Research On Ride Control System For Wave Piercing Catamarans Based T-foil And Stern Flaps

When the wave piercing catamarans(WPC)is sailing at a high speed,it will be disturbed by the complicated sea wave environment,which will cause the hull to move violently.Ship motion poses a serious threat to the safety of passengers and equipment on board and may cause damage to the structure of the hull itself.If a ship has a high-requirement combat mission,its unstable wobble will reduce the ship’s ability to strike accurately,which may lead to the failure of the equipment in serious cases.In addition,the vertical acceleration caused by the ship motion will lead to seasickness reaction,which can cause vomiting,convulsion and so on according to the individual physique.According to the description above,when the ship is sailing at a high speed,it must be equipped with the stabilizer to restrain the ship’s motion to ensure the safety and comfort of the ship’s navigation.Firstly,based on the sea wave spectral density analysis of several sea areas,including the wave spectrum suitable for the coastal area of China,such as the sea spectrum of the East China Sea and the Yangxi Sea,the forces and moments of sea wave disturbance can be obtained under the different sea states(SSN).Then,through the modeling and analysis of the general six degrees of freedom(6 DOF)motion model of the ship,the two degrees of freedom(2 DOF)and three degree of freedom(3 DOF)motion models of the WPC are obtained under head seas and beam seas.Then,the hydrodynamic coefficients of longitudinal coupling motion of the WPC are obtained based on strip method.On the other hand,the roll motion response is obtained,through the hydrodynamic motion simulation of the WPC hull.Finally,the hydrodynamic coefficients of ship roll motion can be obtained by solving the roll attenuation model.Secondly,in order to suppress the vertical motion of the ship,such as submerging bow and trimming,T-foil and flaps are installed at the bow and stern of the WPC,respectively.The height of the strut varies because of T-foil’s different position in the bow of the ship.Moreover,the proper range of strut’s height is selection based on control device practicability and safety considerations.Then,the optimum T-foil model matching the WPC vessel is obtained,throughout simulating the bare ship motion and simulating the T-foil constrained by the hull under different sea conditions and sailing speeds.Finally,by analyzing the motion reduction effect of T-foil and flap in different areas,the application range of attack angle of those under different sea conditions is obtained.So it can improve the seakeeping of the ship to the greatest extent and improve the comfort of the ship.Thirdly,the design of ship ride control system based on T-foil/flaps has the problem of selecting the combination form among the control devices.The control scheme based on T-foil and stern flap is divided into three forms:single T-foil control,single flap control and the combination of the two,each of which includes the choice of different area of hydrofoil.Then,through the analysis of the motion reduction effect of different schemes,the optimal reduction effect is the combination form of T-foil and flap.This work presents optimal linear quadratic regulator(LQR)based on genetic algorithm(GA)to reduce the heave and pitch motion.Through the global optimization of the weight coefficient,T-foil/flaps can provide effective control force and moment to achieve the purpose of ship heave and pitch reduction.Then,based on the LQR-GA algorithm,the linear quadratic Gaussian(LQG)algorithm and the model predictive control(MPC)algorithm to control the roll,heave,and pitch motion of the catamarans.The final results show that the ship motion is reduced in varying degrees.The purpose of evaluating the comfort of the ship under the conditions of head sea and beam sea is to check the anti-roll,heave,and pitch effect based on T-foil/flaps control device.According to the three-dimensional images of seasickness,the establishment of ship motion control system based on T-foil/flaps can effectively improve the comfort of the hull and reduce the occurrence of seasickness.Finally,the simulation study of the ride control for WPC vessel based T-foil/flaps control device is carried out based on the above model establishment.First,the wave disturbance model,hull motion model,hydrofoil lift model and the proposed control algorithm model are built using MATLAB&SIMULINK and Lab VIEW human-computer interaction software,and the ship’s reduction effect is demonstrated by simulation curve image or 3D dynamics.Furthermore,the control signal is output to the control hydrofoil module in the computer based on the design of control algorithm using NI CompactRIO controller.And the reduction effect is also obtained.At the end,through the ship motion simulation platform,the output demonstration of the ship motion can visually feel the movement state of the ship with the hydrofoil under the sea wave disturbance,and verify the designed T-foil/flaps’ feasibility and effectiveness for the ride control system of WPC vessel.