Control of a class of thrust-propelled underactuated vehicles and application to a VTOL drone

A control approach for a class of underactuated vehicles with the objective of stabilizing reference trajectories either in velocity or position is proposed. The basic modeling assumption is that the vehicle is propulsed via a thrust force along a single body-fixed direction and that it has full torque actuation for attitude control (i.e. a typical actuation structure for aircrafts, vertical take-off and landing (VTOL) vehicles, submarines, etc.). Additional assumptions on the external forces applied to the vehicle are also introduced for the sake of control design and stability analyses. They are best satisfied for vehicles whose shape induces lift forces with limited amplitude and which are subjected to an external force field (e.g. gravity), as in the case of VTOL vehicles. The interactions of the vehicle with the surrounding fluid are often difficult to model precisely and they may significantly perturb its motion. Some novel nonlinear feedback control laws are proposed to compensate for modeling errors and perform robustly against such perturbations. Simulation results illustrating these properties on a realistic model of a VTOL vehicle are reported.