Formation Control Of Underactuated Surface Vehicles Based On Sliding-Mode

In recent years, along with the developing of shipping technology, the formation control of surface ships has received more attention. The system of formation control for surface ships can control a group of ships by using automation technology including the heading, velocity and distance between ships in the formation during the voyage. Then it can achieve some hard and complex masks that an independent ship can not do. The formation control of surface ships has a strong potential for both civil use and military use. It is very important to study on the formation control of surface ships in practice.In this paper, the formation control of surface ships are systematically studied. The contents are as follows:Firstly, we describe the problem of the formation control of under-actuated surface ships. There are two reference frame for under-actuated surface ships, the inertial coordinates and the ship-body fixed frame. The math equations include dynamic equations and kinematic equations. And then we get two control subjects for underactuated surface ships, trajectory tracking control and formation synchronization control.Secondly, with the first control subject, a sliding mode controller to tracking the trajectory is presented for the leader ship after having the expecting trajectory. The controller can not only achieve the first control subject but also despite the presence of environmental disturbances including by wave, wind and ocean current. Numerical simulations are provide to validate the correctness and effectiveness of the proposed controller.Thirdly, with the second control subject, the problem of formation control can be transformed into maintaining invariable distance and angle. Considering the position between leader and followers, a sliding mode controller is presented for the follower ships. The controller can ensure the distance and angle of ships, and the formation is stable. Numerical simulations are provided to validate the correctness and effectiveness of the proposed controller.Fourthly, use the controller of trajectory tracking and formation controller to get the simulation of maintaining and changing formation. With the numerical simulations, the uncertainty of the parameters and the presence of environmental disturbances including by wave, wind and ocean current can be solved.