I. Ethernet
Ethernet is one of the most common computer networks in the real world. There are two types of Ethernet: classic Ethernet and switched Ethernet, which uses a device called a switch to connect different computers. Classic Ethernet is the original form of Ethernet, with speeds ranging from 3 to 10 Mbps; while switched Ethernet is the widely used type of Ethernet, capable of operating at high speeds of 100, 1000, and 10000 Mbps, presented as Fast Ethernet, Gigabit Ethernet, and 10 Gigabit Ethernet, respectively.
The standard Ethernet topology is a bus topology, but Fast Ethernet (100BASE-T, 1000BASE-T standards) uses switches for network connection and organization to maximize network speed and efficiency by reducing collisions. This results in a star topology for Ethernet; however, logically, Ethernet still uses a bus topology and CSMA/CD (Carrier Sense Multiple Access/Collision Detection) bus technology.
Ethernet enables multiple nodes in a wireless network to transmit information. Each node must acquire a cable or channel to transmit information, sometimes called "ether" (this name comes from the 19th-century physicist's hypothetical electromagnetic radiation medium—optical ether. Later research proved that optical ether does not exist.) Each node has a globally unique 48-bit address, which is the MAC address assigned by the manufacturer to the network card, to ensure that all nodes on the Ethernet can identify each other. Because Ethernet is so ubiquitous, many manufacturers integrate Ethernet cards directly into computer motherboards.
II. Industrial Control
Industrial control refers to industrial automation control, which is mainly achieved through a combination of electronic, electrical, mechanical, and software technologies. It is also known as industrial control or factory automation control. It primarily refers to the use of computer technology, microelectronics technology, and electrical means to make factory production and manufacturing processes more automated, efficient, precise, controllable, and visible.
Industrial control has always been a bottleneck restricting the upgrading of China's equipment manufacturing industry and even its products. The equipment manufacturing industry is the core and foundation of industry, determining the level of a country's industry and technology, as well as its position in the global division of labor.
For industrial machine tools, domestic manufacturers rely on Siemens or Mitsubishi for comprehensive motion control solutions. Core motion control products, such as linear motors, AC servo motors, and systems, are the main components and application solutions for precise motion control, provided entirely by foreign multinational corporations. From product design to technology, everything is handled by foreign companies. Domestic machine tool manufacturers, on the other hand, understand the functions of these key components from an application perspective, focusing on how to use them and ultimately integrating them into a complete machine. This highlights the gap in manufacturing and the direction for improvement.
III. Problems with the Application of Ethernet in Industrial Control
Traditional Ethernet is a commercial network, and there are still some problems in applying it to industrial control, mainly in the following aspects.
(1) It suffers from poor real-time performance and uncertainty.
Traditional Ethernet employs the CSMA/CD media access control mechanism, with each node using the BEB (Binary Exponential Back-off) algorithm to handle collisions. This mechanism suffers from uncertain queuing delays, requiring each network node to compete for the right to send packets. During communication, nodes listen to the channel and can only send information when it is idle; if the channel is busy, they must wait. After transmission begins, collision checks are performed; if a collision occurs, transmission must be abandoned and retransmitted. Therefore, deterministic queuing delays and communication response cannot be guaranteed, failing to meet the real-time requirements of industrial process control. Furthermore, during periods of high traffic, there is a risk of data loss, thus limiting its application in industrial control.
(2) Industrial reliability issues
Ethernet was designed for office automation and did not consider the adaptability requirements of industrial environments, such as extremely high or low operating temperatures, and strong electromagnetic noise from large motors or other high-power equipment that affects channel transmission characteristics. If Ethernet is to be used in the lower levels of a factory floor, reliability issues must be addressed.
(3) Ethernet does not provide power and requires an additional power cable.
Industrial field control networks must not only transmit communication information but also provide power to field devices for operation. This is primarily for ease of cabling and maintenance, and bus power supply also reduces cabling costs.
(4) Ethernet is not an intrinsically safe system.
(5) Security issues
Ethernet, due to its use of the TCP/IP protocol, is susceptible to network security threats, including viruses, unauthorized intrusions by hackers, and unauthorized operations. Unauthorized users may gain access to the network's control or management layers, creating security vulnerabilities. While various security mechanisms such as user passwords, data encryption, and firewalls can be used to strengthen network security management, solutions specifically for industrial automation control network security require further investigation.
(6) Integration issues between the existing control network and the newly built Ethernet control network
Among these problems, real-time performance, determinism, and reliability have long been major obstacles preventing Ethernet from entering the field of industrial control. To address these issues, industrial Ethernet solutions have been proposed.
