The distributed control system has evolved through multiple stages since its inception in the mid-1970s. The core features of each stage are as follows:
Mid-1970s (First Generation)
Representative products included the TDC-2000 from Honeywell, the Spectrum system from Foxboro, the Network-90 system from Bailey, the Teleperm-M system from Siemens, the 900/TX system from Nippon Chuen, and the CENTUM system from Yokogawa. The system mainly consisted of data acquisition devices, field control stations, CRT operation stations, high-speed data communication paths, and monitoring computers. This stage’s products had the advantages of centralized computer control systems, with effective decentralization of control units, and CRT operation stations featuring rich graphics and full system alarm, diagnosis, and management functions. However, the monitoring computer mainly handled many management and information processing functions, using 8-bit or 16-bit microprocessors, with communication being a primary industrial control local network, and the use of a dedicated communication protocol limited system compatibility. Some systems lacked sequential control functions, and the technology had limitations. [6]
Early 1980s and mid-1980s (Second Generation)
Representative products included Honeywell’s TDC-3000, Taylor’s MOD300, Hitachi’s HIACS-3000, Westinghouse’s WDPF, and Yokogawa’s YEWT-TORIA, among others. Some were new designs, while others were upgrades from the first generation. The system consisted of local networks, multi-functional field control stations, enhanced operation stations, main computers, system management stations, and inter-network connectors. The core feature was that it used a local network as the system backbone, with each unit as a network node; network protocols gradually unified with MAP standards or were compatible with MAP, improving data communication capabilities and moving towards standardization; product design became standardized, modular, and structured; control functions were improved, and the user interface was user-friendly; management functions were decentralized, significantly enhancing system reliability, adaptability, and expansion flexibility. [6]
Mid-1980s to late 1980s (Third Generation)
Representative products included MAX’s MAX-1000+PLUS, Siemens’ Teleperm-XP, Bailey’s INFI-90, Westinghouse’s WDPF II, and ABB’s Procontrol-P. The development background was to overcome the inconvenience of proprietary local network interconnection in the second generation products and meet higher requirements for production process automation. The support from computer companies’ technical services also promoted changes in industrial division of labor. Core features included: enhanced information management functions, capable of high-level information management systems; adopting standard communication network protocols to achieve open system communication and solve the problem of interconnection between different devices; applying 32-bit microprocessors and intelligent I/O to improve system performance and control strategies; operation stations introduced technologies such as three-dimensional graphics display, making operation more convenient; hardware used specialized integrated circuits and surface mount technology, improving reliability; supporting personal computers and programmable controllers for access, enhancing system composition flexibility; process control configuration used CAD methods and introduced expert systems to achieve self-tuning, self-diagnosis, and other functions. [6]
Since the 1990s (Fourth Generation)
Marked by Honeywell’s Experion PKS, Emerson’s PlantWeb, Foxboro’s A2, Yokogawa’s R3, and ABB’s IndustrialIT system, the core feature was information (information) and integration (integration). The system architecture is divided into four layers: the enterprise management layer, the factory (workshop) layer, the unit (unit group) monitoring layer, and the field control instrument layer. The main features include: enhanced informatization, possessing comprehensive SCADA functions, equipment management and intelligent maintenance functions, and energy management functions; integration, achieving functional and product integration, using third-party product integration or OEM methods; blurred control object division, supporting mixed control of process, logic, and batch processing, using IEC61131-3 standard configuration; further decentralization, integrating fieldbus technology, installing I/O modules on-site, and changing the communication between the control station and I/O to a field serial bus; system openness, supporting third-party product connections at the enterprise management, factory (workshop), and unit (unit group) monitoring levels; service specialization, manufacturers focusing on industry solution design and implementation, providing specialized solutions and services.