Finite-time active disturbance rejection control scheme for quadrotor attitude tracking.

In this paper, a finite-time active disturbance rejection control (FADRC) framework for quadrotor attitude tracking is presented. The FADRC framework is developed for two cascaded loops (inner-loop and outer-loop) to control the attitude angle and angular velocity, respectively. Two nonlinear extended state observers (NESOs) are devised to actively estimate and compensate for total disturbances, including internal uncertainties and external disturbances. A novel tracking differentiator (TD) is introduced to generate smooth angular speed information, featuring a simpler configuration and only one adjustable parameter, thus enhancing practical applicability. Additionally, a nonlinear control law is formulated to resist disturbances. For the outer-loop, a finite-time controller is designed to significantly enhance the tracking speed and mitigate the effects of tracking errors by ensuring convergence in a finite time, thereby improving the overall system response and robustness. The inner-loop nonlinear controller ensures rapid angular velocity tracking and stable output torques. The convergence of the TD and NESO, as well as the stability of the dual-loop controllers, are rigorously proven using Lyapunov methods. Simulation and experimental results demonstrate that the proposed control scheme achieves precise tracking performance with faster response speed, smaller tracking error, and better disturbance rejection performance compared to the existing methods.