CN115002128A

CN115002128A - Control method for implementing main/standby reliability improvement of OPC client

Info

Publication number: CN115002128A
Application number: CN202210587516.5A
Authority: CN
Inventors: 徐庆中
Original assignee: Shanghai Corelli Software Co ltd
Current assignee: Shanghai Corelli Software Co ltd
Priority date: 2022-05-25
Filing date: 2022-05-25
Publication date: 2022-09-02
Anticipated expiration: 2042-05-25
Also published as: CN115002128B

Abstract

The invention discloses a control method for realizing main/standby reliability improvement of an OPC client. A plurality of OPC servers are arranged between the OPC client and the equipment PLC, and the configuration of the OPC servers is completely the same; the multiple OPC servers are communicated with the equipment PLC at the same time, and the OPC servers read and write the equipment PLC data; the multiple OPC servers are communicated with the OPC client at the same time, the OPC client accesses the multiple OPC servers at the same time, and the OPC servers are switched independently; an OPC connection manager is additionally arranged on the OPC client to be connected with a plurality of OPC servers and respectively connected with a data reading thread and a command processing thread. The method does not need an OPC manufacturer to provide a high-availability component, realizes high OPC availability in real time by a mode of simultaneously accessing a plurality of OPC servers at a client, does not need to manually switch the OPC servers, can improve the stability of the whole system, and avoids the reduction of productivity caused by the shutdown of a production line.

Description

Control method for implementing main/standby reliability improvement of OPC client

Technical Field

The invention belongs to the technical field of OPC UA communication, and relates to a control method for realizing the improvement of reliability of a main device and a standby device by an OPC client.

Background

An EAP system (Equipment Automation system) realizes real-time monitoring of a production line machine, and is an indispensable control system for factory Automation. The EAP system is closely related to the machine in the FAB, and the design and development of the system must be consistent with the actual production flow of the machine in the production line, so as to achieve the purpose of automatically controlling the production of the machine. All production processes, production data and machine state data are collected through an EAP system and then transmitted to corresponding databases of servers such as MES, FDC and the like, and the MES tracks and monitors product and equipment events through the data. In the communication of EAP and device (machine) online, OPC UA is a widely used technology.

In OPC UA (unified architecture for object linking and embedded process control) communication, an OPC client generally reads or writes data from an OPC server, and the OPC server is connected to a device PLC and actually writes the data into the device PLC, which can satisfy most of the requirements in a general scene, particularly the requirements for data acquisition. However, with the improvement of the processes in different industries, the automation degree of the equipment is improved, the requirements on OPC communication become higher and higher, especially after the production line is provided with the automatic conveying equipment, the production of the production line completely realizes full-automatic production, and at this time, when the OPC communication is abnormal, and the OPC server software or the operating system running the OPC server fails, the production of the whole production line is suspended, which affects the productivity of the plant. Thus, the need for high availability of OPC slowly has also emerged within different industries. Traditionally, OPC vendors were required to provide highly available components, which required separate procurement, and different OPC vendors on the market, some had highly available components, and some had no highly available components.

In summary, the high availability of the existing OPC communication requires purchasing highly available components of OPC manufacturers, re-purchasing, and is expensive, and time and labor consuming for updating and upgrading the OPC servers that have been purchased previously. If the availability is not improved, once a problem occurs, the influence on the capacity of the factory is large, and the influence is not acceptable to customers.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a control method for realizing main and standby reliability improvement of an OPC client, which can realize OPC high availability in real time without purchasing high-availability components and can improve the stability of the whole system.

The purpose of the invention is realized by the following technical scheme:

the invention discloses a control method for realizing the improvement of availability of a main backup for an OPC client, which comprises the following steps:

a plurality of OPC servers are arranged between the OPC client and the equipment PLC, and the configuration of the OPC servers is completely the same; the multiple OPC servers are communicated with the equipment PLC at the same time, and the OPC servers read and write the equipment PLC data; the multiple OPC servers are communicated with the OPC client at the same time, the OPC client accesses the multiple OPC servers at the same time, and the OPC servers are switched independently; the method for packaging and transforming the OPC client comprises the following steps: on the basis of the existing data reading thread, event processing thread and command processing thread of an OPC client, a control program module (namely an OPC connection manager) is additionally arranged; the OPC connection manager is respectively connected with a plurality of OPC servers; the OPC connection manager is respectively connected with a data reading thread and a command processing thread; the data reading thread is connected with the event processing thread.

Further, the working method of the data reading thread is as follows:

(1) circularly reading the value of a data bit (an event reporting bit or a normal running bit of equipment) defined by the configuration file, if the value is read normally, generating an event reporting message, and sending the event reporting message to an event processing thread for processing;

(2) if the reading fails, automatically switching to another OPC client connection to read data; after success, executing according to the previous step;

(3) if the reading is failed, waiting for a period of time, and circularly executing the previous step;

(4) reporting an error if the read failure exceeds the configured number of times;

(5) after reporting the error, the OPC client will attempt to reconnect.

Further, the processing method of the event processing thread comprises the following steps:

(1) after receiving the message, the event processing thread reads data according to logic;

(2) after reading the data, writing the signal of the event response bit and starting overtime detection;

(3) monitoring the value of the event reporting bit, and changing the value of the event response bit to 0(Off) after finding that the value of the event reporting bit is 0 (Off);

(4) simultaneously closing overtime monitoring;

(5) if a timeout occurs, an error is reported and the value of the event acknowledgement bit is changed to 0 (Off).

The data reading thread reads the device event signal, when monitoring the device event, the event processing thread reads the data and writes the event response bit signal according to the signal time sequence defined by the two parties, and the time sequence requirement is as follows:

1) after the equipment writes the data into the corresponding data area, the equipment PLC sets the event reporting bit to be 1 (namely On, On);

2) the device PLC started the T1 timer to check for a T1 timeout (T1 timeout is 4 seconds); in this time, the device PLC can no longer report any event using the same event reporting bit;

3) the EAP system reads data after receiving the signal of the event report bit as 1, and then sets the corresponding event response bit as 1 (On); simultaneously starting a T2 timer to check for a T2 timeout (T2 timeout is 2 seconds);

4) after receiving the signal that the value of the event response bit is 1(On), the equipment PLC modifies the event reporting bit to 0(Off) and then can continue to do subsequent actions;

5) after receiving the signal that the value of the event report bit is modified to be 0, the EAP system modifies the value of the event response bit to be 0 (Off); the EAP system will monitor the event report bit signal for a timeout period T2; if the value of the event report bit does not become 0(Off) beyond the T2 timeout (T2 timeout is 2 seconds), the EAP system will report an error.

Description of the drawings:

● the device vendor is to provide a T1 timer time setting function (default 4 seconds).

After the device PLC writes data into the corresponding data area, the content of the data area may not be changed during the same event interaction process, and the data is maintained until the next event flow starts.

Device events include a number, such as device alarms, device status, device panel ingress and egress, port status, and the like.

Further, the processing method of the command processing thread comprises the following steps:

(1) when finding that a command needs to be sent to the equipment, writing the data into a data area, changing the value of a command bit into 1(On), and simultaneously starting a T1 timer to monitor whether the response is overtime; if the reading fails, switching to another OPC client connection to execute the same operation;

(2) when the value of the command response bit is monitored to be changed to 1(On), reading the response data and the return value;

(3) change the value of the command bit to 0(Off), while turning Off T1 timeout monitoring;

(4) if a timeout occurs, an error is reported and the value of the command bit is changed to 0 (Off).

The command processing thread: the method comprises the following steps of issuing a command to equipment, wherein the command is mainly used for issuing various data such as a process menu (Recipe) parameter, time synchronization, issuing batch information and the like, an independent thread of an EAP system processes the command to issue, and a signal issued by the command needs to meet the following time sequence requirements:

1) after the EAP system writes the data into the corresponding data area, the EAP system modifies the value of the command bit into 1 (On);

2) the EAP system starts a T1 timer to check for a T1 timeout (T1 timeout is 4 seconds);

3) the PLC reads data after receiving a signal with a command bit value of 1(On), verifies the data after reading the data, executes a command, writes result data into a corresponding data area, and writes a return code of the execution result into a data area of the return code; then, the value of the corresponding command response bit is modified to 1 (On); at the same time, a T2 timer is started to check the T2 timeout;

4) the EAP system modifies the value of the command bit to 0 after receiving the signal that the value of the command response bit is modified to 1

(Off); if the device PLC does not modify the value of the command response bit to 1(On) within the time T1, the EAP system will alarm and automatically modify the value of the command bit to 0 (Off);

5) after receiving the signal that the value of the command bit is modified into 0, the equipment PLC modifies the value of the command response bit into O (off); the device PLC always monitors the value of the command bit within the timeout period of T2; if the value of the command bit is not modified to 0(Off) beyond the timeout T2, the device PLC reports an error (the timeout T2 is 2 seconds).

The device vendor is to provide T2 timer time setting function (default value of 2 seconds).

The invention discloses a control method for realizing master-slave availability improvement of an OPC client, which is mainly realized by the way that the OPC client simultaneously accesses a plurality of OPC servers and autonomously switches the OPC servers. The OPC client accesses the OPC server, mainly reads and writes PLC data through the OPC server, and then controls automatic production of a production line.

The invention has the beneficial effects that:

the control method for realizing the main and standby reliability improvement of the OPC client side realizes the control method for realizing the main and standby availability improvement of the OPC client side on the basis of software of the traditional OPC server, can realize the overall high availability of the OPC, avoids the problems of disconnection of the whole communication and production stop caused by the problem of a single OPC server, provides the high availability of a system, meets the requirement of full-automatic production of a factory, improves the production efficiency and avoids the capacity loss.

The control method for realizing the main and standby availability improvement of the OPC client does not need an OPC manufacturer to provide a high-availability component, realizes the OPC high availability in real time by a mode of simultaneously accessing a plurality of OPC servers at the client, does not need to manually switch the OPC servers, reduces the influence of an OPC server Down machine on production line production, and improves the stability of the whole system.

Compared with the prior art, the control method for improving the reliability of the main and standby OPC client sides has the following advantages that:

1. independent high-availability components do not need to be purchased, and the active-standby mode that multiple OPC servers are simultaneously accessed by OPC clients is adopted, so that real-time switching is realized, the cost is low, and the time is short.

2. The method for improving the availability of the main and standby equipment by using the OPC client avoids the reduction of the productivity caused by the shutdown of a production line, reduces production errors and improves the product quality.

Drawings

FIG. 1 is a diagram illustrating a conventional OPC control scheme in the prior art;

FIG. 2 is a schematic diagram illustrating an OPC client interrupting communication with a PLC when a problem occurs in an OPC server in the prior art;

FIG. 3 is a schematic diagram of multiple servers communicating with a PLC simultaneously in accordance with the present invention;

FIG. 4 is a schematic diagram illustrating that an OPC client communicates with a PLC without interruption when an OPC server fails;

FIG. 5 is a schematic diagram of a logic control module of a control program of an OPC client in the control method of the present invention;

FIG. 6 is a schematic diagram of the timing requirements of event processing threads in the present invention;

FIG. 7 is a schematic diagram of the timing requirements of a command processing thread in the present invention.

Detailed Description

The invention is further described below with reference to the following figures and examples.

Examples

As shown in fig. 3 to fig. 6, a control method for implementing the main/standby reliability improvement by an OPC client according to the present invention is as follows:

a plurality of OPC servers are arranged between the OPC client and the equipment PLC, and the configuration of the OPC servers is completely the same; the multiple OPC servers are communicated with the equipment PLC at the same time, and the OPC servers read and write the equipment PLC data; and the plurality of OPC servers are communicated with the OPC client at the same time, and the OPC client accesses the plurality of OPC servers at the same time to autonomously switch the OPC servers.

The invention discloses a control method for realizing main and standby reliability improvement of an OPC client, which is mainly realized in a mode that the OPC client accesses a plurality of OPC servers at the same time and autonomously switches the OPC servers. The OPC client accesses the OPC server, mainly reads and writes PLC data through the OPC server, and then controls automatic production of a production line. (the OPC client may read data from the OPC server or write data to the OPC server).

The conventional control method, the connection method of the OPC client, the OPC server and the PLC is shown in fig. 1.

In this way, when the OPC server has a problem, the communication between all OPC clients and the PLC is interrupted, the production line production is affected, and it is impossible to issue a Recipe, collect data, and control the production line production, as shown in fig. 2.

The technical concept of the control mode of the invention is as follows: to increase the availability of OPC servers, multiple OPC servers need to be deployed, and the multiple servers communicate with the PLC at the same time, as shown in fig. 3.

In this case, even if one OPC server has a problem, the OPC client can access the PLC through another OPC server to read and write PLC data. As shown in fig. 4.

Although the principle of the control method is simple, the OPC client needs to be encapsulated and modified to support the simultaneous access to two or more OPC servers, and meanwhile, the configuration of the two or more OPC servers is completely the same.

The method for packaging and transforming the OPC client comprises the following steps:

on the basis of the existing data reading thread, event processing thread and command processing thread of an OPC client, a control program module (namely an OPC connection manager) is additionally arranged; the OPC connection manager is externally connected with a plurality of OPC servers respectively; the OPC connection manager pair is respectively connected with a data reading thread and a command processing thread; the data reading thread is connected with the event processing thread.

For explaining the control method of the control program of the OPC client, the main logic control module thereof, as shown in fig. 5, performs the functions of data acquisition and instruction issue:

OPC server configuration

The OPC server must be configured to have at least 2, and the configuration must be identical. The maintenance of this block, i.e. modification of the configuration, adding nodes, deleting nodes, modifying nodes, must be synchronized.

OPC connection manager

The OPC connection manager is used for maintaining communication connection management from the OPC client to the OPC server according to the deployed OPC server; the connection or communication Channel (Channel) must be opened at the same time and remain in communication.

And the OPC connection manager establishes connection with the two OPC servers simultaneously according to the addresses of the OPC servers configured by the configuration file, manages the communication state from the OPC client to the OPC servers simultaneously, and detects the communication condition between the OPC client and the OPC server according to a return value of read-write data and a heartbeat signal.

3. Data Read (Read Data) thread

Data reading is divided into different types, namely an EQP Alive (normal running of equipment) signal for monitoring whether equipment or a PLC program runs normally or not, an Event (Event) signal representing the occurrence of an equipment Event and a data area of equipment parameters.

And writing data by the equipment PLC, and connecting an EAP system (equipment control program) On the OPC server to read data once every 4seconds On/Off, so that the EAP system reads the data and judges whether the equipment software normally runs.

Event signal, which is written by device software or PLC program, EAP system single thread reads data in real time, monitors whether Bit signal changes, so as to monitor the Event happening in the device.

The data area of the device parameters is read by the EAP system at regular time or triggered by conditions.

All the reading operations are executed through an API (application programming interface) of an OPC Client, the reading result is judged, if the reading fails, data reading is immediately tried through an OPC server of a standby machine (another standby OPC server), the reading result is judged again, and the reading failure is judged only when all the configured OPC servers fail to read.

4. Event processing (Event) thread

The data reading thread reads the device Event (Event) signal, and when the device Event (Event) is monitored to occur, the Event processing thread reads the data and the write Event response Bit (Event Reply Bit) signal according to the signal timing sequence defined by the two parties, and the timing sequence is required to be as shown in fig. 6:

1) after the device writes data to the corresponding data area, the device PLC sets an Event Bit to 1 (On).

2) The device PLC starts a T1 Timer (T1 Timer) to check for a T1 Timeout (Timeout, T1 Timeout is 4 seconds). Within this T1 timeout, the device PLC can no longer report any Event using the same Event reporting Bit (Event Bit).

3) The EAP system reads data after receiving a signal of an Event Bit (Event Bit) of 1(On), and then sets a corresponding Event Reply Bit (Event Reply Bit) to 1 (On). At the same time, a T2 Timer (T2 Timer) is started to check for a T2 Timeout (T2 Timeout, T2 Timeout is 2 seconds).

4) After receiving the signal that the value of the Event Reply Bit (Event Reply Bit) is 1(On), the device PLC modifies the Event report Bit (Event Bit) to 0(Off) and then can continue to perform subsequent operations.

5) The EAP system modifies the value of the Event Reply Bit (Event Reply Bit) to 0(Off) upon receiving a signal that the value of the Event report Bit (Event Bit) is modified to 0 (Off). The EAP system will monitor the Event Bit signal for a time out time period (T2 Timeout) at T2. If the value of the Event Bit (Event Bit) does not become 0(Off) beyond the T2 Timeout (T2 Timeout is 2 seconds), the EAP system reports an error.

Description of the drawings:

Device events include many, such as device alarms, device status, device Panel in and out, Port status, etc.

5. Command processing (Command) thread

Issuing a command to the device, which is mainly used for issuing various data such as a process menu (Recipe) parameter, time synchronization, issuing batch information, and the like, wherein the EAP system issues the command in a single thread processing manner, and a signal issued by the command needs to satisfy the following timing requirements as shown in fig. 7:

6) after the EAP system writes data to the corresponding data area, the EAP system modifies the value of the Command Bit (Command Bit) to 1 (On).

7) The EAP system starts a T1 Timer (T1 Timer) to check for a T1 Timeout (T1 Timeout, T1 Timeout is 4 seconds).

8) The device PLC reads data after receiving a signal of which the value of a Command Bit (Command Bit) is 1(On), verifies the data after reading the data, executes a Command, writes result data into a corresponding data area, and writes a return code of the execution result into a data area of the return code. Then, the value of the corresponding Command Reply Bit is modified to 1 (On). A T2 Timer (T2 Timer) is also started to check the T2 Timeout.

9) The EAP system modifies the value of the command bit to 0(Off) after receiving the signal that the value of the command response bit is modified to 1 (On). If the device PLC does not modify the value of the Command Reply Bit to 1(On) within time T1, the EAP system will alarm and automatically modify the value of the Command Bit to 0 (Off).

10) The device PLC modifies the value of the Command response Bit to o (Off) upon receiving a signal that the value of the Command Bit is modified to 0 (Off). The device PLC should always monitor the value of the Command Bit (Command Bit) for the T2 Timeout (T2 Timeout is 2 seconds). If the value of the time out time Command Bit (Command Bit) exceeding T2 is not modified to 0(Off), the device PLC reports an error.

Description of the drawings: the device vendor is to provide T2 timer time setting function (default value of 2 seconds).

Among the methods for achieving the same function are the following: and purchasing high-availability components of OPC manufacturers, and realizing high availability of OPC access by an OPC server. This approach is expensive, requiring upgrade updates for the old version of the OPC server, as well as upgrade costs.

Claims

1. A control method for realizing main and standby reliability improvement of an OPC client is characterized in that a plurality of OPC servers are arranged between the OPC client and a PLC (programmable logic controller), and the configuration of the OPC servers is completely the same; the multiple OPC servers are simultaneously communicated with the equipment PLC, and the OPC servers read and write the equipment PLC data; the multiple OPC servers are communicated with the OPC client at the same time, the OPC client accesses the multiple OPC servers at the same time, and the OPC servers are switched independently; the method for packaging and transforming the OPC client comprises the following steps: on the basis of the existing data reading thread, event processing thread and command processing thread of an OPC client, a control program module, namely an OPC connection manager is additionally arranged; the OPC connection manager is respectively connected with a plurality of OPC servers; the OPC connection manager is respectively connected with a data reading thread and a command processing thread; the data reading thread is connected with the event processing thread.

2. The OPC client apparatus of claim 1 which realizes the control method for improving the reliability of the main and standby apparatuses, wherein the working method of the data reading thread is as follows:

(1) circularly reading a data bit defined by the configuration file, namely a value of an event reporting bit or a normal running bit of the equipment, if the value is read normally, generating an event reporting message, and sending the event reporting message to an event processing thread for processing;

(5) after reporting the error, the OPC client will attempt to reconnect.

3. The control method for implementing active/standby reliability improvement by an OPC client according to claim 1, wherein the processing method of the event processing thread comprises the following steps:

(3) monitoring the value of the event reporting bit, and changing the value of the event response bit to 0 after the event reporting bit is found to be 0, namely, the closing;

(4) simultaneously closing overtime monitoring;

(5) if a timeout occurs, an error is reported and the value of the event acknowledgement bit is changed to 0.

4. The OPC client apparatus of claim 1 for implementing a master/slave control method for improving reliability, wherein the processing method of the command processing thread comprises the steps of:

(1) when finding that a command needs to be sent to the equipment, writing the data into a data area, changing the value of a command bit to 1, starting the data, and starting a T1 timer to monitor whether the response is overtime; if the reading fails, switching to another OPC client connection to execute the same operation;

(2) when the value of the command response bit is monitored to be changed into 1, reading the response data and the return value;

(3) changing the value of the command bit to 0 and turning off T1 timeout monitoring;

(4) if a timeout occurs, an error is reported and the value of the command bit is changed to 0.

5. The control method for implementing active/standby improvement of reliability by an OPC client according to claim 1, wherein a data reading thread reads a device event signal, and when monitoring that a device event occurs, an event processing thread reads data and writes an event response bit signal according to a signal timing defined by both parties, and the timing requirements are as follows:

1) after the equipment writes the data into the corresponding data area, the equipment PLC sets the event reporting bit to be 1;

2) the device PLC starts a T1 timer to check for a T1 timeout; in this time, the device PLC can no longer report any event using the same event reporting bit;

3) the EAP system reads data after receiving the signal of the event report bit as 1, and then sets the corresponding event response bit as 1; simultaneously starting a T2 timer to check the T2 timeout;

4) after receiving the signal that the value of the event response bit is 1, the equipment PLC modifies the event reporting bit to 0 and then can continue to do subsequent actions;

5) after receiving the signal that the value of the event report bit is modified to be 0, the EAP system modifies the value of the event response bit to be 0; the EAP system will monitor the event report bit signal for a timeout period T2; if the T2 timeout is exceeded, the value of the event report bit does not become 0 and the EAP system may report an error.

6. The control method for implementing active/standby reliability improvement by an OPC client according to claim 1, wherein the command processing thread: the method comprises the following steps of issuing a command to equipment, wherein the command is mainly used for issuing process menu parameters, synchronizing time and issuing various data of batch information, an EAP system processes the command by a single thread and the signal issued by the command needs to meet the following time sequence requirements:

1) after the EAP system writes the data into the corresponding data area, the EAP system modifies the value of the command bit into 1;

2) the EAP system starts a T1 timer to check T1 timeout;

3) the PLC reads data after receiving the signal of which the command bit value is 1, verifies the data after reading the data, executes the command, writes result data into a corresponding data area, and writes a return code of the execution result into a data area of the return code; then, modifying the value of the corresponding command response bit to 1; simultaneously starting a T2 timer to check the T2 timeout;

4) after receiving the signal that the value of the command response bit is modified to 1, the EAP system modifies the value of the command bit to 0; if the PLC of the device does not modify the value of the command response bit to 1 within the time T1, the EAP system alarms and automatically modifies the value of the command bit to 0;

5) after receiving the signal that the value of the command bit is modified into 0, the equipment PLC modifies the value of the command response bit into O; the device PLC monitors the value of the command bit for a timeout period T2; if the timeout T2 is exceeded and the value of the command bit is not modified to 0, the device PLC reports an error.

7. The OPC client side implementation control method for improving the reliability of the active/standby system according to claim 5 or 6, wherein the timeout time of T1 is 4 seconds.

8. The OPC client side implementation control method for improving the reliability of the active/standby system according to claim 5 or 6, wherein the timeout time of T2 is 2 seconds.

9. The control method for implementing active-standby reliability improvement by an OPC client as in claim 5, wherein after writing data into a corresponding data area, the content of the data area cannot be changed in the same event interaction process by the device PLC, and the data is maintained until the next event flow starts.

10. The control method for implementing active/standby reliability enhancement by an OPC client of claim 5, wherein the device event includes a device alarm, a device status, a device panel entry/exit, and a port status.