CN112019416A - EtherCAT-based redundant communication method - Google Patents
EtherCAT-based redundant communication method Download PDFInfo
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- CN112019416A CN112019416A CN201910455390.4A CN201910455390A CN112019416A CN 112019416 A CN112019416 A CN 112019416A CN 201910455390 A CN201910455390 A CN 201910455390A CN 112019416 A CN112019416 A CN 112019416A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
- H04L12/42—Loop networks
- H04L12/437—Ring fault isolation or reconfiguration
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/22—Arrangements for detecting or preventing errors in the information received using redundant apparatus to increase reliability
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Abstract
The invention discloses a redundancy communication method based on EtherCAT, which solves the problems of real-time performance, certainty and reliability of industrial Ethernet communication. The method provides the industrial Ethernet with real-time performance and certainty based on EtherCAT, improves the network reliability by utilizing redundant communication, and solves the problems. The redundant communication is that a ring network topology structure is used, the master station adopts a double network card, and a bidirectional ring structure is designed by utilizing the automatic loopback function of an EtherCAT slave station control chip, so that the network automatically loops back at a fault point; the redundancy control layer is added in the EtherCAT main station, the link fault point is judged on the premise of not influencing the function of the application layer, the redundancy information and operation are shielded for the application layer, the influence of the link fault on the network is eliminated, the network has a self-healing function, and the reliability of the network is improved.
Description
Technical Field
The invention relates to an EtherCAT redundant communication method, in particular to an EtherCAT-based redundant communication method for industrial production.
Background
The traditional industrial Ethernet adopts a CSMA/CD medium access control mechanism, each node on the network needs to obtain the transmission right through competition, the time delay is unpredictable, data collision can be generated after transmission, the network is a non-deterministic network, the real-time requirement of data transmission cannot be ensured, single-point faults are difficult to isolate, the whole network is easy to spread, and the requirement of the current industrial production on the industrial Ethernet is difficult to meet.
Disclosure of Invention
Aiming at the defects of instantaneity, determinacy and reliability of the traditional industrial Ethernet, the technical problem to be solved by the invention is to provide a redundancy communication method based on EtherCAT for industrial production.
In order to solve the technical problems, the invention adopts the technical scheme that: a redundant communication method based on EtherCAT, a main station and N slave stations are connected in turn to form a loop, the main station is provided with two network cards, namely a network card 1 and a network card 2, and is used for realizing a bidirectional loop structure, and the method comprises the following steps:
the network card 1 sends the Ethernet frame and receives the Ethernet frame returned from the station through the network card 2, so the loop is normal;
the network card 1 sends the ethernet frame and receives the ethernet frame returned from the station 1, and the network card 2 sends the ethernet frame and receives the ethernet frame returned from the station N, that is, the network card and the station form two loops, and if at least one of the above situations occurs, the loop fails.
When a link failure occurs, the master station and the slave station form two loops, specifically as follows:
the master station sends Ethernet frames through the network card 1, sequentially loops from the slave station 1 to the slave station i, sequentially from the slave station i to the slave station 1, and then is received by the network card 1, so that a loop I is formed;
after the loop I is formed, the master station sends an Ethernet frame through the network card 2, sequentially loops from the slave station N to the slave station N-j, sequentially from the slave station N-j to the slave station N, and then is received by the network card 2 to form a loop II; wherein i and j represent the serial numbers of the slave stations, and i + j is less than N.
In the two network cards provided in the master station, each network card can be used for transmitting and receiving data.
Before the master station sends the Ethernet frame, network information in the master station is configured; the network information comprises a network topology structure, an initialization command of each slave station and communication command Ethernet frames needing to be sent periodically.
The master station configuration tool uses the slave station description file ESI to compile a network information file ENI in an offline mode, and uses the ENI file to configure the master station, wherein the ESI file and the ENI file are in an XML format.
The master station sends the ethernet frame through the network card 1 and receives the ethernet frame returned by the slave station through the network card 2, which is as follows:
the network card 1 of the master station sends Ethernet frames, each slave station extracts or inserts data from the received Ethernet frames, then the processed Ethernet frames are transmitted to the next slave station according to the sequence of the slave station, and finally the slave station N sends back the Ethernet frames processed by each slave station and receives the Ethernet frames by the network card 2 of the master station.
The destination address of the Ethernet frame sent by the network card 1 is the MAC of the network card 2, and the source address is the MAC of the network card 1; the destination address of the ethernet frame sent by the network card 2 is the MAC of the network card 1, and the source address is the MAC of the network card 2:
after receiving the ethernet frame, the network card 1 determines the destination address of the ethernet frame: if the destination address of the ethernet frame is the MAC of the network card 2, it indicates that the looped ethernet frame is received and the loop is faulty; otherwise, the loop is normal;
after the network card 2 receives the ethernet frame, the destination address of the ethernet frame is determined: if the destination address of the Ethernet frame is the MAC of the network card 1, the looped Ethernet frame is received, and the loop fails; otherwise, the loop is normal.
The method for determining the position of the fault slave station by the master station according to the returned Ethernet frame comprises the following steps:
the master station sets an expected value for each work counter WKC used for each slave station communication sub-message; when the master station sends Ethernet frames through the network card 1 or the network card 2, all WKCs are initially 0; when the Ethernet frame passes through a slave station and data extraction or insertion is realized, the WKC is increased;
after the primary station receives the looped Ethernet frame, comparing the WKC value of each secondary station with the expected value of each secondary station respectively; if the communication is equal, the corresponding slave station is communicated correctly; if the WKC is not equal but not 0, the message processing has problems; and if the WKC is equal to 0, the corresponding slave station fails in communication.
A master station based on EtherCAT comprises a sending/receiving unit and two network cards connected with the sending/receiving unit, namely a network card 1 and a network card 2;
the network card 1 is used for sending and receiving Ethernet frames;
the network card 2 is used for sending and receiving Ethernet frames;
a transmitting/receiving unit for performing the steps of:
the network card 1 sends the Ethernet frame and receives the Ethernet frame returned from the station through the network card 2, so the loop is normal;
the network card 1 sends the ethernet frame and receives the ethernet frame returned from the station 1, and the network card 2 sends the ethernet frame and receives the ethernet frame returned from the station N, that is, the network card and the station form two loops, and if at least one of the above situations occurs, the loop fails.
The invention has the beneficial technical effects and advantages that:
1. the invention adopts the EtherCAT real-time industrial Ethernet technology, and ensures the real-time performance and the certainty of communication.
2. The invention utilizes the redundant communication to enable the network to have the self-healing function, thereby improving the reliability of the network.
3. The invention can judge the link fault range and is convenient for the detection and maintenance of the system.
4. The invention is employed in a master station.
Drawings
FIG. 1 is a schematic view of the overall structure of the present invention;
FIG. 2 is a flow chart of the redundant communication of the present invention;
fig. 3 is a communication diagram when a link fails according to the present invention.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings.
The invention discloses a redundancy communication method based on EtherCAT, which solves the problems of real-time performance, certainty and reliability of industrial Ethernet communication. The method provides the industrial Ethernet with real-time performance and certainty based on EtherCAT, improves the network reliability by utilizing redundant communication, and solves the problems. The redundant communication is that a ring network topology structure is used, the master station adopts a double network card, and a bidirectional ring structure is designed by utilizing the automatic loopback function of an EtherCAT slave station control chip, so that the network automatically loops back at a fault point; the redundancy control layer is added in the EtherCAT main station, the link fault point is judged on the premise of not influencing the function of the application layer, the redundancy information and operation are shielded for the application layer, the influence of the link fault on the network is eliminated, the network has a self-healing function, and the reliability of the network is improved.
The redundant control layer is mainly responsible for filling Ethernet frames, detecting looped Ethernet frames, coordinating the sending and receiving of the two network card Ethernet frames and judging the link fault range.
Fig. 1 is a schematic view of the overall structure of the present invention. A redundancy communication method based on EtherCAT comprises the following steps:
step 1, a master station is provided with two network cards, each network card can send and receive Ethernet frames, and an EtherCAT network adopts a ring topology;
step 2, configuring network related information in the EtherCAT master station, wherein the network related information comprises a network topology structure, an initialization command of each slave station, communication command Ethernet frames needing to be periodically sent and the like;
step 3, the EtherCAT master station periodically sends commands and receives data returned by the slave station, and the commands are sent from the network card 1 and received by the network card 2 under the normal condition of a link; after a link failure occurs, one loop is divided into two loops: the Ethernet frame is sent by the network card 1 of the loop I, received by the network card 1 after being looped back, and the Ethernet frame is handed to the loop II by the redundancy control layer, sent by the network card 2 and received by the network card 2 after being looped back.
In the step 1, the master station is provided with two network cards, each of which can send and receive ethernet frames, and the EtherCAT network adopts a ring topology. The receiving unit is simultaneously connected with the receiving ends of the two network cards, the sending unit is simultaneously connected with the sending ends of the two network cards, the sending end of the slave station 1 is connected with the receiving end of the network card 1, and the receiving end of the slave station 1 is connected with the sending end of the network card 1; the sending end of the slave station N is connected with the receiving end of the network card 2, and the receiving end of the slave station N is connected with the sending end of the network card 2, so that a bidirectional ring structure is realized.
In the step 2, network related information in the EtherCAT master station is configured, including a network topology structure, an initialization command of each slave station, an ethernet frame of a communication command needing to be periodically sent, and the like; the master station configuration tool uses the slave station description file ESI to compile a network information file ENI in an offline mode, and uses the ENI file to configure the master station, wherein the ESI file and the ENI file are in an XML format.
In the step 3, the EtherCAT master station periodically sends ethernet frames to each slave station according to the configuration of the ENI file. Under the normal condition of a link, the master station sends an Ethernet frame through the network card 1, the slave station extracts or inserts data in the Ethernet frame, then the processed Ethernet frame is transmitted to the next EtherCAT slave station, and the last EtherCAT slave station sends back the completely processed Ethernet frame and sends the completely processed Ethernet frame to the network card 2 of the master station as a response Ethernet frame to receive the Ethernet frame. And after receiving the response Ethernet frame, the master station diagnoses the link fault by the redundancy control layer and judges the fault range. Under the condition of link failure, due to the automatic loopback function of the control chip of the slave station, the Ethernet frame sent by the network card 1 of the master station is received by the network card 1 of the master station after loopback; the redundancy control layer hands the Ethernet frame to a loop II, the Ethernet frame is sent by the network card 2, and the Ethernet frame is received by the network card 2 of the main station after being looped back.
As shown in fig. 2, the redundant communication flow is as follows.
Configuring network related information in an EtherCAT main station;
the EtherCAT master station periodically sends commands and receives data returned by the slave station:
the destination address of the Ethernet frame sent by the network card 1 is the MAC of the network card 2, the source address is the MAC of the network card 1, the destination address of the Ethernet frame sent by the network card 2 is the MAC of the network card 1, the source address is the MAC of the network card 2, and the master station and the slave station judge whether the frame is transmitted correctly through an Ethernet frame detection sequence FCS.
Under the condition that the link is normal, the main station receives the Ethernet frame sent by the network card 1 by the network card 2 of the main station in response to the Ethernet frame.
Under the condition of link failure, the Ethernet frame sent by the network card 1 by the master station responds that the Ethernet frame is received by the network card 1 of the master station due to the automatic loopback function of the control chip of the slave station; the master station receives the ethernet frame sent by the network card 2 in response to the ethernet frame.
After the network card 1 receives the data, the redundancy control layer judges the destination address of the Ethernet frame, and if the destination address is the MAC of the network card 2, the loopback Ethernet frame is received; after the network card 2 receives the data, the redundancy control layer judges the destination address of the ethernet frame, and if the destination address is the MAC of the network card 1, the loopback ethernet frame is received.
As shown in fig. 3, the communication mode at the time of the link failure is as follows.
When the master station initiates period control, a desired value is set for the WKC of each slave station sub-message, the WKC is initially 0 during transmission, and when an ethernet frame passes through the slave station and is correctly processed (data extraction or insertion is realized), the WKC is increased, and the specifically increased value is related to the command type of the slave station sub-message, as shown in table 1:
TABLE 1 WKC increments
After the master station receives the Ethernet frame, comparing the WKC value of each slave station with the WKC expected value of each slave station respectively; whether the data message is correctly processed by the slave station node of the EtherCAT can be verified.
When the slave station detects that the link is disconnected, the Ethernet frame is looped back, and after the Ethernet frame is looped back is detected by the redundancy control layer, the fault range is judged by combining a work counter WKC:
the slave station at the link disconnection position cannot process the Ethernet frame, so the WKC corresponding to the sub-message is necessarily 0, and the fault range can be obtained according to the slave station address of the sub-message with the WKC of 0. Assuming that N slave stations are provided, after a link failure, the loop 1 has X slave stations, and the loop 2 has Y slave stations, the WKCs corresponding to the slave station sub-messages of the looped Ethernet frames received by the network card 1 at the positions X + 1-N are all 0, the WKCs corresponding to the slave station sub-messages of the looped Ethernet frames received by the network card 2 at the positions 1-N-Y are all 0, and the failure range is at the positions X + 1-N-Y of the slave stations.
Claims (9)
1. A redundancy communication method based on EtherCAT is characterized in that a main station and N slave stations are sequentially connected to form a loop, the main station is provided with two network cards, namely a network card 1 and a network card 2, and the redundancy communication method is used for realizing a bidirectional loop structure and comprises the following steps:
the network card 1 sends the Ethernet frame and receives the Ethernet frame returned from the station through the network card 2, so the loop is normal;
the network card 1 sends the ethernet frame and receives the ethernet frame returned from the station 1, and the network card 2 sends the ethernet frame and receives the ethernet frame returned from the station N, that is, the network card and the station form two loops, and if at least one of the above situations occurs, the loop fails.
2. The EtherCAT-based redundant communication method according to claim 1, wherein the primary station and the secondary station form two loops when a link failure occurs, specifically as follows:
the master station sends Ethernet frames through the network card 1, sequentially loops from the slave station 1 to the slave station i, sequentially from the slave station i to the slave station 1, and then is received by the network card 1, so that a loop I is formed;
after the loop I is formed, the master station sends an Ethernet frame through the network card 2, sequentially loops from the slave station N to the slave station N-j, sequentially from the slave station N-j to the slave station N, and then is received by the network card 2 to form a loop II; wherein i and j represent the serial numbers of the slave stations, and i + j is less than N.
3. The EtherCAT-based redundant communication method according to claim 1, wherein: in the two network cards provided in the master station, each network card can be used for transmitting and receiving data.
4. The EtherCAT-based redundant communication method according to claim 1, characterized in that before the Ethernet frame is sent by the primary station, the network information in the primary station is configured; the network information comprises a network topology structure, an initialization command of each slave station and communication command Ethernet frames needing to be sent periodically.
5. An EtherCAT-based redundant communication method according to claim 1 or 4, characterized in that: the master station configuration tool uses the slave station description file ESI to compile a network information file ENI in an offline mode, and uses the ENI file to configure the master station, wherein the ESI file and the ENI file are in an XML format.
6. The EtherCAT-based redundant communication method according to claim 1, wherein the master station transmits ethernet frames through the network card 1 and receives ethernet frames returned from the slave station through the network card 2, specifically as follows:
the network card 1 of the master station sends Ethernet frames, each slave station extracts or inserts data from the received Ethernet frames, then the processed Ethernet frames are transmitted to the next slave station according to the sequence of the slave station, and finally the slave station N sends back the Ethernet frames processed by each slave station and receives the Ethernet frames by the network card 2 of the master station.
7. The EtherCAT-based redundant communication method according to claim 1, wherein: the destination address of the Ethernet frame sent by the network card 1 is the MAC of the network card 2, and the source address is the MAC of the network card 1; the destination address of the ethernet frame sent by the network card 2 is the MAC of the network card 1, and the source address is the MAC of the network card 2:
after receiving the ethernet frame, the network card 1 determines the destination address of the ethernet frame: if the destination address of the ethernet frame is the MAC of the network card 2, it indicates that the looped ethernet frame is received and the loop is faulty; otherwise, the loop is normal;
after the network card 2 receives the ethernet frame, the destination address of the ethernet frame is determined: if the destination address of the Ethernet frame is the MAC of the network card 1, the looped Ethernet frame is received, and the loop fails; otherwise, the loop is normal.
8. The EtherCAT-based redundant communication method of claim 1 wherein the primary station determines the location of the failed secondary station based on the returned ethernet frames, comprising the steps of:
the master station sets an expected value for each work counter WKC used for each slave station communication sub-message; when the master station sends Ethernet frames through the network card 1 or the network card 2, all WKCs are initially 0; when the Ethernet frame passes through a slave station and data extraction or insertion is realized, the WKC is increased;
after the primary station receives the looped Ethernet frame, comparing the WKC value of each secondary station with the expected value of each secondary station respectively; if the communication is equal, the corresponding slave station is communicated correctly; if the WKC is not equal but not 0, the message processing has problems; and if the WKC is equal to 0, the corresponding slave station fails in communication.
9. A master station based on EtherCAT is characterized by comprising a sending/receiving unit and two network cards, namely a network card 1 and a network card 2, connected with the sending/receiving unit;
the network card 1 is used for sending and receiving Ethernet frames;
the network card 2 is used for sending and receiving Ethernet frames;
a transmitting/receiving unit for performing the steps of:
the network card 1 sends the Ethernet frame and receives the Ethernet frame returned from the station through the network card 2, so the loop is normal;
the network card 1 sends the ethernet frame and receives the ethernet frame returned from the station 1, and the network card 2 sends the ethernet frame and receives the ethernet frame returned from the station N, that is, the network card and the station form two loops, and if at least one of the above situations occurs, the loop fails.
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Cited By (4)
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| CN112685340A (en) * | 2020-12-28 | 2021-04-20 | 深圳市合信自动化技术有限公司 | Method and device for automatically starting EtherCat redundancy function |
| CN114205263A (en) * | 2021-12-08 | 2022-03-18 | 中国信息通信研究院 | Communication method, system and storage medium for Ether CAT network |
| CN114844774A (en) * | 2022-04-24 | 2022-08-02 | 重庆长安汽车股份有限公司 | Redundant communication system, method and storage medium of vehicle-mounted Ethernet ring network |
| CN117092903A (en) * | 2023-10-20 | 2023-11-21 | 浙江禾川科技股份有限公司 | Redundancy control system and method |
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