| In recent years, collapse accidents of large bridge occurred frequently, resulting in a lot of property and human losses. During operations, the structure of bridges will become aging and damaged inevitably. In the long-term effects of heavy vehicles, the internal stress may be severely damaged, causing some traffic problems. With the development of Internet of Things technology, wireless sensor network technology is increasingly being applied to the bridge structural health monitoring. Today, a growing number of large bridges are installed structural health monitoring system. Most of the bridge structural health monitoring systems include the monitoring the status of its vibration. Through collection and analysis of bridge vibration information, we can calculate the vibration modes of the bridge, and know the situation of injury and aging of the bridge structure.However, the amplitude of the bridge structure is small and the natural frequency of the bridge structure is very low. The environment of bridge monitoring is often harsh, not only to undergo changes in weather condition, but also suffered a complex electromagnetic interference. Existing structural health monitoring systems based on vibration information collected are often insufficient on the noise performance. A lot of bridge vibration information is submerged in noise, reducing the accuracy of the data, impacting the final modal analysis. In addition, due to the large bridge span, the communication distance is too long, which bring a range of communication quality problems, reducing the reliability of monitoring results.Based on past experience of bridge structural health monitoring, a set of vibration acquisition system used in the field of structural health monitoring was proposed and implemented. From the perspectives of the sensor choosing acquisition module design, circuit design, and power module design, the low-noise design is integrated. Making the new vibration acquisition system has significantly improved in data accuracy compared to previous systems.The proposed vibration acquisition system comprises the sensor module, control module, communication module and power module. Its sensor module uses acceleration sensor which has lower noise and higher sensitivity to improve the accuracy of data collection. Control module utilizes the powerful processing ability and reliable environment adaptability of the IRIS platform. Communication module uses a communication protocol with low power consumption, flexibility advantages. With the design of communication distance extender, the distance of wireless communication is extended. The design of the power supply module taking into account of the voltage stability and low noise, the system was supported clean and stable energy.Software design of low noise vibration acquisition system considers more of the practical application of the bridge structure monitoring. The system uses a polling way of transmission control. Time synchronization is taken into account in the software design. ACK mechanism was used in data communication for error control, which improves the reliability of data communication.Standard vibration experiment tested the accuracy of the vibration measurements. Comparative Experiment to previous system proofs that the low-noise performance of the system has significantly improved. |
