Three-dimensional mobile docking control method of an underactuated autonomous underwater vehicle

A three-dimensional mobile docking control method consisting of a docking position estimation method, a control strategy with a switched guidance algorithm, and an observer-based backstepping sliding mode controller is proposed to control an underactuated autonomous underwater vehicle (AUV) to complete a mobile docking mission. First, a five-degrees-of-freedom kinematics and dynamics model of an underactuated AUV is constructed. Using this model, reduced-order linear extended state observers are obtained and further used to estimate and compensate for the unknown disturbance. In addition, a docking position estimation method is developed to estimate the docking position roughly when a mobile docking station performs a uniform circular motion. Furthermore, a control strategy with a switched guidance algorithm is designed to avoid unreasonable behaviors of AUVs and reach the desired position. Finally, an observer-based backstepping sliding mode controller is designed to make an AUV complete mobile docking mission efficiently and reliably in the presence of unknown current disturbances. The proposed control system has been proven to be stable by employing the Lyapunov stability theory.