Fieldbus is designed with a lot of advantages for industrial communication,such as
* Simple wiring
* Short project cycle with low cost for installation
* Easy to maintain
* High reliability,good stability,and strong ability of anti-interference
* Fast communication speed
* Safety system meets environment profection requirements.
Therefore many enterprises are paying more and more attention on the importance of fieldbus.
Some beginners are easy to confuse fieldbus with IIOT(Industrial Internet of Things). In fact fieldbus concept is indeed related to IIOT concept. IIOT involves load cell,video device,multimedia and some perceiving and controlling technologies. However Fieldbus,Industrial Ethernet,wireless communication serve as network communication technologies are also involved. In addition,IIOT also involves information processing technologies like data cleaning as well as analysis,data modeling,data storage,etc.,and other security management technologies(encryption and authentication,firewall,intrusion detection). So it can be concluded from above,Fieldbus is only a part of whole technology system in IIOT.
1. What is Fieldbus?
Traditional workshop automation monitoring and information integration system.
Traditional automation monitoring system adopts 4-20mA/24VDC signal which information is limited,it is difficult to exchange information between devices or between systems and outside devices,so the control system is an isolated part in factory,which has seriously restricted to realize information integration and comprehensive automation of enterprises.
Workshop automation monitoring and information integration system based on fieldbus
Automation monitoring system based on fieldbus adopts computer digital communication technology,enable control system and devices to join in factory information network. So information communication range will extend to production site. For example,using Fieldbus technology,a communication cable can inspect the connection of field intelligent devices with information interface,digital communication instead of 4-20mA/24VDC signal can control devices,detect and remote control industrial parameters and so on.
Fieldbus is a digital,bi-directional communication network which has multiple branches and can connect intelligent field devices of automation system. That is to say,fieldbus sets decentralized controlling and communicating devices as network node,to eventually form the controlling network which can deliver information freely and complete whole controlling task.
2. Development of Fieldbus
At present both science technology and information communication way are developing rapidly. Globalization and digitization are oriented. Automatic control system as the outcome from the development of information and science,it also has great changes in the past 200 years since 19th century. In conclusion,there are five generations as below,
First generation: Pneumatic signal control system(PCS)
Second generation: Electronic analog instrument process control system(ACS)
Third generation: Centralized digital control system(CCS)
Four generation: Distributed control system(DCS)
Five generation: Fieldbus control system(FCS)
3. Global Industry Network Market Analysis
Figure 3：HMS Data Analysis
The latest survey by HMS,a Swedish network specialist,shows that in 2016,the number of fieldbus security nodes accounted for 48% of global industrial network market. It can be easily proved fieldbus is still the most widely used network in present industry environment. Many advantages of fieldbus like simplicity,reliability and flexibility etc. have received great preference of users.
4. Fieldbus Market in China
Affected by slowdown investment and declined international demand,fieldbus market witnessed a negative growth in 2016 and it is predicted to be at a low growth rate in the coming years.
5. Eleven Kinds of Fieldbus
(1) FF(Fieldbus Foundation) is based on interconnection of ISO/OSI development system,takes it’s physical layer,data link layer,application layer as the corresponding layer of FF communication model. Furthermore user layer is added on application layer. The user layer primary aims at demand of automation control and measurement,defines the uniform rules for information access,adopts device description language to set common function blocks.
(2) HART(Highway Addressable Remote Transducer) was first introduced by US company Rosement in 1985. It is a kind of protocol for bi-directional communication between smart terminals and control devices. This protocol was supported by over 80 well-known instrument companies. HART Communication Foundation was established in 1993. HART fieldbus provides two simultaneous signal channels:4~20mA analog signal and a digital signal. These two channels can supply an integrated communication solution which is easy to use or configure. Moreover this reliable solution is low cost. Figure 6:
(3) CAN(Controller Area Network) is a serial communication protocol developed by Bosch of Germany in the early 1980s. This protocol can solve real-time data exchange between many control units and test instruments. As an international standard CAN has been supported by Motorala/Intel/Philips/Siemens/NEC and other companies and extensively used in discrete control field.
(4) LONWORKS was developed by US company Echelon in the late 1980s,in 1992 the local operating network was introduced.Initially it was applied to building automation but then used in industrial field network soon. LonWorks fieldbus struture is simple,easy to wiring,expand capacity as well as add new functions. For different function requirements,just need to select different control node and write corresponding procedures,next connect it with control network to meet the expected demand without any addtional change of network structure.
(5) DeviceNet was introduced by US Rockwell Automation Company in 1994. This network achieved network interconnection with low cost as well as good performance. Trough DeviceNet network can be connected with many industrial devices like Connectable Switch,photoelectric sensor,valve bank,motor starter,process sensor,VVVF devices,solid state overload protection,barcode reader,I/O and HMI.It greatly eliminates expensive wiring cost.
(6) INTERBUS is the first kind of fieldbus in the world. It was developed by Phoenix Contact Company in 1984 and displayed in Hannover Fair in 1987. It developed fast and applied widely. INTERBUS has successively become German Standard DIN9258,European Standard EN50254 and International Standard IEC61158. Interbus diversified performance parameters are very close to the virtual needs of automobile production,it is the earliest fieldbus to enter automobile industry,and now it is the most welcome fieldbus in automobile industry as well. Automobile industry is the traditional application area for Interbus.
(7) PROFIBUS served as either German National Standard DIN19245 or European Standard prEN50170,ISO/OSI model is also it’s reference model. Profibus-Dp,Profibus-FMS,Profibus-PA form Profibus series.
DP type is approriate for process automation application to disperse high speed transmission between periphrals. FMS stands for field information specification which is suitable for general automation in textile industry,building automation,programmable controller,low-voltage switch etc. And PA is a type for process automation which complies with Standard IEC1158-2.
(8) WorldFIP is the first fieldbus technology introduced by FIP in France in 1988. In fact WorldFIP provided the basic network structure of fieldbus which made fieldbus system featuring information technology preliminarily.
WorldFIP North American part was merged with ISP into FF,but WorldFIP European part remains independent and headquater is in France. It dominates European market and especially occupies about 60% of France market. WorldFIP features single bus structure to meet the specific need of different applications without additional gateway and bridge,the software can provide solutions for the convergence of high speed and low speed.
(9) CC-Link(Control & Communication Link) is the link system for control and communication.In November of 1996,a number of companies led by Mitsubishi Electric Corporation introduced CC-Link. It developed rapidly. CC-Link has wined a large share in Asia and currently it is growing rapidly in Europe and North America.
In CC-Link system,control and information can be both delivered to the site network at a high speed of 10M bit/s. Excellent performance with low cost make CC-Link to be used widely. It can not only solve the problem of industrial complex wiring but also feature excellent anti-noise and compatibility. CC-Link is a kind of device-oriented network,it also can cover higher level control layer and lower level sense level.
(10) Modbus is a communications protocol developed by Modicon (now a part of Schneider Electric) in 1979. Schneider Electric introduced ModbusTCP in 1996. Modbus is widely used and developed in industrial areas.It is a standard network communication protocol which supports RS232,RS422,RS485 and EtherNet devices etc.
(11) PowerLink was introduced by B & R in 2001. It is an open source fieldbus with good real-time performance. Powerlink can be implemented on different platforms(such as FPGA/ARM,etc.) based on common Ethernet without need of professional chip. Powerlink complies with IEC standard,communication description standard is IEC61784-2,service and protocol description standard is IEC61158-300/IEC61158-400/IEC61158-500/IEC61158-600,and device description standard is ISO15745-1.
6. Fieldbus Comparison
7. Fieldbus Development Trend
(1) In a view of technical point
-Low speed fieldbus areas will continue to develop and improve. At present,fieldbus are mainly low speed products. Whether FF,Profibus or other fieldbus all can implement process control with low speed request. Therefore it is hard to dominate the global market in low speed control areas.
-High speed fieldbus technology is developing with intense competition
High speed fieldbus is primarily used in interconnection of control network,which can connect PC,PLC,and other smarter as well as faster devices,meanwhile achieve the connection of low speed fieldbus bridges.It is necessary to fully implement the decentralized control structure of whole system.The competition in this area is more intense.
(2) In a view of application point
-Network structure tends to simplified
Earlier fieldbus models consisted of seven layers.Now Rockwell proposed three-layer structure automation.Fisher Rosemount proposed two-layer automation.Even one-layer structure was recommended,that can go from Ethernet to the bottom.Now consensus structure is three layer devices and two layer network.
-A lot of proven,developed and versatile technologies are widely used.
For communication protocol of management layer,more and more enterprises adopt the most popular TCP/IP protocol and Ethernet.Generally operating devices are industrial PC or ordinary PC.Control devices adopt standard PLC or industrial control computer. While control network is a variety of fieldbus application fields.
8. Fieldbus Manufacturers
9. Fieldbus Application
The original article is from following link,