Fieldbus technology of the hottest industrial cont

Fieldbus technology of industrial control

1 The site always absorbs their work experience and research and development achievements. The timeliness of data transmission and the real-time response of the system: Generally speaking, the response time of the process control system is required to be 0.01 ~ 0.5s, the response time of the manufacturing automation system is 0.5 ~ 2S, and the response time of the it network is 2 ~ 6S. Therefore, the real-time performance can be ignored in most uses of it

2. Fieldbus emphasizes the integrity and reliability of data transmission in harsh environments: Fieldbus has the ability to transmit data for a long time, continuously, reliably and completely in industrial environments such as dust, high temperature, humidity, vibration, acid (alkali) corrosion, especially electromagnetic and radio interference. It can resist the surge, loss of wave, drop and peak interference of industrial electricity. In flammable or explosive occasions, fieldbus is also required to have intrinsic safety performance

second, standard and non-standard fieldbus

there are more than 30 brands of fieldbus and its systems in the market, which are called real fieldbus and can be used in various fields. In fact, fieldbus in the market should be divided into standard and non-standard

1. Standard fieldbus is a fieldbus product that conforms to the fieldbus protocol model framework of IEC (International Electrotechnical Commission) and has an approximate standard digital signal system. These mainly include IEC61158, FF (Foundation Fieldbus), LonWorks, pro tibus, WorldFIP fieldbus. It is suitable for process control, manufacturing automation and building automation

2. Non standard fieldbus, and other fieldbuses can be regarded as non-standard fieldbus. Most of them have special standards and are suitable for special fields. It will not be close to international standards

III. FCS and DCS

FCS (Fieldbus Control System) based on FF will replace traditional DCS (distributed control system) as the protagonist of the control system. The following is a comparison of several main aspects

1. Digital

1) FCS: fully digital, pure communication makes process control more reliable. In FCS, from sensors, transmitters to regulators, there are always digital signals, which makes more complex and accurate signal processing possible. Ordinary noise is difficult to distort the digital signal in the fieldbus control system. The error checking function of digital communication can detect the error code in transmission

2) DCS: semi digital. In the traditional DCS system, the original digital signals measured by temperature and pressure transmitters must be converted into mA analog signals before being sent to DCs. In the analog system, noise and other signal distortions cannot be detected

2. Interoperability: with an interoperability and fieldbus system, users can choose the best hardware products based on factors such as performance, price, quality and after-sales service, and integrate them into one in a time-saving and labor-saving manner

1) the interoperability of Fieldbus automation equipment is mainly achieved through the standardization of functional modules and their parameters, which has excellent interoperability

2) most of the communication protocols used between DCs and intelligent transmitters are special closed systems exclusively adopted by DCs manufacturers

3. Decentralized

1) FCS: it adopts a completely decentralized system, its control is all decentralized to the site, and the control loop is realized by the field equipment

2) DCS: Mr. Bakker finally emphasizes that one or more control units are used to control multiple circuits. The control part is distributed to some control boards, and each control board has a semi decentralized system of multiple circuits

4. Reliability, maintainability and economy

the fieldbus control system uses digital bus communication lines to replace the one-to-one i/o connection in the traditional DCS. For large-scale i/o systems, it reduces the unreliability caused by the connection and reduces the wiring cost. Compared with the traditional DCS technology, it can save more than 40% of the cable, debugging and maintenance costs

5. Fieldbus has developed into a new FCS control system that can replace DCS. For many people, the coexistence of DCS and F is possible, but DCS is not suitable for integration with fieldbus. If the fieldbus is connected to DCS, most of its advantages cannot be brought into play. Because the function block configuration, status, diagnosis, verification, equipment information and management information from the current equipment distributed in the field equipment cannot be fully mapped to DCs

IV. EIC (electric drive, instrument, computer) integration

in the control system FCS composed of fieldbus, the instrument has developed into an intelligent instrument with comprehensive functions, that is, the function of DCs that used to realize instrument control. In fact, the field controller is the dispersion of PLC functions in the past, which replaces the PLC used for electric drive control. From the above two points, it is not difficult to see that the Fieldbus Control System FCS is a system structure to realize the integration of electrical drive control, instrument control and computer control, and this structure is precisely a more and urgently needed control system structure for the automation of the iron and steel industry

v. progress of Fieldbus

at present, the more popular fieldbuses are FF, LonWorks, PROFIBUS, WorldFIP, can, Hart (transition protocol), etc. These fieldbuses and transition protocols have representative offices or affiliated units in China (mainly Beijing), and most of them have been developed and applied to varying degrees. Among them, FF and Hart are listed in the key projects of the ninth five year plan. The research and development units participating in the fieldbus intelligent instruments are mainly: Xi'an Instrument Group, Shanghai Industrial Automation Instrument Research Institute, Chongqing Industrial Automation Instrument Research Institute, Shanghai Automation Instrument Co., Ltd., Chongqing Chuanyi group, Beijing Huakong technology company, etc., which are specialized in overcoming the technical difficulties of HART protocol and FF protocol communication software and hardware

1. The products developed mainly include:

1) Hart transmitter (including intelligent temperature transmitter, intelligent pressure transmitter, intelligent flow transmitter)

2) Hart intelligent electric actuator

3) Hart bridge

4) field equipment management system software

5) the key research tasks of FF Fieldbus and can bus garden cards, interfaces, etc.

Hart have been basically completed and can be accepted this year. FF can be completed and accepted in the first half of next year

at present, among the more popular fieldbus, FF, PROFIBUS, LonWorks, canhart protocols are introduced more in books and newspapers, among which Hart and LonWorks are developed and applied more in China. The following is a brief introduction to WorldFIP

rldfip: WorldFIP fieldbus has only one set of communication protocol, no matter high-speed or low-speed, and it does not need any bridge or switch. The connection between low-speed and high-speed is only completed by software

worldfip organization believes that its producer/consumer mode and bus arbiter scheduling mode are particularly suitable for fieldbus systems of industrial process control. Many of its advantages are related to this. Both FF and IEC standard draft adopt this communication mode, but the names are different. FF is called publi her/subscriber and link scheduler (LAS), and the actual way is basically the same as WorldFIP. This also explains why WorldFIP supports IEC standards, because it is technically easier for them to move closer to IEC

at present, the application fields of WorldFIP are: power transmission, railway transportation, subway, chemical industry, space technology, automobile manufacturing, etc. In May, 1998, WorldFIP established a technology promotion center in China and focused on two areas that will be vigorously developed in China, namely, energy and railway, which may have rust, corrosion and other phenomena