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Lee, Giuk,Jeong, Jay I.,Kim, Jongwon Marcel Dekker inc. 2016 MECHANICS BASED DESIGN OF STRUCTURES AND MACHINES Vol.44 No.4
<P>This paper presents the kinematic calibration of a two degree-of-freedom redundantly actuated parallel mechanism (RAPM), with the aim of eliminating contradicting control forces (CCF). The kinematic errors in the RAPM induce CCFs, especially in the case of decentralized individual position control, which is the standard control method used in industrial applications. The encoder indexing errors of the actuated joints are known to be of strong influence on the CCFs. Therefore, it is believed that the CCFs will be eliminated if the encoder indexing errors are corrected. We proved this through experiments. We performed the calibration using a projection technique, wherein we projected tracking error terms onto orthogonal complementary terms of the constraint Jacobian between the independent joints and actuated joints. Using this projection technique, the effect of tracking error terms from the joint stiffness and external force is eliminated. During the calibration process, the tracking errors in the actuated joints are measured. Using these errors, we derived the optimal values of the encoder indexing error by minimizing the objective function. We verified the calibration result by comparing the CCFs measured before calibration with those measured after calibration, for the case of individual PID position control. Our results confirmed that the calibration procedure of encoder indexing errors successfully reduces the average norm value of CCFs from 366N to 13N.</P>
Theoretical and Experimental Analysis of Material Deformation by Microcontact
Rae-Hyeong Ryu,Si-Hyung Lim,Jay I. Jeong,Donghoon Shin,Siyoul Jang,Hong Jae Yim,Kee Sung Lee 한국정밀공학회 2009 International Journal of Precision Engineering and Vol.10 No.2
This paper reports on an investigation of contact damage induced in molds and substrate materials used in micro and nanoimprint lithography. Silicon, polydimethylsiloxane (PDMS), glass, and silicon carbide were studied. A finite element analysis using ABAQUS software was conducted to investigate the stress induced in mold and substrate materials when they come in contact with each other at a uniaxial pressure of 1 MPa. A spherical indentation experiment was conducted for a model study for various indentation loads and numbers of contact cycles. We examined the contact damage during the spherical indentation. Indentation stress-strain curves, surface views of contact damage, and mechanical properties were characterized for the mold and substrate materials.
Using Harmonic Analysis and Optimization to Study Macromolecular Dynamics
Moon K. Kim,Yunho Jang,Jay I. Jeong 대한전기학회 2006 International Journal of Control, Automation, and Vol.4 No.3
Mechanical system dynamics plays an important role in the area of computational structural biology. Elastic network models (ENMs) for macromolecules (e.g., polymers, proteins, and nucleic acids such as DNA and RNA) have been developed to understand the relationship between their structure and biological function. For example, a protein, which is basically a folded polypeptide chain, can be simply modeled as a mass-spring system from the mechanical viewpoint. Since the conformational flexibility of a protein is dominantly subject to its chemical bond interactions (e.g., covalent bonds, salt bridges, and hydrogen bonds), these constraints can be modeled as linear spring connections between spatially proximal representatives in a variety of coarse-grained ENMs. Coarse-graining approaches enable one to simulate harmonic and anharmonic motions of large macromolecules in a PC, while all-atom based molecular dynamics (MD) simulation has been conventionally performed with an aid of supercomputer. A harmonic analysis of a macroscopic mechanical system, called normal mode analysis, has been adopted to analyze thermal fluctuations of a microscopic biological system around its equilibrium state. Furthermore, a structure-based system optimization, called elastic network interpolation, has been developed to predict nonlinear transition (or folding) pathways between two different functional states of a same macromolecule. The good agreement of simulation and experiment allows the employment of coarse-grained ENMs as a versatile tool for the study of macromolecular dynamics.
장서영(Seo Young Jang),정재일(Jay I. Jeong) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
In this paper, a mathematical model of roller-type bearings previously studied is reviewed in order to apply the correct bearing stiffness. The mathematical models based on Hertz contact theory that is suggested by Popov[1] was selected as stiffness models for simulation. To verify the formula model, a displacement/force graph was created through finite element analysis of a roller model with the same boundary conditions as the boundary line used in the formula. The result of the formula was compared with simulations. As a result of the analysis, the Popov equation model more closely matched the results of the finite element analysis. When the displacement was within 10 micrometers, the result was within the error range of 8.8%.
김도현(Dohyun Kim),김문영(Moonyoung Kim),정재일(Jay I. Jeong) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
In this paper, structural and thermal analysis are conducted to determine the effect of molten recycled plastic on moving between metal filters. Structure and thermal deformation of the metal filter should be analyzed since the fluid flow through a metal filter has a high-temperature, high-viscosity and high-pressure. Fluid solid interaction method (FSI) is used to reveal a coupling phenomenon between solids and fluids. The FSI analyzes the effect of fluid boundary conditions on metal filters. Pressure, flow rate, and temperature of the recycled plastic filter is used as the boundary condition of the FSI analysis. The largest deformation at the center of the filter, major stresses are observed at the inlet and outlet of each micro hole.