【 Weak current College 】 fieldbus and DCS, FCS of linkages between the three-Power By 【 China power house network 】

FCS is the fieldbus control technology, it is one thing. FCS is the PLC developed; in other industries, FCS is evolved by DCS, PLC and DCS FCS and inextricably links between, and the existence of differences in the nature. FCS is the development by DCS and PLC, DCS and FCS not only possess the characteristics, and PLC a revolutionary step forward. At present, new DCS and PLC, has drawn close to each other. New DCS have a very strong order control functions; and a new type of PLC in disposal no closed-loop control aspects, and both can make up a large network, DCS and PLC, a big crossover. DCS system communication is the key. It can be said that the data highway is DCS distributed control system of the spine. Because of it's mission is to provide all communication networks between the parts, so the data highway's own design determines the overall flexibility and security. Data highway media can be: a twisted pair cable, coaxial or fibre optic cable. Through data highway design parameters, basically can understand a specific DCS system relative strengths and weaknesses. (1) the system can handle the number of I/O information. (2) the system can handle and control the control loop. (3) can adapt to many users and devices (CRT, control stations, etc.). (4) the integrity of transmitted data is thoroughly checked. (5) data highway for the maximum allowed length. (6) data can support the number of branch roads. (7) data highway is supported by other factory production hardware (programmable controller, computer, data recorder, etc.). In order to ensure the integrity of the communication, most of the DCS manufacturers are able to provide redundant data highway. In order to guarantee system security, use a complex communication protocols and error detection technology. The so-called communication protocol is a set of rules to ensure the transmission of data is received and understood it and send data. At present in the DCS system generally use two categoriesof communication means that synchronization and asynchronous, synchronous communication relies on a clock signal to regulate data transmission and reception, asynchronous network uses no clock of the reporting system. · FCS FCS three key points (1) FCS system is the core bus protocol, i.e. bus standards preceding chapters have described, a type of bus, as long as its bus protocol is established, the related key technologies and related equipment are determined. The basic principle of bus protocol, various types of bus are the same, to solve the bidirectional serial transmission of digital distribution as basis. For various reasons, various bus bus protocol there is a big difference. In order for the fieldbus meet interoperability requirements, making it a truly open system, the IEC international standards fieldbus protocol layer in the model of the user, expressly provide user level has the device description. In order to achieve interoperability, each fieldbus devices are used to describe a device description DD. DD can be considered to be one of the drive, it includes all the necessary parameter description and main station the required steps. Because the DD including description of the device to communicate all the information you need, and has nothing to do with the main station, so you can make the field devices achieve true interoperability.
The actual situation as above, the answer is no. Current through the fieldbus international standards including 8 type, and the IEO international standards is just one of the eight types, and other 7 type bus status are equal. Other 7 bus, irrespective of its market share numbers, each bus protocol has a set of software and hardware support. They can form a system, product, and the international standard IEC field bus, is a free software support or hardware support of empty shelves. Therefore, in order to achieve these bus compatibility and interoperability, for the purposes of the present state, is almost impossible. Through this, we can conclude that a mapping: an open fieldbus control system interoperability, a specific type of the field bus, as long as you follow the type fieldbus bus protocol, its product is open and interoperable. In other words, no matter what the manufacturers of the products, nor a family is the fieldbus products, as long as you follow the bus bus protocols, products are open and interoperable, can make up bus network. (2) FCS system is based on the number of digital smart onsite appliance is intelligent field devices FCS system hardware support is the Foundation, the reason is simple, FCS system performing an automatic control device and field device for bi-directional digital communications between the fieldbus signal system. If on-site installations do not follow unified bus protocol, i.e. related communication protocols that do not have a digital communication functions, the so-called bidirectional digital communication just empty words, you cannot call the fieldbus control system. Then, a large field bus is to increase the field-level control function. If the site system is not a multi-function intelligent products, fieldbus control system features that do not exist, the so-called simplified system, which makes it easy to design and facilitate the maintenance advantage is virtual. (3) the nature of FCS system is information processing field of a control system, whether used DCS or fieldbus, system needs to address at least the same amount of information. In fact, the use of fieldbus to from the site for more information. The amount of the fieldbus system is not reduced, or even increasing, and transport information cable is greatly reduced. This requires on the one hand to greatly enhance the ability of cable transmission of information, on the other hand to allow large amounts of information in the scene-place finishes processing, reducing the site and the information between the control room. It can be said that the essence of the fieldbus isinformation processing field. Reduce information from network design and system configuration of an important principle. Reduce information to and from the often leads to improved system response time. Therefore, the network design time should give priority to the mutual information exchange capacity of node, in the same slipRI. Reduce information return and reduce system cable sometimes contradictory. This should save investment principles to make a choice. If you choose a system response time allows, would save cable programmes. If the selected system response time comparison, slightly reducing the point information transmission is sufficient, that would reduce the transmission of information. Now some strip fieldbus field instrument itself has a number of functional blocks, although different products with a function block in performance is slightly different, but a network of branch, there are many functional similarity function block is objective and existent. Choose which field instrument of function block, is the system configuration in order to solve the problem. This principle is: as far as possible reduce the information on the bus. Usually you can select that feature information about the output up to that one of the function block on the gauge.