Event-triggered model-free adaptive control for a class of surface vessels with time-delay and external disturbance via state observer

This paper provides an improved model-free adaptive control (IMFAC) strategy for solving the surface vessel trajectory tracking issue with time delay and restricted disturbance. Firstly, the original nonlinear time-delay system is transformed into a structure consisting of an unknown residual term and a parameter term with control inputs using a local compact form dynamic linearization (local-CFDL). To take advantage of the resulting structure, use a discrete-time extended state observer (DESO) to estimate the unknown residual factor. Then, according to the study, the inclusion of a time delay has no effect on the linearization structure, and an improved control approach is provided, in which DESO is used to adjust for uncertainties. Furthermore, a DESO-based event-triggered model-free adaptive control (ET-DESO-MFAC) is established by designing event-triggered conditions to assure Lyapunov stability. Only when the system's indicator fulfills the provided event-triggered condition will the control input signal be updated; otherwise, the control input will stay the same as it is at the last trigger moment. A coordinate compensation approach is developed to reduce the steady-state inaccuracy of trajectory tracking. Finally, simulation experiments are used to assess the effectiveness of the proposed technique for trajectory tracking.