Path-following control of an AUV in cascade under input saturation

This paper studies the problem of spatial path-following control of underactuated autonomous underwater vehicles (AUVs) with multiple uncertainties and input saturation taken into account. Initially, the reduced-order extended state observes (ESOs) is introduced to estimate and compensate all humped uncertainties due to the model parameters perturbations, unmodeled dynamics, environmental disturbances and nonlinear hydrodynamic damping terms. Furthermore, the spatial path-following control strategy is established by combining with backstepping, integral sliding mode control and estimator to cope with the position, attitude and linear velocity tracking of the AUV. Specifically, the dynamic surface control (DSC) technique is utilized to achieve satisfactory differential performance and avoid “explosion of complexity”. Additionally, the auxiliary dynamic compensator is presented to analyze the effect of input saturation, and states of the auxiliary design system are used to develop the controller. It is easily proved that the proposed control scheme can guarantee that all signals of the closed-loop system are globally stable through the Lyapunov theorem, with the tracking errors converging to an arbitrarily small neighborhood of zero. Finally, numerical simulation results are carried out to illustrate the effectiveness the proposed controller.