Prescribed Performance Path Following Control of USVs via an Output-Based Threshold Rule

In this article, a prescribed performance path following control algorithm is presented for underactuated surface vessels (USV) that uses an output-based threshold rule and a shifting function to execute parallel (also called lawn mowing) maritime search missions. The latter consist of classical search patterns suggested by the international aeronautical and maritime search and rescue (IAMSAR) manual. The proposed scheme comprises a guidance and a control module. In the guidance module, a limited boundary-based guidance principle is developed with a position threshold rule to avoid continuous computation of heading reference signals. Associated with the guidance signal, a novel dynamic event-triggered mechanism is derived by designing an output-based dynamic rule without fixed parameters, which has the potential to reduce unnecessary communication resource usage between the controllers and the actuator systems when compared with existing techniques. A shifting function is introduced to ensure that the path following error is within a prescribed region. This will ensure proper balance between communication burden and tracking accuracy in the closed-loop system. Semi-global uniform ultimate bounded (SGUUB) stability of the proposed control system is guaranteed using Lyapunov theory. The advantages and effectiveness of the proposal algorithm are shown via simulations.