Underwater Stability of a Morphable Aerial-Aquatic Quadrotor With Variable Thruster Angles

Abstract

The design of aerial-aquatic multirotors can benefit from thruster rotation so that the thrusters can act directly in the lateral directions of surge and sway when submerged. This allows much more effective locomotion underwater as opposed to the aerial configuration where rotational acceleration is used to direct small components of thrust in the lateral directions. However, the introduction of lateral thruster components by rotating the thrusters about their respective arm axes creates additional coupled moment terms. Here, the dynamics of this design is analysed to show that critical angles of thruster rotation can achieve stable surge and sway movements while also decoupling lateral from rotational movements.