Multivariable Output Feedback Adaptive Terminal Sliding Mode Control for Underwater Vehicles

For the four degrees of freedom (4-DOF) trajectory tracking control problem of underwater vehicles in the presence of parametric uncertainties and external disturbances, a novel multivariable output feedback adaptive nonsingular terminal sliding mode control (ANTSMC) approach is proposed based on the equivalent output injection adaptive sliding mode observer (ASMO) and ANTSMC method. The ASMO is applied to reconstruct the full states in finite time and the ANTSMC method is designed to stabilize the trajectory tracking error to a small field in finite time. The proposed output feedback ANTSMC approach, using the adaptive technology, does not require the bound information of parametric uncertainties or external disturbances which successfully achieves the decrease of undesired chattering effectively. Corresponding stability analysis is presented. Comparative numerical simulation results are presented to validate the effectiveness of the proposed approach.