Displacement measurement is critical to understand the real behavior of civil infrastructure systems. However, effective displacement sensing still remains as a challenging task. In this presentation, a real-time displacement estimation technique combining acceleration and GNSS measurement is presented, and its commercial applications are showcased. Then, three different sensing data fusion techniques are presented to estimate structural displacement under GNSS-denied environments. 

• An displacement estimation technique fusing acceleration and strain measurements is developed for structures with no nearby fixed targets. The primary contribution lies in simultaneous estimation of displacement and an unknown parameter associated with strain–displacement transformation, and improvement of displacement estimation accuracy.
• An displacement estimation technique combining an accelerometer and a vision camera is developed for structures moving in-plane relative to a nearby fixed target. The primary contribution lies in the automated scale factor estimation, development of an adaptive multi-rate Kalman filter for asynchronous fusion of acceleration and vision measurements, and improvement of feature matching by developing an ROI updating algorithm and two automatic mismatch rejection algorithms. 

An accelerometer and radar based displacement estimation technique is developed for structures moving out-of-plane relative to a nearby fixed target. The primary contribution lies in the automated selection of the best target and estimation of a conversion factor for radar system, and improvement of radar-based displacement estimation by developing an acceleration-aided phase unwrapping algorithm.

A suit of numerical and experimental tests are presented to showcase these displacement estimation techniques. 

BIO

Hoon Sohn received his B.S. and M.S. degrees from Seoul National University, Seoul Korea and Ph.D. from Stanford University all in Civil Engineering. He worked at Los Alamos National Laboratory (LANL) as a Technical Staff Member and at Carnegie Mellon University as an Assistant Professor. He is now a Professor at KAIST (Korea Advanced Institute of Science and Technology) in South Korea. His research interest has been in the areas of structural health monitoring, nondestructive testing, sensing technologies and data analytics.  He has published over 210 refereed journal articles, over 400 conference proceedings, and 12 book & book chapters. He is holding 28 domestic and 14 international patents, and his developed technologies are licensed and commercialized by private companies, resulting in over 1 Million USD licensing agreements. He is currently SPIE Fellow, Member of National Academy of Engineering of Korea (NAEK), and Member of Korean Academy of Science and Technology (KAST).