Cooperative Path-following of Multiple Surface Vessels with Parametric Model Uncertainty and in the Presence of Ocean Currents

This paper addresses the problem of cooperative path-following of multiple autonomous vehicles. Stated briefly, the problem consists in steering a group of vehicles along specified paths, while keeping a desired spatial formation arrangement. For a given class of autonomous surface vessels, it is shown how Lyapunov based techniques and graph theory can be brought together to design a decentralised control structure where the vehicle dynamics and the constraints imposed by the topology of the inter-vehicle communication network are explicitly taken into account. Path-following for each vehicle amounts to reducing an appropriately defined geometric error to zero, in the presence of ocean currents and parametric model uncertainty. Vehicle cooperation is achieved by adjusting the speed of each vehicle along its path according to information exchanged on the positions of a subset of the other vehicles, as determined by the communication topology adopted. Global stability and convergence of the closed-loop system are guaranteed.