Intelligent Building Electrical Equipment Based on Industrial Ethernet

Industrial Ethernet IP network technology Embedded operating system intelligent controller In the current intelligent building building automation system, due to the existence of various fieldbus standards, the control of the controlled electrical equipment in the building automation system is scalable and interoperable. There are huge obstacles in terms of the basics that are simply monitored by the on-site controller. Some of the operating parameters of the equipment are not based on changes in the application environment and the performance of the equipment itself is optimized synchronously. The main reason is that the provider of the field controller does not have the ability to design and manufacture the controlled device itself, and the setting of the environmental parameters of the intelligent electrical device itself cannot be optimized. However, embedding the Ethernet-based controller directly in the controller of the equipment by the electric equipment manufacturer can better change this situation.

The Ethernet transmission mode is obviously superior to various field bus protocols in terms of fast transmission speed, easy installation, high cost performance, and good compatibility. Therefore, all countries in the world have studied Ethernet as a de facto industry standard in order to achieve "plug and play" in the control system of building electrical equipment. This article proposes an intelligent integrated building electrical equipment production strategy for industrial Ethernet controllers with embedded real-time operating systems, and proposes a more effective integrated control concept for building control systems that use conventional field buses and field controllers.

1 The application of Ethernet and IP technology in the field of measurement and control The basic principle of the measurement and control system based on IP network technology is to replace the traditional serial buses with Ethernet (Ethernet) and to replace the traditional ones with the open common TCP/IP protocol. The special communication protocol developed by the manufacturer itself integrates the equipment's own control system and building automation system into one through product manufacturing. This system is a fusion of traditional measurement and control technology and the latest information technology, which is not available in other types of measurement and control systems in the past. The key technology is to solve the "non-determinism" of Ethernet data transmission, enhance the real-time nature of the data, and the reliability level of the TCPAP protocol, and achieve the real-time, interoperability, and controllable requirements in the field of measurement and control, and thus in modern automation networks. In the implementation, the control layer and the information layer are seamlessly connected (full compatibility).

Relative to some developed countries, China has long been in a technologically backward position in the traditional field of measurement and control. Intelligent measurement and control technologies and markets are being held by international manufacturers for a long time. Chinese researchers and manufacturers have always faced international manufacturers’ monopoly and market monopoly. China was the earliest country that applied open network technology and open communication protocols to apply research in the field of intelligent measurement and control. We Taihao Technology and research institutions and experts and scholars have conducted research in this area, but the progress is slow, there is no practical product, and no systematization. Although foreign manufacturers recognize the development trend of Ethernet and IP technology in the field of measurement and control, due to the technology and market monopoly in the field of traditional measurement and control, there is a great deal of inertia in the adoption and promotion of new technologies. Although this is being studied, At the end, there are products and systems available. In other words, research is based on Ethernet and IP technology for the field of measurement and control, and intelligent building electrical equipment is at the leading level worldwide.

In a nutshell, the basic technical innovation of the measurement and control system based on IP network technology is the first successful implementation of Ethernet and TCP/IP technology in the traditional field of measurement and control in the world. The traditional measurement and control technologies are based on the closed and unopened communication protocols of various manufacturers, which brings great difficulties to the construction of intelligent buildings. The original measurement and control technology is applied in large-scale intelligent buildings. Due to the defects of the technology itself and the closedness of the technology, it is difficult to achieve integration between the systems. This is a very real and very important solution to the current needs. The Ethernet TCP/IP protocol is an open standard protocol that has been used only for data communication between computers and belongs to a different technical field than measurement and control technology. At present, many measurement and control manufacturers are vigorously promoting the application of Ethernet and IP technology in the field of measurement and control. The successful development of the measurement and control system based on IP network technology has provided an unprecedented opportunity for China's development in the field of measurement and control: to break the market monopoly and technology monopoly of foreign products, and to take the initiative in the future development trend of measurement and control technology.

The transport layer of Ethernet is based on the CSMA/CD mechanism. This mechanism is particularly inefficient for the transmission of random data. This feature makes the transmission delay of the same size data in different time will be different, and the uncertainty of Ethernet transmission data is caused by this.

According to the current and foreseeable future development trend of network transmission technologies, the 1/, 110, and 11' protocols are undoubtedly the mainstream technologies in the future. The adoption of these protocols compared to fieldbuses has further increased the amount of data transferred.

Ethernet based on the current mainstream protocol must be improved or take other measures to meet the application in the industry.

The following is a detailed analysis of the time spent when transmitting with Ethernet and Fieldbus for the same amount of data. Take Ethernet and 1.2mm CAN busses as an example. For example, useful data (which must be used in the industrial field) is 10 bytes. When using the CAN bus, there is no overhead other than adding 26 bytes of frame headers. Ethernet using TCP/IP protocol requires an additional overhead of 4050 bytes. In this way, the same data is transmitted, the time for the CAN bus is 80100xs, and the Ethernet time is much shorter. If the upper layer protocol, such as HTTP, is used, Ethernet will need more data, but due to the difference in bandwidth, the total time is not much more than that of the CAN bus. Of course, this result is based on the premise that Ethernet does not collide. Once the data collision occurs, the above calculation has no practical significance. Although people made the following conclusions through long time statistics: When the data flow is less than 40% of the bandwidth, the probability of collision is very small, but in terms of a certain data packet, the data delay cannot be determined.

2 Influence of the embedded real-time operating system on the determinism of transmission time At present, there are several international solutions to solve the uncertainty of Ethernet transmission. One of them is the combination of token mode and Ethernet mode.

Although this approach helps solve the problem, it also damages the versatility of Ethernet. However, this idea is a good way to solve the uncertainty of Ethernet transmission time. Whether this idea can be expressed in other ways, the introduction of a real-time, multitasking operating system with priority level control can solve this problem.

The biggest difference between embedded real-time operating systems and general operating systems is the real-time response. Real-time is controlled by the priority of the task. Tasks that require real-time response have a high priority. Tasks that do not require real-time response have a low priority. High-level tasks only run when needed, so tasks with high priority take very short time during the entire run time, creating conditions for reducing the uncertainty of Ethernet transmission time.

The uncertainty of Ethernet transmission time is mainly due to the fact that different priority transmission information cannot be distinguished at the Ethernet transmission layer. If Ethernet's transmission process is regarded as a higher-priority task and real-time response task is a higher-priority level, Ethernet transmission will occur only when needed, which will reduce some unnecessary responses. When all Ethernet nodes operate in this manner, the total amount of data exchanged is reduced. When real-time response is needed, because this task has a higher priority level, it can directly interrupt the currently unfinished Ethernet transmission task, and package the content to be sent immediately to the Ethernet for transmission (recall the Ethernet transmission task again). , to further reduce the uncertainty of time.

In the field bus, the master-slave protocol can ensure the determinism of the transmission time. The introduction of the embedded real-time operating system can also enable the Ethernet transmission to exhibit a transmission mode similar to the master-slave protocol.

When Ethernet transmission is used, a high-level protocol such as HTTP is used, meaning that the on-site device becomes a server and the monitoring device becomes a client. If the above-mentioned priority level control is adopted, it means that the client is equivalent to the master station and the server is the slave station. The operating system limits the transmission time of the Ethernet to a relatively clear range and further compresses the transmission time. Uncertainty.

The introduction of the embedded real-time operating system is significant for implementing multiple HTTP connections. In some industrial fields, when the real-time requirements are not satisfied and the requirements for information monitoring and browsing are poor, due to the uncertainty of connection requests, traditional programming methods may cause the connection time to be too long or cannot respond to more than one connection at the same time. . The introduction of multitasking operating systems can successfully respond to more than one connection by successfully implementing multiple tasks. Through the SNMP response to the Ethernet request QoS allocation, the embedded WEB operating system and the intelligent building electrical equipment based on the Ethernet transmission capability are passed through the building integrated wiring system and the human control network. People can conveniently monitor and control the controlled devices just like a familiar web browser.

The application of Ethernet in the industrial field is a general trend. Although there are issues such as transmission time uncertainty, but with the adoption of Ethernet with higher transmission rates and the use of embedded real-time operating systems on intelligent building equipment, the transmission of Ethernet is standardized to make it unpredictable. It becomes controllable within a certain period of time. It is entirely possible to achieve or exceed the performance of the fieldbus in the time response. The fieldbus is far behind in the transmission rate.

3 Conclusion At present, the domestic manufacturers of intelligent building electrical integration optimization optimization led by Tellhow Technology Co., Ltd., through the high intelligent building electrical integration manufacturing capabilities, is gradually forming intelligent module air conditioning, intelligent building distribution equipment, intelligent mute Intelligent building electrical product chain based on industrial Ethernet and ip technology, such as generator set In the next few years, we will connect all kinds of intelligent electrical equipment through the building integrated wiring system, and simply use the browser to Various electrical devices controlled by the company are given orders to achieve the safe, efficient, energy-saving and environmental-friendly comfort of the entire smart building.