Simulation Study And Experimental Verification Of Integrated Rudder/Fin Control

Ships in a seaway will inevitably experience undesiable motion in multiple degrees of freedom induced by the action of external environmental disturbances(such as waves,wind andcurrent,etc.).Severe undesirable motion could cause equipment damage,crew discomfort and even capsizing.For conventional ships,roll and yaw are the dominant motion.Integrated rudder/fin control is an effective means of ship motion control,which can maintain the ship’s heading while effectively attenuating the ship’s rolling.This topic focuses on the Integrated rudder/fin control.The main work of this paper is as follows:Firstly,by combining the 3-dof maneuvering model of Hirano and the linear rolling model of conolly,the 4-dof nonlinear motion model of the ship is obtained by considering the coupling of each dof,and the empirical fomulas of the relevant hydrodynamic parameters are given.The hydrodynamics of the propulsion system,the rudders and the fins are taken into account as the control force in this ship model.And the nonlinear element existing in the rudder’s and fin’s servo systems are also analyzed.In this model,the wave disturbance force is taken into account as the environmental disturbance.Then,a computer simulation is built by using the ship model established in this paper,the parameter comes from a real ship.This ship’s maneuvering test and the seakeeping test are carried out in the simulation.Secondly,based on the internal model control method,the nonlinear ship motion equation is linearized as the internal model which is used to design the controller,and the nonlinearity of the system is treated as the system uncertainty.Considering the ship rolling problem as the anti-interference problem of the system,based on the idea of sensitivity function design,a design method of Integrated rudder/fin internal model controller with automatic gain control is proposed.The parameters of this internal model controller are optimized by the ant colony optimazation algorithm.The computer simulation results show that the internal model controller of the Integrated rudder/fin Roll Stabilization designed in this paper could achieve good anti-rolling effect while keeping the heading of the ship which is sailing in a hard seaway.Finally,a relevant free running model is designed for this research.The hardware and software control system of the free running model is described in this paper.The maneuverring test and seakeeping test are also carried out by using the self-propelled model on the open water to be compared with the computer simulation.The experimental results show that there is a certain error between the computer simulation and the free running model test,but it is within a reasonable range.The cause of the error is analyzed,in which the scale effect has a great influence on the free running model test.