Impact of Current Disturbances on AUV Docking: Model-Based Motion Prediction and Countering Approaches

Underwater docking enables autonomous underwater vehicles (AUVs) to operate independently of a surface vessel for extended periods. To perform the docking mission, special attention has to be paid to the navigation, guidance, and control issues of the vehicle, especially under current disturbances. Based on a full dynamic model of an AUV in currents, this paper studies the influences of current disturbances on AUV docking motion. A comprehensive docking scheme is introduced, which combines Kalman filter type navigation, guidance with current compensation, and proportional-integral-derivative (PID) controllers for both cross-track and heading control, to ensure successful docking operations. To counter the current effects, the proposed guidance algorithm applies current estimation and attitude compensation for motion correction online; in addition, an upstream control strategy in the case of strong current is also discussed. The proposed algorithms are initially validated through model-based numerical simulations, which provide effective guidance for the succeeding docking experiments conducted in a current generating pool. The feasibility and effectiveness of the countering approaches for AUV docking under current disturbances are demonstrated during the pool trials.