Comparison of Control Methods for Trajectory Tracking in Fully Actuated Unmanned Aerial Vehicles

In this article, recently proposed control methods, suitable for trajectory tracking in fully actuated unmanned aerial vehicles (UAVs), are reviewed and experimentally compared. We specifically focus on multirotor platforms with tiltable propellers, for which the thrust and torque delivered by each rotor can be oriented within the aircraft frame using servo actuators. First, the main assumptions underlying the control design model usually employed in the literature are discussed, pointing out the main limitations. Then, some recent control laws that have been proposed to address the trajectory tracking problem for these platforms are reviewed, placing emphasis on their tracking capabilities as well as on the ease of tuning and implementation. Finally, experimental results obtained by applying three control laws on a tilt-arm quadrotor UAV are shown to evaluate and compare their performance. Two experiments, representative of operating conditions for thrust-vectoring UAVs, have been performed: a set-point tracking with level attitude and a full-pose trajectory tracking task.

I. Introduction

In recent years, the development of multirotor unmanned aerial vehicles (UAVs) with thrust vectoring capabilities has received a growing interest. These systems can achieve a larger degree of actuation compared with coplanar multirotor UAVs since both thrust and torque can be oriented within the airframe. This feature makes thrust-vectoring UAVs capable of performing complex full-pose maneuvers, which is particularly attractive for inspection-like applications that may require, for instance, navigation in a constrained environment. Moreover, being able to deliver both force and torque in any direction enhances the UAV interaction capabilities with the environment, which is especially desirable in aerial manipulation tasks.