EtherCAT to CANopen Gateway for Schneider Drive Control
In modern industrial automation, bridging different communication protocols is essential for integrating diverse devices. This article explores a practical solution that connects an EtherCAT master controller to a Schneider Electric variable frequency drive (VFD) via a CANopen network using a dedicated protocol conversion gateway. The approach enables seamless control and monitoring of motor-driven applications such as fans, pumps, and conveyors.
Understanding the Communication Challenge
EtherCAT (Ethernet for Control Automation Technology) is a high-performance industrial Ethernet protocol known for its fast cycle times and precise synchronization. CANopen, on the other hand, is a widely adopted application layer protocol based on CAN bus, commonly found in drives, sensors, and I/O modules. When a system uses an EtherCAT-based PLC or motion controller and needs to operate CANopen devices like Schneider VFDs, a direct connection is not possible due to protocol differences. A gateway that converts EtherCAT to CANopen becomes the critical link, translating data between the two networks in real time.
Key Benefits of Using a Protocol Gateway:
- Preserves existing CANopen devices while upgrading to EtherCAT-based control systems.
- Reduces wiring complexity and cost compared to replacing all drives.
- Enables fast data exchange with cycle times as low as 2 ms for responsive motor control.
- Simplifies integration through standardized configuration tools and EDS files.
System Components and Topology
A typical setup includes an EtherCAT master (such as an Omron PLC or a PC-based controller), a protocol conversion gateway, and one or more Schneider Electric Altivar or similar VFDs equipped with CANopen interfaces. The gateway acts as an EtherCAT slave on one side and a CANopen master on the other. It handles the mapping of process data objects (PDOs) and service data objects (SDOs) between the two networks.
| Component | Role | Typical Example |
|---|---|---|
| EtherCAT Master | Issues control commands and reads status | Omron NJ/NX series PLC |
| Protocol Gateway | Converts EtherCAT frames to CANopen messages | Third-party ECAT-CANopen module |
| CANopen Slave | Executes motor control and provides feedback | Schneider Altivar 320/340 VFD |
Step-by-Step Configuration Guide
The integration process involves configuring both the EtherCAT master and the CANopen gateway. Below is a structured approach based on common engineering practices.
1. EtherCAT Master Setup
Begin by launching the EtherCAT master configuration software. Create a new project and select the appropriate PLC model. Install the ESI (EtherCAT Slave Information) file for the gateway device. This XML file describes the gateway’s capabilities and I/O mapping. Once installed, add the gateway to the EtherCAT network and configure the required I/O sizes. The I/O length should match the data expected from the CANopen side, but it does not need to be identical to the gateway’s internal configuration—the gateway will handle the mapping. After verifying the settings, download the configuration to the PLC.
2. CANopen Gateway Configuration
Open the gateway’s dedicated configuration tool (often called CANopen Configuration Studio or similar). Create a new project and add devices: first, add the master (select ECAT-CANopen type), then add the Schneider VFD as a CANopen slave. If the drive is not listed in the device library, import its EDS (Electronic Data Sheet) file, which is provided by the drive manufacturer. The EDS file contains all necessary communication parameters and default PDO mappings.
3. Parameter Settings
Configure the master parameters: set the CANopen baud rate (commonly 500 kbit/s or 1 Mbit/s), communication cycle period, and the IP address for downloading the configuration. For the slave device, define the PDO parameters. PDOs are used for real-time data exchange—typically, you will map control words, speed setpoints, and status words. Choose the transmission type: cyclic (data sent every cycle) or event-driven (sent on change). Use the “auto-offset” function to automatically assign EtherCAT addresses to the mapped objects, ensuring alignment with the master’s I/O image.
Important: Always double-check the PDO mapping. A mismatch between the gateway’s output data and the drive’s expected input can lead to communication faults or unintended motor behavior.
4. Download and Verification
After confirming all settings, download the configuration to the gateway. Power cycle the devices if necessary. Observe the status LEDs on the gateway: a solid green run light typically indicates successful communication. The EtherCAT master should now be able to control the drive—start/stop commands, frequency reference, and acceleration/deceleration times can be written via the mapped PDOs, while actual speed, current, and fault codes are read back.
Real-World Application Considerations
In practice, a 2 ms communication cycle is sufficient for most variable speed drive applications like HVAC fans or water pumps. However, for high-dynamic applications such as winding or positioning, you may need to optimize the network load and reduce the cycle time further. It is also crucial to tune the drive’s acceleration and deceleration ramps according to the mechanical load to prevent overcurrent trips or mechanical stress. Frequent start/stop operations should be avoided unless the drive is rated for such duty; otherwise, consider using a flying start feature or a DC injection braking method.
| Application | Typical Cycle Time | Key Drive Parameters |
|---|---|---|
| Fan control | 5-10 ms | Accel time 20 s, Decel time 30 s |
| Pump control | 5-10 ms | PID setpoint via CANopen, ramp 15 s |
| Conveyor belt | 2-5 ms | Quick ramp 5 s, torque limit 150% |
Troubleshooting Common Issues
If the gateway does not establish communication, check the following:
- CANopen wiring: Ensure proper termination resistors (120 Ohm) at both ends of the CAN bus. Verify the baud rate matches on all devices.
- Node ID: The drive’s CANopen Node ID must be unique and match the configuration. Avoid conflicts with the gateway’s own ID.
- EDS file accuracy: An incorrect or outdated EDS file can cause mapping errors. Always obtain the latest version from the drive manufacturer.
- EtherCAT I/O size: The I/O size configured in the master must be at least as large as the total PDO data mapped in the gateway. Use the auto-offset feature to prevent overlapping addresses.
Conclusion
Integrating EtherCAT and CANopen networks via a protocol gateway is a cost-effective and reliable method to modernize control systems while retaining existing drive investments. With careful configuration and attention to real-time data mapping, engineers can achieve precise motor control and comprehensive diagnostics. This approach is scalable and can be extended to multiple drives or other CANopen devices, making it a versatile solution for many industrial automation projects.
Pro Tip: When commissioning, use the gateway’s monitoring features to observe live PDO data. This helps verify that control words and setpoints are correctly transmitted before connecting the motor.
