Identification Of Longitudinal Motion Model Of High-speed Trimaran And Research On The Pitch Reduction Control Law

Among many new types of ships,trimaran has excellent applications in many fields due to its fast and efficient navigation characteristics,flexible and stable hull design and stability performance in complex and harsh environments,and has increasingly become the focus of research and development direction of new types of ships at home and abroad.However,due to the special structure of the trimaran's slender hull,it will produce a larger heave and pitch range in the course of running,which will affect all aspects of the trimaran's performance,but also restrict the further application of the trimaran.Therefore,the main research content of this paper is how to achieve the longitudinal roll reduction of trimaran,and then make the navigation motion of high-speed trimaran more stable.Firstly,the mathematical model of ship longitudinal motion is determined by the method of system identification based on the experimental data of ship models.On this basis,T-foil and flaps are used as anti-rolling attachments of trimaran,and relevant control algorithms are added to the simulation to achieve the purpose of longitudinal anti-rolling of high-speed trimaran.In this paper,T-foil and flaps are used as anti-rolling attachments of trimaran,and the longitudinal motion of trimaran during high-speed navigation is analyzed.Firstly,the motion model and force model of the trimaran are analyzed and established separately.and the experimental data of the trimaran towing pool are fitted,calculated and identified by the least square method in classical system identification method and the genetic algorithm in modern identification method respectively.The input signal can be transformed into ship heave and sink.The force and pitching moment models of ships are presented,and the advantages and disadvantages of the two identification methods are compared and analyzed.Then the mathematical model of anti-rolling appendage is analyzed and established,and the actual anti-rolling effect is simulated.The longitudinal motion simulation of trimaran is carried out by CFD software,and the lift and drag coefficients of anti-rolling appendage are solved.The size and installation location of anti-rolling appendage with the best anti-rolling effect are analyzed and selected.Finally,the longitudinal motion simulation system of multi-hull ship is established by using MATLAB Simulink,and the decoupling controller is designed by using relevant control methods.On the one hand,the pitch reduction effect is optimized to minimize the pitch amplitude of the trimaran,on the other hand,the coupling effect between the various links in the whole system is reduced so that they do not interfere with each other.The traditional PID control method and the fuzzy PID control method areadopted in the control method.The anti-rolling effect and applicable environment of the two control methods are compared and analyzed.The simulation results show that the pitch reduction control effect of the fuzzy PID is better than that of the traditional PID control method,and the coupling effect of the whole trimaran motion system is obviously reduced after the decoupling controller is added,and the longitudinal roll reduction effect is more ideal.