[Abstract] In the late 1960s, based on the demands of the automotive market and the development of computing technology, Bedford Associates in Bedford, Massachusetts, proposed to the American automotive industry the development of a Modular Digital Controller (MODICON) to replace the relay control panel. Other companies also suggested computer-based solutions. The core idea was to use software programming to replace the hard-wiring method of relay control, and to provide interfaces for input sensors and output actuators widely used in production lines, facilitating large-scale production line process control. PLC Development Review In the late 1960s, based on the demands of the automotive market and the development of computing technology, Bedford Associates in Bedford, Massachusetts, proposed to the American automotive industry the development of a Modular Digital Controller (MODICON) to replace the relay control panel. Other companies also suggested computer-based solutions. The core idea was to use software programming to replace the hard-wiring method of relay control, and to provide interfaces for input sensors and output actuators widely used in production lines, facilitating large-scale production line process control. This is the origin of the term "Programmable Logic Controller." The MODICON 084 was the world's first commercially produced PLC. The 1970s saw the rise of PLCs, initially gaining widespread application in the automotive industry, and subsequently in other sectors. The 1980s marked its maturation, with the full adoption of microelectronics and microprocessor technology; widespread application solidified its unshakeable position in industrial control. During this period, PLC sales consistently grew at double-digit percentage rates, exceeding 35% in the first six years and stabilizing at approximately 12% annually in the following four years. The 1990s ushered in its third development phase. The official promulgation of the international standard IEC 61131 for PLCs propelled new technological advancements: ★ In system architecture, the development evolved from traditional stand-alone systems to multi-CPU and distributed/remote control systems; ★ In programming languages, the diversity of text-based and graphical languages ​​created a programming environment with greater expressive control requirements, text processing capabilities, and communication capabilities. ★ In terms of application scope and level, besides continuing to develop control systems for automated production lines in machining, the focus is on developing PLC-based DCS systems, SCADA systems for monitoring and data acquisition, Flexible Manufacturing Systems (FMS), Safety Interlock Protection (ESD) systems, motion control systems, etc., comprehensively improving the application scope and level of PLCs. Entering the late 1990s, due to strong user demands and pressure for openness, and the vigorous promotion of information technology, if PLCs remained stuck in the original dedicated and closed system concept, they would be doomed. Thus, PLCs entered their fourth stage of development. Its characteristics are: ★ While retaining PLC functions, it adopts an architecture oriented towards fieldbus networks and uses open communication interfaces such as Ethernet and high-speed serial ports. ★ It adopts various relevant international industrial standards and a series of de facto standards. It is worth noting that PLCs and DCSs, originally on different hardware platforms, are trending towards establishing a unified hardware platform, using the same operating system and programming system, and executing different DCS and PLC functions, with the development of computing, communication, and programming technologies. This is the true meaning of EIC (Electrical, Industrial, and Computer Integration). In other words, the form of DCS and PLC will change, but their functions will remain. The key technologies are embedded PC systems and I/O (hardware) supporting fieldbus, as well as programming systems based on IEC 61161-3 and hard real-time operating systems. The Development of PLCs in China In China, around 1974 or 1975, development of programmable sequential controllers using bit-slice microprocessor chips began in Beijing and Shanghai, and some applications were made. However, mass production was never achieved. In 1979, at the beginning of the reform and opening up, under the impetus of the Instrumentation Bureau of the Ministry of Machinery Industry, the 584 PLC was introduced from MODICON in the United States. It was first successfully applied in auxiliary equipment in power plants such as coal conveying, ash removal and slag removal, water treatment systems, and control systems in cement plants, greatly promoting the large-scale application of PLCs in China's industry. Unfortunately, this project, which cost a large amount of foreign exchange, did not achieve healthy follow-up development. Starting in 1985, small PLCs, primarily the MELSEC-F from Mitsubishi Electric Corporation of Japan, entered the Chinese market through non-governmental channels. Within three or four years, small PLCs achieved widespread adoption. After 1990, Siemens, Allen Bradley, and other well-known brands began to enter the Chinese market in large numbers, capturing a significant share of the medium and large PLC market. After 1995, a pattern emerged where large PLCs were dominated by Europe and America, medium PLCs were evenly divided between Europe, America, and Japan, and small PLCs were dominated by Japan, with Siemens steadily gaining ground. This pattern has not changed significantly to this day. From the above brief review, it can be seen that PLCs have formed a huge application market in China, but a PLC manufacturing industry with mass production and continuous development capabilities has not yet been established. It should be noted that: ★ In China, the application level of PLCs is still quite high, and the capabilities of independent design, system integration, and field deployment can be said to be on par with international mainstream levels; ★ The application fields of PLCs are also very wide, covering industries such as metallurgy, power, chemical, petrochemical, machinery, light industry, electronics, electrical engineering, building materials and cement, as well as modern agricultural machinery and other applications. In recent years, the environmental protection industry has also seen widespread application, with a strong development momentum. ★ A large sales, service, application, and system integration team for PLCs exists throughout China, except for Tibet. There is ample reason to say that PLCs have become a suitable technology for industrial control in China. Therefore, the development of PLCs, soft PLCs, and IEC 61131-3 has undeniably become a matter of great concern. Following 1992, various parts of the IEC 61131 international standard for programmable controllers were successively published and implemented in China . The China Industrial Process Measurement and Control Standardization Committee organized the translation and publication work according to the principle of equivalence to the IEC international standard. On December 29, 1995, national standards for PLCs were promulgated as GB/T 15969.1, 15969.2, 15969.3, and 15969.4. This standard only covers Parts 1, 2, 3, and 4 of IEC 61131, omitting Part 5 (Communications), Part 7 (Fuzzy Control Programming Software Tools), and Part 8 (Implementation Guidelines for the IEC 61131-3 Language), all published after 1995. Since its promulgation, it has not had a significant impact. This is because: China lacks a truly substantial PLC manufacturing industry; influential PLC brands in China are not actively promoting it; and there is little organized promotion activity, including from the standard's governing body. It wasn't until after 1998, as IEC 61131-3 gained increasing influence in the international control industry, that influential PLC brands in China began to mention their compliance with or compatibility with IEC 61131-3; several newly launched DCS systems also publicly claimed compliance with or compatibility with IEC 61131-3. Only then did people begin to pay attention to this standard. Specialized articles in relevant professional journals have introduced the background, importance, and main content of this standard. The China Association for Electromechanical Integration Technology (CAMETA) has translated a monograph by two German authors, Karl-Heinz John and Miachael Tiegelkamp, ​​entitled "IEC 61131-3: Programming for Industrial Automation Systems." It is now being distributed internally within the association. Recently, CAMETA collaborated with Mr. Robert Champoud, General Manager of the Far East branch of KW GmbH, a German company renowned for developing programming systems based on IEC 61131-3, to organize and coordinate workshops related to the IEC 61131 project, receiving strong support from Siemens, Phoenix, and Fuji Electric. This has profound significance for promoting its adoption. Soft PLC in China Soft PLC, in essence, is the implementation of PLC functions using software on a PC platform under the Windows operating environment. This concept was introduced to China around 1996. Due to the immaturity of this technology, it has only garnered attention from a small number of academics. While Interllution and Wonderware's HMI and SCADA software have been very successful in my country, their soft logic and soft PLC products, P-31 and InControl, have received little attention. Of course, neither company has intentionally targeted this market. Think&Do and Steeperchase's VLCs entered the Chinese market in 1998 and 1999, with Think&Do putting in considerable effort, yet still not achieving satisfactory results. There have been some successful applications, such as mail sorting systems. I feel this is partly due to their advocacy of flowchart programming languages ​​instead of IEC 61131-3. KW, a German company, established an office in Beijing after 1998, focusing on promoting its IEC 61131-3 compliant programming system MULTIPROG and control program ProConOS. Siemens began promoting its WinAC soft PLC series in China in 2001, and it has already seen some applications. They have demonstrated considerable strategic vision. Inforteam's openPCS from Germany has also begun market development activities in China, and held a technical exchange at the Shanghai Automation Exhibition in June 2002. China's domestically developed DCS systems, such as Shanghai Automation Instrumentation Co., Ltd.'s SUPMAX-800, use IsaGraf from CJ International of France, which conforms to IEC 61131-3, and the powerful real-time operating system VxWorks from the United States. Beijing's Helishi has adopted Inforteam's OpebPCS to develop a new DCS. Analysis of the Development of Control Equipment Worldwide Globally, soft PLC/PC control is developing as an emerging industry. Despite this challenge, PLCs continue to evolve. According to a report by Venture Development Corp. in the United States, in 2000, global sales of DCS systems, PLC systems, and PC control systems reached US$22 billion. Of this, DCS accounted for 40.5%; PLC 46.3%; and PC control 13.2%. The market sales of distributed/remote I/O used in these three control systems also reached US$22 billion, with an annual growth rate of 6.6%. It was estimated to reach US$30 billion by 2005. From an application perspective, DCS still firmly holds sway over process control applications in large-scale continuous process industries (with thousands of I/O points). PLC has entered the batch control market, but still maintains a dominant position in its traditional discrete manufacturing industries. Soft PLC/PC control uses industrial PCs (or embedded PCs) and a robust real-time OS to achieve PLC functions and motion control. To date, PC control has not yet gained widespread acceptance in terms of reliability and safety. According to a report by Venture Development Corp. in the United States, PLC has the following advantages compared to soft PLC/PC control: * A robust maintenance and service system with a large team of experienced maintenance personnel. * Power failures have minimal impact. * For low-end applications, PLC offers a significant performance-to-price ratio advantage. * Unparalleled reliability with minimal downtime. * Ruggedized architecture suitable for industrial environments. * Compared to the rapid development of PCs, PLC products can be supplied long-term with ongoing technical support. The reason why PLCs hold such a stable position in factory automation is as follows: * PLC technology has long-term stability, both hardware and software are easy to use (plug and play), and the price is moderate, making it a suitable technology for industrial control. * It can be said that PLCs can meet 85% to 90% of the performance requirements of today's industrial control. Any shortcomings can be supplemented by other methods. * In recent years, PLCs have also continuously improved their technical content, integrating IT technologies (including Ethernet, the Internet, wireless network technology, fieldbus technology, and using software engineering methods to improve PLC programming languages, developing entirely new programming systems, etc.). * PLCs have also made substantial breakthroughs in openness. A major aspect of attacking PLCs in the past decade was their proprietary nature, but this has greatly improved. PLCs adopt various industrial standards, such as IEC 61131, IEEE 802.3 Ethernet, TCP/IP, UDP/IP, and various de facto industrial standards, such as Windows NT and OPC. * PLC hardware has also made significant progress. Advances in microelectronics technology are all being applied to PLCs, leading to increasingly higher integration of components, which in turn reduces PLC costs and improves reliability. PLC-on-a-chip chips specifically designed for PLC CPUs have been available for many years. High-end PLC products have undergone qualitative changes in architecture and operating systems, resulting in significantly improved performance. Multiple CPU modules can be mounted on a single rack. Web-based PLC series products have also emerged. Regarding the future of PLCs, soft PLCs, and IEC 61131 in China, the traditional PLC manufacturing industry is unlikely to be established and developed domestically in the foreseeable future. However, it is not impossible for soft PLCs to gain significant traction in the near future. Soft PLC I/O can fully utilize mainstream and some viable fieldbus series products. Strong real-time operating systems can adopt Windows CE, NTE, VenturCom RTX, and others; as long as they can achieve time determinism in control, that is, guarantee the execution of control instruction sequences in a highly consistent manner and have predictable results or behaviors. Since joining the WTO, China's process of becoming the "world's factory" is accelerating. We have ample reason to believe that the annual growth rate of PLC and soft PLC sales in China will significantly exceed the world average. Therefore, the promotion and application of PLCs, soft PLCs, and IEC 61131, especially high-level technical support, becomes crucial. With the development of large-scale production in modern industry, the introduction of integrated management and control systems (ERP/MES/PCS) to enhance enterprise market competitiveness has been put on the agenda in China. As the main tool of the basic automation PCS layer—PLC—the response should be to rapidly strengthen PLC networking and communication development capabilities, as well as information processing capabilities. In China, on average, the number of technicians proficient in or knowledgeable about PLC networking and communication, and PLC-computer communication, is still significantly lower than future needs. Therefore, measures to strengthen training are urgently needed. CAMETA should also play a role in this regard. IEC 61131-3 is currently the only international standard for industrial control programming languages. It is widely used in PLCs, DCS, SCADA, and even motion control. The promotion and application of IEC 61131-3 in China will certainly be very successful. The key issue is what measures to take to accelerate the process. In conclusion, PLCs, soft PLC/PC control, IEC 61131-3, and related software (strong real-time operating systems, programming system platforms, etc.) will remain the main players in industrial control for the next decade. This requires us to seize the opportunity, identify the direction, and gain a competitive edge. With the rapid development of fieldbus technology and the widespread adoption of fieldbus products, in addition to strengthening the promotion of IEC 61131-3, we should also promote IEC 61499, a new standard that compensates for the shortcomings of IEC 61131-3 in adapting to distributed systems. After the first round of IEC 61131-3 roadshow presentations, we should use various tools to promote the technology so that industrial control technicians, especially PLC programmers, know that those who do not master the IEC 61131-3 programming language will fall behind and fail to keep up with development. CAMETA should focus on supporting one or two companies developing soft PLC/PC control, highlighting several significant application projects, such as large-scale manufacturing production lines, and summarizing and promoting these successful applications to help industry professionals recognize the superiority of soft PLC/PC control.