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PARAMETRIC IDENTIFICATION FOR SHIP HULL FORMS BY SYMMETRIC MOTIONS AROUND A YAW ANGLE

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The paper presents experimental results on the identification of the inertial parameters and energy dissipation by the symmetric motions of the bodies in a liquid. The object of research is the energy method supplemented by taking into account the coefficients of the dynamic mathematical model of the accelerating and decelerating motion stages and the impact of the solid wall. The subject of research is the problem of exact symmetry of the program motions in various environments and the right choice of the regulator parameters with initial values. The programmed symmetric motions were performed by brushless direct current motor in a small model basin and in the air. When a small tracking error was obtained, the intervals with the highest symmetry were selected. It is necessary to separate the inertial parameters from the dissipative in the calculation formulas. The paper proposed a procedure for iterative tuning of the robust tracking controller, as well as modifications of the adaptation algorithm for the adaptive controller. The right choice of the initial values for the robust controller based on preliminary approximate theoretical calculation improved the quality of the transient responses. Comparative results with the use of the developed method, the least squares method and theoretical formulas are given. The experiments were carried out for the vessel hull and the ellipsoid taking into account the similarity of the Froude and Strouhal numbers in view of the two drafts. The experiment results in the air differ from the results by the nonlinear least squares by no more than 5.1 %. In a liquid with a tracking error about 0.01 % the results differ by no more than 25 %. The theoretical calculation by the known formulas showed different results. The practical relevance of the proposed method is associated with the possibility of high precision parameter identification on a specific program low speed motion with the use of only two angular intervals (with reducing the experiment time).

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