• 제어로봇시스템학회:학술대회논문집
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• 1996.10a
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• pp.20-23
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• 1996

This paper deals with the flexible manipulator with rotational and translational degrees of freedom, which has an arm of time-varying length with the prismatic joint. The tracking control problem of the flexible manipulator is considered. First we design the controller of the 2-type robust servo system based on the finite horizon optimal control theory for the trajectory planned as a discontinuous velocity. Next, to reduce the tracking error, we use the method of the dynamic programming and of modifying the reference trajectory in time coordinate. The simulation results show that the dynamic modeling is adequate and that the asymptotic stabilization of the flexible manipulator is preserved in spite of nonlinear terms. The PTP control error has been reduced to zero completely, and the trajectory tracking errors are reduced sufficiently by the proposed control method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.12
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• pp.2096-2105
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• 1997

A parallel approach using a network of engineering workstations is presented for the efficient computation in the elastoplastic analysis of strip rolling process. The domain decomposition method coupled with the frontal solver for elimination of internal degrees of freedom in each subdomain is used. PVM is used for message passing and synchronization between processors. A 2-D plane strain problem and the strip rolling process are analyzed to demonstrate the performance of the algorithm and factors that have a great effect on efficiency are discussed. In spite of much communication time on the network the result illustrates the advantages of this parallel algorithm over its corresponding sequential algorithm.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.10a
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• pp.444-451
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• 2003

In this study, a new three-dimensional finite element analysis model of high-speed railway bridges considering train-bridge interaction, in which various improved finite elements are used for modeling structural members, is proposed. The box-type bridge deck of a railway bridge is modeled by the NFS(Nonconforming Flat Shell) elements with 6 degrees of freedom. Track structures are idealized using the beam finite elements with the offset of beam nodes and those on Winkler foundation with two parameters. And, the vehicle model devised for a high-speed train is employed, which has an articulated bogie system. By Lagrange's equations of motion, the equations of motion of a bridge-train system can be formulated. Finally, by deriving the equations of the forces acting on a bridge considering bridge-train interaction the complete system matrices of total bridge-train system can be constructed. As numerical examples of this study, 2-span PC box-girder bridge is analyzed and results are compared with experimental results.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.1478-1485
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• 2010

In this paper, the nonlinear dynamic response of Vehicle-Bridge interaction with the coupled equations of motion including nonlinear Hertzian contact is presented. The moving train model is chosen to have 10 degrees of freedom (DOF). The bridge is modeled as 2D Euler-Bernoulli beam element with 4 DOF for each element, two for rotations and another two for translations. The nonlinear Hertzian contact is used to simulate the interaction between vehicle and bridge. Base on the relationship of wheel displacement of the vehicle and the vertical displacement of the bridge in Hertzian contact, the coupled equations of motion of the whole system is derived. The convenient formulation was encoded into a computer program. The contact forces, contact area and stress of the rail surface were also computed. The accuracy and efficiency of the proposed program are verified and compared with exact analytical solution and other previous studies. Various numerical examples and parametric studies have demonstrated the versatility and applicability of the proposed program.

• Journal of the Ergonomics Society of Korea
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• v.15 no.2
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• pp.125-135
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• 1996

The purpose of this research is to measure range of virtual hip joint and lower limb joints motion such as the hip, knee and ankle joints for 47 young male students. The results of ANOVA revealed that anthropometric dimensions including weight and stature did not show any significant effects on the range of virtual hip joint and lower limb joints motion and the range of motion with two degrees of freedom at the shoulder, virtual hip and hip joints. Anthropometric dimensions such as age, weight, statuire, arm length, shoulder height and leg length were found to be lowly correlated with the range of virtual hip joint and lower limb joints motion. It is expected that the data on the range of joint motion suggested in this study can be used as a valuable input data when designing workplace, predicting human posture and reach volume, etc.

• Korean Journal of Computational Design and Engineering
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• v.3 no.2
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• pp.87-102
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• 1998

Given a sequence of cross-sectional curves, the skinning method generates a freeform surface that interpolates the given curves in that sequence. This thesis presents a construction method of a B-spline skinning surface that is fair and satisfies volume constraints. The fairness metric is based on the parametric energy functional of a surface. The degrees of freedom in surface control are closely related lo control points in the skinning direction. The algorithm fur finding a skinning surface consists of two step. In the first step, an initial fair surface is generated without volume constraints and one coordinate of each control point is fixed. In the second step, a final surface that meets all constraints is constucted by rearranging the other coordinates of each control point that defines the initial surface A variational Lagrange optimization method produces a system of nonlinear equations, which can be solved numerically. Moreover, the reparametrization of given sectional curves is important for the construction of a reasonable skinning surface. This thesis also presents an intuitive metric for reparametrization and gives some examples that are optimized with respect to that metric.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.2
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• pp.138-150
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• 2000

This study is concerned with computerized multi-level substructuring methods and stress analysis of coil springs. The purpose of substructuring methods is to reduce computing time and capacity of computer memory by multiple level reduction of the degrees of freedom in large size problems which are modeled by three dimensional continuum finite elements. In this paper, a super element has been developed for stress analysis of coil springs. The spring super element developed has been examined with tension and torsion simulation of cylindrical bars for demonstrating its validity. The result shows that the super element enhances the computing efficiency while it does not affect the accuracy of the results and it is ready for application to the coil spring analysis.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1495-1499
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• 2003

There is some equipment that helps user to exercise and to walk. But almost all equipments require some physical strength of their muscles. So we developed a system that could assist walking action of the people with lower-limb disability. The system called as walking stand adopted the balancing mechanism which assures the stable walking, and the 4 link-based mechanism that had 2 degrees of freedom on each leg. The walking stand uses four motors and has two sets of the special link-structure to simulate the human walking mechanism. With our system, even serious disabled with lower-limb disability may enjoy walking rehabilitation. And by adjusting the power, it can be used as the walking assistant mechanism instead of conventional wheelchairs. Experiments showed that our walking stand is applicable to the rehabilitation and also to the mobile device in our daily life for those people who do not have enough physical ability to walk by themselves.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.134.2-134
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• 2001

This paper treats the implementation of a statically stable control system for a biped walking robot with 10 degrees-of-freedom. Statically stable walking of a biped robot can be realized by keeping the center of mass (COM) inside the sole of the supporting foot (or feet) during single-support or double-support phases. We predetermined five static positions for walking based on the COM method. The positions can be represented by the length of the gait, the width between the feet, the height of the foot and two parameters in the hip movement. With the five parameters, we calculated the position trajectory. And we got the angular trajectories of 10 joints from the posit ion trajectory using the position tracking control and neural network. By tracking the angular trajectories, the robot can walk maintaining stability. We implemented walking of a biped robot throught the above ...

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1503-1507
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• 2003

A general vibration phenomenon of a rigid-body supported by springs can be viewed as a small repetitive screw displacement. From this view, a multi-directional vibration absorber can be designed by use of screw theory and transfer matrix method. In this paper, the basic equations of motion for a multi-body system have been expressed in terms of screws using transfer matrix method and a simple approach to the design of a multi-degrees-of-freedom absorber has been presented. In order to illustrate the methodology, an example for the design of a 2-DOF active absorber which is capable of absorbing vibration of a rigid body excited by 3-DOF external force has been presented.