Motion Mode Characteristics Analysis for Tilt-Rotor Aircraft Transition Path Planning

The tilt-rotor aircraft motion mode characteristics significantly change during transition flight. Current research on transitional flight control lacks a close connection with the mode characteristics in path planning and control law design, leading to a greater reliance on gain scheduling, increasing engineering complexity and effort. We first systematically analyze the variations and mechanisms of mode characteristics. Then, we propose leveraging the relatively stable mode and its minor, gradual characteristic changes to plan the transition path. We finally validate the efficacy of this method in reducing the requirements for gain scheduling. The results demonstrate that the transition to airplane mode significantly affects the damping ratios for the Dutch roll, pitch short-period, and phugoid modes, approximately 200%, 49%, and 65%, respectively. The amplitude ratio of roll motion and phase angle in Dutch roll and spiral modes significantly change, correlating with the nacelle angle. Key factors influencing these variations include the body angular velocities projected onto the rotor axis, the angle between the rotor disk and flight velocity, and the distance of the rotor hub from the center of gravity. Simulations indicate that, by selecting an appropriate path, it is possible to achieve control performance similar to that of control gain scheduling, even without gain scheduling.