Distributed observer-based position-based fuzzy formation control for unmanned surface vessels with input saturation

In this article, a control issue is investigated for achieving distributed formation forming and tracking of multiple unmanned surface vessels (USV) subjected to unknown model dynamics and external disturbance. Additionally, the constraints posed by the lack of velocity measurements and input saturation are considered for each USV. For this purpose, two types of distributed position-based control schemes are presented to constitute formation shape and track target trajectory by steering multiple USVs. The first control scheme is based on acquiring absolute position measurements and communication data, while the second control scheme relies on relative position measurements. In the two aforementioned control schemes, two different types of observers are scheduled to provide essential data support for the corresponding controllers. Then, the unknown data that include unknown model dynamics and external disturbance are approximated by a fuzzy logic system and adaptive laws, respectively. In addressing the issue of controller input saturation, a smooth function and auxiliary system are imported to eliminate the effect of actuator saturation. Finally, suitable Lyapunov functions are selected to analyze the theoretical feasibility of the two designed schemes. Corresponding digital simulations are exhibited to further examine the robustness and effectiveness of the designed control schemes.