## 6 Experimental Results  
An Intel D415 RGB/D camera was used to collect depth measurements, handled by the realsense2 Python package. The point cloud, colour and depth measurements have then been processed using Open3D Python software [20]. A Universal Robots UR10e platform was deployed, controlled through the Real-Time-Data-Exchange (RTDE) package and supplemented by the On-Robot HEX E/H QC force-torque sensor, integrated through UR-Cap software. The CUDA library was imported into the Python environment and handled the pre-processing of the paths. For online orientation corrections, three Panasonic HG-C 24V class II laser distance sensors relayed data to the external controller via an Arduino-uno at a power low enough to prevent surface ablations. Completed within a laboratory in direct proximity with a window, the the experiments show that the process is robust when exposed to a mixture of low and high intensity ambient lighting levels to be representative of site-inspection work. The robotic platform was statically mounted, with parts placed onto a table within the work-volume. A normal force of 50\(N\) was selected to maintain a high quality UT signal response, while also ensuring the CW probe is not damaged or split. To test the collision detection pre-planning approach, a large non-planar surface was chosen, representing a wing-section from an aerospace component. A highly reflective CFRP section was also chosen to demonstrate resilience to holed and noisy point cloud data. A small calibration plate was chosen to demonstrate the use of the Structural Similarity Index to the location of small surfaces. Finally, a smooth and rough (0.1 mm ridged) CFRP components were chosen to test the applicability of surface friction measurements, and a friction stir weld plate used to validate friction-coefficient imaging. The robot was capable of significant orientation and positional velocity control in the presence of a large curvature, as shown in Figure 4. In these experiments, the distance-metric used was not consistently monotonic in the case of inflection; however, the direction of motion was consistently correct. This agrees with the requirement made in Section4, as the surface inflects between points but the path taken passes local minima in the planar-distance parameter. Principle to the path planning process is the initial collision detection procedure to remove points that potentially damage the part or robot. The same wing as used in Figure 4 was placed at an angle relative to the robot that would cause a collision. The result is a successful removal of points that would potentially cause a collision, as shown in Figure 5.  
The ability to plan and scan over holed and noisy point cloud data is highlighted in Figure 6. Figure 6a shows the initial point cloud corrupted by light-interference. The resultant path executed by the robot is shown in Figure 6b, shown to cover the part despite the missing and noisy data. The images shown in Figure 7 demonstrates the structural similarity method of point-cloud selection prior to clustering and refinement. This is additionally resilient to variable lighting conditions, the main drawback of which is the potential for error when reflective regions are close to the surface of interest, resulting in artefacts seen in Figure 7c. The point cloud of the artefacts and the surface are then clustered, and the largest or closest to the camera is chosen, resulting in the surface alone being selected in Figure 7d. The operator should be aware of the placement of small parts so that the surface is not closer to reflective background regions than the clustering radius. Figure 4: Scanning of a mock-aerofoil sample. The original RGB/D data poorly represented the surface, with an offset of 5 mm. (**a**) Robotic-arm deployed to a mock aerofoil with large surface curvature. (**b**) Surface reconstructed using laser-data, waypoints from the RGB/D image embedded. Figure 5: Scanning of a mock-aerofoil sample. The original RGB/D data poorly represented the surface, with an offset of 5 mm.