Time?variant excitations in planetary gear trains can cause excessive noise and vibration and even damage the system on a permanent basis. This paper focuses on the elastic vibrations of a helical planetary ring gear ...Time?variant excitations in planetary gear trains can cause excessive noise and vibration and even damage the system on a permanent basis. This paper focuses on the elastic vibrations of a helical planetary ring gear subjected to mesh and planet?pass excitations. Motivated by the structure, excitation and deformation symmetries, this paper proposes dual?frequency superposition and modulation methods to capture the mesh and sideband vibrations. The transi?tion between ring gear tooth and planet is introduced to address the excitations and vibrations. The phasing e ect of ring gear tooth and planet on various deformations is formulated. The inherent connections between the two types of vibrations are identified. The vibrations share identical exciting rules and the wavenumber and modulating signal order both equal the linear combination of tooth and planet counts. The results cover in?plane bending and extensional, out?of?plane bending and torsional deformations. Main findings are verified by numerical calculation and comparisons with the open literature. The analytical expressions can be used to determine whether the sideband is caused by component fault or only by elastic vibration. The methods can be extended to other power?transmission systems because little restriction is imposed during the analysis.展开更多
Due to low carrying capacity and short life of current ring reducer,we proposed a new planetary gearing with internal gear ring,which consisted of two stages.One was an involute planetary drive and the other was an N-...Due to low carrying capacity and short life of current ring reducer,we proposed a new planetary gearing with internal gear ring,which consisted of two stages.One was an involute planetary drive and the other was an N-type planetary drive with small teeth difference.The kinematic calculation was conducted based on the analysis of structural composition and working principle.Formulas of backlash calculation for the new planetary gearing were derived by using probabilistic theory and the analytical model was created at the same time.Then,main factors that affect the systematic backlash were introduced and the effects of manufacture error,misaligments and roller bearing parameters on the distribution of backlash were presented.The influence of gear backlash on systematic return difference was performed based on the backlash mathematic model proposed.The results show that the backlash is a little large,of which the backlash of bearing takes a greater part than two gearing stages.So we presented some practical methods to reduce the systematic backlash.展开更多
Jupiter is one of the major targets for planetary exploration,and dust in the Jovian system is of great interest to researchers in the field of planetary science.In this paper,we review the five dust populations outsi...Jupiter is one of the major targets for planetary exploration,and dust in the Jovian system is of great interest to researchers in the field of planetary science.In this paper,we review the five dust populations outside the ring system:grains in the region of the Galilean moons,potential dust from plumes on Europa,Jovian stream particles,particles in the outer region of the Jovian system ejected from the irregular satellites,and dust in the region of the Trojan asteroids.The physical environment for the dust dynamics is described,including the gravity,the magnetic field and the plasma environment.For each population,the dust sources are described,and the relevant perturbation forces are discussed.Observations and results from modeling are reviewed,and the distributions of the individual dust populations are shown.The understanding of the Jovian dust environment allows to assess the dust hazard to spacecraft,and to characterize the material exchange between the Jovian moons,their surface properties and distribution of non-icy constituents.展开更多
基金National Natural Science Foundation of China(Grant Nos.51175370,51675368)Application of Basic Research and Frontier Technology Research Key Projects of Tianjin,China(Grant No.13JCZDJC34300)National Basic Research Program of China(973 Program,Grant No.2013CB035402)
文摘Time?variant excitations in planetary gear trains can cause excessive noise and vibration and even damage the system on a permanent basis. This paper focuses on the elastic vibrations of a helical planetary ring gear subjected to mesh and planet?pass excitations. Motivated by the structure, excitation and deformation symmetries, this paper proposes dual?frequency superposition and modulation methods to capture the mesh and sideband vibrations. The transi?tion between ring gear tooth and planet is introduced to address the excitations and vibrations. The phasing e ect of ring gear tooth and planet on various deformations is formulated. The inherent connections between the two types of vibrations are identified. The vibrations share identical exciting rules and the wavenumber and modulating signal order both equal the linear combination of tooth and planet counts. The results cover in?plane bending and extensional, out?of?plane bending and torsional deformations. Main findings are verified by numerical calculation and comparisons with the open literature. The analytical expressions can be used to determine whether the sideband is caused by component fault or only by elastic vibration. The methods can be extended to other power?transmission systems because little restriction is imposed during the analysis.
基金Funded by Key Technology R&D Program of Chongqing(No. 2008AC3087)Science & Technology Project of Chongqing Education Committee(No. KJ091414)
文摘Due to low carrying capacity and short life of current ring reducer,we proposed a new planetary gearing with internal gear ring,which consisted of two stages.One was an involute planetary drive and the other was an N-type planetary drive with small teeth difference.The kinematic calculation was conducted based on the analysis of structural composition and working principle.Formulas of backlash calculation for the new planetary gearing were derived by using probabilistic theory and the analytical model was created at the same time.Then,main factors that affect the systematic backlash were introduced and the effects of manufacture error,misaligments and roller bearing parameters on the distribution of backlash were presented.The influence of gear backlash on systematic return difference was performed based on the backlash mathematic model proposed.The results show that the backlash is a little large,of which the backlash of bearing takes a greater part than two gearing stages.So we presented some practical methods to reduce the systematic backlash.
基金the European Space Agency under the project“Jovian Micrometeoroid Environment Model”(JMEM)(Contract No.4000107249/12/NL/AF)at the University of Oulu,and by the Academy of Finland under the project“Earth and Near-Space System and Environmental Change”.
文摘Jupiter is one of the major targets for planetary exploration,and dust in the Jovian system is of great interest to researchers in the field of planetary science.In this paper,we review the five dust populations outside the ring system:grains in the region of the Galilean moons,potential dust from plumes on Europa,Jovian stream particles,particles in the outer region of the Jovian system ejected from the irregular satellites,and dust in the region of the Trojan asteroids.The physical environment for the dust dynamics is described,including the gravity,the magnetic field and the plasma environment.For each population,the dust sources are described,and the relevant perturbation forces are discussed.Observations and results from modeling are reviewed,and the distributions of the individual dust populations are shown.The understanding of the Jovian dust environment allows to assess the dust hazard to spacecraft,and to characterize the material exchange between the Jovian moons,their surface properties and distribution of non-icy constituents.
