Finite-time adaptive tracking control of marine vehicles with complex unknowns and input saturation

In this paper, a finite-time adaptive tracking control (FATC) scheme based on nonsingular terminal sliding mode (NTSM) is proposed for trajectory tracking of a marine vehicle with complex unknowns and input saturation. First, a finite-time tracking differentiator (FTD) is designed to acquire the smooth position signal and its derivative. Besides, an adaptive assistant system is introduced to overcome the adverse effects caused by the nonlinear saturation factors. And then, the non-singular terminal sliding surface is constructed to achieve finite-time stability considering the position error and velocity error of the marine vehicle. Subsequently, to attenuate unknown uncertainties, the radial basis function neural network (RBFNN) is adopted to approximate the model uncertainties. Moreover, the adaptive law is introduced to estimate the boundary value of neural network approximation error and external disturbances. It can be proved that the proposed FATC scheme can make the trajectory tracking errors converge to a tiny neighborhood near zero in a finite time. Simulation studies and comprehensive comparisons based on a 76.2m supply vessel are exhaustively provided to confirm the effectiveness and superiority of the proposed FATC scheme.