EtherCAT to CANopen Gateway for VFD Control Integration
Modern industrial automation often requires communication between devices using different fieldbus protocols. A common challenge is connecting an EtherCAT master controller to CANopen-based variable frequency drives (VFDs). This article explores how a protocol conversion gateway can bridge these two networks, enabling seamless control of drives for applications like fans, pumps, and conveyors.
The solution uses an EtherCAT-CANopen gateway that acts as a slave on the EtherCAT side and a master on the CANopen side. This allows an EtherCAT PLC to command CANopen VFDs without modifying existing hardware. The gateway handles real-time data exchange, mapping process data objects (PDOs) between the two protocols.
System Architecture Overview
The typical setup includes:
- EtherCAT Master: A PLC or industrial PC running an EtherCAT master stack.
- Protocol Gateway: A device with both EtherCAT slave and CANopen master interfaces.
- CANopen Slaves: VFDs or other devices supporting the CANopen protocol (e.g., CiA 402 drive profile).
The gateway translates cyclic I/O data from EtherCAT frames into CANopen PDOs, and vice versa. Configuration is done via dedicated software tools for each side.
Step-by-Step Configuration
1. EtherCAT Master Setup
Begin by creating a new project in the EtherCAT master configuration tool. Import the gateway’s ESI (EtherCAT Slave Information) file to add it to the device catalog. After scanning the network, assign the gateway to the project. Configure the I/O sizes for the process data—these should match the expected PDO mapping on the CANopen side, though exact byte lengths can be adjusted later. Once the configuration is complete, download it to the PLC.
2. Gateway Configuration
Use the gateway’s proprietary configuration software (often called CANopen Configuration Studio or similar). Create a new project and add the EtherCAT-CANopen master device. Then add the CANopen slave devices—if the required EDS (Electronic Data Sheet) file is not in the library, import it from the drive manufacturer’s website.
3. CANopen Network Settings
Set the CANopen baud rate (typically 500 kbit/s or 1 Mbit/s) and the communication cycle time. A 2 ms cycle is common for fast drive control. Configure the IP address for downloading the configuration to the gateway.
4. PDO Mapping
Map the required PDOs for the drive. Standard objects include:
| PDO Type | Typical Objects | Description |
|---|---|---|
| RxPDO (from master to drive) | Controlword (6040h), Target Velocity (6042h) | Commands and setpoints |
| TxPDO (from drive to master) | Statusword (6041h), Actual Velocity (6044h) | Feedback and status |
Set the transmission type: cyclic (synchronous or asynchronous) or event-driven. Use the auto-offset function to assign EtherCAT addresses automatically, ensuring alignment with the master’s I/O image.
5. Download and Verify
Download the configuration to the gateway. After power-up, check the status LEDs: a solid green run light indicates proper communication. The EtherCAT master should now see the gateway in OP (Operational) state, and CANopen slaves should be in NMT Operational mode.
Application Tips for Drive Control
When controlling VFDs via this gateway, consider the following:
- Cycle Time: A 2 ms communication cycle is sufficient for most pump and fan applications. For high-dynamic servo drives, consider faster cycles if supported.
- Acceleration/Deceleration: Optimize ramp times in the drive parameters to avoid overcurrent trips. Use the gateway’s PDO to adjust these remotely if needed.
- Emergency Handling: Map the Emergency (EMCY) object to detect drive faults quickly. The gateway can relay these to the EtherCAT master via diagnostic messages.
- Network Topology: Keep CANopen cable lengths short and use proper termination resistors (120 Ω at both ends). For EtherCAT, standard Ethernet cables and topology rules apply.
Benefits of Protocol Conversion
Using an EtherCAT-CANopen gateway offers several advantages:
- Cost Savings: Retain existing CANopen drives while upgrading the control system to EtherCAT.
- Flexibility: Mix devices from different vendors without compatibility issues.
- Simplified Wiring: EtherCAT’s daisy-chain topology reduces cabling compared to traditional fieldbuses.
- Real-Time Performance: The gateway ensures deterministic data exchange with low jitter.
Troubleshooting Common Issues
If communication fails, check:
- EtherCAT cable connections and slave states (INIT, PRE-OP, SAFE-OP, OP).
- CANopen baud rate and node ID settings match between gateway and drives.
- PDO mapping lengths are consistent on both sides.
- Termination resistors are installed correctly on the CAN bus.
By following these guidelines, engineers can successfully integrate EtherCAT and CANopen networks, unlocking the full potential of their automation systems.
