JPH0435761B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multiplexed process control system for controlling the status of a process.

[Technical background of the invention and its problems]

In recent years, process control devices used to control processes that require high reliability often have a multiplex configuration, such as duplication or triplication, in order to improve the reliability of the control device itself. A multiplexed configuration has a regular device and a standby device, and if the regular device is an old castle, the standby device is used, and multiple control devices are operated at all times, and the most reliable output is selected from among the outputs of those control devices. A method is used in which control is performed by selecting a large number of items using a deterministic decision. In general, the former method requires a failure detection circuit to detect equipment failure, and switching from the regular equipment to the standby system is performed when a failure is detected by the failure detection circuit. If an undetectable failure occurs, the switching operation will not be performed and the process control will become abnormal. Furthermore, as the fault detection ability of the fault detection circuit increases, the fault detection circuit itself becomes more complex, and failures of the fault detection circuit itself become a problem. Furthermore, it is difficult to detect all failures of the control device.

On the other hand, the latter method requires at least three control devices to make a majority decision, but it does not require a fault detection circuit, and the circuit that makes a majority decision has very simple functions such as selecting an intermediate value. It can be composed of Furthermore, no matter what kind of failure occurs in one control device, it is possible to maintain normal process control. For this reason, control devices using the latter method are often used to control processes that require particularly high reliability, such as nuclear power plants.

Figure 1 shows an example of this, where 1 is a controlled process, 2 is a setting device that outputs a target value _S1 of the process state, and 3 is a setter that outputs a target value _S1 and a feedback signal _S2 from process 1. A controller that performs control calculations to make the state of process 1 match the target value S ₁ and outputs a control signal S _3. 4 selects an intermediate value S ₄ from the three control signals S ₃ and outputs it. This is an intermediate value selection circuit. Setter 2 is an increase command S ₄ or a decrease command
_S5 allows the target value _S1 to be changed.

Now, of the triplex control device, setting device 2 of one series
Suppose that (for example, the A series) fails at time _t1 . As shown in Figure 2, the target values of each series S ₁ A, S ₁ B, S ₁
C (subscripts A, B, and C are A series, B series,
Shows C series. ) match, even if the A-series setter 2 fails and the target value S ₁ A becomes abnormal, the intermediate value selection circuit 4 selects the control signal S ₃ B or S ₃ C.
Since one of these is selected, the state of the process remains unchanged and normal control can continue.

However, even if the failure of the setter 2 of the A series is recovered at time t ₂ , the target value S ₁ of the A series will not be increased.
Since it is not changed unless S ₄ or reduction command S ₅ is input, the target value S ₁ A of the A series does not match the target values S ₁ B, S ₁ C of the other series (B series, C series). If process control is continued in such a state, then, for example, if the setter 2 of the B series fails at time _t3 , the target value _S1 of two series of the triplex control device will become abnormal. , normal process control is no longer possible.

Also, as mentioned above, the target values of each series S ₁ A, S ₁ B,
When S ₁ C is matched, a failure in setter 2 in one series will not cause a change in the process state;
As shown in the figure, if the target value S ₁ of each series has a deviation due to the drift of the setting device 2, etc., the process state will fluctuate by that deviation due to a failure of the setting device 2 of one series. . For example, if the A series fails at time t ₄ , the intermediate value S ₁ B is selected until time t ₅ , and S ₁ A is selected from time t ₅ to time t ₆ .
is selected, and since S ₁ C is selected after time t ₆ , the feedback signal S ₂ indicating the process state is
varies by the deviation amount due to the drift of the setting device 2, etc.

Furthermore, in order to eliminate the deviation of the target value _S1 between each series due to the drift of the setter 2, etc., it is necessary to give an independent increase command _S4 or decrease command _S5 to each series. If an independent increase command S ₄ or decrease command S ₅ is given for each series in this way, the normal target value changing operation becomes extremely complicated.
Normally, the increase command _S4 and the decrease command _S5 are common to each series. Therefore, if a deviation occurs in the target value S ₁ between each series, it is not possible to correct the deviation, so
The above-mentioned problem will occur.

[Purpose of the invention]

The present invention promptly and automatically zeroes out the deviation of the target value between multiplexes caused by failure or drift of the setting device, etc., thereby eliminating problems that may occur if control is continued in a state where the deviation has occurred. An object of the present invention is to provide a process control device that eliminates the above problems.

[Summary of the invention]

In order to achieve this objective, the present invention provides an intermediate value selection circuit that inputs the target values output from each multiplexed setter and selects an intermediate value of these, and the output of this intermediate value selection circuit The present invention is characterized in that by inputting the value into each setter, the target value can be automatically restored when the failure of one series of setters is restored.

[Embodiments of the invention]

The present invention will be explained below based on an embodiment shown in FIG. FIG. 4 is a block diagram of a process control device according to an embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 1 indicate the same or corresponding parts. The feature of this embodiment is that it is provided with a second intermediate value selection circuit 5 that inputs the target values S ₁ A, S ₁ B, and S ₁ C and selects an intermediate value of these. The output is added to the setting device as an external input, and a signal tracking means is built into the setting device as a function, and an operation switching circuit 6 is provided to output a command to activate or stop the following operation of the setting device by this signal tracking means. It is a point. This operation switching circuit 6 issues a follow-up command _S6 for causing the setter 2 to perform a follow-up operation so that the target value _S1 , which is the output of the setter 2, matches the external input. It also selects an increase command _S4 and a decrease command _S5 .

In the operation switching circuit 6, increase command S ₄ or decrease command S ₅ is ON.
In this case, follow-up command S ₆ is turned OFF and increase command S ₄
And when the reduction command _S5 is OFF, the follow-up command _S6 is turned ON. Therefore, the target value is set by increase command S ₄ or decrease command ₅ .
Unless _S1 is changed, the setter 2 will always follow the output of the intermediate value selection circuit.

Similar to FIG. 2, FIG. 5 shows the operation of the present invention in the case of a failure in the A-series setter 2 as an example. Even if the A-series setter 2 fails at time _t1 and the target value _S1A becomes abnormal, the second intermediate value selection circuit 5 is connected to the external input of the A-series setter 2.
The target value of the normal series selected by S ₁ B or S ₁
C is added. Therefore, if the failure of the A-series setter 2 is recovered at time _t2 , the setter 2 immediately performs a follow-up operation to make the target value S ₁ A match the external input, that is, S ₁ B or S ₁ C. , the target value S ₁ A automatically follows and matches the normal setter output of the other series. Therefore, even if, for example, the B-series setter 2 breaks down, normal control is possible.

Furthermore, even if a deviation occurs in the target value S ₁ due to the drift of the setting device 2 between multiplexing,
Since each setter 2 follows the intermediate value among the target values S ₁ A, S ₂ B, and S ₂ C selected by the second intermediate value selection circuit 5, the deviation between the target values S ₁ is always calculated. It is possible to set it to zero.

Furthermore, if the target value _S1 is changed by an increase command _S4 or a decrease command _S5 , a follow-up command is issued by the operation switching circuit 6.
Since _S6 is OFF and the setter 2 does not perform a follow-up operation to match the target value _S1 with the external input, the same changes as normal can be made.

Another embodiment of the present invention will be described based on FIG. FIG. 6 is a block diagram of another embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 4 indicate the same or corresponding parts. The difference from the one in FIG. 4 is that a comparator 7 is provided as a signal tracking means. That is, the output of the second intermediate value selection circuit 5 and the target value S ₁
is input into the comparator 7, and the comparator 7 can also generate the increase command _S4 and the decrease command _S5 . The comparator 7 uses the output of the intermediate value selection circuit 5 as the target value.
If the intermediate value selection circuit output is smaller than the target value _S1 , a decrease command _S5 is generated, and if the intermediate value selection circuit output is smaller than the target value _S1 , an increase command _S4 is generated. Therefore, even if a deviation occurs between the target values S ₁ , the comparator 7 increases the increase command S until they match the intermediate value of the target values S ₁ selected by the second intermediate value selection circuit 5. ₄ or the reduction command _S5 , it is possible to reduce the deviation to zero.

〔Effect of the invention〕

As explained above, according to the present invention, even if one series of setting devices 2 fails, the target value can be set immediately after the failure is recovered.
Since S ₁ recovers, it is possible to continue normal process control even if a failure subsequently occurs in another series. In addition, it is possible to always eliminate the deviation between the target values _S1 caused by the drift of the setting device 2, etc., so that when a deviation occurs, it is possible to prevent the process from occurring due to a failure of one series of setting device 2. There is no change in condition.

In the above description, a process control apparatus with a triplex configuration has been used to simplify the explanation, but the present invention is equally applicable to process control apparatuses with other multiplex configurations.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a conventional multiplexed process control device, FIGS. 2 and 3 are signal diagrams showing the operation of the conventional multiplexed process control device, and FIG.
The figure is a block diagram showing the configuration of an embodiment of the present invention.
FIG. 5 is a signal diagram showing the operation of an embodiment of the present invention;
FIG. 6 is a block diagram showing the configuration of another embodiment of the present invention. 1...Process, 2...Setting device, 3...Controller, 4...Intermediate value selection circuit, 6...Operation switching circuit, 7...Comparator, _S1 ...Target value, _S2 ...Feedback Signal, S ₃ ... Control signal, S ₄ ... Increase command,
_S5 ...Decrease command, _S6 ...Follow command.

Claims (1)

[Claims] 1. A controller having a multi-series configuration that calculates a control signal so that a process input matches a target value given from each setting device, and a control signal from the controller of each of these series. a first intermediate value selection circuit that selects an intermediate value among the setters, the first intermediate value selection circuit being provided for each setter of each series, inputting the target value from the setter of each series; a second intermediate value selection circuit that selects an intermediate value; and a target value of the setter such that the deviation between the target value from the setter and the output value of the second intermediate value selection circuit of the series is zero. 1. A process control device comprising: signal tracking means for increasing/decreasing . 2. The process control device according to claim 1, wherein the signal tracking means is incorporated as a function of the setting device of each system. 3. Comparison of inputting the signal tracking means with the target value of the setter of each series and the output value of the second intermediate value selection circuit of the series, and outputting an increase/decrease command to the setter so as to make the deviation zero. 2. The process control device according to claim 1, wherein the process control device is a device. 4 A controller with a multi-series configuration that calculates its control signal so that the process input matches the target value given from each setting device, and an intermediate value selected from among the control signals from the controllers of each of these series. a first intermediate value selection circuit that is provided for each setter of each series, and that inputs target values from the setters of each series and selects an intermediate value of the setters; a second intermediate value selection circuit; and a signal follower for increasing or decreasing the target value of the setter so as to make the deviation between the target value from the setter and the output value of the second intermediate value selection circuit of the series zero. and an operation switching circuit that stops the follow-up operation of the setter when a command to increase or decrease a target value is given to the setter from the outside.