With such market demand and technological progress, industrial wireless sensor network technology came into being and has become a new hot spot in the field of measurement and control.
With the development of industries such as industry, agriculture, medical treatment, and health, and people's increasing emphasis on environmental protection and social security, a technology and product are needed to facilitate real-time perception, monitoring, and collection of multiple information within a certain range. And deal with. With such market demand and technological progress, the Industrial Wireless Sensor Network (Wireless Sensors Network referred to as WSN) technology came into being, and has become a new hot spot in the field of measurement and control.
The US military began to deploy as early as 1978, and the US Department of Energy also used industrial wireless technology in 2002 as a means to reduce overall industrial energy consumption by 5% by 2020. The US Presidential Science and Technology Advisory Committee pointed out in the "Federal Energy Research and Development Plan for the 21st Century" that the widespread application of industrial wireless technology will increase industrial production efficiency by 10% and reduce emissions and pollution by 25%.
The Chinese government has also included "Sensor Network and Information Processing" in the National "Eleventh Five-Year Plan" and the "National Medium- and Long-Term Science and Technology Development Plan Outline", and WSN is also listed as a supporting project in the national 863 and 973 plans. In addition, the National Natural Science Foundation of China, various provinces, cities, and large enterprises have also provided funding to create conditions for the rapid development of WSN.
Long way to go
After the emergence of WSN, WSN ranked WSN as one of the 21 most influential technologies in the 21st century in 1999; the MIT (MIT) Technology Review in 2003 included it in the report predicting the future development of technology In order to change one of the ten new technologies in the world; in 2003, American Business Week published an article in its future technology "special test" that pointed out that WSN is one of the four major technology industries in the world in the future and will set off a new industry wave.
About the formulation of WSN standards and protocols
In the IEEE (American Institute of Electrical and Electronics Engineers) 802.15 standard, Bluetooth and Zigbee are already available in the home and office fields, while HART7.1, ISA100 and WIA-PA in China are in the industrial field.
Among them, HART7.1 (Wireless HART) was officially approved by IEC on September 19, 2008, and became a publicly available specification (IEC / PAS62591Ed.1). This is the first industrial wireless communication technology to obtain this level of international certification. But ISA100 wanted to submit IEC to become the standard of IEC but failed to achieve it.
WIA-PA (WirelessforIndustryAutomation-ProcessAutomation) is a Chinese WSN standard led by the Shenyang Institute of Automation, Chinese Academy of Sciences and is currently under review. Its goal is to become China's national standard first, and then apply to become an international standard of IEC.
Features of WSN
The characteristics of WSN can be summarized in 12 words, namely "low-consumption self-organization, heterogeneous interconnection, and ubiquitous collaboration".
Low consumption self-assembly
"Low consumption self-organization" is the most important feature of WSN. Because it consumes a lot of power and cannot be powered by batteries, wireless cannot be achieved, so low power consumption is the key. "Self-organization" is self-organizing (adhoc) in the WSN mesh network, and each node in the network coordinates each other's behavior through distributed algorithms, without manual intervention and any other preset network Facilities can be quickly deployed and automatically networked at any time and place. When a node exits or joins, or a node's communication path with a contact is blocked, WSN can automatically resume the organization. Therefore, WSN has the characteristics of self-organization (weaving), self-optimization (chemical), and self-healing (healing).
Heterogeneous interconnect
"Heterogeneous interconnection" includes two parts: node-level and network-level heterogeneous interconnection. The former refers to the interconnection of nodes with different structures (such as sensors, transmitters, routers, etc.) within the same network; the latter refers to the interconnection of heterogeneous networks, such as the interconnection of wireless networks with different protocols or existing wired networks . The key to node-level heterogeneous interconnection is to design an open architecture suitable for WSN. The core is communication protocol design and research including wireless signal modulation and demodulation, MAC protocol and routing algorithms. The key to achieving heterogeneous interconnection between networks is the design and configuration of gateways. In short, the heterogeneous interconnect greatly solves the problem of network scalability.
Ubiquitous collaboration
In nature, things to be perceived are everywhere. Even in the industrial field, a large unit or project needs to be measured or controlled by thousands of parameters. "Ubiquitous" refers to this application situation. However, each node's energy, sensing, storage, and computing capabilities are quite limited, and the effective use of coordinated processing and control of the data and information measured between a large number of nodes increases the competitiveness of the enterprise's products and improves profitability. Is very important. Therefore, this is also one of the key technologies and features of WSN.
Current promotion of WSN in China
At present, two foreign companies have launched WSN products, one conforms to the wireless HART7.1 standard; the other adopts the ISA100 standard. But most of them are limited to temperature, pressure, flow and level transmitters. Domestic Chuanyi and Chongqing University of Posts and Telecommunications have also produced prototypes of wireless series transmitters and actuators, and China's WIA-PA has also been successfully tested on Angang Cold Rolling Mills (measurement points have reached 400 points).
Application of WSN
Due to the internationalization of the market, competition among enterprises is becoming more and more fierce. Major manufacturers are all developing in the direction of high and stable production, high quality and low consumption, environmental protection and safety. The continuous expansion of production scale (such as thermal power and nuclear power units has reached one million kilowatts, oil refining has reached more than ten million tons, and ethylene has also risen to one million tons). The requirements make the number of measurement and control points reach nearly 10,000 points. If a wired solution is used, the number of cables is also tens of thousands, which not only complicates engineering design, increases engineering investment, but also increases installation and maintenance costs. The application of wireless technology can reduce costs by more than 90%, so the application of WSN technology is unstoppable.
At present, wireless local area network (WLAN) or Wi-Fi (IEEE802.11) has been applied in industry, and wide area network (WWLAN) or WiMax (IEEE802.16) is also beginning to apply. WSN belongs to personal area network (WPAN), IEEE802.15 Is being developed. The difficulty is that on the one hand, it requires low consumption, and on the other hand, it must ensure the real-time, security and reliability of the communication, which are contradictory. Therefore, we must try to find its balance point and achieve overall optimization. For example, in terms of energy saving, in addition to the use of low-consumption chips and the development of high-performance batteries, it also adopts measures such as sleeping or semi-sleeping when each node is not communicating, or using light energy and mechanical vibration to convert it into electrical energy.
At present, domestic and foreign R & D institutions have obtained some gratifying results in the above-mentioned fields. At present, the distance of domestic HART wireless communication is within 200m, the battery life is 5 to 10 years, and the reliability is 99%. It can be seen that it can only be a supplement to the cable at present, which is used in data collection and cannot be used in control or security occasions.
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