I. Characteristics of Fieldbus
Fieldbus systems break away from the traditional structure of control systems and have the following technical characteristics:
( 1 ) System openness Fieldbus is committed to establishing an open system of unified factory underlying network. Users can use fieldbus to connect products from different manufacturers into open interconnection systems of any size according to their own needs.
( 2 ) Interoperability and interoperability Interoperability refers to the information transmission and communication between interconnected devices and systems; while interoperability means that devices with similar performance from different manufacturers can be interchanged.
( 3 ) The intelligence and functional autonomy of field equipment It distributes the functions of sensing measurement, compensation calculation, engineering quantity processing and control to the field equipment. The basic functions of automatic control can be completed by the field equipment alone, and the operating status of the equipment can be diagnosed at any time.
( 4 ) Highly distributed system structure Fieldbus constitutes a new fully distributed control system architecture, which fundamentally changes the DCS system that combines centralized and distributed control, simplifies the system structure, and improves reliability.
( 5 ) Adaptability to field environment Fieldbus is designed specifically for field environment, supports various communication media, has strong anti-interference ability, can use two-wire system to realize power supply and communication, and can meet intrinsic safety explosion-proof requirements, etc.
II. Advantages of Fieldbus
Due to the simplified structure of fieldbus systems, control systems demonstrate superior performance across the entire process, from design and installation to commissioning, normal production operation, and maintenance. The advantages of fieldbus are as follows:
( 1 ) Saving on hardware quantity and investment Since the intelligent devices distributed on site can directly perform a variety of sensing, measurement, control, alarm and calculation functions, the number of transmitters can be reduced. There is no need for separate regulators, calculation units, etc., nor is there a need for signal conditioning, conversion, isolation and other functional units of DCS system and their complex wiring. An industrial control PC can also be used as an operator station, thus saving a lot of hardware investment and reducing the floor space of the control room.
( 2 ) Reduced Installation Costs: The wiring of a fieldbus system is very simple. Multiple devices can usually be connected to a single twisted pair or cable, thus greatly reducing the amount of cables, terminals, trunking, and cable trays required, as well as the workload of wiring design and connector calibration. When additional field control devices are needed, there is no need to add new cables; they can be connected to existing cables nearby, saving both investment and design and installation work. According to calculations from relevant typical test projects, installation costs can be reduced by more than 60 %.
( 3 ) Save maintenance costs The field control equipment has the ability to self-diagnose and handle simple faults. It sends relevant diagnostic and maintenance information to the control room through digital communication. Users can query the operation, diagnostic and maintenance information of all equipment so as to analyze the cause of the fault early and quickly eliminate it, shortening the maintenance downtime. At the same time, due to the simplified system structure and simple wiring, the maintenance workload is reduced.
( 4 ) Users have a high degree of initiative in system integration. Users can freely choose equipment from different manufacturers to integrate the system. This avoids limiting the range of equipment choices due to the selection of a certain brand of products, and prevents users from being at a loss due to incompatible protocols and interfaces in system integration. This ensures that the initiative in the system integration process is firmly in the hands of the users.
( 5 ) Improved system accuracy and reliability. The intelligent and digital nature of field equipment, compared with analog signals, fundamentally improves the accuracy of measurement and control and reduces transmission errors. The simplified system structure, fewer devices and connections, and enhanced internal functions of field equipment reduce signal round-trip transmission and improve the system's operational reliability.
In addition, due to its standardized equipment and modular functions, it also has the advantages of simple design and easy reconfiguration.
