JP2020024491A - Control device and abnormality detection method - Google Patents

Abstract

To perform abnormality detection without error even if there is a delay in the adjustment output change at the time of output switching.SOLUTION: A determination value calculation unit 16C acquires and sequentially saves an adjustment output value Q(i) for every certain measurement period M(i), and calculates a determination value D(i) indicating the degree of attainment of the adjustment output value Q(i) with respect to the preset specified value QS based on a plurality of adjustment output values Q obtained up to the adjustment output value Q(i). A standby period detection unit 16D detects, as the standby period TW, the time from when the output of the adjustment output is switched to the time when the determination value D(i) reaches a determination threshold DS. An abnormality detection unit 16E stops the abnormality detection until the standby period TW elapses from the output switching time, and starts the abnormality detection when the standby period TW elapses.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an abnormality detection technique for detecting an abnormality of a device when controlling a process amount to a set value.

  In a control device that controls a process amount such as a temperature, a pressure, and a flow rate to a preset set value SP, a new operation amount MV is determined based on a feedback method such as a PID based on the measured values PV and SP regarding the process amount. Based on the calculated and obtained operation amount MV, the process amount is controlled by switching the output start or the output stop of the adjustment output output from the operating device to the device.

  For example, a temperature controller representing a control device performs a PID calculation based on a measured temperature PV measured as a process amount and a set temperature SP, and controls a heater based on the obtained operation amount MV. As a result, the current supplied from the operating device to the heater is on / off controlled, and the temperature is adjusted by the heater so that the measured temperature PV as the process amount becomes the set temperature SP.

  In such a control device, it is necessary to accurately detect occurrence of an abnormality in a device for adjusting a process amount. Conventionally, as an abnormality detection technology for such a temperature controller, an abnormality in the heater is detected by monitoring the current supplied from the operating device to the heater as an adjustment output, and comparing the detected current value with a reference value. (For example, see Patent Document 1).

Japanese Patent Publication No. 7-93178

However, in such a conventional technique, when detecting an abnormality of a device, the delay of the adjustment output change at the time of switching on / off control of the device, that is, at the time of output switching in which the output of the adjustment output is started or stopped is not considered. Therefore, there is a problem that an abnormality of the device is erroneously detected at the time of output switching.
In general, a device for adjusting the process amount has a certain time constant, and thus the value of the adjustment output output from the operating device tends to change with a delay. For example, the heater does not reach the rated value immediately after the current supply is started, but requires a certain amount of time to reach the rated value. Therefore, if the abnormality detection is started immediately at the time when the current supply is indicated by the operation amount MV, the current to the heater is not sufficiently flowing, and the abnormality detection is erroneously determined.

  An object of the present invention is to solve such a problem, and an object of the present invention is to provide an abnormality detection technology that can perform abnormality detection without error even when there is a delay in adjustment output change at the time of output switching. .

  In order to achieve such an object, the control device according to the present invention monitors an adjustment output output from an operating device to a device that adjusts a process amount during operation of process control, thereby controlling the abnormality of the device. An abnormality detection unit that performs detection, and acquires a new adjustment output value indicating the value of the adjustment output every fixed measurement period, sequentially stores the new adjustment output value in a storage circuit, and stores the new adjustment output stored in the storage circuit. A determination value calculation unit that calculates a determination value indicating a degree of attainment of the new adjustment output value with respect to a preset specified value, based on the plurality of adjustment output values obtained up to the value, and an output of the adjustment output A standby period detection unit that detects, as a standby period, a period from the time of output switching at which start or output stop is performed to the time when the determination value reaches a predetermined determination threshold value, and the abnormality detection unit includes: The abnormality detection is stopped during a period from the force switching time until the waiting period has elapsed, in which so as to start the abnormality detection when the waiting period has elapsed.

  Further, in the configuration example of the control device according to the present embodiment, when the determination value calculation unit calculates the determination value, a predetermined determination time length from the time when the new adjustment output value is acquired. The determination value is calculated based on the plurality of adjustment output values obtained during a retrospective determination period.

  Further, one configuration example of the above-described control device according to the present embodiment is such that the determination value calculation unit obtains the output after the output switching time at which the output of the adjustment output is started or stopped during the operation of the process control. The determination value is calculated for each of the obtained new adjustment output values, and the standby period detecting unit detects the standby period TW based on the determination value obtained during the operation. is there.

  Further, one configuration example of the above-described control device according to the present embodiment is configured such that the determination value calculation unit performs output switching or output stop of the adjustment output on a trial basis during non-operation of the process control. The determination value is calculated for each of the new adjustment output values obtained after the time, and the standby period detection unit detects the standby period TW based on the determination value obtained during the non-operation. It is like that.

  In addition, one configuration example of the above-described control device according to the present embodiment is configured such that when the determination value calculation unit calculates the determination value, a predetermined reference determination value and the new adjustment output value are compared. The difference or the ratio is calculated as the determination value.

  Further, the abnormality detection method according to the present embodiment is a control device that detects an abnormality of a device for adjusting a process amount by monitoring an adjustment output output from an operation device for the device for adjusting a process amount during operation of process control. Wherein the determination value calculation unit acquires a new adjustment output value indicating the value of the adjustment output for each predetermined measurement period, sequentially stores the new adjustment output value in the storage circuit, and stores the new adjustment output value in the storage circuit. Determination value calculation for calculating a determination value indicating the degree of attainment of the new adjustment output value with respect to a preset specified value based on a plurality of adjustment output values obtained up to the new adjustment output value The step and the standby period detecting unit detect a standby period from a time point at which the output of the adjusted output is started or stopped to a time point at which the determination value reaches a predetermined determination threshold value. A standby period detecting step for performing the abnormality detection, wherein the abnormality detection unit stops the abnormality detection during a period from the output switching time to the end of the standby period, and starts the abnormality detection at the end of the standby period. And steps.

  According to the present invention, the abnormality detection by the abnormality detection unit is stopped only during the standby period from the time of output switching to the time when the adjusted output value shows a certain degree of reaching the specified value. Therefore, even if there is a delay in the adjustment output change at the time of output switching, the abnormality detection is started after the delay is eliminated, so that abnormality detection can be performed without error.

FIG. 2 is a block diagram illustrating a configuration of a control device. 5 is a flowchart illustrating a determination value calculation process according to the first embodiment. FIG. 9 is an explanatory diagram illustrating a determination value calculation process according to the first embodiment. 5 is a timing chart showing an abnormality detection operation (from OFF to ON). 5 is a timing chart showing an abnormality detection operation (from ON to OFF). 9 is a flowchart illustrating a determination value calculation process according to a second embodiment. FIG. 14 is an explanatory diagram illustrating a determination value calculation process according to the second embodiment.

Next, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
First, a control device 10 according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram illustrating a configuration of the control device.

  The control device 10 is composed of an arithmetic processing device as a whole. In a control device that controls a process amount such as a temperature, a pressure and a flow rate to a preset set value SP, a measured value PV and a set value SP related to the process amount are set. , And a PID calculation based on the manipulated variable MV, and based on the obtained manipulated variable MV, controls the start or stop of the output of the adjustment output output from the operating device to the device, thereby controlling the process amount. It has a control function.

  As a specific example of the control device 10, there is a digital indicating controller used as a temperature controller or the like. Hereinafter, a case where the control device 10 operates as a temperature controller will be described as an example. That is, as shown in FIG. 1, the control device 10 performs a PID calculation based on the measured temperature PV measured by the temperature sensor 3 and the set temperature SP as the process amount, and controls the operating device 1 based on the obtained operation amount MV. Control. As a result, the current I supplied from the operating device 1 to the heater 2 is turned on and off, and the temperature is adjusted by the heater 2 so that the measured temperature PV, which is the process amount, becomes the set temperature SP. It is assumed that the configuration example of the control device 10 includes a device having only an abnormality detection function described later without including a process amount control function.

  According to the present invention, when the controller 10 detects an abnormality of the heater 2 based on the current I detected by the current detector 4, the current I acquired for each predetermined measurement period is defined from the time when the output of the current I is switched. The time until the value is reached is detected as a standby period, abnormality detection is stopped during the period from the output switching time until the standby period elapses, and abnormality detection is started when the standby period elapses. is there.

[Control device]
Next, the configuration of the control device 10 according to the present embodiment will be described in detail with reference to FIG. As shown in FIG. 1, the control device 10 includes, as main components, a device I / F circuit 11, a communication I / F circuit 12, an operation input circuit 13, a display circuit 14, a storage circuit 15, and an arithmetic processing circuit 16. Have.

  The device I / F circuit 11 has a function of performing data communication with the operating device 1, the temperature sensor 3, and the current detector 4. Specifically, the device I / F circuit 11 has a function of transmitting the operation amount MV to the operation device 1, a function of acquiring the measured temperature PV of the heater 2 detected by the temperature sensor 3, and a function of the current detector 4. It has a function of acquiring the detected current I from the operating device 1 to the heater 2 as an adjustment output value Q.

  The communication I / F circuit 12 has a function of performing data communication with a higher-level device (not shown) via the communication line L. Specifically, the communication I / F circuit 12 has a function of acquiring various control parameters instructed from the higher-level device, a function of notifying the higher-level device of a result of abnormality detection, and the like.

The operation input circuit 13 has operation input devices such as operation keys, operation switches, and a touch panel, and has a function of detecting an operation of an operator and outputting the operation to the arithmetic processing circuit 16.
The display circuit 14 has a display device such as an LED or an LCD, and has a function of displaying various data, such as an operation state, a control status, and an abnormality detection result, instructed by the arithmetic processing circuit 16.

  The storage circuit 15 is composed of a semiconductor memory, and has a function of storing various processing data and programs used for process control and abnormality detection in the arithmetic processing circuit 16. Main processing data stored in the storage circuit 15 includes control data such as a set temperature (set value) SP, a measured temperature (measured value) PV, an operation amount MV, and an adjustment output value (detected current) Q used for PID control. is there. The program stored in the storage circuit 15 is stored in the storage circuit 15 in advance from an external device connected to the control device 10 or a recording medium (both not shown).

  The arithmetic processing circuit 16 includes a CPU and peripheral circuits, and has a function of implementing various processing units by reading and executing a program in the storage circuit 15. The main processing units realized by the arithmetic processing circuit 16 include a set value acquisition unit 16A, a device control unit 16B, a determination value calculation unit 16C, a standby period detection unit 16D, and an abnormality detection unit 16E.

  The set value acquisition unit 16A acquires a set temperature SP that is a target of the process value based on the operator operation detected by the operation input circuit 13 or the control parameter received by the communication I / F circuit 12. It has a function of storing in the storage circuit 15.

  The device control unit 16B has a function of performing feedback calculation such as PID based on the measured temperature PV, the set temperature SP, and the operation amount MV acquired from the temperature sensor 3 via the device I / F circuit 11. It has a function of outputting a new operation amount MV from the device I / F circuit 11 to the operation device 1.

  The determination value calculation unit 16C receives a signal from the current detector 4 via the device I / F circuit 11 every fixed measurement period M (i) (i = 1, 2,..., N; n is an integer of 2 or more). A function of acquiring a new adjustment output value Q (i) indicating the value of the current (adjustment output) I and sequentially storing it in the storage circuit 15, and a function of acquiring a new adjustment output value Q (i) stored in the storage circuit 15 ), The determination value D (i) indicating the degree of attainment of the new adjustment output value Q (i) with respect to the preset specified value QS, based on the determination target Q ′ including the plurality of adjustment output values Q. ) Is calculated.

  The standby period detection unit 16D causes the determination value D (i) to reach a predetermined determination threshold DS from the time of output switching at which the output of the current I to the operating device 1 is started or stopped by the device control unit 16B. It has a function of detecting up to the time point as the waiting period TW.

  The abnormality detection unit 16E detects the abnormality of the heater 2 by monitoring the current (adjustment output) I output from the operating device 1 to the heater (equipment) 2 for adjusting the process amount during the operation of the process control. It has a function to perform the abnormality detection and a function to stop the abnormality detection during a period from when the output is switched by the device control unit 16B until the standby period TW elapses, and to start the abnormality detection when the standby period TW elapses. .

[Operation of First Embodiment]
Next, an abnormality detection operation of the control device 10 according to the present embodiment will be described with reference to FIGS. FIG. 2 is a flowchart illustrating a determination value calculation process according to the first embodiment. FIG. 3 is an explanatory diagram illustrating a determination value calculation process according to the first embodiment. FIG. 4 is a timing chart showing the abnormality detection operation (from OFF to ON). FIG. 5 is a timing chart showing the abnormality detection operation (from ON to OFF).

  Here, it is assumed that the determination value calculation unit 16C calculates the determination value D (i) for each determination period N (i) having a fixed determination time length TN, and the determination period N (i) includes a fixed measurement time period. It is assumed that m (m is an integer of 2 or more) adjustment output values Q (i) acquired for each measurement period M (i) having the length TM. Further, it is assumed that the determination threshold value DS is 100%. Note that the number of measurement periods M (i) included in the ON period in which the operation amount MV indicates the current output or the OFF period in which the operation amount MV indicates the current stop is n (n is an integer of 2 or more), and m Is an integer equal to or less than n.

The determination value calculation unit 16C executes the determination value calculation processing of FIG. 2 for each measurement period M (i).
First, the determination value calculation unit 16C waits until the acquisition timing in the measurement period M (i) arrives (step S100), and performs new adjustment from the current detector 4 via the device I / F circuit 11 according to the arrival of the acquisition timing. The output value Q (i) is obtained and stored in the storage circuit 15 (step S101).
Next, the determination value calculation unit 16C determines the m pieces of adjustment output values Q (i−m + 1) obtained during the determination period N (i) which is traced back by a certain determination time length TN from the time when Q (i) was obtained. ) To Q (i) are selected from the storage circuit 15 as the determination target Q ′ (step S102).

Subsequently, the determination value calculation unit 16C compares each of the adjustment output values Q (i−m + 1) to Q (i) belonging to Q ′ with a preset specified value QS1 (Step S103). Is calculated as the determination value D (i) and stored in the storage circuit 15 (step S104), and the series of determination value calculation processing ends.
When the m adjustment output values Q (i−m + 1) to Q (i) cannot be selected from the storage circuit 15, the determination value D (i) is calculated assuming that the insufficient Q has not reached QS1. do it.

Thereby, as shown in FIG. 3, when Q (m) is acquired in the measurement period M (m), m Q (1) to Q (m) belonging to the corresponding determination period N (m) are Q (Q), and the rate at which they reach QS1 is calculated as D (m).
When Q (m + 1) is obtained in the subsequent measurement period M (m + 1), m Q (2) to Q (m + 1) belonging to the corresponding determination period N (m + 1) are selected as Q ′, Is calculated as D (m + 1).

As shown in FIG. 4, in the actual process control, when the output of the current is instructed by the manipulated variable MV at the time of the output switching at the time TC1, the current I gradually increases from the time TC1, and thereafter the time TQ1 Then, it is assumed that the ON period specified value QS1 (maximum rated current value) indicating the current output has been reached.
Therefore, Q (i) gradually increases from TC1, and D (i) starts increasing from TC1. At this time, since DS1 = 100%, D (i) is determined when all m Qs included in the determination period Ni have reached QS1 at time TD1 which is delayed from TQ1 by the determination time length TN. The threshold value DS1 will be reached.

As a result, the standby period detection unit 16D detects the output period from TC1 to TD1 as the standby period TW1.
Therefore, for TW1 from the time of output switching at time TC1 to TD1, the abnormality detection unit 16E stops abnormality detection based on Q (i). Thereafter, the standby period TW1 elapses at the time TD1, so that the abnormality detection unit 16E starts abnormality detection based on Q (i).

Further, as shown in FIG. 5, in the actual process control, when the current output is instructed by the manipulated variable MV at the time of the output switching at the time TC2, the current I gradually decreases from the time TC2, and thereafter, At time TQ2, it is assumed that a specified value QS2 (zero) of the OFF period indicating current stop has been reached.
Therefore, Q (i) gradually decreases from TC2, and D (i) starts decreasing from TC2. At this time, since DS2 = 100%, D (i) is determined when all m Qs included in the determination period Ni have reached QS2 at time TD2 which is delayed from TQ2 by the determination time length TN. The threshold value DS2 will be reached.

Thereby, the standby period detection unit 16D detects TC2, which is the output switching point, as the start point of the standby period TW2, and detects TD2 as the end point of the standby period TW2.
Therefore, the standby period TW2 is started at the time of the output switching at the time TC2, so that the abnormality detection unit 16E stops the abnormality detection based on Q (i). Thereafter, since the waiting period TW2 is completed at the time TD2, the abnormality detection unit 16E starts abnormality detection based on Q (i).

[Effect of First Embodiment]
As described above, in the present embodiment, the determination value calculation unit 16C acquires a new adjustment output value Q (i) for each predetermined measurement period M (i), sequentially saves the new adjustment output value Q (i), Based on the plurality of adjustment output values Q obtained up to (i), a determination value D (i) indicating the degree of attainment of a new adjustment output value Q (i) with respect to a preset specified value QS is calculated. The standby period detecting unit 16D detects the standby period TW from the point at which the output of the adjustment output is switched to the point at which the determination value D (i) reaches the determination threshold DS. The abnormality detection is stopped until the period TW elapses, and the abnormality detection is started when the standby period TW elapses.

  As a result, the abnormality detection by the abnormality detection unit 16E is stopped for the waiting period TW from the time of output switching until the new adjusted output value Q (i) shows a certain degree of reaching the specified value QS. Become. Therefore, even if there is a delay in the adjustment output change at the time of output switching, the abnormality detection is started after the delay is eliminated, so that abnormality detection can be performed without error.

  Further, in the present embodiment, when the determination value calculation unit 16C calculates the determination value D (i), the determination is performed by a predetermined determination time length TN from the time when the new adjustment output value Q (i) is obtained. The determination value D (i) may be calculated based on the plurality of adjustment output values Q acquired during the period N (i). Accordingly, the latest Q of Q (i) is used for calculating Q (i), so that determination value D (i) can be determined with high accuracy.

Further, in the present embodiment, the determination value calculation unit 16C uses the new adjustment output value Q (i) obtained after the output switching time point when the output of the adjustment output is started or stopped during the operation of the process control. Alternatively, the determination value D (i) may be calculated, and the standby period detection unit 16D may detect the standby period TW based on the determination value D (i) obtained during operation.
This makes it possible to more accurately stop and start abnormality detection based on the new standby period TW detected at each output switching time.

Further, in the present embodiment, when the process control is not performed, the determination value calculation unit 16C outputs a new adjustment output value Q obtained after the output switching time at which the output of the adjustment output is experimentally started or stopped. The determination value D (i) may be calculated for each (i), and the standby period detection unit 16D may detect the standby period TW based on the determination value D (i) obtained during non-operation. .
Accordingly, the abnormality detection is stopped and started based on the new standby period TW detected in advance, so that the processing load required for calculating the standby period TW can be reduced.

[Second embodiment]
Next, a control device 10 according to a second embodiment of the present invention will be described.
In the first embodiment, when calculating the determination value D (i), the rate at which m Q (i) included in the determination period N (i) has reached the specified value QS is determined by the determination value D ( The case of calculating as i) has been described as an example, but the method of calculating D (i) is not limited to this.
In the present embodiment, a case will be described in which a difference or a ratio between a preset reference determination value Q (ref) and Q (i) is calculated as a determination value D (i).

That is, in the present embodiment, when calculating the determination value D (i), the determination value calculation unit 16C calculates the difference between the preset reference determination value Q (ref) and the adjustment output value Q (i) or It has a function of calculating the ratio as the determination value D (i).
Other configurations of the control device 10 according to the present embodiment are the same as those of the first embodiment, and a detailed description thereof will be omitted.

[Operation of Second Embodiment]
Next, an abnormality detection operation of the control device 10 according to the present embodiment will be described with reference to FIGS. FIG. 6 is a flowchart illustrating a determination value calculation process according to the second embodiment. FIG. 7 is an explanatory diagram illustrating a determination value calculation process according to the second embodiment.

  Here, it is assumed that the determination value calculation unit 16C acquires the adjustment output value Q obtained during the preset reference period M (ref) from the storage circuit 15 and uses the adjusted output value Q as the reference determination value Q (ref). I do. Further, as shown in FIG. 7, M (ref) is a measurement period immediately before the output switching time point TC0 immediately before the output switching time point TC1 at which the calculation of the standby period TW is started.

  Thereby, as shown in FIG. 4, when the calculation of the TW is performed during the ON period, Q acquired during (the last of) the immediately preceding ON period is used as Q (ref). Further, as shown in FIG. 5, when the calculation of the TW is performed during the OFF period, Q obtained during (the last of) the immediately preceding OFF period is used as Q (ref).

The determination value calculation unit 16C executes the determination value calculation processing of FIG. 6 for each measurement period M (i).
First, the determination value calculation unit 16C waits until the acquisition timing in the measurement period M (i) arrives (step S200), and adjusts the adjustment output value from the current detector 4 via the device I / F circuit 11 according to the acquisition timing. Q (i) is obtained and stored in the storage circuit 15 (step S201).
Next, the determination value calculation unit 16C uses the difference Q (i) -Q (ref) between Q (i) and Q (ref) or the ratio Q (i) / Q (ref) as the determination value D (i). The calculated value is stored in the storage circuit 15 (step S202), and the series of determination value calculation processing ends.

[Effect of Second Embodiment]
As described above, in the present embodiment, when the determination value calculating unit 16C calculates the determination value D (i), the reference value Q (ref) and the adjustment output value Q (i) are set in advance. The difference or the ratio is calculated as a determination value D (i).
As a result, the processing load required to calculate D (i) can be significantly reduced as compared with the first embodiment.

[Expansion of Embodiment]
As described above, the present invention has been described with reference to the exemplary embodiments. However, the present invention is not limited to the exemplary embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention. In addition, the respective embodiments can be arbitrarily combined and implemented without contradicting each other.

  DESCRIPTION OF SYMBOLS 10 ... Control device, 11 ... Equipment I / F circuit, 12 ... Communication I / F circuit, 13 ... Operation input circuit, 14 ... Display circuit, 15 ... Storage circuit, 16 ... Operation processing circuit, 16A ... Setting value acquisition part, 16B: equipment control section, 16C: determination value calculation section, 16D: standby period detection section, 16E: abnormality detection section, 1 ... operating device, 2 ... heater, 3 ... temperature sensor, 4 ... current detector.

Claims (6)

During operation of the process control, an abnormality detection unit that detects an abnormality of the device by monitoring an adjustment output output from the operation device for the device that adjusts the process amount,
A new adjustment output value indicating the value of the adjustment output is obtained for each fixed measurement period and sequentially stored in the storage circuit, and a plurality of adjustment output values obtained up to the new adjustment output value stored in the storage circuit are obtained. Based on the adjustment output value, a determination value calculation unit that calculates a determination value indicating the degree of attainment of the new adjustment output value with respect to a preset specified value,
A standby period detection unit that detects, as a standby period, a period from the output switching time at which the output of the adjustment output is performed or the output is stopped, to a time at which the determination value reaches a predetermined determination threshold,
The control device, wherein the abnormality detection unit stops the abnormality detection during a period from the output switching time to when the standby period elapses, and starts the abnormality detection when the standby period elapses. The control device according to claim 1,
The determination value calculation unit, when calculating the determination value, based on the plurality of adjustment output values obtained during a determination period that is retroactive by a certain determination time length from the time when the new adjustment output value is obtained And a controller for calculating the determination value. In the control device according to claim 1 or 2,
The determination value calculation unit calculates the determination value for each of the new adjustment output values obtained after the output switching time point at which the output of the adjustment output is started or stopped during the operation of the process control. ,
The control device, wherein the standby period detection unit detects the standby period TW based on the determination value obtained during the operation. In the control device according to claim 1 or 2,
The determination value calculation unit, when the process control is not in operation, for each of the new adjustment output values obtained after the output switching time when the output of the adjustment output was started or stopped experimentally, the determination value Is calculated respectively,
The control device, wherein the standby period detection unit detects the standby period TW based on the determination value obtained during the non-operation. The control device according to claim 1,
A control unit configured to calculate, as the determination value, a difference or ratio between a preset reference determination value and the new adjustment output value when calculating the determination value. . During operation of the process control, an abnormality detection method used in a control device that performs abnormality detection of the device by monitoring an adjustment output output from an operation device for the device that adjusts a process amount,
The determination value calculation unit obtains a new adjustment output value indicating the value of the adjustment output for each fixed measurement period, sequentially stores the new adjustment output value in the storage circuit, and up to the new adjustment output value stored in the storage circuit. A determination value calculating step of calculating a determination value indicating a degree of attainment of the new adjustment output value with respect to a predetermined specified value, based on the plurality of adjustment output values obtained in
A standby period detecting step in which a standby period detecting unit detects, as a standby period, a period from an output switching time point at which the output of the adjustment output is started or output is stopped to a time point at which the determination value reaches a predetermined determination threshold. ,
An abnormality detection step of stopping the abnormality detection during a period from the output switching time to the elapse of the standby period, and starting the abnormality detection at the elapse of the standby period. Abnormality detection method.

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