JP7544516B2 - Control device and control method - Google Patents

Description

The present invention relates to a control device and a control method that combines feedback control and feedforward control.

A method has been proposed in which a feedforward component is added to PID control, which is a typical feedback control (hereinafter referred to as feedforward + feedback control) (see Patent Document 1).

In order to improve the practicality of such feedforward + feedback control, particularly when applied to a heating device such as that shown in FIG. 17, the inventors have proposed a feedforward method (Patent Document 2) in which the lower limit value OL and upper limit value OH of the manipulated variable MV asymptotically converge to normal values, and a feedforward method (Patent Document 3) in which the feedforward amount MV_P asymptotically converges to zero.

The heating device in FIG. 17 is composed of a heat treatment furnace 100 for heating the workpiece to be treated, an electric heater 101, a temperature sensor 102 for measuring the temperature inside the heat treatment furnace 100, a temperature regulator 103 for controlling the temperature inside the heat treatment furnace 100, a power regulator 104, a power supply circuit 105, and a PLC (Programmable Logic Controller) 106 for controlling the entire heating device. The temperature regulator 103 calculates the manipulated variable MV so that the temperature PV (controlled variable) measured by the temperature sensor 102 matches the temperature set value SP. The power regulator 104 determines the power according to the manipulated variable MV, and supplies the determined power to the electric heater 101 via the power supply circuit 105.

The feedforward + feedback control proposed by the inventor in Patent Document 3 is close to typical feedforward control. The technology proposed by the inventor in Patent Document 3 will be explained using the block diagram of the control system in Figure 18. P in Figure 18 indicates the controlled object.

The manipulated variable calculation unit 201 receives a set value SP and a controlled variable PV as input, and calculates a manipulated variable MV (which in this invention is referred to as a basic manipulated variable MV) by performing a PID control calculation, for example, using the following transfer function equation, so that the controlled variable PV coincides with the set value SP.
MV=(100/Pb) {1+(1/Tis)+Tds}(SP-PV)
... (1)
Pb is the proportional band, Ti is the integral time, Td is the differential time, and s is the Laplace operator.

When an operating volume addition value FF_P (FF_P≠0) which is a target value of the addition amount of the feedforward portion for the basic operating volume MV is input, the addition volume calculation unit 204 calculates an operating volume addition value MV_P which gradually converges to a zero value after approaching the operating volume addition value FF_P. Specifically, the addition volume calculation unit 204 calculates the operating volume addition amount MV_P by the following transfer function formula.
MV_P={Kxs/(1+Tfs) ² }FF_P...(2)

In equation (2), Tf is a parameter that specifies the time for the manipulated variable addition amount MV_P to gradually converge. Kx is a parameter that specifies the magnitude of the feedforward. An example of the change in the manipulated variable addition amount MV_P is shown in FIG. 19. In the example of FIG. 19, the manipulated variable addition amount FF_P = 50%, the parameter Tf = 100 sec., and the parameter Kx = 275.

When an operating volume subtraction value FF_M (FF_M≠0) which is a target value of the subtraction amount of the feedforward portion for the basic operating volume MV is input, the subtraction amount calculation unit 205 calculates an operating volume subtraction amount MV_M which gradually converges to a zero value after approaching the operating volume subtraction value FF_M. Specifically, the subtraction amount calculation unit 205 calculates the operating volume subtraction amount MV_M by the following transfer function formula.
MV_M={Kxs/(1+Tfs) ² }FF_M...(3)

Tf in formula (3) is a parameter that specifies the time for gradually converging the manipulated variable subtraction amount MV_M. The manipulated variable change unit 206 adds the manipulated variable additional amount MV_P calculated by the additional amount calculation unit 204 to the basic manipulated variable MV calculated by the manipulated variable calculation unit 201, and further subtracts the manipulated variable subtraction amount MV_M calculated by the subtraction amount calculation unit 205 from the added amount, thereby calculating the manipulated variable MV_F (referred to as the actual manipulated variable MV_F in the present invention).
MV_F=MV+MV_P-MV_M...(4)

The limit processing unit 207 performs lower limit processing to limit the actual operation amount MV_F calculated by the operation amount change unit 206 to a value equal to or greater than a predetermined operation amount lower limit value OL, and upper limit processing to limit the actual operation amount MV_F to a value equal to or less than a predetermined operation amount upper limit value OH. The actual operation amount MV_F' limited by this limit processing unit 207 is output to the control object P.

The technology proposed in Patent Document 3 makes it possible to reduce problems that occur with discontinuous control, such as changing the basic operating variable MV by a feedforward amount and returning the feedforward amount to 0% after a certain period of time has elapsed.

However, it is rare for an ordinary operator (control technology user) who is not an expert in control technology to be able to properly evaluate the results of feedforward control. In particular, the added amount of the manipulated variable for the feedforward portion (in this invention, to distinguish it from Patent Document 3, this is called the feedforward amount MV_X) must be properly diagnosed and corrected. Needless to say, if the disturbance changes with respect to the feedforward amount MV_X, the effect of the feedforward control deteriorates. However, it is difficult for an ordinary operator who is not an expert in control technology to properly correct the feedforward amount MV_X and improve the effect of the feedforward control.

JP 2007-102816 A JP 2019-101846 A JP 2019-101847 A

The present invention has been made to solve the above problems, and aims to provide a control device and control method that can rationally diagnose the validity of the feedforward amount.

The control device of the present invention includes a manipulated variable calculation unit configured to calculate a first manipulated variable for each control cycle using a set value and a controlled variable as inputs, a feedforward calculation unit configured to calculate, for each control cycle, a sum of a first feedforward amount required to suppress a step disturbance and a second feedforward amount required to suppress an impulse disturbance in response to an input of a trigger variable that is a significant value before the application of the disturbance and a non-significant value after the application of the disturbance , as a third feedforward amount, a feedforward execution unit configured to add the third feedforward amount to the first manipulated variable calculated by the manipulated variable calculation unit for each control cycle , a manipulated variable output unit configured to output a second manipulated variable obtained by adding the third feedforward amount to the first manipulated variable to a controlled object, and a first estimation unit configured to estimate a difference between the second manipulated variable at the time of settling before a disturbance recovery response when a trigger variable becomes a significant value and the second manipulated variable after settling of the disturbance recovery as a first parameter for calculating the first feedforward amount, and to use the estimated first parameter as a first diagnostic index; a total amount calculation unit configured to calculate a total amount that is an integrated value of the first feedforward amount for each control period until the second manipulated variable becomes set, assuming that the same first parameter as the value estimated by the first estimation unit has been set in the feedforward calculation unit and that the first feedforward amount has been output based on the set first parameter when the trigger variable becomes a significant value; a second estimation unit configured to subtract a total amount of the first feedforward amount from a total amount that is an integrated value of an amount of change of the second manipulated variable in each control cycle until the second manipulated variable is settling, estimate a value obtained by multiplying the control cycle by a result of the subtraction as a second parameter for calculating the second feedforward amount, and use the estimated second parameter as a second diagnostic index ; an invalid amount calculation unit configured to calculate an invalid amount that is an integrated value of an amount of the second feedforward amount calculated by the feedforward calculation unit for each control cycle until the second manipulated variable is settling during a period in which the trigger variable becomes significant, the invalid amount being an integrated value of an amount of the second feedforward amount that is invalidated due to either output saturation in which the second manipulated variable exceeds a manipulated variable upper limit value or output saturation in which the second manipulated variable falls below a manipulated variable lower limit value; a correction unit configured to calculate a ratio between a total amount that is an integrated value of each control cycle of the second feedforward amount calculated by the feedforward calculation unit until the settling of the second manipulated variable during a period when the value of the second feedforward amount becomes a value of 100%, and a total amount that is an integrated value of each control cycle of the second feedforward amount that is not invalidated by the output saturation, based on the invalid amount , estimate a correction value obtained by multiplying the second diagnostic index by the ratio so that a corresponding portion of the invalid amount is distributed within a range of the second manipulated variable that is not invalidated by the output saturation, and use the estimated value as a corrected second diagnostic index; and a diagnostic index presentation unit configured to present the first diagnostic index and the corrected second diagnostic index.

Moreover, one configuration example of the control device of the present invention further includes a correction unit configured to correct the first parameter set in the feedforward calculation unit to the value of the first diagnostic index, correct the second parameter set in the feedforward calculation unit to the value of the corrected second diagnostic index, and correct a time constant set in the feedforward calculation unit that specifies the time for the second feedforward amount to gradually converge to a correction value of the time constant, and the correction unit calculates the corrected second diagnostic index and calculates a value obtained by multiplying the time constant by the ratio as the correction value of the time constant .
Moreover, in one configuration example of the control device of the present invention, the second feedforward amount is calculated by [Kx2s/{(1+ATfs)(1+(2.0-A)Tfs)}]FF_X, where the second parameter is Kx2, a time constant defining a time for gradually converging the second feedforward amount is Tf, a coefficient for adjusting the time constant is A, the trigger variable is FF_X, and a Laplace operator is s.
Furthermore, in one configuration example of the control device of the present invention, the correction unit calculates the ratio RH by Kx2/(Kx2-FF_N×dt), where FF_N is the reactive amount, dt is the control period which is a calculation period of the first manipulated variable and the first, second and third feedforward amounts, and RH is the ratio, calculates a correction value of the second parameter Kx2 by Kx2×RH as a second diagnostic index after the correction , and calculates a value Tf×RH obtained by multiplying the time constant Tf by the ratio RH as the correction value of the time constant Tf .
Moreover, in one configuration example of the control device of the present invention, the first feedforward amount is calculated by [Kx1/{(1+ATfs)(1+(2.0-A)Tfs)}]FF_X, where Kx1 is the first parameter, Tf is a time constant that specifies the time for gradually converging the first feedforward amount, A is a coefficient that adjusts the time constant, FF_X is the trigger variable, and s is a Laplace operator.

In addition, one configuration example of the control device of the present invention further includes an index ratio calculation unit configured to calculate, as a third diagnostic index, the ratio between the invalid amount and a total amount, which is the integrated value of each control cycle of the second feedforward amount calculated by the feedforward calculation unit until the second operating amount is settled during the period in which the trigger variable becomes a significant value, and the diagnostic index presentation unit is characterized in that it presents the third diagnostic index in addition to the first diagnostic index and the corrected second diagnostic index.
Moreover, one configuration example of the control device of the present invention further includes a limit processing unit that performs limit processing to limit a second manipulated variable calculated by the feedforward execution unit to a value equal to or greater than the manipulated variable lower limit value and equal to or less than the manipulated variable upper limit value, the manipulated variable output unit outputs the second manipulated variable that has been limited to a control target, the first estimator, the total amount calculation unit and the second estimator perform processing using the second manipulated variable that has been limited to as an input, and the invalid amount calculation unit calculates, during a period in which the trigger variable becomes a significant value, a value that is in the range of output saturation in which the second manipulated variable before the limit processing exceeds the manipulated variable upper limit value or output saturation in which the second manipulated variable before the limit processing falls below the manipulated variable lower limit value among the second feedforward amounts calculated by the feedforward calculation unit for each control cycle until the second manipulated variable that has been limited to a settling state during the period in which the trigger variable becomes a significant value. the correction unit calculates the invalid amount, which is an integrated value of the amount invalidated by either one of the above, and the correction unit calculates a ratio between a total amount, which is an integrated value of each control cycle of the second feedforward amount calculated by the feedforward calculation unit until the settling of the second operation amount subjected to the limit processing during a period in which the trigger variable becomes significant, and a total amount, which is an integrated value of each control cycle of the second feedforward amount that was not invalidated by the output saturation, based on the invalid amount, and estimates the correction value, which is obtained by multiplying the second diagnostic index by the ratio, as a value for correcting the second feedforward amount so that a corresponding portion of the invalid amount is distributed within a range of the second operation amount before the limit processing that is not invalidated by the output saturation, and sets the estimated value as the second diagnostic index after correction.
Moreover, one configuration example of the control device of the present invention further includes a limit processing unit that performs limit processing to limit a second manipulated variable calculated by the feedforward execution unit to a value equal to or greater than the manipulated variable lower limit value and equal to or less than the manipulated variable upper limit value, the manipulated variable output unit outputs the second manipulated variable that has been limited to a control target, the first estimator, the total amount calculation unit, the second estimator, and the index ratio calculation unit perform processing using the second manipulated variable that has been limited to an input, and the invalid amount calculation unit calculates, during a period in which the trigger variable becomes a significant value, output saturation in which the second manipulated variable before the limit processing exceeds the manipulated variable upper limit value or output saturation in which the second manipulated variable before the limit processing falls below the manipulated variable lower limit value among the second feedforward amounts calculated by the feedforward calculation unit for each control cycle until the second manipulated variable that has been limited to a settling time during which the trigger variable becomes a significant value. the correction unit calculates, based on the invalid amount, a ratio between a total amount that is an integrated value of each control cycle of the second feedforward amount calculated by the feedforward calculation unit until the settling of the second operation amount that has been limited during a period in which the trigger variable becomes a significant value, and a total amount that is an integrated value of each control cycle of the second feedforward amount that has not been invalidated due to the output saturation, and estimates the correction value obtained by multiplying the second diagnostic index by the ratio so that a corresponding portion of the invalid amount is distributed within a range of the second operation amount before the limit processing that is not invalidated due to the output saturation, and sets the estimated value as the second diagnostic index after correction.

The control method of the present invention includes a first step of calculating a first manipulated variable for each control cycle using a set value and a controlled variable as inputs, a second step of calculating a sum of a first feedforward amount required to suppress a step disturbance and a second feedforward amount required to suppress an impulse disturbance as a third feedforward amount for each control cycle in response to an input of a trigger variable that is a significant value before the application of the disturbance and a non-significant value after the application of the disturbance, a third step of adding the third feedforward amount to the first manipulated variable for each control cycle , a fourth step of outputting a second manipulated variable obtained by adding the third feedforward amount to the first manipulated variable to a controlled object, and a disturbance recovery response when the trigger variable becomes a significant value. a fifth step of estimating a difference between the second manipulated variable at the time of the previous settling and the second manipulated variable after the settling of disturbance recovery as a first parameter for calculating the first feedforward amount, and using the estimated first parameter as a first diagnostic index ; a sixth step of calculating a total amount which is an integrated value of the first feedforward amount for each control period until the second manipulated variable is settling, assuming that the same first parameter as the value estimated in the fifth step has already been set and the first feedforward amount has been output based on the already set first parameter when the trigger variable becomes a significant value; a seventh step of subtracting a total amount of the first feedforward amount from a total amount which is an integrated value of an amount of change in a control cycle , estimating a value obtained by multiplying the result of the subtraction by the control cycle as a second parameter for calculating the second feedforward amount, and setting the estimated second parameter as a second diagnostic index ; an eighth step of calculating an invalid amount which is an integrated value of an amount of the second feedforward amount calculated for each control cycle by the second step until the second manipulated variable is settling during a period in which the trigger variable becomes significant, the invalid amount being an integrated value of an amount of the second manipulated variable invalidated due to either output saturation in which the second manipulated variable exceeds an upper limit value of the manipulated variable or output saturation in which the second manipulated variable falls below a lower limit value of the manipulated variable; a ninth step of calculating a ratio between a total amount, which is an integrated value of each control cycle of the second feedforward amount calculated by the second step until the second manipulated variable is settling, and a total amount, which is an integrated value of each control cycle of the second feedforward amount that has not been invalidated by the output saturation, based on the invalid amount, and estimating a correction value obtained by multiplying the second diagnostic index by the ratio so that a corresponding portion of the invalid amount is distributed within a range of the second manipulated variable that is not invalidated by the output saturation , as a value for correcting the second feedforward amount, and setting the estimated value as a corrected second diagnostic index; and a tenth step of presenting the first diagnostic index and the corrected second diagnostic index.

Moreover, one configuration example of the control method of the present invention further includes an eleventh step of correcting the first parameter set for calculating the first feedforward amount in the second step to the value of the first diagnostic index, correcting the second parameter set for calculating the second feedforward amount in the second step to the value of the corrected second diagnostic index, and correcting a time constant that is set for calculating the second feedforward amount in the second step and that specifies the time for gradually converging the second feedforward amount, to a correction value of the time constant, and the ninth step is characterized in including a step of calculating the corrected second diagnostic index and calculating a value obtained by multiplying the time constant by the ratio as the correction value of the time constant .
Moreover, in one configuration example of the control method of the present invention, the second feedforward amount is calculated by [Kx2s/{(1+ATfs)(1+(2.0-A)Tfs)}]FF_X, where the second parameter is Kx2, a time constant defining a time for gradually converging the second feedforward amount is Tf, a coefficient for adjusting the time constant is A, the trigger variable is FF_X, and a Laplace operator is s.
Furthermore, in one configuration example of the control method of the present invention, the ninth step includes a step of calculating the ratio RH by Kx2/(Kx2-FF_N×dt), where FF_N is the reactive amount, dt is the control period which is a calculation period of the first manipulated variable and the first, second and third feedforward amounts, and RH is the ratio, calculating a correction value of the second parameter Kx2 by Kx2×RH as the second diagnostic index after the correction , and calculating a value Tf×RH obtained by multiplying the time constant Tf by the ratio RH as the correction value of the time constant Tf .
Moreover, in one configuration example of the control method of the present invention, the first feedforward amount is calculated by [Kx1/{(1+ATfs)(1+(2.0-A)Tfs)}]FF_X, where the first parameter is Kx1, a time constant defining a time for gradually converging the first feedforward amount is Tf, a coefficient for adjusting the time constant is A, the trigger variable is FF_X, and a Laplace operator is s.

Furthermore, one configuration example of the control method of the present invention is characterized in that it further includes a twelfth step of calculating, as a third diagnostic index, the ratio between the invalid amount and a total amount which is the integrated value of each control cycle of the second feedforward amount calculated by the second step until the second manipulated variable is settling during the period in which the trigger variable becomes a significant value, and a thirteenth step of presenting the third diagnostic index.
Moreover, one configuration example of the control method of the present invention further includes a twelfth step of performing limit processing to limit the second manipulated variable calculated in the third step to a value equal to or greater than the manipulated variable lower limit value and equal to or less than the manipulated variable upper limit value, the fourth step includes a step of outputting the limit-processed second manipulated variable to a control target, the fifth step, the sixth step, and the seventh step include a step of performing processing using the limit-processed second manipulated variable as an input, and the eighth step includes a step of outputting a second feedforward amount calculated in the second step for each control cycle until the limit-processed second manipulated variable is settling during a period in which the trigger variable becomes significant, the second manipulated variable before the limit processing being limited due to either output saturation exceeding the manipulated variable upper limit value or output saturation falling below the manipulated variable lower limit value. the ninth step includes a step of calculating the invalid amount, which is an integrated value of the second feedforward amount that has been invalidated by the output saturation, based on the invalid amount, a ratio between a total amount that is an integrated value of each control cycle of the second feedforward amount calculated in the second step until the settling of the second manipulated variable that has been limited during a period in which the trigger variable becomes significant, and a total amount that is an integrated value of each control cycle of the second feedforward amount that has not been invalidated by the output saturation, and estimating the correction value obtained by multiplying the second diagnostic index by the ratio as a value for correcting the second feedforward amount so that a corresponding portion of the invalid amount is distributed within a range of the second manipulated variable before the limit processing that is not invalidated by the output saturation, and setting the estimated value as the corrected second diagnostic index.
Moreover, one configuration example of the control method of the present invention further includes a fourteenth step of performing limit processing to limit the second manipulated variable calculated in the third step to a value equal to or greater than the manipulated variable lower limit value and equal to or less than the manipulated variable upper limit value, the fourth step includes a step of outputting the limit-processed second manipulated variable to a control target, the fifth step, the sixth step, the seventh step, and the twelfth step include a step of performing processing using the limit-processed second manipulated variable as an input, and the eighth step includes a step of outputting a value of the second feedforward variable calculated in the second step for each control cycle until the limit-processed second manipulated variable is settling during a period in which the trigger variable becomes significant, the output saturation in which the second manipulated variable before the limit processing exceeds the manipulated variable upper limit value or the output saturation in which the second manipulated variable falls below the manipulated variable lower limit value. the ninth step includes a step of calculating the invalid amount, which is an integrated value of the amount invalidated by any of the above, and the ninth step includes a step of calculating, based on the invalid amount, a ratio between a total amount that is an integrated value of each control cycle of the second feedforward amount calculated by the second step until the settling of the second operation amount that has been limited during a period in which the trigger variable becomes a significant value, and a total amount that is an integrated value of each control cycle of the second feedforward amount that has not been invalidated by the output saturation, and estimating the correction value obtained by multiplying the second diagnostic index by the ratio as a value for correcting the second feedforward amount so that a corresponding portion of the invalid amount is distributed within a range of the second operation amount before the limit processing that is not invalidated by the output saturation, and setting the estimated value as the corrected second diagnostic index.

According to the present invention, by providing a first estimation unit, a total amount calculation unit, a second estimation unit, a reactive amount calculation unit, a correction unit, and a diagnostic index presentation unit, it is possible to obtain diagnostic indexes for the first feedforward amount required to suppress step disturbances and the second feedforward amount required to suppress impulse disturbances based on the results of execution of disturbance recovery control, and it is possible to rationally diagnose the validity of the first feedforward amount and the second feedforward amount.

In addition, the present invention provides a correction unit, making it possible to realize an adaptive readjustment function.

FIG. 1 is a block diagram showing the configuration of a control device according to a first embodiment of the present invention. FIG. 2 is a block diagram of a control system according to a first embodiment of the present invention. FIG. 3 is a flowchart illustrating the operation of the control device according to the first embodiment of the present invention. FIG. 4 is a flowchart illustrating the operation of the control device according to the first embodiment of the present invention. FIG. 5 is a diagram showing an example of a change in the feedforward amount according to the first embodiment of the present invention. FIG. 6 is a diagram showing an example of a change in the feedforward amount according to the first embodiment of the present invention. FIG. 7 is a diagram showing an example of a change in the feedforward amount according to the first embodiment of the present invention. FIG. 8 is a diagram showing a simulation result in the case where feedforward control is not executed and only feedback control is executed in the first embodiment of the present invention. FIG. 9 is a diagram showing a simulation result when feedforward control and feedback control are executed in the first embodiment of the present invention. FIG. 10 is a diagram showing a simulation result of the feedforward amount when feedforward control and feedback control are executed in the first embodiment of the present invention. FIG. 11 is a diagram showing a simulation result when feedforward control and feedback control are executed in the first embodiment of the present invention. FIG. 12 is a diagram showing a simulation result when feedforward control and feedback control are executed in the first embodiment of the present invention. FIG. 13 is a block diagram showing the configuration of a control device according to a second embodiment of the present invention. FIG. 14 is a flowchart illustrating the operation of the control device according to the second embodiment of the present invention. FIG. 15 is a diagram showing an example of a presented diagnostic index in the second embodiment of the present invention. FIG. 16 is a block diagram showing an example of the configuration of a computer that realizes the control device according to the first and second embodiments of the present invention. FIG. 17 is a block diagram showing the configuration of the heating device. FIG. 18 is a block diagram of a feedback+feedforward control system. FIG. 19 is a diagram showing an example of a change in the added amount of the manipulated variable in the feedback+feedforward control.

[Principle 1 of the invention]
The present invention is applied to a disturbance recovery response, which is particularly applicable to the technique proposed in Patent Document 3. Disturbances to which the present invention is applied are roughly divided into two types: impulse disturbances and step disturbances.

An impulse disturbance is a disturbance in which the actual operating amount MV_F at the time of settling hardly changes before and after the disturbance recovery response, and is a temporary, shock-like disturbance. A step disturbance is a disturbance in which the actual operating amount MV_F at the time of settling changes significantly before and after the disturbance recovery response, and is a disturbance in which the equilibrium point itself, known as the settling state, changes. The technology proposed in Patent Document 3 is particularly suitable for impulse disturbances.

If there is only an impulse disturbance, the feedforward amount MV_X can be optimized using the total amount of change ΔMV_imp in the actual operation amount MV_F in disturbance recovery control by feedback control alone (control that returns the control amount PV to the set value SP) as a guide. Also, if there is only a step disturbance, the feedforward amount MV_X can be optimized using the actual operation amount difference ΔMV_stp before and after the disturbance recovery response by feedback control alone as a guide. Disturbances in which both impulse disturbances and step disturbances occur simultaneously (referred to as a mixed disturbance in this invention) are particularly difficult to adjust.

As a result of extensive research, the inventors have discovered that the feedforward amount MV_X can be estimated by the following steps (I) and (II), and have proposed a control method that follows steps (I) and (II) (Patent Application No. 2020-016891).

(I) At least execute disturbance recovery control using feedback control (or disturbance recovery control using only feedback control), and estimate the feedforward amount MV_X1 required for the step disturbance based on the actual manipulated variable difference ΔMV_stp before and after the disturbance recovery response.

(II) In the disturbance recovery control executed in (I) above, the total amount of change ΔMV_all in the actual manipulated variable MV_F is calculated, and the feedforward amount MV_X2 required for the impulse disturbance is estimated based on the total amount of change ΔMV_imp in the actual manipulated variable MV_F obtained by subtracting the total amount of feedforward amount MV_X1 required for the step disturbance estimated in (I) MV_X1_all.

The above steps (I) and (II) make it possible to estimate the feedforward amount MV_X appropriately. However, because the feedforward amount as shown in FIG. 19 results in an operation that temporarily fluctuates the actual operation amount MV_F significantly, there is a high possibility that output saturation will occur that exceeds the upper limit OH or lower limit OL of the actual operation amount MV_F. When output saturation occurs, the expected feedforward amount cannot be secured. In other words, it is particularly difficult to diagnose a case where the feedforward amount required for an impulse disturbance is affected by output saturation.

After extensive research, the inventors have discovered that the feedforward amount MV_X can be monitored, diagnosed, and readjusted approximately appropriately by following the steps (III), (IV), and (V) below. Note that this invention is premised on the fact that the timing of applying the disturbance is known, and therefore the timing of applying the feedforward operation can be automatically determined. This invention is also premised on the fact that, by employing, for example, PID control as feedback control, the parameter Tf for the time at which the feedforward amount MV_X converges can be automatically and uniquely determined based on the PID parameters, which are controller parameters. In other words, in this invention, it is only the polarity and magnitude of the disturbance that change without achieving reproducibility.

(III) Disturbance recovery control is performed using feedforward control and feedback control for step disturbances and impulse disturbances, and an index is calculated to diagnose the appropriateness of the feedforward amount MV_X1 required for the step disturbance based on the actual operation amount difference ΔMV_stp before and after the disturbance recovery response. Theoretically, the appropriate feedforward amount MV_X1 is proportional to the actual operation amount difference ΔMV_stp.

(IV) An index for diagnosing the appropriateness of the feedforward amount MV_X2 required for the impulse disturbance is calculated based on the total amount of change ΔMV_imp of the actual control amount MV_F obtained by subtracting the total amount of feedforward amount MV_X1 required for the step disturbance that can be assumed based on the diagnostic index obtained in the procedure (III) above. Theoretically, the appropriate feedforward amount MV_X2 is roughly proportional to the total amount of change ΔMV_imp of the actual control amount MV_F.

(V) In the disturbance recovery control executed in the procedure (III) above, the correction amount of the feedforward amount MV_X2, which is the diagnostic index obtained in the procedure (IV) above, is calculated as a corrected diagnostic index, based on the ratio RH calculated from the total amount of feedforward amounts invalidated due to output saturation (invalid amount FF_N) and the feedforward amount MV_X2 for impulse disturbances, so that the equivalent amount of the invalid amount FF_N is distributed within a range that is not invalidated due to output saturation.

The above steps (III), (IV), and (V) allow a rational diagnosis of the validity of the feedforward amount MV_X (MV_X1+MV_X2H). In practice, it is preferable to make a statistically reliable judgment while repeating disturbance recovery control and monitoring, and to appropriately correct the feedforward amount MV_X as necessary.

[Principle 2 of the Invention]
As described above, when output saturation is assumed with versatility in mind, it is preferable to monitor not only the feedforward amount MV_X1 required for a step disturbance and the feedforward amount MV_X2 required for an impulse disturbance individually, but also the ratio RX regarding the reactive amount FF_N, which makes it possible to monitor changes in the effectiveness of the feedforward control.

[First embodiment]
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 control device according to a first embodiment of the present invention. This embodiment corresponds to the above-mentioned principle 1 of the invention. The control device includes a control amount calculation unit 1 that calculates a basic control amount MV (first control amount) by PID calculation using a set value SP and a controlled amount PV as inputs, a feedforward calculation unit 2 that calculates the sum of a feedforward amount MV_X1 (first feedforward amount) required to suppress a step disturbance and a feedforward amount MV_X2 (second feedforward amount) required to suppress an impulse disturbance as a feedforward amount MV_X (third feedforward amount) in response to an input of a trigger variable FF_X that is a significant value before the application of the disturbance and a non-significant value after the application of the disturbance, and a feedforward execution unit 3 that adds the feedforward amount MV_X to the basic control amount MV calculated by the control amount calculation unit 1 to obtain an actual control amount MV_F (second control amount).

The control device also includes a step correspondence estimation unit 4 (first estimation unit) that estimates a parameter Kx1 (first parameter) for calculating the feedforward amount MV_X1 as a first diagnostic index based on the actual operation amount difference ΔMV_stp before and after the disturbance recovery response when the trigger variable FF_X becomes a significant value, and a parameter Kx1 that is the same as the value estimated by the step correspondence estimation unit 4 is set in the feedforward calculation unit 2, and when the trigger variable FF_X becomes a significant value, the feedforward amount MV_X1 is calculated based on the parameter Kx1 that has been set. The system includes a total amount calculation unit 5 that calculates the total amount MV_X1_all of the feedforward amount MV_X1 when it is assumed that MV_X1 is output, and an impulse response estimation unit 6 (second estimation unit) that estimates a parameter Kx2 (second parameter) for calculating the feedforward amount MV_X2 as a second diagnostic index based on the result ΔMV_imp of subtracting the total amount MV_X1_all of the feedforward amount MV_X1 from the total amount of change ΔMV_all of the actual operation amount MV_F during the period in which the trigger variable FF_X becomes a significant value.

Furthermore, the control device includes an invalid amount calculation unit 7 that calculates an invalid amount FF_N, which is the total amount of the feedforward amount MV_X2 calculated by the feedforward calculation unit 2 during the period when the trigger variable FF_X becomes a significant value that is invalidated due to either output saturation in which the actual operation amount MV_F exceeds the operation amount upper limit value OH or output saturation in which the actual operation amount MV_F falls below the operation amount lower limit value OL, and a calculation unit 8 that calculates a calculation unit 9 that calculates a calculation unit 100 of the total amount of the feedforward amount MV_X2 calculated by the feedforward calculation unit 2 during the period when the trigger variable FF_X becomes a significant value and the total amount of the feedforward amount MV_X2 that was not invalidated due to output saturation. The system includes an impulse-responsive correction unit 8 that calculates a ratio based on the invalid amount FF_N, estimates a parameter for correcting the feedforward amount MV_X2 based on the ratio as a corrected second diagnostic index so that a portion of the invalid amount FF_N is distributed within the range of the actual operating amount MV_F that is not invalidated by output saturation, an estimation result output unit 9 that outputs the estimation results of the step-responsive estimation unit 4 and the impulse-responsive correction unit 8, a diagnostic index presentation unit 10 that presents the first diagnostic index and the corrected second diagnostic index to the operator, and an adaptive correction unit 11 that corrects the settings of the feedforward calculation unit 2 based on the diagnostic index.

Furthermore, the control device is equipped with a limit processing unit 12 that performs limit processing to limit the actual operating volume MV_F calculated by the feedforward execution unit 3 to a value greater than or equal to the operating volume lower limit value OL and less than or equal to the operating volume upper limit value OH, and an operating volume output unit 13 that outputs the limited-processed actual operating volume MV_F' (second operating volume) to the controlled object.
2 is a block diagram of the control system of this embodiment, in which P indicates a controlled object.

Next, the operation of the control device of this embodiment will be described with reference to Figures 3 and 4. The set value SP (e.g., temperature set value) is set by an operator of the control device, etc., and input to the operation amount calculation unit 1 (Figure 3, step S100).

The controlled variable PV (e.g., a temperature measurement value) is measured by a measuring device (not shown) (e.g., a temperature sensor that measures the temperature of the heated object) and input to the manipulated variable calculation unit 1 (step S101 in FIG. 3).

The manipulated variable calculation unit 1 receives the set value SP and the controlled variable PV as input, and calculates the basic manipulated variable MV by performing a PID calculation, for example, using the following transfer function formula, so that the controlled variable PV coincides with the set value SP (step S102 in FIG. 3).
MV=(100/Pb) {1+(1/Tis)+Tds}(SP-PV)
...(5)
Pb is the proportional band, Ti is the integral time, Td is the differential time, and s is the Laplace operator.

The feedforward calculation unit 2 calculates the feedforward amount MV_X when feedforward control is executed, but if the trigger variable FF_X, which is 1 (significant value) before the application of the disturbance and 0 (insignificant value) after the application of the disturbance, is 0 (NO in step S103 in FIG. 3), it is assumed that only feedback control is performed and feedforward control is not executed, and the feedforward amount MV_X is set to 0 (step S104 in FIG. 3).

The feedforward execution unit 3 calculates an actual manipulated variable MV_F by adding the feedforward variable MV_X calculated by the feedforward calculation unit 2 to the basic manipulated variable MV calculated by the manipulated variable calculation unit 1 (step S105 in FIG. 3).
MV_F=MV+MV_X...(6)

Here, since MV_X = 0, MV_F = MV. The limit processing unit 12 performs lower limit processing to limit the actual manipulated variable MV_F calculated by the feedforward executing unit 3 to a value equal to or greater than a predetermined manipulated variable lower limit value OL, and upper limit processing to limit the actual manipulated variable MV_F to a value equal to or less than a predetermined manipulated variable upper limit value OH (step S106 in FIG. 3).
IF MV_F<OL THEN MV_F'=OL...(7)
IF MV_F>OH THEN MV_F'=OH...(8)
That is, when the actual manipulated variable MV_F is smaller than the manipulated variable lower limit OL, the limit processing unit 12 sets the actual manipulated variable MV_F'=OL, and when the actual manipulated variable MV_F is larger than the manipulated variable upper limit OH, the limit processing unit 12 sets the actual manipulated variable MV_F'=OH.

The manipulated variable output unit 13 outputs the actual manipulated variable MV_F' that has been subjected to limit processing by the limit processing unit 12 to the controlled object (step S107 in FIG. 3). The actual manipulated variable MV_F' is output to an operating unit (not shown) such as a heater or a valve. In the case of a heater, the actual output destination of the actual manipulated variable MV_F' is a power regulator (not shown) that supplies power to the heater.

The step response estimation unit 4 and the impulse response estimation unit 6 store the actual operation amount MV_F' calculated by the feedforward execution unit 3 and processed by the limit processing unit 12 together with the time (step S108 in Figure 3).

The control device executes steps S100 to S108 in FIG. 3 for each control cycle until control is terminated, for example, by an operator's instruction (YES in step S109 in FIG. 3).

Next, we will explain the operation when the trigger variable FF_X becomes 1 (a significant value). In this embodiment, it is assumed that the timing of applying the disturbance is known, and therefore the timing of executing feedforward control can be automatically determined. In a system to which the control device of this embodiment is applied, the trigger variable FF_X = 1 is automatically input from an external device to the control device at a specified timing in order to suppress disturbances that are anticipated during control.

For example, in a pharmaceutical manufacturing device, there is a situation where the temperature inside the pharmaceutical manufacturing furnace fluctuates when the door of the furnace is opened. In this case, the control device (external device) that controls the temperature of the furnace sends a trigger variable FF_X = 1 to the control device of this embodiment at a point in time before the door of the furnace opens (the timing of applying the disturbance).

Similarly, in a reflow furnace with a constant set value SP (temperature set value), there is a situation where the temperature fluctuates as printed circuit boards to be soldered are periodically inserted. In this case, the control device (external device) that controls the transportation of the printed circuit boards sends a trigger variable FF_X = 1 to the control device of this embodiment at a point in time prior to the timing at which the printed circuit boards are inserted into the reflow furnace (timing at which the disturbance is applied).

Furthermore, the external device sets the trigger variable FF_X to 0 (insignificant value) a predetermined time after the application of the disturbance ends. The timing for setting the trigger variable FF_X to 0 needs to be set to a timing later than the timing at which the actual manipulated variable MV_F′ is settled after the application of the disturbance.
The extent to which the trigger variable FF_X should be set to 1 relative to the timing of application of the disturbance will be described later.

When the trigger variable FF_X changes from 0 to 1 (YES in step S103), the feedforward calculation unit 2 calculates the feedforward amount MV_X1 required to suppress the step disturbance using the following equation (9) to execute feedforward + feedback control (step S110 in FIG. 4). At the same time as calculating this feedforward amount MV_X1, the feedforward calculation unit 2 calculates the feedforward amount MV_X2 required to suppress the impulse disturbance using the following equation (10) (step S111 in FIG. 4).

The feedforward amount MV_X1 required for suppressing the step disturbance is calculated as follows:
MV_X1
= [Kx1/{(1+ATfs)(1+(2.0-A)Tfs)}]FF_X
... (9)

The feedforward amount MV_X2 required for suppressing the impulse disturbance is calculated as follows:
MV_X2
= [Kx2s/{(1+ATfs)(1+(2.0-A)Tfs)}]FF_X
...(10)

In equations (9) and (10), Tf is a parameter (time constant) that specifies the time for gradually converging the feedforward amounts MV_X1 and MV_X2. The time constant Tf can be set in advance based on information about the feedback control system, etc.

In the formulas (9) and (10), A is a coefficient (A is a real number greater than 0) that adjusts the balance of the time constant Tf. In this embodiment, A=1.0.
The parameter Kx1 is a parameter for calculating the feedforward amount MV_X1 required for suppressing the step disturbance, and is substantially a target value of the amount of addition or subtraction of the feedforward portion with respect to the basic manipulated variable MV. According to the formula (9), the feedforward amount MV_X1 gradually converges from zero to the value of the parameter Kx1.

Furthermore, Kx2 in formula (10) is a parameter for calculating the feedforward amount MV_X2 required to suppress impulse disturbances, and is essentially a target value for the total amount of additions and subtractions of the feedforward components to the basic operating amount MV (the integrated value of the additions and subtractions for each control cycle). According to formula (10), after the total amount (the integrated value for each control cycle) of the feedforward amount MV_X2 approaches the value of the parameter Kx2, the feedforward amount MV_X2 itself gradually converges to a zero value. Formulas (9) and (10) are stored in the feedforward calculation unit 2.

Next, after calculating the feedforward amounts MV_X1 and MV_X2, the feedforward calculation unit 2 calculates the feedforward amount MV_X by adding the feedforward amounts MV_X1 and MV_X2 as shown in the following equation (step S112 in FIG. 4).
MV_X=MV_X1+MV_X2...(11)

In this embodiment, it is sufficient to execute disturbance recovery control using at least impulse disturbance-responsive feedforward control and feedback control, and it is not necessary to execute feedforward control for step disturbances. When parameter Kx1 is set to 0 and parameter Kx2 is set to a value other than 0, the feedforward amount MV_X1 becomes 0, so that impulse disturbance-responsive feedforward control and feedback control are executed as disturbance recovery control. Whether or not to set MV_X1 = 0 can be determined appropriately depending on the disturbance.

The processing in steps S113 to S115 in Fig. 4 is the same as the processing in steps S105 to S107. The step response estimator 4, the impulse response estimator 6, the reactive amount calculator 7, and the impulse response corrector 8 store the actual manipulated variable MV_F' calculated by the feedforward execution unit 3 and processed by the limit processor 12, and the feedforward amounts MV_X2 and MV_X calculated by the feedforward calculator 2, together with the time (step S116 in Fig. 4).
In this manner, when the trigger variable FF_X is 1, the control device executes the processes of steps S100 to S102 and S110 to S116 for each control period.

Next, when the step correspondence estimation unit 4 determines that the actual operation amount MV_F' has settled in the disturbance recovery control in which the trigger variable FF_X has become 1 (YES in step S117 in FIG. 4), it calculates the actual operation amount difference ΔMV_stp before and after the disturbance recovery response (step S118 in FIG. 4). The actual operation amount difference ΔMV_stp is the difference between the settling value of the actual operation amount MV_F' when it is determined in step S117 that it has settled and the actual operation amount MV_F' before the application of the disturbance (the settling value of the actual operation amount MV_F' immediately before the trigger variable FF_X becomes 1).

Then, the step correspondence estimator 4 estimates, as the diagnostic index Kx1new, an appropriate value of the parameter Kx1 for calculating the feedforward amount MV_X1 necessary for suppressing the step disturbance (step S119 in FIG. 4).
Kx1new=ΔMV_stp...(12)
That is, in this embodiment, the step correspondence estimator 4 sets the actual manipulated variable difference ΔMV_stp as the diagnostic index Kx1new as it is.

The estimation result output unit 9 outputs the value of the diagnostic index Kx1new estimated by the step correspondence estimation unit 4 to the diagnostic index presentation unit 10 and the adaptive correction unit 11. The diagnostic index presentation unit 10 presents the value of the diagnostic index Kx1new estimated by the step correspondence estimation unit 4 to the operator (step S120 in FIG. 4).

The adaptive correction unit 11 corrects the value of the parameter Kx1 set in the feedforward calculation unit 2 to the value of the diagnostic index Kx1new estimated by the step correspondence estimation unit 4 (Figure 4, step S121).

However, automatic correction of the parameter Kx1 by the adaptive correction unit 11 is not a necessary component of the present invention. For example, the operator may manually correct the value of the parameter Kx1 after confirming the value of the diagnostic index Kx1new displayed on the screen by the diagnostic index presentation unit 10. Alternatively, the correction of the parameter Kx1 itself may be put on hold for the time being in order to make a statistically reliable judgment.

Next, the total amount calculation unit 5 calculates the total amount MV_X1_all (the integrated value of the addition and subtraction amounts for each control cycle) of the feedforward amount MV_X1 until the actual operation amount MV_F' is settled, assuming that the parameter Kx1, which is the same as the value estimated by the step correspondence estimation unit 4, has already been set in the feedforward calculation unit 2 and that the feedforward amount MV_X1 has been output based on the set parameter Kx1 when the trigger variable FF_X becomes 1 (FIG. 4, step S122).

In other words, since the diagnostic index Kx1new is estimated by the step correspondence estimation unit 4 after the trigger variable FF_X becomes 1 and the actual operation amount MV_F' is settled, it is possible that the parameter Kx1 with the same value as the diagnostic index Kx1new has not been set in the feedforward calculation unit 2 at the time when the trigger variable FF_X becomes 1. In response to this, the total amount calculation unit 5 calculates the total amount MV_X1_all until the actual operation amount MV_F' is settled, assuming that the parameter Kx1 with the same value as the diagnostic index Kx1new has been set in the feedforward calculation unit 2 before the trigger variable FF_X becomes 1, and the feedforward amount MV_X1 is calculated and output by the processing of step S110 when the trigger variable FF_X becomes 1.

The impulse response estimation unit 6 calculates the total change amount ΔMV_all (the integrated value of the change amount in each control cycle) of the actual operation amount MV_F' in the disturbance recovery control when the trigger variable FF_X becomes 1, based on the stored time series data of the actual operation amount MV_F' (the set value of the actual operation amount MV_F' just before the trigger variable FF_X becomes 1) before the disturbance is applied, based on the time series data of the actual operation amount MV_F' (step S123 in FIG. 4).

Next, the impulse-responsive estimator 6 calculates the total amount of change ΔMV_imp by subtracting the total amount MV_X1_all of the feedforward amount MV_X1 calculated by the total amount calculator 5 from the total amount of change ΔMV_all of the actual manipulated variable MV_F' calculated in step S123 (step S124 in FIG. 4).
ΔMV_imp=ΔMV_all−MV_X1_all (13)

Furthermore, the impulse response estimation unit 6 estimates, as a diagnostic index Kx2new, an appropriate value of the parameter Kx2 for calculating the feedforward amount MV_X2 necessary for suppressing the impulse disturbance (step S125 in FIG. 4).
Kx2new=ΔMV_imp×dt...(14)

In the formula (14), dt is a control period (a calculation period of the basic manipulated variable MV and the feedforward variables MV_X1, MV_X2, and MV_X) and is expressed in seconds.
Next, in the disturbance recovery control in which the trigger variable FF_X becomes 1, when the actual control input MV_F' settles, the invalid amount calculation unit 7 calculates an invalid amount FF_N which is the total amount of the feedforward amount MV_X2 calculated by the feedforward calculation unit 2 until the actual control input MV_F' settles, which is invalidated due to either output saturation in which the actual control input MV_F exceeds the control input upper limit value OH or output saturation in which the actual control input MV_F falls below the control input lower limit value OL (step S126 in FIG. 4).

Specifically, in the case of output saturation where the actual manipulated variable MV_F exceeds the manipulated variable upper limit value OH, the reactive quantity calculation unit 7 may take the integrated value of the positive difference of the difference MV_X-OH between the feedforward variable MV_X obtained for each control cycle and the manipulated variable upper limit value OH as the reactive quantity FF_N. In addition, in the case of output saturation where the actual manipulated variable MV_F is below the manipulated variable lower limit value OL, the reactive quantity calculation unit 7 may take the integrated value of the negative difference of the difference MV_X-OL between the feedforward variable MV_X obtained for each control cycle and the manipulated variable upper limit value OH as the reactive quantity FF_N.

In addition, in the case of output saturation, not only the feedforward amount MV_X2 but also the basic operation amount MV or the feedforward amount MV_X1 may be partially invalidated. However, in the feedforward + feedback control of the present invention, most of the steep rise or fall of the actual operation amount MV_F that causes output saturation is due to the feedforward amount MV_X, and most of that is due to the feedforward amount MV_X2. The basic operation amount MV and the feedforward amount MV_X1 change later than the feedforward amount MV_X2. Therefore, the invalid amount FF_N may be calculated simply by a simple comparison of the feedforward amount MV_X and the operation amount upper limit values OH and OL as described above.

Next, the impulse-responsive correction unit 8 calculates the ratio RH between the total amount Kx2 of the feedforward amount MV_X2 calculated by the feedforward calculation unit 2 until the actual operating amount MV_F' is settled and the total amount of the feedforward amount MV_X2 that has not been invalidated due to output saturation among the total amount Kx2, based on the invalid amount FF_N, as shown in the following equation (step S127 in FIG. 4).
RH=Kx2/(Kx2-FF_N×dt)...(15)

Note that the total amount of the feedforward amount MV_X2 is equal to the parameter Kx2 set in the feedforward calculation unit 2, so in the calculation of equation (15), the feedforward amount MV_X2 is not calculated by integrating it, but Kx2 is used as the total amount.

Then, the impulse response correction unit 8 calculates a correction amount of the feedforward amount MV_X2 as a corrected diagnostic index so that the equivalent of the invalid amount FF_N is distributed within the range of the actual manipulated variable MV_F that is not invalidated by the output saturation. More specifically, the impulse response correction unit 8 estimates a correction value Kx2H of the parameter Kx2 by equation (16) based on the diagnostic index Kx2new and the ratio RH estimated by the impulse response estimation unit 6. In addition, the impulse response correction unit 8 estimates a correction value TfH of the time constant Tf by equation (17) based on the time constant Tf and the ratio RH set in the feedforward calculation unit 2 (step S128 in FIG. 4).
Kx2H=Kx2new×RH...(16)
TfH=Tf×RH...(17)

The estimation result output unit 9 outputs the corrected diagnostic indexes Kx2H and TfH values estimated by the impulse response correction unit 8 to the diagnostic index presentation unit 10 and the adaptive correction unit 11.
The diagnostic index presenting unit 10 presents the values of the diagnostic indexes Kx2H and TfH estimated by the impulse-based correction unit 8 to the operator (step S129 in FIG. 4).

The adaptive correction unit 11 corrects the value of the parameter Kx2 set in the feedforward calculation unit 2 to the diagnostic index Kx2H estimated by the impulse response correction unit 8, and corrects the value of the time constant Tf set in the feedforward calculation unit 2 to the diagnostic index TfH estimated by the impulse response correction unit 8 (step S130 in FIG. 4).

As in the case of the parameter Kx1, the automatic correction of the parameter Kx2 and the time constant Tf by the adaptive correction unit 11 is not an essential component of the present invention. For example, the operator may manually correct the values of the parameter Kx2 and the time constant Tf after having confirmed the values of the diagnostic indexes Kx2H and TfH displayed on the screen by the diagnostic index presenting unit 10. Alternatively, the correction of the parameter Kx2 and the time constant Tf itself may be suspended for the time being in order to perform a statistically reliable judgment.
The processes of steps S118 to S130 need only be performed once when the actual manipulated variable MV_F' has stabilized.

Figure 5 shows an example of the change in the feedforward amount MV_X1, Figure 6 shows an example of the change in the feedforward amount MV_X2, and Figure 7 shows an example of the change in the feedforward amount MV_X. In the examples of Figures 5 to 7, Kx1 = 20.0, Kx2 = 3304.0, and Tf = 15.0 sec. The total amount (integrated value for each control cycle) mentioned above is the amount equivalent to the area enclosed by the curves in Figures 5 to 7.

The effect of this embodiment will be verified by a simulation below. In the following example, the controlled object is a control system that can be approximated by a first-order lag transfer function with a process gain of 10.0, a process time constant of 400.0 sec, and a process dead time of 20.0 sec. In other words, the model equation Gp of the controlled object can be written as follows:
Gp=10.0exp(-20.0s)/(1+400.0s)...(18)

In addition, the upper limit value OH of the actual manipulated variable MV_F is set to 75% so that output saturation occurs due to the feedforward control, which means that the amount exceeding 75% is invalidated.
The PID parameters set in the operation amount calculation unit 1 are proportional band Pb=60%, integral time Ti=120.0 sec, and differential time Td=10.0 sec. The control period dt is 1.0 sec.

The start timing of feedforward control, i.e., the timing at which the trigger variable FF_X changes from 0 to 1, can be set based on the differential time Td. Specifically, it is appropriate that the start timing is αTd before the time point at which the disturbance is applied (the coefficient α is a real number greater than 0, for example 0.7). When the differential time Td = 10.0 sec., the start timing of feedforward control is 7.0 sec. before the time point at which the disturbance is applied. However, the coefficient α is a value that can be fine-tuned as appropriate.

Similarly, the time constant Tf can be set based on the differential time Td. Specifically, it is appropriate for Tf to be βTd (coefficient β is a real number greater than 0, e.g., 0.4). When differential time Td is 10.0 sec., the time constant Tf is 4.0 sec. However, coefficient β is a value that can be fine-tuned as appropriate.

Figure 8 shows an example of the change in the controlled variable PV and the actual manipulated variable MV_F' (= manipulated variable MV) when temperature control is performed using only feedback control without feedforward control. This Figure 8 shows a reference example when feedforward control is not performed, and shows the simulation results of the disturbance recovery response by feedback control when a mixed disturbance is applied at 100 seconds. Because the mixed disturbance includes a step disturbance, there is a noticeable change in the actual manipulated variable MV_F' (= manipulated variable MV) at the time of settling before and after the disturbance recovery response.

Figure 9 shows the simulation results of the disturbance recovery response by feedforward control and feedback control when a mixed disturbance is applied at 100 sec., and Figure 10 shows the simulation results of the feedforward amount MV_X in the case of Figure 9. The examples of Figures 9 and 10 show the case where the parameters Kx1 = 15.0, Kx2 = 870.5, and time constant Tf = 4.6 sec. are preset in the feedforward calculation unit 2.

In the example of Figures 9 and 10, the actual control amount MV_F' before the disturbance application is 30.0%, while the set value of the actual control amount MV_F' after the disturbance recovery response is 45.0%, so the actual control amount difference ΔMV_stp = 15.0%. The step correspondence estimation unit 4 estimates the diagnostic index Kx1new = 15.0 using equation (12) (step S119 in Figure 4).

In the example of Figures 9 and 10, the total change amount ΔMV_imp obtained by subtracting the total amount of feedforward amount MV_X1 from the total change amount ΔMV_all of the actual manipulated variable MV_F' is 752.4%. The impulse response estimation unit 6 estimates the diagnostic index Kx2new = 752.4 using equation (14) (step S125 in Figure 4). The invalid amount calculation unit 7 calculates the invalid amount FF_N = 118.1% (step S126 in Figure 4).

The impulse-compliant correction unit 8 calculates the ratio RH = 870.5/(870.5-118.1 x 1.0) = 1.157 using equation (15) (step S127 in FIG. 4). Furthermore, the impulse-compliant correction unit 8 estimates the corrected diagnostic index Kx2H = 752.4 x 1.157 = 870.5 using equation (16), and estimates the corrected diagnostic index TfH = 4.0 x 1.157 = 4.6 sec. using equation (17) (step S128 in FIG. 4).

In the example of Figures 9 and 10, the values of the parameters Kx1, Kx2, and Tf that were previously set in the feedforward calculation unit 2 are equal to the values of the estimated diagnostic indices Kx1new, Kx2H, and TfH. Therefore, the operator can diagnose that the feedforward amount MV_X is appropriate.

Figure 11 shows the simulation results of the disturbance recovery response by feedforward control and feedback control when a mixed disturbance with a larger amount of application than in Figures 9 and 10 is applied at 100 sec. As in Figures 9 and 10, the example in Figure 11 shows a case where the parameters Kx1 = 15.0, Kx2 = 870.5, and time constant Tf = 4.6 sec. are preset in the feedforward calculation unit 2. The amount of disturbance application is greater than in Figures 9 and 10, and the actual operation amount MV_F' at the time of settling before the application of the disturbance is also higher, so the control result is also different from that in Figure 9.

In the example of FIG. 11, the actual control amount MV_F' before the disturbance application is 35.0%, while the set value of the actual control amount MV_F' after the disturbance recovery response is 55.0%, so the actual control amount difference ΔMV_stp = 20.0%. The step correspondence estimation unit 4 estimates the diagnostic index Kx1new = 20.0 using equation (12) (step S119 in FIG. 4).

In the example of FIG. 11, the total change amount ΔMV_imp obtained by subtracting the total amount of feedforward amount MV_X1 from the total change amount ΔMV_all of the actual manipulated variable MV_F' is 768.3%. The impulse response estimation unit 6 estimates the diagnostic index Kx2new to be 768.3 using equation (14) (step S125 in FIG. 4). The invalid amount calculation unit 7 calculates the invalid amount FF_N to be 220.0% (step S126 in FIG. 4).

The impulse-compliant correction unit 8 calculates the ratio RH = 870.5/(870.5-220.0 x 1.0) = 1.342 using equation (15) (step S127 in FIG. 4). Furthermore, the impulse-compliant correction unit 8 estimates the corrected diagnostic index Kx2H = 768.3 x 1.342 = 1031.0 using equation (16), and estimates the corrected diagnostic index TfH = 4.0 x 1.342 = 5.4 sec. using equation (17) (step S128 in FIG. 4).

In the example of FIG. 11, as the amount of disturbance applied increases and the actual operating amount MV_F' at the time of settling before the disturbance is applied increases, the values of the estimated diagnostic indexes Kx1new, Kx2H, and TfH become larger than the values of the parameters Kx1, Kx2, and Tf that were preset in the feedforward calculation unit 2. Therefore, the operator can diagnose that it is appropriate to increase the feedforward amount MV_X.

Figure 12 shows the simulation results of the disturbance recovery response by feedforward control and feedback control when a mixed disturbance is applied at 100 sec. with a smaller amount than in Figures 9 and 10. As in Figures 9 and 10, the example in Figure 12 shows a case where the parameters Kx1 = 15.0, Kx2 = 870.5, and time constant Tf = 4.6 sec. are preset in the feedforward calculation unit 2. The amount of disturbance applied is smaller than in Figures 9 and 10, and the actual operation amount MV_F' at the time of settling before the disturbance application is also lower, so the control result is also different from that in Figure 9.

In the example of FIG. 12, the actual control amount MV_F' before the disturbance application is 22.5%, while the set value of the actual control amount MV_F' after the disturbance recovery response is 35.0%, so the actual control amount difference ΔMV_stp = 12.5%. The step correspondence estimation unit 4 estimates the diagnostic index Kx1new = 12.5 using equation (12) (step S119 in FIG. 4).

In the example of FIG. 11, the total change amount ΔMV_imp obtained by subtracting the total amount of feedforward amount MV_X1 from the total change amount ΔMV_all of the actual manipulated variable MV_F' is 720.3%. The impulse response estimation unit 6 estimates the diagnostic index Kx2new to be 720.3 using equation (14) (step S125 in FIG. 4). The invalid amount calculation unit 7 calculates the invalid amount FF_N to be 89.4% (step S126 in FIG. 4).

The impulse-compliant correction unit 8 calculates the ratio RH = {870.5/(870.5-89.4)} x 1.0 = 1.114 using equation (15) (step S127 in FIG. 4). Furthermore, the impulse-compliant correction unit 8 estimates the corrected diagnostic index Kx2H = 720.3 x 1.114 = 802.4 using equation (16), and estimates the corrected diagnostic index TfH = 4.0 x 1.114 = 4.5 sec. using equation (17) (step S128 in FIG. 4).

In the example of FIG. 12, as the amount of disturbance applied decreases and the actual operating amount MV_F' at the time of settling before the disturbance is applied decreases, the values of the estimated diagnostic indicators Kx1new, Kx2H, and TfH become smaller than the values of the parameters Kx1, Kx2, and Tf that were preset in the feedforward calculation unit 2. Therefore, the operator can diagnose that it is appropriate to reduce the feedforward amount MV_X.

As described above, in this embodiment, diagnostic indices for the feedforward amounts MV_X1 and MV_X2 can be obtained, and the validity of the feedforward amounts MV_X1 and MV_X2 can be reasonably diagnosed. In addition, in this embodiment, an adaptive readjustment function can be realized by providing an adaptive correction unit 11 that corrects the parameters Kx1, Kx2, and Tf based on the diagnostic indices.

[Second embodiment]
Next, a second embodiment of the present invention will be described. FIG. 13 is a block diagram showing the configuration of a control device according to the second embodiment of the present invention, and the same components as those in FIG. 1 are given the same reference numerals. This embodiment is an example corresponding to the above-mentioned principle 2 of the present invention. The control device of this embodiment includes an operation amount calculation unit 1, a feedforward calculation unit 2, a feedforward execution unit 3, a step-response estimation unit 4, a total amount calculation unit 5, an impulse-response estimation unit 6, a reactive amount calculation unit 7, an impulse-response correction unit 8, an estimation result output unit 9, a diagnostic index presentation unit 10a, a limit processing unit 12, an operation amount output unit 13, and an index ratio calculation unit 14 that calculates, as a third diagnostic index, a ratio RX between the reactive amount FF_N and the total amount of the feedforward amount MV_X2 calculated by the feedforward calculation unit 2 during a period in which the trigger variable FF_X becomes a significant value.

Next, the operation of the control device of this embodiment will be described with reference to Fig. 14. The operation when the trigger variable FF_X remains at 0 and only the feedback control is executed is as shown in Fig. 3, so the description will be omitted.
The processes in steps S110 to S119 when the trigger variable FF_X becomes 1 are the same as those in the first embodiment.

The diagnostic index presenting unit 10a presents to the operator the value of the diagnostic index Kx1new estimated by the step correspondence estimating unit 4, as in the first embodiment (FIG. 14, step S120a). In this embodiment, the diagnostic index Kx1new is displayed in a time series graph so that the operator can easily make some kind of judgment, including statistical reliability, based on the change over time in the diagnostic index Kx1new.

The processes in steps S122 to S128 when the trigger variable FF_X becomes 1 are the same as those in the first embodiment.
The diagnostic index presenting unit 10a presents to the operator the values of the diagnostic indexes Kx2H and TfH estimated by the impulse-based correction unit 8 (step S129a in FIG. 14). As in the above, the diagnostic index presenting unit 10a displays the diagnostic indexes Kx2H and TfH in a time-series graph.

The index ratio calculation unit 14 further calculates, as a diagnostic index, the ratio RX between the reactive amount FF_N calculated by the reactive amount calculation unit 7 and the total amount Kx2 of the feedforward amount MV_X2 calculated by the feedforward calculation unit 2 until the actual operating amount MV_F' is settled (step S131 in FIG. 14).
RX=FF_N×dt/Kx2 (19)

As described above, in the calculation of equation (19), the parameter Kx2 set in the feedforward calculation unit 2 is set as the total amount of the feedforward amount MV_X2.
Although there is no problem with the ratio RH shown in the first embodiment, since the ratio RH is a value for correcting the parameters of the feedforward control, it is preferable to employ the ratio RX, which is easy to intuitively understand as the degree to which the feedforward amount MV_X2 becomes invalid.

The diagnostic index presenting unit 10a presents to the operator the value of the diagnostic index RX calculated by the index ratio calculating unit 14 (step S132 in FIG. 14). As in the above, the diagnostic index presenting unit 10a displays the diagnostic index RX in a time-series graph.
The processes of steps S118, S119, S120a, S122 to S128, S129a, S131, and S132 need to be performed once when the actual manipulated variable MV_F' has stabilized.

In this embodiment, the configuration described in the first embodiment does not include the adaptive correction unit 11, but the adaptive correction unit 11 may be added to this embodiment. If the adaptive correction unit 11 is added to this embodiment, in principle, proper feedforward control will be maintained even if the amount of disturbance applied increases or decreases. Even if the adaptive correction unit 11 is added, the calculated values for the time-dependent changes in each diagnostic index are approximately the same as when the adaptive correction unit 11 is not present. Therefore, the presence or absence of the adaptive correction unit 11 does not affect the function of monitoring changes in the amount of disturbance applied and changes in the nature of the disturbance.

When formula (19) is used to calculate the ratio RX, it becomes an index ranging from a minimum value RX = 0.0 to a maximum value RX = 1.0, and the smaller the value, the more ideal the change pattern of the feedforward is applied. When the feedforward amount is affected by output saturation, the ratio RX changes not only due to changes in the disturbance itself as in Figures 11 and 12, but also due to changes in the actual operating amount MV_F' (equilibrium point) at the time of settling before the disturbance is applied. For example, in the case of a heating device as shown in Figure 17, the degree of warmth of the entire heating device can be a factor in changes in the ratio RX in the form of heat dissipation characteristics.

As described above, in applications where the cause of the change in diagnostic index over time is thought to be some kind of malfunction, the management range of each diagnostic index may be set in advance, and an alarm output unit that issues an alarm when the index falls outside the management range may be added to the first and second embodiments. If the adaptive correction unit 11 is added, in principle, proper feedforward control will be maintained, but if the adaptive correction unit 11 is not added, there is a high possibility that adverse effects will appear on the control performance regardless of the presence or absence of a malfunction, so it is preferable to always install an alarm output unit.

Figure 15 is a diagram showing an example of the presentation of the ratio RX. In the example of Figure 15, the ratio RX is displayed as a graph on the screen 150. The horizontal axis of the graph represents the number of disturbance recovery controls counted from when the trigger variable FF_X becomes 1 until it becomes 0. A graph display such as that in this embodiment can be particularly effectively used in applications in which disturbance recovery control is performed repeatedly.

In the first and second embodiments, an example of a disturbance in which the controlled variable PV decreases relative to the set value SP is described, but the present invention can also handle a disturbance in which the controlled variable PV increases relative to the set value SP. When a disturbance occurs in which the controlled variable PV increases, the actual controlled variable difference ΔMV_stp, the total amount of change ΔMV_all of the actual controlled variables MV_F', the total amount MV_X1_all of the feedforward amount MV_X1, the parameters Kx1, Kx2, the feedforward amounts MV_X1, MV_X2, and the reactive amount FF_N become negative values.

The control device described in the first and second embodiments 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. 16.

The computer includes a CPU 300, a storage device 301, and an interface device (I/F) 302. A temperature sensor or a power regulator, for example, is connected to the I/F 302. In such a computer, a program for implementing the control methods of the first and second embodiments is stored in the storage device 301. The CPU 300 executes the processing described in the first and second embodiments in accordance with the program stored in the storage device 301.

The present invention can be applied to control devices.

1...operational quantity calculation section, 2...feedforward calculation section, 3...feedforward execution section, 4...step response estimation section, 5...total quantity calculation section, 6...impulse response estimation section, 7...reactive quantity calculation section, 8...impulse response correction section, 9...estimated result output section, 10, 10a...diagnostic index presentation section, 11...adaptive correction section, 12...limit processing section, 13...operational quantity output section, 14...index ratio calculation section.

Claims (16)

a manipulation amount calculation unit configured to calculate a first manipulation amount for each control period using a set value and a control amount as input;
a feedforward calculation unit configured to calculate, for each control period, a sum of a first feedforward amount necessary to suppress a step disturbance and a second feedforward amount necessary to suppress an impulse disturbance, in response to an input of a trigger variable that is a significant value before application of the disturbance and a non-significant value after application of the disturbance;
a feedforward execution unit configured to add the third feedforward amount to the first manipulated variable calculated by the manipulated variable calculation unit for each control period;
a manipulated variable output unit configured to output a second manipulated variable obtained by adding the third feedforward variable to the first manipulated variable to a control target;
a first estimation unit configured to estimate a difference between the second manipulated variable at a time of settling before a disturbance recovery response when the trigger variable becomes a significant value and the second manipulated variable after settling of the disturbance recovery as a first parameter for calculating the first feedforward amount, and to use the estimated first parameter as a first diagnostic index;
a total amount calculation unit configured to calculate a total amount which is an integrated value of the first feedforward amount for each control period until the second manipulated variable is settled, on the assumption that the first parameter equal to the value estimated by the first estimation unit has already been set in the feedforward calculation unit and the first feedforward amount has been output based on the already set first parameter when the trigger variable becomes a significant value;
a second estimation unit configured to subtract a total amount of the first feedforward amount from a total amount that is an integrated value of an amount of change of the second manipulated variable in each control cycle until the second manipulated variable is settled during a period in which the trigger variable becomes a significant value, estimate a value obtained by multiplying the control cycle by a result of the subtraction as a second parameter for calculating the second feedforward amount, and use the estimated second parameter as a second diagnostic index;
an invalid amount calculation unit configured to calculate an invalid amount which is an integrated value of the second feedforward amount calculated by the feedforward calculation unit for each control cycle until the second manipulated variable is settling during a period in which the trigger variable becomes a significant value, the invalid amount being an integrated value of the amount invalidated due to either output saturation in which the second manipulated variable exceeds an upper limit value of a manipulated variable or output saturation in which the second manipulated variable falls below a lower limit value of a manipulated variable;
a correction unit configured to calculate, based on the invalid amount, a ratio between a total amount that is an integrated value of each control period of the second feedforward amount calculated by the feedforward calculation unit until the second manipulated variable is settling during a period in which the trigger variable becomes a significant value, and a total amount that is an integrated value of each control period of the second feedforward amount that is not invalidated due to the output saturation, estimate a correction value obtained by multiplying the second diagnostic index by the ratio so that a corresponding portion of the invalid amount is allocated within a range of the second manipulated variable that is not invalidated due to the output saturation, as a value for correcting the second feedforward amount, and set the estimated value as the corrected second diagnostic index;
a diagnostic index presenting unit configured to present the first diagnostic index and the corrected second diagnostic index. 2. The control device according to claim 1,
a correction unit configured to correct the first parameter set in the feedforward calculation unit to a value of the first diagnostic index, to correct the second parameter set in the feedforward calculation unit to a value of the corrected second diagnostic index, and to correct a time constant set in the feedforward calculation unit, the time constant defining a time for gradually converging the second feedforward amount, to a correction value of the time constant ;
The control device , wherein the correction unit calculates the second diagnostic index after the correction and calculates a value obtained by multiplying the time constant by the ratio as a correction value of the time constant . 3. The control device according to claim 1,
The second feedforward amount is calculated by [Kx2s/{(1+ATfs)(1+(2.0-A)Tfs)}]FF_X, where Kx2 is the second parameter, Tf is a time constant that specifies the time for gradually converging the second feedforward amount, A is a coefficient that adjusts the time constant, FF_X is the trigger variable, and s is a Laplace operator. 4. The control device according to claim 3,
the correction unit calculates the ratio RH by Kx2/(Kx2-FF_N×dt), where FF_N is the reactive amount, dt is the control period which is a calculation period of the first manipulated variable and the first, second and third feedforward amounts, and RH is the ratio, calculates a correction value of the second parameter Kx2 by Kx2×RH as a second diagnostic index after the correction , and calculates a value Tf×RH obtained by multiplying the time constant Tf by the ratio RH as the correction value of the time constant Tf . The control device according to any one of claims 1 to 4,
The control device is characterized in that the first feedforward amount is calculated by [Kx1/{(1+ATfs)(1+(2.0-A)Tfs)}]FF_X, where Kx1 is the first parameter, Tf is a time constant that specifies a time for gradually converging the first feedforward amount, A is a coefficient that adjusts the time constant, FF_X is the trigger variable, and s is a Laplace operator. The control device according to any one of claims 1 to 5,
an index ratio calculation unit configured to calculate, as a third diagnostic index, a ratio between the invalid amount and a total amount that is an integrated value of the second feedforward amount for each control period calculated by the feedforward calculation unit until the second manipulated variable is settled during a period in which the trigger variable becomes a significant value,
The control device, wherein the diagnostic index presenting unit presents the third diagnostic index in addition to the first diagnostic index and the corrected second diagnostic index. The control device according to any one of claims 1 to 5,
a limit processing unit that performs limit processing to limit the second manipulated variable calculated by the feedforward execution unit to a value that is equal to or greater than the manipulated variable lower limit value and equal to or less than the manipulated variable upper limit value,
the operation amount output unit outputs the second operation amount subjected to the limit processing to a control target;
the first estimator, the total amount calculator, and the second estimator perform processing using the second manipulated variable subjected to the limit process as an input;
the invalid amount calculation unit calculates the invalid amount as an integrated value of the second feedforward amount calculated by the feedforward calculation unit for each control cycle until the second manipulated variable subjected to the limit processing is settling during a period in which the trigger variable becomes a significant value, the invalid amount being an integrated value of the amount invalidated due to either output saturation in which the second manipulated variable before the limit processing exceeds the manipulated variable upper limit value or output saturation in which the second manipulated variable before the limit processing falls below the manipulated variable lower limit value;
The control device is characterized in that the correction unit calculates a ratio between a total amount that is an integrated value of each control cycle of the second feedforward amount calculated by the feedforward calculation unit until the settling of the second operation amount that has been limited during a period in which the trigger variable becomes a significant value, and a total amount that is an integrated value of each control cycle of the second feedforward amount that has not been invalidated by the output saturation, based on the invalid amount, estimates the correction value obtained by multiplying the second diagnostic index by the ratio so that a corresponding portion of the invalid amount is distributed within a range of the second operation amount before the limit processing that is not invalidated by the output saturation, and sets the estimated value as the second diagnostic index after correction. 7. The control device according to claim 6,
a limit processing unit that performs limit processing to limit the second manipulated variable calculated by the feedforward execution unit to a value that is equal to or greater than the manipulated variable lower limit value and equal to or less than the manipulated variable upper limit value,
the operation amount output unit outputs the second operation amount subjected to the limit processing to a control target;
the first estimator, the total amount calculator, the second estimator, and the index ratio calculator perform processing using the second manipulated variable subjected to the limit process as an input;
the invalid amount calculation unit calculates the invalid amount as an integrated value of the second feedforward amount calculated by the feedforward calculation unit for each control cycle until the second manipulated variable subjected to the limit processing is settling during a period in which the trigger variable becomes a significant value, the invalid amount being an integrated value of the amount invalidated due to either output saturation in which the second manipulated variable before the limit processing exceeds the manipulated variable upper limit value or output saturation in which the second manipulated variable before the limit processing falls below the manipulated variable lower limit value;
The control device is characterized in that the correction unit calculates a ratio between a total amount that is an integrated value of each control cycle of the second feedforward amount calculated by the feedforward calculation unit until the settling of the second operation amount that has been limited during a period in which the trigger variable becomes a significant value, and a total amount that is an integrated value of each control cycle of the second feedforward amount that has not been invalidated by the output saturation, based on the invalid amount, estimates the correction value obtained by multiplying the second diagnostic index by the ratio so that a corresponding portion of the invalid amount is distributed within a range of the second operation amount before the limit processing that is not invalidated by the output saturation, and sets the estimated value as the second diagnostic index after correction. A first step of calculating a first manipulated variable for each control cycle using a set value and a controlled variable as input;
a second step of calculating, for each control period, a sum of a first feedforward amount necessary to suppress a step disturbance and a second feedforward amount necessary to suppress an impulse disturbance in response to an input of a trigger variable that is a significant value before the application of the disturbance and is a non-significant value after the application of the disturbance;
a third step of adding the third feedforward amount to the first manipulated variable for each control period;
a fourth step of outputting a second manipulated variable obtained by adding the third feedforward variable to the first manipulated variable to a control target;
a fifth step of estimating a difference between the second manipulated variable at the time of settling before a disturbance recovery response when the trigger variable becomes a significant value and the second manipulated variable after settling of the disturbance recovery as a first parameter for calculating the first feedforward amount, and setting the estimated first parameter as a first diagnostic index;
a sixth step of calculating a total amount which is an integrated value of the first feedforward amount for each control period until the second manipulated variable is settled, on the assumption that the first parameter equal to the value estimated in the fifth step has already been set and the first feedforward amount has been output based on the already set first parameter when the trigger variable becomes a significant value;
a seventh step of subtracting a total amount of the first feedforward amount from a total amount that is an integrated value of an amount of change of the second manipulated variable in each control cycle until the second manipulated variable is settled during a period in which the trigger variable becomes a significant value, estimating a value obtained by multiplying the control cycle by a result of the subtraction as a second parameter for calculating the second feedforward amount, and setting the estimated second parameter as a second diagnostic index;
an eighth step of calculating an invalid amount, which is an integrated value of the second feedforward amount calculated for each control cycle by the second step until the second manipulated variable is settling during a period in which the trigger variable becomes significant, which is invalidated due to either output saturation in which the second manipulated variable exceeds a manipulated variable upper limit value or output saturation in which the second manipulated variable falls below a manipulated variable lower limit value;
a ninth step of calculating, based on the invalid amount, a ratio between a total amount that is an integrated value of each control period of the second feedforward amount calculated in the second step until the second manipulated variable is settled during a period in which the trigger variable becomes a significant value and a total amount that is an integrated value of each control period of the second feedforward amount that is not invalidated due to the output saturation, estimating a correction value obtained by multiplying the second diagnostic index by the ratio so that a corresponding portion of the invalid amount is distributed within a range of the second manipulated variable that is not invalidated due to the output saturation, as a value for correcting the second feedforward amount, and setting the estimated value as the corrected second diagnostic index;
and a tenth step of presenting the first diagnostic index and the corrected second diagnostic index. 10. The control method according to claim 9,
an eleventh step of correcting the first parameter set for calculating the first feedforward amount in the second step to a value of the first diagnostic index, correcting the second parameter set for calculating the second feedforward amount in the second step to a value of the corrected second diagnostic index, and correcting a time constant set for calculating the second feedforward amount in the second step, the time constant defining a time for gradually converging the second feedforward amount, to a correction value of the time constant ;
The ninth step of the present invention is a control method characterized in that it includes a step of calculating the corrected second diagnostic index and calculating a value obtained by multiplying the time constant by the ratio as a correction value of the time constant . 11. The control method according to claim 9 or 10,
The second feedforward amount is calculated by [Kx2s/{(1+ATfs)(1+(2.0-A)Tfs)}]FF_X, where Kx2 is the second parameter, Tf is a time constant that specifies the time for gradually converging the second feedforward amount, A is a coefficient that adjusts the time constant, FF_X is the trigger variable, and s is a Laplace operator. 12. The control method according to claim 11,
the ninth step includes the steps of: calculating the ratio RH by Kx2/(Kx2-FF_N×dt), where FF_N is the reactive amount, dt is the control period which is a calculation period of the first manipulated variable and the first, second and third feedforward amounts, and RH is the ratio; calculating a correction value of the second parameter Kx2 by Kx2×RH as the second diagnostic index after the correction ; and calculating a value Tf×RH obtained by multiplying the time constant Tf by the ratio RH as the correction value of the time constant Tf . 13. The control method according to claim 9, further comprising:
the first feedforward amount is calculated by [Kx1/{(1+ATfs)(1+(2.0-A)Tfs)}]FF_X, where Kx1 is the first parameter, Tf is a time constant that specifies a time for gradually converging the first feedforward amount, A is a coefficient that adjusts the time constant, FF_X is the trigger variable, and s is a Laplace operator. 14. The control method according to claim 9, further comprising:
a twelfth step of calculating, as a third diagnostic index, a ratio between the invalid amount and a total amount, which is an integrated value of the second feedforward amount calculated in the second step for each control period until the second manipulated variable is settled during a period in which the trigger variable becomes significant;
and a thirteenth step of presenting the third diagnostic index. 14. The control method according to claim 9,
a twelfth step of limiting the second manipulated variable calculated in the third step to a value equal to or greater than the manipulated variable lower limit value and equal to or less than the manipulated variable upper limit value,
the fourth step includes a step of outputting the second manipulated variable subjected to the limit process to a control target;
the fifth step, the sixth step, and the seventh step perform processing using the second manipulated variable that has been subjected to the limit process as an input;
the eighth step includes a step of calculating an invalid amount which is an integrated value of the second feedforward amount calculated for each control cycle by the second step until the second manipulated variable subjected to the limit processing is settling during a period in which the trigger variable becomes a significant value, the invalid amount being an integrated value of the amount invalidated due to either output saturation in which the second manipulated variable before the limit processing exceeds the manipulated variable upper limit value or output saturation in which the second manipulated variable before the limit processing falls below the manipulated variable lower limit value;
the ninth step includes a step of calculating, based on the invalid amount, a ratio between a total amount that is an integrated value of each control cycle of the second feedforward amount calculated by the second step until the settling of the second operation amount that has been limited during a period in which the trigger variable becomes a significant value and a total amount that is an integrated value of each control cycle of the second feedforward amount that has not been invalidated due to the output saturation, estimating the correction value obtained by multiplying the second diagnostic index by the ratio so that a corresponding portion of the invalid amount is distributed within a range of the second operation amount before the limit processing that is not invalidated due to the output saturation, as a value for correcting the second feedforward amount, and setting the estimated value as the corrected second diagnostic index. 15. The control method according to claim 14,
a fourteenth step of limiting the second manipulated variable calculated in the third step to a value equal to or greater than the manipulated variable lower limit value and equal to or less than the manipulated variable upper limit value,
the fourth step includes a step of outputting the second manipulated variable subjected to the limit process to a control target;
the fifth step, the sixth step, the seventh step, and the twelfth step perform processing using the second manipulated variable that has been subjected to the limit process as an input;
the eighth step includes a step of calculating an invalid amount which is an integrated value of the second feedforward amount calculated for each control cycle by the second step until the second manipulated variable subjected to the limit processing is settling during a period in which the trigger variable becomes a significant value, the invalid amount being an integrated value of the amount invalidated due to either output saturation in which the second manipulated variable before the limit processing exceeds the manipulated variable upper limit value or output saturation in which the second manipulated variable before the limit processing falls below the manipulated variable lower limit value;
the ninth step includes a step of calculating, based on the invalid amount, a ratio between a total amount that is an integrated value of each control cycle of the second feedforward amount calculated by the second step until the settling of the second operation amount that has been limited during a period in which the trigger variable becomes a significant value and a total amount that is an integrated value of each control cycle of the second feedforward amount that has not been invalidated due to the output saturation, estimating the correction value obtained by multiplying the second diagnostic index by the ratio so that a corresponding portion of the invalid amount is distributed within a range of the second operation amount before the limit processing that is not invalidated due to the output saturation, as a value for correcting the second feedforward amount, and setting the estimated value as the corrected second diagnostic index.

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