## 3 Influence Factors of the UAV-LDV System
### Wind Speed  
Controlling the attitude and stability of UAVs in windy conditions has been a significant technical challenge [58]. The UAV-LDV system is designed to inspect curtain walls, which requires long-term operation at high altitudes, making it subject to wind interference. This section conducts a wind resistance test to investigate the impact of wind speed on the system's performance.  
The tests of the first-order natural frequency are conducted for Condition 3 in Section 3.4 under the influence of wind speed. This condition is primarily selected due to the shorter damaged length and the fact that most of the structural adhesive is still in use. The glass panel will perform better in high winds during this time, while the wind speed mainly affects the performance of the UAV-LDV system. If there were significant errors in the results under this condition, the conditions of greater severity of damage would have larger errors. The measuring points were arranged and the distances were measured in accordance with the provisions of Section 3.4 (1 m). The working UAV-LDV system was subjected to lateral wind at three different speeds: 1.5 m/s, 3.0 m/s, and 5.0 m/s (produced by an electric fan). Figure 13 shows the arrangement of the tests. Photos of the tests in the wind are shown in Figure 14.  
Table 6 presents the average first-order natural frequencies obtained from the nine measuring points. The results indicate that the wind speed has a significant impact on the reliability of the UAV-LDV system. Therefore, it is recommended to acquire the first-order natural frequency with this system in a windless environment or use an error correction algorithm to minimize the effect of wind speed on accuracy.  
Figure 14: Testing photographs in the wind. (**a**) 1 m ranging fixed test in the wind. (**b**) 1 m ranging mobile test in the wind.  
Figure 13: Test site setup.  
The study verifies the effectiveness of the UAV-LDV system in identifying debonding damage to the HFSCGCW under the influence of wind. Figure 15 validates the results of different wind speeds through numerical simulation and fixed tests. The assessment chart can give a general indication of the locations of damaged structural adhesives, but it is not very effective in pinpointing the exact location. When the wind speed reaches 5.0 m/s, it is difficult to provide useful information about the damaged side. The results indicate that the wind greatly affects the detection capability of the UAV-LDV system. The SSD indicator has a large numerical error in windy conditions and does not clearly indicate the exact location of the damage, even in the case of lighter damage. During the test, high winds interfered with the hovering and stabilization of the UAV. Even aligning the measuring points was difficult at times. To maintain alignment in strong winds, the drone continuously maneuvers through turns and side shifts. In contrast to the drone's camera, which is stabilized by a gimbal, the LDV is fixed directly to the fuselage. This configuration leads to the laser beam deviating from the target as the orientation of the fuselage changes, and passing through transparent glass. Consequently, the laser intensity that reflects the LDV is insufficient for stable data acquisition, resulting in failed assessments. As demonstrated in Figure 15, at a wind speed of 5 m/s, the processed results suggest extensive and severe debonding damage along both boundaries, even when the actual damage is minor. This contradicts the actual conditions. In subsequent research, it is recommended that a gimbal structure be developed to stabilize the LDV device, in order to minimize the errors in optical path differences caused by attitude adjustments. This approach is simpler and more efficient than developing complex algorithms. As a result, it is not recommended to perform tests in windy weather now.