Maintenance decision problems generally involve multiple criteria which apparently are best addressed using Multi-Criteria Decision Making (MCDM) tools. This paper describes the use of a hybrid MCDM technique in prior...Maintenance decision problems generally involve multiple criteria which apparently are best addressed using Multi-Criteria Decision Making (MCDM) tools. This paper describes the use of a hybrid MCDM technique in prioritizing maintenance strategy for ship systems. The Hybrid MCDM technique combines Delphi method, AHP and TOPSIS methods. While the Delphi method and AHP are applied in screening of decision criteria and decision criteria weights determination respectively, the TOPSIS method is used in the ranking of alternative maintenance strategies. Five alternative maintenance strategies which include corrected maintenance, scheduled overhaul, scheduled replacement, continuous on-condition task and scheduled on-condition task are considered and the optimum maintenance strategy is selected based on twelve critical maintenance decision criteria. To demonstrate the suitability of the approach a case study of sea water pump of the central cooling system of a marine diesel engine is used.展开更多
The solid oxide fuel cell(SOFC)power system fueled by NH_(3)is considered one of the most promising solutions for achieving ship decarbonization and carbon neutrality.This paper addresses the technical challenges face...The solid oxide fuel cell(SOFC)power system fueled by NH_(3)is considered one of the most promising solutions for achieving ship decarbonization and carbon neutrality.This paper addresses the technical challenges faced by NH_(3)fuel SOFC ship power system,including slow hydrogen(H2)production,low efficiency,and limited space.It introduces an innovative a NH_(3)-integrated reactor for rapid H2 production,establishes a safe and efficient all-electric SOFC all-electric propulsion system adaptable to various sailing conditions.The system is validated using a 2 kW prototype experimental rig.Results show that the SOFC system,designed for a target ship,has a rated power of 96 kW and an electrical efficiency of 60.13%,meeting the requirements for rated cruising conditions.Under identical catalytic scenarios,the designed reactor,with highly efficient heat transfer,measuring 1.1 m in length,can achieve complete NH_(3)decomposition within 2.94 s,representing a 35%reduction in cracking time and a 42%decrease in required cabin space.During high-load voyage conditions,adjusting the circulation ratio(CR)and ammonia-oxygen ratio(A/O)improves system efficiency across a wide operational range.Among these adjustments,altering the A/O ratio proves to be the most efficient strategy.Under this configuration,the system achieves an efficiency of 55.02%at low load and 61.73%at high load,allowing operation across a power range of 20%to 110%.Experimental results indicate that the error for NH_(3)cracking H2 is less than 3%within the range of 570-700℃,which is relevant to typical ship operation scenarios.At 656℃,the NH_(3)cracking H2 rate reaches 100%.Under these conditions,the SOFC produces 2.045 kW of power with an efficiency of approximately 58.66%.The noise level detected is 58.6 dB,while the concentrations of CO_(2),NO,and SO_(2)in the flue gas approach zero.These findings support the transition of the shipping industry to green,clean systems,contributing significantly to future reductions in ocean carbon emissions.展开更多
Multivariables, strong coupling, nonlinearity, and large delays characterize the boiler-turbine coordinated control systems for ship power equipment. To better deal with these conditions, a compound control strategy b...Multivariables, strong coupling, nonlinearity, and large delays characterize the boiler-turbine coordinated control systems for ship power equipment. To better deal with these conditions, a compound control strategy based on a support vector machine （SVM） with inverse identification was proposed and applied to research simulating coordinated control systems. This method combines SVM inverse control and fuzzy control, taking advantage of the merits of SVM inverse controls which can be designed easily and have high reliability, and those of fuzzy controls, which respond rapidly and have good anti-jamming capability and robustness. It ensures the controller can be controlled with near instantaneous adjustments to maintain a steady state, even if the SVM is not trained well. The simulation results show that the control quality of this fuzzy-SVM compound control algorithm is high, with good performance in dynamic response speed, static stability, restraint of overshoot, and robustness.展开更多
Based on support vector machines, three modeling methods, i.e., white-box modeling, grey-box modeling and black-box modeling of ship manoeuvring motion in 4 degrees of freedom are investigated. With the whole-ship mat...Based on support vector machines, three modeling methods, i.e., white-box modeling, grey-box modeling and black-box modeling of ship manoeuvring motion in 4 degrees of freedom are investigated. With the whole-ship mathematical model for ship manoeuvring motion, in which the hydrodynamic coefficients are obtained from roll planar motion mechanism test, some zigzag tests and turning circle manoeuvres are simulated. In the white-box modeling and grey-box modeling, the training data taken every 5 s from the simulated 20°/20° zigzag test are used, while in the black-box modeling, the training data taken every 5 s from the simulated 15°/15°, 20°/20° zigzag tests and 15°, 25° turning manoeuvres are used; and the trained support vector machines are used to predict the whole 20°/20° zigzag test. Comparisons between the simulated and predicted 20°/20° zigzag tests show good predictive ability of the proposed methods. Besides, all mathematical models obtained by the proposed modeling methods are used to predict the 10°/10° zigzag test and 35° turning circle manoeuvre, and the predicted results are compared with those of simulation tests to demonstrate the good generalization performance of the mathematical models. Finally, the proposed modeling methods are analyzed and compared with each other in aspects of application conditions, prediction accuracy and computation speed. The appropriate modeling method can be chosen according to the intended use of the mathematical models and the available data needed for system identification.展开更多
The transfer alignment problem of the shipborne weapon inertial navigation system （INS） is addressed. Specifically, two transfer alignment algorithms subjected to the ship motions induced by the waves are discussed....The transfer alignment problem of the shipborne weapon inertial navigation system （INS） is addressed. Specifically, two transfer alignment algorithms subjected to the ship motions induced by the waves are discussed. To consider the limited maneuver level performed by the ship, a new filter algorithm for transfer alignment methods using velocity and angular rate matching is first derived. And then an improved method using integrated velocity and integrated angular rate matching is introduced to reduce the effect of the ship body flexure. The simulation results show the feasibility and validity of the proposed transfer alignment algorithms.展开更多
Because the general object of ship steering control system is singular, the state Of rudder force and the state of disturbance are separated, and the generalized yaw output disturhance is obtained. Furthermore, singul...Because the general object of ship steering control system is singular, the state Of rudder force and the state of disturbance are separated, and the generalized yaw output disturhance is obtained. Furthermore, singular system control problem of ship yaw and sway coupled system is transferred into nonsingular standard control problem. Then according to the linear fractional denoting algorithm of the rational function parameter perturbation system, the Linear Fractional Transform （LFT） model of yaw and sway coupled motion is solved, which is used to design the ship steering robust control system. For the ship steering system with the uncertain parameters, the robust control law is designed based on H^∞ μ-synthesis. And the robust performance of the system is analyzed and the simulation validation is made. Simulation results show that the designed control system has excellent control effect and robustness.展开更多
Thrust bearing is a key component of the propulsion system of a ship. It transfers the propulsive forces from the propeller to the ship＇s hull, allowing the propeller to push the ship ahead. The performance of a thru...Thrust bearing is a key component of the propulsion system of a ship. It transfers the propulsive forces from the propeller to the ship＇s hull, allowing the propeller to push the ship ahead. The performance of a thrust bearing pad is critical. When the thrust bearing becomes damaged, it can cause the ship to lose power and can also affect its operational safety. For this paper, the distribution of the pressure field of a thrust pad was calculated with numerical method, applying Reynolds equation. Thrust bearing properties for loads were analyzed, given variations in outlet thickness of the pad and variations between the load and the slope of the pad. It was noticed that the distribution of pressure was uneven. As a result, increases of both the outlet thickness and the slope coefficient of the pad were able to improve load beating capability.展开更多
Common effect of wave and slip of internal heavy load will make rolling of the roll-on ship serious. This is one of the important reasons for overturn of ro-ro ships. The multibodies System with a floating base is com...Common effect of wave and slip of internal heavy load will make rolling of the roll-on ship serious. This is one of the important reasons for overturn of ro-ro ships. The multibodies System with a floating base is composed of ro-ro ship and slipping heavy load. This paper takes the rolling angle of the ship and the transverse displacement of the heavy load on desk as two freedoms. Making use of analysis of apparent gravitation and apparent buoyancy, the wave rolling moment is derived. By use of dynamic method of multibodies system with a floating base, dynamic equations of the system are established. Taking a certain channel ferry as an example, a set of numerical calculation have been carried out for rolling response of the ship and displacement response of the slipping heavy load under common effect of synchro-slipping heavy loads and wave.展开更多
Electric power is widely used as the main energy source of ship integrated power system(SIPS), which contains power network and electric power network. SIPS network reconfiguration is a non-linear large-scale problem....Electric power is widely used as the main energy source of ship integrated power system(SIPS), which contains power network and electric power network. SIPS network reconfiguration is a non-linear large-scale problem. The reconfiguration solution influences the safety and stable operation of the power system. According to the operational characteristics of SIPS, a simplified model of power network and a mathematical model for network reconfiguration are established. Based on these models, a multi-agent and ant colony optimization(MAACO) is proposed to solve the problem of network reconfiguration. The simulations are carried out to demonstrate that the optimization method can reconstruct the integrated power system network accurately and efficiently.展开更多
1.Introduction Maritime transport is the backbone of international trade.The amount of total international maritime trade in million tonnes loaded was 8408 in 2012 and had increased to 11076 by 2019,for an average ann...1.Introduction Maritime transport is the backbone of international trade.The amount of total international maritime trade in million tonnes loaded was 8408 in 2012 and had increased to 11076 by 2019,for an average annual increase of 3.12%.In early 2020,the world fleet contained 98140 ships of 100 gross tonnes and above with 2.06 million dead weight tonnage of capacity[1].The greenhouse gas(GHG)emissions from shipping activities are not negligible.According to the fourth GHG study commissioned by the International Maritime Organization(IMO),in 2018,global shipping emitted a total of 1056 million tonnes of carbon dioxide(CO_(2)),accounting for around 2.89%of global anthropogenic CO_(2) emissions[2].Due to the international nature of shipping,efforts to control CO_(2) emissions from ships are absent from the Kyoto Protocol and the Paris Agreement.In an attempt to phase out carbon emissions from shipping entirely,the IMO formulated a strategy to cut the total annual GHG emissions from shipping by at least 50%from their 2008 levels by 2050[3];however,no mandatory rules have been promulgated since the release of this strategy.展开更多
A terminal sliding mode fuzzy control based on multiple sliding surfaces was proposed for ship course tracking steering, which takes account of rudder characteristics and parameter uncertainty. In order to solve the p...A terminal sliding mode fuzzy control based on multiple sliding surfaces was proposed for ship course tracking steering, which takes account of rudder characteristics and parameter uncertainty. In order to solve the problem, the controller was designed by employing the universal approximation property of fuzzy logic system, the advantage of Nussbaum function, and using multiple sliding mode control algorithm based on the recursive technique. In the last step of designing, a nonsingular terminal sliding mode was utilized to drive the last state of the system to converge in a finite period of time, and high-order sliding mode control law was designed to eliminate the chattering and make the system robust. The simulation results showed that the controller designed here could track a desired course fast and accurately. It also exhibited strong robustness peculiarly to system, and had better adaptive ability than traditional PID control algorithms.展开更多
A fuzzy robust path tracking strategy of an active pelagic trawl system with ship and winch regulation is proposed.First,nonlinear mathematic model of the pelagic trawl system was derived using Lagrange equation and f...A fuzzy robust path tracking strategy of an active pelagic trawl system with ship and winch regulation is proposed.First,nonlinear mathematic model of the pelagic trawl system was derived using Lagrange equation and further simplified as a low order model for the convenience of controller design.Then,an active path tracking strategy of pelagic trawl system was investigated to improve the catching efficiency of the target fish near the sea bottom.By means of the active tracking control,the pelagic trawl net can be positioned dynamically to follow a specified trajectory via the coordinated winch and ship regulation.In addition,considering the system nonlinearities,modeling uncertainties and the unknown exogenous disturbance of the trawl system model,a nonlinear robust H2 /H∞ controller based on Takagi-Sugeno(T-S) fuzzy model was presented,and the simulation comparison with linear robust H2 /H∞ controller and PID method was conducted for the validation of the nonlinear fuzzy robust controller.The nonlinear simulation results show that the average tracking error is 0.4 m for the fuzzy robust H2 /H∞ control and 125.8 m for the vertical and horizontal displacement,respectively,which is much smaller than linear H2 /H∞ controller and the PID controller.The investigation results illustrate that the fuzzy robust controller is effective for the active path tracking control of the pelagic trawl system.展开更多
The aim of this research is to develop an algorithm and application that can perform real-time monitoring of the safety operation of offshore platforms and subsea gas pipelines as well as determine the need for ship i...The aim of this research is to develop an algorithm and application that can perform real-time monitoring of the safety operation of offshore platforms and subsea gas pipelines as well as determine the need for ship inspection using data obtained from automatic identification system(AIS).The research also focuses on the integration of shipping database,AIS data,and others to develop a prototype for designing a real-time monitoring system of offshore platforms and pipelines.A simple concept is used in the development of this prototype,which is achieved by using an overlaying map that outlines the coordinates of the offshore platform and subsea gas pipeline with the ship’s coordinates(longitude/latitude)as detected by AIS.Using such information,we can then build an early warning system(EWS)relayed through short message service(SMS),email,or other means when the ship enters the restricted and exclusion zone of platforms and pipelines.The ship inspection system is developed by combining several attributes.Then,decision analysis software is employed to prioritize the vessel’s four attributes,including ship age,ship type,classification,and flag state.Results show that the EWS can increase the safety level of offshore platforms and pipelines,as well as the efficient use of patrol boats in monitoring the safety of the facilities.Meanwhile,ship inspection enables the port to prioritize the ship to be inspected in accordance with the priority ranking inspection score.展开更多
External forces of marine weather, such as waves, currents and wind flows, affect the course and speed of a ship under way. As a result, marine accidents, such as collisions or grounding, may occur, particularly in in...External forces of marine weather, such as waves, currents and wind flows, affect the course and speed of a ship under way. As a result, marine accidents, such as collisions or grounding, may occur, particularly in inshore areas. On coasts where earthquakes and tsunamis occur frequently, such as the Japanese coast, a tsunami that advances into a bay from the open sea is influenced by the submarine topography. It grows into a huge wave that could cause tremendous damage to ships under way and at anchorage. A massive earthquake occurred in the Tohoku and Kanto regions of Japan on March 11,2011. In response, a tsunami alert, a tsunami warning and an advisory were issued for the entire Pacific coast region. This research investigates the evacuation behaviour of ships by AIS （automatic identification system） data in Tokyo Bay after the tsunami warning was issued. The unusual behaviour observed was attributed to the emergency evacuation of ships.展开更多
The head-on collision process between ship and concrete pile supported protective system is simulated by software LS-DYNA. The influences of pile non-linearity and soil non-linearity on impact force, ship crush depth ...The head-on collision process between ship and concrete pile supported protective system is simulated by software LS-DYNA. The influences of pile non-linearity and soil non-linearity on impact force, ship crush depth and the cap displacement of pile supported protective system are discussed. It's shown that for both severe impact case and non-severe impact case, the non-linearity of pile material influence the impact force history, ship crush depth. The non-linearity of pile material and soil has remarkable influence on the cap displacement especially for severe impact case. These issues should not be ignored in the analysis of pile supported protective system subjected to ship impact.展开更多
This paper aims to evaluate the feasibility of pressure-dependent models in the design of ship piping systems.For this purpose,a complex ship piping system is designed to operate in firefighting and bilge services thr...This paper aims to evaluate the feasibility of pressure-dependent models in the design of ship piping systems.For this purpose,a complex ship piping system is designed to operate in firefighting and bilge services through jet pumps.The system is solved as pressure-dependent model by the piping system analysis software EPANET and by a mathematical approach involving a piping network model.This results in a functional system that guarantees the recommendable ranges of hydraulic state variables(flow and pressure)and compliance with the rules of ship classification societies.Through this research,the suitability and viability of pressure-dependent models in the simulation of a ship piping system are proven.展开更多
Water transportation today has become increasingly busy because of economic globalization.In order to solve the problem of inaccurate port traffic flow prediction,this paper proposes an algorithm based on gated recurr...Water transportation today has become increasingly busy because of economic globalization.In order to solve the problem of inaccurate port traffic flow prediction,this paper proposes an algorithm based on gated recurrent units(GRUs)and Markov residual correction to pass a fixed cross-section.To analyze the traffic flow of ships,the statistical method of ship traffic flow based on the automatic identification system(AIS)is introduced.And a model is put forward for predicting the ship flow.According to the basic principle of cyclic neural networks,the law of ship traffic flow in the channel is explored in the time series.Experiments have been performed using a large number of AIS data in the waters near Xiazhimen in Zhoushan,Ningbo,and the results show that the accuracy of the GRU-Markov algorithm is higher than that of other algorithms,proving the practicability and effectiveness of this method in ship flow prediction.展开更多
This paper presents the test of a ship model for the design of a backward-bent duct oscillating water column type wave energy conversion system, to supply electric power for a light ship. This system suggests a new wa...This paper presents the test of a ship model for the design of a backward-bent duct oscillating water column type wave energy conversion system, to supply electric power for a light ship. This system suggests a new way to produce electric power automatically for large light ships.展开更多
Naval ship deperming is effective to reduce the potential damage from sea mines some of which sense magnetic field of the ship, and thus, is an important treatment of naval ships in the recent world. Large electric cu...Naval ship deperming is effective to reduce the potential damage from sea mines some of which sense magnetic field of the ship, and thus, is an important treatment of naval ships in the recent world. Large electric current is required to impose the magnetic field on the ship hull, which in turn means that the deperming coil needs to be wound on ship hull when the coil is composed of conventional conductive materials, such as copper. We considered a few HTS （high temperature superconducting） coil systems to deperm naval ships because we expect the shorter deperming time and lower manual workload for ship deperming operation, compared conventional conductor coil systems. We have in the past presented a solution using a fiat two-coil system arranged on seabed with tightly bound HTS conductor by analytical calculation of magnetic field on the conductor. By considering present and already developed technologies, a conductor with cylindrically wound on the core arranged as fiat multi-turn coils on seabed was designed using analytical methods.展开更多
文摘Maintenance decision problems generally involve multiple criteria which apparently are best addressed using Multi-Criteria Decision Making (MCDM) tools. This paper describes the use of a hybrid MCDM technique in prioritizing maintenance strategy for ship systems. The Hybrid MCDM technique combines Delphi method, AHP and TOPSIS methods. While the Delphi method and AHP are applied in screening of decision criteria and decision criteria weights determination respectively, the TOPSIS method is used in the ranking of alternative maintenance strategies. Five alternative maintenance strategies which include corrected maintenance, scheduled overhaul, scheduled replacement, continuous on-condition task and scheduled on-condition task are considered and the optimum maintenance strategy is selected based on twelve critical maintenance decision criteria. To demonstrate the suitability of the approach a case study of sea water pump of the central cooling system of a marine diesel engine is used.
基金supported by the National Natural Science Foundation of China(Grant No.52176013)the Shanghai Intergovernmental International Cooperation Project,China(No.23160710200)+1 种基金the National Science and Technology Major Project,China(No.J2019-I0012-0012)the UK Royal Society,China(Grant No.IES\R3\213195).
文摘The solid oxide fuel cell(SOFC)power system fueled by NH_(3)is considered one of the most promising solutions for achieving ship decarbonization and carbon neutrality.This paper addresses the technical challenges faced by NH_(3)fuel SOFC ship power system,including slow hydrogen(H2)production,low efficiency,and limited space.It introduces an innovative a NH_(3)-integrated reactor for rapid H2 production,establishes a safe and efficient all-electric SOFC all-electric propulsion system adaptable to various sailing conditions.The system is validated using a 2 kW prototype experimental rig.Results show that the SOFC system,designed for a target ship,has a rated power of 96 kW and an electrical efficiency of 60.13%,meeting the requirements for rated cruising conditions.Under identical catalytic scenarios,the designed reactor,with highly efficient heat transfer,measuring 1.1 m in length,can achieve complete NH_(3)decomposition within 2.94 s,representing a 35%reduction in cracking time and a 42%decrease in required cabin space.During high-load voyage conditions,adjusting the circulation ratio(CR)and ammonia-oxygen ratio(A/O)improves system efficiency across a wide operational range.Among these adjustments,altering the A/O ratio proves to be the most efficient strategy.Under this configuration,the system achieves an efficiency of 55.02%at low load and 61.73%at high load,allowing operation across a power range of 20%to 110%.Experimental results indicate that the error for NH_(3)cracking H2 is less than 3%within the range of 570-700℃,which is relevant to typical ship operation scenarios.At 656℃,the NH_(3)cracking H2 rate reaches 100%.Under these conditions,the SOFC produces 2.045 kW of power with an efficiency of approximately 58.66%.The noise level detected is 58.6 dB,while the concentrations of CO_(2),NO,and SO_(2)in the flue gas approach zero.These findings support the transition of the shipping industry to green,clean systems,contributing significantly to future reductions in ocean carbon emissions.
文摘Multivariables, strong coupling, nonlinearity, and large delays characterize the boiler-turbine coordinated control systems for ship power equipment. To better deal with these conditions, a compound control strategy based on a support vector machine （SVM） with inverse identification was proposed and applied to research simulating coordinated control systems. This method combines SVM inverse control and fuzzy control, taking advantage of the merits of SVM inverse controls which can be designed easily and have high reliability, and those of fuzzy controls, which respond rapidly and have good anti-jamming capability and robustness. It ensures the controller can be controlled with near instantaneous adjustments to maintain a steady state, even if the SVM is not trained well. The simulation results show that the control quality of this fuzzy-SVM compound control algorithm is high, with good performance in dynamic response speed, static stability, restraint of overshoot, and robustness.
基金financially supported by the National Natural Science Foundation of China(Grant No.51279106)the Special Research Fund for the Doctoral Program of Higher Education of China(Grant No.20110073110009)
文摘Based on support vector machines, three modeling methods, i.e., white-box modeling, grey-box modeling and black-box modeling of ship manoeuvring motion in 4 degrees of freedom are investigated. With the whole-ship mathematical model for ship manoeuvring motion, in which the hydrodynamic coefficients are obtained from roll planar motion mechanism test, some zigzag tests and turning circle manoeuvres are simulated. In the white-box modeling and grey-box modeling, the training data taken every 5 s from the simulated 20°/20° zigzag test are used, while in the black-box modeling, the training data taken every 5 s from the simulated 15°/15°, 20°/20° zigzag tests and 15°, 25° turning manoeuvres are used; and the trained support vector machines are used to predict the whole 20°/20° zigzag test. Comparisons between the simulated and predicted 20°/20° zigzag tests show good predictive ability of the proposed methods. Besides, all mathematical models obtained by the proposed modeling methods are used to predict the 10°/10° zigzag test and 35° turning circle manoeuvre, and the predicted results are compared with those of simulation tests to demonstrate the good generalization performance of the mathematical models. Finally, the proposed modeling methods are analyzed and compared with each other in aspects of application conditions, prediction accuracy and computation speed. The appropriate modeling method can be chosen according to the intended use of the mathematical models and the available data needed for system identification.
基金supported by the Weapon Equipment Research Foundation in Advance(514090909HT0141).
文摘The transfer alignment problem of the shipborne weapon inertial navigation system （INS） is addressed. Specifically, two transfer alignment algorithms subjected to the ship motions induced by the waves are discussed. To consider the limited maneuver level performed by the ship, a new filter algorithm for transfer alignment methods using velocity and angular rate matching is first derived. And then an improved method using integrated velocity and integrated angular rate matching is introduced to reduce the effect of the ship body flexure. The simulation results show the feasibility and validity of the proposed transfer alignment algorithms.
文摘Because the general object of ship steering control system is singular, the state Of rudder force and the state of disturbance are separated, and the generalized yaw output disturhance is obtained. Furthermore, singular system control problem of ship yaw and sway coupled system is transferred into nonsingular standard control problem. Then according to the linear fractional denoting algorithm of the rational function parameter perturbation system, the Linear Fractional Transform （LFT） model of yaw and sway coupled motion is solved, which is used to design the ship steering robust control system. For the ship steering system with the uncertain parameters, the robust control law is designed based on H^∞ μ-synthesis. And the robust performance of the system is analyzed and the simulation validation is made. Simulation results show that the designed control system has excellent control effect and robustness.
基金Supported by the Natural Science Foundation of China under Grant No.50675162the Program of Introducing Talents of Discipline to Universities under Grant No.B08031the Key Project of Hubei Province Science & Technology Fund under Grant No.2008CAD027
文摘Thrust bearing is a key component of the propulsion system of a ship. It transfers the propulsive forces from the propeller to the ship＇s hull, allowing the propeller to push the ship ahead. The performance of a thrust bearing pad is critical. When the thrust bearing becomes damaged, it can cause the ship to lose power and can also affect its operational safety. For this paper, the distribution of the pressure field of a thrust pad was calculated with numerical method, applying Reynolds equation. Thrust bearing properties for loads were analyzed, given variations in outlet thickness of the pad and variations between the load and the slope of the pad. It was noticed that the distribution of pressure was uneven. As a result, increases of both the outlet thickness and the slope coefficient of the pad were able to improve load beating capability.
基金the National Natural Science Foundation of China(50309018).
文摘Common effect of wave and slip of internal heavy load will make rolling of the roll-on ship serious. This is one of the important reasons for overturn of ro-ro ships. The multibodies System with a floating base is composed of ro-ro ship and slipping heavy load. This paper takes the rolling angle of the ship and the transverse displacement of the heavy load on desk as two freedoms. Making use of analysis of apparent gravitation and apparent buoyancy, the wave rolling moment is derived. By use of dynamic method of multibodies system with a floating base, dynamic equations of the system are established. Taking a certain channel ferry as an example, a set of numerical calculation have been carried out for rolling response of the ship and displacement response of the slipping heavy load under common effect of synchro-slipping heavy loads and wave.
基金supported by the National Natural Science Foundation of China (4177402141974005)。
文摘Electric power is widely used as the main energy source of ship integrated power system(SIPS), which contains power network and electric power network. SIPS network reconfiguration is a non-linear large-scale problem. The reconfiguration solution influences the safety and stable operation of the power system. According to the operational characteristics of SIPS, a simplified model of power network and a mathematical model for network reconfiguration are established. Based on these models, a multi-agent and ant colony optimization(MAACO) is proposed to solve the problem of network reconfiguration. The simulations are carried out to demonstrate that the optimization method can reconstruct the integrated power system network accurately and efficiently.
基金This research is supported by the National Natural Science Foundation of China(72071173,71831008,and 72025103).
文摘1.Introduction Maritime transport is the backbone of international trade.The amount of total international maritime trade in million tonnes loaded was 8408 in 2012 and had increased to 11076 by 2019,for an average annual increase of 3.12%.In early 2020,the world fleet contained 98140 ships of 100 gross tonnes and above with 2.06 million dead weight tonnage of capacity[1].The greenhouse gas(GHG)emissions from shipping activities are not negligible.According to the fourth GHG study commissioned by the International Maritime Organization(IMO),in 2018,global shipping emitted a total of 1056 million tonnes of carbon dioxide(CO_(2)),accounting for around 2.89%of global anthropogenic CO_(2) emissions[2].Due to the international nature of shipping,efforts to control CO_(2) emissions from ships are absent from the Kyoto Protocol and the Paris Agreement.In an attempt to phase out carbon emissions from shipping entirely,the IMO formulated a strategy to cut the total annual GHG emissions from shipping by at least 50%from their 2008 levels by 2050[3];however,no mandatory rules have been promulgated since the release of this strategy.
基金the National Natural Science Foundation ofChina (60974136)
文摘A terminal sliding mode fuzzy control based on multiple sliding surfaces was proposed for ship course tracking steering, which takes account of rudder characteristics and parameter uncertainty. In order to solve the problem, the controller was designed by employing the universal approximation property of fuzzy logic system, the advantage of Nussbaum function, and using multiple sliding mode control algorithm based on the recursive technique. In the last step of designing, a nonsingular terminal sliding mode was utilized to drive the last state of the system to converge in a finite period of time, and high-order sliding mode control law was designed to eliminate the chattering and make the system robust. The simulation results showed that the controller designed here could track a desired course fast and accurately. It also exhibited strong robustness peculiarly to system, and had better adaptive ability than traditional PID control algorithms.
基金Project(2009AA045004)supported by the Hi-tech Research and Development Program of China
文摘A fuzzy robust path tracking strategy of an active pelagic trawl system with ship and winch regulation is proposed.First,nonlinear mathematic model of the pelagic trawl system was derived using Lagrange equation and further simplified as a low order model for the convenience of controller design.Then,an active path tracking strategy of pelagic trawl system was investigated to improve the catching efficiency of the target fish near the sea bottom.By means of the active tracking control,the pelagic trawl net can be positioned dynamically to follow a specified trajectory via the coordinated winch and ship regulation.In addition,considering the system nonlinearities,modeling uncertainties and the unknown exogenous disturbance of the trawl system model,a nonlinear robust H2 /H∞ controller based on Takagi-Sugeno(T-S) fuzzy model was presented,and the simulation comparison with linear robust H2 /H∞ controller and PID method was conducted for the validation of the nonlinear fuzzy robust controller.The nonlinear simulation results show that the average tracking error is 0.4 m for the fuzzy robust H2 /H∞ control and 125.8 m for the vertical and horizontal displacement,respectively,which is much smaller than linear H2 /H∞ controller and the PID controller.The investigation results illustrate that the fuzzy robust controller is effective for the active path tracking control of the pelagic trawl system.
文摘The aim of this research is to develop an algorithm and application that can perform real-time monitoring of the safety operation of offshore platforms and subsea gas pipelines as well as determine the need for ship inspection using data obtained from automatic identification system(AIS).The research also focuses on the integration of shipping database,AIS data,and others to develop a prototype for designing a real-time monitoring system of offshore platforms and pipelines.A simple concept is used in the development of this prototype,which is achieved by using an overlaying map that outlines the coordinates of the offshore platform and subsea gas pipeline with the ship’s coordinates(longitude/latitude)as detected by AIS.Using such information,we can then build an early warning system(EWS)relayed through short message service(SMS),email,or other means when the ship enters the restricted and exclusion zone of platforms and pipelines.The ship inspection system is developed by combining several attributes.Then,decision analysis software is employed to prioritize the vessel’s four attributes,including ship age,ship type,classification,and flag state.Results show that the EWS can increase the safety level of offshore platforms and pipelines,as well as the efficient use of patrol boats in monitoring the safety of the facilities.Meanwhile,ship inspection enables the port to prioritize the ship to be inspected in accordance with the priority ranking inspection score.
文摘External forces of marine weather, such as waves, currents and wind flows, affect the course and speed of a ship under way. As a result, marine accidents, such as collisions or grounding, may occur, particularly in inshore areas. On coasts where earthquakes and tsunamis occur frequently, such as the Japanese coast, a tsunami that advances into a bay from the open sea is influenced by the submarine topography. It grows into a huge wave that could cause tremendous damage to ships under way and at anchorage. A massive earthquake occurred in the Tohoku and Kanto regions of Japan on March 11,2011. In response, a tsunami alert, a tsunami warning and an advisory were issued for the entire Pacific coast region. This research investigates the evacuation behaviour of ships by AIS （automatic identification system） data in Tokyo Bay after the tsunami warning was issued. The unusual behaviour observed was attributed to the emergency evacuation of ships.
文摘The head-on collision process between ship and concrete pile supported protective system is simulated by software LS-DYNA. The influences of pile non-linearity and soil non-linearity on impact force, ship crush depth and the cap displacement of pile supported protective system are discussed. It's shown that for both severe impact case and non-severe impact case, the non-linearity of pile material influence the impact force history, ship crush depth. The non-linearity of pile material and soil has remarkable influence on the cap displacement especially for severe impact case. These issues should not be ignored in the analysis of pile supported protective system subjected to ship impact.
文摘This paper aims to evaluate the feasibility of pressure-dependent models in the design of ship piping systems.For this purpose,a complex ship piping system is designed to operate in firefighting and bilge services through jet pumps.The system is solved as pressure-dependent model by the piping system analysis software EPANET and by a mathematical approach involving a piping network model.This results in a functional system that guarantees the recommendable ranges of hydraulic state variables(flow and pressure)and compliance with the rules of ship classification societies.Through this research,the suitability and viability of pressure-dependent models in the simulation of a ship piping system are proven.
文摘Water transportation today has become increasingly busy because of economic globalization.In order to solve the problem of inaccurate port traffic flow prediction,this paper proposes an algorithm based on gated recurrent units(GRUs)and Markov residual correction to pass a fixed cross-section.To analyze the traffic flow of ships,the statistical method of ship traffic flow based on the automatic identification system(AIS)is introduced.And a model is put forward for predicting the ship flow.According to the basic principle of cyclic neural networks,the law of ship traffic flow in the channel is explored in the time series.Experiments have been performed using a large number of AIS data in the waters near Xiazhimen in Zhoushan,Ningbo,and the results show that the accuracy of the GRU-Markov algorithm is higher than that of other algorithms,proving the practicability and effectiveness of this method in ship flow prediction.
文摘This paper presents the test of a ship model for the design of a backward-bent duct oscillating water column type wave energy conversion system, to supply electric power for a light ship. This system suggests a new way to produce electric power automatically for large light ships.
文摘Naval ship deperming is effective to reduce the potential damage from sea mines some of which sense magnetic field of the ship, and thus, is an important treatment of naval ships in the recent world. Large electric current is required to impose the magnetic field on the ship hull, which in turn means that the deperming coil needs to be wound on ship hull when the coil is composed of conventional conductive materials, such as copper. We considered a few HTS （high temperature superconducting） coil systems to deperm naval ships because we expect the shorter deperming time and lower manual workload for ship deperming operation, compared conventional conductor coil systems. We have in the past presented a solution using a fiat two-coil system arranged on seabed with tightly bound HTS conductor by analytical calculation of magnetic field on the conductor. By considering present and already developed technologies, a conductor with cylindrically wound on the core arranged as fiat multi-turn coils on seabed was designed using analytical methods.
