Transition Strategy Optimization of Tilt-Rotor VTOL UAV in Conversion Process

In this study, the flight quality of the transition process for a classic type of tilt-rotor vertical take-off and landing unmanned aerial vehicle (VTOL UAV) was improved by optimizing the transition process of this type of UAV. The optimization process is as follows: (i) the nonlinear dynamic models of aircraft were established. (ii) the tilting path of the tilt-rotor aircraft was designed by the optimal method. In order to minimize the attitude change, control energy consumption, and transition time of the aircraft during the transition process, a novel optimization cost function was built as objective for transition time, pitch angle change, and the control surface deflection minimization. The tilting strategy of the transition process was proposed based on the Gaussian pseudo spectral method. (iii) A weighted pseudo-inverse method based on niche genetic algorithm was used to design the manipulation strategy with the goal of the highest control efficiency and the smoothest transition, solving the problem of control redundancy caused by mode conversion and the lack of yaw control capability during the early stage of conversion. The simulation results show that compared to the traditional transition strategy, the novel tilting trajectory designed in this study brings better transition qualities, and the new control allocation law increases the aircraft yaw control capability, which in turn enhances the stability and anti-interference ability of the UAV in the transition mode.