A smartphone camera and built-in gyroscope based application for non-contact yet accurate off-axis structural displacement measurements

Abstract Image-based optical methods have been widely used for noncontact structural displacement measurements, due to their prominent advantages over conventional contact sensors. However, existing optical methods usually require complicated and expensive imaging systems, and have difficulties to accurately measure in-plane displacements when the optical axis is not perpendicular to surface of the object (i.e., off-axis measurement). In this work, we develop a low-cost and portable smartphone-based optical method for accurately measuring off-axis structural displacements. The theoretical equations of the in-plane physical displacements on the object surface are derived based on the smartphone gyroscope data that can be used to determine the rotation matrix between the defined world coordinate system and the camera coordinate system. Simple calibration tests are performed to validate the accuracy of the smartphone gyroscope in detecting the rotation angles. The effectiveness and accuracy of this method in off-axis structural displacement measurement are then verified by two in-plane translation tests in laboratory condition. Finally, the noise from the smartphone camera is evaluated, and the effectiveness of the proposed method in continuous displacement measurement is further confirmed the vibration measurement of a hanging light under random wind load.

[1]  Maria Q. Feng,et al.  Experimental validation of cost-effective vision-based structural health monitoring , 2017 .

[2]  Hani Nassif,et al.  Comparison of laser Doppler vibrometer with contact sensors for monitoring bridge deflection and vibration , 2005 .

[3]  Zhengyou Zhang,et al.  A Flexible New Technique for Camera Calibration , 2000, IEEE Trans. Pattern Anal. Mach. Intell..

[4]  Peter Avitabile,et al.  Photogrammetry and optical methods in structural dynamics – A review , 2017 .

[5]  Anand Asundi,et al.  Two-dimensional digital image correlation for in-plane displacement and strain measurement: a review , 2009 .

[6]  Ran Tao,et al.  Accurate 3D Shape, Displacement and Deformation Measurement Using a Smartphone , 2019, Sensors.

[7]  Eric Maisel,et al.  Using vanishing points for camera calibration and coarse 3D reconstruction from a single image , 2000, The Visual Computer.

[8]  Bing Pan,et al.  Remote Bridge Deflection Measurement Using an Advanced Video Deflectometer and Actively Illuminated LED Targets , 2016, Sensors.

[9]  Hubert W. Schreier,et al.  Image Correlation for Shape, Motion and Deformation Measurements: Basic Concepts,Theory and Applications , 2009 .

[10]  M. A. Sutton,et al.  Accurate measurement of three-dimensional deformations in deformable and rigid bodies using computer vision , 1993 .

[11]  Farhad Ansari,et al.  Reference free method for real time monitoring of bridge deflections , 2015 .

[12]  Piervincenzo Rizzo,et al.  Non-Contact Smartphone-Based Monitoring of Thermally Stressed Structures , 2018, Sensors.

[13]  Bing Pan,et al.  Single-camera high-speed stereo-digital image correlation for full-field vibration measurement , 2017 .

[14]  Peter Avitabile,et al.  Large-area photogrammetry based testing of wind turbine blades , 2017 .

[15]  Maria Q. Feng,et al.  A Vision-Based Sensor for Noncontact Structural Displacement Measurement , 2015, Sensors.

[16]  Carlo Atzeni,et al.  Interferometric radar vs. accelerometer for dynamic monitoring of large structures: An experimental comparison , 2008 .

[17]  James M. W. Brownjohn,et al.  Review of machine-vision based methodologies for displacement measurement in civil structures , 2018 .

[18]  Lijun Wu,et al.  Dynamic testing of a laboratory model via vision-based sensing , 2014 .

[19]  Alan Dodson,et al.  Detecting bridge dynamics with GPS and triaxial accelerometers , 2007 .

[20]  Carlo Atzeni,et al.  High-speed CW step-frequency coherent radar for dynamic monitoring of civil engineering structures , 2004 .

[21]  Jean-José Orteu,et al.  3-D computer vision in experimental mechanics , 2007 .

[22]  Fanis Moschas,et al.  Measurement of the dynamic displacements and of the modal frequencies of a short-span pedestrian bridge using GPS and an accelerometer , 2011 .

[23]  Sinan Acikgoz,et al.  Sensing dynamic displacements in masonry rail bridges using 2D digital image correlation , 2018 .

[24]  Maria Q. Feng,et al.  Cost‐effective vision‐based system for monitoring dynamic response of civil engineering structures , 2010 .

[25]  Jae-Hong Min,et al.  Non-contact and Real-time Dynamic Displacement Monitoring using Smartphone Technologies , 2015 .

[26]  Rui Calçada,et al.  Non-contact measurement of the dynamic displacement of railway bridges using an advanced video-based system , 2014 .

[27]  Billie F. Spencer,et al.  Advances in Computer Vision-Based Civil Infrastructure Inspection and Monitoring , 2019, Engineering.

[28]  Bing Pan,et al.  Real-time, non-contact and targetless measurement of vertical deflection of bridges using off-axis digital image correlation , 2016 .

[29]  Sung-Han Sim,et al.  Computer Vision-Based Structural Displacement Measurement Robust to Light-Induced Image Degradation for In-Service Bridges , 2017, Sensors.

[30]  Carlo Atzeni,et al.  Static and dynamic testing of bridges through microwave interferometry , 2007 .

[31]  Hani Nassif,et al.  Bridge Displacement Estimates from Measured Acceleration Records , 2007 .

[32]  Adam Gąska,et al.  Development of a vision based deflection measurement system and its accuracy assessment , 2013 .

[33]  M. Gordan,et al.  Camera calibration using two or three vanishing points , 2012, 2012 Federated Conference on Computer Science and Information Systems (FedCSIS).

[34]  James M. W. Brownjohn,et al.  A non‐contact vision‐based system for multipoint displacement monitoring in a cable‐stayed footbridge , 2018 .

[35]  Bing Pan,et al.  In-plane displacement and strain measurements using a camera phone and digital image correlation , 2014 .

[36]  Hao Liu,et al.  Structural Displacement Monitoring Using Smartphone Camera and Digital Image Correlation , 2018, IEEE Sensors Journal.