# Design and Control of an Ultra-Low-Cost Logistic Delivery Fixed-Wing UAV
## 2 Overall UAV Design
### Establishment Process of Aircraft Modeling  
In this study, SolidWorks software (solidworks2021) is used to conduct 3D modeling of the thrown fixed-wing UAV. The aircraft modeling process consists of the following  
\begin{table}
\begin{tabular}{c c c c} \hline \hline Wingspan/m & 1.50 & Maximum Takeoff Weight/kg & 2.0 \\ Ratio to the tip & 1.50 & Minimum takeoff speed m/s & 10 \\ Fuselage length/m & 0.655 & Maximum level-flight speed m/s & 30 \\ String span ratio & 6.87 & Battery life/h & 0.2 \\ Wing loads g/dm\({}^{3}\) & 65 & Practical ceiling/m & 100 \\ Thrust-to-weight ratio & 1.5 & Payload/kg & 0.5 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Main UAV design parameters.  
Figure 17: Three views of the fixed-wing throwing UAV.  
steps: The takeoff weight of the aircraft ranges between 1900 g and 2000 g, with a flight altitude of about 30 m and a flying speed of 15 m/s. The average chord length of the wing has been preliminarily determined to be 230 mm, resulting in a Reynolds number (Re) of 235,629. A twin-engine, single-wing design with an H-tail layout is adopted, and the areas of all the control surfaces are appropriately enlarged. The combination of the flight control and an airspeed meter with a motor differential speed is used to achieve better wind resistance. Additionally, based on flying experience, reconnaissance requires a lower cruising speed. An overly heavy payload can result in poor takeoff and landing performance; hence, a high-aspect-ratio trapezoidal wing is used to increase the wing area, reduce wing loading, and induce drag while maintaining favorable lift-to-drag ratio characteristics [52; 53]. Because of the low fuselage, a sponge pad is attached to the bottom of the fuselage during actual flights to increase the height and prevent the propeller blades from hitting the ground during landing. In terms of the power, to shorten mission times and provide power redundancy under strong wind conditions, the aircraft maximizes the thrust-to-weight ratio, sacrificing some endurance capabilities to achieve better climbing performance. Figure 18 shows a 3D assembly drawing of the drone.  
Meanwhile, in the establishment process of the aircraft modeling, a detailed system attribute analysis of the studied fixed-wing UAV is conducted, where crucial inertial and mass properties are precisely measured and recorded. The total mass of the UAV is 1606.66 g, equipped with a payload that has a clearly defined center of gravity, with \(X\), \(Y\), and \(Z\)-axis coordinates at 0.01 m, 0.29 m, and \(-\)589.15 m, respectively, reflecting its balanced design and mass distribution. The inertial matrix provides critical data about the UAV's inertial characteristics with respect to rotational motions; the principal moments of inertia are as follows: \(Ixx=\) 129,656,482.52 kg\(\cdot\)mm\({}^{2}\), \(Iyy=\) 170,053,044.53 kg\(\cdot\)mm\({}^{2}\), and \(Izz=\) 296,400,388.67 kg\(\cdot\)mm\({}^{2}\), highlighting the UAV's rotational stability along each axis. Additionally, the product of the inertia quantifies the interplay between the axes, such as \(Ixz=-\)29,702.20 kg\(\cdot\)mm\({}^{2}\), which is crucial for understanding the UAV's dynamic characteristics. Furthermore, the UAV design also considers additional inertial properties, such as \(Ixx=\) 853,973,205.56 kg\(\cdot\)mm\({}^{2}\) and \(Izz=\) 130,465,594 kg\(\cdot\)mm\({}^{2}\), to enhance its performance in various operational scenarios.  
Figure 18: Three-dimensional modeling of the fixed-wing delivery UAV.