Anti-Disturbance Control for 6-DOF Quadrotor: A UC-FAS Approach

The precise control of 6-DOF quadrotors is often hindered by their underactuated nature and susceptibility to external disturbances. The unidirectionally connected fully actuated system (UC-FAS) framework offers a theoretical solution, yet the nominal approach remains fragile against uncertainties such as disturbances. To address the limitations, this work proposes an anti-disturbance control scheme that integrates the UC-FAS structure with an adaptive disturbance estimator. A key contribution of this study is the development of an optimized synthesis method for the Lyapunov matrix used in the adaptation laws. We formulate a convex optimization problem to determine the adaptation gains, explicitly balancing the convergence speed of the estimator against system robustness. Simulation results demonstrate that the proposed method reduces tracking errors compared to the nominal UC-FAS approach. Furthermore, the proposed optimization strategy effectively resolves the system divergence issues encountered when using standard unconstrained Lyapunov inequality, ensuring stable and accurate trajectory tracking.