Hydrodynamic Analysis And Motion Control Of Multi-functional Wing

The multi-functional wing is a new type of anti-rolling device for yachts which offers roll damping during cruising and zero speed.Different from the longitudinal flapping zero-speed fin stabilizer designed with a low aspect ratio,multi-functional wing is mainly characterized by a high aspect ratio and foldable recovery.In this paper,we investigate the lift/drag characteristics for the multi-functional wing by ANSYS for the first part of the work.We focus on the impacts of aspect ratio on the lift/drag,so as to make reasonable suggestions on product development.Firstly,we design geometric models in combination with the NACA0015 airfoil with the area 0.5m~2.Secondly,we investigate the effects of aspect ratios=1,3,5,7 and the attack angles=10°,15°,20°,30°and motion periods=1s,2s,4s on hydrodynamic characteristics by using dynamic mesh technique.Finally,the aspect ratio,airfoil shape and working mode of the multi-functional wing are discussed based on the simulation results and practical purposes.We believed that the aspect ratio of the multi-functional wing should be at least greater than 3;It is more reasonable to use elliptical airfoils with symmetrical front and trailing edges.The second part of the work is about the design of the anti-rolling controller.Firstly,a mathematical model of roll motion is established and the wave disturbance of the ship is discussed.Combined with the results of the first part of the hydrodynamic analysis,the cruise mode and zero speed mode controllers are designed respectively.For the cruise mode,the hydrodynamics of the multi-functional wing can be approximated as linear with the angle of attack.A PID controller based on BP neural network has been designed to improve adaptability to variable and high sea conditions.For the zero speed mode,the hydrodynamic force generated by the wing is more complex and has a nonlinear relationship with variables such as swing angular velocity.Moreover,the ship model at large roll angle is a nonlinear structure.These factors can lead to PID control being unable to directly obtain control variables,and conventional methods often fail to achieve theoretical results.This paper uses a master-slave controller separation strategy to separate the controlled system into input nonlinearity and output nonlinearity.The neural network is used as the inverse model master controller to obtain the intermediate control variables,and a slave controller is constructed through Newton’s numerical iteration inversion,achieving good control results.