Design Of Robust Control System Using Rudder And Fin For Ship

The dynamic performance of ship motion closely related to the marine condition,otherwise, affected by the wind, wave, current and other kinds of disturbance. Because of theship type and load is different, the hydro-dynamic load and disturbance are complicated. Thismakes the ship control system exists a lot of uncertainty, ship motion is a very complicatedmotion, all this brought the control of ship motion great difficulty.In the control of large ships, yawing and rolling are the main control objects. This paperuses robust control theory which adopts to the uncertainty and interference suppression todesign rudder/fin joint control system taking example for one ship. And through the design offuzzy PID controller to control the course. Before the design of control system, this paper firstestablishes the mathematical model of the ship. And in the modeling, fully considering theinterference on the hull create by wind and wave, as well as rudder/fin machine nonlinearlimit. These laid the foundation for design of the good performance of the controller.For rolling control, of both at home and abroad to rudder/fin joint stabilized researches,are still in the stage of theoretical analysis, and basically ignored the coupling between fincontrol loop and rudder stabilization loop, as well as rolling and yawing. Most also did notconsider how to reasonable for system integrated design to achieve optimal damping effectand system performance and so on. In addition, most studies are based on the linear model ofship motion system. These systems without deep analysis of model uncertainty that possibleexisted, including the uncertainty caused by speed change, the uncertainty caused by the wavedisturbance, all kinds of un-modeled dynamic uncertainty, etc.This paper in view of above questions, first improves the control algorithm by design thecontroller using h-infinity mixed sensitivity algorithm. The design process will analysis allsorts of coupling effect that possible existed and gives a set of detailed design schemes tomake the system have optimal performance and achieve good performance on rollstabilization. And this paper also uses the method of dual control h-infinity to design therudder/fin joint controller. The method through zero phase shift design by two loop of rudderand fin to make two channel have the same zero phase in the dominant frequency. So the twochannel characteristic can be added to enhance the system performance on roll stabilization.The paper also compares the effect of two controllers and gives the analysis and explanation.For the yawing control, characteristic of yawing mainly is low frequency characteristic,and the dynamic characteristic of rolling is in medium frequency band, there is a certain band separation between them. So in the designing of whole control system, course controller canbe separately designed and does not affect the design of rolling controller. The traditionalnavigation control system usually adopts PID controller, but the dynamic performance of thecontroller is poor. And fuzzy controller has good dynamic performance, strong adaptability,but steady state accuracy is not high. Based on this, this paper adopts the method of fuzzy PIDto design the steering controller, improving the feature of poor dynamic performance, weakadaptability of traditional PID. The controller can quickly follows course signal and has thegood course tracking and course-keeping performance through the simulation analysis.