Research On Effects Of Ship Turning Performance Under Rudder/Fin Control

Ship maneuverability directly relates to the survivability of ship in the sea, andturning performance is an important part in it. However, the turning motion alwaysoccurs with heeling, if there have some interference force. It is easy that accidenthappen like ship turn over. Therefore, this paper mainly studies the ship turningperformance under the rudder and fins control. On the basis of original turningperformance, add the control effect of the fins, which change the ship turningperformance, research of the heeling and turning circle’s elements in ship turning areconducted separately. Base on the study of the subject content, the main work of thispaper is as follows:Firstly, the nonlinear motion model of four-degree of freedom of the vessel isbuilt. The effects of hydrodynamic force and torque on hull, propeller, rudder and finsare taken into account respectively. The third order hydrodynamic derivatives,nonlinear characteristics of transmission mechanism of fins and the effective angle ofattack of the fins were considered in order to achieve a model precise enough.Because of the variety of the navigation environment, the models of interferences offorce and torque acting on the ship by random waves, constant current and current seawind are established respectively.Secondly, the simulating model is established according to the mathematicalmodel. The simulation of ship turning without fins is performed and the correctness ofmodels is ensured by empirical formulas. The turning performance relates to theinitial speed of the ship, the varying of the rudder angle and rudder speed and theresults of other external interferences are studied.Thirdly, the turning performances of the ship with fins fixed have been analyzed.Simulations are performed with one pair and two pairs of fins. Obtain the manners ofvarieties of turning parameters with fins angle, and the differences between one pairand two pair of fins are obtained by comparison.Finally, the controller is designed according to the turning performances withfins fixed. The traditional PID control method and the neuron adaptive PID controlmethod are adopted. The turning heeling and circle elements of ordinary turningmotions are controlled respectively. The Williams turning with one pair of fins isstudied at last. A series of simulations show that the turning performance of the ship canimprove with stabilization fins. Ship turning heeling can be reduced effectively in seacondition, and when rapid turning is needed or necessary, the parameters of turningtrack can be reduced as can as possible by stabilization fins.