Coordinated path following control of multiple underactuated underwater vehicles

This paper investigates the coordinated path following problem of multiple underactuated underwater vehicles (UUVs) which move on the desired paths. To deal with the path following control problem, the path tracking error equation is established in Serret-Frenet frame based on ‘virtual’ guidance. The controller design process is divided into kinematic and dynamic two parts with backstepping method, which leads a simplification for the design procedure. To deal with the coordination control problem, the speeds of UUVs are adjusted about their nominal values so as to synchronize their positions and achieve coordination. It is shown that the system that is obtained by putting together the path following and coordination subsystems can be viewed as cascade connection system. Using this fact and recent results from nonlinear systems and graph theory, the path following and coordination errors are driven to a neighborhood of zero. Moreover, these controllers are distributed in the sense that the controller design for each UUV only requires relative state in formation between itself and its neighbors. Finally, a simulation example demonstrates the effectiveness of the control method.