Coordinated formation pattern control of multiple marine surface vehicles with model uncertainty and time-varying ocean currents

This paper considers the coordinated formation pattern control of multiple marine surface vehicles in the presence of model uncertainty and time-varying ocean disturbances induced wind, waves and ocean currents. Leaderless and leader-follower formation controllers depending on the information of neighboring vehicles are devised based on a backstepping technique. Neural networks together with adaptive filtering methods are employed to extract the low frequency content of the model uncertainty and ocean disturbances. The results are further extended to the formation pattern control with unmatched time-varying ocean currents. An observer is developed to precisely identify the time-varying ocean currents. Then, observer-based leaderless and leader-follower formation controllers are proposed. For both cases, the stability properties of the multi-vehicle systems are established via Lyapunov analysis, and the formation tracking errors converge to an adjustable neighborhood of origin. An advantage of this design is that it results in adaptive formation controllers with guaranteed low frequency control signals, which facilitates practical implementations. An example is given to show the performance of the proposed methods.