In recent years, with the continuous advancement of the intelligent manufacturing strategy, Chinese manufacturing enterprises have begun to focus on the transformation and upgrading of underlying industrial automation systems, which has sparked discussions about whether it is necessary to replace fieldbus technology with industrial Ethernet . Currently, the prevailing view is that with the deepening application of smart factories and the gradual integration of IT and OT, connecting the data exchange between upper-level business management systems and lower-level production control systems is an inevitable trend. This inherent driving force is pushing the control and management layers to build a unified network communication standard, making industrial Ethernet an important alternative to fieldbus technology.
The convergence of IT and OT is driving the rapid development of industrial Ethernet.
Industrial Ethernet is a combination of Ethernet technology and general industrial protocols, representing an extension of standard Ethernet applications in the industrial field. In recent years, to meet the demands of high real-time industrial applications, major industrial automation companies and standardization organizations have proposed various technical standards for the real-time performance of Industrial Ethernet. These solutions are based on the IEEE 802.3 standard, extending related standards to improve real-time performance and achieve seamless integration with standard Ethernet.
Currently, the widely used industrial Ethernet standards mainly include the following six types:
(1) MODBUS TCP/IP
Schneider Electric has adopted a development strategy based on collaborative automation solutions using Industrial Ethernet . MODBUS systems can be easily upgraded to MODBUS TCP/IP without requiring users to reinvest in their existing systems.
For MODBUS serial connections, such as RS485, corresponding products are available that make it very easy to update or upgrade from an existing MODBUS system to MODBUS TCP/IP. If other networks are used, appropriate gateways can also be applied to integrate or upgrade them into the Ethernet system.
(2) Ethernet/IP
Ethernet/IP is an industrial application layer protocol for industrial automation applications. It was developed by Rockwell Automation, the company behind the ControlNet fieldbus, to bring Ethernet into the automation field. Built on top of the standard UDP/IP and TCP/IP protocols, it utilizes fixed Ethernet hardware and software to define an application layer protocol for configuring, accessing, and controlling industrial automation equipment. The Ethernet/IP protocol consists of three parts: the IEEE 802.3 physical layer, the data link layer standard protocol, and the Control and Information Protocol (CIP).
(3) Ethernet POWERlink
EthernetPOWERlink is a technology that addresses the real-time data transmission requirements in industrial control and data acquisition applications using standard Ethernet media. EthernetPOWERlink leverages Ethernet's high-speed, open interface and CANopen's well-defined SDO and PDO data definitions for industrial applications. In a sense, POWERlink is CANopen on Ethernet; the physical and data link layers utilize the Ethernet medium, while the application layer retains the original SDO and PDO object dictionary structure.
(4) PROFInet
PROFINET, launched by the PROFIBUS International Organization, is a next-generation automation bus standard based on industrial Ethernet technology. PROFINET encompasses current hot topics in the field of automation, such as real-time Ethernet, motion control, distributed automation, fail-safety, and network security. As a cross-vendor technology, it is fully compatible with industrial Ethernet and existing fieldbus technologies (such as PROFIBUS), protecting existing investments.
(5) SERCOSIII
Sercos (Serial Real-Time Communication System) has been widely used in factory automation applications (suitable for mechanical engineering and construction) for 25 years. Sercos III, the third-generation protocol, was developed in 2003. This efficient and deterministic communication protocol integrates real-time data exchange via the Sercos interface with Ethernet. Sercos III is a product of combining the mature communication mechanism of Sercos with industrial Ethernet; it possesses both the real-time characteristics of Sercos and the features of Ethernet.
(6) EtherCAT
EtherCAT was originally developed by Beckhoff Automation GmbH in Germany. EtherCAT sets a new standard for real-time system performance and topology flexibility, while also meeting or reducing the cost of using fieldbus systems. Other features of EtherCAT include high-precision device synchronization, optional cable redundancy, and a functional safety protocol (SIL3).
Based on the implementation method of the slave devices, industrial Ethernet can be divided into three types:
Category 1:
It employs general-purpose hardware and the standard TCP/IP protocol. Modbus/TCP, PROFInet/CbA, and Ethernet/IP all use this approach. Using the standard TCP/IP protocol and a general-purpose Ethernet controller, all real-time data (such as process data) and non-real-time data (such as parameter configuration data) are transmitted via TCP/IP. Its advantages include low cost, ease of implementation, and full compatibility with standard Ethernet. In specific implementations, some products may achieve better performance by modifying or optimizing the TCP/IP protocol, but real-time performance is always limited by the underlying architecture.
Figure 1 uses general-purpose hardware and standard TCP/IP protocol.
Category Two:
This approach employs general-purpose hardware and defines a real-time data transmission protocol. EthernetPowerlink and PROFInet/RT use this method. Instead of using TCP/IP to transmit real-time data, it defines a dedicated real-time data transmission protocol with a real-time layer to transmit data with high real-time requirements. The TCP/IP protocol stack may still be present for transmitting non-real-time data, but its access to Ethernet is limited by the real-time layer to improve real-time performance. The advantages of this architecture are strong real-time performance and hardware compatibility with general-purpose Ethernet.
Figure 2 uses general-purpose hardware and defines a real-time data transmission protocol.
Category 3:
This method employs dedicated hardware and a custom real-time data transmission protocol. EtherCAT, PROFInet/IRT, and SERCOS-III use this approach. This method, building upon the second type, uses a proprietary Ethernet controller to further optimize performance. Its advantages include strong real-time performance, but its disadvantages include higher cost and the need for proprietary protocol chips, switches, etc.
Figure 3 shows the use of dedicated hardware and a custom real-time data transmission protocol.
The driving force behind Industrial Ethernet replacing fieldbus
With the advancement and implementation of smart factories, enterprises have an urgent need to build unified industrial communication networks. However, due to the numerous and incompatible industrial fieldbus standards, data transmission between controllers of different standards is impossible. Inconsistent network communication protocols have led to widespread automation information silos, posing a significant obstacle to enterprises building interconnected and integrated virtual-physical smart factories. This has become a major driving force for industrial Ethernet to replace fieldbus. The author believes that as industrial Ethernet technology matures, it will partially replace fieldbus and become the mainstream of industrial control network communication.
First, facilitating data integration between business management systems and industrial automation systems has become a crucial step in implementing smart factories. Industrial Ethernet, as a more efficient and versatile network communication standard, provides impetus for building interconnected and better interoperable transparent integrated industrial control networks.
Secondly, fieldbus technology fails to meet the demands of increasingly intelligent industrial applications due to its lack of support for new data types such as voice and images. Industrial Ethernet, based on the TCP/IP protocol, offers unparalleled advantages over fieldbus in terms of bandwidth, data type support, and communication of unstructured data.
Third, it is generally believed that because Ethernet data transmission uses CSMA/CD collision detection, it cannot meet the real-time requirements of industrial data transmission under heavy network load. However, as faster fiber optic cables gradually replace cables, the significant increase in network bandwidth can improve the real-time performance of data transmission. At the same time, industrial manufacturers are also enhancing Ethernet's real-time data transmission capabilities by incorporating real-time data transmission protocols into Ethernet.
Fourth, to ensure the reliable and stable operation of industrial Ethernet in harsh industrial environments such as vibration, dust, and humidity, industrial equipment manufacturers are specifically developing and producing industrial Ethernet switches and other products, which are installed on standard DIN rails and equipped with redundant power supplies. To improve network anti-interference capabilities, the backbone network can use fiber optic transmission, while shielded twisted-pair cables can be used for field device connections. Redundant network technology can also be used for critical network segments.
Summarize
Although Industrial Ethernet (IE) is rapidly developing and has partially replaced fieldbuses in industrial control networks, this author believes it is premature to discuss its complete replacement of fieldbuses. While IE has made progress in real-time performance, reliability, and resilience to harsh environments, it still faces challenges in data acquisition in industrial settings and the interconnection of lower-level sensors and embedded devices, requiring further research and solutions. For the foreseeable future, the industrial control network field will continue to see the coexistence of IE and fieldbuses. However, from an ultimate perspective, the replacement of fieldbuses by IE is inevitable.
