Project Report

Growing public concerns on the health of the aging civil infrastructures prospered structural health monitoring (SHM) using various sensors. Pinnacle technology on the wireless sensors enabled usage of wireless smart sensor network (WSSN) on the SHM and significantly lowered the entire cost of the network. Although researchers proposed methods to establish reliable WSSN, assuring accurate time synchronization of the wireless network and network communication are challenging features for implementing full scale monitoring of the structure. WSSN currently relies on CPU clock time for time synchronization. However, using PC clocks in particular is not reliable enough due to various effects on crystal tolerance such as calibration and/ or temperature effect. The effect results the network time drift of many mille-seconds. Also, reliable network communication is partially achieved by increasing number of sensors on the network or using strong antenna power. Usage of low-cost GPS receivers for time synchronizing the WSSN was proposed and studied in University of Tokyo to cure the problems. GPS is known to have satellite time synchronization every second and provide an accuracy of few nano-seconds. GPS time synchronized nodes also obsolete the need of communication within the network when collecting data from the environmentally challenging structures. During the research period in University of Tokyo, the first thing that I accomplished was encoding time signal from GPS signals. Separated time pulse and time index as a two different inputs, inputs were then combined with acceleration signal from an accelerator. In final design, pulse signal controls start threshold and end threshold of the accelerator and during the sensing period, time indices are stored as a memory and printed in the final stage. With the help of NSF EAPSI program, I could finalize the framework of this research and the study has been continued after the program with the good relationship with host researcher at University of Tokyo.

National Science Foundation (NSF)
Office of International and Integrative Activities (IIA)
Application #
Program Officer
Carter Kimsey
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Kim Robin E
United States
Zip Code