| Rail safety monitoring is an important surveillance method to guarantee the train driving security. The wireless sensor network system for rail monitoring could meet the urgent need for real-time, rapidly and wide-area monitoring. A large of nodes separately deployed on the rail and formed a wireless sensor network, could monitor the status of the railway in real time and provide data for subsequent analysis. WSNs gateway as an important device of the wireless sensor network system realized the interconnection of heterogeneous networks. In this paper, a WSNs gateway based on Zigbee-3G was developed for rail remote monitoring.Firstly, the architecture of wireless sensor network system for rail monitoring was briefly introduced. After analyzing the functional requirements of WSNs gateway, the access to networks were chosen. The gateway get access to wireless sensor network by Zigbee technology and get access to external network by 3G technology. And then the overall design schemes of gateway hardware and software were put forward for realizing its functions.Aiming at the hardware requirement of WSNs gateway, the communication layer and power supply layer were designed. In power supply layer, two kinds of power supply scheme, 220V AC power supply and solar DC power supply, were put forward for different working environment. Aiming at the interconnection demand of heterogeneous networks, the application software of WSNs gateway was developed on WinCE platform. And considering the data integrity, a data package complement mechanism was established and it can reduce the data loss rate to 0.6% efficiently. In addition, in order to realize the function of gateway files remote managing, a remote access mechanism was also formulated.Considering the complex electromagnetic environment of rail monitoring field, the electromagnetic compatibility of gateway hardware was designed. Analyzing the electromagnetic interference problems caused in railway signal system and gateway, the electromagnetic compatibility of gateway box, antenna and power supply circuit were designed by using shielding, grounding and filtering technology. And according to the requirement of relevant national standards GB/T 24338.5-2009, the gateway was tested and the results reached A lever.The performance of WSNs gateway developed was tested in lab, the test results showed that:the startup time of gateway was only 47s; could work at the temperature range-25℃ 75℃; the time to complete a data transmission is about 2min.The developed WSNs gateway was also tested in a certain scale in the center of the Beijing railway scientific experiments,20 sets of gateways and 40 sets of sensor nodes were deployed on the experimental section of rail, and a series of tests were completed on this platform. The field operation and laboratory test show that the WSNs gateway has advantages of quick start, stable operation, reliable data transmission and strong anti-interference capability, which can meet the requirement of rail monitoring. |
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