A Programmable Logic Controller (PLC) is a real-time embedded computer designed for industrial control. Through dedicated control languages, it can implement various logic and process controls. Centered around the PLC, automated control systems can be built for fields such as national defense, manufacturing, rail transportation, power, water conservancy, and municipal engineering. PLC systems have become the "brain" of modern digital industrial systems, comprehensively monitoring various core process and operational data, directly determining and ensuring the safe and healthy operation of national industrial and defense equipment systems.
1. Current Status of PLC Development in China
In the nearly 60 years since its invention, the PLC has achieved a leap from relay wiring logic to stored logic in the field of industrial control, its functions have evolved from weak to strong, it has progressed from logic control to digital control, and its application areas have expanded from small to large, enabling it to leap from simple control of individual devices to complex motion control, process control, and distributed control, among other tasks.
1.1 Development History of Domestic PLCs
The research and application of PLCs in my country began in the 1970s. Based on its development characteristics, it can be divided into four periods: the initial development period, the introduction and application period, the localization development period, and the deep self-reliance period, as shown in Figure 1. Initial Development Period: From the mid-1970s, my country developed its first domestically produced PLC with practical value, applying it to industrial production control. This period mainly focused on the assimilation and secondary development of foreign products. Regarding the introduction of production lines, joint ventures were established to import foreign PLC production lines, such as the Siemens S5 series PLC production line introduced in 1986 and the AB company PLC production line established in 1988. Regarding the introduction of complete sets of equipment, complete sets of equipment integrating imported PLCs were introduced in the steel and water conservancy industries, replacing traditional relays to achieve logic control of the process. For example, over 200 PLCs were introduced in the first phase of the Shanghai Baosteel project to control the conveyor belt, and imported PLCs were introduced to control the feeding, adding, and batching of materials in Shougang's No. 4 blast furnace. Meanwhile, in the 1980s, under the organization of the Ministry of Machinery Industry, research institutes represented by the Beijing Institute of Automation of Machinery Industry began to develop the first generation of domestically produced PLCs, and successively formed a series of products such as MPC-20, MPC-85, and DJK-S-480.
Figure 1. Four Stages of Domestic PLC Development: Introduction and Application Period. In the early 1990s, the level of industrial automation in China was relatively low, and the PLC market was small. PLC R&D required significant investment of funds and manpower, with no short-term returns. Some research institutes shifted towards system integration, using imported PLC products for control system engineering applications. Imported PLC products gradually dominated the domestic market. German Siemens, American AB, and other well-known brands began to enter the Chinese market in large numbers, with imported PLCs accounting for as much as 99% of the market. After 1995, my country's PLC market developed into a pattern where large PLCs were dominated by Europe and the United States, small PLCs by Japan, and medium-sized PLCs were evenly divided between Europe and Japan. The technological development and widespread application of domestically produced PLCs were relatively slow. However, the systematic development of PLCs in China gradually gained attention. In 1991, the PLC Application Branch of the China Electromechanical Integration Application Association was established to promote the development, production, and application of PLC technology and products. In 1993, the National Industrial Process Measurement and Control Standardization Technical Committee (SAC/TC124/SC5) was established, creating my country's standard system for programmable controllers and systems, laying the foundation for the development of PLC technology and industry in my country. This marked the beginning of the domestic production development period.
Entering the 21st century, with the rapid development of domestic manufacturing, the demand for PLCs surged. Some companies, seeing the market opportunity, entered this field, developing and producing domestically made PLC products, achieving large-scale applications in manufacturing, non-standard machinery, and power equipment. However, during this period, domestically produced PLCs were mainly small-scale products, lacking core technologies, and basic components were all imported. Compared with foreign manufacturers, the industry scale was relatively small. For example, in 2013, the domestic PLC market size was 7.8 billion yuan, and Wuxi Xinjie, a domestic company, entered the top ten with a 1.6% market share thanks to its high-performance, cost-effective small PLCs. The period of deep self-reliance began. Influenced by factors such as the Stuxnet virus in Iran, the Prism scandal, the power outage in Ukraine, the US Entity List, and changes in the international situation, during the 13th Five-Year Plan period, the country prioritized critical information infrastructure as a key aspect of cybersecurity. Its control system PLCs were included in the management of key network equipment, initiating a journey of deep localization of critical infrastructure control systems. Domestic enterprises have overcome key core technologies of PLCs and developed independent and safe PLC products based on domestic software and hardware platforms. These products have been promoted and applied in energy fields such as power generation, rail transit, and oil and petrochemicals. For example, the IM30 series PLC developed by the Sixth Research Institute of Electronics in 2020 has been applied in thermal power, wind power, municipal natural gas and other fields, realizing the deep localization of key infrastructure.
1.2 Current Status of the Domestic PLC Market
With the steady advancement of Made in China 2025, the demand for automation systems continues to grow. As the core equipment for discrete control, the domestic PLC market size has been increasing year by year, as shown in Figure 2. From RMB 6.024 billion in 2010 to RMB 12.43 billion in 2020 (excluding distributed I/O products, the PLC market size was RMB 10.85 billion), the average annual growth rate over the 10 years was 7.51%.
Figure 2. Domestic GDP from 2010 to 2020
The PLC market size trend chart, analyzed by PLC model, shows that the market for large PLCs remained relatively stable over the past 10 years, fluctuating around 1.1 billion yuan per year. However, with the trend towards medium-sized PLCs, their performance has continuously improved, leading to their replacement in some application scenarios of large PLCs, resulting in a slight decline in the large PLC market. The medium-sized PLC market has experienced steady growth, increasing from 1.889 billion yuan in 2010 to 3.66 billion yuan in 2020, with an average annual growth rate of 6.84%. Due to rapid growth in demand from OEM sectors such as electronic manufacturing equipment, lithium battery equipment, photovoltaic equipment, semiconductor equipment, and packaging machinery, the small PLC market has seen significant growth in recent years, increasing from 2.733 billion yuan in 2010 to 6.07 billion yuan in 2020, with an average annual growth rate of 8.31%. With the vertical integration of the industrial chain by the Industrial Internet, PLCs are widely used in industries such as automobile manufacturing, electrical engineering, and electronics. As intelligent manufacturing continues to advance, the domestic PLC market is expected to maintain stable growth in the coming years, reaching an estimated market size of 14.46 billion yuan in 2022. Figure 3 shows an analysis of the PLC market size by brand.
Figure 3 shows the market size trend of PLC manufacturers from 2016 to 2020. Siemens' market size and growth rate far exceeded other brands, maintaining its number one ranking for a long time. Japanese brands Omron and Mitsubishi, and American brand Rockwell have consistently ranked second to fourth, with the top four rankings remaining relatively stable. As the market size of small PLCs increases, Delta and Xinje's market rankings have shown an upward trend, with Delta entering the top five in 2020.
Figure 4 shows the domestic PLC market share in 2020. The PLC market size in my country in 2020 was RMB 12.43 billion. The market share structure of various brands is shown in Figure 4(a). Siemens ranked first with a market size of RMB 5.31 billion and a market share of 43%. Other manufacturers were Omron, Mitsubishi, Rockwell, Delta, and Schneider Electric, among others. These manufacturers accounted for approximately 90% of the market share. Only Xinjie, Huichuan, and Hollysys, domestic companies, made it into the top ten. In 2020, the market size of large PLCs was RMB 1.12 billion, accounting for 10%; the market size of medium PLCs was RMB 3.66 billion, accounting for 34%; and the market size of small PLCs was RMB 6.07 billion, accounting for 56%, as shown in Figure 4(b). Large PLCs were mainly dominated by European and American manufacturers. Rockwell, Siemens, and Schneider ranked as the top three in the large PLC market, occupying 76.8% of the market share, as shown in Table 1. Table 1. Market Size of PLC Brands in 2020 (in RMB 100 Million)
In the mid-range PLC market, Siemens leads by a wide margin with a 49.2% market share. Omron and Mitsubishi, with market capitalizations exceeding 200 million yuan, form the second tier, accounting for 29.2% of the market share. Rockwell and Schneider Electric form the third tier, holding 10% of the market share. The small PLC market has lower technological barriers and a large number of suppliers, but the top five manufacturers still hold 74.3% of the market share, presenting a competitive landscape of one large (Siemens) and four smaller (Omron, Mitsubishi, Delta, and Wuxi Xinjie). Overall, domestic PLC manufacturers have achieved a certain level of competitiveness in the small PLC field and have entered the mid-to-large PLC market.
1.3 Current Status of Domestic PLC Products
There are now over 40 domestic PLC manufacturers, with leading companies including Xinje, Inovance, and Hollysys. Through continuous efforts in recent years, domestically produced PLCs have achieved significant results in technology, products, and the market. Xinje's PLCs include the XD/XC small PLC and XL thin card-type series, mainly used in small to medium-sized control scenarios in fields such as solar energy, tunnel engineering, textile machinery, power equipment, coal mining equipment, and central air conditioning. Inovance has developed high-performance H3U, general-purpose H2U-XP, and economical H1U-XP series PLCs, with supporting drive actuators mainly used in elevators, air compressors, robotic arms, and 3C manufacturing. Hollysys has developed LE small PLCs, LK medium to large PLCs, and LKS safety PLCs, mainly used in OEM equipment such as packaging machinery and machine tools, as well as project-based industries such as municipal engineering, tunnels, and rail transit. In addition to the above companies, domestic enterprises have also developed and produced PLC products with distinct characteristics, such as Supcon Technology, Hexin, and Yiwei. However, most of the aforementioned companies develop PLC products based on imported hardware and software, which can lead to self-sufficiency issues during special periods. To address this, companies like the Sixth Research Institute of Electronics have developed domestically produced PLC products based on domestic hardware and software platforms. For example, the Sixth Research Institute has developed the IL40, IM30, and IS20 series of domestically developed and safe PLC products using Phytium CPU processors, which have already been applied in batches in national defense, military, energy, municipal, and other critical infrastructure sectors. Although domestic PLCs have achieved some success, they are generally characterized by being "small, weak, and fragmented." Each manufacturer has a small market size and low market share; products are mainly small PLCs, lacking a complete product portfolio; products are developed based on imported hardware and software or purchased foreign control software, lacking core technologies and advanced control software; their ability to provide comprehensive industry solutions is weak; and they have not formed a technological and market synergy for domestic PLCs, making them less competitive with foreign PLC manufacturers.
1.4 Domestic PLC-related standards
Standardization work in the domestic PLC and related systems field is handled by the Programmable Logic Controllers and Systems Subcommittee (TC124/SC5) of the National Technical Committee on Standardization of Industrial Process Measurement Control and Automation, with business guidance from the China Machinery Industry Federation. The main domestic PLC-related standards are the GB/T15969 series standards. This standard, under the guidance of the Ministry of Machinery Industry of China and managed by TC124/SC5, is equivalent to the international standard IEC61131 and was first published in 1995. As of 2022, the officially released GB/T15969 comprises nine parts. Part 1, General Information, defines the main functional characteristics of the PLC system.
Part 2 covers equipment requirements and testing, specifying the requirements and related tests for the PLC. Part 3 covers programming languages, defining the syntax and semantics of the PLC programming language. Part 4 provides user guidelines, offering basic specifications and rules for information exchange between PLC users and PLC suppliers. Part 5 covers communication, defining the communication between the PLC and other electronic systems. Part 6 covers functional safety, including functional safety PLC safety lifecycle management, functional safety requirement allocation, and development planning. Part 7 covers fuzzy control programming, defining the programming language used for fuzzy control. Part 8 covers the application of the programming language, providing guidelines for the application and implementation of the programming language defined in Part 3. Part 9 specifies single-point digital communication interfaces for small sensors and actuators.
Part 10 is the open XML exchange format for PLCs, specifying an XML-based exchange format for exporting and importing GB/T15969.3 projects. This standard has completed the consultation process and is currently under review. In addition to the GB/T15969 series of standards, relevant standards have been developed for PLC functional evaluation, information security, and engineering integration. GB/T36009 specifies the performance indicators, testing, and evaluation methods for PLCs, providing a basis for PLC performance evaluation. GB/T36011 specifies the sampling inspection methods for environmental adaptability tests of PLCs before they leave the factory, as well as routine test methods for appearance, I/O functions, and communication. GB/T37391 specifies the usage conditions and functional requirements of complete PLC control equipment. Regarding the information security protection capabilities of PLCs, GB/T33008.1 and the currently approved "Information Security Technology: Security Requirements and Test Evaluation Methods for Programmable Logic Controllers (PLCs)" specify PLC network security requirements and test methods. GB/T33008, along with GB/T33009 and other standards, constitute a series of standards for network security in industrial automation and control systems. GB/T41274 describes the intrinsic security goals of PLC systems and the relevant security requirements of each unit module from the perspective of intrinsic security requirements. In terms of PLC industry applications, GB/T40329 specifies the syntax and semantics of dedicated programming modules for CNC equipment PLCs in industrial machinery electrical equipment and systems; GB/T37761 specifies the relevant requirements for PLC control devices in power transformer cooling systems. Regarding national military standards, the first national military standard for PLCs, "General Specifications for Military Programmable Control Systems," began drafting in 2020 and has now been completed and is in the approval stage.
1.5 Domestic PLC-related policies
In recent years, with the gradual expansion of the Entity Lists of Europe and the United States and the frequent occurrence of industrial security incidents, the country has attached great importance to the innovation of information technology applications in the industrial control field, and has successively introduced a series of supporting policies and plans to achieve the self-sufficiency of key core technologies. The country is also extremely concerned about the safety and controllability of PLCs, with self-sufficiency and cybersecurity becoming key terms. The release of corresponding policies has promoted the healthy and orderly development of the domestic PLC industry. Some of these policies are shown in Table 2. Table 2: PLC-Related Policies
In line with policy support, the state attaches great importance to R&D investment in industrial control systems, and has successively established PLC projects in major projects such as the National High-Tech Research and Development Program (863 Program), the National Science and Technology Major Project (Core Electronic Components, High-End General-Purpose Chips and Basic Software Products), and the National Key R&D Program (Network Security Project, Manufacturing Technology and Key Components Project, etc.). These projects aim to enhance capabilities in multiple areas, including large-scale PLC systems, security protection, and controllability, promote breakthroughs in key PLC technologies and their widespread application, and accelerate the self-reliance and strengthening of the PLC industry. Some PLC-related science and technology projects are shown in Table 3. Table 3: PLC-Related Science and Technology Plans and Major Projects
2. Analysis of the gap between domestic and foreign PLCs
With the widespread application of domestically produced PLCs in various fields, they have made certain breakthroughs in application technology. However, shortcomings still exist, and there is still a significant gap compared to foreign PLCs in terms of functionality, performance, ease of use, and reliability. Regarding functionality, high-performance PLCs from mainstream foreign manufacturers typically employ customized dedicated SoCs and real-time running software to improve instruction processing, data storage, data exchange, and control output performance from the underlying platform. In contrast, domestically produced PLCs often borrow general-purpose information system processors and general-purpose embedded systems, mostly adopting a low-performance, low-cost "general-purpose CPU + software" design. Because general-purpose processors are typically designed for information computers and conventional embedded systems, the systems are cumbersome, with many useless functions in the basic hardware and software. Furthermore, they lack underlying chip and software support for real-time performance and advanced control algorithms, resulting in significant difficulties in developing and upgrading dedicated PLC functions, limited optimization potential, low control efficiency, and overall weak performance. In terms of logic programming software, foreign PLC logic programming software typically integrates monitoring and drive execution functions, achieving integrated engineering design capabilities, strong ease of use, and high engineering development efficiency.
Most domestically produced PLC logic programming software adopts the kernels of foreign general-purpose products such as CoDeSys, KW-Software, or OpenPCS. These software programs only consider the programming and development requirements of the PLC itself, failing to achieve integrated development with other control systems. Integration with third-party systems is labor-intensive, complex, and lacks ease of use, resulting in low engineering development efficiency. For example, Siemens' TIAPortal logic programming software integrates PLC programming software Step7, PLC simulation software PLCSIM, and monitoring software WinCC, enabling efficient configuration of control and monitoring points. Control variables are available globally across the entire project. In contrast, domestically produced PLCs require frequent importing and exporting of control and monitoring variable points in the logic programming software to achieve interaction and communication with other systems, leading to lower engineering efficiency. Regarding communication protocols, most PLC products from major foreign manufacturers use independently developed communication protocols. With a well-established independent ecosystem, they achieve compatibility and interconnection between the upper-level monitoring layer and field instruments and actuators through a unified network. Foreign manufacturers only release the conventional protocol portions as IEC international standards or open-source code, without disclosing protocols and code for complex applications. Domestic PLC manufacturers lack the capability to independently develop communication network protocols, and most of them directly use IEC standards or industrial fieldbuses based on open-source code.
Domestic PLCs are constrained by established standards, making it difficult to modify and optimize protocol specifications. Custom development is challenging, and connecting to actuators requires additional conversion interfaces, reducing system response time. In complex control applications, insufficient functionality or performance is frequently observed, significantly limiting product scalability and adaptability. In terms of product portfolio, major international manufacturers offer not only PLCs but also a complete range of upstream and downstream automation software and hardware products, enabling the rapid creation of integrated solutions covering core products such as sensing, execution, control, and monitoring. Domestic PLC manufacturers typically only offer PLCs, resulting in a limited product line and a lack of supporting upstream and downstream automation products. This incomplete product portfolio makes it difficult to provide system-level integrated solutions, hindering the formation of a cohesive product system in terms of both product technology and market competitiveness. Domestic integrated solutions generally utilize products from different manufacturers, leading to differences in product interfaces, functional definitions, and quality standards. Product compatibility is inferior to that of foreign products from the same manufacturer, preventing system-level optimization of overall performance, control efficiency, and reliability, while increasing system design complexity and debugging difficulty. Furthermore, control system engineers often struggle to achieve one-stop procurement when selecting domestic products. In terms of standardization, foreign PLC manufacturers have accumulated and developed over decades, forming a large-scale industry. With their market advantage, they have led the development of a comprehensive standard system covering automation systems, including international and industry standards for control technology, information security, and functional safety, thus gaining control of the industry. While China has developed some PLC technical standards, these existing standards are largely equivalent to foreign standards, lacking top-level planning and a complete standard system. Furthermore, they are constrained by established foreign technical standards, resulting in limited independent innovation in domestic PLCs. This hinders their ability to lead technological development through standards, leading to a lack of competitiveness in the market and weak industry influence.
3. Development Strategy of "Chinese-style" PLCs
Currently, PLCs can be divided into three major schools based on region: European, American, and Japanese, each with different characteristics in product positioning, functional performance, logic programming, and market layout. European PLCs are represented by Siemens and Schneider Electric, American PLCs by Rockwell and General Electric, and Japanese PLCs by Mitsubishi and Omron. Addressing the gap between domestic and international PLC development, and considering the current state of domestic PLC development, this paper proposes a development strategy for "Chinese-style" PLCs. Corresponding to the three major PLC schools, "Chinese-style" PLCs are domestically developed PLC products based on the characteristics of the domestic market and application scenarios, utilizing domestically developed software and hardware, possessing native safety capabilities, conforming to the usage habits of domestic engineers, and meeting the diverse industrial control application needs in China.
3.1 General Situation
The R&D backgrounds, application needs, and market positioning of European, American, and Japanese PLC products differ significantly, resulting in distinct product characteristics and market distributions. European and American PLCs are innovation-driven, powerful, and renowned for their medium to large-sized PLCs, boasting comprehensive product lines. European PLCs offer strong functionality, rigorous programming methods, but are slightly less user-friendly. American PLCs emphasize practicality, featuring numerous function blocks and relatively simple programming methods. European and American PLCs are primarily used in major equipment and critical infrastructure sectors, with a high market share in project-based applications. Japanese PLCs are market-driven, known for their small PLCs, high product integration, and programming methods similar to traditional electrical control, but with generally limited functionality. Japanese PLCs are mainly used in small to medium-sized electromechanical automation equipment, with a high OEM market share. "Chinese" PLCs should focus on applications in defense and critical infrastructure sectors, benchmarking against European PLCs while incorporating the cost-effectiveness and high integration of Japanese PLCs. By leveraging the driving force of major equipment and key sectors, a domestic PLC ecosystem can be established, gradually expanding to other fields.
3.2 Market Situation
From a market distribution perspective, in 2020, European PLCs accounted for approximately 47.4% of the overall market, making them the largest segment. American PLCs accounted for about 7%, and Japanese PLCs for about 21.6%. European and American PLCs held the vast majority of the market share in the medium and large-sized PLC segment, while Japanese PLCs maintained a high market share in the small-sized PLC market. American Rockwell, European Siemens, and Schneider Electric accounted for 76.8% of the large-sized PLC market. European Siemens dominated the medium-sized PLC market, maintaining a relatively stable market position with a market share exceeding 50%. Japanese Omron, Mitsubishi, and German Siemens held 56% of the small-sized PLC market. Considering the deep localization of critical infrastructure, "Chinese-made" PLCs should initially target the medium and large-sized PLC market. In terms of product pricing, European and American PLCs, primarily focusing on medium and large-sized models, offer more powerful functions and higher added value, thus commanding higher prices.
Especially American brands like AB (All-Star) and Japanese brands, primarily focusing on small PLCs, are positioned as economical products with high cost-performance and relatively lower prices. Considering the current ecosystem characteristics, product specifications, and application scenarios of basic software and hardware in China, "Chinese-made" PLCs are positioned at a mid-range price, lower than European and American brands and slightly higher than Japanese PLCs. In terms of industry distribution, European and American PLCs mainly target the project-based market, where PLC products are used in integrated control system projects, designed and implemented alongside the overall automation system. Japanese PLCs primarily target the OEM market, assembling PLCs into equipment and selling them in bulk along with the equipment. European PLCs boast a complete product line, reliable quality, a mature channel network, and excellent solution capabilities, finding applications in almost all user industries. They possess strong competitiveness and a high market share in major sectors such as power, metallurgy, rail transportation, and automotive manufacturing. For example, in the hydropower sector, Schneider Electric of France almost monopolizes the market.
American PLCs, with their powerful functions and support from leading system integrators across various industries, enjoy a high market share in municipal, oil and gas, metallurgy, power, pharmaceutical, and food industries. Japanese PLCs, with their outstanding cost-effectiveness, constantly evolving product lines, and high degree of functional integration, are widely used in almost all OEM industries that utilize small PLC products, including food machinery, packaging machinery, textile machinery, machine tools, electronic manufacturing equipment, and HVAC systems. "Chinese" PLCs primarily target applications in sectors vital to national welfare and people's livelihoods, including military equipment, defense manufacturing, and critical infrastructure sectors such as power, water conservancy, oil and petrochemicals, metallurgy, and municipal engineering.
3.3 Product Characteristics
European and American PLC products emphasize process control and communication control, while Japanese PLCs focus more on discrete control and motion control. Chinese PLCs, particularly large and medium-sized models, prioritize process and discrete control, while smaller models focus on motion control. From a process control perspective, European PLCs support complex floating-point operations, have advantages in analog signal accuracy, and offer simple control logic programming. They can quickly and easily implement closed-loop control algorithms such as PID, giving them a clear advantage in process control. Japanese PLCs primarily rely on integer calculations, making analog signal programming complex. Implementing complex controls requires dedicated control modules, increasing costs. From a motion control perspective, Japanese PLCs typically have dedicated positioning instructions for servo control and stepping motion, making it easier to implement complex motion control, such as robotic arm control. European and American PLCs lack dedicated motion control instructions, requiring complex programming and resulting in lower control accuracy. From a communication perspective, European and American PLCs often use open industrial communication protocols or provide communication protocol chips, facilitating integration with third-party devices. Japanese PLCs typically have relatively closed network protocols, supporting only their own products and making it difficult to connect to third-party devices.
3.4 Control Logic Programming
European and American PLC programming is closer to computer programming principles. Treating the PLC as a specialized industrial computer, PLC programming borrows the general and simple methods of computer programming and the straightforward data processing methods, resulting in a more concise and intuitive programming approach. European and American PLCs primarily use structured programming, with a more complete hierarchy and structure, featuring abundant function blocks, program blocks, and organization blocks for easy calling and reuse, high readability, and easy fault location and debugging. Some European and American PLCs also support high-level language programming, such as C, which offers a significant advantage when writing large-scale control programs. However, PLC instructions are relatively abstract, requiring a certain learning curve and engineers need some basic computer knowledge. Japanese PLCs, on the other hand, have a more graphical programming approach, and their data processing largely departs from the basic storage area concepts and formats of computer data processing, making programming intuitive and easy to learn.
Japanese PLCs typically employ a top-down, single vertical structure, including a main program and subroutines. This lack of hierarchy and structure means many programs need to be grouped together. PLC programming efficiency is relatively low, and result interpretation is cumbersome. Therefore, Japanese PLCs are suitable for small to medium-sized control systems, but programming and debugging in large systems is tedious and complex, making efficient and rapid programming and manufacturing difficult. "Chinese" PLCs should primarily refer to the characteristics of European and American PLC programming software, while also drawing on the graphical programming concepts of Japanese PLCs, to achieve both the ability to meet the requirements of complex control scenarios and intuitive programming and configuration. Considering the characteristics of the domestic PLC market and user habits, in terms of product range, product features, and product applications, "Chinese-made" PLCs are developed based on domestically produced software and hardware, benchmarking against European PLC products. First, in terms of product range, they have a complete range of large, medium, and small PLC products, with a focus on medium and large high-end PLCs. Second, in terms of product features, they have high-end functions such as hot standby redundancy and advanced control algorithms, as well as advanced performance such as nanosecond-level instruction processing speed and microsecond-level synchronization accuracy, meeting the needs of complex application scenarios. Third, in terms of product applications, they will initially play a leading role in key areas related to national economy and people's livelihood, such as national defense and military industry and critical infrastructure, and gradually promote their application to other fields after forming a certain ecosystem.
4. Conclusion
This paper reviews the four stages of PLC development in China, introducing the current status of domestic PLC development from the perspectives of market conditions, product status, standards, and relevant national policies and plans. Then, it analyzes the gap between domestically produced and imported PLC products, and, based on the current domestic situation, proposes a development strategy for "Chinese-style" PLCs, benchmarking against European, American, and Japanese PLCs.
