Abstract. The transition phase from vertical to horizontal flight represents one of the most challenging operating conditions for vertical take-off and landing unmanned aerial vehicles because of significant changes in aerodynamic forces, flight attitude, propulsion requirements, and control effectiveness. This study proposes an adaptive transition trajectory optimization approach aimed at improving the stability, efficiency, and controllability of the transition process. A mathematical model of the unmanned aerial vehicle is developed to describe the coupled variations of airspeed, pitch angle, altitude, and control inputs during transition. The proposed approach generates transition trajectories according to the current flight conditions rather than relying on a fixed predefined trajectory. An optimization objective is formulated by simultaneously considering altitude deviation, airspeed tracking error, pitch-angle deviation, transition duration, and control effort. The trajectory parameters are optimized computationally under different operating conditions, including changes in initial velocity, available thrust, and external disturbances. Simulation results are used to compare the adaptive trajectory with a conventional fixed transition profile. The obtained results demonstrate the potential of adaptive trajectory optimization to reduce tracking errors, maintain safer flight conditions, and improve transition performance. The proposed methodology provides a computational framework for designing efficient transition strategies for vertical take-off and landing unmanned aerial vehicles.

Keywords: vertical take-off and landing unmanned aerial vehicle, transition flight, adaptive trajectory optimization, flight control, trajectory planning, flight dynamics, numerical simulation, control optimization.