What Is a Bus Coupler?

Field bus is a kind of industrial data bus that has developed rapidly in recent years. It mainly solves the digital communication among field devices such as intelligent instruments, controllers, actuators and other field control devices and advanced control. Information transfer issues between systems. Due to a series of outstanding advantages such as simple, reliable and economical field bus, it has been highly valued by many standards bodies and computer manufacturers.

1.PROFIBUS

As a fast bus, Profibus is widely used in distributed peripheral components (PROFIBUS-DP). In addition to PROFIBUS-DP and FMS, Beckhoff supports the drive communication standard PROFIBUS MC. Process fieldbus.

EtherCAT

EtherCAT (Ethernet for Control Automation Technology, Ethernet for control and automation technology) is a real-time Ethernet solution for industrial automation with superior performance and easy use.

3.Lightbus

This proven Beckhoff fiber optic bus system is extremely resistant to EMI, easy to install, fast, cyclic and deterministic data flow.

4.Interbus

Interbus is easy to configure, and communication is fast and reliable. The master / slave system's shift register protocol provides efficient cyclic communication.

5.CANopen

By making effective use of the bus bandwidth, CANopen can achieve short system response times even at relatively low data transfer rates. Adhering to the traditional advantages of CAN, such as high data security and multi-master capability.

ControlNet

ControlNet is an open standard fieldbus system. The bus protocol allows cyclic data and acyclic data to be exchanged through the bus at the same time without affecting each other.

7.SERCOS interface

SERCOS was originally developed as a fast fiber-optic bus system for drives. With the Beckhoff SERCOS bus coupler, I / O devices can achieve high-speed data transfers and short cycle times.

8.Ethernet

Ethernet is the mainstream standard in office environments. In Beckhoff Ethernet products, the advantages of Ethernet are also upheld and carried forward, such as high data transmission rate, simple integration with existing networks, and extensive services and interfaces.

9.PROFINET

PROFINET is a standard developed by PNO (PROFIBUS User Organization) for Open Industrial Ethernet: an internationally established IT standard for communication (such as the TCP / IP protocol).

10.USB

USB has become the standard interface for PC technology, featuring high transmission rates and flexible topology (through an integrated hub). In addition to the Beckhoff USB bus coupler, the system can replace fieldbus at short distances.

11.Modbus

Modbus is an open serial communication protocol based on a master / slave structure. It is very easy to implement on all types of serial interfaces and is widely accepted.

12.RS232 / RS485

RS232 and RS485 are classic serial interfaces and have been widely used. Beckhoff RS485 / RS232 I / O modules use a simple serial communication protocol that is easy to implement.

13, CC-Link

CC-Link (Control & Communication Link) is an open bus system for communication between the control level and the fieldbus level. The application is mainly in the Asian region.

14.AS-Interface

The AS interface connects sensors, actuators, and higher-level control layers with a simple and economical wiring method. The AS interface has passed EN 50295 and IEC 62026-2 standards and is internationally standardized.

15, LON

LON (Local Operating Network, Local Operating Network) is a communication system capable of multi-network connection, which is used for distributed applications.

16.EIB

EIB (European Installation Bus) is a bus system for building wiring, which is widely used in Europe.

17.SNMP

Simple Network Management Protocol.

18.QOS

Quality of service, a technology that addresses latency and blocking.

19.CAN

Controller Area Network ^[1]

The generation of fieldbus plays a very important role in the development of industry and has a very important impact on the growth of the national economy. Fieldbus is mainly used in

In April 2003, the third edition of the IEC61158 Ed.3 fieldbus standard officially became an international standard, specifying 10 types of fieldbus.

Type 1 TS61158 fieldbus

Type 2 ControlNet and Ethernet / IP fieldbus

Type 3 Profibus fieldbus

Type 4 P-NET fieldbus

Type 5 FF HSE Fieldbus

Type 6 SwiftNet Fieldbus

Type 7 World FIP Fieldbus

Type 8 Interbus fieldbus

Type 9 FF H1 fieldbus

Type 10 PROFInet fieldbus

Domestic industrial buses EPA, G-link, Symotion and NCUC-BUS

(1) Full digital communication

(2) Open Internet

(3) Interoperability and interoperability

(4) Intelligentization of field equipment

(5) Highly decentralized system structure

(6) Adaptability to the site environment

Different organizations and different people may have different definitions of fieldbus, but generally, it is generally recognized in the following six aspects:

Analyzing from the fieldbus technology itself, it has two obvious development trends:

The first is to seek a unified international fieldbus standard

The second is Industrial Ethernet moving towards industrial control networks

Unified and open

Fieldbus

Due to the dispute over the interests of companies in various countries, although the International Electrotechnical Commission / International Standards Association (IEC / ISA) began to develop fieldbus standards as early as 1984, a unified standard has not yet been completed. Many companies have also launched their own fieldbus technologies, but their openness and

There are about forty fieldbuses in the world, such as FIP in France, ERA in Britain, and ProfiBus by Siemens in Germany.

Fieldbus is gradually popularized in the industrial field. Many devices not only have the functions of traditional instruments, but also have the function of fieldbuses. In DCS, fieldbuses are widely used. The fieldbus needs to pay attention to the following issues in use:

1) Communication distance. Fieldbus communication distance generally has certain requirements. For example, when PROFIBUS / DP is at 12Mbps, standard cables can be used to reach 200m. If 187.5kbps is used, it can reach 1,000m. The communication distance has two meanings. The first is the distance that can be achieved between two nodes without a repeater. Generally speaking, the distance is inversely proportional to the communication rate; the other is the two nodes that are the furthest in the entire network the distance between. Often, the description of this type is not clear in the manufacturer's introduction materials. In actual use, the entire network range must be considered. It takes time for the electromagnetic wave signal to pass through the cable, especially in some high-speed field buses. For large distances, some communication parameters must be modified;

2) Cable selection. The field environment determines the communication speed and communication medium of the fieldbus. Generally speaking, the field bus uses electrical signals to transfer data, and it is unavoidable to receive the influence of the surrounding electromagnetic environment during the transmission process. Most fieldbuses use shielded twisted pair. It must be noted that the shielded twisted pair required for different types of fieldbus may be different. Developers of fieldbuses generally specify a special cable, and the specified rate and transmission distance can only be achieved under the correct use of this cable. Under extremely harsh electromagnetic conditions, optical cables are a reasonable choice, otherwise local interference may affect the work of the entire fieldbus network;

3) Isolation. Generally, the electrical signals of the fieldbus are electrically isolated from the inside of the device. Fieldbus cables are distributed in all corners of the workshop. Once high-voltage inrush occurs, the bus transceivers of all devices in the entire network segment will be damaged. If not isolated, high-voltage signals will continue to damage other circuits inside the device, leading to serious consequences;

4) Shielding. The outer layer of the shielded cable used in the field bus must be well grounded at one point. If high-frequency interference is serious, multi-point capacitor grounding can be used. Multi-point direct grounding is not allowed to avoid ground loop current.

5) Connector. Fieldbus generally does not make strict regulations on the connector, but if it is not handled properly, it will affect the entire system communication. For example, the field bus generally adopts a bus-type daisy chain connection method. When connecting each device, care must be taken to ensure that the insertion and removal of the device is not affected under the existing communication conditions, which has certain requirements for the connector;

6) Terminal matching. The field bus signal has the same reflection phenomenon as all electromagnetic wave signals. The two terminals of each network segment of the bus should use resistance matching. The first effect can absorb radiation, and the second effect is to achieve correctness at both ends of the bus. Level to ensure communication. Therefore, fieldbus technology is the intersection and integration of control, computer, and communication technology. Its emergence and rapid development reflects the requirements of the control field for reducing costs, improving reliability, enhancing maintainability, and improving the intelligence of data collection.

Each kind of bus has its application fields, such as FF, PROFIBUS-PA is suitable for the process control field of petroleum, chemical industry, medicine, metallurgy and other industries; LonWorks, PROFIBUS-FMS, DevieceNet is suitable for buildings, transportation, agriculture and other fields; DeviceNet,

Most fieldbuses have one or several large multinational companies as their backgrounds and set up corresponding international organizations in an effort to expand their influence and gain more market share. For example, PROFIBUS is mainly supported by Siemens, and the PROFIBUS International User Organization has been established. WorldFIP set up the WorldFIP International User Organization with Alstom as the main back office.

1,

Fieldbus technology is control, computer,

In 1984, the United States Inter company proposed a computer distributed control system-BITBUS. It mainly separated the low-speed process-oriented input and output channels from the high-speed computer bus (MULTIBUS) and formed the original concept of fieldbus. . In the mid-1980s, the United States Rosemount Corporation developed an addressable remote sensor (HART) communication protocol. A frequency signal is superimposed on an analog quantity of 4 to 20 mA, and digital signal transmission is realized by using twisted pair wires. HART protocol is the embryonic form of fieldbus. In 1985, sponsored by large companies such as Honeywell and Bailey, World FIP was established and the FIP agreement was formulated. In 1987, led by several well-known companies such as Siemens, Rosemount, Yokogawa, etc., a special committee Interoperating System Protocol (ISP) was also established and the PROFIBUS protocol was formulated. Later, the American Institute of Instrumentation also developed the field bus standard IEC / ISA SP50. Over time, the world has gradually formed two competing fieldbus groups: one is the ISP group headed by Siemens, Rosemount, and Yokogawa; the other is the WorldFIP group led by companies such as Honeywell and Bailey. In 1994, the two groups announced their merger and merged into the Fieldbus Foundation (FF) for short. For the technical development of fieldbus and the development of standards, the Fund Committee has reached the following consensus: jointly formulate and follow the IEC / ISA SP50 protocol standard; agree on the stage of fieldbus technology development.