Abstract

Displacement measurements are useful information for various engineering applications such as structural health monitoring (SHM), earthquake engineering and system identification. Most existing displacement measurement methods are costly, labor-intensive, and have difficulties particularly when applying to full-scale civil structures because the methods require stationary reference points. Indirect estimation methods converting acceleration to displacement can be a good alternative as acceleration transducers are generally cost-effective, easy to install, and have low noise. However, the application of acceleration-based methods to full-scale civil structures such as long span bridges is challenging due to the need to install cables to connect the sensors to a base station. This article proposes a low-cost wireless displacement measurement system using acceleration. Developed with smart sensors that are low-cost, wireless, and capable of on-board computation, the wireless displacement measurement system has significant potential to impact many applications that need displacement information at multiple locations of a structure. The system implements an FIR-filter type displacement estimation algorithm that can remove low frequency drifts typically caused by numerical integration of discrete acceleration signals. To verify the accuracy and feasibility of the proposed system, laboratory tests are carried out using a shaking table and on a three storey shear building model, experimentally confirming the effectiveness of the proposed system.

Highlights

  • IntroductionDisplacement measurements provide useful information for various engineering applications such as structural health monitoring (SHM), earthquake engineering, and system identification

  • Displacement measurements provide useful information for various engineering applications such as structural health monitoring (SHM), earthquake engineering, and system identification.Displacement responses from a structure can be obtained either by: (1) contact or (2) non-contact type sensors

  • We investigated acceleration-based displacement estimation algorithms based on the following criteria for possible use with the smart sensor:

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Summary

Introduction

Displacement measurements provide useful information for various engineering applications such as structural health monitoring (SHM), earthquake engineering, and system identification. Displacement responses from a structure can be obtained either by: (1) contact or (2) non-contact type sensors (see Table 1). The linear variable differential transformer (LVDT), one of the most commonly used contact type devices, requires a connection link between the structure and the fixed reference point; applications to large civil structures such as bridge deflection measurements are quite challenging due to the difficulties in sensor installation. GPS can be an attractive alternative as displacement can be conveniently measured, but the use of GPS is limited to long-period, large deflection structures such as high-rise structures and long-span bridges due to its relatively low sampling rate and accuracy [1,2,3]

Method
Displacement Estimation Using Acceleration
Wireless Displacement Measurement System
Imote2 Smart Sensor Platform
Implementation of the Displacement Estimation Algorithm on Imote2
Harmonic Motion Testing
Shear-Building Model Test
Conclusions
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