Sliding-mode formation control for underactuated surface vessels

Sliding-m ode control laws for controlling multiple unmanned surface vessels in arbitrary formations are proposed. The presented formation control method uses local information as well as the planned gross motion of the formation to achieve mesh stability. A three-degree-of-freedom dynamic model has been used for the surface vessels. It is assumed that each vessel only has two actuators and the vessels are underactuated. Mesh stability and parameter uncertainty in the dynamic model and wave disturbance are considered in designing the controllers. It is shown that the internal dynamics of the underactuated system is also stable. The effectiveness and robustness of these control laws in the presence of parameter uncertainty in the dynamic model and wave disturbances and the mesh stability of the formation are demonstrated by computer simulation.