Adaptive robust sliding mode control of autonomous underwater glider with input constraints for persistent virtual mooring

Bottom-resting capability will enable an autonomous underwater glider (AUG) to perform long-duration virtual mooring. However, the tracking control of AUG soft landing on the seabed faces a number of challenges. It is crucial that the controller is able to incorporate many important factors, e.g., model uncertainty, environmental disturbances and limited dynamic range of actuators. This study first formulates the soft landing tracking control problem of AUG for persistent virtual mooring. An adaptive robust control scheme based on sliding mode control with a nonlinear disturbance observer is proposed that can effectively solve the challenges aroused by parametric uncertainty and unknown time-varying external disturbances. Moreover, the effect of input constraints of the AUG system is analyzed for the first time and is damped through a dynamic auxiliary compensator. Finally, simulation results demonstrate the superiority and inherent robustness of the proposed control scheme, in comparison with other techniques.