Sliding mode formation control for under-actuated autonomous surface vehicles

Sliding mode control laws for controlling multiple unmanned surface vehicles in arbitrary formations are proposed. The presented formation control method uses only local sensor-based information. A three-degree-of-freedom dynamic model has been used for the surface vehicles. It is assumed that each vehicle only has two actuators and the vehicles are under-actuated. Parameter uncertainty in the dynamic model and wave disturbance are considered in designing the controllers. It is shown that the internal dynamics of the under-actuated system is also stable. The effectiveness and robustness of these control laws in presence of parameter uncertainty in the dynamic model and wave disturbances are demonstrated by computer simulations. The control scheme is scalable and can be used to control a number of unmanned surface vehicles moving in very general formations