Dynamic attitude planning for trajectory tracking in underactuated VTOL UAVs

TL;DR

This paper presents a control scheme for underactuated VTOL UAVs prioritizing position tracking by using an attitude planner, effectively handling unmodeled dynamics and disturbances through simulations.

Contribution

It introduces an attitude planner as a dynamical system to ensure primary position tracking while managing attitude as a secondary objective.

Findings

Effective position tracking achieved in simulations.

Robustness to unmodeled dynamics and external disturbances.

Applicable to UAVs with different actuation mechanisms.

Abstract

This paper addresses the trajectory tracking control problem for underactuated VTOL UAVs. According to the different actuation mechanisms, the most common UAV platforms can achieve only a partial decoupling of attitude and position tasks. Since position tracking is of utmost importance for applications involving aerial vehicles, we propose a control scheme in which position tracking is the primary objective. To this end, this work introduces the concept of attitude planner, a dynamical system through which the desired attitude reference is processed to guarantee the satisfaction of the primary objective: the attitude tracking task is considered as a secondary objective which can be realized as long as the desired trajectory satisfies specific trackability conditions. Two numerical simulations are performed by applying the proposed control law to a hexacopter with and without tilted propellers, which accounts for unmodeled dynamics and external disturbances not included in the control design model.