Composite Control Based on Additive Decomposition for Disturbed Quadrotor UAV Attitude Systems

This paper proposes a composite control strategy based on additive decomposition for the attitude control system of a quadrotor UAV with modeling uncertainties and external disturbances. The original system, including external disturbances and uncertainties, is decomposed into a primary system with nominal dynamics and a secondary system accounting for the total disturbances, thereby simplifying the analysis and design process of the complex system. This decomposition transforms the coupled trajectory tracking and disturbance rejection problem into two independent subproblems: trajectory tracking control and disturbance rejection control. For the primary system, which is deterministic, a backstepping controller is designed to achieve trajectory tracking. For the secondary system, a non-singular fast terminal sliding mode control, enhanced by a compensation function observer (CFO), is proposed to handle external disturbances and uncertainties. The CFO offers precise disturbance estimation, significantly enhancing system robustness while effectively suppressing chattering in the sliding mode control. Simulation results demonstrate the effectiveness and superiority of the proposed method.