Longitudinal Motion Modeling And Simulation Of A Hydrofoil Craft

The hydrofoil craft is a high performance ship which supported by hydrofoils. When thehydrofoil craft moving at high speed, the hydrodynamic produced by the hydrofoils will lift itup out of the water in whole or in part. The hydrofoil craft has the characteristic of lowresistance, high speed and small track wave etc. The reduce of hydrofoil body draft make itmore vulnerable to the waves of the sea environment interference, resulting in severeoscillation. This can make hydrofoil’s seaworthiness reduce, seasickness rate increase, thusaffecting the passenger comfort and the working efficiency of the crew. Therefore, it isnecessary to design the controller in this problem. By controlling the flap at the trailing edgeof hydrofoil, the controller generates control force which can reduce the interference of thewaves, so as to improve the hydrofoil’s seaworthiness and occupant comfort. Therefore wecan see the study of modeling of hydrofoil longitudinal motion and its attitude control in thisarticle.Establish longitudinal motion mathematical model of hydrofoil craft is the premise of thecontroller design. This paper analyzes respectively on the hull and the hydrofoil to establishthe longitudinal motion mathematical model. With the help of the ship-aided design andconstruction of software Maxsurf, many hydrodynamic coefficients in the longitudinal motionequations and disturbance torque impose on the hull in the regular or irregular waves can becalculated quickly. To the disturbance of hydrofoil, the paper based on the foil effective angleof attack changes induced by the speed of the wave particle heave to produce disturbanceforce modeling. And through the model can calculate disturbance force and torque on thehydrofoils produced by waves in different sea conditions. After longitudinal motion modelingof hydrofoil vessels, the paper carried on the stability study firstly; then the hydrofoillongitudinal motion simulation and analysis in different significant wave heights are carriedout after the solution of the longitudinal motion.In order to facilitate the application of the latest control theory to design the controller,this paper transformed the longitudinal motion equation of hydrofoil vessels into the form ofstate space. The paper introduces the design of LQR controller and robust H∞state feedbackcontroller based on the linear matrix inequalities (LMI) algorithm. The design of controller inaddition to consider the traditional performance indicators, namely to reduce the longitudinalmotion displacement and pitch angle of hydrofoil vessels, but also into the seasick rate whichis a index that measure the crew comfort performance. Through the simulation and comparison of statistical data, the controller designed in this thesis has ideal control effect onthe hydrofoil heave, pitch angle and seasickness rate. And it is able to meet the performancerequirements of longitudinal motion of hydrofoil vessels and has a certain reference value.