The Modeling Of Rudder/Fin Joint Roll Stabilization System And Research On Sliding Mode Control

When sailing on the sea, due to the influence of wind, waves and other disturbance, the ship will be produced a variety of sway motions inevitably. Excessive roll motion will seriously influence safety and seaworthiness of ship. Rudder/fin joint control system is a roll stabilization device developed in comprehensive consideration of fin stabilizer and rudder roll stabilization, which can ensure the accuracy of course control and achieve good performance on roll stabilization at the same time, thereby improving ship’s course stability, maneuverability, security and comfort of crew and passenger.This thesis focuses on the study about establishing the ship motion nonlinear mathematical model, and designing rudder/fin joint sliding mode control system based on the input-output feedback linearization.Firstly, considering the effects of hydrodynamic force and torque on hull, propeller, rudder and fins respectively, the thesis builds the ship motion nonlinear mathematical model of 4 degrees of freedom (surge, sway, roll and yaw) affected by wind and waves disturbance, and gives the estimation formulas involved parameters in the model. This paper references related theory about the added mass and added moment of inertia produced by fluid following the ship motion proposed by Sun Jinghao in the process of mathematical modeling, which makes the model more comprehensive.Then, according to the parameters of a container ship, the turning test and zig zag test have been simulated using the nonlinear mathematical model of ship motion in this thesis. The simulation results verify the effectivity and feasibility of this model in comparison with the calculated data and ship maneuverability criterion provided by the literature. The model can be used in the ship rudder/fin joint control simulation study.Finally, based on the features of sliding mode variable structure control which is to insensitive in disturbance and model error, combining the theory of nonlinear differential geometry, the sliding mode controller based on the input-output feedback linearization is designed and applied to rudder/fin joint roll stabilization control system. For the convenience of designing the sliding mode controller, ship motion nonlinear mathematical model is simplified to affine nonlinear mathematical model. The simulations of ship stabilization and course-keeping joint control are performed under different sea conditions. The simulation results show that the controller has good robustness, and the control system can achieve better performance on roll stabilization while maintaining the accuracy of course control.