Research On Ship Motion Control Based On Encounter Angle Decision

Wave and wind disturbance results in undesired motion of the ship. Due to the roll damping is comparatively little, rolling motion is particularly severe. In order to reduce the roll movement and improve the safety of the sailing, it is particularly important to research the control method of ship motion. There has been a trend toward on the integrated fin and rudder roll stabilization theory because it can fully exploit the damping capacity of fins and rudder.In this dissertation,the author summarized the development status of the current integrated fin and rudder roll stabilization research in and out of broad based on a large number of related literatures. Single controller performed effective at a particular working station but bad in other conditions. This paper addressed a switching control technique for an integrated fin and rudder roll stabilization.At first,the author established and simplified the dynamics mathematical model of ship motion and derived the force and moment model of propeller, rudder and fins according to their operating principle. Here the fundamental of rudder roll stabilization was analysis in theory. Through the simulation test in Matlab/Simulink, the control performance of the model is achieved. Meanwhile, the paper discovered the elements which have the biggest impact on ship rolling motion according to the variation of the roll motion frequency response curve.In order to ameliorate the roll stabilization in complex and changeable sea conditions, the application of a switching control scheme for integrated fin and rudder roll stabilization was posed. The application has two components, switching decision and switching controller set.The switching controller set was consisted of different sub-controllers which promotes the system performance in a certain sea state. The switching decision made decisions according to the roll angle,the sea condition and the ship speed in a period of time. It analyses the roll angle data by spectrum analysis and generates the power spectral density histograms. Based on the PSD histograms for different encounter angles which can exhibit the characteristics of the waves, the control algorithm can solved the switching index function. According to this function,the switching decision chooses sub-controller pair which is most suited to the prevailing conditions and ensures that the appropriate controller pair is switched into operation steadily.In order to demonstrate the efficacy of the controller, the author applied the new control algorithm to an identified ship model and conducted a simulation test in Matlab environment.Compared with other controllers such as traditional PID controller, the implementation switching controllers applied to the ship motion control system is more effective.