Predefined-time sliding mode trajectory tracking control for asymmetric underactuated surface vehicle with nonlinear disturbances

In this paper, the predefined-time trajectory tracking problem of an asymmetric underactuated surface vehicle (AUSV) subject to external disturbances and model uncertainties is investigated. First, a new predefined-time disturbance observer (PTDO) is developed to estimate the compound disturbances accurately within a predefined time. Then, by employing coordinate transformations and cascaded system theory, the underactuation issue is addressed, and the tracking control problem of the AUSV is reformulated as a stabilization problem of two cascaded subsystems. Subsequently, two nonsingular predefined-time sliding mode control laws are designed for the two cascade subsystems. It is mathematically demonstrated that the tracking errors can converge in a predefined time. Meanwhile, the convergence time-bound is independent of the initial conditions of the system and can be predetermined within the physically allowable range as required. Finally, the simulation and experimental studies demonstrate the effectiveness of the proposed control scheme.