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RISS 인기검색어
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- 저자 : Yunsong Li (검색결과 5 건)
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Dynamics modeling and modal experimental study of high speed motorized spindle
Yunsong Li,Xiaoan Chen,Peng Zhang,Jinming Zhou 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.3
This paper presents a dynamical model of high speed motorized spindles in free state and work state. In the free state, the housing is modeled as a rotor with equivalent masses including bearing pedestals, motor stator and rear end cover. As a consequence, a double rotor dynamics can be modeled for high speed motorized spindles by a bearing element which connects the housing and bearing pedestals. In the work state, the housing is fixed and the system becomes a bearing-rotor dynamical model. An excitation-measurement test in the free state is designed to analyze the cross spectral density and auto spectral density of input and output signals. Then the frequency response function of system and coherence function of input and output signals which are used to analyze the inherent characteristics of the double-rotor model can be obtained. The other vibration test in the work state is designed to research the dynamical supporting characteristics of bearings and the effects from bearings on the inherent characteristics of the system. The good agreement between the experimental data and theoretical results indicates that the dynamical model in two states is capable of accurately predicting the dynamic behavior of high speed motorized spindles.
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H<sub>2</sub>O Adsorption/Desorption in MOF-74: <i>Ab Initio</i> Molecular Dynamics and Experiments
Li, Yunsong,Wang, Xinjiang,Xu, Dongyan,Chung, Jae Dong,Kaviany, Massoud,Huang, Baoling American Chemical Society 2015 The Journal of Physical Chemistry Part C Vol.119 No.23
<P>Using density functional theory based molecular dynamics with the tight-binding approximation and experimental characterization, the H<SUB>2</SUB>O vapor adsorption/desorption processes in Zn-MOF-74 and the corresponding influence on the lattice dynamics were investigated. It was found that the Zn sites are preferred for H<SUB>2</SUB>O adsorption, and they even allow for the adsorption of multiple H<SUB>2</SUB>O molecules on the same site, making it possible to form stable H<SUB>2</SUB>O cluster at low temperatures. The adsorption heats of different adsorption processes were predicted, and the possibility of H<SUB>2</SUB>O cluster formation under vapor exposure at low and room temperatures was explored. The first adsorbed H<SUB>2</SUB>O can only be dissociated at elevated temperatures, therefore reducing the cyclic uptake near the room temperature. The vibrational spectra of the lattice and adsorbed H<SUB>2</SUB>O were also calculated using molecular dynamics simulation to illuminate the variation of lattice dynamics during the adsorption. The framework was found to be stable after water vapor exposure near room temperature but may start to collapse at around 570 K. X-ray diffraction and H<SUB>2</SUB>O adsorption isotherm measurements have been conducted to verify the theoretical predictions, and good agreements are found.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2015/jpccck.2015.119.issue-23/acs.jpcc.5b02069/production/images/medium/jp-2015-02069m_0008.gif'></P>
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Dynamic analysis of a flexure-based compliant stage
Yunsong Du,Tie-Min Li,Guohua Gao 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.11
This paper presents the dynamic analysis of a flexure-based compliant stage. The dynamic model is first obtained, after which the equivalent masses of the flexure hinge, including the axial equivalent mass, the bending equivalent mass, and the shear equivalent mass, are derived. According to this method, the equivalent mass components of the proposed stage are derived by accumulating those of the output platform, input platform, and flexure hinges. Finally, to verify the validity of the proposed method, the first two resonant frequencies and the corresponding mode shapes are analyzed by using finite element analysis (FEA). An experimental platform is fabricated, and experimental results and FEA values appear to be in accordance with the theoretical calculations. This result demonstrates that the dynamic model and equivalent mass are accurate. The dynamic model provides an effective method for calculating equivalent masses, and dynamic characteristics can be precisely estimated from the corresponding analytical models.
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Output decoupling modeling of a XY flexure-based compliant manipulator
Yunsong Du,Tie-Min Li 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.1
This paper presents the coupling stiffness modeling of an XY flexure-based manipulator. Stiffness/compliance equations for compliant mechanisms are first obtained. According to a simplified spring model, the input stiffness and coupling stiffness of the proposed manipulator consisting of outer and inner kinematic chains are then derived. This simplified spring model is composed of four parallel chains, such as the left, lower, upper and right parallel chain. Subsequently, the external force/moment and the output displacement of the manipulator are analyzed by using finite element analysis (FEA). Finally, a prototype of the manipulator is fabricated. Its motion range and the corresponding cross-coupling displacements are measured, and thus the cross-coupling ratios can be derived. It demonstrates that the manipulator possesses good decoupling characteristic, and the proposed theoretical model is reasonable and accurate.
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Evaluate the Gray Code in Distributed Fields for Tracking
Xianyun Wu,Kai Liu,Jinyan Cao,Yunsong Li,Li Wang 보안공학연구지원센터 2016 International Journal of Signal Processing, Image Vol.9 No.11
Distribution Fields (DFs) for tracking achieved a better performance than traditional algorithms due to its special representation that allows smoothing the objective function without destroying information about pixel values. DFs descriptor can satisfy both the specificity and smooth landscape requirements of a good tracking algorithm. In this paper, we evaluate the Gray code in original DFs algorithm by replacing the pixel values using Gray code instead of original binary code. Experimental results show that the Gray code can improve the tracking efficiency in certain way.
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