The Distributed Control System Based Fieldbus

Distributed control system based fieldbus is a new kind of control system, it connects UFCH, UFMH, UOPS, ULFS by databus mode. It integrates computer technology, communication technology and process control technology, adopts multi-layers frame to adjust to demand of high standard productive control and management. It developments and follows the advantages of traditional instrument control system and computer central control system and make up for their disadvantages so that it is applied in oil, chemistry, mineral, electricity, silk, food and water est. with its new frame, modern technology, complex information and unique control mode. It has become mainstream in process control system. Its advantage is simple frame, few cable, saving materials and fees, decrease of maintenance. This paper proposals the research in distributed control system (DCS) and fieldbus control system(FCS) and describes the progresses from DCS to PCS. Then this paper analyzes fieldbus's frame, function, category, compares distributed control system and fieldbus control system, distinguish between RS-485 and CAN in practice application.Under the theory, this paper comes up a DCS based fieldbus and named DCS2000TMRT that is applied in tension control in package factory, this paper recommended its main function, hardware frame, work principles and software design. This system has function dispersion and can deal with parameter checking, calculation, control strategy, information output and process parameters time-control. These functions will auto-run effectually and reliably that make control dispersion. Fieldbus intelligential model layer in this system is made of a few intelligential models in the fields. Intelligential instruments adopt functional model frame and has detection, tension control and speed control etc. The design of the whole system adopt not only RS-485 but also CAN. It has whole digital bilateral communication, multi-parameters deal, self-check etc. In the whole system, each intelligential unit work independently and intercommunicate. The users can freely configure to realize kinds of functions according to their demands. So this system integrates advantages of DCS and fieldbus. This paper takes oneintelligential unit-mobile roll tension control unit as concrete object toanalyze. Its frame, principle, program and character are purposed. During this purpose, difference between RS-485 and CAN in communication are discussed. Then this system's advantages and characters are recommended in practice industrial application.This paper discusses the process of industrial control system thatdeveloped from distributed control system to fieldbus control system and its improvement. In the same time, this paper compares RS-485 and CAN. This paper analyzes a concrete example to represent this system's advantage, such as convenience, common use. Then it interprets distinguish between RS^485 and CAN.