Formation Tracking of Open Multi-ASV Systems Subject to External Disturbances and Unmodeled Dynamics

Abstract

This paper investigates the formation tracking problem for open multiple autonomous surface vessel (multi-ASV) systems subject to external disturbances and unmodeled dynamics. Unlike conventional multi-ASV systems with a fixed number of ASVs, an open multi-ASV system allows ASVs to leave or join the formation freely, which naturally leads to a dynamically evolving communication topology. These structural variations directly affect the information exchange and the control execution, introducing significant challenges to the achievement of formation tracking. To address these issues, a hierarchical control protocol is developed. First, a distributed observer is designed to estimate the formation tracking error and the velocity of the leader. Then, a virtual controller is constructed to generate reference velocity signals for each ASV. Based on the reference signal, a controller is subsequently designed to regulate the motion of each ASV. To compensate for unmodeled dynamics, a neural network-based estimator is incorporated into the control loop. Furthermore, an analytical method is proposed to characterize the evolution of the error system when an ASV leaves or joins the formation. By constructing appropriate inequalities and employing Lyapunov-based techniques, the formation tracking problem of open multi-ASV systems with external disturbances and unmodeled dynamics is effectively addressed using the proposed control protocol. The effectiveness of the theoretical results is validated through a simulation example.