Cascaded Design for Finite-Time Trajectory Tracking Control of an Underactuated Surface Vehicle

This paper discusses the cascaded design for finitetime trajectory tracking control of an underactuated unmanned surface vehicle (USV). The tracking error dynamics is established with the guidance of a virtual reference vehicle, and transformed into a new cascaded structure, so the control of the overall system can be equivalent to stabilization of two interconnected subsystems separately, which can facilitate the control design by verifying the properties of the interconnection instead of iterative constructing Lyapunov functions for the whole system. The nonsingular fast terminal sliding mode (NFTSM) method is applied to stabilize the kinematic and dynamic subsystems in the present of model uncertainties, which can drive the states to the origin in finite time and avoid the possible singularity during the control phase. The stability of the cascaded system is guaranteed by verifying the satisfaction of the sufficient conditions. Numerical simulation results are provided to demonstrate the effectiveness of the proposed cascaded design.