Global robust and adaptive output feedback dynamic positioning of surface ships

A constructive method was presented to design a global robust and adaptive output feedback controller for dynamic positioning of surface ships under environmental disturbances induced by waves, wind, and ocean currents. The ship’s parameters were not required to be known. An adaptive observer was first designed to estimate the ship’s velocities and parameters. The ship position measurements were also passed through the adaptive observer to reduce high frequency measurement noise from entering the control system. Using these estimate signals, the control was then designed based on Lyapunov’s direct method to force the ship’s position and orientation to globally asymptotically converge to desired values. Simulation results illustrate the effectiveness of the proposed control system. In conclusion, the paper presented a new method to design an effective control system for dynamic positioning of surface ships.     

航行于波浪中的肥大型船波浪增阻计算研究(英文)

Under the background of the energy saving and emission reduction, more and more attention has been placed on investigating the energy efficiency of ships. The added resistance has been noted for being crucial in predicting the decrease of speed on a ship operating at sea. Furthermore, it is also significant to investigate the added resistance for a ship functioning in short waves of large modern ships. The researcher presents an estimation formula for the calculation of an added resistance study in short waves derived from the reflection law. An improved method has been proposed to calculate the added resistance due to ship motions, which applies the radiated energy theory along with the strip method. This procedure is based on an extended integral equation (EIE) method, which was used for solving the hydrodynamic coefficients without effects of the irregular frequency. Next, a combined method was recommended for the estimation of added resistance for a ship in the whole wave length range. The comparison data with other experiments indicate the method presented in the paper provides satisfactory results for large blunt ship.     

A method based on potential theory for calculating air cavity formation of an air cavity resistance reduction ship

This research is intended to provide academic reference and design guidance for further studies to determine the most effective means to reduce a ship’s resistance through an air-cavity. On the basis of potential theory and on the assumption of an ideal and irrotational fluid, this paper drives a method for calculating air cavity formation using slender ship theory then points out the parameters directly related to the formation of air cavities and their interrelationships. Simulations showed that the formation of an air cavity is affected by cavitation number, velocity, groove geometry and groove size. When the ship’s velocity and groove structure are given, the cavitation number must be within range to form a steady air cavity. The interface between air and water forms a wave shape and could be adjusted by an air injection system.     

A method based on potential theory for calculating air cavity formation of an air cavity resistance reduction ship

This research is intended to provide academic reference and design guidance for further studies to determine the most effective means to reduce a ship’s resistance through an air-cavity. On the basis of potential theory and on the assumption of an ideal and irrotational fluid, this paper drives a method for calculating air cavity formation using slender ship theory then points out the parameters directly related to the formation of air cavities and their interrelationships. Simulations showed that the formation of an air cavity is affected by cavitation number, velocity, groove geometry and groove size. When the ship’s velocity and groove structure are given, the cavitation number must be within range to form a steady air cavity. The interface between air and water forms a wave shape and could be adjusted by an air injection system.     

船舶虚拟装配集成化建模方法研究(英文)

A new method of virtual ship assembly modeling which integrates ship three-dimensional design and ship construction planning was described in this paper. A workflow model of simulation modeling based on the virtual ship assembly process was also established; furthermore, a method of information transformation between the ship three-dimensional design and ship construction plan was formulated. To meet the requirements of information sharing between different systems in the ship virtual assembly, a simulation database was created by using the software engineering design method and the relational data model. With the application of this database, the information of ship three-dimensional design, construction planning, and virtual assembly can be integrated into one system. Subsequently, this new method was applied as a tool to simulate the virtual assembly of a ship, and the results guarantee its rationality and reliability.     

Key technologies of ship remote control system in inland waterways under ship-shore cooperation conditions北大核心CSCD

［Objective ］ To meet the requirements of remotely controlling ship in curved, narrow and crowded inland waterways, this paper proposes an approach that consists of CNN-based algorithms and knowledge based models under ship-shore cooperation conditions. ［Method］On the basis of analyzing the characteristics of ship-shore cooperation, the proposed approach realizes autonomous perception of the environment with visual simulation at the core and navigation decision-making control based on deep reinforcement learning, and finally constructs an artificial intelligence system composed of image deep learning processing, navigation situation cognition, route steady-state control and other functions. Remote control and short-time autonomous navigation of operating ships are realized under inland waterway conditions, and remote control of container ships and ferries is carried out. ［Results］The proposed approach is capable of replacing manual work by remote orders or independent decision-making, as well as realizing independent obstacle avoidance, with a consistent deviation of less than 20 meters. ［Conclusions］The developed prototype system carries out the remote control operation demonstration of the above ship types in such waterways as the Changhu Canal Shenzhou line and the Yangtze River, proving that a complete set of algorithms with a CNN and reinforcement learning at the core can independently extract key navigation information, construct obstacle avoidance and control awareness, and lay the foundation for inland river intelligent navigation systems. © 2022 Journal of Clinical Hepatology. All rights reserved.     

三维测量数据的钢结构虚拟装配过程仿真系统(英文)

The virtual erection simulation system was explained for a steel structure including ship and ocean plant blocks.The simulation system predicted the erection state to optimize any gap or overlap of blocks based on 3-D measurement data.The blocks were modified(cut) on the basis of the simulation result on the ground before erecting them by crane.The re-cutting process was not required and the blocks were erected into a mother ship speedily.Therefore,the erection time is reduced,increasing the dock turnover.     

Research on integrated naval ship design model and its intelligent algorithm

Pointing at naval ship projects creation and evaluation at stage of naval ship concept design,in the mechanism of integrated design based on naval ship synthesis model, ship projects creation and intelligent fuzzy evaluation method is researched, thus the applicability of each algorithm is obtained. Firstly,the naval ship synthesis model is introduced to design process, value and application status of synthesis model in integrated design is then exposed. Then the applicability of single target and multi targets SA algorithm is improved, and the quick generation of naval ship projects is done. After that, multiple projects evaluation method based on Vague fuzzy set is introduced to established the intelligent evaluation model, which can integrate effectively the quantitative and qualitative indexes. At last, the analysis of results comparison shows the advancement and rationality of each method. The example shows the integrated design process researched in this paper can be a great orientation of naval ship project design, and can also be used in other parts of naval ship development.     

船模在简谐激励存在时的运行模态分析(英文)

A ship is operated under an extremely complex environment, and waves and winds are assumed to be the stochastic excitations. Moreover, the propeller, host and mechanical equipment can also induce the harmonic responses. In order to reduce structural vibration, it is important to obtain the modal parameters information of a ship. However, the traditional modal parameter identification methods are not suitable since the excitation information is difficult to obtain. Natural excitation technique-eigensystem realization algorithm (NExT-ERA) is an operational modal identification method which abstracts modal parameters only from the response signals, and it is based on the assumption that the input to the structure is pure white noise. Hence, it is necessary to study the influence of harmonic excitations while applying the NExT-ERA method to a ship structure. The results of this research paper indicate the practical experiences under ambient excitation, ship model experiments were successfully done in the modal parameters identification only when the harmonic frequencies were not too close to the modal frequencies.     

采用遗传算法进行球鼻艏优化的流体动力计算(英文)

Computational fluid dynamics(CFD) plays a major role in predicting the flow behavior of a ship.With the development of fast computers and robust CFD software,CFD has become an important tool for designers and engineers in the ship industry.In this paper,the hull form of a ship was optimized for total resistance using CFD as a calculation tool and a genetic algorithm as an optimization tool.CFD based optimization consists of major steps involving automatic generation of geometry based on design parameters,automatic generation of mesh,automatic analysis of fluid flow to calculate the required objective/cost function,and finally an optimization tool to evaluate the cost for optimization.In this paper,integration of a genetic algorithm program,written in MATLAB,was carried out with the geometry and meshing software GAMBIT and CFD analysis software FLUENT.Different geometries of additive bulbous bow were incorporated in the original hull based on design parameters.These design variables were optimized to achieve a minimum cost function of "total resistance".Integration of a genetic algorithm with CFD tools proves to be effective for hull form optimization.     

槽道型高速滑行艇船型的自动生成(英文)

The creation of geometric model of a ship to determine the characteristics of hydrostatic and hydrodynamic, and also for structural design and equipments arrangement are so important in the ship design process. Planning tunnel high speed craft is one of the crafts in which, achievement to their top speed is more important. These crafts with the use of tunnel have the aero-hydrodynamics properties to diminish the resistance, good sea-keeping behavior, reduce slamming and avoid porpoising. Because of the existence of the tunnel, the hull form generation of these crafts is more complex and difficult. In this paper, it has attempted to provide a method based on geometry creation guidelines and with an entry of the least control and hull form adjustment parameters, to generate automatically the hull form of planning tunnel craft. At first, the equations of mathematical model are described and subsequent, three different models generated based on present method are compared and analyzed. Obviously, the generated model has more application in the early stages of design.     

舰船刚性阻振质量复合托板隔振特性优化设计(英文)

In considering the theory of structural dynamic optimization design, a design method of the structural style of ship composite brace with rigid vibration isolation mass was studied. Two kinds of structural dynamic optimization formulations minimizing the vibration acceleration of the non-pressure hull on the restraining condition of the gross weight of the ship cabin were established: 1) dynamic optimization of the sectional dimensions of the rigid vibration isolation mass in the composite brace; 2) dynamic optimization of the arranging position of the rigid vibration isolation mass. Through the optimization results, sectional dimensions and the arranging position of the rigid vibration isolation mass with better performance in reducing vibration were gained, and some reference was provided for practical engineering designs as well as enrichment of the design method of a novel ship vibration-isolation brace.     

舰船气泡尾流数值模拟(英文)

Based on a volume of fluid two-phase model imbedded in the general computational fluid dynamics code FLUENT6.3.26, the viscous flow with free surface around a model-scaled KRISO container ship (KCS) was first numerically simulated. Then with a rigid-lid-free-surface method, the underwater flow field was computed based on the mixture multiphase model to simulate the bubbly wake around the KCS hull. The realizable k-ε two-equation turbulence model and Reynolds stress model were used to analyze the effects of turbulence model on the ship bubbly wake. The air entrainment model, which is relative to the normal velocity gradient of the free surface, and the solving method were verified by the qualitatively reasonable computed results.     

3-D computational method of wave loads on turret moored FPSO tankers

A three-dimensional method of calculating wave loads of turret moored FPSO (Floating Production Storage and Offloading) tankers is presented. The linearized restoring forces acting on the ship hull by the mooring system are calculated according to the catenary theory, which are expressed as the function of linear stiffness coefficients and the displacements of the upper ends of mooring chains. The hydrodynamic coefficients of the ship are calculated by the three-dimensional potential flow theory of the linear hydrodynamic problem for ships with a low forward speed. The equations of ship motions are established with the effect of the restoring forces from the mooring system included as linear stiffness coefficients. The equations of motions are solved in frequency domain, and the responses of wave-induced motions and loads on the ship can be obtained. A computer program based on this method has been developed, and some calculation examples are illustrated. Analysis results show that the method can give satisfying prediction of wave loads.     

考虑不确定性因素的路径优化(英文)

A route optimization methodology in the frame of an onboard decision support/guidance system for the ship’s master has been developed and is presented in this paper.The method aims at the minimization of the fuel voyage cost and the risks related to the ship’s seakeeping performance expected to be within acceptable limits of voyage duration.Parts of this methodology were implemented by interfacing alternative probability assessment methods,such as Monte Carlo,first order reliability method(FORM) and second order reliability method(SORM),and a 3-D seakeeping code,including a software tool for the calculation of the added resistance in waves of NTUA-SDL.The entire system was integrated within the probabilistic analysis software PROBAN.Two of the main modules for the calculation of added resistance and the probabilistic assessment for the considered seakeeping hazards with respect to exceedance levels of predefined threshold values are herein elaborated and validation studies proved their efficiency in view of their implementation into an on-board optimization system.     

军船雷达目标有效截面预报和缩减研究(英文)

Radar cross section(RCS) is the measurement of the reflective strength of a target.Reducing the RCS of a naval ship enables its late detection,which is useful for capitalizing on elements of surprise and initiative.Thus,the RCS of a naval ship has become a very important design factor for achieving surprise,initiative,and survivability.Consequently,accurate RCS determination and RCS reduction are of extreme importance for a naval ship.The purpose of this paper is to provide an understanding of the theoretical background and engineering approach to deal with RCS prediction and reduction for naval ships.The importance of RCS,radar fundamentals,RCS basics,RCS prediction methods,and RCS reduction methods for naval ships is also discussed.     

Analysis of the flexural vibration of ship’s tail shaft by transfer matrix method

A ship＇s tail shaft has serious flexural vibration due to the cantilevered nature of the propeller＇s blades. Analysis of the nature frequency of flexural vibration is vital to be able to provide effective shock absorption for a ship＇s tail shaft. A mathematic model of tail shaft flexural vibrations was built using the transfer matrix method. The nature frequency of flexural vibration for an electrically propelled ship＇s tail shaft was then analyzed, and an effective method for calculating it was proposed： a genetic algorithm （GA）, which calculates the nature frequency of vibration of a system. Sample calculations, with comparisons by the Prohl method under conditions bearing isotropic support, showed this method to be practical. It should have significant impact on engineering design theory.