The hottest sensor network has gradually come into

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The realization of low-cost and standardization of sensor networks has gradually entered the practical stage

recently, the sensor network that uses wireless networks to connect sensors and collect data began to enter the practical stage from the research stage. What are the applications of sensor networks? Why has it only recently been applied? Sumitomo precision industrial sensor network, which has actually participated in the development, has become one of the manufacturers in a large range in the domestic additive masterbatch industry. Miyamoto zhe (director of the technical department) was interviewed on the future topic

Q: what is the process of developing wireless sensor networks

Miyamoto: the opportunity for the sensor network to become the focus of attention is the "smart dust" program launched from 1998 to 2001. This is a plan funded by DARPA of the U.S. Department of defense and centered on the University of California Berkeley. Its purpose is to develop ultra small wireless sensor nodes using MEMS (micro electro mechanical systems) technology. Just like the name of "smart dust", its ultimate goal is to make the subminiature sensor nodes float in the air, collect the surrounding environmental information, and transmit it to the distance through the network. Although it is still unable to float in the air, a small sensor node prototype with a volume of only about 10mm3 has been developed

after that, the plan to develop low-cost universal sensor nodes using commercially available components was promoted, and the sensor network platform "mica mote" put into production by crossbow technology in the United States was born. With the advent of popular sensor network platform, the research field of sensor network has also begun to expand to practical applications, and the feedback obtained from it has promoted the further development of sensor network platform

since it was originally DARPA's plan, in the past, there were many applications with strong military colors such as mastering battlefield conditions, and ecosystem investigation, factory equipment monitoring, human and object tracking, disaster prevention and other applications were also within the scope of research

in Japan, Sumitomo Precision Industry and crossbow are cooperating to develop mote related product systems. In the initial stage, universities and research institutions adopted more, and the actual adoption of stores and factories also increased in the past two to three years. Applications include energy-saving system for managing the temperature of fresh food cabinets in supermarkets, energy monitoring for energy conservation in offices and factories, etc. The sensor network is also applied to the control of factory automation equipment, which can reduce the construction cost caused by changing settings and layout by reducing wiring

in overseas, the above applications are widely carried out. Because there are many wide farms, sensor networks are used for environmental monitoring of farms. In view of the large agricultural and outdoor demand, which is expected to continue to increase in the future, crossbow launched the sensor network product "Eko" for such applications last year. The product has also been listed in Japan and has been adopted by agricultural universities and research institutions

"Eko" is a sensor node equipped with waterproof casing, dry cells and solar cells. The battery life is up to several years, reducing the trouble of replacing the battery. In California vineyards, this product has played a role in optimizing irrigation in soil moisture measurement. If it is not needed, it can reduce costs and improve grape quality at the same time. In addition, the product is also used for equipment monitoring in oil refineries. In the outdoor where it is difficult to ensure power supply, the sensor network that can cover a large area without wiring is very suitable. The wireless communication standard of this product adopts IEEE802.15.4

why is the application expanding now

Q: why has the application of expanding sensor networks only begun to be expanded now? Crossbow's system has been equipped with a small sensor OS "TinyOS" that can operate with the help of small memory capacity at the beginning of this century, and the basic technology has been roughly improved

Miyamoto: there are three main reasons for the development of sensor network applications: the development of hardware constituting sensor nodes, the establishment of wireless communication standards, research and the accumulation of prototype results

the first is the development of hardware that constitutes sensor nodes. Nowadays, the degree of low cost and low power consumption of microcontrollers, wireless ICs and sensors is becoming higher and higher. In mass production, the cost of one module can even be lower than 2000 yen. Because the effect obtained by using the sensor network varies from application to application, the target cost cannot be determined uniformly. In a large number of applications, the cost problems that hinder the practicality are being solved one by one. The improvement of improving battery life by reducing power consumption is also being carried out. In more and more cases, battery life, like cost, is no longer an obstacle to practicality

the second is the wireless communication standard. With the formulation of IEEE802.15.4, the physical layer used by ZigBee, in 2003, it is possible to use wireless without license with low power consumption at a speed of 250kbps sufficient to transmit sensor data. The application certificate of the technical standard of the radio wave method only needs to be obtained by the module and the sensor node, and the user does not need to obtain certification

before that, sensor data transmission used weak wireless and specific low-power wireless, and there were problems such as insufficient data transmission speed and complex wireless IC programming

in addition, since the IEEE802.15.4 standard wireless IC has begun to be popularized in various products, the cost of wireless IC is expected to continue to reduce. With the formulation of ZigBee, WirelessHART, isa-sp100 and other standards on the upper end of the protocol, the adoption of enterprise applications that adhere to global standards also began

the third reason - the accumulation of research and prototype results has driven practicality. For example, the abnormal monitoring of the equipment in the factory needs to detect the abnormal signs of the equipment by monitoring the vibration, so as to prevent the failure. To complete this operation, we need to establish a connection between the observed phenomenon and the equipment failure. In this kind of application that needs time verification before application, there are more and more examples of completing the analysis of sensing objects and entering the practical stage

what is the future topic

ask: in the future, what issues need to be solved to further popularize sensor networks

Miyamoto: I think there are two stages of popularization, and each stage has different topics

first of all, the topic of the ongoing wirelessly wired system is to reduce costs and ensure reliability. For some applications, cost and reliability are not a problem at present, but in order to expand the scope of application, improvements are still needed in the future

in terms of cost, I believe that as the output of sensor nodes increases, the price will gradually fall, and wireless applications will increase

in terms of reliability, some people worry that the reliability of wireless is not as good as that of wired. However, there is also a reliability problem with wired lines, which generally cooperate with fault safety measures in use. The same is true for wireless, which can get enough reliability as long as it is combined with fault safety measures. Moreover, in some use environments, the wired storage cable is corroded and damaged, and the wireless reliability is high. I believe that the reliability problem can be solved by clarifying the reliability required by the application and adding the necessary failure safety mechanism

in the next stage, our goal is to create new applications that only sensor networks can achieve. This requires continued technical development to move closer to the ultimate goal of "smart dust" such as achieving ultra miniaturization of nodes and low power consumption that requires almost no electrical component pool. Moreover, in the development of these technologies, we must find applications that can gather manpower and funds

the above applications require deep knowledge in the corresponding fields. Therefore, it is impossible to carry out research simply by relying on sensor network manufacturers. As people deepen their understanding of the possibility of sensor networks, I expect sensor network manufacturers to work with manufacturers with deep knowledge of specific applications to launch new applications

system elements and development priorities

Q: please introduce the elements of the sensor network

Miyamoto: it can be roughly divided into the sensor network part containing sensor nodes and the client part for sensor data processing. In some usage forms, the software development environment of sensor nodes is also needed

the first is the sensor node. The configuration of wireless parts such as frequency band and power, environmental tolerance performance, sensors that can be used, installation method and power supply type are determined by the hardware part

wireless network protocol is more important in software. The network shape is determined by it, and the battery life is also affected accordingly. The network morphology includes the star shape that can only collect sensor data and transmit directly to the customs, the shape that can multi hop transmission and relay, and the hybrid star shape that is composed of the star shape cluster that can be relayed by all nodes and formed with some relayable nodes as the center. Hybrid star can be divided into types that can change relay objects across clusters and types that cannot. Since repeatable nodes must receive data sent by other nodes, the battery life is significantly shorter than that of nodes that do not relay and simply send. In most sensor networks, the battery life of repeatable nodes is very short, so battery drive cannot be realized

next, the processing method of the data collected by the sensor network is determined by the client part. Some clients have prepared general sensor data display client software, but do you know the performance characteristics of the basic digital display electronic tensile testing machine and the usual protection of the equipment? Next, our technicians will introduce to you that the client software needs to be specially prepared according to the application, or embedded into the existing system after converting the data format

in addition, when using autonomous sensors and adding the inherent processing of applications to sensor nodes, it is necessary to develop sensor node software. At this time, we need to use the software development environment of sensor nodes. What language environment can it be developed in? What is OS? How about using the API of wireless network protocol? These are very important for improving development efficiency

connect the sensor node with the existing equipment. When using it like a wireless modem, there is no need to develop the sensor node software. What is needed is to exchange data with the sensor node working as a wireless modem through a certain interface. For the wireless communication of RS232C and other 1-to-1 communication forms, it can also be used in the "penetration" mode of direct wireless transmission of UART (Universal Asynchronous Receiver Transmitter) source data. If the 1-to-N communication form of RS485 master-slave communication is used, the transmission object in the wireless network must be informed to the wireless modem

Q: what is the focus of system development? In addition, what should software developers pay attention to when writing source code

Miyamoto: for sensor nodes with limited hardware resources such as memory capacity and processing speed, attention should be paid to the overall balance of data storage location and reading and writing timing in programming

take the data received through wireless communication and relayed to other nodes as an example. Due to the limited reception cache, the transmission processing must be carried out before it is full. But on the other hand, the processing of reading data from its own sensor is also in progress. Therefore, if the two cannot be balanced, the data will be lost and the traffic of the whole network will be reduced

of course, the programming level needs to be noted. When designing the system initially, it is also very important to estimate the feasible data transmission rate and the number of nodes

moreover, in order to reduce the load of sensor nodes, the complex processing is left to the server

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