Virtual target algorithm in cooperative control of marine vessels

Marine vessels (surface and underwater) present dynamic systems which are difficult to control due to their complexity, hydrodynamic effects and external forces. Moreover, cooperative control and guidance of these systems presents a task which still presents an intriguing research topic in the area of marine robotics. This paper presents a guidance method based on virtual targets (VT) applied to marine vehicles. The proposed algorithm is derived using a Lyapunov based approach which guarantees convergence and stability under external disturbances. Firstly, the VT algorithm is applied for path following of a single vehicle. It is demonstrated that this algorithm is convenient for following of conventional paths (line, circle arc, spline). Secondly, the VT algorithm is applied for cooperative control between two marine vehicles. The following formations of marine vessels will be described and analyzed: vehicle following - where one vehicle is the “leader” followed by the “follower” vehicle at a predefined distance; and the “wingman problem” where two vehicles are required to follow a joint path at a constant predefined distance between them. Simulation results of the described algorithms will be given in the paper as well as the discussion on their quality.