| The amphibious air cushion vehicle (ACV) is lifted from ground or water surface by air cushion and propelled by aerial propellers. ACV has amphibiousness, so it is widely used in both the civilian fields and military fields. Because of the structural specificity, as for maneuver ACV is very different from a general ship. Transverse inclination will be induced because of air leakage from one side of shipboard when ACV is turning, and great slip angle will be brought since the less resistance between the ship and water. ACV is apt to turn with high speed and sideslip once it is operated improperly, so it will turn into dangerous running state extremely turnover. So, the analysis of ACV's nonlinear characterstics in theory has great of significance.First, the mathematical model of the hovercraft is established to study stability of ACV in this paper. Simulation of the hovercraft is established. The motion equations are solved by means of Runge-Kutta method, and the transform between fixed coordinate and motion coordinate is realized with freeze-defreeze arithmetic, and the accuracy of the model is verified.Second, the theory of vanishing perturbation is established by the theory of stability of Lyapunov. The perturbation nonlinear direct sailing mathematical model of ACV is established and make sure it is vanishing perturbation system base on the characteristic of perturbation. The result of stability of ACV at different pace is got and make sure the veracity of the result.At last, transform the model of rudder and established the nonlinear rotary steering mathematical model of ACV, make sure it is nonvanishing perturbation system base on the characteristic of the model. The least rudder angle of ACV when it is steering steadily at different pace and different rudder angle is got by the theory of nonvanishing perturbation theroy.The research method and result of ACV in this paper provides theoretical basis on hovercraft controller design for the future. |
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