Simulation Of Ship Maneuvering And Study Of Rudder/Fin Roll Stabilization Control

Ship maneuverability is ship capability that is a ship performance of keeping orchanging initial course. The ship which has a better maneuverability can escape obstacleseasily when the ship is moving, that would reduce happen of ship collision. As thecomplexity of ocean environment, once ships turn turtle or collide each other, people wouldbe hurt and chemistry would be leaked, that would cause serious society problems andzoology problems, large economic loss would appear. So stricter request of shipmaneuverability is proposed and more methods of roll stability are appealed. In order toreduce roll of ship, except for fins, controlling rudder can effect ship roll moment whenrudder effect ship yaw, combining rudder and fin to control ship can reduce more roll andkeep course. So rudder/fin roll stabilization is attached importance. Based on the content ofthe task, the paper did many works.Firstly, ship motion equations which are nonlinear mathematical model in four-dofbased on Hirano model are founded, that give solving method of hydrodynamic parameters,and contain the mathematics model of rudder and fin. In the model, the saturation limits ofrudder and fin servo systems are considered, and effect attack angle of rudder and fin. Theangle rate effects valid rate and angle, then it effects hydrodynamic force.Secondly, the environment disturbance model was completed, that contains ocean wave,current and wind. Regular wave disturbance was described in math method using cosineserial coefficient, wave random disturbance was completed though repeated added ofregular wave. Analyse current and wind, current disturbance model was completed usingrelation between relative rate and absolutely rate. Wind disturbance model was completedunder the method of Isherwood formula.Thirdly, turning and Z type motion as the typical movements of ship maneuverabilitywere analyzed and simulated. The simulation results contrast with test datas, and the errorwas small, that indicated the method was feasible. Other ship maneuverability motions weresimulated, for example, Williamson turn, repeated rudder and so on. The effects of speed,rudder angle rate and rudder angular rate were considered. The results indicated that rudderparameters and rudder angle rate effect maneuverability except ship parameters, somaneuverability can be optimized through rudder parameters optimization when the shipparameters were known.At last, there are many uncertain elements in ship motion control, H∞mix sensitive robust control algorithm was elected to attain rudder/fin roll stabilization controller. Theproblem were translated into H∞typical problem, then into mix sensitive problems, afterselecting weighting functions, judging system stability, robust controller was acquired. Thesimulation results indicated that under this controller, ship has better roll stabilization andcourse keeping at different counters in sea environment disturbance, and increasing rudderangle rate can improve the impact of roll stabilization and course keeping.