Global trajectory tracking of VTOL UAV based on disturbance rejection control

In order to solve the trajectory tracking problem of the vertical take-off and landing unmanned aerial vehicles, the controller is proposed to make the system input-to-state stable with the consideration of model uncertainty and external disturbance. Firstly, with consideration of the dynamics of the servo system, the nonlinear error model is established completely by the modified Rodrigues parameters. Then, the hierarchical control method is used to design the translational and rotational controllers based on the time-scale property of the system, respectively. Thereafter, the disturbance observer which guarantees both the robust stability of the inner-loop and the disturbance rejection performance is designed. At last, the global stability of the closed-loop system is analyzed based on the singular perturbation theory. The global input-to-state stability of the system is obtained based on the Lyapunov stability theory. Simulation results show the effectiveness of the proposed method in this paper.