1. Core Views
1.1 PLC Communication: The Key Hub of Industrial Automation
PLC communication plays a central role in modern industrial automation. It is like a neural network in an industrial automation system, connecting different devices to achieve information transmission and interaction, so that various devices can work together efficiently. For example, in an industrial production line, different PLC devices use specific communication methods and protocols to achieve precise control and real-time monitoring of the production process. PLC communication enables devices to quickly respond to each other's state changes, improving production efficiency and product quality.
1.2 Multi-scenario applications promote industrial upgrading
PLC communication has a wide range of applications in many fields, providing a strong impetus for the intelligent development of the industry. In the steel, petroleum, chemical and other industries, PLC communication realizes the closed-loop control of analog quantities such as temperature, pressure, and flow, ensuring the stability and safety of the production process. In the field of transportation, PLC communication can be used to control traffic lights, subway trains, etc. to improve traffic efficiency. In building automation, PLC communication can realize intelligent control of equipment such as air conditioners and lighting, and reduce energy consumption. According to statistics, PLC has been widely used in various industries such as steel, petroleum, chemical, electric power, and building materials in domestic and foreign industrial fields. Its use covers the logic control of switch quantity, analog quantity control, motion control, process control, data processing, communication and networking.
1.3 Technological innovation leads future trends
PLC communication technology continues to innovate, leading the future development trend of industrial automation. In the future, PLC communication will have higher intelligence and autonomous learning capabilities, and will be able to self-optimize control strategies and predict equipment failures. At the same time, with the development of high-speed communication protocols such as 5G and Wi-Fi 6, the PLC communication speed will be greatly improved, realizing real-time communication with a large number of devices and systems. In addition, the application of edge computing technology will enable PLC to have the ability to process and analyze data locally, reducing data transmission delays. Modular and reconfigurable designs will also make PLC more flexible and adapt to the needs of different industries and application scenarios. In short, technological innovation will enable PLC communication to play a more important role in industrial automation.
2. Product Research
2.1 PLC Communication Method
2.1.1 Parallel Communication and Serial Communication
Parallel communication is a data transmission method based on bytes or words. In addition to multiple data lines and a common line, control lines are also required. Its transmission speed is fast, such as in data communication between PLC internal components, between host and expansion modules, or between short-distance intelligent modules, it can quickly transmit data. However, due to the large number of transmission lines and high cost, it is generally suitable for short-distance data transmission.
Serial communication is a data transmission method based on binary bits. Only one data line is needed in one data transmission direction, which serves as both a data line and a communication control line. It requires fewer signal lines and is suitable for occasions with longer distances. Serial communication is generally used in industrial control, such as data communication between PLC and computer, and between multiple PLCs. Commonly used standard transmission rates are 300, 600, 1200, 2400, 4800, 9600 and 19200bps, etc. Different serial communication transmission rates vary greatly, some are only hundreds of bps, and some can reach 100Mbps.
2.1.2 Simplex, Duplex and Full-Duplex Communication
Simple communication can only send or receive data in a single direction, such as the typical simplex communication between ordinary remote controllers and receivers. Full-duplex communication means that data is allowed to be transmitted in both directions at any time during communication. For example, when you call your girlfriend to have a quarrel, both parties can send and receive data at the same time. Usually two pairs of twisted pair cables are required for connection, and the communication line cost is high, such as RS-422. Half-duplex communication can realize two-way communication, but it cannot be carried out in both directions at the same time, and must be carried out alternately. The common RS485 interface is half-duplex communication, and MODBUS, USS, PROFIBUS and other protocols based on this interface are all half-duplex communication.
2.1.3 Asynchronous communication and synchronous communication
Asynchronous communication transmits more additional non-valid information and has lower transmission efficiency. It is generally used for low-speed communication. For example, PLC generally uses asynchronous communication. The data characters it sends consist of a start bit, 7~8 data bits, 1 parity bit (optional) and a stop bit (1 bit, 1.5 or 2 bits). Synchronous communication uses bytes as units, and transmits 1~2 synchronization characters, several data bytes and check characters each time. Synchronous communication has high transmission efficiency, but has high requirements on hardware. It is generally used for high-speed communication, such as data communication with a transmission rate higher than 20Kbit/s.
2.1.4 Baseband transmission and frequency band transmission
Baseband transmission is the direct transmission of digital signals on the channel according to the original waveform, requiring the channel to have a wider passband. It does not require modulation and demodulation, the equipment cost is low, and it is suitable for data transmission in a smaller range. It is often used in PLC communication. Frequency band transmission is a transmission form that uses modulation and demodulation technology. The sending end converts the digital signal into an analog signal with a certain frequency band range, and the receiving end performs the opposite conversion. Frequency band transmission is more complex and the transmission distance is longer. If a modem is equipped through the local telephone system, the transmission distance can be unlimited.
2.2 PLC Communication Protocol
2.2.1 MODBUS Protocol
MODBUS protocol is widely used in both serial and Ethernet communications. In serial communication, it has the advantages of being simple to use and highly reliable, and is suitable for data exchange between multiple devices. In Ethernet communication, MODBUS TCP protocol can achieve high-speed data transmission and can communicate with different types of devices.
2.2.2 Profibus protocol
The Profibus protocol has outstanding features in high-speed communication and multi-device connection. It can achieve high-speed data transmission rate and is suitable for industrial automation scenarios with high real-time requirements. At the same time, Profibus can connect multiple devices to form a complex industrial control system.
2.2.3 Ethernet/IP protocol
The Ethernet/IP protocol is based on TCP/IP and has the characteristics of high-speed communication and real-time performance. It can achieve fast data transmission in industrial networks and can be seamlessly connected with other TCP/IP-based devices.
2.2.4 CAN protocol
The CAN protocol uses differential signal transmission in the control system, with its own CRC error detection mechanism, and can be used normally in complex interference environments. The data format of the CAN protocol includes identifiers, control fields, data fields, etc. Its communication method is multi-master competition, and multiple nodes can send data at the same time. The data transmission order is determined by the priority of the identifier.
3. Application scenarios
3.1 Industrial automation
3.1.1 Switching logic control
In the application of modular machine tools, PLC communication can achieve precise control of each workstation. For example, by connecting various sensors and actuators through PLC communication, when the sensor at a certain station detects that the workpiece is in place, the PLC quickly issues a command to start the corresponding processing equipment. In the packaging production line, PLC communication can coordinate various linksActions such as material conveying, packaging sealing, labeling, etc. Through precise switch logic control, the production line is ensured to run efficiently and stably. According to statistics, in some advanced packaging production lines, the production efficiency can be increased by more than 30% after adopting PLC communication control.
3.1.2 Analog Control
PLC communication plays a vital role in the control of continuous variable quantities such as temperature and pressure. For example, in the chemical production process, the temperature of the reactor needs to be accurately controlled. The real-time temperature data is transmitted to the PLC through the temperature sensor. The PLC communication system makes judgments based on the preset temperature range and adjusts the output power of the heating or cooling equipment to keep the temperature stable near the set value. Similarly, in the oil industry, the control of pipeline pressure also relies on the collection and analysis of pressure sensor data by PLC communication to ensure that the pressure fluctuates within a safe range.
3.1.3 Motion Control
In the application example of driving the motor to make linear or circular motion, PLC communication can realize precise speed regulation and position control of the motor. For example, in CNC machine tools, PLC communication cooperates with the servo motor control system to control the speed and direction of the motor by sending instructions to achieve precise movement of the tool. In the automated warehousing system, the linear and circular motion of the stacker is also controlled by PLC communication to ensure accurate storage and retrieval of goods.
3.1.4 Process Control
In closed-loop control applications in industries such as metallurgy and chemical engineering, PLC communication works closely with various sensors and actuators. Taking the metallurgical industry as an example, PLC communication collects parameters such as furnace temperature, furnace pressure, and flow in real time, and adjusts fuel supply and ventilation according to preset control algorithms to achieve precise control of the metallurgical process. In the chemical industry, PLC communication can achieve closed-loop control of multiple parameters such as temperature, pressure, and liquid level in the reaction process, improving product quality and production efficiency.
3.1.5 Data Processing
In large control systems, PLC communication plays an important role in data collection, analysis and processing. For example, in the monitoring system of a power plant, PLC communication can collect the operating parameters of each device, such as the output power, voltage, current, etc. of the generator, and transmit these data to the central control room for analysis and processing. Through real-time monitoring and analysis of large amounts of data, hidden dangers of equipment failure can be discovered in a timely manner, providing a basis for preventive maintenance.
3.2 Smart Home and Smart Building
3.2.1 Home Appliance Control
In smart homes, PLC communication can achieve remote control and linkage control in a variety of ways. For example, by connecting to the PLC communication system through a mobile phone APP or smart voice assistant, you can remotely control the switching and adjustment of home appliances, such as TVs, air conditioners, and water heaters. At the same time, linkage control can also be achieved, such as automatically turning on the living room lights and adjusting the indoor temperature when the owner is detected to return home.
3.2.2 Home Security Monitoring
Home security monitoring can be achieved by connecting smart devices such as cameras, smoke alarms, door and window sensors, etc. to the PLC communication system. When the camera detects an abnormal situation, the image information is transmitted to the user's mobile phone through PLC communication, and the alarm device is triggered at the same time. When the smoke alarm detects smoke, it immediately sends an alarm to the user through PLC communication to ensure family safety.
3.2.3 Building Automation
In building automation, PLC communication can realize intelligent management of elevators, lighting and other equipment. For example, the operation status and floor selection of elevators can be controlled through PLC communication to improve the operation efficiency and safety of elevators. In terms of lighting control, the brightness of lights can be automatically adjusted according to different time periods and light intensity to achieve energy saving effects.
3.2.4 Lighting and air conditioning control
In lighting and air conditioning control, PLC communication can improve comfort and energy saving. By connecting the light sensor and temperature sensor to the PLC communication system, the indoor light and temperature changes are monitored in real time, and the light brightness and air conditioning temperature are automatically adjusted to create a comfortable living environment for users. At the same time, when no one is indoors, some lighting and air conditioning equipment are automatically turned off to achieve energy saving.
4. Competition Landscape
4.1 Competition Strategies of Major Manufacturers
In the PLC communication market, different manufacturers have adopted diverse competition strategies.
- Product Technology: Internationally renowned manufacturers such as Siemens, Schneider, ABB, etc., have taken a leading position in the field of medium and large PLC communications with their long-term technology accumulation and R&D investment. They continue to launch products with more powerful functions and more stable performance. For example, Siemens' PLC products excel in communication speed, data processing capabilities and reliability. It uses advanced communication protocols and technologies to achieve efficient interconnection with a variety of devices and meet the needs of complex industrial automation systems. At the same time, these manufacturers are also constantly exploring the application of new technologies, such as intelligent and modular design, to improve the competitiveness of their products.
Domestic manufacturers such as Inovance Technology and Supcon are making efforts in the small PLC communication market, focusing on the cost-effectiveness of products and customized services. Through continuous technological innovation, Inovance Technology has achieved remarkable results in the fields of servo motors and frequency converters. Its PLC products have also gradually won customer recognition in the market with good compatibility with other products and customized functions for specific industries. For example, in some emerging industries, such as lithium batteries and semiconductors, Inovance Technology has developed special PLC communication solutions based on customer needs to improve production efficiency and product quality.
- Price: Domestic manufacturers usually attract customers with lower prices, and reduce product prices through large-scale production and cost control. For example, in the small PLC communication market, domestic manufacturers' product prices are relatively low, which can meet the cost-sensitive needs of small and medium-sized enterprises. In the medium and large PLC communication market, although international manufacturers have higher prices, they still occupy a certain market share with their brand advantages and product performance.
- Service: Domestic manufacturers pay more attention to localized services, can quickly respond to customer needs, and provide on-site debugging and technical support. For example, in the chemical, power and other industries, Supcon has established a complete after-sales service network to promptly solve problems encountered by customers during use, thereby improving customer satisfaction. International manufacturers are also constantly strengthening the construction of service systems. For example, Schneider has established multiple technical service centers around the world to provide customers with comprehensive technical support and training services.
4.2 Market share trend
In recent years, the share of the PLC communication market has shown a dynamic trend. In the medium and large PLC communication market, the market share of international manufacturers is still large, but with the continuous improvement of the technical level of domestic manufacturers and the gradual maturity of their products, the market share of domestic manufacturers is gradually expanding. For example, in some industries with high reliability requirements, such as metallurgy and electricity, domestic manufacturers' products have begun to gradually replace imported products.
In the small PLC communication market, the market share of domestic manufacturers has grown rapidly. With its flexible customized services, high cost-effectiveness and fast-response after-sales services, domestic manufacturers have been widely used in the semiconductor, textile, packaging and other industries. It is expected that in the future, with the continuous advancement of domestic manufacturers' technology and market expansion, the share of domestic manufacturers in the small PLC communication market will continue to grow.
At the same time, with the development of industrial automation and intelligence, new application areas continue to emerge, such as smart grids, smart homes, smart transportation, etc. This provides new market opportunities for different manufacturers and will also promote further changes in market share. Manufacturers will continue to adjust their competitive strategies, strengthen technological innovation and product research and development to adapt to market changes and customer needs.
5. Supervision policy
5.1 Industry standards and specifications
PLC communication is a key technology for industrial automation and intelligence, and its industry standards and specifications are crucial. China's General Administration of Quality Supervision, Inspection and Quarantine and China Standardization Administration have successively issued a series of national standards, such as the GB/T 15969 series of national standards, which covers 8 parts of sub-standards such as general information related to PLC, equipment requirements and testing, programming languages, and user guidelines. It provides comprehensive and systematic definitions and guidance for PLC programming, communication, equipment requirements, integration, and practical applications, and provides guarantees for the standardized development of the industry.
In addition, there are also relevant standards for information security of industrial control systems. The national standard GB/T 33008.1 - 2016 "Industrial Automation and Control System Network Security - Programmable Controller (PLC)" issued in October 2016 specifies the security protection requirements for network security detection, evaluation, protection and management in the PLC field of industrial automation and control systems, and improves the industry network security standard system.
5.2 Impact of policies on the industry
Policies play an important role in promoting and guiding the development of the PLC communication industry. In the past decade, the country has attached great importance to the intelligent manufacturing industry and has successively issued a series of industry support policies and industry supervision policies to promote the intelligent development of industrial clusters, which has also promoted the healthy and orderly development of the PLC industry to a certain extent.
In terms of industry support policies, in 2011, the Ministry of Industry and Information Technology issued the "Several Opinions on Accelerating the Deep Integration of Informatization and Industrialization", proposing to enhance the ability of the information industry to support the deep integration of "two informatizations", vigorously develop high-end numerical control systems, manufacturing execution systems, industrial control systems, etc., and provide policy support for the development of the PLC industry. In 2015, "Made in China 2025" proposed to promote the deep integration of informatization and industrialization, accelerate the improvement of the network security protection capabilities of intelligent manufacturing industrial control systems, vigorously develop intelligent manufacturing equipment products, break through intelligent core devices, and promote the industrialization process of intelligent manufacturing complete sets of equipment. Among them, PLC, as an important part of industrial control systems, will also benefit from these policies.
In 2016, the "Guiding Opinions on Deepening the Integration of Manufacturing and Internet Development" and the "Smart Manufacturing Development Plan (2016-2020)" and other policies also provide a good policy environment for the development of the PLC industry. These policies propose to improve the security protection level of industrial information systems, improve the laws and regulations and standards system for industrial information security management, accelerate the development of intelligent manufacturing equipment, vigorously break through core products such as PLC, and accelerate the industrialization process of complete sets of intelligent manufacturing equipment.
In terms of industry regulatory policies, in 2016, the Ministry of Industry and Information Technology issued the "Guidelines for Information Security Protection of Industrial Control Systems", which put forward security protection requirements and implementation details for industrial control companies in terms of access control strategy construction, data security protection, asset configuration management, etc. for the entire life cycle of industrial control system design, selection, construction, testing, operation, maintenance, and disposal, ensuring the security of PLC communication.
To sum up, policies have an important role in promoting and regulating the development of the PLC communication industry, and provide a strong guarantee for the healthy and orderly development of the industry.
6. Other influencing factors
6.1 Driving force of technological innovation
Multi-carrier modulation technology such as orthogonal frequency division multiplexing (OFDM) has a significant impact on PLC communication. OFDM technology decomposes high-speed data streams into several sub-bit streams, and each sub-bit stream modulates several sub-carriers for transmission. Compared with traditional technologies, OFDM has the advantages of strong anti-attenuation ability, high frequency utilization, suitable for high-speed data transmission, and strong anti-inter-code interference ability. For example, in power line communication, most AC noise frequencies are below 2MHz, while the carrier frequency of high-speed broadband PLC chips is 2-12MHz and will not be affected by this. At the same time, the physical layer of high-speed broadband PLC chips supports FEC (Forward Error Correction) and CRC (Cyclic Redundancy Check) functions, with powerful denoising and error correction capabilities, and a specific noise filtering algorithm to improve noise tolerance.
Spread spectrum technology also plays an important role in PLC communication. Based on the direct sequence spread spectrum mechanism, it has strong anti-interference ability and is suitable for reliable data information transmission in harsh communication environments such as low-voltage power lines. It can also implement code division multiple access technology to achieve simultaneous communication of different users on low-voltage distribution networks, and the power spectrum density of the signal is very low, with good concealment and not easy to be intercepted. However, due to the limitation of its principle, the maximum transmission rate of spread spectrum communication can only reach about 4800lKbit/s.
6.2 Integration with other technologies
The integration of PLC communication with technologies such as the Internet of Things and big data has broad development prospects. With the development of industrial Internet of Things, PLC, as a core component of industrial control, is increasingly integrated with the Internet of Things platform. For example, the BlueBee EMCP Internet of Things cloud platform is an industrial-grade comprehensive Internet of Things cloud platform that supports seamless access for multiple users, across industries, and across devices. The BlueBee Internet of Things gateway collects field equipment data, processes it on the edge, and then transmits the processed data to the EMCP Internet of Things cloud platform to realize functions such as data alarm report analysis and cloud configuration large-screen display.
PLC communication and big data technology integration can realize the collection, analysis and processing of large amounts of data. In large control systems, such as unmanned flexible manufacturing systems, PLC controllers can complete data collection, analysis and processing, and compare with reference values stored in memory to complete certain control operations, and can also use communication functions to transmit to other intelligent devices.
In the future, with the continuous development of technology, the integration of PLC communication with the Internet of Things, big data and other technologies will be closer, providing a stronger impetus for the development of industrial automation and intelligence.
7. Risk Analysis
7.1 Risk of Technology Upgrading
With the continuous advancement of science and technology, the development of communication technology is changing with each passing day. New communication technologies are constantly emerging, which may put existing PLC communication products at risk of being eliminated. For example, the high speed, low latency and large capacity characteristics of 5G technology may have an impact on traditional PLC communication methods. If PLC communication cannot keep up with the pace of technological development in a timely manner, it may gradually lose its market competitiveness.
According to statistics, the replacement cycle of communication technology is getting shorter and shorter, and there will be major technological breakthroughs every 3-5 years on average. In this context, PLC communication companies need to continuously increase R&D investment, keep up with technological development trends, and deploy new technologies in advance to reduce the risks brought about by technological replacement.
7.2 Risks of intensified market competition
Increasingly fierce competition in the PLC communication market may lead to price wars and affect corporate profitability. At present, there are many manufacturers in the global PLC communication market, including internationally renowned brands and domestic emerging companies. In order to compete for market share, companies may adopt a strategy of lowering prices, which will compress the company's profit margins.
For example, in the small PLC communication market, the number of domestic manufacturers continues to increase, and market competition is becoming increasingly fierce. In order to quickly open up the market, some manufacturers may lower product prices, thus triggering a price war. Price wars will not only affect the profitability of enterprises, but may also lead to a decline in product quality and affect the overall development of the industry.
In order to cope with the risks of intensified market competition, enterprises need to continuously improve product quality and service levels, strengthen brand building, and increase product added value. At the same time, enterprises can also open up new market areas through technological innovation and differentiated competition strategies, and avoid over-reliance on price competition.
7.3 Risk of policy changes
Policy adjustments may have an adverse impact on the development of the PLC communication industry. The government's industrial policies, environmental policies, trade policies, etc. may have a significant impact on the industry. For example, if the government's support for industrial automation and intelligent manufacturing weakens, it may affect the demand for the PLC communication market.
In addition, changes in trade policies may also have an impact on the import and export business of PLC communication companies. If trade frictions intensify, it may lead to higher tariffs and increased trade barriers, affecting the international market competitiveness of companies.
In order to reduce the risks brought by policy changes, enterprises need to pay close attention to policy trends and adjust their development strategies in a timely manner. At the same time, enterprises can also strengthen communication and cooperation with government departments, actively participate in the formulation of industry standards and policy making, and contribute to the healthy development of the industry.