# Advanced Cooperative Formation Control in Variable-Sweep Wing UAVs via the MADDPG-VSC Algorithm
## 2 Dynamics Analysis of the Variable-Sweep Wing UAV
### Dynamic Characteristics Analysis of the L-30A UAV  
To comprehensively understand the aerodynamic characteristics of the L-30A variable-sweep wing UAV, the multi-rigid-body dynamics model established earlier is used to analyze the aerodynamic forces and moments experienced by the L-30A under various flight states, including takeoff, cruising, maneuvering, and diving. This analysis aims to provide a foundation for optimizing control strategies. Connection between the model and aerodynamic analysis  
The multi-rigid-body dynamics model enables precise calculations of the aerodynamic forces and moments acting on the L-30A UAV. These calculations are crucial for understanding the UAV's performance during different flight states and for determining the most effective control strategies to optimize performance. Detailed analysis of dynamic characteristics  
This study focuses on the L-30A variable-sweep wing UAV, an evolution of the L-30 fixed-wing UAV originally designed with a fixed \(6^{\circ}\) sweep angle. The L-30A introduces a critical rotating mechanism at the wing-fuselage junction, allowing for adjustment of the wing's sweep angle during flight, as shown in Figure 3. The key performance parameters of the L-30 series UAVs are compared in Table 1.  
Aerodynamic characteristics analysis  
The aerodynamic characteristics of the L-30A UAV were analyzed across various flight states, including takeoff, cruising, maneuvering, and diving. To ensure optimal performance, the sweep angle of the variable-sweep wing was restricted to \(16^{\circ}\) during maneuvering and \(60^{\circ}\) during diving. The aerodynamic forces and moments calculated using the multi-rigid-body dynamics model, as detailed in Table 2, are critical for understanding the UAV's behavior during these states. The geometric parameters of the L-30A UAV under these two sweep angles are summarized in Table 2. The table shows that at a 16\({}^{\circ}\) sweep angle, the wingspan is significantly larger and the chord length smaller, resulting in a longer longitudinal reference length. In contrast, at a 60\({}^{\circ}\) sweep angle, the wingspan is reduced, and the chord length is increased, which shortens the longitudinal reference length. These changes in geometry are crucial for adapting the UAV's aerodynamic performance to different flight states, particularly during high-speed maneuvers like diving. Figure 4 illustrates the relationships between the lift coefficient, drag coefficient, and angle of attack. The lift coefficient shows a quasi-linear relationship with the angle of attack, while the drag coefficient exhibits a quasi-conic relationship. The analysis demonstrates that the maximum lift-to-drag ratio increases with greater sweep angles, highlighting the L-30A UAV's ability to meet diverse aerodynamic requirements across different flight states, particularly during the diving phase, where the highly swept wings provide enhanced efficiency. (4) Comparative analysis of aerodynamic characteristics  
A comparative analysis was conducted between the fixed-wing L-30 UAV with a 6\({}^{\circ}\) sweep angle and the variable-sweep configurations of the L-30A UAV during the maneuvering and diving phases. This comparison highlights the advantages of the variable-sweep wing design over the fixed-wing model in terms of performance and adaptability. By integrating the multi-rigid-body dynamics model with the aerodynamic analysis, the control strategies for the L-30A UAV have been refined to optimize performance across \begin{table}
\begin{tabular}{l l l} \hline \hline
**Parameters** & **L-30A Variable-Sweep Wing UAV** & **L-30 Fixed-Wing UAV** \\ \hline Takeoff weight & 75 kg & 70 kg \\ Service ceiling & 6800 m & 7000 m \\ Velocity & 100–120 km/h (cruising) & 100–120 km/h (cruising) \\  & 180 km/h (maximum) & 150 km/h (maximum) \\ Endurance & 4.8 h & 5 h \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Flight performance parameters of L-30 series UAVs. Figure 3: Rotating mechanism at the wing–fuselage junction of the L-30A UAV.