JP3070814B2 - Multiplexing control device and control output determination method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multiplex control device,
In particular, the present invention relates to a method and an apparatus for determining a control command with high reliability.

[0002]

2. Description of the Related Art A control device applied to a control system requiring high reliability has two steps from a process measurement to a control device.
A multiplexing configuration such as multiplexing or triplexing is used, and based on a plurality of control signals output from each control device, an output signal to a control target is determined by majority logic, intermediate value selection logic, or the like. As such an example, Japanese Patent Application Laid-Open No. 62-540
No. 2 is known.

In determining a control signal to be output to a control target, a self-diagnosis is performed only by each control device, and a control signal is exchanged between multiplexed control devices to check a deviation value between each two signals. However, mutual diagnosis for eliminating abnormal control signals is performed.

Many systems in a normal multiplexing control device operate each control device asynchronously because of the simplicity of the configuration. Even if the sampling cycle (also the control cycle) is the same, the execution timing is shifted (phase difference). ). For this reason, due to a process change or an instrument drift that occurs during the deviation, the measurement value taken into the control device does not become the same value even for the same measurement target, which causes a deviation between the control signals.

Therefore, in the mutual diagnosis based on the deviation check of the control signal, an allowable range is set in advance, and the deviation value between the normal control signals is regarded as normal. This permissible range needs to be large for a controlled object or the like in which the control output changes suddenly.

[0006]

In the conventional multiplexing control apparatus, the mutual diagnosis based on the check of the deviation value makes it possible to specify an abnormal signal only when two or more sets of deviation values exceed an allowable range. . For this reason, it takes time until diagnosis, and during this time, the control target is controlled by an incorrect control output signal including an abnormal signal. In addition, when a control command is determined based on a normal control signal excluding an abnormal signal, there is a problem that the reliability and stability of control are impaired, for example, a discontinuous step change that causes disturbance occurs.

[0007] Even when the multiplexing control device is operated synchronously, the control signal continues to be constant when a failure occurs in the memory of the analog input (AI) card.
However, since self-diagnosis is difficult, it takes time to detect an abnormality based on the deviation value check. In such a case, the above problem also occurs.

An object of the present invention is to provide a method for stably and accurately determining a control command of a multiplex control device.

It is another object of the present invention to provide a low-cost asynchronous multiplexing control device having a simple system configuration with a diagnostic device for ensuring reliability and stability.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to mutually diagnose each control signal by a plurality of control devices,
In a control output determination method of a multiplexing control device for determining a control command to a control object, a change rate of each of the control signals and a change rate difference between the change rates are obtained, and the change rate difference is set to a predetermined value. This is achieved by performing a change rate diagnosis as to whether the change rate is within the allowable value, and selecting a normal control signal corresponding to the change rate difference within the allowable value to determine the control command.

[0011]

According to the present invention, the change rate difference becomes remarkable earlier in comparison with the conventional signal deviation. Therefore, when there is an abnormality in a control signal from each control device, it is possible to detect and eliminate the abnormality at an early stage, and control with a normal control signal can be continued.

As a result, it is possible to prevent the output of an inaccurate control command including an abnormal signal and the occurrence of disturbance at the time of switching, and to realize highly accurate and stable control in the multiplexing control device.

[0013]

FIG. 2 is a block diagram of a process control system to which the multiplexing control device of the present invention is applied. The multiplexing control device 2 of FIG. 1 is configured in a triple system in which the control devices 2-1, 2-2, and 2-3 are connected by a transmission line 1. The multiplexing control device 2 includes a process input / output device (PI / O) 3 (3-1 to 3).
The control command signal U is output to the process 9 while the target value from the target value setting device 7 and the actually measured value of the control target 8 by the measuring devices 9-1 to 9-3 are taken in through (-3).

The control devices 2-1, 2-2, and 2-3 have a control operation unit 4 for calculating a control output in accordance with a deviation between an actual measurement value from a corresponding measuring instrument and a target value. A transmission control unit 5 that exchanges via the transmission line 1 and a mutual diagnosis unit 6 that compares its own control output with other control outputs to perform mutual diagnosis and determine a control command signal U based on a normal control signal.
It has. Generally, a self-diagnosis function (not shown) is also provided.

FIG. 1 shows an embodiment of the present invention.
FIG. 2 is a functional block diagram illustrating details of a first example. The control devices 2-2 and 2-3 have the same configuration. In the figure, a mutual diagnosis unit 6 includes a change rate check unit 61 for performing a change rate check between control signals, a deviation check unit 62 for performing a deviation check between control signals, an exclusion signal selection unit 63 for excluding an abnormal signal, and a control command. The control command output unit 64 determines and outputs a signal.

The rate-of-change check unit 61 includes a control output signal U1 obtained by the control operation unit 4 and a control output signal U2 of the other control devices 2-2 and 2-3 fetched from the transmission processing unit 5.
U3 is input. The change rate check unit 61 stores past control signals of the control signals U1, U2, and U3,
The change rate G based on these past values and the present values is obtained. The calculation of the change rate is based on the simplified least squares method shown in (Equation 1), but can also be performed by the average gradient method or the like.

[0017]

Gi = (U _ij * 20 + U _ij-1 * 10−U _ij-2 *
10-U _ij-3 * 20) / T Here, T: sampling period i = 3: number of the control device 2-1 to j: current sampling Further, a change rate difference between the change rates G1 and G2 of each control apparatus. X
1, G2 and the change rate difference X2 of G3, G3 and the change rate difference X3 of G1 is obtained from equation (2), these rate of change difference X1~3 to diagnose whether the allowable value alpha ₁ below be predetermined .

[0018]

[Number 2] X1 = G1-G2 X2 = G2 -G3 X3 = G3-G1 Consequently, if the rate of change difference X1~X3 are all allowable value alpha ₁ below, all the normal each control output signal U1~U3 , in the case of all allowable value alpha ₁ or more are diagnosed every abnormal. If only the change rate deviation X1 exceeds the allowable value alpha _1, there is abnormal doubt either U1 or U2, further, X3
Is larger than the allowable value, it is diagnosed that U1 is abnormal.

The rate of change according to the above example is calculated by the control
And the rate of change may be exchanged via the transmission means 5.

FIG. 3 shows a flow of a diagnosis process of the change rate check section 61. The control signals U1,
For each of U2 and U3, the change rates G1, G2, and G3 are obtained, and further, the change rate differences X1, X2, and X3 between G1, G2, G2, and G3, and G3 are calculated (S101).

Next, at X1, X3 is allowable value alpha ₁ or more, X
2 alpha ₁ below or check (S102). If YES, the change rate abnormality flag YG ₁ corresponding to the signal U1 1
(S106). If S102 is NO, X1,
X2 is allowable value alpha ₁ or more X3 is alpha ₁ below or check (S103). If YES, the change rate abnormality flag YG ₂ corresponding to the signal U2 to 1 (S107). S10
If 3 is a NO, X1 in X2, X3 allowable value alpha ₁ or more
There α ₁ below or check (S104). If YES, the flags YG ₃ corresponding to the signal U3 and 1 (S1
08). S104 is if NO, X1, X2, X3 is checked whether the allowable value alpha ₁ or more (S105). As result is YES, and all YG ₁ ~YG _{3 1} (S10
9). S105 is equal NO, the and all _{YG 1 ~YG 3 0 (S110)} .

[0022] Step S110, all G1~G3 is or normal or, one allowable value alpha ₁ or more change rate difference X is a state in which the abnormal signal can not be identified. In the latter case, unrelated signal to the change rate difference was over, in the case of example X1> alpha ₁ signal G3, and determined to be normal signal, there is a method of the determination of the control command to be described later. According to this method, the multiplicity is reduced, but the abnormality detection is further accelerated.
This is advantageous for double multiplexing and the like.

The deviation check unit 62 controls the control signals U1 and U1.
2, deviation values of U2 and U3, U3 and U1 △ U1, △ U2,
△ U3 asking whether to check in the range absolute value of tolerance alpha ₂ which is predetermined for each deviation. In FIG.
6 shows a diagnosis processing flow of the deviation check unit 62. Abnormality setting the deviation abnormality flag YD ₁ ~YD ₃ control signal U1~U3 is performed as in the case of change rate check unit 61.

FIG. 5 shows a processing flow of the exclusion signal selecting section 63 for excluding an abnormal control signal. Control signals U1 to U3
The change at the time of abnormality is faster in the change rate difference than the signal deviation,
Usually, it becomes 1/5 to 1/10 and becomes apparent in any period. Therefore, the exclusion signal selection unit 63 performs the process on the result of the change rate check unit 61, and refers to the result of the deviation check unit 62 as a backup when no abnormality is found in the result.

First, it is determined whether or not all of the change rate abnormality flags YG _{1 to} YG ₃ from the change rate check section 61 are “0” (S301). If NO, the exclusion flag YEi is set to "1" and the others are set to "0" for the signal Ui of YGi = 1.

[0026] all of YG ₁ ~YG ₃ in step S301 is "
"When the deviation abnormality flag YDi from deviation check portion 62 is referenced, YD ₁ all ～YD ₃ is" 0 If determined whether 0 "(s303) a .YES, exclusion flag YE ₁
ＹYE ₃ are all set to “0” (S305). Step S
If 303 is NO, the exclusion flag YEi is set to "1" and the others are set to "0" for the signal Ui of YDi = 1 (s3
04).

It should be noted that the mutual diagnosis section 6 omits the backup check section 62 and provides the change rate check section 61.
In this case, the exclusion signal selection unit 63 is omitted, and the change rate abnormality flag YGi is used as the exclusion flag. Conversely, the combination with the change rate check is not limited to the deviation check. For example, it can be combined with self-diagnosis.

FIG. 6 shows a processing flow of the control command output unit 64.
Is shown. First, it is determined whether all the signal exclusion flags are “1” (S401). If all are “1”, the process moves to S404, and an intermediate value of the control signals G1 to G3 is selected as in the case where all the signal exclusion flags are “0”. Or the maximum value /
The selection of the minimum value may be performed. Note that the maximum value is selected
The maximum value is less than the set upper limit.
You. Similarly, if a minimum is selected, the minimum is set.
It is below the specified lower limit.

If NO in step S401, it is checked whether there are two signal exclusion flags "1" (S40).
2) If YES, Gi corresponding to the signal exclusion flag YEi = 0 is selected as the control command signal. On the other hand, if NO, it is checked whether there is one signal exclusion flag "1" (S403). If YES, the signal exclusion flag YEi =
An average value of the two control signals Ui corresponding to 0 is obtained as a control command signal. In this case, the maximum value (upper limit value) / minimum value (lower limit value) may be selected regardless of the average value.

As described above, in this embodiment, the control signals are all
If normal, those intermediate values are used as control command signals. one
If there is a control signal whose signal exclusion flag is “1”,
Are excluded, and only the normal control signal
Calculates the minimum value and uses it as a control command signal. Also, signal exclusion
When all the flags are “1”, the selection in S404 is performed.
The intermediate value as the control command signal
You. This is because all the multiplexed control devices are abnormal at the same time.
It can be said that there is nothing in reality, but as in this example
If an early diagnosis based on the rate of change
Depending on the setting, signal exclusion flag may be transiently applied to all control signals.
This is because there is a possibility that "1" is set. In this case, the book
In this embodiment, all cases are treated as normal,
Have been around. Note that there is a method in which the control command when the signal exclusion flags are all “1” retains the previous control command value regardless of the selection in S404.

FIG. 7 is a time chart for explaining the operation of control command selection according to this embodiment. FIG. 3A shows control signals U1, U by control devices 2-1, 2-2, 2-3.
The time transition of U2 and U3 is shown by a solid line. Control signal U
1 and U3 have been increasing in a similar manner since time t ₀ ,
U2 remains in a constant state.

In FIG. 3, the upper and lower limits of the deviation with respect to U2 are indicated by dotted lines (the upper and lower limits of the deviation between U1 and U3 are omitted).
Tolerance alpha ₂ as the upper limit of the deviation, if each control device is operated asynchronously so as not to determine that an abnormality signal incorrectly process change within the sampling period is set large to some extent.

FIG. 5B shows a case of a conventional deviation check (in this embodiment, a backup), and the selected control command U is indicated by a solid line. U1, U2, U3
If both signals are normal (exclusion flag “0”), 3
U2 which is an intermediate value in the signal is selected as the control command value. U3 is U3 is selected intermediate values from the time t ₁ becomes larger than U2. When abnormality in the time t ₂ at U2 is determined by the deviation check, the average value A of the control command value U1 and U3
Is output.

[0034] In this case, from time t ₀ to t ₂ the control signal U
2 is determined to be normal, an inaccurate control command U is output by the intermediate value selection logic, where the output of the average value should be based on the normal signals of U1 and U3. At time t ₂ when the abnormality of U2 is determined, the control instruction U is for changes stepwise becomes the average value output 2 signal from the intermediate value selection of the selected logic 3 signal, disturbance to the plant Becomes

FIG. 6C shows the case of the change rate difference check of the present embodiment, in which the change rates G1, G2, G3 of the control signals U1, U2, U3 over time, G2 and the other G signals.
1, the change rate difference for the deviation between the G3 tolerance alpha ₁ is shown. Change rate difference G2 and G1 is greater than the allowable value alpha ₁ at time t _3, the change rate difference G2 and G3 is beyond the allowable value alpha ₁ at time t _4.

FIG. 6D shows the selection of the control command U by the change rate check. At time t ₄ when the signal U2 is determined to be abnormal, the control command U from the intermediate value selection so far, the average value B is outputted is switched to the mean value selection signals U1 and U3. As a result, compared with the deviation check of FIG (b), since the early exclusion control signal U2 is made, t ₀ ~t can output a precise control command to the _fourth short step variation due switching of selection logic Can also be suppressed.

Although the above-mentioned allowable values of the change rate check and the deviation check are shown as fixed values, they may be predetermined values which change according to a predetermined parameter or a function of the process amount.

Further, the exclusion signal selecting section 63 and the control command output section 64 of this embodiment may be provided commonly to each control device. That is, the change rate check unit 6 of each control device
1 and the signals YG and YD from the deviation check unit 62 are received,
The control command is determined and output as one. Thereby, the configuration of the mutual diagnosis unit can be simplified.

Although the present embodiment has been described in terms of a triple configuration, it is of course possible to apply it to other multiplexing control devices. Also, the multiplexing configuration does not need to be fixed,
The present invention is also applicable to a case where the control device in the system changes the multiplexing configuration online.

As described above, according to the present embodiment, abnormality of each control device of the multiplexing control device is detected at an early stage, and a high-precision and stable control command is issued using a control signal from only a normal control device. Can be determined. Further, the abnormal control signal or device detected early is notified to the operator by an alarm or the like, and the spread of the abnormal situation can be prevented, so that the reliability of the plant operation can be further improved.

The present invention is a process control system in which the reliability and stability of a plant are required to be high, such as a recirculation flow control system of a nuclear power plant, or
A multiplexed control system that operates each control device asynchronously,
Furthermore, it is suitable for a distributed processing system that changes the multiplex configuration to online.

[0042]

According to the present invention, the abnormality of the output of each control device in the multiplexing control device can be quickly detected by the change rate check, so that it is possible to generate an accurate control command based on a normal control signal, and Can be prevented from occurring due to the switching of the output selection logic, and a highly reliable control command determination method for the multiplexing control device can be provided.

Further, according to the present invention, the reliability of the asynchronous multiplexing control device can be improved by providing the mutual diagnosis unit based on the change rate check, so that the system configuration can be easily and inexpensively constructed.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of a mutual diagnosis unit of a control device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a control system to which the multiplexing control device of the present invention is applied.

FIG. 3 is a processing flow of a change rate check unit.

FIG. 4 is a flowchart of a deviation check process.

FIG. 5 is a processing flow of an exclusion signal selection unit.

FIG. 6 is a processing flow of a control command output unit.

FIG. 7 is a time chart for explaining the operation of this embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Transmission line, 2 ... Multiplexing control device, 2-1, 2-2, 2
-3: Individual control device, 3 (3-1, 3-2, 3-3)
... Process input / output device, 4 ... Control operation unit, 5 ... Transmission processing unit, 6 ... Mutual diagnosis unit, 61 ... Change rate check unit, 62 ...
Deviation check unit, 63: Exclusion signal selection unit, 64: Control command output unit, 7: Setting device, 8 (81, 82, 83): Detection device, 9: Control target.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoichi Yoshida 5-2-1 Omikacho, Hitachi City, Ibaraki Prefecture Inside the Hitachi, Ltd. Omika Plant (56) References JP-A-62-5402 (JP, A) JP-A-56-7154 (JP, A) JP-A-59-71504 (JP, A) JP-A-60-15704 (JP, A) JP-A-61-103201 (JP, A) JP-A-59-214903 (JP, A) JP, A) JP-A-2-202602 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G05B 9/03

Claims (9)

(57) [Claims] 1. A control output determination method for a multiplexing control device, which determines a control command to a control target while mutually diagnosing each control signal by a plurality of control devices, comprising: A change rate difference between the change rates is obtained, a change rate diagnosis is performed as to whether the change rate difference is within a predetermined allowable value set in advance, and a change rate difference outside the allowable value is determined.
Excluding the control signal corresponding to the change rate difference as an abnormal signal,
The control signal corresponding to the change rate difference within the tolerance is a normal signal.
Wherein the control command is determined from the normal control signal . 2. A control output determining method for a multiplexing control device, which determines a control command to a control target while mutually diagnosing respective control signals from a plurality of control devices, comprising: A change rate difference between the change rates is obtained, a change rate diagnosis is performed as to whether or not the change rate difference is within a predetermined allowable value set in advance.
Intermediate value or according to the number of control signals determined to be normal
Determining the control command according to a selection criterion for an average value, a maximum value, or a minimum value . 3. Control signals from a plurality of control devices are synchronized.
Many of them determine control commands to the controlled object while diagnosing each other.
The control output determination method of the duplex controller, the rate of change of the control signal, respectively, based on the control signal at the control point from the current and the previous or current to a plurality of times past, determined by the average gradient method or the least squares method, wherein The rate of change between the rates of change is determined, and the rate of change of
Diagnosis of change rate whether it is within the set tolerance
Normal, corresponding to the change rate difference within the tolerance
A control output determination method for a multiplexing control device, wherein the control command is determined by selecting an appropriate control signal . 4. When all the control signals are determined to be normal by the change rate diagnosis according to claim 1, 2 or 3, or when it is difficult to specify an abnormal control signal, all of the control signals A signal deviation is determined to determine whether the signal is within a second allowable value set in advance, and a normal control signal corresponding to the signal deviation within the second allowable value is selected to execute the control command. A method for determining a control output of a multiplexing control device, characterized by determining. 5. The control command according to claim 1, wherein all of the control signals are determined as normal control signals when all of the change rate differences exceed the allowable value. A method for determining a control output of a multiplexing control device, characterized by using a previous control command. 6. A multiplexing control device comprising a multiplexing configuration of a measuring device for detecting a state of a control target and a control device for determining a control signal according to the state, wherein the control device is connected to another control device. Information transmission means for exchanging signals with each other, control calculation means for calculating the control signal in accordance with a deviation between an actual measurement value from a measuring device and a target value from a setting device, a control signal from the control calculation means, and Receiving control signals from other control devices from the information transmission means, and determining the rate of change of each control signal and the rate of change between the rates of change,
A change rate diagnostic unit that determines that a specific signal in the control signal is an abnormal signal when the change rate difference exceeds a first allowable value set in advance; and a normal signal excluding the abnormal signal. A multiplexing control device comprising: a mutual diagnosis unit having control command output means for determining the control command according to a predetermined selection criterion corresponding to the number. 7. The mutual diagnosing unit according to claim 6, wherein the mutual diagnosis unit obtains a signal deviation of each of the control signals, and when the signal deviation exceeds a second allowable value set in advance, the mutual diagnosis unit includes A multiplexing control device comprising a deviation diagnosis unit that determines a specific signal as an abnormal signal. 8. The multiplex control device according to claim 6, wherein each of said control devices is configured to operate asynchronously. 9. A multiplexing control device comprising a multiplexing configuration of a measuring device for detecting a state of a control target and a control device for determining a control signal according to the state, wherein another control device is included in the control device. Information transmission means for exchanging signals with each other, control operation means for calculating the control signal according to the deviation of the measured value from the measuring device and the target value from the setting device, and a control signal from the control operation means In response to a control signal from another control device from the information transmitting means, a change rate of each control signal and a change rate difference between the change rates are obtained, and the change rate difference is set to a first set value.
A change rate diagnostic unit that determines a specific signal in the control signal as an abnormal signal when the allowable value exceeds the allowable value, and is output from the change rate diagnostic unit of each control device in common to the control devices. Multiplexing characterized by comprising control command output means for determining the control command according to a predetermined selection criterion according to a normal signal excluding the abnormal signal and the number thereof according to the presence or absence of the abnormal signal. Control device.