Research On Cooperated Control Method Of Multiple-Module-Ship

Mobile offshore base (MOB) is generally constituted by several rectangular steel semi-submersible ship modules; each module is equipped with dynamic positioning system. MOB can maintain position, heading and the relative position of each module through the coordination control algorithm, which is a key part of the MOB.This paper researches on the problem of coordination control of multiple modules with the object of MOB. Firstly the kinematics and dynamics mathematical model of MOB and the mathematical model of environmental interference are established, base on which, a dynamic surface controller (DSC) of single ship is designed with the on Lyapunov stability theory. Then the controller is proved to be feasibility through the SIMULINK simulation; The paper analyses of the DSC controller deeply and conducts three improvements with the idea of ADRC:to arrange the transient process based on the ability of propulsion systems; to use a chain of nonlinear tracking-differentiator to estimate the differential signal, to use non-linear extended state observer to observe the total disturbances and compensate feedforward. Simulation shows that the improved controller is more robust and practical.This paper designs coordination controller of three modules ship with Leader-Follower control strategy and Leaderless-Follower control strategy respectively. In the first concept, the one of the ship module is selected as the leader, and the others follow the leader. It may still suffer from "string instability" problems (i.e. spacing errors may amplify along the string). In the Leaderless-Follower strategy, each vessel is controlled to track both an inertial reference as well as its position with respect to adjacent vessels and spacing errors do not spread to the entire system, with strong anti-interference ability.