Robust Trajectory Tracking of Quadrotor Using State Feedback Control Combined With Improved Active Disturbance Rejection Control

Robust trajectory tracking of quadrotors remains challenging due to nonlinear dynamics, cross-coupling among control channels, model uncertainties, and external disturbances. Disturbance observer-based control (DOBC) is a promising strategy for addressing these issues. In this work, a DOBC-based strategy is proposed, where an extended state feedback control (SFBC) scheme is combined with an improved active disturbance rejection control (IADRC) scheme, forming a hybrid dual-loop SFBC–IADRC architecture for robust quadrotor trajectory tracking. In this architecture, the IADRC is employed in the inner attitude loop, while the SFBC is used in the outer position loop. The SFBC is implemented by combining a state feedback (SFB) controller with a first-order sliding mode disturbance observer (FOSMDO). The FOSMDO is constructed by integrating a higher-order sliding mode (HOSM) observer and an extended state observer (ESO) to estimate complex-structured disturbances. The IADRC is developed by modifying the fal function in the conventional ADRC. A six-degree-of-freedom quadrotor dynamic model considering external disturbances is established using the Newton–Euler formulation. The SFBC is synthesized to ensure robust trajectory tracking in the presence of complex-structured disturbances. The IADRC is then developed to reduce jitter in the state estimates and control input caused by abrupt changes in the error gain at the transition points. Finally, the tracking performance and robustness of the proposed SFBC–IADRC scheme are validated through numerical simulations. The SFBC is further compared with ADRC-based and UDE-based methods under the same IADRC attitude loop.