For some largely damaged ships, the conventional methods are unadaptable to estimate their dynamic characteristics as to ships with symmetrical hull section. Based on dry hull modal analysis of flexure — torsion coupling vibration of unsymmetrical ship structures about longitudinal center line, a transfer matrix method to calculate the dynamic characteristics is presented. Taken both shear effect and warping deformations into account, the point and field transfer matrices are derived, and the influence on dynamic characteristics is computed according to different damaged positions and ranges. As examples, the damaged structures are calculated and some interesting conclusions are obtained.
The potential based low order surface panel method is used to predict the hydrodynamic performance of marine propellers. In present method the hyperboloidal quadrilateral panels are employed to avoid the gap between the panels. The influence coefficients of panels are calculated by Morino’s analytical formulations for increasing numerically calculating speed. The pressure Kutta condition is satisfied on the trailing edge of propeller blade by Newton-Raphson iterative procedure. Therefore the pressure coefficients of the suction and pressure faces of blade are equal on trailing edge. The method developed by Yanagizawa is used to determine the velocities on propeller surface, and to avoid the singularity in the numerical differentiation. The predicted pressure distributions and open water performances of general propellers and highly skewed propellers have a good agreement with experimental dat and other calculation results.
Up to now, some technology of neural networks are developed to solve the non-linearity of researched objects and to implement the adaptive control in many engineering fields, and some good results were achieved. Though it puts some questions over to design application structure with neural networks, it is really unknowable about the study mechanism of those. But, the importance of study ratio is widely realized by many scientists now, and some methods on the modification of that are provided. The main subject is how to improve the stability and how to increase the convergent rate of networks by defining a good form of the study ratio. Here a new algorithm named LDBP (least disturbance BP algorithm) is proposed to calculate the ratio online according to the output errors, the weights of network and the input values. The algorithm is applied to the control of an autonomous underwater vehicle designed by HEU. The experimental results show that the algorithm has good performance and the controller designed based on it is fine.
In this paper, maximum-likelihood (ML) and its relaxation algorithm, which are used to identify the mathematics model of an underwater vehicle(UV), are discussed. With the trial data of zigzag tests, the hydrodynamic derivatives of the UV were estimated, and the relaxation algorithm is confirmed to have better astringency from the contrast between the two methods. Then a simulation environment based on these parameters is established to verify the validity and effect of these methods. The result shows the model is credible and the methods are very useful for the research of maneuverability and adaptive control of underwater vehicles.
Using the air plasma ignition technique, physicochemical process of burning can be accelerated; concentration limit of retrofires both can be extended; reliability of retrofires and stability of burning can be improved. In this paper, using internal equivalent heat area in place of electric arc that created Ohm heat, the flow fields of thermodynamic equilibrium chemistry congealment and chemistry non-equilibrium in the plasma generator were simulated. The influences of the inlet prerotation angle of air, the inlet total pressure of air and the airflow compression angle of spray nozzle on the temperature on the surface of electrode nearby the electrode spot and the average temperature of outlet of spray nozzle were contrasted and analyzed. Considering the chemistry non-equilibrium flow, the change of temperature on the surface of electrode after ablation of electrode was further studied. As a result, when the internal flow field of plasma generator was calculated, if the computation model of congealment flow was used, although the parameter change rules were consistent with those of chemistry non-equilibrium, the results had much difference with the chemistry non-equilibrium. So the results of the computation of congealment flow cannot be completely used in quantitative analysis.
A new reasonably perfect dynamic mathematic model has been established for condenser used in ship nuclear power plant according to its structural features and operating principle. The model has been solved by the Runge-Kutta method. And an analysis program has been developed for dynamic numerical simulation under steady operation condition, disturbance condition, and accident condition. The dynamic characteristics of condenser has been calculated and analyzed under several kinds of disturbances, and the results of calculation are in good agreement with the theoretical analysis.
All kinds of reasons are analysed in theory and a fault repository combined with local expert experiences is established according to the structure and the operation characteristic of steam generator in this paper. At the same time, Kohonen algorithm is used for fault diagnoses system based on fuzzy neural networks. Fuzzy arithmetic is inducted into neural networks to solve uncertain diagnosis induced by uncertain knowledge. According to its self-association in the course of default diagnosis, the system is provided with non-supervise, self-organizing, self-learning, and has strong cluster ability and fast cluster velocity.
This paper introduces the composition, control method and testing results of the integrated control system for the first tidal flow electricity generating (TFEG) ship of China. The control method, control algorithm and the specific circuits for the hydraulics system are also introduced. Our research works are emphasized on the control algorithm of stabilizing frequency and some special problems of the controller. The related protection measures for hydraulic system and TFEG system have been taken. A brief explanation of the water turbine control is given.
A Chebyshev fitting way for a propeller atlas across four quadrants is discussed. As an example, Chebyshev polynomial fitting results and its error analysis are given. Because it’s difficult generally to get a propeller atlas across four quadrants, a way is used to construct an alternative with higher accuracy based on the properties. As an application example, an alternative for the propeller property of a Deep Submergence Vehicle across four quadrants is given practically and a simulation model of the four quadrants propeller for dynamic condition is set up. The model lays a foundation for DSV full operating-condition movement simulation. A lot of simulation work shows that the results are very close to the practical data and, therefore, are effective.
Three key factors are discussed, which affect positioning accuracy of range — range positioning mode and hyperbolic positioning mode. Based on the error elliptical theory, the expressions of positioning error and of positioning geometric factor of range — range positioning mode and hyperbolic positioning mode are derived, and the positioning error and the blind positioning area of two different positioning modes are analyzed. According to the requirement of navigation area, an optimum positional configuration among navigation stations of hyperbolic positioning mode is provided. Some considerable conclusions are obtained, and some graphs of distribution are presented, which are important to study and design a reasonable, precise radio navigation system.
GM(1, 1) is generally used in Grey System Theory which constructs an Ordinary Differential Equation for given series. It is effective for monotone series, and its simulating effect is good and error is small. However, If the series doesn’t have a property of monotone, the simulating effect of GM(1, 1) is not fine, and its error gets bigger. In this paper, we use GM(2, 1) to handle the oscillation series, which uses the Method of Minimum Squares in determining the uncertain parameters. The method avoids a big error while choosing an initial value of O.D.E., and we get good results. Finally, we solve a real problem — the simulation of ship pitch, and obtain satisfactory results.
In this paper we show the method of energy in part with which we can get the model of random wave, and predict the roll motion of unstabilized ship and stabilized ship using the wave model. The control parameters of fin stabilizer are determined according to the performance index. The simulation of the system is also made in this paper. The comparison of the simulation with real ship indicates that the method can be used in the prediction of roll motion of a stabilized ship in random wave.
Presents the fin — propeller test set — up to solve the problem of roll stabilization with ships in full speed range, with which, tests were run in water rank for acquisition of data, and concludes from data acquired that the fin — propeller test set — up produces more lift than simple fin, and provides lateral thrust as well, and it is therefore an effective roll stabilization device for ships in full speed range.
On the basis of the principle of dieless hydrobulging technology, a novel hydrobulging technology for manufacturing hyperbolic plates is proposed. First, a toroidal pipe elbow or a partial toroidal pipe elbow is formed, then the single hydrobulged structure can be cut up into some desired plates. It is proved by experiments and finite element simulation that manufacturing technology of hyperbolic plates adopting integrated hydrobulging forming technology is feasible.
To research the effect of the selection method of multi — objects genetic algorithm problem on optimizing result, this method is analyzed theoretically and discussed by using an autonomous underwater vehicle (AUV) as an object. A changing weight value method is put forward and a selection formula is modified. Some experiments were implemented on an AUV, TwinBurger. The results shows that this method is effective and feasible.