The configuration boundedness of the three-body model dynamics is studied for Sun-Earth formation flying missions.The three-body formation flying model is built up with considering the lunar gravitational acceleration...The configuration boundedness of the three-body model dynamics is studied for Sun-Earth formation flying missions.The three-body formation flying model is built up with considering the lunar gravitational acceleration and solar radiation pressure.Because traditional linearized dynamics based method has relatively lower accuracy,a modified nonlinear formation configuration analysis method is proposed in this paper.Comparative studies are carried out from three aspects,i.e.,natural formation configuration with arbitrary departure time,initialization time and formation configuration boundedness,and specific initialization time for bounded formation configuration.Simulations demonstrate the differences between the two schemes, and indicate that the nonlinear dynamic method reduces the error caused by the model linearization and disturbance approximation,and thus provides higher accuracy for boundedness analysis,which is of value to initial parameters selection for natural three-body formation flying.展开更多
The dynamic equivalent continuum modeling method of the mast which is based on energy equivalency principle was investigated. And three kinds of mast dynamic model were established, which were equivalent continuum mod...The dynamic equivalent continuum modeling method of the mast which is based on energy equivalency principle was investigated. And three kinds of mast dynamic model were established, which were equivalent continuum model, finite element model and simulation model, respectively. The mast frequencies and mode shapes were calculated by these models and compared with each other. The error between the equivalent continuum model and the finite element model is less than 5% when the mast length is longer. Dynamic responses of the mast with different lengths are tested, the mode frequencies and mode shapes are compared with finite element model. The mode shapes match well with each other, while the frequencies tested by experiments are lower than the results of the finite element model, which reflects the joints lower the mast stiffness. The nonlinear dynamic characteristics are presented in the dynamic responses of the mast under different excitation force levels. The joint nonlinearities in the deployable mast are identified as nonlinear hysteresis contributed by the coulomb friction which soften the mast stiffness and lower the mast frequencies.展开更多
We proposed a dynamic model of DNA to study its nonlinear excitation and duplication and transcription in the basis of molecular structure and changes of conformation of DNA under influence of bioenergy.
为了减小车辆振动,提高车辆乘坐舒适性和操纵稳定性,将惯容器与非线性能量汇相结合,构建惯容非线性能量汇(Nonlinear Energy Sink Inerter,NESI),并将其运用于车辆悬架和座椅悬架,进一步提出一种基于遗传算法的无模型自适应控制方法(Mod...为了减小车辆振动,提高车辆乘坐舒适性和操纵稳定性,将惯容器与非线性能量汇相结合,构建惯容非线性能量汇(Nonlinear Energy Sink Inerter,NESI),并将其运用于车辆悬架和座椅悬架,进一步提出一种基于遗传算法的无模型自适应控制方法(Model-free Adaptive Control,MFAC)。研究了采用MFAC方法的耦合NESI的车-座椅系统在路面随机激励下的动态特性,并与被动系统和比例积分微分(Proportional Integral Derivative,PID)控制系统进行对比。结果表明,与车-座椅被动系统相比,采用MFAC方法的车-座椅系统的车身垂直加速度与座椅垂直加速度均方根值在低中高车速下都显著减小;与PID控制相比,车身垂直加速度、座椅垂直加速度、悬架动行程和轮胎动载荷均方根值在低、中、高车速下都有所降低。展开更多
文摘The configuration boundedness of the three-body model dynamics is studied for Sun-Earth formation flying missions.The three-body formation flying model is built up with considering the lunar gravitational acceleration and solar radiation pressure.Because traditional linearized dynamics based method has relatively lower accuracy,a modified nonlinear formation configuration analysis method is proposed in this paper.Comparative studies are carried out from three aspects,i.e.,natural formation configuration with arbitrary departure time,initialization time and formation configuration boundedness,and specific initialization time for bounded formation configuration.Simulations demonstrate the differences between the two schemes, and indicate that the nonlinear dynamic method reduces the error caused by the model linearization and disturbance approximation,and thus provides higher accuracy for boundedness analysis,which is of value to initial parameters selection for natural three-body formation flying.
基金Projects(50935002, 11002039) supported by the National Natural Science Foundation of ChinaProject(HIT.KLOF.2009062) supported by Key Laboratory Opening Funding of Aerospace Mechanism and Control Technology,Chinasupport by "111 Project" (Grant No.B07018)
文摘The dynamic equivalent continuum modeling method of the mast which is based on energy equivalency principle was investigated. And three kinds of mast dynamic model were established, which were equivalent continuum model, finite element model and simulation model, respectively. The mast frequencies and mode shapes were calculated by these models and compared with each other. The error between the equivalent continuum model and the finite element model is less than 5% when the mast length is longer. Dynamic responses of the mast with different lengths are tested, the mode frequencies and mode shapes are compared with finite element model. The mode shapes match well with each other, while the frequencies tested by experiments are lower than the results of the finite element model, which reflects the joints lower the mast stiffness. The nonlinear dynamic characteristics are presented in the dynamic responses of the mast under different excitation force levels. The joint nonlinearities in the deployable mast are identified as nonlinear hysteresis contributed by the coulomb friction which soften the mast stiffness and lower the mast frequencies.
文摘We proposed a dynamic model of DNA to study its nonlinear excitation and duplication and transcription in the basis of molecular structure and changes of conformation of DNA under influence of bioenergy.
文摘为了减小车辆振动,提高车辆乘坐舒适性和操纵稳定性,将惯容器与非线性能量汇相结合,构建惯容非线性能量汇(Nonlinear Energy Sink Inerter,NESI),并将其运用于车辆悬架和座椅悬架,进一步提出一种基于遗传算法的无模型自适应控制方法(Model-free Adaptive Control,MFAC)。研究了采用MFAC方法的耦合NESI的车-座椅系统在路面随机激励下的动态特性,并与被动系统和比例积分微分(Proportional Integral Derivative,PID)控制系统进行对比。结果表明,与车-座椅被动系统相比,采用MFAC方法的车-座椅系统的车身垂直加速度与座椅垂直加速度均方根值在低中高车速下都显著减小;与PID控制相比,车身垂直加速度、座椅垂直加速度、悬架动行程和轮胎动载荷均方根值在低、中、高车速下都有所降低。
