The hottest fieldbus and factory bottom automation

Fieldbus and factory bottom automation

1, fieldbus technology

1.1 fieldbus technology concept

according to the definition of iec1158 of the International Electrotechnical Commission, fieldbus is "a serial, digital and multipoint communication data bus between field equipment/instruments installed in the production process area and automatic control devices/systems in the control room". In other words, fieldbus is a network system and control system with a single decentralized, digital and intelligent measurement and control equipment as the network node, which is connected with the bus to exchange information with each other and jointly complete the automatic control function. Among them, "production process" should include intermittent production process and continuous production process. Field equipment/instruments refer to sensors, drivers, actuators and other equipment located at the field level. Therefore, fieldbus is a digital network technology for factory bottom automation and information integration. The automation system based on this technology is called FCS (Fieldbus Control System)

1.2 main features of fieldbus technology

(L) digital communication replaces the traditional technology of 4~20ma analog signal. The connection between field layer equipment and controller is one-to-one (one i/o point to one measurement and control point of the equipment) the so-called i/o wiring mode, and the signal transmits 4~20ma (transmitting analog quantity information) or 24VDC (transmitting switching quantity information) signals. Using fieldbus technology, a communication cable can be used to connect the controller with field devices (intelligent, with communication interface), and digital communication is used to complete the communication and control requirements of bottom devices

(2) the intelligent application of field bus technology requires that field devices (sensors, drivers, actuators and other devices) are intelligent (programmable or parameterized) devices with serial communication interfaces. Therefore, fieldbus technology is based on the development of computer large-scale integrated circuits

(3) it integrates the remote control, parameterization and fault diagnosis of field equipment. The fieldbus uses computer digital communication technology to connect intelligent field equipment. Therefore, the controller can obtain a large amount of rich information from field equipment, realize the transmission of equipment status, fault and parameter information, and complete the remote control, parameterization and fault diagnosis of equipment

(4) fieldbus is the extension of computer network communication to the field level. The traditional communication between field layer equipment and controller adopts the way of one-to-one connection to transmit 4~20ma/24vdc signals. This kind of communication technology has a limited amount of information, which makes it difficult to exchange information between equipment and between the system and the outside world, making the automatic control system an "information island" in the factory, which seriously restricts the realization of enterprise information integration and enterprise integrated automation. Fieldbus technology adopts computer digital communication technology, which makes the automatic control system and equipment join the factory information network and become the bottom layer of the enterprise information network, so that the coverage of enterprise information communication has been extended to the production site according to the characteristics of various energy storage technologies

(5) fieldbus technology is the key technology to realize the bottom information integration of the factory. In order to successfully implement CIMS, the information integration and supporting technology at all levels - computer network problem must be solved. Fieldbus is the extension of factory computer network to field level equipment, and it is the technical basis to support the information integration of field level and workshop level with the development of product processing technology and the improvement of product quality requirements

1.3 fieldbus technology development and standards

(1) fieldbus technology and products at home and abroad are developing rapidly. Fieldbus technology, products and systems are developing rapidly internationally. Take fieldbus PROFIBUS as an example. At present, there are more than 1500 products supporting the standard of PROFIBUS, which come from more than 250 manufacturers in the world. More than 2million PROFIBUS devices have been installed and operated worldwide, with an annual growth rate of 25%. The market survey of the fieldbus system FBS (fbsz fieldbus system composed of more than 10 devices) provided by consultant shows that (in the European market, 1996): 427500 sets of FBS have been installed and 146400 new FBS have been added. Fieldbus system accounts for an average of 25% of the market share of the entire automation system. At present, international famous automation, instrument and electrical appliance manufacturers have fieldbus products and systems, such as Rockwell, Siemens, Schneider, Rosemount, Honeywell, Yokogawa, etc

(2) there is no unified international standard for fieldbus. A key problem for the realization of fieldbus technology is to form a fieldbus technical standard that manufacturers jointly abide by in the industry. The world's famous manufacturers of automation products and field equipment, aware that fieldbus technology is the future development direction, have formed enterprise alliances, launched their own bus standards and products, trained users in the market, expanded their influence, and supported the international standards organization to formulate international standards for fieldbus. The competition among major international companies in formulating fieldbus international standards is actually a competition of technical and economic strength, and a competition and division of the future market. Therefore, due to the interests, it is very difficult to reach an agreement in the short term. At present, IEC has not achieved the expected goal

(3) the environmental protection investment per ton of steel that cannot be discharged by enterprises up to the standard needs to be increased by 13%. One fieldbus standard can be used to face a wide variety of automation industries and various application needs. The requirements of automation technology for communication networks are different from those of computers. It is impossible to face a wide variety of automation industries and various application needs with one fieldbus standard. A certain fieldbus standard is applicable in some fields and has high performance price ratio. Beyond these fields, it may not be optimal or even applicable. It is unrealistic to try to use a fieldbus standard to cover all application fields

(4) in the face of many fieldbus standards, we should actively carry out research on fieldbus technology suitable for China's national conditions and oriented to manufacturing automation, and the control modes can be arbitrarily combined and smoothly switched; Automatically obtain the result parameters specified in relevant standards. In the face of various genres of fieldbus and standards in the world, Chinese and foreign experts generally believe that:

· expect IEC to complete the formulation of unified standards as soon as possible according to the expected goals. However, according to the current progress estimation, it is difficult for IEC to achieve the expected goals in recent years

· at present, the proposed scheme proposed by IEC is limited to process automation, which is difficult to meet the requirements of other application fields. It is impossible to become the only standard, and it is likely to form a variety of standard systems to coexist. A variety of communication protocol interfaces are made under the unified standard framework, which can