3D path tracking of underactuated AUVs with general form of dynamics

This paper proposes a 3D path tracking method for a class of torpedo-type AUVs (autonomous underwater vehicles) with general form of dynamics. For this kind of AUV, there are only three control inputs are available for its 6DOF 3D motion, and therefore it´s a typical underactuated system. First, we introduce certain two spherical coordinate transformations so as to transform the vehicle model into three-inputs-three-outputs second-order strict-feedback form. To avoid possible singularity problem in the recursive control design, an asymptotic modification of orientation concept is introduced. Proposed tracking scheme can guarantee the asymptotic stability of closed-loop system in the spherical coordinate frames.