In the design of electric vertical takeoff and landing (eVTOL) vehicles, coaxial rotors have garnered significant attention due to their superior space usage and aerodynamic efficiency compared to standard rotors. However, it is challenging to study the flow field near the rotors due to the blade–vortex interface (BVI) and vortex–vortex contact between two rotors. Using sliding mesh technology and Reynolds-averaged Navier–Stokes (RANS) solvers, a numerical method was established to simulate the flow field of a coaxial rotor in hover, which was verified by experiments. Using this method, this paper analyzes the relationship between position and intensity of the tip vortex of the upper rotor, the axial velocity of induced flow and the load distribution on the blades at the azimuth when the BVI phenomenon occurs with a difference in rotational speed and rotor spacing. The results indicate that, when the BVI phenomenon appears, the blade-tip vortex of the top rotor rapidly dissipates, and the load distribution of the lower blade changes due to the induced flow of the vortex. When the rotational speed increases, the spanwise thrust coefficient of each rotor changes slightly. The vortex–vortex interaction becomes stronger, which leads to vortex pairing. When the distance between the rotors decreases, the BVI phenomenon occurs at an earlier azimuth and the location of the BVI moves towards the tip of the lower blade. The vortex–vortex interaction is also enhanced, which leads to vortex pairing and vortex merging.

Fixed-wing aircraft with vertical takeoff and landing capabilities need a lower speed and a higher lift during transition. To meet these needs, a tandem-channel wing layout has been developed, including a FLR (front wing lower than rear wing) configuration and a FUR (front wing upper than rear wing) configuration, which differ in height differences between the front and rear wings. Numerical simulations have been performed to investigate the aerodynamic characteristics of the two configurations. The results show that a significant increase in lift coefficient occurs when the propeller rotational speed and the angle of attack increase. The lift at a small angle of attack increases by more than 50% at a high propeller rotational speed, and the stall angle of attack increases by more than 10 degrees. For the FLR configuration, the downwash effect of the front wing impacts the rear wing, decreasing the local angle of attack and delaying airflow separation on the top surface. For the FUR configuration, the up surface of the rear wing is induced by the wake flow of the front wing propeller at a high propeller rotational speed, which increases the lift and the stall angle of attack but makes the aircraft have static instability.

Channel wing is a propeller-coupling layout that has good low-speed performance and S/VTOL potential. Focused on the application of this layout at the S/VTOL stage, this paper attempts to find the interaction mechanism for the distributed propeller channel wing. Firstly, the computation method based on RANS equations for propeller–wing integration was established with Momentum Source Method, which was compared with the unsteady Sliding Mesh method and validated by a ducted propeller. Secondly, the performances and aerodynamic characteristics of the single-propeller channel wings with two different airfoils were analyzed, and a ground test for the scaled model was conducted. Finally, a four-propeller channel wing was analyzed and compared with single-propeller channel wing, then the flow field characteristics were discussed in depth. The study shows that the airfoil shape will strongly affect the lift of channel wing at S/VTOL stage. Multi-propeller channel wing analysis indicates that rotational direction plays an important role in outside propeller interaction, where outboard-up rotation increases outside channel lift. In addition, the propeller wake also shows special distortion and dissipation behaviors, which are strongly affected by adjacent propellers.

One of the most essential approaches to expanding the capabilities of autonomous systems is through collaborative operation. A separated lift and thrust vertical takeoff and landing mother unmanned aerial vehicle (UAV) and a quadrotor child UAV are used in this study for an autonomous recovery mission in an aerial child–mother unmanned system. We investigate the model predictive control (MPC) trajectory generator and the nonlinear trajectory tracking controller to solve the landing trajectory planning and high-speed trajectory tracking control problems of the child UAV in autonomous recovery missions. On this basis, the estimation of the mother UAV movement state is introduced and the autonomous recovery control framework is formed. The suggested control system framework in this research is validated using software-in-the-loop simulation. The simulation results show that the framework can not only direct the child UAV to complete the autonomous recovery while the mother UAV is hovering but also keep the child UAV tracking the recovery platform at a speed of at least 11 m/s while also guiding the child UAV to a safe landing.

Electric-powered disposable unmanned aerial vehicles (UAVs) have wide applications due to their advantages in terms of long time flight and load capacity. Thus, improving their endurance has become an important task to enhance the performance of these UAVs. To achieve this, we investigated a battery dumping strategy which splits the battery into several packs that are used and dumped in sequence to reduce the dead weight. The Peukert effect is also considered. In this paper, the sensitivity analysis method was employed to analyse the endurance benefits for different battery weight ratios, Peukert constants and capacities, quantitatively. The results show that the endurance benefits are significantly affected by all three parameters. For ideal batteries, the endurance can be improved by 20% and 28% respectively when employing a double-pack or triple-pack battery strategy (for a battery weight ratio of 0.4), but these benefits will fall rapidly if the Peukert constant exceeds 1.0 or the battery weight declines. Besides, the endurance will be 10% longer if the lift coefficient rather than the velocity remains constant after the battery packs are dumped at a Peukert constant of 1.2.

To achieve underactuated control, a novel swashplateless rotor configuration of asymmetric inclined hinges which can be driven by periodic sinusoidal torque is studied, hopefully eliminating the conventional swashplate mechanism and multiple actuators. Therefore, the traditional mechanism can be intelligently replaced by software. However, high-frequency torque variation will invariably result in vibration noise and energy loss.Thus it is critical to properly design the swashplateless rotor in order to achieve a control process with less torque variation. As a result, in both numerical simulation and experiments, we performed sensitivity analyses on related design parameters such as hinge eccentricity, hinge inclined angle, and wingtip hammer position. The parameter effect on swashplateless rotor control was discovered through the analyses, and the basic law of its design was obtained.