Limits...
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.


Subpixel resolution evaluation (a) Resolution: ±1.338 mm; (b) Resolution: ±0.669 mm; (c) Resolution: ±0.268 mm; (d) Resolution: ±0.067 mm.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4541893&req=5

sensors-15-16557-f006: Subpixel resolution evaluation (a) Resolution: ±1.338 mm; (b) Resolution: ±0.669 mm; (c) Resolution: ±0.268 mm; (d) Resolution: ±0.067 mm.

Mentions: As shown in Figure 6a, for the integer-pixel resolution (1.338 mm), the displacement errors between the vision sensor and LDS can be observed clearly. On the other hand, after employing different levels of subpixel analysis, the displacement by the vision sensor agrees better with that by LDS as the resolution improves (with NRMSE errors (by Equation (8)) of 6.41%, 3.80%, 1.73%, and 1.35% respectively for the four zoom-in segments in Figure 6).


A Vision-Based Sensor for Noncontact Structural Displacement Measurement.

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

Subpixel resolution evaluation (a) Resolution: ±1.338 mm; (b) Resolution: ±0.669 mm; (c) Resolution: ±0.268 mm; (d) Resolution: ±0.067 mm.
© Copyright Policy
Related In: Results  -  Collection

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

sensors-15-16557-f006: Subpixel resolution evaluation (a) Resolution: ±1.338 mm; (b) Resolution: ±0.669 mm; (c) Resolution: ±0.268 mm; (d) Resolution: ±0.067 mm.
Mentions: As shown in Figure 6a, for the integer-pixel resolution (1.338 mm), the displacement errors between the vision sensor and LDS can be observed clearly. On the other hand, after employing different levels of subpixel analysis, the displacement by the vision sensor agrees better with that by LDS as the resolution improves (with NRMSE errors (by Equation (8)) of 6.41%, 3.80%, 1.73%, and 1.35% respectively for the four zoom-in segments in Figure 6).

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.