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A Vision-Based Sensor for Noncontact Structural Displacement Measurement.

Feng D, Feng MQ, Ozer E, Fukuda Y - Sensors (Basel) (2015)

Bottom Line: An advanced template matching algorithm, referred to as the upsampled cross correlation, is adopted and further developed into a software package for real-time displacement extraction from video images.By simply adjusting the upsampling factor, better subpixel resolution can be easily achieved to improve the measurement accuracy.Then field tests are carried out on a railway bridge and a pedestrian bridge, through which the accuracy of the vision sensor in both time and frequency domains is further confirmed in realistic field environments.

View Article: PubMed Central - PubMed

Affiliation: Department of Civil Engineering and Engineering Mechanics, Columbia University, New York, NY 10027, USA. df2465@columbia.edu.

ABSTRACT
Conventional displacement sensors have limitations in practical applications. This paper develops a vision sensor system for remote measurement of structural displacements. An advanced template matching algorithm, referred to as the upsampled cross correlation, is adopted and further developed into a software package for real-time displacement extraction from video images. By simply adjusting the upsampling factor, better subpixel resolution can be easily achieved to improve the measurement accuracy. The performance of the vision sensor is first evaluated through a laboratory shaking table test of a frame structure, in which the displacements at all the floors are measured by using one camera to track either high-contrast artificial targets or low-contrast natural targets on the structural surface such as bolts and nuts. Satisfactory agreements are observed between the displacements measured by the single camera and those measured by high-performance laser displacement sensors. Then field tests are carried out on a railway bridge and a pedestrian bridge, through which the accuracy of the vision sensor in both time and frequency domains is further confirmed in realistic field environments. Significant advantages of the noncontact vision sensor include its low cost, ease of operation, and flexibility to extract structural displacement at any point from a single measurement.

No MeSH data available.


Field test: (a) Streicker Bridge; (b) Artificial target.
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sensors-15-16557-f014: Field test: (a) Streicker Bridge; (b) Artificial target.

Mentions: The Streicker Bridge is a pedestrian bridge located on the Princeton University campus, NJ, USA. The bridge has a main span and four approaching legs. The main span is a deck-stiffened arch and the legs are curved continuous girders supported by steel columns [33]. This field tests are to study the performance of the vision sensor in frequency domain. Two sets of dynamic loading tests are carried out on the third span of the southeast leg. As shown in Figure 14, one artificial target and one accelerometer (Model#W352C67 by PCB PIEZOTRONICS Inc.: Depew, NY, USA) are installed on the mid span. It is noted that the camera optical axis is tilted by an approximate angle of 15° with respect to the normal direction of the bridge surface, However, in this field test, due to the large height between ground and the bridge bottom surface, it is very difficult to install a reference LVDT to compare the accuracy of the measured displacement time histories by the vision sensor.


A Vision-Based Sensor for Noncontact Structural Displacement Measurement.

Feng D, Feng MQ, Ozer E, Fukuda Y - Sensors (Basel) (2015)

Field test: (a) Streicker Bridge; (b) Artificial target.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4541893&req=5

sensors-15-16557-f014: Field test: (a) Streicker Bridge; (b) Artificial target.
Mentions: The Streicker Bridge is a pedestrian bridge located on the Princeton University campus, NJ, USA. The bridge has a main span and four approaching legs. The main span is a deck-stiffened arch and the legs are curved continuous girders supported by steel columns [33]. This field tests are to study the performance of the vision sensor in frequency domain. Two sets of dynamic loading tests are carried out on the third span of the southeast leg. As shown in Figure 14, one artificial target and one accelerometer (Model#W352C67 by PCB PIEZOTRONICS Inc.: Depew, NY, USA) are installed on the mid span. It is noted that the camera optical axis is tilted by an approximate angle of 15° with respect to the normal direction of the bridge surface, However, in this field test, due to the large height between ground and the bridge bottom surface, it is very difficult to install a reference LVDT to compare the accuracy of the measured displacement time histories by the vision sensor.

Bottom Line: An advanced template matching algorithm, referred to as the upsampled cross correlation, is adopted and further developed into a software package for real-time displacement extraction from video images.By simply adjusting the upsampling factor, better subpixel resolution can be easily achieved to improve the measurement accuracy.Then field tests are carried out on a railway bridge and a pedestrian bridge, through which the accuracy of the vision sensor in both time and frequency domains is further confirmed in realistic field environments.

View Article: PubMed Central - PubMed

Affiliation: Department of Civil Engineering and Engineering Mechanics, Columbia University, New York, NY 10027, USA. df2465@columbia.edu.

ABSTRACT
Conventional displacement sensors have limitations in practical applications. This paper develops a vision sensor system for remote measurement of structural displacements. An advanced template matching algorithm, referred to as the upsampled cross correlation, is adopted and further developed into a software package for real-time displacement extraction from video images. By simply adjusting the upsampling factor, better subpixel resolution can be easily achieved to improve the measurement accuracy. The performance of the vision sensor is first evaluated through a laboratory shaking table test of a frame structure, in which the displacements at all the floors are measured by using one camera to track either high-contrast artificial targets or low-contrast natural targets on the structural surface such as bolts and nuts. Satisfactory agreements are observed between the displacements measured by the single camera and those measured by high-performance laser displacement sensors. Then field tests are carried out on a railway bridge and a pedestrian bridge, through which the accuracy of the vision sensor in both time and frequency domains is further confirmed in realistic field environments. Significant advantages of the noncontact vision sensor include its low cost, ease of operation, and flexibility to extract structural displacement at any point from a single measurement.

No MeSH data available.