Fixed-time observer-based heading control for underactuated hovercraft with slew rate safety constrain

Abstract

ABSTRACT This paper presents a safe-guaranteed backstepping sliding mode heading controller for the underactuated hovercraft in the presence of slew safety constraint and system uncertainties. To begin with, based on the four degrees-of-freedom mathematical model of the hovercraft with system uncertainties, a novel slew rate constraint scheme is proposed to constrain the virtual slew rate of the hovercraft by designing auxiliary dynamic function, and redefine the error constraint envelope according to the prescribed performance control idea to realise the slew rate error constraint. In addition, a second-order fixed time disturbance observer is designed to quickly estimate the uncertainties of the system. Finally, all tracking errors of the closed-loop system are verified global asymptotically stable. The simulation results show that the slew rate can be constrained within the set safety range, and the error signals can converge to 0.