L1 Adaptive Structure-Based Nonlinear Dynamic Inversion Control for Aircraft with Center of Gravity Variations

Due to the reliance on model knowledge and the lack of compensation mechanism, Nonlinear Dynamic Inversion (NDI) control does not provide the essential robustness in the face of disturbances such as the Center of Gravity (CG) sudden change. To overcome this deficiency, a novel adaptive NDI control approach based on the L1 adaptive structure, called L1 Adaptive Nonlinear Dynamic Inversion (L1-ANDI), is presented, which can guarantee the desired dynamic performance while overcoming the influence of disturbances and uncertainties. In particular, the introduction of a low-pass filter makes the L1-ANDI control realize the decoupling of fast adaptation and robustness. Furthermore, the effect of CG variations on the aircraft is analyzed from the aerodynamic perspective, and the L1-ANDI-based flight controller is designed to eliminate the influence of the CG variations. A series of simulation results demonstrate that the designed flight controller can achieve satisfactory performance and is robust to the disturbance of CG sudden variations.