Practical implementation of parmetric identification of linear mathematical models of marine vessels by tables of maneuvering elements

The paper considers the practical implementation of the algorithm for identifying the parameters of linear mathematical models of Nomoto 1st and 2nd order of the marine vessels based on experimental data. Information from the maneuvering element tables containing information on the vessel’s circulation is used as experimental data. The initial data are presented in the form of discrete sampling, which allows obtaining the model parameters in a discrete form and then making the transition to a continuous form. The initial data are formed for each type of motion: a loaded vessel, a vessel in ballast, half-board and aboard, starboard and port aboard. The paper uses a method for determining the parameters of the transfer functions of the obtained models using the least squares method for transient characteristics. To improve the quality of the assessment of the parameters of the identified model, it is proposed to interpolate the initial data. The following methods are used in the paper: linear interpolation, interpolation by adjacent points, cubic and spline interpolation. To implement the proposed method, a program has been developed and implemented in the MatLab environment, which allows interpolation of the transient response by a method selected from the proposed ones, and then, based on the interpolated values, to determine the parameters of the transfer function. A block diagram and description of the algorithm for the operation of this program are provided. The result of its operation is a model with its own parameters for each case of vessel motion. The program displays graphs of transient processes for the initial data and calculated ones for each selected type of interpolation, and also displays the parameters of the transfer functions of the models. A description of the source data file used is provided. To assess the quality of software-implemented identification models, a model circulation trajectory is calculated and its graphic construction occurs. As a result of the program, the obtained linear mathematical models are proposed to be grouped and presented in interval form.

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