Fractional Cascaded Non Linear ESO ADRC Control For a Quadrotor UAV

Quadrotor UAVs demand robust control strategies to handle inherent nonlinearities, model uncertainties, and external disturbances. While conventional PID control is widely used due to its simplicity, its performance degrades under dynamic perturbations and aggressive maneuvers. This paper presents an enhanced Active Disturbance Rejection Control (ADRC) framework for quadrotors, leveraging a fractional-order cascaded nonlinear Extended State Observer (ESO) to improve disturbance estimation and rejection. The proposed ESO combines fractional calculus for precise error dynamics tuning with a cascaded structure to decouple and compensate for multi-source disturbances (e.g., wind gusts, payload variations, and unmodeled dynamics). Comparative flight simulations demonstrate that the fractional cascaded nonlinear ESO-ADRC achieves superior trajectory tracking and disturbance rejection compared to the conventional linear ESO-ADRC, particularly under high-speed flight and sudden disturbances. The results validate the observer’s enhanced robustness and adaptability, offering a promising solution for autonomous quadrotor control in complex environments.