Single Point Mooring System Dynamics Modeling And Simulation And Research On Attitude Control

Positioning operations at sea is one of the most important kinds of conditions faced by engineering ship. Currently in the ship engineering and marine engineering, there are two kinds of main positioning system:Mooring System and Dynamic Positioning System (DPS). As the mooring system has a low investment, high reliability, and convenient maintenance, the mooring system is primarily used in positioning system. Dynamic positioning system generates thrust vector by controlling the ship's own power plant to compensate for external forces (wind, waves and flows, etc.) to keep the ship's position within the given scope automatically. Compared to the mooring system, DPS has a higher positioning accuracy, more flexibility, applicable to a variety of sea conditions, highly mobility, stable cost and convenient operation. Therefore, as the necessary supporting measures of ship, the dynamic positioning system needs to be increased usually. Regarding addressing mooring system stability problems as starting point, this paper carries out research on dynamic directional technology of single-point mooring system combining with actual project.Firstly, according to MMG modeling idea, the three degrees of freedom dynamics model of single-point mooring system in the horizontal plane is established.Secondly, starting with the established system dynamics model, computer simulation program for the ship motion under single-point mooring state is carried out. Through analysis, the change of motion situation of ship yawing and external load is obtained.Finally, the study of dynamic directional technology for mooring ship is conducted. Under normal circumstances, dynamic directional is implemented by using outboard machine to provide control which is needed by ship directional. Outboard machines are deployed in the rear hull, and can achieve 180°rotation in the horizontal plane, while the propeller is able to provide the matching thrust. Aiming at the control algorithm of mooring system heading angle automatic keeping, in the previous study, in order to simplify the control method, the direction of outboard machine is vertical to the hull longitudinal axis. Here, the longitudinal hull doesn't produce control force. In the hull coordinate system, the role of the hull on the simplified control center of the hull at the longitudinal axis of the torque and vertical lines outside. The control force acting on the hull is simplified as moment to the hull center and external force vertical to longitudinal axis. On this basis, with the classic PID as control algorithm, the deviation of ship heading as input and the control force of outboard machine as output, the controller is designed to keep ship heading automatically.