86 A. Khadka et al. 9.2 Methodology In this paper, a non-destructive technique is proposed to monitor rotating wind turbines using digital image correlation. The proposed approach uses a drone with eight motors and propellers. An experiment was performed on a small-scale wind turbine (see Fig. 9.1) to show the merit of the approach. Figure 9.1 shows the wind turbine that is used for this measurement. The test structure is a six-bladed wind turbine with 113 cm blade diameter and 154 cm hub height. For measurement using DIC, the area of the test structure must be prepared before the measurement by applying a high contrast speckle pattern on the structure. This system is also capable of point tracking, in which the 3D coordinates of optical targets mounted to the structure are extracted during deformation. The principal aim of the project was remote structural health monitoring. A pair of high-speed cameras was desired to be mounted in an unmanned aerial vehicle. For this project, a UAV was used with eight propellers and eight motors that is controlled by 9-channel remote. Figure 9.2 depicts the drone with the stereo camera installed on it for DIC measurements of wind turbine blades. Moreover, for better flight and stability, this drone is equipped with a GPS. Fig. 9.1 A six-bladed wind turbine that was used for measurement Fig. 9.2 Flight control electronics and view screen
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