Ship maneuvering in waves includes the performance of ship resistance, seakeeping, propulsion, and maneuverability. It is a complex hydrodynamic problem with the interaction of many factors. With the purpose of direct...Ship maneuvering in waves includes the performance of ship resistance, seakeeping, propulsion, and maneuverability. It is a complex hydrodynamic problem with the interaction of many factors. With the purpose of directly predicting the behavior of ship maneuvering in waves, a CFD solver named naoe-FOAM-SJTU is developed by the Computational Marine Hydrodynamics Lab(CMHL) in Shanghai Jiao Tong University. The solver is based on open source platform OpenFOAM and has introduced dynamic overset grid technology to handle complex ship hull-propeller-rudder motion system. Maneuvering control module based on feedback control mechanism is also developed to accurately simulate corresponding motion behavior of free running ship maneuver. Inlet boundary wavemaker and relaxation zone technique is used to generate desired waves. Based on the developed modules, unsteady Reynolds-averaged Navier-Stokes(RANS) computations are carried out for several validation cases of free running ship maneuver in waves including zigzag, turning circle, and course keeping maneuvers. The simulation results are compared with available benchmark data. Ship motions, trajectories, and other maneuvering parameters are consistent with available experimental data, which indicate that the present solver can be suitable and reliable in predicting the performance of ship maneuvering in waves. Flow visualizations, such as free surface elevation, wake flow, vortical structures, are presented to explain the hydrodynamic performance of ship maneuvering in waves. Large flow separation can be observed around propellers and rudders. It is concluded that RANS approach is not accurate enough for predicting ship maneuvering in waves with large flow separations and detached eddy simulation(DES) or large eddy simulation(LES) computations are required to improve the prediction accuracy.展开更多
鉴于洋山港在上海国际航运中心建设的地位及超大型船舶航行与应急条件有限的实际情况,超大型油轮(Very Large Crude Carry VLCC)进靠该港口石油储运码头存在很多不确定的因素和风险。为了确保港口设施和船舶的安全,根据港口的实际情况...鉴于洋山港在上海国际航运中心建设的地位及超大型船舶航行与应急条件有限的实际情况,超大型油轮(Very Large Crude Carry VLCC)进靠该港口石油储运码头存在很多不确定的因素和风险。为了确保港口设施和船舶的安全,根据港口的实际情况和引领超大型船舶的经验与体会,就VLCC在洋山港航行和靠离操纵方法进行论述,强调了此类船舶在航行与靠离作业的注意事项。同时,结合引领VLCC"枫林湾"轮的深切体会,对洋山港石油储运码头附近的安全保证和VLCC安全靠泊的时机等进行了探讨。展开更多
In order to achieve a straight ballistic trajectory of missile and reduce the update frequency of the missile normal acceleration for the interception of maneuvering target,a backstepping-based parallel approaching gu...In order to achieve a straight ballistic trajectory of missile and reduce the update frequency of the missile normal acceleration for the interception of maneuvering target,a backstepping-based parallel approaching guidance method is designed with nonlinear disturbance observer(NDO)technique and event-triggered(ET)mechanism in this paper.In order to suppress the adverse e®ect of target maneuver,the NDO is designed to estimate the target maneuvering acceleration.Then,the NDO-based backstepping method is used to obtain the normal acceleration of missile and realize the parallel approaching guidance.In order to reduce the update frequency of missile normal acceleration,the ET mechanism is employed in the parallel approaching guidance method.If the missile trajectory is relatively straight,the normal acceleration of missile remains unchanged.On the contrary,if the missile trajectory is not straight,the normal acceleration of missile is updated to make the missile trajectory straight.In this way,the ET-based parallel approaching guidance can be obtained.Furthermore,a determined method for the initial missile°ight-path angle is proposed to keep the normal acceleration of missile at zero in the initial stage of interception.Besides,Lyapunov stability analysis method is used to prove that all signals in the closed-loop guidance system are uniformly ultimately bounded.Finally,simulation results show the e®ectiveness of the proposed guidance method.展开更多
This paper deals with the adaptive practical output maneuvering control problems for a class of nonlinear systems with uncontrollable unstable linearization. The objective is to design a smooth adaptive maneuvering co...This paper deals with the adaptive practical output maneuvering control problems for a class of nonlinear systems with uncontrollable unstable linearization. The objective is to design a smooth adaptive maneuvering controller to solve the geometric and dynamic tasks with an arbitrary small steady tracking error. The method of adding a power integrator and the robust recursive design technique are employed to force the system output to track a desired path and make the tracking speed to follow a desired speed along the path. An example is considered and simulation results are given. The proposed design procedure can be illustrated by the use of this example.展开更多
The Dash Stop flight at the extreme condition is the primary interest of this study. This paper describes some research on the flight characteristics of helicopter in Dash Stop. A set of equations which govern the Das...The Dash Stop flight at the extreme condition is the primary interest of this study. This paper describes some research on the flight characteristics of helicopter in Dash Stop. A set of equations which govern the Dash Stop is developed. A method which determines the acceleration and deceleration is proposed. Formulas are then developed which relate the aircraft angular rates and attitudes to flight speed, angle of attack and acceleration or deceleration. Finally the DOLPHIN helicopter is taken as an example to calculate its acceleration/deceleration capability, pilot control and aircraft attitudes in space. It is found that the results are reasonable.展开更多
Ship maneuverability, in the field of ship engineering, is often predicted by maneuvering motion group （MMG） mathematical model. Then it is necessary to determine hydrodynamic coefficients and interaction force coef...Ship maneuverability, in the field of ship engineering, is often predicted by maneuvering motion group （MMG） mathematical model. Then it is necessary to determine hydrodynamic coefficients and interaction force coefficients of the model. Based on the data of free running model test, the problem for obtaining these coefficients is called inverse one. For the inverse problem, ill-posedness is inherent, nonlinearity and great computation happen, and the computation is also insensitive, unstable and time-consuming. In the paper, a regularization method is introduced to solve ill-posed problem and genetic algorithm is used for nonlinear motion of ship maneuvering. In addition, the immunity is applied to solve the prematurity, to promote the global searching ability and to increase the converging speed. The combination of regularization method and immune genetic algorithm（RIGA） applied in MMG mathematical model, showed rapid converging speed and good stability.展开更多
Based on the stress-strain data collected by a CSSMAS （container ship structure monitoring and analyzing system） onboard a container vessel, stress-strain responses of the ship＇s structure in high wave were analyze...Based on the stress-strain data collected by a CSSMAS （container ship structure monitoring and analyzing system） onboard a container vessel, stress-strain responses of the ship＇s structure in high wave were analyzed and illustrated for the identification of reasonable safe course sections. Besides the ship＇s structure safety, the maneuvering convenience is also deemed as a main concern which influences the safety of vessels in heavy waves. In order to develop a comprehensive guidance in adverse weather condition, the basic requirements on maneuvering convenience for vessels in storm were further discussed. In combination of the two requirements, namely structure health and maneuvering convenience, a proposed operational method was thus developed, which was an amendment to the traditional navigational method for ship in extreme weather. At the end of this paper, an example of optimal course planning in bad weather was illustrated by using the operational method proposed.展开更多
基金the National Natural Science Foundation of China (51809169,51879159,51490675,11432009, 51579145)Chang Jiang Scholars Program (T2014099)+2 种基金Shanghai Excellent Academic Leaders Program (17XD1402300)Program for Professor of Special Appointment (Eastern Scholar)at Shanghai Institutions of Higher Learning (2013022)Innovative Special Project of Numerical Tank of Ministry of Industry and Information Technology of China (2016-23/09).
文摘Ship maneuvering in waves includes the performance of ship resistance, seakeeping, propulsion, and maneuverability. It is a complex hydrodynamic problem with the interaction of many factors. With the purpose of directly predicting the behavior of ship maneuvering in waves, a CFD solver named naoe-FOAM-SJTU is developed by the Computational Marine Hydrodynamics Lab(CMHL) in Shanghai Jiao Tong University. The solver is based on open source platform OpenFOAM and has introduced dynamic overset grid technology to handle complex ship hull-propeller-rudder motion system. Maneuvering control module based on feedback control mechanism is also developed to accurately simulate corresponding motion behavior of free running ship maneuver. Inlet boundary wavemaker and relaxation zone technique is used to generate desired waves. Based on the developed modules, unsteady Reynolds-averaged Navier-Stokes(RANS) computations are carried out for several validation cases of free running ship maneuver in waves including zigzag, turning circle, and course keeping maneuvers. The simulation results are compared with available benchmark data. Ship motions, trajectories, and other maneuvering parameters are consistent with available experimental data, which indicate that the present solver can be suitable and reliable in predicting the performance of ship maneuvering in waves. Flow visualizations, such as free surface elevation, wake flow, vortical structures, are presented to explain the hydrodynamic performance of ship maneuvering in waves. Large flow separation can be observed around propellers and rudders. It is concluded that RANS approach is not accurate enough for predicting ship maneuvering in waves with large flow separations and detached eddy simulation(DES) or large eddy simulation(LES) computations are required to improve the prediction accuracy.
文摘鉴于洋山港在上海国际航运中心建设的地位及超大型船舶航行与应急条件有限的实际情况,超大型油轮(Very Large Crude Carry VLCC)进靠该港口石油储运码头存在很多不确定的因素和风险。为了确保港口设施和船舶的安全,根据港口的实际情况和引领超大型船舶的经验与体会,就VLCC在洋山港航行和靠离操纵方法进行论述,强调了此类船舶在航行与靠离作业的注意事项。同时,结合引领VLCC"枫林湾"轮的深切体会,对洋山港石油储运码头附近的安全保证和VLCC安全靠泊的时机等进行了探讨。
基金supported in part by the National Natural Science Foundation of China under Grants No.62003269Foundation of Science and Technology on Aerospace Flight Dynamics Laboratory(6142210200308).
文摘In order to achieve a straight ballistic trajectory of missile and reduce the update frequency of the missile normal acceleration for the interception of maneuvering target,a backstepping-based parallel approaching guidance method is designed with nonlinear disturbance observer(NDO)technique and event-triggered(ET)mechanism in this paper.In order to suppress the adverse e®ect of target maneuver,the NDO is designed to estimate the target maneuvering acceleration.Then,the NDO-based backstepping method is used to obtain the normal acceleration of missile and realize the parallel approaching guidance.In order to reduce the update frequency of missile normal acceleration,the ET mechanism is employed in the parallel approaching guidance method.If the missile trajectory is relatively straight,the normal acceleration of missile remains unchanged.On the contrary,if the missile trajectory is not straight,the normal acceleration of missile is updated to make the missile trajectory straight.In this way,the ET-based parallel approaching guidance can be obtained.Furthermore,a determined method for the initial missile°ight-path angle is proposed to keep the normal acceleration of missile at zero in the initial stage of interception.Besides,Lyapunov stability analysis method is used to prove that all signals in the closed-loop guidance system are uniformly ultimately bounded.Finally,simulation results show the e®ectiveness of the proposed guidance method.
基金Supported by the National Natural Science Foundation of China （No. 60304003, 60574007, and 60574080）.
文摘This paper deals with the adaptive practical output maneuvering control problems for a class of nonlinear systems with uncontrollable unstable linearization. The objective is to design a smooth adaptive maneuvering controller to solve the geometric and dynamic tasks with an arbitrary small steady tracking error. The method of adding a power integrator and the robust recursive design technique are employed to force the system output to track a desired path and make the tracking speed to follow a desired speed along the path. An example is considered and simulation results are given. The proposed design procedure can be illustrated by the use of this example.
文摘The Dash Stop flight at the extreme condition is the primary interest of this study. This paper describes some research on the flight characteristics of helicopter in Dash Stop. A set of equations which govern the Dash Stop is developed. A method which determines the acceleration and deceleration is proposed. Formulas are then developed which relate the aircraft angular rates and attitudes to flight speed, angle of attack and acceleration or deceleration. Finally the DOLPHIN helicopter is taken as an example to calculate its acceleration/deceleration capability, pilot control and aircraft attitudes in space. It is found that the results are reasonable.
文摘Ship maneuverability, in the field of ship engineering, is often predicted by maneuvering motion group （MMG） mathematical model. Then it is necessary to determine hydrodynamic coefficients and interaction force coefficients of the model. Based on the data of free running model test, the problem for obtaining these coefficients is called inverse one. For the inverse problem, ill-posedness is inherent, nonlinearity and great computation happen, and the computation is also insensitive, unstable and time-consuming. In the paper, a regularization method is introduced to solve ill-posed problem and genetic algorithm is used for nonlinear motion of ship maneuvering. In addition, the immunity is applied to solve the prematurity, to promote the global searching ability and to increase the converging speed. The combination of regularization method and immune genetic algorithm（RIGA） applied in MMG mathematical model, showed rapid converging speed and good stability.
文摘Based on the stress-strain data collected by a CSSMAS （container ship structure monitoring and analyzing system） onboard a container vessel, stress-strain responses of the ship＇s structure in high wave were analyzed and illustrated for the identification of reasonable safe course sections. Besides the ship＇s structure safety, the maneuvering convenience is also deemed as a main concern which influences the safety of vessels in heavy waves. In order to develop a comprehensive guidance in adverse weather condition, the basic requirements on maneuvering convenience for vessels in storm were further discussed. In combination of the two requirements, namely structure health and maneuvering convenience, a proposed operational method was thus developed, which was an amendment to the traditional navigational method for ship in extreme weather. At the end of this paper, an example of optimal course planning in bad weather was illustrated by using the operational method proposed.
