JPH09265306A - Process controller and detection method for inoperative control circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure the safety of a plant operation by providing the information of a control circuit not performing an operation even once. SOLUTION: This process controller is provided with a PI/O 4 for inputting and outputting data between a plant 5, a programmable controller(PC) 1 for outputting the arithmetic result of a control program corresponding to input data as output data and a display means 2 for displaying the input data and the arithmetic result on a screen. A compiler 11 mounts the control program for which a storage processing 100 is added to the respective control circuits sectioned by braching points/merging points on a ladder diagram to a process control part 12. Every time of the execution of the respective control circuits in the control program, the storage processing 100 compares the value of this time of the arithmetic result with the value of a previous time, and in the case that it is changed, accumulates the number of times of change and stores it in a table 101. A retrieval processing 102 retrieves the table 101, detects the inoperative control circuit whose number of times of the change is 0 or equal to or less than a threshold value and displays it at the display means 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process control device, and more particularly to a detection system for a non-operation control circuit.

[0002]

2. Description of the Related Art Process control equipment is used to control a wide range of plants such as chemical, FA, electric power, nuclear power, railway, water and sewage.
It has been applied to surveillance. In general, the process control program is implemented by creating a ladder diagram or a logic circuit diagram representing a combination of plant control circuits on a screen, converting it with a compiler, and implementing it. This facilitates the creation of the program and reflects the execution result of the program in the ladder diagram and the logic circuit diagram on the screen to support the operation and monitoring of the plant.

FIG. 10 shows a block diagram of a conventional process control device. A programmable controller (hereinafter abbreviated as PC) 1 including a display device 2 receives a process signal from a plant 5 via a process signal input / output unit (hereinafter abbreviated as PI / O) 4 and a communication unit 3 such as a LAN. The plant 5 is controlled by taking in at the sampling cycle and outputting a control signal according to the result of the control calculation. In addition, the process data and the control calculation result are reflected on the control points of the ladder diagram on the screen and displayed so that they can be monitored. The process control program held by the process control unit 12 is converted from the ladder diagram displayed on the screen through the compiler 11 and stored in the main memory (not shown).

Further, the process control device constantly monitors the process abnormality by comparing the change of the process signal with the previous value or analyzing it in time series. When an abnormality occurs, an alarm is generated, and a failsafe or failsoft circuit or an emergency stop circuit is activated to ensure safety to prevent the occurrence or spread of an accident.

[0005]

The control circuit of the plant comprises a control circuit for normal processing, which operates frequently, and a control circuit for abnormal processing, which rarely operates. Since the control circuit for the abnormality processing does not operate during the period when the plant is operating normally, if it is attempted to operate it in an abnormal state, it may not operate normally and may cause a serious accident. Therefore, at the time of regular inspection of the plant, careful inspection including operation test of maintenance equipment is performed.

Under such circumstances, skilled workers are indispensable for maintenance and inspection of the plant, and the working time tends to increase more and more. However, in the case of a large-scale plant, it is practically impossible to disassemble all the equipment and inspect it without leaking it. In addition, contact failure such as relay contacts and rusting of parts often cause gradual progress and suddenly cause a malfunction for one day. It is one of the bottleneck for inspection.

In view of the problems of the prior art, it is an object of the present invention to detect the operating state of a control circuit of a plant online and provide a dead circuit detecting method for providing information of a dead or extremely small number of times of operation of the control circuit. And to provide a process control device. With this inoperative circuit information, it is possible to ensure the safe operation of the plant by, for example, maintaining and inspecting the target control circuit or element and shortening the parts replacement cycle.

[0008]

The above-mentioned object is to provide a PI / O that is input / output between plants and a PC that outputs the operation result of a control program according to the input data as output data.
In the process control device having display means for displaying the input data and the calculation result on the screen, the current value of the calculation result changes from the previous value each time each control circuit which is predeterminedly divided on the control program is executed. If this is the case, it is achieved by accumulating the number of changes and detecting a dead control circuit in which the number of changes is 0 or less than a threshold value.

Alternatively, a correspondence relationship between each control circuit divided into predetermined sections on the control program and each of the input data and each of the output data is initialized, and each time the control program is executed, the correspondence relationship is set. If the current value of the input data or the output data has changed from the previous value, the number of changes is accumulated, and a dead control circuit corresponding to the input data or output data in which the number of changes is 0 or less than a threshold value is detected. It is achieved by Here, the number of changes may be accumulated only for a plurality of previously designated input data / output data out of all input data and all output data input / output via the PI / O.

The change of the present value is judged to be changed when the absolute value of the difference between the previous value and the present value is a predetermined value or more, and the input data or the output data is not only a digital signal but also an analog signal. In the case of, it can be determined.

Further, the control program is implemented by compiling from a ladder diagram, and a predetermined section of the control circuit is divided at a branch point or a junction point on the ladder diagram as a boundary.

The process control apparatus to which the method of the present invention can be applied, when compiling the control program, immediately after each control circuit sectioned on the program, displays the present value and the previous value of the operation result in the control circuit. A compiler for comparing and adding a storage process for accumulating the number of changes when there is a change, a data table for accumulating and storing the number of changes of each control circuit each time the control program is executed, and a control program of the control program. After the execution, the display control means is provided for searching the data table and detecting and displaying the inoperative control circuit in which the number of changes is 0 or less than a threshold value.

Alternatively, it has a compiler for adding a reference process for associating each of the control circuits divided on the program with the input data or the output data when compiling the control program, and the control program, The reference process is executed in the initial process of the program, and the current value and the previous value of the input data or the output data are compared each time the control operation is executed by the program thereafter, and the value changes if it changes. A process control unit that also executes a storage process for accumulating the number of times; a data table that stores, for each of the input data or the output data, the number of changes by the storage process and a corresponding control circuit by the reference process; After execution, the data table is searched and the number of changes is 0. Or display control means for detecting and displaying an inactive control circuit having a threshold value or less.

[0014]

Embodiments of the present invention will be described below in detail.

[First Embodiment] FIG. 1 is a block diagram of a process control apparatus according to the present embodiment. The PC 1 provided with the display device 2 monitors and controls the plant 5 via the communication means 3 such as a LAN and the PI / O 4. The plant 5 includes a plurality of measuring means and control means (not shown), and a PC
Process signals and control signals are exchanged with 1.
These process signals and control signals include measured values such as temperature and pressure, analog signals 6 such as motor rotation speed and valve opening control, and digital signals such as ON / OFF of pump operation / stop and fault contacts. There is 7.

Process signal input / output control unit 15 of PC1
Has an input / output program and captures a process signal into the input data table 13 at a sampling cycle via the PI / O 4. Further, the control signal of the output data table 14 is output at the sampling cycle to control the plant 5. The process control means 12 has a process control program, executes control calculation while reading the process signal of the input data table 13, and writes the control signal according to the calculation result to the output data table 14. Further, the display device 2 displays the process signal and the calculation result via the display control means 10.
Directly on the screen of or reflected on the ladder diagram and displayed so that it can be monitored. The process control program is converted from the ladder diagram displayed on the screen through the compiler 11 and stored in the main memory (not shown).

FIG. 2 shows an example of a ladder diagram corresponding to the process control program. The ladder diagram is the logical product (AN
Combinations such as D), logical sum (OR), and negation (NOT) can be visually expressed by contact inputs and outputs in a matrix. In the example of FIG. 7A, contact input DI00
If 0 is ON and the contact input DI001 is OFF, or if the contact input DI002 is ON and the contact input DI003 is ON, the contact output DO000 is ON.

For example, the logical product of the input contact 20 and the input contact 21 corresponds to one of the normal processing control circuits of the plant, and the input contact 22 corresponds to one of the abnormal processing control circuits. Further, the output contact 24 corresponds to a control point of equipment such as a valve. In this way, the control circuit on the ladder diagram has a correspondence relationship with the control circuit or circuit elements of the actual plant (hereinafter simply referred to as control circuit). However, the control circuit on the ladder diagram also includes internal processing of software, and in order to avoid confusion, the control circuit on the ladder diagram will be simply referred to as a circuit or a unit circuit below.

The compiler 11 generates a process control program from this ladder diagram. Specifically, the circuit is divided into a circuit 1 to a circuit 3 at a branch point or a junction point in the ladder circuit and before the final output point (immediately before the output contact 24). Next, the AND of the input conditions of each circuit is calculated and temporarily stored in the work tables WK1 to WK3. As a result, the work table WK1 stores the state of the logical product of the input of the input contact 20 and the negative input of the input contact 21, the work table WK2 stores the input state of the input contact 22, and the work table WK3. The input state of the input contact 23 is saved.

FIG. 2B shows an equivalent circuit in which the ladder diagram shown in FIG. That is, the contact output DO000 in FIG. 9A is the logical product OR of the work table WK1 and the work table WK2 and the logical product AND of the work table WK3. It should be noted that this equivalent circuit can also be said to be a logic circuit diagram obtained by making a ladder diagram macro.

This embodiment is different from the conventional one (FIG. 10) in that (1) the storage processing 100 is added to the process control program at the time of conversion by the compiler 11, and (2) the storage processing 100 is executed. The number of operations of each circuit is set in the search data table 101, and (3) the display controller 1
The number of operations of each circuit is displayed on the screen by the search process 102 added to 0.

FIG. 3 shows a process control program.
This program is divided into the circuit 1 and the ladder diagram of FIG.
When converting to 2 or 3, the compiler 11 performs the storage processing 10
Automatically generated including 0. Here, the unit circuit to be stored and processed is 1 in the ladder diagram at the confluence or branch point.
Divide into blocks.

That is, in the case of the program of FIG. 2, contact input DI000 and contact input DI are added to the work table WK1.
The state of the logical product AND with the negation (NOT) of 001 is saved, and then the storing process 100 of WK1 is performed. Next, the state of the contact input DI002 is stored in the work table WK2, and the storage processing 100 of WK2 is performed. Further, the state of the contact input DI003 is saved in the work table WK3, and W
The storage process 100 of K3 is performed.

When this process control program including the memory process 100 is executed, every time the circuit state is changed,
The memory processing 100 accumulates the number of operation changes for each circuit and sets it in the search table 101. Display control unit 10
In the search process 102, the search data table 101 is searched, a circuit whose number of operation changes is 0 to a predetermined value or less is selected, and the circuit number and the number of times are displayed.

FIG. 4 shows a flow chart of the storage process. The storage process 100 is a subroutine of the process control program, and takes in the result (current value) of the circuit operation by execution of the process control program and the circuit number as arguments (S10). On the other hand, the previous value is stored in the search data table 101 at the time of the previous execution.

Next, it is determined for each circuit whether the current value has changed from the previous value (step S11). The judgment of the change is
It supports both digital and analog signals,
For digital signals, there is no change at | previous value-current value | = 0, and for analog signals | previous value-current value |>
χ (predetermined value for each circuit) is calculated, and if smaller than the predetermined value χ, no change is determined.

If there is a change in step S11, the circuit of which circuit number is executed is stored (S12),
The counter is incremented by "+1" (S13) and stored in the counter area of the search data table 101 (S14). Then, the current value is stored in the previous value area of the search data table 101 (S15). On the other hand, if there is no change in step S11, the current value is stored (S15) and the process ends.

FIG. 5 shows a flowchart of the search process. The search process 102 is executed after the process control program is processed, and in order to search for a circuit with a small number of changes,
The change count threshold value n is arbitrarily designated (S20). The threshold value n may be set in advance. Or,
The threshold value n can be changed or weighted by a circuit as time passes.

Next, the change number threshold value n and the count number are compared in the order of the circuit numbers in the search data table 101 (S21). If the count number is less than the threshold value n, the circuit number and the number of times of the corresponding circuit are displayed (S2).
2). At this time, the default display or the like may be performed by associating with the ladder diagram. On the other hand, if the number of counts is greater than the threshold value n, the process ends.

FIG. 6 shows a control program according to another ladder diagram. In the illustrated example, the control is more complicated than that in FIG. 2, but the circuit is divided at the branch point / confluence point of the ladder diagram, and the circuit 1
It is classified into ~ 9. Then, by storing the input condition and the logical operation of each unit circuit in the work table for each circuit, an equivalent circuit expressed in the circuit unit of FIG. Therefore,
By converting the circuit order by the compiler 11 and adding the storage processing 100 after each circuit, the number of operation changes of each circuit can be counted as in the case of FIG.

As described above, even when the control circuit is complicated and large-scale, the storage load is performed not for each input / output point of the ladder diagram but for each unit circuit in the present embodiment, so that the processing load is increased. And the processing speed of the parent process control program is not adversely affected. By the way, Figure 6
In the case of, the number of WK is 9 for 13 input / output points.
Therefore, the speed is increased by about 1.4 times as compared with the case where the storage processing is performed for each input / output point. The speed can be further increased in a more complicated circuit, for example, when a large number of contacts form a logical product (AND). It is also advantageous in terms of program capacity and data capacity.

As described above, according to the present embodiment, in the process control by the ladder diagram, the block divided at the branch point or the junction point of the ladder diagram is used as a unit circuit, and the number of operation change times of each unit circuit is executed every time the control program is executed. Therefore, it is possible to monitor the operating states of all the control circuits of the plant online, and it is possible to provide information on the control circuits that do not operate or have extremely few operations. This result can be reflected in the maintenance specifications for each control circuit of the plant, and can contribute to the safe operation of the plant.

Further, in this embodiment, since the control circuits are divided on the ladder sequence program, it is possible to monitor the operation status of the control circuit which performs so-called internal processing. As a result, it is possible to extract the program portion of the unit circuit in which the number of operations is 0. Therefore, by rechecking the program portion, a program error that cannot be detected by the sequence test with the fixed pattern may be found.

In the present embodiment, the control program using the ladder diagram is targeted, but a logic circuit diagram or the like may be used. Further, instead of the conversion program shown in the figure, the circuit may be divided on a normal application program and the above storage processing may be added.

[Second Embodiment] FIG. 7 is a block diagram of a process control apparatus according to the present embodiment. In the figure, the same elements as those in FIG. The feature of this embodiment is that the reference processing 103 is added to the process control program of the process control unit 12 by the compiler 1
1 is added, and a storage process 104 for counting and storing the number of times the data of the input / output data tables 13 and 14 is changed is added. In the search data table 105, the count of the number of changes, the previous value, and the corresponding circuit number by the reference process 103 are managed based on the input / output data.

FIG. 8 shows a process control program.
This program is automatically generated by the compiler 11 including the reference processing 103 when converting from the ladder diagram of FIG. 2 into the circuits 1, 2, 3, and 4 as described above. In the reference processing 103, the input / output data tables 13 and 14
The circuit number in which each data item is used is stored in the corresponding circuit area of the search data table 105 in the initial processing. After the process control program executes a predetermined control calculation, the storage processing program 104 is started, and the number of changes of the input / output data in the input / output data tables 13 and 14 is calculated.
It is stored in the search data table 105. After that, by the search processing 102 of the display control unit 10, the circuits whose number of operations is equal to or less than the threshold value are displayed on the screen as in the case of the first embodiment.

FIG. 9 shows a flowchart of the storage processing according to this embodiment. The storage process 14 first fetches the current values of the input data and the output data from the input / output data tables 13 and 14 (S30). Next, it is determined whether the previous value and the current value have changed from the constant value x (S31).
The previous value is stored in the search data table 101.
If there is a change in step S31, which input / output signal has changed is stored (S32), and the counter is set to "+".
1 ”(S33) and stores it in the counter area of the search data table 105 (S34). The above processing is looped for all input / output points (S35), and then the current value of each input / output signal is stored in the previous value area of the search data table 105 (S36).

Although the total number of input / output points is set in step S35, the process can be simplified by designating the target input / output points. In this case, it goes without saying that, of the process input / output signals, a signal leading to a serious failure is designated. Further, when the applied system is performing monitoring processing by comparing the previous value and the current value of the process input / output signal, the comparison result can be used.

According to this embodiment, the number of changes of the control circuit on the corresponding ladder diagram is monitored based on the process input / output signal managed by the system, so that the operation of the so-called internal processing part is monitored. In addition, since the data of the monitoring process can be used for the change of the input / output data, it is possible to provide the information of the control circuit having no malfunction or extremely few motions while simplifying the process.

[0040]

According to the present invention, the operating status of the control circuit of the plant can be monitored online through the execution of the process control program, and the information of the non-operation control circuit having 0 operations or extremely few operations can be provided. This is effective for ensuring the safe operation of the plant by shortening the maintenance cycle of control circuits or elements and the parts replacement cycle.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a process control device according to a first embodiment of the present invention.

FIG. 2 is a ladder diagram representing an example of a control program.

FIG. 3 is an explanatory diagram of a control program compiled by adding a storage process for each circuit from the ladder diagram of FIG. 2.

FIG. 4 is a flowchart showing an example of storage processing.

FIG. 5 is a flowchart showing an example of search processing.

FIG. 6 is a ladder diagram showing another example of the control program.

FIG. 7 is a configuration diagram of a process control device according to a second embodiment of the present invention.

8 is an explanatory diagram of a control program compiled by adding reference processing for each circuit from the ladder diagram of FIG. 2 in the second embodiment.

FIG. 9 is a flowchart showing an example of storage processing according to the second embodiment.

FIG. 10 is a block diagram of a process control device according to a conventional technique.

[Explanation of symbols]

1 ... PC (programmable controller), 2 ... display means, 3 ... communication means (LAN), 4 ... PI / O (process signal input / output means), 5 ... plant, 10 ... display control section,
11 ... Compiler, 12 ... Process control section, 13 ... Input data table, 14 ... Output data table, 15 ... Process signal input / output control section, 100 ... Storage processing, 101 ...
Search data table, 102 ... Search processing, 103 ... Reference processing, 104 ... Storage processing, 105 ... Search data table.

Claims (8)

[Claims] 1. A process signal input / output unit (hereinafter referred to as PI / O) for inputting / outputting between plants, and a programmable controller (hereinafter referred to as PC) for outputting a calculation result of a control program according to input data as output data. In a process control device having a display means for displaying input data and a calculation result on the screen, the current value of the calculation result changes from the previous value each time each control circuit divided into a predetermined section on the control program is executed. If so, the number of changes is accumulated, and the inactive control circuit in which the number of changes is 0 or a threshold value or less is detected. 2. A process signal input / output unit (hereinafter referred to as PI / O) for inputting / outputting between plants, and a programmable controller (hereinafter referred to as PC) for outputting a calculation result of a control program according to input data as output data. In a process control device comprising display means for displaying input data and calculation results on a screen, a correspondence relationship between each control circuit and each of the input data and each of the output data, which are predeterminedly divided on the control program, Initialization is performed, and each time the control program is executed, if the current value of the input data or the output data has changed from the previous value, the number of changes is accumulated, and the number of changes is 0 to a threshold value or less. Detecting a non-operation control circuit corresponding to the input data or output data. 3. The method according to claim 2, wherein the number of changes is accumulated for a plurality of input data and / or output data designated in advance among all input data and all output data input / output via the PI / O. And a method for detecting a non-operation control circuit. 4. The change of the current value according to claim 1, wherein it is determined that there is a change when the absolute value of the difference between the previous value and the current value is a predetermined value or more, and the input data or the output data is changed. A detection method for a non-operation control circuit, which enables determination not only for digital signals but also for analog signals. 5. The control program according to claim 1, wherein the control program is implemented by compiling from a ladder diagram, and the predetermined section of the control circuit is divided at a branch point or a junction point on the ladder diagram as a boundary. A method for detecting a non-operation control circuit characterized. 6. A process signal input / output unit (hereinafter referred to as PI / O) for inputting / outputting between plants, and a programmable controller (hereinafter referred to as PC) for outputting, as output data, a calculation result of a control program according to input data. In a process control device having a display means for displaying input data and a calculation result on a screen, at the time of compiling the control program, immediately after each control circuit divided on the program, the present value of the calculation result in the control circuit. And a compiler that adds a storage process for accumulating the number of changes when the values have changed, and a data table that accumulates and stores the number of changes of each control circuit each time the control program is executed, After the execution of the control program, the data table is searched to determine whether the number of changes is 0 to a threshold value or less. A process control device comprising display control means for detecting and displaying a control circuit. 7. A process signal input / output unit (hereinafter referred to as PI / O) for inputting / outputting between plants, and a programmable controller (hereinafter referred to as PC) for outputting, as output data, a calculation result of a control program according to input data. In a process control device having display means for displaying input data and calculation results on a screen, at the time of compiling the control program, each of the control circuits divided on the program is associated with the input data or the output data. A compiler for adding a reference process to be performed, and the control program, the reference process is executed in the initial process of the program, and the input data or the output data of the input data is output each time the control operation is executed by the program thereafter. Compare the current value with the previous value, and if there is a change, accumulate the number of changes A process control unit that also executes a storage process; a data table that stores, for each of the input data or the output data, the number of changes in the storage process and a corresponding control circuit in the reference process; A process control device comprising display control means for searching a data table and detecting and displaying an inactive control circuit whose number of changes is 0 or less than a threshold value. 8. The compiler according to claim 6 or 7, wherein the compiler divides the control circuit at a branch point or a junction point on a ladder diagram displayed on the screen of the display device, and performs a predetermined additional process. A process control device, wherein the process control device converts the control program while adding the above.