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Vol. 18 (2015 year), No. 1
Agarkov S. A., Pashentsev S. V.
Parametric identification of the Nomoto generalized model
using the apparatus of variational calculus
A new approach to the identification of parameters of the Nomoto generalized vessel model has been proposed. The apparatus of classical calculus and the method of least squares have been used
(in Russian, стр.5, fig. 5, tables. 0, ref 6, Adobe PDF, Adobe PDF 0 Kb)
Vol. 20 (2017 year), No. 4, DOI: 10.21443/1560-9278-2017-20-4
Pashentsev S. V.
Comparative analysis of mathematical models of the ship from the standpoint of controllability of the variances
The paper has shown the choice of the mathematical model of the ship with the help of which in the future will be investigated the process of control of the vessel from deviations of two spaced points of the ship's diametric plane from certain lines called aiming. Two mathematical models of the tanker differing structurally are considered: by type and set of differential equations for their description, which are identified parametrically, i. e. the coefficients describing the model equations have been found. To assess the adequacy of the models, their work on the example of the standard maneuver "Zigzag" with the comparative analysis of results between the data and full-scale tests has been tested. The type of maneuver has been chosen on the basis of proximity of the ship characteristic movements to those that occur when the vessel is steered by deviation. Further research has been carried out by performing the managing for deviations in relation to the set of aiming lines. The control quality indicator of quadratic form which assesses the management effectiveness of each model has been introduced. In this calculation case, a mathematical model of the "speed – drift angle – angular speed of rotation" type presented by Japanese engineers has been proposed for the study of complex controls of the tanker of Project 214 on deviations. The model has given estimates of the quality of controls going to "stock". This will allow in further works on the subject on the basis of this mathematical model to obtain results and make the decisions that lead to fewer managerial risks.
(in English, стр.8, fig. 5, tables. 0, ref 6, Adobe PDF, Adobe PDF 0 Kb)
Vol. 21 (2018 year), No. 4, DOI: 10.21443/1560-9278-2018-21-4
Pashentsev S. V.
Modelling cyclic reverse movements of the vessel using modified Lammeren's curves of screw action
In our national practice, the screw action curves are traditionally used either for positive values of the screw speed n and the vessel's velocity v, or when one of these characteristics of the movement is negative. Consequently, the used curves of the screw action do not allow to create computer simulators for testing specific maneuvering tasks with reversible moves. The purpose of the work is to study the opportunities of mathematical modelling of the vessel's reverse movements, when the propeller advance of the fixed pitch screw is constantly changing. In foreign sources, really universal Lammeren's curves of screw action can be found. The specificity of these curves is that the introduction to them is performed not due to the pitch ratio itself, but due to the angle ? of the direction incident to the propeller blade. This angle is determined by using tangent tg(?) = v/(0.7 ?nD), and it is sensitive to the change of sign of both the ship's velocity v and the revolution speed n. Therefore, these curves are presented as functions of the angle ? in the range of angles 0?–360?. These curves are obtained and described by Lammeren as the results of processing experimental data concerning the thrust and the screw torque and are approximated by Fourier series, in which 20 terms are kept. These curves can be used as universal ones. This allows to integrate a system of two equations: the motion of the vessel and the rotation of the screw with arbitrary signs of these movements' direction by means of MathCad. By setting the law regulating the speed of the ship engine, it is possible to simulate arbitrary maneuvers of the vessel with any change of direction. The considered approach to modeling has been tested in the paper and implemented in the interface control for vessel maneuvering within the computer simulator.
(in English, стр.10, fig. 12, tables. 1, ref 6, adobePDF, adobePDF 0 Kb)
Vol. 21 (2018 year), No. 4, DOI: 10.21443/1560-9278-2018-21-4
Pashentsev S. V.
Managing the process of tanker towing by regulating the cable tension
Automatic control of the towing process is carried out through the impact of a controlled parameter on it – the cable tension which varies depending on the kinematic parameters of the vessel's motion. As a source of formation of the control signal, one can choose various kinematic characteristics of the towed vessel movement: the angle of deviation of the towing cable from the center line (DP); the drift angle; the angular speed of rotation of the vessel while towing. In the course of the study, an evidence-based choice of a specific control characteristic has been made. With the help of this characteristic (and its derivative if necessary), the control law is determined eliminating stable or developing self-oscillations under the action of initial perturbations. In accordance with this law, technically sound design solutions are selected from the existing patent base to help improve the methods of towing marine objects. Model solutions have been made for the project 214 RN tanker (in ballast) based on a previously calculated mathematical model. The primary problem is to solve a system of four first-order differential nonlinear equations; in this case the law of cable tension control is simply proportional. With the complication of the control law to the proportional-differential (PD), it was necessary to expand the system of differential equations to the seventh order; the initial system of the fourth order is supplemented by three equations for the derivatives of the kinematic variables of the problem. During the selection of methods for controlling the towline tension, the criterial characteristic of the control quality has been used and the mean square characteristic of the angular deviation of the towline from the PD of the towed tanker has been selected.
(in Russian, стр.9, fig. 7, tables. 1, ref 0, adobePDF, adobePDF 0 Kb)
Vol. 22 (2019 year), No. 4, DOI: 10.21443/1560-9278-2019-22-4
Pashentsev S. V., Egorov V. Yu.
Maneuvering analysis of a vessel equipped with two azipods using its mathematical model
Azimuth propulsion systems (azipods, screw-steering columns, SSC) are widely used on new types of vessels intended for the implementation of large-scale projects for the integrated development of the Northern Sea Route. The main way to study the operation of such vessels is their mathematical modeling with the inclusion in the model of both the hull of the vessel and the azimuth propulsion that it is equipped with. The model is complicated when the ship is equipped with not one but two azipods, which in the process of work affect each other in a certain way. During the study, a complicated model of a ship with the displacement of about 36 thousand tons, equipped with two azipods, has been considered. The hull is described using the model in displacements, the operation of each azipod is described using the algorithm of A. D. Gofman. When determining the base value of the stop of each azipod screw (before it is turned), the action curve of the Lammeren screw has been used. Further calculations related to the rotation of the azipods and changes in the flow around the propeller blades are based on the approximation of the curves given in the A. D. Gofman reference book. The computer study of the model (both the hull of the ship and each azipod) consists in the arbitrary maneuvering of the ship to obtain kinematic (linear and angular velocities) and power (forces and moments) characteristics. The results are presented in the form of a set of graphs and a number of conclusions made based on the analysis of the obtained model data. The simulation has been carried out using a software package performed by the authors in two software and computing environments (VB6 and MathCad) and registered by the Federal Service for Intellectual Property.
(in Russian, стр.9, fig. 9, tables. 0, ref 5, AdobePDF, AdobePDF 0 Kb)
Vol. 26 (2023 year), No. 4, DOI: 10.21443/1560-9278-2023-26-4
Pashentsev S. V.
Neural networks as a tool for improving the mathematical model of ship motion
Using neural networks opens up great opportunities for studying mathematical models of ship motion. Correction by a network of identified parameters of the selected model should be as adequate as possible to the results of standard full-scale tests defined by the IMO Resolution N 137 of 2002. A mathematical model in displacements is considered, containing 16 parameters that determine the hydrodynamic forces acting on the ship's hull and steering gear, and is the source of a data set for training the network by randomly varying the parameters and subsequent computer testing. The standard maneuver is a steady-state circulation with fixation of the maneuvering elements: diameter, linear velocity, drift angle and angular velocity of rotation. Improving the quality of the model has consisted of changing its parameters and minimizing the mean square errors of the values of the maneuvering elements obtained during testing. For these purposes, a neural network with 16 inputs (model parameters) and four outputs (maneuvering elements for steady-state circulation) has been built. The data set for training the network was obtained using a program developed by the authors and intended for calculating parameters and conducting maneuver tests. A tanker with a displacement of 30,000 tons was chosen as a test object. Various options for network architecture and tools for working with it have been considered; the Statistica Neural Nets (SNN) software environment and the ANN package in the SciLab environment have been used. Comparative assessments of the results of working with these tools have been given.
(in Russian, стр.17, fig. 18, tables. 4, ref 12, AdobePDF, AdobePDF 0 Kb)