Robust trajectory tracking for underactuated VTOL aerial vehicles: Extended for adaptive disturbance compensation

This work proposes a feedback control strategy to let the dynamics of an under-actuated Vertical Take-Off and Landing (VTOL) aerial vehicle to track a desired trajectory thanks to an adaptive robust compensation of the aerodynamic disturbances. The novelty of the proposed approach consists in employing an aerodynamic disturbance observer derived using the NonLinear Geometric Approach and Radial Basis Functions (RBF). The obtained estimation is directly employed by a nonlinear robust feedback law which relies on a cascade control paradigm in which the attitude dynamics and the position dynamics of the vehicle play the role of the inner and of the outer loop, respectively. The robustness of the proposed approach is also demonstrated by means of simulation results in which the aerodynamic model of a multi-propeller aircraft is considered.