Third-order fast finite-time extended state observer-based fault tolerant control for autonomous underwater vehicles with thruster saturation

In this paper, the fault-tolerant control problem is investigated for AUV with thruster faults and thruster saturation. A non-singular terminal sliding mode control method is developed based on a third-order fast finite time extended state observer (FFTESO). Firstly, the third-order FFTESO is introduced to estimate the generalized uncertainty, which includes current disturbance, dynamic model uncertainty, and thruster fault and saturation. Then, a non-singular terminal sliding mode-based fault tolerant control is presented by combining the estimation provided by the observer. And the Nussbaum-type function is applied to deal with the unknown gain caused by the thruster saturation. It is proved theoretically that the stability of the observer and the designed fault-tolerant controller can ensure the boundness of tracking errors. Finally, the effectiveness of the proposed control scheme is evaluated by simulation and comparison experiments on ODIN-AUV.