In today's automation field, the network structure has been widely used in industrial environments of various industries. It is the basis of various control systems. Its performance directly affects the overall indicators of the system. Different network types such as serial ports Communication, fieldbus, Ethernet, etc. have been verified and developed in various occasions, but with the rapid development of IT technology in recent years, this pattern is undergoing tremendous changes, especially Ethernet technology is being commercialized to industry. The upper layer develops and extends from low-level to low-speed to high-speed, non-real-time to real-time, closed to transparent, hierarchical to flat, and integrates various fieldbus technologies and protocols, coupled with low-cost stimulation and The speed increase factor, the global automation giants also continue to launch the "e network flattening the end" success story, the traditional control system has to face this strong challenge, Ethernet into the industrial control field and integrated into the field communication technology has become reality.
For the protagonist of the future automation network technology, from the perspective of the existing market application, the standardization, versatility and openness of the top-level application layer protocol in the Ethernet iso/osi seven-layer model determine whether each vendor's devices can interact with each other. The first condition of operationality, the standards and openness of application layer protocols provide a good implementation platform for interconnecting communication and achieving efficient and unified management for different levels, different vendors and different types of devices. Looking at the development of Siemens Industrial Ethernet simaTIc ie In line with the needs and trends of this market, the simaTIc ie architecture is shown in Figure 1.
Figure 1 simaTIc ie architecture diagram
The technology development path followed by simaTIc ie is a strategy that fully reflects standardization, versatility and openness. It combines efficiency, real-time, certainty, flexibility and other aspects, including standard Ethernet and custom Ethernet. Net, simatic ie based on "tcp/ip+standardization (profinet)+universality (s7/s5 compatible, it, iso, etc. communication) + open (open type ie)" is the most advanced development mode of industrial Ethernet It is well explained that s7 communication and s5 compatible communication are the standard communication protocols of the simatic plc family. The communication of the application interface does not depend on the specific bus system. It includes the Ethernet-based s7 station, s5 station and pg/ in the simatic net system. Inter-communication between pcs; and open-type IE refers to functional blocks based on s5-compatible communication or open communication using standard protocols (tcp native, iso on tcp, udp) stack to implement open communication services on the application layer, equivalent The service function for direct socket access is usually called open IE communication. The data exchange is implemented by the send/receive interface or the t blocks interface. It is based on The s7 plc control layer integrates the Ethernet service function to support data communication with third-party communication partners for Ethernet or tcp/ip; open IE communication provides an "empty application top-level" Ethernet service for user programming. To support free communication of tcp/ip port, suitable for binary or ascii code to communicate with external devices for free agreement or specific proprietary protocol.
Process technologyAs a company specializing in the production and sales of microprocessors mcu, ic and power semiconductor discrete devices, a semiconductor company's ic products are packaged, labeled, weighed, transported, and sorted. The included detection and collection equipment includes weighing instruments, label printers, barcode scanners, inkjet printers, sorters, etc. The commonality of these third-party devices is: wide distribution of equipment and high wiring costs, cumbersome protocols and no The same, the physical layer is not uniform, the networking performance is poor, the maintenance is complicated, the real-time requirements are not high, and the traffic is uneven. The networking solutions based on the above devices are currently commonly used in the following categories:
(1) Analog input and output module
(2) usb / rs232 / rs485 serial ptp communication
(3) Various types of fieldbus or device bus
(4) Industrial tablet / embedded computer
(5) pc base based tcp / ip program
The serial communication method is the most common in the above schemes. For example, s7-300 plc expands the serial port networking function through cp340/341, but there are different physical layers (rs232/422/485) and different protocol restrictions, which will inevitably lead to more expansion. A serial port is used to connect such devices, which increases system cost and complicated wiring. In addition, it is limited by factors such as low transmission rate, short communication distance, and difficult maintenance. Therefore, the existing shared Ethernet common transmission channel in the factory range is utilized. More obvious advantages than the above solutions.
First, the low-level part based on the osi Ethernet seven-layer model has a unified network medium access layer, that is, the physical layer and the data link layer conform to the ieee 802.3 specification, which means that the physical interface and driver level of the Ethernet hardware are unified, each The selection criteria for Ethernet-like standard ports and cables and their combined use provide great convenience for the interconnection of Ethernet port devices, ensuring that such devices can quickly and easily share information on the Ethernet common transmission channel.
Secondly, the middle layer part of the osi Ethernet model transport layer/network layer, which provides a unified ip-based tcp/udp protocol, which has the advantages of simple structure, easy integration of network resources and support for high-speed communication, where udp is based on ip Simple and fast data transfer protocol, because it only adds a small amount of management information in the sent packets, it can get higher data throughput than tcp/ip, but it is oriented to packet transmission, not connection-oriented. The characteristics of udp protocol data transmission are insecure. The "iso-on-tcp" in rfc1006 is an extension of the tcp protocol. It defines the attributes of iso transmission in the tcp/ip protocol. It combines the advantages of high-speed communication and routing compatibility, supports data block transmission with acknowledgment, and has high communication reliability. However, it is currently used only within the simatic s7 family of products. Third-party communication partners generally do not support iso-on. -tcp connection, so connection-oriented tcp/ip Ethernet communication becomes our first choice.
Based on the above, it can be concluded that the use of unified media access layer, standard tcp/ip transport network layer and open application layer Ethernet to achieve these third-party communication equipment networking is the preferred solution for this process automation control, so for the above industrial data collection The current state of the art, we have developed a tcp / ip based Ethernet communication solution, including the overall cost of equipment investment, wiring, maintenance and programming difficulties can be greatly reduced, it does not occupy the processor physical port and processing Resources, can be greatly improved in terms of flexibility and usability, and the synergy efficiency with the plc control layer has also been improved, reducing maintenance costs and further simplifying the network structure, and bringing about future system function expansion and upgrade. Great convenience, in line with the value proposition that manufacturers are increasingly concerned about.
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