CN113485237A - PLC redundancy control system and method based on bus monitoring - Google Patents
PLC redundancy control system and method based on bus monitoring Download PDFInfo
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- CN113485237A CN113485237A CN202110933439.XA CN202110933439A CN113485237A CN 113485237 A CN113485237 A CN 113485237A CN 202110933439 A CN202110933439 A CN 202110933439A CN 113485237 A CN113485237 A CN 113485237A
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B19/00—Programme-control systems
- G05B19/02—Programme-control systems electric
- G05B19/04—Programme control other than numerical control, i.e. in sequence controllers or logic controllers
- G05B19/05—Programmable logic controllers, e.g. simulating logic interconnections of signals according to ladder diagrams or function charts
- G05B19/052—Linking several PLC's
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B2219/00—Program-control systems
- G05B2219/10—Plc systems
- G05B2219/14—Plc safety
- G05B2219/14014—Redundant processors and I-O
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Abstract
The invention relates to the technical field of automation control, in particular to a PLC redundancy control system and a PLC redundancy control method based on bus monitoring, which comprises a master PLC and a slave PLC which are connected with each other through a data line, wherein the master PLC is connected with an expansion board card group through a data bus; a signal switching device is arranged on the data bus, and the slave PLC is connected with the signal switching device through a monitoring line; the expansion board card group comprises at least one expansion board card, and the expansion board cards are mutually connected. According to the scheme, under the condition that the backup expansion board card is not added, the existing data flow is monitored, the data needing redundant backup is obtained, and the conversation content of the PLC and the expansion board card is processed in one conversation; the time overhead and the data overhead of the whole process are very small, and the data redundancy can be realized without completely depending on the data synchronization of the main PLC and the standby PLC. The scheme can not only save the time cost of system processing, but also improve the processing capacity and shorten the system response time.
Description
Technical Field
The invention relates to the technical field of automation control, in particular to a PLC redundancy control system and method based on bus monitoring.
Background
A system formed by a Programmable Logic Controller (PLC) and an expansion board thereof is an important component of a modern industrial automatic control system. The system formed by the PLC and the expansion board card has very high reliability and stability, so that the automatic control system can have higher reliability and stability. However, in more and more important occasions, the system needs to be continuously, stably and reliably operated automatically, and not only the PLC itself needs to be stable and reliable, but also the system formed by the PLC and the expansion board needs to be continuously and stably operated. To meet this demand, redundant systems have emerged.
Redundant systems establish a set of such systems: the same function unit in the system consists of two same devices which are mutually standby. Once one of the devices fails, the standby device seamlessly takes over the operation of the failed device. The key is seamless replacement and continued operation.
To achieve this, both devices need to ensure that their own limited data units are completely consistent, and the standby device needs to monitor the status of the working device, taking over the system opportunistically. Otherwise, the requirements of seamless replacement and continuous operation cannot be realized, so that system oscillation or system failure is caused, and the effects of improving the reliability and stability of the system cannot be achieved.
Fast and stable switching of the system is the central emphasis of the whole redundant system. At present, most methods adopted by the PLC with the redundancy function on the market realize the redundancy of the PLC, the standby PLC becomes a copy of the active PLC in a data synchronization mode, and when the active PLC fails, the standby PLC takes over the active PLC. The method has the advantages of simple structure and the defects that the expansion board cards of the PLC cannot be simply processed, particularly, the system data volume formed by two groups of the PLC expansion board cards is very large, the data change is very frequent, the processing logic during switching is also complex, and all data of the expansion system are difficult to process when the standby PLC takes over the system. Therefore, the PLC with the redundancy function in the market often uses two sets of the same expansion board cards, the switching of the whole expansion system is driven through the switching of the PLC, the control uncertainty is added to the relevant parts of the expansion board cards, and the system cost is very high.
Therefore, a technique for solving this problem is urgently required.
Disclosure of Invention
The invention aims to overcome the problems in the prior art and provides a PLC redundancy control system and a PLC redundancy control method based on bus monitoring, under the condition that an expansion board card is not added with backup, the data needing redundancy backup is obtained by monitoring the existing data flow, and the conversation contents of a PLC and the expansion board card are processed in one conversation; the time overhead and the data overhead of the whole process are very small, and the data redundancy can be realized without completely depending on the data synchronization of the main PLC and the standby PLC.
The above purpose is realized by the following technical scheme:
a PLC redundancy control system based on bus monitoring comprises a master PLC and a slave PLC which are connected with each other through data lines, wherein the master PLC is connected with an expansion board card group through a data bus; a signal switching device is arranged on the data bus, and the slave PLC is connected with the signal switching device through a monitoring line; the expansion board card group comprises at least one expansion board card, and the expansion board cards are mutually connected.
Further, if the data bus is a differential signal bus, the signal conversion device is a differential signal converter.
Further, if the data bus is an ethernet cable, the signal conversion device is an ethernet signal converter.
Furthermore, the master PLC and the slave PLC are PLCs with the same specification and redundant functions and are installed on a redundant adapter plate.
Furthermore, the redundant adapter plate comprises a main power supply interface, a standby power supply interface, a main PLC backboard interface, a standby PLC backboard interface and an expansion board card backboard interface, wherein the main power supply interface is used for being connected with an external main power supply, the standby power supply interface is used for being connected with an external standby power supply, the main PLC backboard interface is used for being plugged with the main PLC, the standby PLC backboard interface is used for being plugged with the slave PLC, and the expansion board card backboard interface is used for being plugged with the expansion board card set.
A control method of a PLC redundant control system based on bus monitoring comprises two conditions of a normal mode and a fault mode:
in the normal mode:
the main PLC receives a control program, issues a control instruction to the expansion board card group through the data bus, and receives the working process of the expansion board card group through the data bus;
the slave PLC synchronously backs up the control program received by the master PLC to obtain a backup control program, and monitors the control signal on the data bus in real time through the monitoring line to realize process monitoring and process backup of the backup control program;
in the failure mode:
the main PLC receives a control program, issues a control instruction to the expansion board card group through the data bus, and receives the working process of the expansion board card group through the data bus;
the slave PLC synchronously backs up the control program received by the master PLC to obtain a backup control program, and monitors the control signal on the data bus in real time through the monitoring line to realize process monitoring and process backup of the backup control program;
and if the master PLC fails, the slave PLC replaces the master PLC to realize the control of the expansion board card group, and the subsequent control of the backup control program is continued by taking the current process backup node as a starting point.
Advantageous effects
The PLC redundancy control system and method based on bus monitoring provided by the invention can acquire data needing redundancy backup by monitoring the existing data flow under the condition of not increasing the backup expansion board card, and process the conversation content of the PLC and the expansion board card in one conversation; the time overhead and the data overhead of the whole process are very small, and the data redundancy can be realized without completely depending on the data synchronization of the main PLC and the standby PLC. The scheme can not only save the time cost of system processing, but also improve the processing capacity and shorten the system response time.
Drawings
FIG. 1 is a schematic diagram of a PLC redundancy control system based on bus monitoring according to the present invention;
FIG. 2 is a schematic diagram of the normal operation of a PLC redundancy control system based on bus monitoring according to the present invention;
fig. 3 is a schematic diagram of the operation of the PLC redundancy control system based on bus monitoring in the failure mode according to the present invention.
Graphic notation:
the system comprises a master PLC (1), a slave PLC (2), a signal switching device (3), an expansion board card group (4), an expansion board card group (5), a data line (6), a data bus (7) and a monitoring line (8).
Detailed Description
The invention is explained in more detail below with reference to the figures and examples. The described embodiments are only some embodiments of the invention, not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1, a PLC redundancy control system based on bus monitoring includes a master PLC1 and a slave PLC2 connected to each other through a data line 6, the master PLC1 is connected to an expansion board card group 4 through a data bus 7; the data bus 7 is provided with a signal switching device 3, and the slave PLC2 is connected with the signal switching device 3 through a monitoring line 8; the expansion board card group 4 comprises at least one expansion board card 5, and the expansion board cards 5 are connected with each other.
In this embodiment, the data bus 7 may use a differential signal bus or an ethernet line,
when the data bus 7 is a differential signal bus, the signal switching device 3 is a differential signal switch, and the slave PLC2 is connected with the differential signal switch through a monitoring line 8, so as to realize real-time monitoring of the system.
When the data bus 7 is an ethernet cable, the signal switching device 3 is an ethernet signal adapter, and the slave PLC2 is connected to the ethernet signal adapter through a monitoring line 8, so as to implement real-time monitoring of the system.
In this embodiment, the master PLC1 and the slave PLC2 are PLCs having redundant functions and having the same specification, and are mounted on a redundant patch panel.
Specifically, redundant keysets includes main power source interface, stand-by power source interface, main PLC backplate interface, reserve PLC backplate interface and extension integrated circuit board backplate interface, main power source interface is used for being connected with outside main power source, stand-by power source interface is used for being connected with outside stand-by power source, main PLC backplate interface is used for pegging graft main PLC1, stand-by PLC backplate interface is used for pegging graft from PLC, extension integrated circuit board backplate interface is used for pegging graft extension board card group.
Based on the system, the scheme also provides a control method of the PLC redundancy control system based on bus monitoring, which comprises two conditions of a normal mode and a fault mode:
as shown in fig. 2, in normal mode:
the master PLC1 receives a control program sent by a host, stores the control program, distributes a control instruction to each expansion card 5 in the expansion board card group 4 through the data bus 7, and receives a work process of each expansion card 5 in the expansion board card group 4 through the data bus 7;
the slave PLC2 synchronously backs up the control program received by the master PLC1 to obtain a backup control program, and monitors the control signal on the data bus 7 in real time through the monitoring line 8, thereby realizing the process monitoring and process backup of the backup control program and achieving the purpose of real-time redundancy backup. Specifically, the slave PLC2 receives and processes all data of the data bus 7 formed by the master PLC1 and the expansion board card group 4, and determines which specific expansion board card 5 the data belongs to by identifying the identifier in the bus data frame from the data bus 7, and the slave PLC analyzes the data to be stored in a specific internal position according to the collected data, stores the data in an internal storage device, and forms a backup for the master PLC.
As shown in fig. 3, in failure mode:
the master PLC1 receives a control program sent by a host, stores the control program, distributes a control instruction to each expansion card 5 in the expansion board card group 4 through the data bus 7, and receives a work process of each expansion card 5 in the expansion board card group 4 through the data bus 7;
the slave PLC2 synchronously backs up the control program received by the master PLC1 to obtain a backup control program, and monitors the control signal on the data bus 7 in real time through the monitoring line 8, so that the process monitoring and the process backup of the backup control program are realized, and the purpose of real-time redundancy backup is achieved; specifically, the slave PLC2 receives and processes all data of the data bus 7 formed by the master PLC1 and the expansion board card group 4, and determines which specific expansion board card 5 the data belongs to by identifying the identifier in the bus data frame from the data bus 7, and the slave PLC analyzes the data to be stored in a specific internal position according to the collected data, stores the data in an internal storage device, and forms a backup for the master PLC;
when the master PLC1 fails, the slave PLC2 replaces the master PLCl to implement control over each expansion card 5 in the expansion card group 4, and continues to backup subsequent control of the control program with the current process backup node as a starting point, thereby implementing seamless docking.
In the system and the control method, in actual measurement, the communication period between the master PLC and the expansion board card is 500 microseconds, taking 256-byte data as an example, the time consumed by the slave PLC from data acquisition to system processing is less than 10 microseconds, the communication period is occupied by 2%, and the data processing capacity is more than sufficient for the whole bus.
Therefore, under the above test conditions, if a scheme that the two PLCs synchronize the data of all the expansion board cards is adopted, the time consumption is very large, and by using the method, 2000 times of data monitoring can be performed within 1 second, and the required data can be acquired from the PLCs at any time.
The above description is for the purpose of illustrating embodiments of the invention and is not intended to limit the invention, and it will be understood by those skilled in the art that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (6)
1. A PLC redundancy control system based on bus monitoring is characterized by comprising a master PLC and a slave PLC which are connected with each other through a data line, wherein the master PLC is connected with an expansion board card group through a data bus; a signal switching device is arranged on the data bus, and the slave PLC is connected with the signal switching device through a monitoring line; the expansion board card group comprises at least one expansion board card, and the expansion board cards are mutually connected.
2. The PLC redundancy control system based on bus monitoring of claim 1, wherein the data bus is a differential signal bus, and the signal switching device is a differential signal switch.
3. The PLC redundancy control system based on bus monitoring of claim 1, wherein the data bus is an Ethernet cable, and the signal switching device is an Ethernet signal switch.
4. The PLC redundancy control system based on bus monitoring as claimed in claim 1, wherein the master PLC and the slave PLC are PLCs with redundancy function with the same specification and are installed on a redundancy adapter plate.
5. The PLC redundancy control system based on bus monitoring of claim 4, wherein the redundancy adapter plate comprises a main power supply interface, a standby power supply interface, a main PLC backplane interface, a standby PLC backplane interface and an expansion board backplane interface, the main power supply interface is used for being connected with an external main power supply, the standby power supply interface is used for being connected with an external standby power supply, the main PLC backplane interface is used for being plugged with the main PLC, the standby PLC backplane interface is used for being plugged with the slave PLC, and the expansion board backplane interface is used for being plugged with the expansion board card set.
6. The control method of the PLC redundancy control system based on bus monitoring as claimed in claim 1,
the main PLC receives a control program, issues a control instruction to the expansion board card group through the data bus, and receives the working process of the expansion board card group through the data bus;
the slave PLC synchronously backs up the control program received by the master PLC to obtain a backup control program, and monitors the control signal on the data bus in real time through the monitoring line to realize process monitoring and process backup of the backup control program;
and if the master PLC fails, the slave PLC replaces the master PLC to realize the control of the expansion board card group, and the subsequent control of the backup control program is continued by taking the current process backup node as a starting point.
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| CN202110933439.XA CN113485237A (en) | 2021-08-13 | 2021-08-13 | PLC redundancy control system and method based on bus monitoring |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114326366A (en) * | 2021-12-02 | 2022-04-12 | 珠海格力电器股份有限公司 | Soft redundancy control system and configuration method thereof |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114326366A (en) * | 2021-12-02 | 2022-04-12 | 珠海格力电器股份有限公司 | Soft redundancy control system and configuration method thereof |
| CN114326366B (en) * | 2021-12-02 | 2023-09-12 | 珠海格力电器股份有限公司 | Soft redundancy control system and configuration method thereof |
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