Observer-Based Adaptive Fuzzy Event-Triggered Path Following Control of Marine Surface Vessel

In this paper, the path following control scheme of a fully actuated marine surface vessel under the condition of model uncertainties and unmeasurable states is developed. Firstly, an adaptive fuzzy state observer is designed to estimate the unmeasurable states of the vessel. To guarantee the robustness of the system, a kind of sliding mode intermediate variable with the improved approaching law is constructed to eliminate the chattering effect and the vessel can obtain a better control performance. By combining with the relative threshold event-triggered strategy, the controllers only update when the triggering conditions are met. Hence, the update frequency of controllers and the loss of actuators are enormously decreased in contrast with the fixed threshold event-triggered control law. Theoretical analysis proves that the tracking error can converge into a compact set, meanwhile the Zeno behavior is avoided. Simulation results and comparative analysis indicate the availability and superiority of the designed controllers.