A hierarchical disturbance rejection depth tracking control of underactuated AUV with experimental verification

This paper presents a hierarchical disturbance rejection depth tracking control scheme for the underactuated autonomous underwater vehicle (AUV) with comparative experimental results. The proposed hierarchical control scheme is constructed by two layers in the kinematics and dynamics. First, the line-of-sight (LOS) guidance is adopted to transform the depth tracking problem of the underactuated AUV into the pitch tracking in the kinematics layer, and then the adaptive line-of-sight guidance (ALOS) is proposed to estimate online and compensate for the angle of attack neglected in the traditional LOS guidance or in the presence of disturbance. Second, in order to further enhance the capability of disturbance rejection, active disturbance rejection control (ADRC) is adopted to track the desired pitch angle in the dynamics layer. In addition, a modified velocity saturation tracking differentiator (VSTD) by considering the motion characteristics of the AUV is introduced to enable the easy tuning of the control parameters and the adaptability to varying conditions in practice. Finally, a small size underactuated AUV prototype named as ARMs-AUV 1.0 is used to implement the control algorithms. Comparative experimental results are illustrated to demonstrate the effectiveness and the remarkable performance of the proposed depth tracking control scheme.