JPS6326956B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plant control device, and more particularly to a plant control device in which a controller station for distributed control and a display station are connected to a peer-to-peer communication path, and which diagnoses its own state.

Conventionally, there has been a communication control system for distributed control called data freeway, but in the example that has been commercialized, it has been necessary to provide a management module on the communication path. In this method, communication is performed via the management module, which not only has low communication efficiency, but also has drawbacks such as the management module becoming a bottleneck in terms of reliability and an increase in the variety of manufacturing processes.

In recent years, the use of LSI communication control equipment has progressed, and by controlling the communication control method with inexpensive microcomputers, it is becoming possible to realize more efficient and reliable systems. We have not yet reached the point where we have established an optimal communication method for this purpose.

The purpose of the present invention is to connect each controller station equally to a communication path, to make a communication interface circuit and a self-diagnosis circuit for self-status diagnosis common to all controller stations, and to make the circuit suitable for LSI implementation. be.

Therefore, in order to connect each controller station equally to the communication path in a communication path that is highly expandable and has no bottlenecks in terms of reliability,
The system is such that the stations that have communication management rights are sent sequentially.
Self-diagnosis is performed by diagnosing whether the microcontroller is normal or abnormal and whether the communication interface circuit is normal or abnormal based on the presence or absence of changes in transmitted data. The communication interface circuit and self-diagnosis circuit for each station will be shared. Each station has the possibility of becoming a station in charge of transmission rights management, and has a mechanism to maintain the uniqueness on the communication path. In order to give order to the transmission right management between stations, the stations on the communication path are arranged in the order of their station numbers, or the time of the transmission right management monitoring timer is made to depend on the station number.

Embodiments of the present invention will be described with reference to FIGS. 1 to 6. This embodiment will be explained with reference to a plant control device in which a plurality of controller stations, display stations, and N:1 backup stations are connected to a dual-system peer-to-peer circular communication channel. Even if the type of communication changes or the communication path becomes a single system,
This does not impair the effects of the present invention. Here N:1
The backup station has a function of controlling the plant in place of the failed station when one of the plurality of controller stations fails.

In FIG. 1, a plurality of controller stations 1 and 2 control a plant 3 with plant operation signals 21 and 2, respectively.
2. On the other hand, the controller station 1 has transmitting/receiving signal lines 17a, 17b and switches 9a,
It is connected to partial communication paths 7a and 7b via 9b. Here, the partial communication channels 7a and 7b constitute a dual system. For ease of understanding, a and b used in this description correspond to two sets of partial communication channels 7a and 7b. Further, the communication path as a system is constructed by connecting the partial communication paths in operation for each station in a ring shape.

Further, the controller station 2 is also connected in the same way as the controller station 1.

Furthermore, the display station 5 is connected to the transmission/reception signal line 1 on the communication path 7.
7a, 17b and switches 9a, 9b. The display station 5 causes the display device 6 to display the plant status via the display signal 23, and key-in data input to the display device 6 is sent to the display station 5.

In addition, when one of the plurality of controller stations fails, the N:1 controller controls the plant 3 instead of the failed station.
Backup station 4 also transmits and receives signal lines 17a and 17b.
and communication paths 7a″, 7 via switches 9a, 9b.
connected to b″.

Switches 9a and 9b connected to each station are controlled by switch drive signals 19a and 19b.

The controller station 1 includes a communication interface circuit 11 that manages communication control, self-state diagnosis, and switch drive signals 19a and 19b for switches 9a and 9b.
It is comprised of a self-diagnosis switching/disconnecting circuit 12 that controls the plant 3, a plant control circuit 14 that controls the plant 3, and a control circuit 13 that controls these as a whole. Controller station 2 is similarly configured. Among these, the communication interface circuit 11, the self-diagnosis switching circuit 12, and the control circuit 14 are connected to the controller stations 1 and 2.
It is also a common circuit common to the N:1 backup circuit 4 and the display station 5. The N:1 backup station 4 has, in addition to the circuit group comprising the controller stations 1 and 2, a switching circuit 15 for switching plant operation signals 21 and 22 for replacing a failed station.

The display station 5 includes a display control circuit 16 in addition to common circuits 11, 12, and 13.

The connections between the partial communication paths 7a, 7a', the switch 9a, and each station will be explained with reference to FIG. 2. The communication path 7a from the upper station is connected to the contact 32 of the switch 31 and the received data 34a to each station. , the other contacts 33 of the switch 31 transmit data 3 sent from each station.
5a, and a switch state signal connected to one of the two contacts 32 and 33 is transmitted to the communication path 7a' to the lower station. When the switch drive signal 19a from each station is in a "bypass state", when each station does not exist, or when the power of each station is off, the switch 31 is electrically connected to the contact 32 side, and the communication path 7
a becomes a bypass state. On the other hand, when the switch drive signal 19a is in the "on" state, conduction occurs to the contact 33 side, and the transmission data from the upper station is received by each station, and the data delayed by several bits of the received signal or the transmission data from each station is It is transmitted to the lower station via the partial communication path 7a'. Note that the second partial communication path 7
b, the switch 9b and the connections to each station are the same as in FIG.

An example of the control circuit 13 will be explained with reference to FIG.
2. It is composed of a data memory 43, an input/output interface circuit 44, a data line 45, an address line 46, and a control line 47.
performs overall control of each station. The program memory 42 and data memory 43 contain communication control, switch control, and self-diagnosis functions common to each station, as well as functions specific to each station, that is, plant control functions for controller stations 1 and 2, and plant control functions for N:1 backup station 4. The display station 5 stores programs and data regarding the display control function and the switching function and the plant control function.

The interface circuit 44 controls an input/output control signal 48 that controls the self-diagnosis switching/disconnecting circuit 12 and the switching circuit 15 in the N:1 backup station 4.

Data lines 45, address lines 46 and control lines 47 are also used to control circuits not shown in FIG. For example, communication interface circuit 1
Connected to 1.

In this embodiment, it is explained that the control circuit 13 is composed of the microcontroller 41, the program memory 42, the data memory 43, the input/output interface circuit 44, the data line 45, the address line 46, and the control line 47. As long as the circuit has the functions of, for example, a one-chip microcontroller, the effects of the present invention are not impaired.
The circuit may include all or part of the functions of the above.

Next, the communication interface circuit 11 will be explained with reference to FIG.
2a and 62b, the selector 51 selects one of the communication paths by the communication path selection signal 61.
Either one of the received data is selected and sent to the selector 5 via the selector 52 and shift register 55.
connected to the other input of 2. Selector 52 is GA
One of the two input signals is selected by the station signal 60. This means that the station in charge of GA monitoring of the communication channel selects the received data delayed by a certain period of time via the shift register 55, while the station that does not have the right to transmit the communication channel selects the received data that is the output of the selector 51.
This becomes the received data 57 of the communication control circuit 56.

The communication control circuit 56 is a circuit that has the function of executing HDLC (High Data Link Controller) or SDLC (Serial Data Link Controller) procedures, which are standardized in communication control, and controls settings for communication control, transmission/reception data, and microcontroller. Connections are made through data lines 45, address lines 46 and control lines 47.

Transmission data 35a, 35 to communication paths 7a', 7b'
b is the output of the drivers 53a and 53b. Drivers 53a and 53b are communication control circuit 56
The input signal is transmission data 58 from .

GA monitoring station signal 60 and communication channel selection signal 6
1 is obtained from the input/output interface circuit 44. However, the GA station signal 60 is the same even if instructed by the communication control circuit 56 in another embodiment.

Next, the switching circuit 15, which is a component of the N:1 backup station 4, will be explained with reference to FIG.
A switching signal 24 from the control circuit 13 of the N:1 backup station 4 becomes an input to the decoder driver 71. The switching signal 24 indicates the address number of the failed station to be backed up and whether or not to back it up. When backing up the control station 1, the plant operation signal 21 can be connected to the plant control circuit 14 via the plant signal 74 of the backup station by turning on the switch 72. At the same time, the switch 77 is activated and the connection to the station 2 side is cut off. Switch 72 is driven by switch drive signal 76. When backing up the control station 2, the switch 73 is turned on and the plant operation signal 22 is connected to the plant signal 74 of the backup station. At the same time, the switch 77 is activated and the connection to the station 2 side is cut off. Switch 73 is driven by a switch drive signal 75. here switch 7
The reason why 2,73 is used is that insulation between each station is required, and the same applies to other insulation methods. In a plant control device that does not require insulation between stations, a plant operation signal can be selected for each station using a selector and a decoder.

Next, the self-diagnosis switching/disconnecting circuit 12 will be explained with reference to FIG. The self-diagnosis switching disconnection circuit 12 is
In order to use either of the two sets of communication paths 7a and 7b, both switches 9a and 9b are turned on and one is selected by the selector 51, or
Alternatively, if the control circuit 13 or the communication interface circuit 11 fails, it has a function of self-diagnosing that the corresponding station is malfunctioning and disconnecting the station from both of the two sets of communication paths 7a and 7b.

This is because when the control circuit 13 is normal, it generates a pulse signal that repeats periodically, and the transmission data always changes within a certain period of time, so the transmission data 35a, 35b control circuit normal signal 89 is "1". The output signals of pulse generation circuits 82, 85, and 83, which generate pulses every time the level of "0" changes, are used. The pulse generation circuit has a function of outputting a pulse with a fixed time width when there is a level change in the input signal, and outputting a pulse with a fixed time width when the next level change occurs in the input signal within the fixed time width. In other words, if there is a level change in the input signal within a certain period of time, the output of the pulse generation circuit will always be a level pulse, but if an abnormality occurs and there is no level change in the input signal, the output of the pulse generation circuit will be a pulse. will no longer occur.

From the above, switch drive signals 19a, 1
The conditions under which switch 9b turns on switches 9a and 9b are expressed by the following equation.

“On state” = (control circuit normal)/(no change in transmission data) In other words, when the communication interface circuit 11 and control circuit 13 are normal and there is a change in transmission data, the switch drive signals 19a and 19b are turned on. determined by the state. On the other hand, control circuit normal signal 8
If there is no change in the level of signal 9 or if there is no change in the transmitted data, the station is abnormal, and the switch drive signals 19a, 19b are switched to switches 9a, 19b.
9b instructs to enter the "bypass state", and the station is automatically disconnected from both communication paths 7a and 7b, so that the influence of the abnormality does not spread to other stations.

Next, the operation of the present invention will be explained using this embodiment. In this embodiment, controller stations 1, 2, N: 1
A total of four stations, a backup station 4 and a display station 5, are connected via a duplex peer-to-peer circular communication path 7, and each station can communicate with each other.

This communication system does not require the management module described in the prior art, and each station is connected equally with respect to the communication system. That is, there is only one station on the communication path that is given the right to transmit at a certain time. This transmission right is then handed over to lower-ranking stations in order.

When a station that was preparing to transmit to another station is given the right to transmit, it communicates with the other station, and when the communication is completed, it hands over the right to transmit to the lower station. When a station that is not ready to transmit is given the right to transmit, it simply transfers the right to the lower station. In this embodiment, the name GA (Go Ahead) is used to explain the communication command representing the transmission right.

This system allows each station to use the communication channel equally by transmitting transmission rights sequentially.

Each station transmits data indicating that it is normal to the N:1 backup station 4 and display station 5 at regular intervals. Since the failed station does not transmit this data, the receiving stations 4 and 5 can determine normality/abnormality. The normality/abnormality determination result is used by the N:1 backup station 4 to back up the controller stations 1 and 2, and by the display station 5 to display the status of each station.

When the N:1 backup station 4 recognizes a failure in one of the controller stations 1 and 2, the failure station transmits the plant operation signal 21 connected to the plant 3.
Or disconnect 22 and N:1 backup station 4.
In accordance with the switching signal 24, the switching circuit 15 selects the plant operation signal of the faulty station to control the plant 3 in place of the faulty station.

Controller stations 1 and 2 are in plant 3 during normal operation.
Since the status of the N:1 backup station 4 is transmitted to the N:1 backup station 4 at regular intervals, the N:1 backup station 4 can continuously control the plant 3 in place of the failed station after the switching process.

While the N:1 backup station 4 is controlling the plant 3 in place of the failed station, the operator who recognizes the failed station from the display station 5 repairs the failed controller station. When the faulty station is inserted or removed from the communication path, the corresponding switches 9a and 9b enter the "bypass state" as described above, and do not adversely affect the use of the communication path by other stations. After the faulty station is repaired or when a new controller station is inserted into the communication path, the control circuit 13 of the controller station
switches 9a and 9b until the initial state is set.
is set to the "bypass state", and after setting the initial state, the switches 9a and 9b are set to the "on state".

Next, a communication path failure detection and switching method will be explained.

If communication is currently carried out by selectively using the signal on the A side of the two sets of partial communication channels 7a and 7b, if one or more of the communication channel 7a, switch 9a, and communication interface circuit 11 fails. , it becomes necessary to switch the selection to the signal of another partial communication path 7b and perform communication.

A communication frame communicated using a communication channel includes communication data between stations or a command for transmission authority, and a communication command must always exist on a communication channel within a certain period. However, when a failure occurs in the communication path 7a, stations lower than the failure location cannot receive communication frames.

Therefore, when each station detects that it is no longer able to receive communication frames for a certain period of time or more, it uses the communication channel selection signal 61 to input received data from another communication channel 7b to the communication control circuit 56 via the selector 51. Furthermore, if the communication control circuit 56 of the upper station breaks down, erroneous data may be transmitted on the communication path, so the switch drive signal 19a of the lower station is changed to put the switches 9a and 9b into a "bypass state".
To prevent an adverse influence of a communication interface circuit 11 from spreading to a communication path.

Although this embodiment describes the case where the number of controller stations is two, there are switches 9 on the communication paths 7a and 7b.
By installing the required number of a and 9b in advance and increasing the number of switching circuits to improve the N:1 backup function, the number of control stations and the location where the control station can be set to the switch can be adjusted arbitrarily. , scalability can be increased.

Next, a method for monitoring a transmission right signal, which is the center of the present invention, will be explained using FIGS. 7 and 8.

The clock management routine in Figure 7 is started by a hard timer interrupt, updates (1) GA monitoring timer T _GA , (2) GA period timer T _GAC , and (3) other timers, and also monitors GA presence. and GA period two timeouts are handled as follows.

(a) Reset of GA monitoring and GA cycle timer (i) When sending GA signal (ii) When receiving GA signal (b) Processing timeout of GA monitoring timer (i) GA monitoring flag = 1 (ii) GA signal output (With transmitting station number) (c) GA cycle timer timeout processing (i) When GA monitoring flag = 1 GA signal output The GA monitoring flag is turned on and off under the following conditions.

(a) Turns ON when the GA monitoring timer times out (b) Turns OFF when the following conditions are met when receiving a GA signal with a transmitting station number [Conditions] Compare the own station number and the GA transmitting station number, and find that the own station number > GA Transmitting station number Next, the setting time of the timer will be explained. Normally, there is only one station in charge of GA monitoring, so in order to prevent multiple GA signals from unnecessarily existing on the communication path, the relationship between the GA monitoring timer and the GA period timer is determined by the quantization error of each station's timer. Considering the time Tq, set T _GA T _GAC +2.Tq.

In addition, in order to minimize the transient when GA disappears, which will be described in the next section, especially when the connection order of each station cannot be selected as described in the next section, the GA of the kth station is
The setting of the monitoring timer is T _GA,k =k・C ₁ +C ₂ .

Next, the effect of the present invention regarding the arrangement order of each station will be explained using FIG. Each station uses a self-running timer to monitor the presence or absence of a GA. Therefore,
If GA disappears from the communication channel, (GA of each station
If the monitoring timer is set to the same time for simplicity, the GA monitoring timer will time out at approximately the same time, and each station will transmit the GA signal.
In the example shown in Figure 9, the first station fails and the second and third stations
The following explanation assumes that the station and the sixth station transmit GAs almost simultaneously. That is, at time t ₁ , the first station
It is the station in charge of GA monitoring, and is the only GA signal present on the communication path. At time t ₂ , due to a failure of the first station,
Assuming that the GA signal disappears, the GA monitoring timer of each station operates, and at time t3, the 2nd, _3rd , and 6th stations time out and become the stations in charge of GA monitoring due to variations in each clock. There is. As a result, these three stations each have a transmitting station number.
Sends GA signal. Each station receives the GA of other stations and compares its own station number with the GA transmitting station number. In this case, except for the second station, the relationship is that own station number>GA transmitting station number, so at time _t4 , the station voluntarily withdraws from the station in charge of GA monitoring. Therefore, only the second station remains as the station in charge of GA monitoring, and is controlled with the GA signal on the communication path being the only one.

The present invention provides the following effects.

(1) GA signals that give order to the communication path are sent to all stations.
This can be achieved with a symmetrical structure in both hardware and software. This method is advantageous in that it simplifies the procedure for acquiring the transmission right in a normal state and also shortens the recovery time from an abnormal state.

(2) In the unlikely event that multiple GA signals exist,
By comparing the size of own station number and GA sending station number,
Since the station in charge of GA monitoring is withdrawn, the uniqueness of the GA signal can be satisfied with simple processing.

(3) When the GA disappears due to a failure in the station in charge of GA monitoring, the GA is regenerated by the monitoring timer of each station. At this time, the stations are arranged in such a way that the station numbers increase in the direction of signal flow, so that a state is returned to where only one GA signal exists by transmitting a plurality of GA signals almost once. That is,
Communication failure time during abnormalities is shortened.

(4) By setting the difference between the setting times of the GA monitoring timer and the periodic timer to twice the timer quantization error, if there is currently only one station in charge of GA monitoring, the station in charge of GA monitoring uses the GA periodic timer. ,
Can send GA signal in advance when it disappears. Therefore, the probability that two or more GA signals exist on the communication path and cause communication failure is reduced.

(5) When a station in charge of GA monitoring fails, if the GA monitoring time is determined depending on the station number, even if the order of each station on the communication path is disrupted, the number of stations temporarily in charge of GA monitoring will be reduced, and the GA monitoring time will depend on the station number. The transient until the signal becomes unique is shortened, and the communication failure time is shortened.

By adopting the GA monitoring mechanism described above, it is possible to improve the system reliability of communication systems using peer-to-peer communication channels through the self-diagnosis function of each station, communication path switching and disconnection function, and N:1 backup function. Effects can be obtained.

Furthermore, the communication interface circuit and self-diagnosis switching/disconnection circuit related to the communication system can be shared by each station, making it suitable for LSI implementation.

Furthermore, since the number of controller stations can be increased or decreased as desired, the scale of the plant control device can be easily changed by simply increasing or decreasing the number of the same control stations, resulting in the effect that the system is highly expandable.

In this embodiment, there is only one display station 5, but
A plurality of display stations can be connected to the communication paths 7a and 7b by increasing the number of switches 9a and 9b. This has the effect that, in the event of a failure of a certain display station, the function is taken over by another display station, and the function of the plant control device is not degraded. Furthermore, by mutually comparing and checking the status of the plant control equipment between multiple display stations or between a display station and an N:1 backup station, it is possible to obtain the effect that the display function or backup function can be made even more reliable. .

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a block diagram of the switch in Fig. 1, and Fig. 3 is a block diagram of the switch shown in Fig. 1.
4 is a configuration diagram of the communication interface circuit in FIG. 1, FIG. 5 is a configuration diagram of the switching circuit in FIG. 1, and FIG. 6 is a configuration diagram of the switching circuit in FIG. 1. 7 and 8 are explanatory diagrams of the GA monitoring mechanism, and FIGS. 9 and 10 are explanatory diagrams showing the effects of the present invention. 1, 2...controller station, 4...N:1 backup station, 5...display station, 7...peer communication path, 11...communication interface circuit, 12...
Self-diagnosis circuit.

Claims (1)

[Claims] 1 a plurality of controller stations divided by groups of digital control points or analog control points;
It consists of a functional module group including a display station that displays and operates the status of this controller station, and a peer-to-peer communication path that connects these functional modules on an equal basis.
The functional module shares one task related to a specialized function and a common communication/diagnosis function, and includes a communication interface circuit common to all functional modules and a self-diagnosis circuit for each functional module to diagnose its own status. In the connected plant control device, the communication path is connected in a ring, and the message transmission right signal is communicated with a mechanism that monitors with a monitoring timer whether or not a message transmission right signal exists on the communication path. A plant control device characterized in that its functional modules have a common mechanism for confirming that it is the only one on the road.