Extended state observer-based fast finite-time control for uncertain nonlinear systems with complexity avoidance

In this research, an extended state observer (ESO) based fast finite-time control problem for nonstrict-feedback system is considered. A novel tanh-type ESO is proposed to estimate the unknown nonlinearities, and a tanh-type fast finite-time filter is proposed to address the computational complexity issue. Through the utilisation of hyperbolic tangent function in ESO and proposed filter, the jitter phenomenon induced by the sign function is eliminated. The event-triggered mechanism based on relative threshold tactic is introduced to minimise communication bandwidth. By combining dynamic surface control (DSC) with the backstepping control technique, the strategy proposed in this article can make all the states in the considered system maintain bounded in finite time. Meanwhile, the tracking error and estimation errors of ESO converge to an interval near zero within the finite time. Finally, an intelligent ship autopilot model is introduced to attest the feasibility of the designed scheme.