EPA stands for Ethernet factory automation. It is the mainstream technology in the field of commercial computer communication, such as Ethernet and TCP/IP, which is directly applied to the communication between industrial control field devices. On this basis, an open network communication platform is established for the communication between industrial field devices. It is a brand-new open real-time Ethernet standard suitable for industrial field devices. It applies a large number of mature IT technologies to industrial control systems, and establishes a brand-new standard for the real-time work of field devices by using efficient, stable and standard Ethernet and UDP/IP protocols to determine the communication scheduling strategy. This project is supported by the "863" high-tech research and development plan of China government. With the support of the National Standardization Administration Committee and the National Standardization Technical Committee for Industrial Process Measurement and Control, a standard drafting working group was established by Zhejiang University, Zhejiang Kong Zhong Science and Technology Co., Ltd., Shenyang Institute of Automation, Chinese Academy of Sciences, Chongqing University of Posts and Telecommunications, Tsinghua University, Dalian University of Technology, Shanghai Institute of Industrial Automation Instruments, Institute of Comprehensive Technical Economics of Mechanical Industrial Instruments and Beijing Huakong Technology Co., Ltd. After more than three years of technical research, a real-time communication control system solution based on industrial Ethernet was put forward.
The research of EPA real-time Ethernet technology is based on the CIMS theme series "Fieldbus control equipment based on high-speed Ethernet technology", "Research on field-level wireless Ethernet protocol and equipment development" and "Research on industrial field equipment, monitoring network and its key technologies based on Bluetooth technology". As well as "Research and Development of Distributed Network Control System Based on EPA" and "Product Development Simulation System Based on EPA", the key technical problems such as deterministic and real-time communication between industrial field devices, network power supply, interoperability, network security, reliability and Ethernet anti-interference have been solved successively, and a distributed network control system based on EPA has been developed and successfully applied to chemical and pharmaceutical production devices.
On this basis, the standard drafting working group drafted the first national fieldbus standard with independent intellectual property rights in China, EPA Architecture and Communication Specification for Industrial Measurement and Control System. At the same time, this standard is classified as 14 in the international standard IEC 6 1 158 (fourth edition). It is listed as the 14th application protocol cluster (public Profile Family 14, CPF 14) in the international standard IEC 6158, which indicates that China.
At present, with the development of computer, communication, network and other information technologies, the field of information exchange has covered factories, enterprises and even markets all over the world. With the further development of automation control technology, it is necessary to establish an integrated automation network platform from the industrial field equipment layer to the control layer and management layer, and to establish an enterprise information system based on industrial network technology. At present, the data information transmitted between different network layers of enterprises is becoming more and more complex, which puts forward higher requirements for the openness, interconnection and bandwidth of industrial networks.
EPA is an open network platform for industrial field devices based on this. Through this platform, not only industrial field devices (such as field controllers, transmitters, actuators, etc.) can be connected. ) communication based on Ethernet is realized, and the network of industrial field devices can keep pace with mainstream communication technology. At the same time, the integrated automation system of industrial enterprises can be realized by using the "E-net to the end" of all levels of networks from Ethernet field equipment to control layer and management layer.
Technical features:
1, deterministic communication
Ethernet adopts CSMA/CD (Carrier Sense Multiple Access/Collision Detection) medium access control mechanism, which has the characteristics of communication uncertainty, which has become the main obstacle to its application in industrial data communication networks.
Although Ethernet switching technology, full duplex communication technology and IEEE 802.1p&; The priority technology specified by q avoids conflicts to some extent, but it also has certain limitations:
The store-and-forward mechanism of (1) Ethernet switch also makes the communication delay uncertain. The uncertainty of communication delay mainly comes from its queuing delay. No matter which store-and-forward mechanism is adopted, when messages from multiple ports need to be forwarded to the same port at the same time, the switch must queue and buffer these messages and forward them in turn. Therefore, the size of the switch buffer pool will directly affect whether and when the message from a port can be successfully forwarded.
(2) The problem of "broadcast explosion" in Ethernet switch. In the industrial data communication network, real-time data messages widely sent by broadcasting will also conflict.
In addition to the requirements of real-time communication, the communication of industrial data communication network also has the following characteristics:
(1) Periodic and aperiodic information exist at the same time. Under normal working conditions, there are many periodic information (such as process measurement and control information, monitoring information, etc.). ) and less aperiodic information (such as emergency alarm, program download, etc. );
(2) Time-limited response. Generally, the response time of office automation computer LAN can be within a few seconds, while the response time of industrial control LAN should be 0.0 1- 1 second;
(3) The direction of information flow has obvious directionality, and the propagation relationship is relatively certain. Under normal working conditions, the transmitter only needs to transmit the measurement information to the controller, the controller transmits the control information to the actuator, the process monitoring and emergency time information from the field instrument is transmitted to the operating station, and the operating station generally only needs to transmit the downloaded program or configuration data to the field instrument.
(4) According to the configuration scheme, the transmission of information follows a strict time sequence;
(5) The amount of information transmitted is small, and the length of information is relatively small, usually only a few bits or a few, a dozen or dozens of bytes; The network throughput is small;
(6) The network load is relatively stable.
In the EPA system, according to the communication relationship, the control site is divided into several control areas, and each area is isolated from each other by an EPA bridge, so that the communication flow between devices in this area is limited in this area; Communication between different control areas is forwarded by EPA bridge; In a control area, each EPA device sends data to the network according to the pre-configured time-sharing principle, which avoids collision and ensures deterministic and real-time communication between EPA devices.
2, "E" network in the end
EPA is an open network technology, which is suitable for communication between industrial field devices. It adopts segmented architecture and deterministic communication scheduling control strategy to solve the uncertainty of Ethernet communication, so that COTS technology, which is widely used in industrial enterprise management and process monitoring network, can be directly applied to the communication between field devices such as transmitters, actuators, remote I/O and field controllers.
Using EPA network can realize the unification of communication network platform based on Ethernet technology from the bottom field device layer to the upper control layer and management layer in the integrated automation intelligent factory system of industrial enterprises, that is, the so-called "E(Ethernet) network to the end".
Using EPA can realize the seamless integration of vertical and horizontal information of smart factories in industrial enterprises;
Through the real-time data communication service provided by EPA network communication platform, the field intelligent devices and applications of different manufacturers can realize transparent information exchange and interoperability.
Using EPA network can realize the seamless integration of Ethernet-based information in all network layers from management layer to control layer to field device layer in smart factory. Users can access any equipment in the smart factory directly through common tools or software (non-dedicated software) through their own access rights anywhere in the world.
Using EPA's open network platform, the information can be seamlessly integrated between traditional control systems (such as DCS and PLC) and field bus control system FCS based on EPA, so that a large number of control and non-control information in industrial field devices can be seamlessly transmitted to manufacturing executive layer and enterprise management system. Through innovative technologies such as information integration, data comprehensive utilization and data value-added mining technology, efficient and intelligent management of the whole production process of industrial enterprises can be realized.
3. Interoperability
Different from the traditional 4-20mA standard, industrial data communication network not only needs to solve the problems of signal intercommunication and interconnection, but also needs to solve the problems of information intercommunication, that is, mutual identification, mutual understanding and interoperability of information.
The so-called signal interworking means that the communication medium, signal type, signal size, signal input/output matching and other parameters adopted by two devices that need to communicate with each other meet the same standard, that is, the physical layer standard. On this basis, using a unified data link layer protocol, different devices can be connected to the same network to achieve interoperability.
At present, almost all control systems use Ethernet and TCP/IP protocol as communication networks, which realizes the interconnection of devices. However, if only Ethernet and TCP/IP protocols are adopted, and there is no unified high-level protocol (such as application layer protocol), different devices can't understand and identify the meaning of information transmitted by each other, so information interoperability between open systems can't be realized.
Therefore, the EPA standard not only solves the problem of real-time communication, but also defines application-layer services and protocol specifications for user-layer applications, including system management services, domain download services, variable access services, and event management services. As for the middle layer such as session layer and presentation layer in ISO/OSI communication model, in order to reduce the communication processing load of equipment, it can be omitted and the interface with TCP/IP protocol can be defined directly at the application layer.
In order to support the interoperability between EPA devices from different manufacturers, the EPA standard adopts XML (Extensible Markup Language) as the EPA device description language, and specifies the description methods of device resources, function blocks and their parameter interfaces. Users can use the general DOM technology provided by Microsoft to interpret the EPA device description file without special tools to compile and interpret the device description file.
Step 4 make it public
EPA standard is fully compatible with IEEE802.3, IEEE 802.1p&; Q, IEEE802. 1D, IEEE802. 1 1, IEEE802. 15 and UDP(TCP)/IP, etc. UDP protocol is used to transmit EPA protocol messages, which reduces the protocol processing time and improves the real-time performance of message transmission.
In order to ensure the reliability of the EPA system, the EPA standard also adds the medium interface selection specification and cable installation guide for industrial field application environment.
Commercial communication cables (such as five types of twisted pair, coaxial cable, optical fiber, etc.). ) can be applied to EPA system, but it must meet the reliability requirements of industrial field application environment, such as using shielded twisted pair instead of unshielded twisted pair.
The EPA network supports the parallel transmission of messages from other Ethernet /WLAN/ Bluetooth protocols (such as FTP, HTTP, SOAP, MODBUS, ProfiNet and Ethernet /IP protocols). In this way, all applicable technologies, resources and advantages in the IT field can be inherited in the EPA system.
5. Hierarchical security strategy
For the network security problems caused by the adoption of Ethernet and other technologies, the EPA standard stipulates that hierarchical network security management measures should be taken from three levels: enterprise information management layer, process monitoring layer and field equipment layer.
EPA field devices use specific network security management function blocks to detect any messages they receive, such as access rights and access passwords, so that only legitimate messages can be processed and other illegal messages will be directly discarded, thus avoiding the interference of illegal messages.
In the process monitoring layer, different micro-network segments are logically isolated by using EPA network to prevent illegal message traffic from interfering with the normal communication of EPA network and occupying network bandwidth resources.
For remote access from the Internet, EPA proxy server and various available information network security management measures are adopted to prevent remote illegal access.
Step 6 lay off employees
EPA supports network redundancy, link redundancy and equipment redundancy, and provides corresponding fault detection and recovery measures, such as the release of equipment redundancy information, the management of redundancy status, automatic backup switching, etc.
Development course:
From June, 5438 to February, 2005, EPA was officially classified as 14 in the international standard IEC 6 1 158 (4th edition), and was also classified as/kloc in the international standard IEC 6 1 158.
In February, 2005, the communication protocol EPA (Ethernet for Plant Automation), which was independently developed in China, passed the vote of IEC national committees and officially became IEC/PAS 62409 document.
065438-2005 10, the results of "Top Ten News in the Field of Industrial Control and Automation in 2004" were announced, and "EPA was included by IEC and released as an international standard of PAS" ranked among the top ten news.
In June, 2004, 165438+ 10, "EPA fieldbus control equipment based on high-speed Ethernet technology" won the innovation award of the 6th Shanghai International Industry Expo.
From June 5, 2004 to 10, EPA real-time Ethernet received extensive attention at the 6th China International Hi-tech Fair.
September, 2004 Zhejiang University Central Control EPA Real-time Ethernet shocked MICONEX2004―― 15th International Instrument Exhibition.
In May 2004, Zhejiang University and the Central Control Office of Zhejiang University presided over the formulation of the EPA Standard (draft for comments), which passed the examination of the National Standards Committee.
In April 2003, based on the EPA standard, the research group developed a prototype verification system of distributed network control system based on EPA, which was successfully tried in the soda carbonization workshop of Hangzhou Longshan Chemical Plant.
From 065438 to 2003 10, the EPA Architecture and Communication Standard of Industrial Measurement and Control System jointly formulated by Zhejiang University and Zhejiang University Central Control passed the expert review.
065438+2003 10, the EPA national standard drafting working group was established.
From June 5, 2002 to 10, the project "EPA network communication technology and its control system based on Ethernet" of Zhejiang University Central Control passed the technical appraisal organized by Zhejiang Science and Technology Department.
200 1 10 CIMS led by Zhejiang University, and mainly undertaken by Zhejiang University, Tsinghua University, Dalian University of Technology, Shenyang Institute of Automation, Chinese Academy of Sciences, Chongqing Institute of Posts and Telecommunications, TC 124 and other units, and started to formulate the EPA standard.
EPA is the abbreviation of eicosapentaenoic acid, which is the main component of fish oil. EPA belongs to ω-3 series of polyunsaturated fatty acids, which is an important nutrient that human body can't synthesize by itself, so it is called essential fatty acid for human body. Although linolenic acid can be transformed into EPA in human body, the reaction in human body is very slow and the transformation amount is very small, which is far from meeting the demand of human body for EPA and must be supplemented directly from food.
EPA can help reduce the contents of cholesterol and triglycerides and promote the metabolism of saturated fatty acids in the body. So as to reduce blood viscosity, improve blood circulation, improve oxygen supply to tissues and eliminate fatigue. Prevent the deposition of fat on the blood vessel wall, prevent the formation and development of atherosclerosis, and prevent cardiovascular diseases such as cerebral thrombosis, cerebral hemorrhage and hypertension.