Research On Robust Control Method Of S-lay Vessel’s Dynamic Positioning

With the development of global economy, the blood of industry——oil and gasresources are attracting more and more attention; all powers in the world are making their oilstrategy, making competition of international oil resources increasingly fierce. Because theland oil and gas resources are becoming less and less, and the ocean abound with rich oil andgas resources, more and more countries have exploited and transported the undersea oil andgas, so the marine pipeline laying ship become the focus of research, and the S-lay vessel isone of the most commonly used. In order to lay pipe with security, we must have the aid ofdynamic positioning system to control the surging shape of pipe and tracking operation.Firstly, this paper establishes the mathematical model of ship motion and the marineenvironment. We use the appropriate coordinate system to establish the kinematics model ofship; pipe laying ship usually operate in low speed, based on this assumption we obtain shipdynamics model without Coriolis matrix. Then the environment disturbance models of shipsuch as wind, waves and currents environment are established.Secondly, S pipeline model is established. The S type pipe and ship are regarded as amechanical arm system of a number of rigid bodies connected with each other. Calculatingthe angle between adjacent sections, we establish the kinematic and dynamic equations whenship moves in the vertical plane. Then the complete solving method for the state of pipes andpipe-laying ship system’s motion are obtained. We make a simulation, and compare the resultswith the catenary method.Then, according to the control problem of pipe-laying operation of S–lay vessel withoutdisturbance, we propose a robust control method for ship surge position, to achieve the aim ofthe pipe shape control indirectly. According to the condition of surging shape variation of pipewhen S–lay vessel works with disturbance, a robust adaptive control method is chosen tocontrol the shape of pipe effectively. Kinetic equations are given by earlier system of pipesand pipe-laying vessel, according to the manipulator characteristics, we choose theappropriate Lyapunov function, and prove the stability of the control method in theory.Simulation analysis shows both control method’s effectiveness.Finally, according to the S–lay vessel tracking work, introducing the principle of pathplanning and tracking control, combining with the previously obtained pipe-laying vesselmovement’s mathematical model, we research a tracking robust control method of the S–layvessel. By selecting reasonable Lyapunov function, the stability of the robust control method is proved, and then we verify its validity by simulation in two conditions: with and withoutdisturbance.