## 3 Overall Design of Bionic Multi-Section Variable-Sweep Wing UAV
### Coordinated Wing Deformation Scheme Based on the Centroid Self-Trim Compensation  
According to the distribution of wing ribs along the span direction, and considering the load-bearing capacity and the space required for wing deformation, pre-selected models of multi-section variable-sweep wings are established. After preliminary screening, the rib numbers at the boundary of the inner and outer wing sections of the pre-selected model are determined to be 12, 13, 14, 15, and 16, respectively. The five pre-selected models are named Model1, Model2, Model3, Model4, and Model5, respectively. The configurations with the sweep angle of the inner section \(\Lambda_{\text{in}}=0^{\circ}\) and the outer section \(\Lambda_{\text{out}}=30^{\circ}\) of the pre-selected models are shown in Figure 5. The mass and dimensions of the inner and outer sections of each pre-selected model are listed in Table 4.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**No**} & \multicolumn{1}{c}{**Spanwise**} & \multicolumn{1}{c}{**Chord**} & \multirow{2}{*}{**No**} & \multicolumn{1}{c}{**Spanwise**} & \multicolumn{1}{c}{**Chord**} \\  & **Position/m** & **Length/m** & & & **Position/m** & **Length/m** \\ \hline
1 & 0.434 & 1.741 & 11 & 5.053 & 1.588 \\
2 & 0.834 & 1.700 & 12 & 5.626 & 1.588 \\
3 & 1.243 & 1.658 & 13 & 6.199 & 1.588 \\
4 & 1.652 & 1.615 & 14 & 6.645 & 1.588 \\
5 & 1.911 & 1.588 & 15 & 7.091 & 1.588 \\
6 & 2.360 & 1.588 & 16 & 7.537 & 1.588 \\
7 & 2.859 & 1.588 & 17 & 8.153 & 1.588 \\
8 & 3.358 & 1.588 & 18 & 8.769 & 1.588 \\
9 & 3.908 & 1.588 & 19 & 9.384 & 1.588 \\
10 & 4.480 & 1.588 & 20 & 10.000 & 1.588 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Positions and dimensions of wing ribs.  
Figure 4: Shape and structure of multi-section variable-sweep wing. The gray part is the weapon section, and the purple part is the deformable section.  
Figure 6 shows the schematic diagram of the deformation process of the wing deformation mode for the multi-section variable-sweep wing UAV based on the centroid self-trim compensation, in which the sweep angle of the inner section \(\Lambda_{\text{in}}\) gradually increases from 0\({}^{\circ}\), while the sweep angle of the outer section \(\Lambda_{\text{out}}\) decreases to 0\({}^{\circ}\).  
Equation (7) lists the fitting functions of the sweep angle change in each wing section of the pre-selected models based on the centroid self-trim compensation.  
\[\begin{array}{l}y_{\text{Model1}}=0.003635x^{2}-0.8632x+22.61\\ y_{\text{Model2}}=0.00133x^{2}-0.405x+10.93\\ y_{\text{Model3}}=0.0009565x^{2}-0.3035x+8.214\\ y_{\text{Model4}}=0.0005743x^{2}-0.1917x+5.222\\ y_{\text{Model5}}=0.0003501x^{2}-0.1184x+3.229\end{array} \tag{7}\]  
where \(x\) is the sweep angle of the outer section, and \(y\) is the sweep angle of the inner section. The unit is in degrees (\({}^{\circ}\)).  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Model**} & **Mass of Inner** & **Mass of Outer** & **Wingspan of** & **Wingspan of Outer** \\  & **Section/kg** & **Section/kg** & **Inner Section/m** & **Section/m** \\ \hline Model1 & 132.21 & 89.99 & 3.72 & 4.37 \\ Model2 & 154.66 & 67.55 & 4.29 & 3.80 \\ Model3 & 158.43 & 63.77 & 4.73 & 3.39 \\ Model4 & 168.88 & 53.33 & 5.18 & 2.91 \\ Model5 & 178.65 & 43.55 & 5.63 & 2.46 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Mass and dimensions of the inner and outer sections of the pre-selected models.  
Figure 5: Schematic diagram of the dimensions of the inner and outer sections corresponding to the pre-selected models. The sweep angle of the inner section \(\Lambda_{\text{in}}=0^{\circ}\) and outer section \(\Lambda_{\text{out}}=30^{\circ}\).  
Figure 6: Schematic diagram of the wing deformation mode for multi-section variable-sweep wing UAV based on the centroid self-trim compensation, in which the sweep angle of the inner section gradually increases from 0\({}^{\circ}\) while the sweep angle of the outer section decreases to 0\({}^{\circ}\).