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Formation control for underactuated surface vehicles in the presence of ocean current

In this paper, a control strategy to the problem of underactuated surface vehicles (USVs) formation in the presence of a slow and irrotational ocean current disturbance is presented. In the first part, the kinematic and dynamic models of USVs are established with ocean current, and the ocean current is estimated by using an ocean current observer. The formation controller is proposed based on the backstepping method, in addition, a filter based on a special nonlinear function is introduced to solve the differential explosion problem in the backstepping control. Then, we discussed the extended leader-follower formation by using the virtual trajectory, the follower can control independently for easy identification. Finally, the stability of the whole system is strictly proved in theory and the simulation results show that the designed formation controller is reasonable and effective.