1. Introduction
Before the 1970s, analog systems were used to transmit and control signals using analog quantities. These systems had poor accuracy and were highly susceptible to interference, resulting in unstable performance and unreliable control. In the late 1970s, with the development of large-scale integrated circuits and microprocessor technology, more advanced control systems emerged. Microprocessors offered greater functionality, smaller size, and higher reliability, enabling more efficient control through appropriate interface circuits. However, these systems were still centralized. With the advancement of process control, automation instrumentation, and computer networking technologies, a new transformation occurred in the control field. This change brought significant improvements in both structure and performance of traditional control systems like distributed control systems (DCS). The foundation of this transformation was the emergence of fieldbus technology.
Fieldbus is a two-way, serial, digital, multi-node communication network that connects field-level intelligent devices and automation control systems. It is also known as the Field Underlying Device Control Network (INFRANET). Since the 1980s, various fieldbus technologies have emerged, prompting changes in traditional analog instrumentation and control systems. This has led to a global wave of technological innovation. The American Instrumentation Association (ISA) began developing fieldbus standards in 1984. In Europe, there are German PROFIBUS and French FIP, leading to the formation of multiple fieldbus standards. Key examples include Foundation Fieldbus (FF), Controller Area Network (CAN), Local Operating Network (LonWorks), Process Field Bus PROFIBUS, and HART Protocol. Despite the diversity, the development of a single open international fieldbus standard is inevitable.
2. Fieldbus Technology and Its Characteristics
Fieldbus is one of the most important developments in automation technology today, often referred to as the LAN of industrial automation. Most field devices now use microprocessors and digital components internally to improve their performance and cost-effectiveness, which necessitates digital communication between them.
Fieldbus is a fully digital, two-way, multi-point communication system that links intelligent field devices with automation systems. It addresses the need for digital communication between field devices such as smart instruments, controllers, and actuators, as well as the transmission of information between these devices and advanced control systems. By integrating digital communication, computer technology, automation, networking, and smart instruments, it breaks through the limitations of traditional point-to-point or digital-analog signal control, creating a fully distributed, digital, intelligent, bidirectional, and interconnected communication and control system.
Fieldbus is a digital, two-way, multi-branch communication network that connects intelligent field devices and automation systems based on smart meters. These meters, scattered across industrial sites, are connected via a digital fieldbus and combined with controllers and monitors in the control room to form a Fieldbus Control System (FCS). Following international standards, fieldbus products from different manufacturers can be integrated into the same FCS, ensuring interchangeability and interoperability. FCS decentralizes the control functions of traditional DCS to on-site smart meters, allowing them to handle data acquisition, processing, control operations, and output. Field instrument data, including collected and diagnostic data, is transmitted to the control room through the fieldbus, enabling monitoring, data storage, and advanced control features. Additionally, FCS can connect to enterprise management networks through gateways, providing managers with real-time data for informed decision-making.
Fieldbus has several key advantages:
2.1 Open Communication Protocol: An open communication protocol allows devices from different manufacturers that follow the same standard to interconnect and exchange information. Users can choose products from various vendors to build an optimal control system.
2.2 Interoperability: Devices from different manufacturers can not only communicate but also be configured uniformly to implement consistent control strategies and "plug and play." Devices with similar performance from different manufacturers can be interchanged.
2.3 Flexible Network Topology: The FCS can form different network topologies depending on complex field conditions, such as tree, star, bus, and hierarchical structures.
2.4 Highly Decentralized Structure: Field devices are intelligent and capable of independent automatic control, fundamentally changing the centralized-decentralized DCS structure. This improves system reliability and simplifies the control architecture.
2.5 Intelligent Field Devices: Unlike traditional DCS, which relies on centralized control stations, the FCS distributes DCS control functions to field equipment. These devices can perform tasks such as data acquisition, PID control, self-diagnosis, and remote monitoring, enhancing system intelligence and efficiency.
2.6 Environmental Adaptability: Designed for industrial environments, fieldbus supports twisted pair, coaxial cable, fiber optics, and wireless transmission. It is highly resistant to interference and can operate under intrinsic safety requirements.
3. Overview of Main Fieldbuses
3.1 Foundation Fieldbus (FF): Developed by the Fieldbus Foundation, FF is an open, non-proprietary protocol supported by major instrument manufacturers worldwide. It follows IEC standards and offers high device interoperability, improved process data, predictive maintenance, and reliable safety.
3.2 PROFIBUS: Proposed by Siemens, PROFIBUS is a widely adopted standard in Germany and Europe. It includes three series: PA for process automation, DP for high-speed data transfer, and FMS for general automation. PROFIBUS uses RS485 and offers high flexibility and reliability.
3.3 LonWorks: Based on the ISO OSI model, LonWorks uses Neuron chips and object-oriented programming to enable communication via network variables or explicit messages.
3.4 CAN (Controller Area Network): Originally developed by Bosch for automotive applications, CAN is known for its high immunity to electromagnetic interference and error detection capabilities. It is widely used in automotive and aerospace industries.
3.5 HART: Introduced by Rosemount, HART is a protocol that enables digital communication over existing analog lines. It is a transitional technology during the shift from analog to digital systems and remains popular in the smart meter market.
4. FCS Control System
Traditional DCS systems require extensive wiring and suffer from signal loss, interference, and high costs. In contrast, the PC-based FCS overcomes these issues by placing all I/O modules in the field, converting signals to digital, and reducing cabling. This results in lower costs, easier installation, and better anti-interference performance.
FCS is open, with standardized software and hardware, making it easy to replace and integrate. It supports IEC1131-3 programming languages and utilizes PC resources for enhanced performance. The system structure includes an industrial PC, fieldbus interface card, I/O modules, control software, and configuration tools. It enables system configuration, real-time monitoring, data sharing, and human-machine interaction, achieving true control concentration, data sharing, and open control requirements.
5. Conclusion
Currently, various fieldbus protocols coexist in the control field. LonWorks and CAN have advantages in building automation, while HART, FF, and PROFIBUS dominate in process automation. HART will remain a key protocol for smart instrumentation, while FF shows strong potential due to industry support. LonWorks' openness has attracted many developers in China. Although the transition to a unified fieldbus standard is ongoing, the gradual decline of traditional DCS is expected. As fieldbus technology continues to evolve, fieldbus control systems will become increasingly widespread and essential in modern industrial automation.
For Oppo Oca,Optical Adhesive Oca Glue,Oppo Reno 10 Pro Oca Sheet Paper,Optically Clear Adhesiv Sheet
Dongguan Jili Electronic Technology Co., Ltd. , https://www.jlglassoca.com