• Transactions of Materials Processing
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• v.14 no.4 s.76
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• pp.327-337
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• 2005

In the present work, the two back stress kinematic hardening models are proposed by combining Armstrong-Frederick, Phillips and Ziegler's hardening rules. Simple combination of hardening rules using simple rule of mixtures results in various evolutions of the kinematic hardening parameter. Using the combined hardening models the ultimate back stress fur the present models is also derived. The stress rate is co-rotated with respect to the spin of substructure due to the assumption of kinematic hardening rule in finite deformation regime. The work piece under consideration is assumed to consist of the elastic and the rigid plastic deformation zone. Then, the J2 deformation theory is facilitated to characterize the plastic deformation behavior under various loading conditions. The plastic deformation localization behaviors strongly depend on the constitutive description namely back stress evolution and its hardening parameters. Then, the analysis for Swift's effects under the fixed boundaries in axial directions is carried out using simple shear deformation.

• Transactions on Control, Automation and Systems Engineering
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• v.3 no.4
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• pp.210-216
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• 2001

In this paper, design of a 3-degree-of-freedom mobile robot with three caster wheels is performed. Initially, kinematic modeling and singularity analysis of the mobile robot is performed. It is found that the singularity can be avoided when the robot has more than two wheels on which two active joints are located. Optimal kinematic parameters of mobile robots with three active joint variables and with four active joint variables are obtained and compared with respect to kinematic isotropic index of the Jacobian matrix of the mobile robot which is functions of the wheel radius and the length of steering link.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.11
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• pp.2665-2671
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• 2000

Dimensional Synthesis, which is apart of kinematic synthesis, is to determine the dimensions of a mechanism of preconceived typer for a specified task and prescribed performance. In this paper, in an effort to provide designers with flexibility, a dimensional approximate synthesis method is presented for utilizing prescribed tolerance both the displacement and joint positions of a mechanism to be synthesized. For this, a constrained optimization problem is formulated with displacement parameters and joint positions as variables. The proposed method is applied to the synthesis of a 5-SS multi link suspension mechanism. The method discussed here, however, can be easily applied to any mechanism of which the kinematic constraint equations can be derived.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.10
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• pp.1035-1043
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• 2006

In this study, a translational 3-DOF parallel mechanism formed by constraining the Stewart Platform Mechanism is investigated. The translational 3-DOF parallel mechanism has three struts(3-UPS type serial subchains) and in addition, has a PPP type serial subchain in the middle of the mechanism. Firstly, the closed-form forward and reverse position solutions are derived for this mechanism. And analysis on kinematic characteristics using isotropic index of the Jacobian is conducted to examine effects of design parameters for the mechanism. Lastly, a prototype mechanism is implemented and the kinematic performance of the translational 3-DOF parallel mechanism was verified through experimental work.

• Transactions of Materials Processing
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• v.17 no.1
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• pp.19-26
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• 2008

In the present work, the ratcheting behavior under uniaxial cyclic loading is analyzed. A comparison between the published and the results from the present model is also included. In order to simulate the ratcheting behavior, Two-Back Stress model is proposed by combining the non-linear Armstrong-Frederick rule and the non-linear Phillips hardening rule based on kinematic hardening equation. It is shown that some ratcheting behaviors can be obtained by adjusting the control material parameters and various evolutions of the kinematic hardening parameter can be obtained by means of simple combination of hardening rules using simple rule of mixtures. The ultimate back stress is also derived for the present combined kinematic hardening models.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.11 s.242
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• pp.1509-1517
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• 2005

This paper presents the two degree-of-freedom(DOF) planar parallel mechanism called 2R$\underline{P}$R-RP manipulator, whose degree-of freedom is dependent on a passive constraining leg connecting the base and the platform. First, the kinematic analysis of the mechanism is performed analytically: the inverse and forward kinematic problems are solved in the closed font the practical workspace is systematically derived, and all of the singular configurations are examined. Then, in order to determine the geometric parameters and the operating limits of the actuators, the optimization of the mechanism is performed considering its dexterity and stiffness. Finally, the kinematic performances of the optimized mechanism are evaluated through comparing to the 5-bar parallel manipulator.

• Journal of Institute of Control, Robotics and Systems
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• v.7 no.2
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• pp.168-172
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• 2001

The accuracy problem of robot manipulators has long been one of the principal concerns in robot design and control. A practical and economical way of enhancing the manipulator accuracy, without affecting its hardware, is kinematic calibration. In this paper an effective and practical method is presented for kinematic calibration of Stewart platforms. In our method differential errors in kinematical parameters are linearly related to differential errors in the platform pose, expressed through the forward kinematics. The algorithm is tested using simulated measurement in which measurement noise is included.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.5
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• pp.464-472
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• 2006

This paper presents the two degree-of-freedom (DOF) planar parallel mechanism, called the $2{\underline{R}}RR-RP$ manipulator, whose degree-of-freedom is dependent on an additional passive constraining leg connecting the base and the platform. First, the kinematic analysis of the mechanism is performed: the inverse and forward kinematic problems are analytically solved, the workspace is systematically derived, and all of the singular configurations are examined. Then, in order to determine the geometric parameters the optimization of the mechanism is performed considering its dexterity, stiffness, and space utilization. Finally, the kinematic performances of the optimized mechanism are evaluated through the comparison study to the conventional 5-bar parallel manipulator.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1512-1517
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• 2003

This paper presents the calibration for the parallel typed tilting table. The calibration system needs only simple sensing device which is a digital indicator to measure the orientation of a table. The calibration algorithm is developed by a measurement operator. It eliminates the concern about the poor parameter observability due to a large number of parameters of parallel-mechanism. This paper uses the QR-decomposition to find the optimal calibration configurations maximizing the linear independence of rows of a observation matrix. The number of identifiable parameters is examined by the rank of the observation matrix, which represents the parameter observability. The method is applied to a Parallel-typed Tilting Table and all the necessary kinematic parameters are identifiable.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.666-672
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• 2017

Our research team is developing a 6-DOF manipulator for narrow workspaces in press forming processes, such as placing PEM nuts on the bottom of a chassis. In this paper, kinematic analysis was performed for the position control of the manipulator, along with structural analyses for position accuracy with different payloads. First, the Denavit-Hatenberg (DH) parameters are defined, and then the forward and backward kinematic equations are presented using the DH parameters. The kinematic model was verified by visual simulation using Coppelia Robotics' virtual robot experimentation platform (V-REP). Position accuracy analysis was performed through structural analyses of deflection due to self-weight and deflection under full payload (5 kgf) in fully opened and fully folded states. The maximum generated stress was 22.05 MPa in the link connecting axes 2 and 3, which was confirmed to be structurally safe when considering the materials of the parts.