Motion Analysis And Control Of Trimaran Planning Hull

In recent years,with the development of shipbuilding technology around the world,many excellent performances have emerged in this period.Among those new vessels,the multihull has better buoyancy,stability and seakeeping,maneuverability and stealth than the monohull.In addition to the advantages of large capacity,strong shock resistance,so it has broad application prospects in the civilian and military fields.The trimaran planning hull is a high-performance ship with superior performance in the multihull planning hull,which combines the advantages of catamaran and optimizes the design,and the special trimaran structure can greatly improve the transverse wave resistance of the planning boat.The HST1300 trimaran planning hull is a special type of boat with M-channel and transverse break-grade structure,which can increase the difficulty of modeling.In the process of fast sailing,high speed makes the poor controllability of trimaran planning hull,meanwhile,the wind and flow will produce large low-frequency interference,which makes it difficult to design the model and control system of the planning boat.In this paper,we first establish the inertial coordinate system and the solid coordinate system that is used to describe the movement state of the trimaran planning hull in the domain.And then according to the movement characteristics of the trimaran planning hull,force and torque can be divided up on the basic of physical meaning,and calculate those respectively.Based on the model with six degrees of freedom,the movement characteristics of the trimaran planning hull can be simplified,then establish MMG model with four degrees of freedom.In terms of the specificity of the structure of the planning hull,many hydrodynamic differential coefficient,which is contained in the motion model of the planning hull,can not be solved by traditional calculation methods.CFD numerical simulation method was used for analysis in the article.At first,this article employed the AQWA module in ANSYS to calculate the additional quality of the planning hull.Considering the complexity of the structure and movement of the propeller,fluent unit could be used to analysis and fit this propeller.Finally,the control response model of the planning hull was simulated and verified under the influence of the wind and flow disturbance model.Because of the course deviation caused by outside interference,the classic PID algorithm was used for course control.Taking into account the uncertainty of the external environment changes,it is necessary to use the RBF neural network to adjust the PID parameters online.The learning process of the RBF neural network is relatively large,so the first and second derivatives are used to improve the learning step of the neural network.It is useful to improve calculation speed.Finally,based on the RBF NN-PID control,a disturbance observer,which combines with characteristics of planning hull,was designed to compensate for the disturbance from the external environment and interior of the system.Due to the existence of unknown nonlinear function in the disturbance observer,the RBF Neural Network which has the ability to approach to arbitrary nonlinear function was utilized to observe the unknown function.The disturbance observer can complete observation of unknown items by using this feature.