Robust Global Trajectory Tracking for Underactuated VTOL Aerial Vehicles Using Inner-Outer Loop Control Paradigms

This paper proposes a feedback control strategy to let the dynamics of a class of under-actuated vertical take-off and landing (VTOL) aerial vehicle tracking a desired position and attitude trajectory globally with respect to the initial conditions. The proposed feedback controller is derived following an inner-outer loop control paradigm, namely by considering the attitude, which is governed by means of a hybrid controller so as to overcome the well-known topological constraints, serving as a virtual input to stabilize the aircraft position. Two different approaches, the first one obtained by assuming perfect knowledge of the vehicle dynamics and the second one obtained by considering uncertainties and exogenous disturbances, are proposed and compared by analyzing the interconnection between the hybrid attitude and the continuous-time position closed-loop subsystems. The effectiveness of the obtained results is demonstrated by means of simulations and experiments using a miniature quadrotor prototype.