Design Of Distributed Data Acquisition And Communication System For Qinghai-Tibet Plateau Test Station

The phenomenon of upward freezing pulling and thawing settlement of frozen soil will seriously damage the roadbed and buildings on it,the safety of frozen soil engineering is inseparable from the long-term monitoring of various elements in the frozen soil environment.This paper,combining with the monitoring communication needs of the buildings and surrounding areas of the Tibetan Plateau Test Station of the Chinese Academy of Sciences,designs a communication system based on combination of wired communication and wireless communication to complete the data transmission for all distributed data collection monitoring nodes.And the long-term automatic monitoring of frozen soil engineering and research has been realized.The main tasks as follows:First of all,for the communication and power supply requirements in the frozen soil and stress monitoring of the pile foundation of the test station,this paper analyzes the common ground interference phenomena and causes of monitoring equipment,researches on isolated communication and isolated power supply technology,and designs an anti-interference wired communication system.The isolated power supply and photoelectric isolation communication technology effectively solve the problems of the power supply and communication to the pile-based monitoring equipment.The m-sequence-based BER test scheme is also designed to test the communication system mentioned above,the test BER is better than 10-7,which proves that it has reached the system communication technical indicators and achieved the isolation between the terminal monitoring node and the power communication bus,ensuring the stability of the monitoring system.According to the issue of data transmission to the pile-based monitoring system,combining with the existing communication lines of the test station,a Wi-Fi communication system based on monitoring node is designed,which can transport all the monitoring data from the system to the remote data center through the Wi-Fi technology to replace the GPRS in the wild.The above experiment was implemented in the actual project of the Test Station of the Chinese Academy of Sciences,and the operation situation for almost a year indicates:the stability and reporting rate of monitoring data have increased significantly compared to the previous period,as well as overall monitoring accuracy and stability of the monitoring system are improved.Secondly,considering that there are also several monitoring sections in the vicinity of the test station,the distance between these monitoring nodes from the test station ranges from a few hundred meters to several kilometers,and separate monitoring of these locations is inefficient and costly.Therefore,this paper designs a point-to-point directed Wi-Fi access scheme.To expand the coverage of the test station WLAN,wireless Bridge-Repeater is used,so that all monitoring nodes within a radius of 10 square kilometers around the test station can transport the monitoring data through the Wi-Fi communication system and the test station WLAN.The multi-AP automatic access technology is also studied and designed in order to enable each monitoring node to actively discover all existing AP access point information,extracting and comparing the signal strengths of all access point information,selecting the AP with the best performance status to access the network and connect and utilize it.The test results of the two monitoring programs show that:On the basis of the effect of monitoring the directed Wi-Fi access,the monitoring task can be completed by the monitoring nodes according to the design process of multi-AP automatic access,thereby the feasibility of the regional monitoring scheme near the test station was demonstrated,which gives full play to the advantages of the communication resources of the test station and improves system monitoring efficiency.