Combined straight and circular path generation for aquatic environmental monitoring with multiple USVs

In this paper, we examine coordinated aquatic environmental monitoring using multiple Unmanned Surface Vehicles (USVs). We employ the hierarchical control architecture presented in our previous work, where the circular paths are updated online based on the concept of so-called constraint-based control. In this paper, we further develop the path generator so that USVs can take a straight path, in order to enhance energy efficiency and reduce wiggling movement. In addition, we refine the lower-level safe control to avoid inter-USV collisions that frequently occur in the presence of straight paths. The proposed control architecture is demonstrated through numerical simulation and an experiment using a testbed with real USVs.