Low-power multi-hop wireless sensor network for vibration monitoring of large structures

Abstract

In recent years, structural health monitoring technology has received considerable attention for its potential to provide objective, accurate, and real-time assessment of structural conditions in comparison with the current periodic visual inspection practice. Battery-operated wireless sensors eliminate wires and make their installations easy. However, wireless data transmission consumes significant power and requires frequent replacement of batteries, which is particularly difficult for structures that are located in rural areas with poor accessibility. To address this obstacle, a low-power multi-hop wireless sensor network that monitors the vibration of large-size civil infrastructure is developed and validated in this work. The wireless communication devices employ special lowpower wireless devices that operate in the sub-GHz band, which allows for long-distance communication exceeding 1 km and easy deployment because no license is required. Data collection over wide areas is achieved through relay transmission (multi-hop communication), in which the wireless sensor data are received and retransmitted by surrounding sensors. A fail-safe function is built to achieve a sensor data collection rate of 99.999%. To save power, the communication timings are synchronized, and time-division communication is implemented, in which the wireless devices are made to sleep in time bands when communication is not needed. To validate this wireless sensor network, a field test was carried out to measure the acceleration response of a long-span suspension bridge, based on which the bridges natural frequencies and mode shapes were successfully identified. The field tests also demonstrated the ease of installation and operation of the wireless sensor system.