Design of super twisting disturbance observer based control for autonomous underwater vehicle

Autonomous underwater vehicles (AUVs) operates in uncertain oceanic environment with unknown external non-vanishing disturbances such as ocean currents. To handle such uncertainties, a super twisting algorithm as a disturbance observer based sliding mode controller (STA-SMC) is designed for trajectory tracking of a linearised steering and diving plane models of highly non-linear model of AUV. The efficacy of designed control scheme has been verified by comparing it with uncertainty and disturbance estimator (UDE) and disturbance observer (DO) based sliding mode control strategies. The extensive numerical simulations have been performed to demonstrate the robustness of the proposed scheme. It is found that the proposed STA-SMC scheme is not only effective in compensating the uncertainties in hydrodynamic parameters of the vehicle but also it rejects unpredictable disturbances due to fast and high magnitude underwater ocean currents. The stability of the designed observer based control scheme is provided by Lyapunov theory.