# Experimental Validation and Evaluation of a Coupled Twist-Camber Morphing Wing Concept
## 3 Ground Testing
### Comparison of Deformed Shapes  
The deformed shapes were experimentally quantified using video of the wing under actuation from four different locations around the same axis: Two positions to determine the shape of the lower surface and two positions to determine the shape of the upper surface. A set of wing sections along the span were discretized using yellow sticker dots placed chordwise in each section, as shown in Figure 7.  
Tracking software [27] allowed tracking the position of the yellow sticker dots depicted in Figure 7 in a 2D plane parallel to the camera lenses while the wing is actuated. If a second set of footage was taken by rotating the camera around an axis parallel to the wing's unswept leading edge, the third coordinate could be calculated from the two sets of 2D positions tracked with the two different camera positions, given that the rotation angle and axis were known as explained earlier. Scaling factors needed to be applied to account for the differences in depth from the sticker dots to the camera when the camera is not parallel to the wing surface.  
Figure 8 depicts the experimental apparatus.  
Given the position in a 3D reference frame of the points of different airfoil sections along the chord and span were obtained, twist and camber for each of the sections could be obtained.  
Figure 7: Wing sections discretized along the wingspan using sticker dots.  
The wing was actuated and its shapes were measured for six main actuation configurations. For each main configuration, other configurations were measured corresponding to the full actuation configurations during roll maneuvers, acting as described earlier. If the main configuration was at an extreme of the actuation range, i.e., uncambered or fully cambered in all stations, only the other available full actuation configuration for rolling was measured. If the main configuration was between extremes, two other configurations were measured corresponding to uncambered and fully cambered roll configurations. Table 1 describes the actuation of each servo for the measured configurations in percentage of throw.  
Figures 9 and 10 depict the measured twist and camber distributions along the half span of the wing for the different configurations in Table 1, respectively. The expected trends were verified, with the magnitude of the negative tip twist being increased as the root camber increases and the tip twist variation being positive as the camber increased at or towards the tip. Nevertheless, the discretization and accuracy of the measurements did not allow the verification of a continuous twist and camber variation along the span, which  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Config. \#** & **Root Act. (\%)** & **Kink (\%)** & **Tip (\%)** \\ \hline
1 & 0 & 0 & 0 \\
1.1 & 0 & 100 & 100 \\
2 & 17 & 17 & 17 \\
2.1 & 17 & 100 & 100 \\
2.2 & 17 & 0 & 0 \\
3 & 33 & 33 & 33  
were therefore approximated by least-squares fit of cubic polynomial curves. These fitting curves were subsequently used for the estimation of roll rates, RBMs, and L/D values.  
Figure 9: Spanwise twist for the selected configurations.