Research On Wireless Monitoring System Hardware For Distributed Rail Stress

In recent years, the rapid development of China’s high-speed railway passenger line construction, made a significant contribution to China’s economic construction. At the same time, the safety of the high-speed trains attracts much attention. Seamless rail plays the role of guiding and hosting the train, it has become imperative to monitor the health status of the seamless rail. Based on the urgent needs and practical significance for the seamless rail safety monitoring, this paper carried out the research of the distributed wireless monitoring system for rail stress. In this paper, the hardware design of wireless monitoring system is described principally, in aspect of the sensor nodes, gateways, as well as power supply design in detail.As the system front-end data acquisition, the performance of sensor nodes directly affects the accuracy and stability of the data collection. The nodes are designed in modular ideas and are composed of the power supply unit, the acquisition unit and the communication unit, which communicate with each other by both sides of the pin connection. Power supply unit provides an efficient, stable, low-ripple voltage output power for the other two units. Acquisition unit is responsible for a slight change of the strain resistance converted into a voltage signal through Wheatstone bridge, after amplification and filtering processing into the16-bit A/D converted into digital signals, sent to the MSP430F149microcontroller via the SPI mode. In the same time, rail temperature, box temperature and node temperature, collected by the multi-channel temperature sensor DS18B20are transfered to the microcontroller by the way of a single bus. The data will be sent to the communication unit by the serial port after treatment, and sent to a nearby gateway through the Zigbee wireless transmission finally.The gateway includes coordinating design, embedded computer selection,3G module and GSM short message service switch functional design. Processor is responsible for calculating data, protocol conversion and data exchange with the communication module. The coordinator uses Zigbee module Coordinator modes as a data receiving part of the core and peripheral circuits designed for reliability. In order to obtain the exact time and location information, the circuit used a GPS module in the production design. Use the GSM short message service switch to control gateway power supply remotely. Use3G module to make the gateway establish contact with the remote monitoring terminal server.Power supply solutions using solar panels and batteries, according to their respective power consumption of nodes and gateways, taking into account the continuous use5to7days to select battery capacity, the size of solar panels power consumption taking into account the continuous rainy weather and battery capacity. In order to protect the battery, a charge and discharge controller is designed to prevent battery overcharge and over discharge. In addition, the design of the mine protects the equipment from lightning damage.Finally, the laboratory testing and field long-term assessment of high-speed railway verify that the distributed rail stress monitoring system is reliable, the system can achieve the requirement of long-term real-time monitoring of the health status of seamless rail.