In industrial production equipment, unpredictable problems such as loose network cable connectors and network port malfunctions frequently occur, leading to abnormal bus communication, which in turn affects production and reduces efficiency. Furthermore, troubleshooting which specific node is causing the abnormality is quite tedious and time-consuming.
Therefore, the reliability and maintainability of bus communication are important factors that most users must consider when selecting motion control products. The Leadshine bus motion control card's EtherCAT ring network redundancy function can improve the communication stability and maintainability of the EtherCAT network. Even if any slave station in the EtherCAT network fails or the network cable has a problem, the device can still operate normally.
01. Introduction to Ring Network Redundancy Function
Currently, EtherCAT bus network topologies are typically linear. Leadshine has developed a bus motion control card with ring network redundancy based on a daisy-chain bus topology. The Leadshine bus motion control card master station provides two dedicated EtherCAT network ports. In the daisy-chain topology, ECAT1 is connected to the IN port of slave node 1, then the OUT port of slave node 1 is connected to the IN port of the next slave node, and so on, until the last slave node is connected to the ECAT master station's ECAT2 port, as shown in the diagram. When a single point of failure occurs in the ring structure, the master station can still maintain data transmission with all slave stations, and equipment operation is unaffected, greatly enhancing the reliability and maintainability of the EtherCAT network.
Ring network redundancy advantages
Improve equipment stability
This ensures that the device can still operate normally even when there are problems such as loose RJ45 connectors, node failures, or network port failures, greatly improving the stability of the device.
Improve equipment maintainability
By using ring network redundancy diagnostic methods, the location of nodes where the bus topology is broken can be quickly identified, bus communication can be restored in a timely manner, and downtime for maintenance can be reduced.
Improve production efficiency
With ring network redundancy enabled, a single network cable or port malfunction will not cause the bus communication to be interrupted, ensuring the production efficiency of user equipment in the event of a sudden malfunction.
02. Ring Network Redundancy Configuration Steps
To facilitate user operation, the ring network redundancy function can be configured in the control card debugging software. The following are the operation steps:
Step 1
Open the control card debugging software, right-click "DMC-E5032", select "Master Station Configuration", and click Open. Then check "Ring Network Redundancy Function". After checking, click the "Download and Reset" button.
Note: If "Spindle stops moving after network cable plugging/unplugging is detected" is checked, it will achieve method ② described in section 3 below. If it is not checked, it will achieve method ① and continue moving.
Step Two
After the reset is complete, right-click "EtherCATSuite Master Unit" and select "Scan Device". In the pop-up window "Download default configuration file first?", click "No".
Step 3
Double-click "EtherCATSuite Master Unit" to enter the main station settings interface. Check "Advanced Options". After checking, the "Advanced Options" section will appear in the menu bar.
Step Four
Click "Advanced Options", check "Process Data Mode", select "Use LRD/LWR instead of LRW", then click "Apply changes to all slaves", and finally download the configuration file.
03. Ring network redundancy function effect
The ring network redundancy function can achieve different effects through parameter configuration.
① When a connection is broken or reconnected, the axis continues to move (this is the default effect).
When a node's network port disconnects, the bus communication will report 0x0228. At this time, the entire device can still communicate normally, and moving axes will not stop. When resuming the network port interruption, the bus cycle will report 0x233. At this point, "nmc_clear_errcode" can be called to clear the bus error and restore the bus state.
② When a connection is broken or reconnected, the shaft stops moving.
In this mode, all axes will stop moving when bus communication is disconnected or reconnected. Although an error code is returned for bus communication, bus communication remains normal, and the client can still use the axis-related motion functions normally by calling the function interface.
For example, if the network cable of a slave station (servo, stepper, or I/O module) becomes loose during equipment operation, the equipment can still operate normally. In this case, the EtherCAT bus status will trigger an alarm, and the fault point can be located to restore the loose network cable, reducing abnormal downtime and material loss, and effectively improving the production line efficiency.
04. Ring Network Redundancy Diagnosis Methods
When a bus connection error occurs, the nmc_get_num_connected_slaves_red command can be used to quickly locate the specific node number where the bus error occurred. After restoring the physical connection of the network cable, the nmc_clear_errcode command can be called to clear the bus error and restore the bus state.
For example, the DMC-E5064 bus card connects three slave stations to form a ring network with redundancy.
Disconnect the input network port of the first slave station.
Reinsert into the input network port of the first slave station.
Under normal connection conditions, no disconnections occurred. When the first slave input port was unplugged, all primary connections were disconnected, therefore BrkMainSlaves and CurMainSlaves both showed 0. At this point, the redundant connection took effect, and communication proceeded under the redundant connection. Therefore, the number of slaves connected to the redundant link was 3, i.e., CurRedSlaves was 3. BrkRedSlaves retains the number of the most recent redundant connections, hence it is 3.
When the network cable is plugged back in, the EtherCAT bus switches back to the master connection. At this time, CurRedSlaves is 0, BrkRedSlaves retains the previous redundancy of 3, BrkMainSlaves is 0, and CurMainSlaves is 3. Calling nmc_clear_errcode at this point can clear bus errors.
Unplug the output network port of the second slave station
Reconnect the output network port of the second slave station
Disconnect the output port of the second slave station. At this point, there are only 2 slave stations on the primary connection, so CurMainSlaves is 2. When the connection is currently disconnected, the primary connection has two slave stations, so BrkMainSlaves is 2. The redundant connection currently has one slave station, so CurRedSlaves is 1. When the connection is currently disconnected, the redundant connection has one slave station, so BrkRedSlaves is 1.
After plugging the network cable back into the output port, read the topology again. At this point, BrkMainSlaves and BrkRedSlaves retain the numbers from the last disconnection, still showing 2 and 1. CurMainSlaves and CurRedSlaves correctly display the current connection numbers as 3 and 0. Call the nmc_clear_errcode command to clear bus errors and restore normal bus operation.
Therefore, by reading the data in the above way, it is possible to accurately identify which node is experiencing the communication anomaly, and the method is convenient and quick to use.
Function description:
The above outlines all the steps for implementing ring network redundancy. After configuration, it enhances the reliability and stability of bus communication, providing stronger support for user production. This function has been implemented on our 5000 series bus cards.
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