Common industry protocols in robotics
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Robots and automated systems place high demands on industrial communication. Besides sufficient bandwidth, deterministic cycle times, low latency, and precise synchronization are crucial. Depending on the application, the requirements range from high-precision motion control to simple sensor or condition monitoring.
This article provides a concise overview of the industrial protocols commonly used in robotics and places them in a practical context.
Categories of industrial communication protocols
Industrial protocols in robotics can be roughly divided into three levels:
- Real-time Layer 2 Ethernet for motion control and axis synchronization
- Industrial Ethernet based on classic Ethernet stacks for flexible automation
- Field and device level for connecting sensors and actuators
Overview: Common industry protocols
| protocol | core principle | Typical cycle time | synchronization | Typical areas of application |
|---|---|---|---|---|
| EtherCAT | Processing in passing, Layer 2 | < 100 µs | < 100 ns (Distributed Clocks) | High-precision motion control, CNC, robotics |
| PROFINET | Real-time over Ethernet, CC-C | < 1 ms | < 1 µs | Discrete manufacturing, automotive, robot cells |
| EtherNet/IP | CIP over standard Ethernet, UDP for I/O | 1–10 ms | Standard Ethernet | General factory automation |
| Modbus TCP | TCP/IP Client-Server | > 5 ms, non-deterministic | – | Monitoring, SCADA, easy integration |
| IO-Link | Point-to-point, 3-wire technique | Device level | – | Sensor and actuator connection |
EtherCAT
EtherCAT is designed for maximum performance and minimal latency. The protocol operates directly at Layer 2 and does not use the traditional TCP/IP stack. A single Ethernet frame is sent by the master and processed by all slaves in passing, enabling extremely short cycle times.
Distributed clock technology enables synchronization in the nanosecond range, making it ideal for coordinated robot movements and demanding motion control applications.
PROFINET and EtherNet/IP
PROFINET and EtherNet/IP are widely used industrial Ethernet standards that build upon standard Ethernet infrastructures.
PROFINET offers IRT (Isochronous Real-Time, CC-C), a variant for time-critical applications with cycle times of less than one millisecond. It is particularly widespread in Siemens-based automation environments.
EtherNet/IP is based on the Common Industrial Protocol and is primarily established in North America. Real-time communication is implemented via UDP, but requires a suitably designed network with managed switches and quality-of-service mechanisms.
Modbus TCP
Modbus TCP is a simple, widely used protocol for data transmission over Ethernet. It is particularly suitable for monitoring, SCADA applications, and simple connections between robots and controllers.
In robotics, Modbus TCP is frequently used when real-time capability is not a central requirement or as a pragmatic solution for connecting heterogeneous systems.
IO-Link
IO-Link is not a fieldbus, but a standardized point-to-point communication protocol for sensors and actuators. The technology enables bidirectional communication via a classic 3-wire connection and is independent of fieldbuses.
In robot cells, IO-Link is frequently used for grippers, sensors and end-of-arm tools and integrated into higher-level fieldbuses.
Conclusion
Choosing the right industrial protocol depends heavily on the specific application. For high-precision robot movements and motion control, EtherCAT is usually the first choice. PROFINET and EtherNet/IP are well-suited for standardized automation and IT integration. Modbus TCP covers simple communication tasks, while IO-Link efficiently complements the connection to the field level.
In practice, several protocols are often used in parallel to optimally utilize their respective strengths.
