Fieldbuses are the backbone of communication in automation technology and vehicles. They connect sensors, actuators, and controllers, enabling efficient and reliable data transmission between participants. Fieldbuses are used to simplify communication in complex systems and reduce wiring. Various fieldbuses can be distinguished based on several criteria, including topology, transmission medium, application areas, and their distribution.
With the Right Topology Optimally Adapted to the Environment
The topology of a fieldbus describes the structure of the network in which the devices are connected. There are different topologies that vary depending on the fieldbus. The bus topology, where all devices are connected to a common line, is widespread and used by Modbus, CANopen, and DeviceNet, with the latter two based on CAN. A star topology, where each device is directly connected to a central node, is optionally found in PROFIBUS and EtherCAT. The tree topology, a combination of bus and star topology, allows for a flexible structure and is also supported by PROFIBUS and EtherCAT. Some variants of EtherCAT also use a ring topology, where the devices are connected in a closed loop.
The Right Transmission Medium
The transmission media used for data transmission are another distinguishing feature of fieldbuses. Copper cables are widespread and cost-effective, used by PROFIBUS and CAN, for example. Optical fiber offers high transmission speeds and is resistant to interference but is used less frequently, such as optionally in PROFIBUS. Wireless transmission media offer flexibility and easy installation but are susceptible to interference and are used in some variants of PROFIBUS. By using repeaters and bridges, various fieldbuses can also be transmitted wirelessly or optically in certain areas to bridge sections.
Ethernet, known for its high speed and wide distribution, is used by Modbus (over Ethernet), EtherCAT, Powerlink, and many other “Industrial Ethernet” based networks. However, conventional switches and topology components cannot be used in Industrial Ethernet-based systems, as these systems often have high requirements for deterministic communication with low latency.
Application Areas and Distribution
PROFIBUS is particularly widespread in manufacturing and process automation. Its flexibility in topology and high reliability make it especially popular in Europe. Modbus is used in industrial automation and building automation. Its simple implementation and global distribution, especially in North America, make it a popular standard.
CANopen, based on the CAN protocol, is mainly used in mechanical engineering and vehicle technology. Its robustness and real-time capability are particular strengths, while the limited network size is a weakness. DeviceNet, also based on the CAN protocol, is mainly used in manufacturing automation and in North America.
EtherCAT offers a flexible topology and uses Ethernet as the transmission medium. This flexibility and high speed make EtherCAT popular worldwide, especially in Europe and Asia.
Important decision criteria for choosing the right fieldbus include the application area and required data rate, real-time capability and robustness, as well as the costs for components and implementation.
Summary
Fieldbuses are crucial for efficient communication in industrial automation systems and vehicles. The choice of the right fieldbus depends on the specific requirements of the application, such as topology, transmission medium, and regional distribution. Companies should carefully weigh the characteristics of the various fieldbuses to find the best solution for their communication tasks.