Efficient and high-precision time synchronization for wireless monitoring of civil infrastructure subjected to sudden events

The implementation of a wireless smart sensor network (WSSN) to monitor a structure subjected to sudden events (e.g., earthquakes) poses many challenges. One typical challenge is to synchronize the data from different sensors during event-triggered sensing, because each wireless sensor has its own independent clock and their triggering time is generally different and unknowable. The challenge becomes more acute when real-time data acquisition is required to support vibration control or rapid damage assessment under sudden events. Although various strategies have been proposed to achieve synchronized sensing of WSSNs, all of these strategies fall short in addressing the challenges of sudden-event monitoring. In this paper, we first proposed an efficient two-stage time synchronization strategy for general structural health monitoring as a baseline and implemented it on a next-generation wireless smart sensor. Building upon the baseline method, efficient time synchronization strategies are proposed, which are fully autonomous and highly efficient for sudden-event monitoring. Two classes of events are considered: short-duration events, for example, bridge impacts, during which initial data loss issues are critical, and long-duration events, such as strong winds, which can benefit significantly from employing real-time monitoring. For short-duration events, a post-event time synchronization strategy is developed, which autonomously performs offline synchronization after measurement. For long-duration events, a real-time time synchronization strategy is proposed, which can support real-time applications under sudden events, for example, vibration control. These time synchronization strategies are experimentally validated to demonstrate the efficiency and accuracy (under 20-μs maximum error) of the proposed sudden-event synchronized sensing strategies.