Industrial communication network is one of the most active directions in the field of Internet of Things technology, and it is also the basic technology supporting the development of intelligent manufacturing. With the arrival of a new round of industrial revolution, it has become a hot spot in the field of automation, especially the construction of automated factories, which is inseparable from efficient and fast communication networks. What kinds of industrial communication networks are commonly used in industry now, and what are their characteristics? This article to reveal.

Ethernet/IP

Ethernet/IP is an industrial application layer protocol for industrial automation applications, one year after CI and ODVA announced the EtherNet/IP specification, Rockwell Automation released the first generation of EtherNet/ IP-based products. Mainly focused on Allen-Bradley ControlLogix, ProcessLogix, PLC-5, SLC-500 series controllers. Now, more and more vendors have or are planning to launch their own EtherNet/IP products.

The EtherNet/IP protocol uses TCP/IP to send "explicit" packets, each containing not only application-specific data, but also an interpretation of the data and information on how to process the data. Because the EtherNet/IP protocol makes full use of the advantages of TCP/IP and UDP/IP protocols, it is fused in the same network, making EtherNet/IP not only for ordinary information processing, but also for the transmission of time-sensitive control information.

PROFINET

Developed by Siemens and the Profibus Users Association, PROFINET features communication capabilities, automation and engineering models between products from multiple manufacturers and is optimized for distributed intelligent automation systems. The result of its application can greatly save configuration and debugging costs. The PROFINET system integrates a Profibus-based system, providing protection against existing system investments. It can also be integrated with other fieldbus systems.

PROFINET is an advanced communication system that supports distributed automation. In addition to communication capabilities, PROFINET includes a specification for the concept of distributed automation, which is based on a manufacturer-independent object and connection editor and an XML device description language, and is the only bus that uses existing IT standards without defining its own dedicated industrial application protocol. Its object pattern is based on Microsoft's Component Object Pattern (COM) technology. For the interaction between all distributed objects on the network, Microsoft DCOM protocol and standard TCP and UDP protocol are used, which is a new generation of automation bus standards based on industrial Ethernet technology.

EtherCAT

EtherCAT is a real-time industrial fieldbus communication protocol based on Ethernet-based development architecture. It was introduced into the market in 2003, became an international standard in 2007, and became a national standard in China in 2014. The EtherCAT system architecture typically reduces CPU load by 25% to 30% compared to other bus systems with the same cycle time. EtherCAT has no restrictions on the network topology, and up to 65535 nodes can form a line, bus, tree, star, or any combination of topologies.

EtherCAT provides an efficient synchronization solution with the precise calibration of distributed clocks, in which data exchange is based entirely on pure hardware devices. Because the communication uses a logical ring network structure and a full-duplex fast Ethernet with an actual ring network structure, the "master clock" can simply and precisely determine the operating compensation for each "slave clock" and vice versa. The distributed clock is adjusted based on this value, which means that it can provide a network wide, accurate clock with low signal jitter.

OPC UA

OPC UA is a commonly used communication protocol in the field of industrial automation and is the standard for connecting applications and field control systems. At present, the OPC Foundation is vigorously promoting the development and application of a new generation of technology, OPC UA, which has the potential to solve many of the communication problems related to Industry 4.0 and the Internet of Things industry.

OPC UA has many advantages

1) Has access unity, effectively integrates the existing OPC specifications (DA, A&E, HDA, commands, complex data and object types) into the new OPC UA specification.

2) The OPC UA specification can communicate through any single port. This makes crossing the firewall no longer a roadblock for OPC communication, and to improve transmission performance, OPC UA messages can be encoded in XML text format or binary format, and can be transmitted using a variety of transport protocols, such as TCP and web services over HTTP.

3)OPC UA's standard redundancy model also makes it possible for software applications from different vendors to be simultaneously adopted and compatible with each other.

4) The OPC UA access specification clearly proposes a standard security model, and every OPC UA application must implement the OPC UA security protocol, which improves interoperability while reducing maintenance and additional configuration costs.

5)OPC UA software development is no longer dependent on and limited to any specific operating platform.

Devicenet

Devicenet is an open, low-cost, high-performance communication Network based on CAN(Controller Area Network) technology developed in the mid-1990s, which meets global industry standards and was originally developed and applied by Rockwell Company in the United States.

Many features of Devicenet are inherited from CAN, a well-designed communication bus, which is mainly used for real-time transmission of control data. The main features of DeviceNet are: short frame transmission, the maximum data of each frame is 8 bytes; Non-destructive bit-by-bit arbitration technology; The network can connect up to 64 nodes; The data transmission baud rate is

HART

HART is a transition bus standard proposed by Emerson, the main feature is the 4-20 MA current signal superimposed on the digital signal, but the protocol is not really open, to join his foundation to get the agreement, and to join the foundation to a certain fee. HART technology is mainly monopolized by several large foreign companies, and there are also domestic companies doing it in recent years, but it has not reached the level of foreign companies.

Now there are many smart meters with [HART circle card], support HART communication function. However, from the domestic situation, it has not really used this part of the function to carry out equipment networking monitoring, and at most, it only uses the manual operator to set its parameters. In the long run, the application of HART instrument will decline due to low HART communication rate and difficult networking.

CC-Link

CC-Link is the control and communication link system. In July 2005, CC-Link was approved by the China National Standards Committee as the guiding technical document of China's national standards. Launched by a number of companies led by Mitsubishi, it is an open fieldbus with large data capacity and multiple communication speeds, which can be adapted to different ranges from higher management network to lower sensor layer network.

In general, the entire layer network of CC-Link can be composed of 1 master station and 64 slave stations. The main station in the network is played by PLC, and the secondary station can be remote I/O module, special function module, local station with CPU and PLC, man-machine interface, frequency converter and various measuring instruments, valves and other field instrumentation equipment. And it can realize the connection from CC-Link to AS-I bus. CC-Link has high data transfer speeds up to 10 Mb/s. The underlying communication protocol of CC-Link follows RS 485. Under normal circumstances, CC-Link mainly adopts the way of broadcast-polling for communication, and CC-Link also supports instantaneous communication between the master station and local station and intelligent device station.

POWERLINK

POWERLINK was originally developed as a proprietary technology by its originator B&R and brought to market in 2001.

After that, automation experts decided to open up the technology, the protocol was published publicly in 2002, and the POWERLINK standardization organization EPSG was formed, within this organization, members share know-hows and collaborate on the promotion of the technology, the most important decision of the EPSG was to complete the integration of CANopen. It is also an open standard, allowing it to have real-time protocols.

This version of POWERLINK, also known as "CANopen on Ethernet", was later defined as POWERLINKV2.0, which is what we know today as PowerLink.

The German Bosch company developed the CAN protocol in 1983 for the network communication of the automobile transmission system. Later known as the International Standard ISO11898, CANopen is currently drafted and reviewed by the non-profit organization CiA(CAN in Automaion). Basic CANopen devices and subprotocols are defined in CAN in Automation (CiA) draft standard 301. Medium. Sub-protocols for individual devices are based on the CiA 301 and expanded, such as CiA401 for I/O modules and CiA402 for motion control.

CANopen has become the most common protocol in Europe, and any automation company has a CANopen communication interface, which has also become a low configuration. Low matching does not mean bad, it just means that it is more cost-effective. CANopen defined a complete synchronous control mechanism, making it the mainstream motion control protocol, in addition to running on the CAN bus, but also moved to the Ethernet network (CANopen over Ethernet), forming the famous PowerLink, EtherCat industrial Ethernet protocol.

TSN

Existing IT networks are defined by the IEEE 802 standard, which specifies requirements for different Ethernet layers and functions and ensures interoperability between devices. Today, many industrial vendors, IT vendors, and chip providers are joining IEEE 802 and the recently formed AVnu consortium to update standard Ethernet protocols and develop low-latency data transfer standards for time-sensitive data for IIoT applications.

The new standard, called Time-Sensitive Networking, or TSN, aims to address some of the shortcomings of existing networks. Working with member companies such as Broadcom, Cisco, Intel and NI, the AVnu Alliance will drive an interoperable ecosystem through certification, similar to how the Wi-Fi Alliance certifies products and devices for compatibility with the IEEE 802.11 standard.

The key benefits of TSN include: Bandwidth The dedicated Ethernet protocols commonly used in industrial control today are limited to 100Mb bandwidth and half-duplex communication. TSN will incorporate a variety of standard Ethernet rates (including 1 Gb, 10Gb, and 400 Gb currently in use) and support full-service communication.

Security - TSN protects critical control networks and integrates the most important IT security requirements. Segmentation, performance protection and time composability add multiple layers of protection to the security framework.

Interoperability - By using standard Ethernet components, TSN seamlessly integrates existing brownfield applications with standard IT networks to improve ease of use. Another advantage offered by TSN is the availability of mass-produced commercial silicon chips using a standard Ethernet chip set, which reduces component costs, particularly compared to dedicated Ethernet protocols using smaller volumes and ASIC-based chips.

Latency and synchronization - TSN focuses on the low latency communications required for fast system response and closed-loop control applications. It can achieve deterministic transmission time of about tens of microseconds and time synchronization between nodes of tens of nanoseconds.