Cooperative Path-Following of Underactuated Autonomous Marine Vehicles with Logic-based Communication

This paper addresses the problem of steering a group of underactuated marine vehicles along given spatial paths, while holding a desired inter-vehicle formation pattern (cooperative path-following). The CPF problem is divided into a motion control task of making each vehicle track a virtual target moving along the desired path and a dynamic assignment task of adjusting the speeds of the virtual targets so as to achieve vehicle coordination. At the path-following level, the controller derived exhibits a inner-outer-loop structure and includes an observer to estimate the ocean currents and the sway velocity. At the coordination level, the decentralized control algorithm addresses explicitly the case where the communications among the vehicles occur with non-homogeneous, possibly varying delays. Convergence and stability of the overall system are proved formally. Simulations results are presented and discussed.