Event-triggered fixed-time tracking of state-constrained surface ships under actuation saturation with prescribed control performance

Abstract

This paper investigates the event-trigger-based fixed-time tracking control of a fully-actuated marine surface vehicle subject to full-state constraints, lumped disturbances, model uncertainties, and input saturation. The definition of the constrainedly practically fixed-time stability (CPFTS) is given first, and a sufficient condition for CPFTS is subsequently provided. To handle the input saturation, an auxiliary system is designed elaborately. Then applying the barrier Lyapunov function technology and blending an error transformation into backstepping scheme, the model-based adaptive controller and neural-network-based (NN-based) adaptive controller are proposed, respectively. Under these two controllers, the resulting closed-loop system signals are CPFTS and the settling time is not only independent of the system initial conditions but also assigned by users previously. Besides, it is proved that the tracking errors can converge to an arbitrarily small preset compact set within the preassigned time at a prescribed decay rate whilst all system states preserve the time-varying constraints.