower limit value and an operation amount upper limit value when the temperature is controlled without executing feedforward. FIG. 8 is a diagram showing an example of changes in the control amount and the operation amount when the upper limit value of the operation amount is changed by the feedforward amount and returned to 100% after a certain period of time has elapsed. FIG. 9 is a diagram showing another example of changes in the control amount and the operation amount when the upper limit value of the operation amount is changed by the feedforward amount and returned to 100% after a certain period of time has elapsed. FIG. 10 is a diagram showing an example of changes in the control amount and the operation amount when the temperature is controlled by the control device according to the embodiment of the present invention. FIG. 11 is a diagram showing an example of changes in the operation amount lower limit value and the operation amount upper limit value when the temperature is controlled by the control device according to the embodiment of the present invention. FIG. 12 is a diagram showing another example of changes in the control amount and the operation amount when the temperature is controlled by the control device according to the embodiment of the present invention. FIG. 13 is a diagram showing another example of changes in the operation amount lower limit value and the operation amount upper limit value when the temperature is controlled by the control device according to the embodiment of the present invention. FIG. 14 is a diagram showing another example of changes in the control amount and the operation amount when the temperature is controlled by the control device according to the embodiment of the present invention. FIG. 15 is a diagram showing another example of changes in the operation amount lower limit value and the operation amount upper limit value when the temperature is controlled by the control device according to the embodiment of the present invention. FIG. 16 is a diagram showing another example of changes in the control amount and the operation amount when the temperature is controlled by the control device according to the embodiment of the present invention. FIG. 17 is a diagram showing another example of changes in the operation amount lower limit value and the operation amount upper limit value when the temperature is controlled by the control device according to the embodiment of the present invention. FIG. 18 is a diagram showing an example of changes in the controlled variable and the manipulated variable when the temperature is controlled with the parameter relating to the time of the manipulated variable upper limit set to a value smaller than that of the embodiment of the present invention. FIG. 19 is a diagram showing an example of changes in the operation amount lower limit value and the operation amount upper limit value when the temperature is controlled by setting the parameter related to the time of the operation amount upper limit value to a value smaller than that of the embodiment of the present invention. FIG. 20 is a diagram showing an example of changes in the controlled variable and the manipulated variable when the parameter relating to the time of the manipulated variable upper limit is temperature controlled as a value larger than that of the embodiment of the present invention. FIG. 21 is a diagram showing an example of changes in the operation amount lower limit value and the operation amount upper limit value when the temperature is controlled by setting the parameter related to the time of the operation amount upper limit value to a value larger than that of the embodiment of the present invention. FIG. 22 is a diagram showing an example of changes in the control amount and the operation amount when the temperature is controlled without executing the feed forward. FIG. 23 is a diagram showing an example of an operation amount lower limit value and an operation amount upper limit value when the temperature is controlled without executing feedforward. FIG. 24 is a diagram showing another example of changes in the control amount and the operation amount when the temperature is controlled by the control device according to the embodiment of the present invention. FIG. 25 is a diagram showing another example of changes in the operation amount lower limit value and the operation amount upper limit value when the temperature is controlled by the control device according to the embodiment of the present invention. FIG. 26 is a block diagram showing a configuration example of a computer that realizes the control device according to the embodiment of the present invention. FIG. 27 is a diagram showing a configuration example of a heating device including a plurality of control loops.

[Principle 1 of the invention]
Arbitrary operation amount addition (including subtraction) by the operator can be positioned as feedforward in the control structure.
For the manipulated variable output by the PID calculation of the temperature controller, the output saturation is determined only by the manipulated variable MV calculated by the thermometer, and the anti-reset windup process for the integral operation is performed. Therefore, it is necessary to solve the problem that the temperature controller does not function normally if the feedforward portion that remains constantly is added to the feedback portion (operation amount MV by PID calculation). For example, when the temperature controller outputs an operation amount MV = 60% with sufficient margin for output saturation, when 50% feedforward is added, it becomes 110%, and the output exceeds 100%. Although it becomes saturated, there is an inconsistency that the anti-reset windup process is not executed as the temperature controller.

Therefore, the inventor applies the feedforward amount to the operation amount lower limit value OL or the operation amount upper limit value OH, and operates at a speed at which the feedback amount can follow within the range of the operation amount lower limit value OL and the operation amount upper limit value OH. If the lower limit of quantity OL or the upper limit of manipulated variable OH is gradually (stepwise, almost continuously) converged to the original value, the feedforward portion is no longer a structure of addition to the feedback portion, and in theory, feedback is provided. I came up with the idea that it can be operated as a control that outputs a continuous operation amount MV only for control. This eliminates the inconvenience for PID calculation.

[Principle 2 of the invention]
The parameter Tf (first parameter) relating to the time of the operation amount lower limit value OL or the operation amount upper limit value OH is automatically determined in conjunction with the PID parameter (for example, integration time Ti). As a result, it is possible to easily maintain the change of the feedforward amount of the operation amount lower limit value OL or the operation amount upper limit value OH so as to be substantially in agreement with the cycle when the vertical movement of the control occurs.

In addition, the parameter Kx (second parameter) that defines the size of feedforward in conjunction with the time parameter Tf so that the parameter value set by the operator is maintained at a physical quantity that is visually easy for the operator to understand. It is preferable to automatically change. For example, it is conceivable to internally process each parameter so that the parameter value set by the operator always corresponds to the maximum feedforward application amount.

[Principle 3 of the invention]
By designating the feedforward portion so as to mean a stepwise change of the operation amount lower limit value OL or the operation amount upper limit value OH, it becomes easy for the operator to manually operate the feedforward amount. In addition, the instruction content for automatically reproducing this operation can be simplified.

[Example]
Hereinafter, examples of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a control device according to an embodiment of the present invention. This embodiment is an example corresponding to the above-mentioned principle 1, the principle 2 of the invention, and the principle 3 of the invention. Here, an example of application to a general-purpose feedback controller (PID-controlled temperature controller) will be described.

The control device sets the operation amount calculation unit 1 that calculates the operation amount MV by PID control calculation by inputting the set value SP and the control amount PV, and the operation amount MV calculated by the operation amount calculation unit 1 as the operation amount limit value ( The limit processing unit 2 that performs limit processing based on the operation amount lower limit value OL and the operation amount upper limit value OH), the operation amount output unit 3 that outputs the limit processed operation amount MV to the control target, and feedforward. Of the normal values of the operation amount limit value applied during normal control that is not executed, the normal upper limit value storage unit 4 that stores the operation amount upper limit normal value OH_R in advance and the operation applied during normal control that does not execute feedforward. Of the normal values of the amount limit value, the normal lower limit value storage unit 5 that stores the operation amount lower limit normal value OL_R in advance, and the operation amount upper limit target value that is a value obtained by changing the operation amount upper limit normal value OH_R by the feedforward amount. The FF (feedforward) upper limit value acquisition unit 6 for acquiring OH_F (operation amount limit target value) and the operation amount lower limit target value OL_F (operation amount limit) which is a value obtained by changing the feedforward amount to the operation amount lower limit normal value OL_R. When the FF lower limit value acquisition unit 7 for acquiring the target value) and the operation amount upper limit target value OH_F different from the operation amount upper limit normal value OH_R are acquired, the operation amount upper limit normal value OH_R is approached after the operation amount upper limit target value OH_F is approached. When the upper limit value changing unit 8 that calculates the operation amount upper limit value OH that gradually converges to and sets it in the limit processing unit 2 and the operation amount lower limit target value OL_F that is different from the operation amount lower limit normal value OL_R are acquired, the operation is performed. It is provided with a lower limit value changing unit 9 that calculates an operation amount lower limit value OL that gradually converges to the operation amount lower limit normal value OL_R after approaching the amount lower limit target value OL_F and sets it in the limit processing unit 2.

The normal upper limit value storage unit 4 and the normal lower limit value storage unit 5 constitute a normal limit value storage unit 10. The FF upper limit value acquisition unit 6 and the FF lower limit value acquisition unit 7 constitute a limit value acquisition unit 11. The upper limit value changing unit 8 and the lower limit value changing unit 9 constitute a limit value changing unit 12.
FIG. 2 is a block diagram of the control system of this embodiment. P in FIG. 2 indicates a control target.

Next, the operation of the control device of this embodiment will be described with reference to FIGS. 3 to 5. FIG. 3 is a flowchart showing the operations of the operation amount calculation unit 1, the limit processing unit 2, and the operation amount output unit 3, FIG. 4 is a flowchart explaining the operations of the FF upper limit value acquisition unit 6 and the upper limit value change unit 8, and FIG. It is a flowchart explaining the operation of the FF lower limit value acquisition unit 7 and the lower limit value change unit 9.

The set value SP (for example, the temperature set value) is set by an operator of the control device and is input to the operation amount calculation unit 1 (step S100 in FIG. 3).
The controlled variable PV (for example, a temperature measured value) is measured by a measuring instrument (for example, a temperature sensor that measures the temperature of the object to be heated) (not shown), and is input to the manipulated variable calculation unit 1 (step S101 in FIG. 3).

The operation amount calculation unit 1 inputs the set value SP and the control amount PV, and performs a PID control operation such as the following transfer function formula so that the control amount PV matches the set value SP, and the operation amount MV. Is calculated (FIG. 3, step S102).
MV = (100 / Pb) {1+ (1 / Tis) + Tds} (SP-PV)
... (1)
Pb is the proportional band, Ti is the integration time, Td is the differential time, and s is the Laplace operator.

The limit processing unit 2 limits the operation amount MV calculated by the operation amount calculation unit 1 to a value equal to or higher than the predetermined operation amount lower limit value OL, and sets the operation amount MV to a value equal to or less than the operation amount upper limit value OH. The upper limit process for limiting is performed (step S103 in FIG. 3).
IF MV <OL THEN MV'= OL ... (2)
IF MV> OH THEN MV'= OH ... (3)
That is, the limit processing unit 2 sets the operation amount MV'= OL when the operation amount MV is smaller than the operation amount lower limit value OL, and sets the operation amount MV'= OH when the operation amount MV is larger than the operation amount upper limit value OH. ..

The operation amount output unit 3 outputs the operation amount MV'that has been limit-processed by the limit processing unit 2 to the control target (step S104 in FIG. 3). The output destination of the operation amount MV'is an operation unit (not shown) such as a heater or a valve. In the case of a heater, the actual output destination of the manipulated variable MV'is a power regulator (not shown) that supplies power to the heater.

The control device executes the processes of steps S100 to S104 of FIG. 3 for each control cycle until the control is completed, for example, by an instruction of the operator (YES in step S105 of FIG. 3).

Next, in the normal upper limit value storage unit 4, the operation amount upper limit value OH (hereinafter, the operation amount upper limit normal value OH_R) applied at the time of normal control in which feedforward is not executed is stored in advance. The normal lower limit value storage unit 5 stores in advance the operation amount lower limit value OL (hereinafter, the operation amount lower limit normal value OL_R) applied at the time of normal control in which feedforward is not executed.

The FF upper limit value acquisition unit 6 acquires the operation amount upper limit target value OH_F, which is a value obtained by changing the operation amount upper limit normal value OH_R by the feedforward amount. Specifically, the FF upper limit value acquisition unit 6 acquires the operation amount upper limit target value OH_F input from the outside, but acquires the value sent by communication at a predetermined timing, or is input by the operator. There are a form of acquiring a value appropriately input by using a function, and a form of acquiring a value automatically generated by changing the set value SP input to the operation amount calculation unit 1.

The FF lower limit value acquisition unit 7 acquires the operation amount lower limit target value OL_F, which is a value obtained by changing the operation amount lower limit normal value OL_R by the feedforward amount. Similar to the FF upper limit value acquisition unit 6, the FF lower limit value acquisition unit 7 acquires the operation amount lower limit target value OL_F input from the outside. As a form of acquiring the operation amount lower limit target value OL_F, as in the FF upper limit value acquisition unit 6, a form of acquiring a value sent by communication at a predetermined timing, or an operator using an input function as appropriate. There are a form of acquiring an input value and a form of acquiring a value automatically generated when the set value SP input to the operation amount calculation unit 1 is changed.

That is, in the system to which the control device of this embodiment is applied, for example, in order to suppress a disturbance assumed during control, an operation is performed from the host device to the control device at a specified timing or at a timing of changing the set value SP. It is conceivable that the amount upper limit target value OH_F and the operation amount lower limit target value OL_F are automatically input, or the operator manually inputs the operation amount upper limit target value OH_F and the operation amount lower limit target value OL_F during control.

When the FF upper limit value acquisition unit 6 acquires the operation amount upper limit target value OH_F different from the operation amount upper limit normal value OH_R (YES in step S200 of FIG. 4), the upper limit value change unit 8 approaches the operation amount upper limit target value OH_F. After that, the operation amount upper limit value OH that gradually converges to the operation amount upper limit normal value OH_R is calculated (FIG. 4 step S201), and the calculated operation amount upper limit value OH is set in the limit processing unit 2 (FIG. 4 step S202). .. Specifically, the upper limit value changing unit 8 calculates the manipulated variable upper limit value OH by the following transfer function formula.
OH = OH_R + {Kxs / (1 + Tfs) ² } (OH_F-OH_R)
... (4)

Tf in the equation (4) is a parameter relating to the time of the operation amount upper limit value OH. In the upper limit value changing unit 8, the PID parameter set in the manipulated variable calculation unit 1, specifically, a value obtained by α times the integration time Ti may be set as Tf (Tf = αTi, the predetermined value α is, for example, 0. 1-2.0). As a result, the change of the feedforward amount of the operation amount upper limit value OH becomes substantially the same as the cycle when the vertical movement of the control occurs. Further, the elapsed time from the start of the change of the operation amount upper limit value OH until the feedforward amount reaches the maximum applied amount almost coincides with the time of the parameter Tf (FIGS. 11 and 13, which will be described later). 15. Operation amount upper limit value OH in FIG. 17).

Kx in equation (4) is a parameter that defines the size of feedforward. The upper limit value changing unit 8 may set a value β times the parameter Tf to Kx (Kx = βTf, a predetermined value β is, for example, 2.75). As a result, the maximum applied amount for feedforward generally coincides with the operation amount upper limit target value OH_F (operation amount upper limit value OH in FIGS. 11, 13, 15, and 17 described later).

On the other hand, when the FF lower limit value acquisition unit 7 acquires the operation amount lower limit target value OL_F different from the operation amount lower limit normal value OL_R (YES in step S300 of FIG. 5), the lower limit value change unit 9 has the operation amount lower limit target value OL_F. The operation amount lower limit value OL that gradually converges to the operation amount lower limit normal value OL_R after approaching is calculated (FIG. 5 step S301), and the calculated operation amount lower limit value OL is set in the limit processing unit 2 (FIG. 5 step). S302). Specifically, the lower limit value changing unit 9 calculates the manipulated variable lower limit value OL by the following transfer function formula.
OL = OL_R + {Kxs / (1 + Tfs) ² } (OL_F-OL_R)
... (5)

Similar to the upper limit value changing unit 8, the lower limit value changing unit 9 may set the value of α times the integration time Ti as Tf (Tf = αTi, the predetermined value α is, for example, 0.1 to 2.0). Further, the lower limit value changing unit 9 may set a value β times the parameter Tf to Kx (Kx = βTf, a predetermined value β is, for example, 2.75). As a result, the maximum applied amount for feedforward generally coincides with the operation amount lower limit target value OL_F.

After the FF upper limit value acquisition unit 6 acquires the operation amount upper limit target value OH_F different from the operation amount upper limit normal value OH_R, the upper limit value change unit 8 repeatedly calculates and sets the operation amount upper limit value OH. The manipulated variable upper limit value OH finally converges to the manipulated variable upper limit normal value OH_R. Similarly, after the FF lower limit value acquisition unit 7 acquires the operation amount lower limit target value OL_F different from the operation amount lower limit normal value OL_R, the lower limit value change unit 9 repeatedly calculates and sets the operation amount lower limit value OL. .. The operation amount lower limit value OL finally converges to the operation amount lower limit normal value OL_R.

The transfer functions of the equations (4) and (5) adopted in this embodiment are typical examples conforming to the principle 1 of the invention and the principle 2 of the invention, and are not limited thereto. For example, although the second-order lag of the denominator of the transfer function is set to the same time constant Tf, it is possible to change it to a different time constant or change the order. Further, if the coefficient β is adjusted according to the order of the time constant and how to select the balance, the principle 2 of the invention can be surely applied.

In the case of the configuration of the FF upper limit value acquisition unit 6 and the upper limit value change unit 8 or the configuration of the FF lower limit value acquisition unit 7 and the lower limit value change unit 9 in this embodiment, the operator can use the input function to perform arbitrary timing. If the operation amount lower limit value OL or the operation amount upper limit value OH is specified to mean a stepwise change, the feedforward process of the present invention can be appropriately started. That is, it corresponds to the principle 3 of the invention.

Hereinafter, the effect of this embodiment will be verified by simulation. In the following example, the control target is a heating control system that can be approximated by a first-order lag transfer function having a process gain Kp = 8, a process time constant Tp = 200 seconds, and a process waste time Lp = 50 seconds. That is, the model formula Gp to be controlled can be described as the following formula.
Gp = Kpexp (-Lps) / (1 + Tps) ... (6)

Further, the PID parameters set in the manipulated variable calculation unit 1 are set to the proportional band Pb = 200 ° C., the integration time Ti = 150 seconds, and the differential time Td = 0 seconds (that is, PI control), and the set value SP is set from 100 ° C. to 350 ° C. The temperature was changed to ° C. Although only the case of changing only the operation amount upper limit value OH is shown, the operation amount lower limit value OL may be changed as described later.

6 and 7 are diagrams showing comparison targets for confirming the effect of this embodiment, and FIG. 6 is an example of changes in the controlled amount PV and the manipulated amount MV when the temperature is controlled without executing feedforward. FIG. 7 is a diagram showing the operation amount lower limit value OL = 0% and the operation amount upper limit value OH = 100% in this case. In the example of FIG. 6, in conjunction with the large decrease in the control amount PV (temperature) around 400 seconds, the decrease in the control amount PV is conspicuous even after 600 seconds, and a state that cannot be said to be a clear settling occurs. There is.

8 and 9 are diagrams showing an example of changes in the controlled variable PV and the manipulated variable MV when the feedforward amount is changed to the manipulated variable upper limit value OH and immediately returned to 100% after a certain period of time has elapsed. It is a figure which shows the problem of the continuous feedback control. In the example of FIG. 8, the set value SP is changed from 100 ° C. to 350 ° C., and at the same time, the operation amount upper limit value OH is changed from 100% to 65%, maintained for 125 seconds, and then returned to 100%. At the same time as changing the set value SP, the operation amount upper limit value OH is changed from 100% to 65%, maintained for 85 seconds, and then returned to 100%.

In the example of FIG. 8, since the upper limit of the manipulated variable OH = 65% is maintained for 125 seconds, it is possible to suppress a large decrease in the controlled variable PV (temperature) around 400 seconds, and the controlled variable after 600 seconds. It can be said that the drop in PV became inconspicuous and the settling state was reached earlier than in FIG. On the other hand, in the example of FIG. 9, since the operation amount upper limit value OH = 65% is maintained only for 85 seconds, the effect of changing the operation amount upper limit value OH to 65% is clearly insufficient as compared with FIG. It can be said that the result is close to that of FIG.

In this way, if the upper limit of the manipulated variable OH is immediately returned to 100% after a certain period of time, the magnitude of the manipulated variable MV will cause discontinuous and extremely different time points. The control result may differ greatly depending on the situation. In other words, even if good control results are obtained once by maintaining the upper limit of manipulated variable OH = 65% for 125 seconds as shown in FIG. 8, when the characteristics of the controlled object change even slightly. It is possible that the control results will deteriorate rapidly and clearly.

FIG. 10 is a diagram showing an example of changes in the controlled variable PV and the manipulated variable MV when the temperature is controlled with the parameter Tf = 60.0 seconds (corresponding to Tf = 0.4Ti) in this embodiment, and FIG. 11 is a diagram showing an example of changes in the manipulated variable MV in this case. It is a figure which shows the change of the operation amount upper limit value OH (the operation amount lower limit value OL is fixed at 0%). In this example, the operation amount upper limit target value OH_F = 65%, the parameter Kx = 165.0, and the parameter Tf = 60.0 seconds.

Similar to the example of FIG. 8, since the control amount PV (temperature) can be suppressed from dropping significantly around 400 seconds, the drop of the control amount PV after 600 seconds becomes inconspicuous, which is compared with FIG. It can be said that the settling state was reached at an early time.

FIG. 12 is a diagram showing an example of changes in the controlled variable PV and the manipulated variable MV when the temperature is controlled with the parameter Tf = 80.0 seconds (corresponding to Tf = 0.53Ti) in this embodiment, and FIG. 13 is a diagram showing an example of changes in the manipulated variable MV in this case. It is a figure which shows the change of the operation amount upper limit value OH (the operation amount lower limit value OL is fixed at 0%). In this example, the operation amount upper limit target value OH_F = 65%, the parameter Kx = 220.0, and the parameter Tf = 80.0 seconds. According to FIG. 12, it can be seen that the same control result as in the case of FIG. 10 is obtained.

FIG. 14 is a diagram showing an example of changes in the controlled variable PV and the manipulated variable MV when the temperature is controlled with the parameter Tf = 100.0 seconds (corresponding to Tf = 0.67Ti) in this embodiment, and FIG. 15 shows an example in this case. It is a figure which shows the change of the operation amount upper limit value OH (the operation amount lower limit value OL is fixed at 0%). In this example, the operation amount upper limit target value OH_F = 65%, the parameter Kx = 275.0, and the parameter Tf = 100.0 seconds. According to FIG. 14, it can be seen that the same control results as in the cases of FIGS. 10 and 12 are obtained.

FIG. 16 is a diagram showing an example of changes in the controlled variable PV and the manipulated variable MV when the temperature is controlled with the parameter Tf = 120.0 seconds (corresponding to Tf = 0.8Ti) in this embodiment, and FIG. 17 is a diagram showing an example of changes in the manipulated variable MV in this case. It is a figure which shows the change of the operation amount upper limit value OH (the operation amount lower limit value OL is fixed at 0%). In this example, the operation amount upper limit target value OH_F = 65%, the parameter Kx = 330.0, and the parameter Tf = 120.0 seconds. According to FIG. 16, it can be seen that the same control results as in the cases of FIGS. 10, 12, and 14 are obtained.

As described above, according to this embodiment, the effect of alleviating the problem of discontinuous feedback control can be obtained. That is, when the feedforward control is additionally applied, the occurrence of a defect can be reduced and the convenience for the operator can be improved.

FIG. 18 shows the control amount PV when the temperature is controlled with the parameter Tf set to a value Tf = 8.0 seconds (corresponding to Tf = 0.053Ti) smaller than that of the present embodiment in order to confirm the effect of the principle 2 of the above invention. FIG. 19 is a diagram showing an example of a change in the operation amount MV, and FIG. 19 is a diagram showing a change in the operation amount upper limit value OH in this case (the operation amount lower limit value OL is fixed at 0%). In this example, the operation amount upper limit target value is OH_F = 65%, Kx = 22.0, and Tf = 8.0 seconds.

The examples of FIGS. 18 and 19 can be regarded as setting examples in which the parameter Tf is too small for the integration time Ti and the integration time Ti is not substantially referred to. Since the feedforward operation is completed in a short time with respect to the control behavior, the effect of feedforward is hardly obtained.

FIG. 20 shows the controlled amount PV when the temperature is controlled with the parameter Tf set to a value Tf = 800.0 seconds (corresponding to Tf = 5.3Ti) larger than that of the present embodiment in order to confirm the effect of the principle 2 of the above invention. FIG. 21 is a diagram showing an example of a change in the operation amount MV, and FIG. 21 is a diagram showing a change in the operation amount upper limit value OH in this case (the operation amount lower limit value OL is fixed at 0%). In this example, the operation amount upper limit target value OH_F = 65%, the parameter Kx = 2200.0, and the parameter Tf = 800.0 seconds.

The examples of FIGS. 20 and 21 can be regarded as a setting example in which the parameter Tf is too large for the integration time Ti and the integration time Ti is not substantially referred to. Since the feedforward operation tends to be delayed for a long time with respect to the control behavior, the effect of feedforward is hardly obtained.

Next, the effect of this embodiment is verified by another simulation. In the following example, the control target is a heating control system that can be approximated to a first-order delay transfer function with a process gain Kp = 8, a process time constant Tp = 200 seconds, and a process waste time Lp = 50 seconds. The PID parameters to be set were proportional band Pb = 600 ° C., integration time Ti = 200 seconds, and differential time Td = 0 seconds (that is, PI control). Then, it is assumed that the temperature drop disturbance occurs in a state where the set value SP = control amount PV = 300 ° C. is set. Although only the case of changing only the operation amount lower limit value OL is shown, the operation amount upper limit value OH may be changed as described above.

FIG. 22 is a diagram showing a comparison target for confirming the effect of this embodiment, and FIG. 22 is a diagram showing an example of changes in the controlled amount PV and the manipulated amount MV when the temperature is controlled without executing feedforward. 23 is a diagram showing the operation amount lower limit value OL = 0% and the operation amount upper limit value OH = 100% in this case. In the example of FIG. 22, the controlled variable PV (temperature) drops significantly from around 100 seconds and reaches about 220 ° C. It takes about 1000 seconds to settle by the disturbance response.

FIG. 24 is a diagram showing an example of changes in the control amount PV and the operation amount MV when the temperature is controlled with the parameter Tf = 20.0 seconds (corresponding to Tf = 0.1Ti) in this embodiment, and FIG. 25 shows an example of the change in the operation amount MV in this case. It is a figure which shows the change of the operation amount lower limit value OL (the operation amount upper limit value OH is fixed at 100%). In this example, the operation amount upper limit target value OL_F = 100%, the parameter Kx = 55.0, and the parameter Tf = 20.0 seconds.

According to FIG. 24, it can be seen that the control amount PV (temperature) can be suppressed from dropping significantly to about 255 ° C. in the vicinity of 100 seconds as in the case of FIG. 22. Further, it takes about 700 seconds to settle by the disturbance response, and it can be said that the settling state can be reached earlier than in the case of FIG. 22.

The control device described in this embodiment can be realized by a computer provided with a CPU (Central Processing Unit), a storage device, and an interface, and a program for controlling these hardware resources. A configuration example of this computer is shown in FIG. The computer includes a CPU 600, a storage device 601 and an interface device (hereinafter, abbreviated as I / F) 602. For example, a temperature sensor and a power regulator are connected to the I / F 602. In such a computer, a program for realizing the control method of the present embodiment is stored in the storage device 601. The CPU 600 executes the process described in this embodiment according to the program stored in the storage device 601.

This embodiment can be applied to a control device.

1 ... Operation amount calculation unit, 2 ... Limit processing unit, 3 ... Operation amount output unit, 4 ... Normal upper limit value storage unit, 5 ... Normal lower limit value storage unit, 6 ... FF upper limit value acquisition unit, 7 ... FF lower limit value acquisition unit Unit, 8 ... Upper limit value change unit, 9 ... Lower limit value change unit, 10 ... Normal limit value storage unit, 11 ... Limit value acquisition unit, 12 ... Limit value change unit.

Claims (7)

An operation amount calculation unit configured to calculate an operation amount by PID control calculation with a set value and a control amount as inputs,
A limit processing unit configured to perform limit processing that limits the operation amount calculated by this operation amount calculation unit based on the operation amount limit value, and
An operation amount output unit configured to output this limit-processed operation amount to the control target,
A normal limit value storage unit configured to store a normal value of the manipulated variable limit value applied at the time of normal control that does not execute feedforward in advance, and a normal limit value storage unit.
A limit value acquisition unit configured to acquire an operation amount limit target value which is a value obtained by changing the normal value by a feedforward amount, and a limit value acquisition unit.
When the manipulated variable limit target value different from the normal value is acquired, the manipulated variable limit value that gradually converges to the normal value after approaching the manipulated variable limit target value is calculated and sent to the limit processing unit. and a limit value changing unit that sets,
The limit value changing unit is a control device characterized in that a first parameter relating to the time of the manipulated variable limit value is automatically determined in conjunction with the PID parameter of the manipulated variable calculation unit. An operation amount calculation unit configured to calculate an operation amount by PID control calculation with a set value and a control amount as inputs,
A limit processing unit configured to perform limit processing that limits the operation amount calculated by this operation amount calculation unit based on the operation amount limit value, and
An operation amount output unit configured to output this limit-processed operation amount to the control target,
A normal limit value storage unit configured to store a normal value of the manipulated variable limit value applied at the time of normal control that does not execute feedforward in advance, and a normal limit value storage unit.
A limit value acquisition unit configured to acquire an operation amount limit target value which is a value obtained by changing the normal value by a feedforward amount, and a limit value acquisition unit.
When the manipulated variable limit target value different from the normal value is acquired, the manipulated variable limit value that gradually converges to the normal value after approaching the manipulated variable limit target value is calculated and sent to the limit processing unit. Equipped with a limit value change part to set
The control device, wherein the manipulated variable limit target value is a value obtained by step-changing the normal value by a feedforward amount. In the control device according to claim 1 or 2.
The manipulated variable limit value is the manipulated variable upper limit value.
The limit processing unit performs limit processing that limits the operation amount calculated by the operation amount calculation unit to a value equal to or less than the operation amount upper limit value.
The normal limit value storage unit stores in advance an operation amount upper limit normal value as a normal value of the operation amount limit value.
The limit value acquisition unit acquires the operation amount upper limit target value as the operation amount limit target value, and obtains the operation amount upper limit target value.
When the limit value acquisition unit acquires the operation amount upper limit target value different from the operation amount upper limit normal value, the limit value change unit moves to the operation amount upper limit normal value after approaching the operation amount upper limit target value. A control device characterized in that the upper limit value of the manipulated variable that gradually converges is calculated and set in the limit processing unit. In the control device according to claim 1 or 2.
The manipulated variable limit value is the manipulated variable lower limit value.
The limit processing unit performs limit processing for limiting the operation amount calculated by the operation amount calculation unit to a value equal to or higher than the operation amount lower limit value.
The normal limit value storage unit stores in advance a lower limit normal value of the manipulated variable as a normal value of the manipulated variable limit value.
The limit value acquisition unit acquires the operation amount lower limit target value as the operation amount limit target value, and obtains the operation amount lower limit target value.
When the limit value acquisition unit acquires the operation amount lower limit target value different from the operation amount lower limit normal value, the limit value change unit approaches the operation amount lower limit target value and then returns to the operation amount lower limit normal value. A control device characterized in that the lower limit value of the manipulated variable that gradually converges is calculated and set in the limit processing unit. In the control device according to claim 1,
The limit value changing unit is a control device characterized in that a second parameter defining the size of the feedforward is automatically determined in conjunction with the first parameter. The first step of calculating the operation amount by PID control calculation with the set value and the control amount as input, and
The second step of performing the limit process of limiting the manipulated variable based on the manipulated variable limit value, and
The third step of outputting this limit-processed operation amount to the control target,
The fourth step of acquiring the operation amount limit target value which is a value obtained by changing the feedforward amount to the normal value of the operation amount limit value applied at the time of normal control in which feedforward is not executed.
A fifth that calculates and sets the manipulated variable limit value that gradually converges to the normal value after approaching the manipulated variable limit target value when the manipulated variable limit target value different from the normal value is acquired. and a step seen including,
The fifth step is a control method including a step of automatically determining a first parameter relating to the time of the manipulated variable limit value in conjunction with the PID parameter of the PID control calculation. The first step of calculating the operation amount by PID control calculation with the set value and the control amount as input, and
The second step of performing the limit process of limiting the manipulated variable based on the manipulated variable limit value, and
The third step of outputting this limit-processed operation amount to the control target,
The fourth step of acquiring the operation amount limit target value which is a value obtained by changing the feedforward amount to the normal value of the operation amount limit value applied at the time of normal control in which feedforward is not executed.
A fifth that calculates and sets the manipulated variable limit value that gradually converges to the normal value after approaching the manipulated variable limit target value when the manipulated variable limit target value different from the normal value is acquired. Including steps
The control method, wherein the manipulated variable limit target value is a value obtained by step-changing the normal value by a feedforward amount.

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