Research On Surface Ship Formation Control With A Leader Ship

This dissertation studies the control problem of the fully actuated ship formation and the underactuated ship formation with a leader ship for the three degree-of-freedom motion of surge,sway and yaw.With the aid of the analysis/synthesis method for the cascade systems,the formation control problem is transformed into the stabilization control problems of kinematic systems and hydrodynamic systems of the follower ships.The design of the formation controllers is decomposed into the design of kinematic controllers and hydrodynamic controllers.This reduces the complexity of the controller design.And,the stability of the closed-loop systems is analyzed by using Lyapunov stability theory.The main contents are summarized as follows:1)For the fully actuated ship formation control with a leader ship,two different cases are investigated,that is,with and without limited communication range between the leader ship and the follower ships.Firstly,for the fully actuated ship formation control via output feedback without limited communication range,based on the high-gain generalized proportion-integral observers,the linear output feedback controllers and the output feedback controllers with input saturation are designed respectively where the high-gain generalized proportion-integral observers are used for estimating the unknown dynamics and the unmeasurable states.Secondly,for the fully actuated ship formation control with limited communication range,the design method of the formation state feedback controllers is given based on the assumption that the velocities are measurable.And,in the case that the velocities are unmeasurable,the design method of the output feedback controllers is given based on the extension state observers.In the output feedback controllers,the extension state observers are used for estimating the velocities and accelerations of all ships.2)For the underactuated ship formation control with a leader ship,two different cases are investigated,that is,without and with limited communication range between the leader ship and the follower ships.Firstly,for the underactuated ship formation control without limited communication range,a three-step formation control design method is given.Furthmore,the differential of virtual control inputs,the systems uncertainty and the external disturbances are viewed as disturbances;the disturbances are estimated by using the disturbance observers and then compensated in controllers.Secondly,for the underactuated ship formation control with limited communication range,the design methods of the formation controllers with and without the path planning are given respectively.In the formation controllers without the path planning,the sum of the leader ship yaw rate and the drift angle rate is required to satisfy the so-called persistent excitation condition.3)A control method is proposed for multiple tugboats assist the underactuated large ship berthing by using the formation.In the formation,a virtual ship that can fulfill the desired berthing motion is viewed as the leader ship,and the tugboats are viewed as the follower ships.In the tugboats hydrodynamics model,the reaction forces produced by the large ship are seen as unknown input.The disturbance observers are given that make the interconnected systems are composed of the disturbance estimated error equations and the original state equations.Based on the disturbance observers,the design of the tugboats formation controllers is given,and the stability of the closed-loop systems is analyzed.