Wind Resistant Transition Trajectory Generation of VTOL Aircraft under Control Allocation Framework

The vertical-takeoff-and-landing (VTOL) suffers from gusts and disturbances when switching between hovering and level flight. The drastic dynamic change may introduce low stability margins and cause instability. The transition trajectory plays a vital role in the process and thus needs to be optimized. In this work, a wind resistant transition trajectory generation method for VTOL aircraft is proposed. The transition trajectory generation exploits the control allocation framework and defines a unique control overflow region based on the trajectory and disturbance conditions. The wind resistance optimization is converted to a minimization of the modulated overflow region and thus is solvable in a conventional optimal control framework. A B-spline parameterization is also introduced to alleviate the computational load. The proposed transition trajectory generation methods have been verified in simulation with an ETS-20 VTOL aircraft model and Von Karman gust profile. Enhanced wind resistance is observed in comparison to other representative transition trajectories.