The aerodynamic performance analysis and blade planform design of a coaxial rigid rotor in forward flight were carried out utilizing CFD solver CLORNS. Firstly, the forward flow field characteristics of the coaxial rotor were analyzed. Shock-induced separation occurs at the advancing side blade tip and severe reverse flow occurs at the retreating side blade root. Then, the influence of geometrical parameters of the coaxial rigid rotor on forward performance was investigated. Results show that swept-back tip could reduce the advancing side compressibility drag and elliptic shape of blade planform could optimize the airload distribution at high advance ratio flights. A kind of blade planform combining swept-back tapered tip and nonlinear chord distribution was optimized to improve the rotor efficiency for a given high-speed level flight based on geometric parameter studies. The optimized coaxial rotor increases lift-to-drag ratio by 30% under the design conditions.

The control stability and accuracy of quad tiltrotor UAVs is improved when encountering external disturbances during automatic flight by an active disturbance rejection control (ADRC) parameter self-tuning control strategy based on a radial basis function (RBF) neural network. Firstly, a nonlinear flight dynamics model of the quad tiltrotor UAV is established based on the approach of component-based mechanistic modeling. Secondly, the effects of internal uncertainties and external disturbances on the model are eliminated, whilst the online adaptive parameter tuning problem for the nonlinear active disturbance rejection controller is addressed. The superior nonlinear function approximation capability of the RBF neural network is then utilized by taking both the control inputs computed by the controller and the system outputs of the quad tiltrotor model as neural network inputs to implement adaptive parameter adjustments for the Extended State Observer (ESO) component responsible for disturbance estimation and the Nonlinear State Error Feedback (NLSEF) control law of the active disturbance rejection controller. Finally, an adaptive attitude control system for the quad tiltrotor UAV is constructed, centered on the ADRC-RBF controller. Subsequently, the efficacy of the attitude control system is validated through simulation, encompassing a range of flight conditions. The simulation results demonstrate that the Integral of Absolute Error (IAE) of the pitch angle response controlled by the ADRC-RBF controller is reduced to 37.4° in comparison to the ADRC controller in the absence of external disturbance in the full-states mode state of the quad tiltrotor UAV, and the oscillation amplitude of the pitch angle response controlled by the ADRC-RBF controller is generally reduced by approximately 50% in comparison to the ADRC controller in the presence of external disturbance. In comparison with the conventional ADRC controller, the proposed ADRC-RBF controller demonstrates superior performance with regard to anti-disturbance capability, adaptability, and tracking accuracy.

Based on the numerical calculation and analysis of the principle of the lift and thrust of the Fan-wing. A new scheme for the wing of Fan-wing aircraft-distributed jet blowing wing was presented. Firstly, the mechanism of the formation process of the vortex-induced lift and thrust force of the two kinds of wings was analyzed. Then, the numerical calculation method and validation example were verified. It was proved that the distributed jet blowing wing had the same vortex-induced lift and thrust mode as that of the Fan-wing by comparing the relative static pressure distribution curve, velocity contours, and pressure contours. Finally, the blow-up speed of a jet blowing wing was defined and the relationship between the lift and thrust of two wings with the flow speed and angle of attack was compared. The result indicated that the lift and thrust of the distributed jet blowing wing was similar to those of the Fan-wing under normal flight conditions. Therefore, it was proved that the Fan-wing can be replaced by the distributed jet blowing wing. Furthermore, distributed jet blowing wing technology has the potential value for application in an ultrashort take-off and landing concept aircraft.