Real-time Ethernet

In real-time Ethernet technology, there are five main competitors: Ethernet PowerLink, PROFINET, SERCOS III, EtherCAT and Ethernet/IP.

The open source real-time communication technology Ethernet POWERLINK is the latest technology to solve the real-time data transmission in the field of industrial control and data acquisition on the standard Ethernet medium. It follows the ISO model. In a sense, POWERLINK is CANopen on Ethernet. The physical layer and data link layer use the Ethernet medium, while the application layer retains the original structure of the SDO and PDO object dictionary.

PROFINET is introduced by PROFIBUS International (PROFIBUS International, PI), which is a new generation of automation bus standard based on industrial Ethernet technology. According to its real-time ability, it can be divided into three communication methods: ProfiNet TCP/IP, ProfiNet RT (real-time 5-10ms response time), ProfiNet IRT (synchronous real-time response time less than 1ms).

SERCOS III was developed by the German Rexroth company. It is a real-time communication standard that is freely provided for digital drive interfaces. It uses industrial Ethernet as its transmission mechanism. It maintains compatibility with previous versions in terms of interface, message structure and synchronization. , And retains a collection of real-time motion and IO control description parameters.

Ethernet/IP is based on standard UDP/IP and TCP/IP protocols, developed by Rockwell Automation and ODVA (Open DeviceNet Vendor Association), and uses fixed Ethernet hardware and software to access, configure and control equipment Defines an application layer protocol. The traditional Ethernet protocol used by Ethernet/IP means that it can be transparently connected with all standard Ethernet equipment and can continue to develop with the development of the Ethernet technology platform.

EtherCAT was developed by the German Beckhoff company. It adopts a "data train" design method. It transmits and processes at the same time, and sends data packets to each slave node in a logical sequence, and then back to the master station. The master node generally uses a PC, and the LVDS-low voltage differential drive signal transmission mode is adopted between the controller chips of different slave nodes to achieve very high data exchange. It adopts IEEE1588 time synchronization mechanism to achieve precise synchronization of distributed clocks. It can process about 1000 switching values within 30μs, or about 200 16-bit analog quantities within 50μs. Its communication capability can enable the control and position of 100 servo axes. And the status data is updated within 100μs.

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