Gaussian Process-Driven Incremental Flight Dynamics Control and Center of Gravity Adjustment for Tailsitter UAVs

This paper presents a center of gravity (CG) control strategy to enhance tailsitter transitions and maneuvers using a robust incremental nonlinear dynamic inversion (INDI) controller. Tailsitters, which use a flying wing configuration without tail surfaces, typically have lower pitching moments than conventional aircraft. By adjusting the CG during flight based on static stability analysis, the proposed method improves transition performance. Static stability generates restoring moments that can assist or hinder maneuvers. The CG adjustment controls the restoring pitching moment relative to the angle of attack, avoiding the need for additional actuators or motors found in other configurations like tilt-rotors, tilt-wings and other tailsitter variations. The INDI controller compensates for CG shifts using a feedforward term and time-delay approximation. Simulation results show improved trajectory tracking over fixed CG configurations, enabling more efficient transitions. This work extends the TIGPD INDI studies, with relative stability analysis confirming the TIGPD-INDI controller meets the gain and phase margin requirements of military specifications.