Generation of Fieldbus

With the rapid development of information and science and technology, the way of information exchange is changing with each passing day, and is developing towards globalization and digitalization. As the fusion product of information and science and technology development, the automatic control system has also undergone tremendous changes in the past two hundred years since the 19th century. Generally speaking, it can be divided into five generations:

(1) Pneumatic signal control system (PCS)

Pneumatic signal control system is the first generation control system based on 5-13 psi, which appeared in the middle of the 19th century.

(2) Electric analog instrument process control system (ACS)

The electric analog process control system appeared in the 1950s and soon occupied the leading position in the control field. It used 0-10mA or 4-20mA current analog signals to collect and control field level equipment signals. It is the second generation control system. However, due to the low accuracy of analog signals and their susceptibility to interference, it was soon replaced by a new control system.

(3) Centralized digital control system (CCS)

With the development and application of digital computer technology, centralized digital control system (CCS) emerged and occupied a dominant position around the 1970s, known as the third generation control system. The centralized digital control system can conduct timely control, calculation and judgment according to the on-site situation, and can conduct unified scheduling and overall arrangement in the selection of control mode and timing. In addition, because the microcontroller is used as the controller, the transmission of digital signals is carried out inside the controller, which not only overcomes the low accuracy of analog signals in the ACS system, but also improves the anti-interference ability of the system. However, because the system has high requirements for the controller itself, and when the task increases, the efficiency of the controller will decline significantly, it is difficult to ensure that the requirements for sufficient processing capacity and high reliability of the controller are met.

(4) Distributed Control System (DCS)

In the early 1980s, the appearance and application of microprocessors prompted the emergence of the fourth generation of control system - Distributed Control System (DCS). DCS system adopts centralized management and decentralized control, that is, management and control are separated: the upper computer executes centralized monitoring and management, and the lower computer conducts decentralized control on the site, and they are connected by control network to realize information transmission. Different from previous generations of control systems, decentralized control systems reduce the requirements for the processing capacity and reliability of the controller in the system.

(5) Fieldbus Control System (FCS)

In the middle and late 1980s, with the rapid development of microelectronic technology and large-scale and ultra large-scale integrated circuits, in line with the above requirements, an intelligent signal transmission technology - Fieldbus, which takes the microprocessor as the core and uses integrated circuits to realize the collection, transmission, processing, control and other functions of field equipment information, has been developed internationally, and uses this open The interoperable network technology interconnects all controllers and field instruments to form a field bus control system. The appearance of this operating system has caused a revolutionary change in the structure of traditional DCS and other control systems, and has completely decentralized the control functions to the field.