## 2 UAV Dynamics Model
### Aerodynamic Model Considering the Influence of Distributed Slip Flow  
MY-UAV adopts a special takeoff and landing method similar to the Neder Drone [3], as shown in Figure 3, with a large stopping angle as the initial state. During the high-angle takeoff and landing process of unmanned aerial vehicles, the free flow velocity is close to zero, and the power demand is relatively high. Therefore, the induced speed of the propeller slipstream is much higher than the free flow velocity, and the aerodynamic force of the wing is mainly generated by the distributed-propeller slipstream. Therefore, the aerodynamic model of unmanned aerial vehicles during takeoff and landing must fully consider the influence of distributed-propeller slipstreams. (1) Average induced velocity test of propeller slipstreams  
In order to accurately obtain the average induced velocity of MY-UAV propeller slipstreams, this paper designed and conducted zero-inflow state propeller slipstream experiments. Due to the fact that the wing profile of the drone can change the incoming flow field and affect the local flow velocity, in order to measure the induced velocity of clean propeller slipstreams at different positions, the inorganic wing measurement method was chosen in this experiment. The experimental system is shown in Figure 4. Firstly, install the selected type of propeller on a fixed platform and connect the testing equipment to control the throttle size of the propeller, while reading information such as voltage, speed, and power. On the other side, install the airspeed tube on a movable platform, with the airspeed tube inlet channel parallel to the propeller shaft. By moving the platform, change the position of the airspeed tube inlet to perform speed measurements at different positions. Figure 3: Neder Drone takeoff from deck. According to reference [15], [PERSON] and [PERSON] developed and validated a propeller slipstream model for unmanned aerial vehicles in their research, considering the acceleration and diffusion in the propeller slipstream region. The slip velocity of the propeller is relatively small at the center of the propeller shaft. As the distance from the center of the propeller shaft increases, the slip velocity will first increase and then gradually decrease to zero. Considering experimental measurement errors, this article takes the slip velocity at the distance from the center of the propeller shaft as the maximum slip-induced velocity of the section and takes 75% of the maximum slip-induced velocity as the average slip-induced velocity of the section. Take 75% of the maximum induced slip velocity at the leading edge of the wing as the average induced slip velocity in the slip zone. After interpolation fitting, the variation law of the average induced slip velocity with throttle under zero flow is obtained. According to reference [15], as the flight speed of the drone increases, the influence of propeller induced slip velocity on the aft closing speed of the drone rotor gradually weakens. Therefore, it is necessary to revise the zero-inflow average induced slip velocity model established in the previous text to expand the application range of the model under different free inflow conditions. After correction, the change curve of the average induced velocity of slipstream with free flow velocity at 1 throttle amount is shown in Figure 5, and the variation curve of the average induced slip velocity with the throttle at different inflow velocities is shown in Figure 6.  
Figure 4: Propeller slip flow velocity test experiment. (2) Experimental study on the mutual influence of multiple propeller slipstreams  
To analyze the characteristics of the distributed power propellers affecting each other, two sets of propeller slipstream influence experiments were further designed, with velocity test points arranged along the wing span direction. The experimental system design is shown in Figure 7:  
Figure 5: Curve of average induced velocity of slipstream influenced by free flow.