Abstract
Wireless sensor networks (WSNs) have been widely used to collect valuable information in Structural Health Monitoring (SHM) of bridges, using various sensors, such as temperature, vibration and strain sensors. Since multiple sensors are distributed on the bridge, accurate time synchronization is very important for multi-sensor data fusion and information processing. Based on shape of the bridge, a spanning tree is employed to build linear topology WSNs and achieve time synchronization in this paper. Two-way time message exchange (TTME) and maximum likelihood estimation (MLE) are employed for clock offset estimation. Multiple TTMEs are proposed to obtain a subset of TTME observations. The time out restriction and retry mechanism are employed to avoid the estimation errors that are caused by continuous clock offset and software latencies. The simulation results show that the proposed algorithm could avoid the estimation errors caused by clock drift and minimize the estimation error due to the large random variable delay jitter. The proposed algorithm is an accurate and low complexity time synchronization algorithm for bridge health monitoring.
Highlights
Bridges are an important part of transportation systems, Structural Health Monitoring (SHM) of bridges is indispensable and multiple sensors such as acceleration, displacement, temperature and strain sensors [1,2,3,4,5,6] are employed to collect the real-time information about bridges
The multiple Two-way time message exchange (TTME) in this paper provide an effective clock offset maximum likelihood estimation (MLE) approach for time synchronization in wireless sensor networks (WSNs) which is a potential application for SHM of bridges
This paper presents an easy method for MLE time synchronization for bridge monitoring wireless sensor networks
Summary
Bridges are an important part of transportation systems, Structural Health Monitoring (SHM) of bridges is indispensable and multiple sensors such as acceleration, displacement, temperature and strain sensors [1,2,3,4,5,6] are employed to collect the real-time information about bridges. To improve the TPSN [24] for ensuring the synchronization accuracy without consuming more power, Gong et al [33] proposed a partial TPSN time offset synchronization scheme for bridge health diagnosis WSNs. The transmission delay results in a large error for clock offset estimation, especially for the random variable delay portion. Nodes broadcast their time information packets periodically and the receivers use the time message to correct their local times This mechanism removes the variable delay from clock offset estimate at the sender but a variable delay is introduced into the estimation directly at the receiver. This paper takes an optimized TTME approach to achieve high precision time synchronization for the data acquisition in bridge health monitoring WSNs. We have discussed the details of the clock offset continuously increasing, optimized the execution time and speed of the TTME to meet the assumption in TPSN.
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