Multi-point measurement using DIC based on UAV platform

Abstract

Displacement measurement method provides quantitative information for structural safety evaluation and maintenance purposes. To overcome the difficulties in the outdoor measurement of large-span bridges, a high-resolution camera on an unmanned aerial vehicle (UAV) was used to implement the deflect detection. First of all, the position of the UAV (including three displacements and three angles) was calibrated based on the speeded up robust features (SURF) algorithm. The SURF algorithm was used to extract the position information of the static areas in the image, and the calibration motion of the UAV was obtained by comparing the position changes of the static areas. The calibration used several self-designed marks with dots and circles to improve the accuracy. Then, the actual vibration of target was extracted from the raw data by subtracting the calibrated motion of the UAV. The numerical simulation indicates that the maximum error of displacement measurement can be controlled within 0.2 pixels. The calibrated experiments in the lab demonstrate that the overall correction accuracy of the displacement measurement is about 1.3 pixels. However, the maximum error of displacement measurement can be decreased to about 0.3 pixels if the rotation of UAV can be restrained by using damping mechanical devices.