EtherCAT to CANopen Gateway for Flue Gas Desulfurization

Why Protocol Conversion Matters in FGD Systems

Flue gas desulfurization units are complex. They include pH sensors, flow meters, temperature transmitters, valve actuators, and motor drives. Many of these field devices communicate via CANopen, a robust protocol originally designed for vehicle networks and now widely adopted in machinery and process control. Meanwhile, the plant’s main control system often uses EtherCAT for its high-speed, deterministic data exchange. Without a gateway, integrating these two worlds becomes a challenge of custom wiring and software hacks.

A dedicated EtherCAT to CANopen gateway solves this by acting as a bidirectional translator. It maps process data objects (PDOs) and service data objects (SDOs) from CANopen into EtherCAT’s process data image, and vice versa. This allows a central PLC or DCS to monitor and control CANopen devices as if they were native EtherCAT slaves.

How the Gateway Works: Technical Deep Dive

The core of an EtherCAT to CANopen gateway is a high-performance microcontroller or FPGA that handles two independent communication stacks. On the EtherCAT side, it acts as a slave device, supporting CoE (CANopen over EtherCAT) or a custom object dictionary. On the CANopen side, it functions as a master or slave, depending on the network topology.

The conversion process involves several layers:

• Address mapping: Assigning CANopen node IDs and object dictionary entries to specific EtherCAT process data slots.
• Data format conversion: Handling differences in byte order, data types, and scaling between the two protocols.
• Command translation: Interpreting network management (NMT) commands, heartbeat messages, and emergency objects.

For example, a typical gateway configuration might map a CANopen temperature sensor’s PDO (index 0x1800) to EtherCAT input offset 0x1000. The gateway reads the CANopen message, extracts the temperature value, and places it into the EtherCAT frame at the next cycle. This happens within microseconds, preserving the real-time nature of the control loop.

Hardware Design Considerations for Harsh Environments

FGD installations are tough. The gateway must withstand high humidity, corrosive gases, temperature swings from -20°C to +60°C, and electromagnetic interference from nearby motors and switchgear. Industrial-grade gateways typically feature:

• Galvanic isolation between EtherCAT and CANopen ports (often 1 kV or higher)
• Wide-range DC power input (9–36 V) with reverse polarity protection
• IP20 or higher enclosure, with optional conformal coating for PCBs
• DIN-rail mounting for easy integration into control cabinets

The physical interfaces are typically RJ45 for EtherCAT (100BASE-TX) and a 9-pin D-sub or open-style terminal block for CANopen. Some gateways also include diagnostic LEDs for power, network status, and error indication, which are invaluable during commissioning and troubleshooting.

Real-World Application: Desulfurization Pump Control

Consider a typical wet limestone FGD system. The absorber tower has several recirculation pumps driven by variable frequency drives (VFDs). These VFDs often support CANopen for parameter setting and status monitoring. The plant’s DCS, however, uses EtherCAT for its high-speed backbone. By installing an EtherCAT to CANopen gateway near the pump skid, the DCS can directly read pump speed, current, and fault codes, and send start/stop commands and speed references.

This integration eliminates the need for separate PLCs or hardwired signals. It also enables advanced functions like predictive maintenance: the DCS can log pump running hours and vibration data over EtherCAT, triggering alerts before a failure occurs. The gateway’s configuration software typically allows easy mapping of CANopen objects to EtherCAT variables, often via a simple spreadsheet or web interface.

Configuration and Commissioning Best Practices

Setting up a gateway involves defining the CANopen network (node IDs, baud rate, PDO mappings) and the EtherCAT slave configuration (vendor ID, product code, process data layout). Many gateways come with a configuration tool that generates an EtherCAT slave information (ESI) file, which can be imported into the master’s engineering environment (e.g., TwinCAT, Sysmac Studio).

During commissioning, it’s essential to verify the data mapping using a bus analyzer or the gateway’s built-in web server. Common pitfalls include mismatched data types (e.g., 16-bit vs. 32-bit integers) and incorrect byte ordering (little-endian vs. big-endian). A well-designed gateway will offer flexible conversion options to handle these issues.

The Future of Protocol Gateways in Environmental Control

As emission regulations tighten, FGD systems will become even more automated and data-driven. Gateways that bridge EtherCAT and CANopen will continue to evolve, adding features like OPC UA connectivity, edge computing capabilities, and cloud integration. This will enable remote monitoring of desulfurization performance and compliance reporting without manual intervention.

Moreover, the trend toward modular plant design means that subsystems from different vendors must interoperate seamlessly. A reliable protocol gateway is no longer a niche accessory—it’s a fundamental building block of flexible, future-proof automation architectures.