Sliding mode robust control for formation of multiple underactuated surface vessels

The paper studies the formation control problem for multiple underactuated surface vessels by utilizing leader-follower approach with parameter uncertainties and external disturbances, and the proposed formation control method that the follower tracks a reference trajectory based on the leader´s position and the predetermined formation without the need for leader´s velocity and dynamics. A virtual ship is constructed such that its trajectory converges to the reference trajectory of the follower in limited time. The Ships formation control model is established on the virtual ship under leader-follower mode. The robust controller can effectively deal with parameter uncertainties and external disturbances by combining backstepping with sliding-mode control method, which can make the follower move along the trajectory of the virtual ship, maintain the desired formation with leader and achieve the purpose of formation control. A Simulation of the formation control for the multiple underactuated surface vessels is performed by using three real Northern Clippers. Results validate the effectiveness of the proposed method.