• International Journal of Precision Engineering and Manufacturing
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• v.7 no.2
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• pp.25-29
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• 2006

Analysis of structures which are composed of numerous repeated unit structures can be simplified by using homogenized properties. If the unit structure is repeated in one direction, the whole structure may be regarded as a beam. Once the effective stiffness is obtained from the analysis of the unit structure in a proper way, the effort for the detail modeling of the global structure is not required, and the real structure can be replaced simply with a beam. This study proposes a kinematical periodicity constraint to be imposed on the FE model of the unit structure, which improves the accuracy of the effective stiffness. The method is employed to a one dimensionally arrayed 3D structure containing periodically repeated unsymmetrical holes. It is demonstrated that the deformation behavior of the homogenized beam agrees well with that of the real structure.

• Journal of Mechanical Science and Technology
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• v.19 no.spc1
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• pp.320-327
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• 2005

A new mechanism for hyper redundant manipulator (HRM) is presented, which comprises of serially assembled compound three-bar linkages (CTL). The CTL mechanism has some unique properties. This paper presents the forward and inverse kinematics of this mechanism and shows the simulation of the HRM havig 9 CTL units. The recursive algorithm of the inverse kinematics that the author originally developed is employed. It is fast and stable ; moreover, it enables us to obtain a solution in which the end-point of the HRM is controlled by a portion of joints. It also presents the method of the dynamical analysis. There exist kinematical constraints in the proposed closed linkage mechanism. In the dynamic analysis constraints are sufficiently sustained by the constraint stabilization method that the author developed. The mechanical structure of the HRM having some CTL units that is under construction is shown.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.7 s.172
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• pp.170-176
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• 2005

Analysis of structures which are composed of numerous repeated unit structures can be simplified by using homogenized properties. If the unit structure is repeated in one direction, the whole structure may be regarded as a beam. Once the effective stiffness is obtained from the analysis of the unit structure in a proper way, the effort for the detail modeling of the global structure is not required, and the real structure can be replaced simply with a beam. This study proposes a kinematical periodicity constraint to be imposed on the FE model of the unit structure, which improves the accuracy of the effective stiffness. The method is employed to a one dimensionally arrayed 3D structure containing periodically repeated un-symmetric holes. It is demonstrated that the deformation behavior of the homogenized beam agrees well with that of the real structure.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.10a
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• pp.189-196
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• 1996

Vibration of a beam translating over supports in vertical motion is investigated in this paper. Equations of motion are formulated using the virtual work principle by regarding the supports as kinematical constraints imposed on an unrestrained beam and by discretizing the beam via the assumed mode method. Differential-algebraic equations of motion are derived and reduced to differential equations in independent generalized coordinates by the generalized coordinate partitioning method. Geometric stiffness of the beam due to translating motion is considered and how the geometric stiffness of beam affects dynamic stability is also investigated. Instability of the beam. in various conditions is also investigated using Floquet theory and then the results are verified through the dynamic response analysis. Results of numerical simulation are presented for various prescribed motions of the beam.

• Korean Journal of Applied Biomechanics
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• v.14 no.3
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• pp.203-218
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• 2004

The purpose of this study was to analyze the comparisons of the kinematical variables when performing Yoko Ukemi(side breakfall) by three Stage in Judo. The subjects were four male judokas who were trainees Y. I. University Squad members and the Yoko Ukemi were filmed by two S-VHS 16mm video cameras(60fields/sec.). The selected times were subject to KWON 3D analysis program and kinematical analysis to compare variables of three Yoko Ukemi. Temporal variables(total time-required : TK, TR by each phase), the body part touched order on the mat and COG variables were computed through video analysis while performing right Yoko Ukemi by three stage. From the data analysis and discussion, the following conclusions were drawn : 1. Temporal variables : total time-required(TR) when performing Yoko Ukemi(side breakfall) by each stage, the first stage(full squat posture: FP : 1.11sec.) showed the shortest time, the next was 3rd(Shizenhontai, straight natural posture: NP : 1.41sec.), and 2nd(Jigohontai, straight defensive posture, DP : 1.42sec.), respectively- 2. TR when performing Yoko Ukemi(side breakfall) by each stage, and phase : the first phase(take of phase, average 0.68sec.) showed the longest time, next was the third phase(ukemi phase, 0.39sec.), and the second phase(air phase, 0.23sec.), respectively. 3. When performing yore Ukemi the body part touched order and TR on the mat : hip(0.94sec.) showed the shortest time, the next was elbow hand(0.97sec.), back(0.98sec.), and shoulder(1.04sec.) order. The hip part touched on the mat the first, but slap the mat in order to alleviate the shock try hand palm and forearm before receiving impact (difference 0.03sec,) 4. Vertical COG variables in each event by each stage : e1(ready position, average 78.33cm) moved the highest, the next was e2(jumping position, 70.14cm), e3(transition position, average 64.00cm), e4(landing position, average 35.99cm), and e5(ukemi position, average 18.32cm) order, gradual decrease respectively. And the difference of COG were showed in initial by each stage, because position fo Yoko Ukemi was difference by each stage in preparation position, but in accordance with executing of Ukemi phase that difference of COG was by decreasing, almost equal displacement in e4(landing) and e5(Ukemi)position finally.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.7 s.196
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• pp.133-138
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• 2007

It is important to understand the characteristics of amputee gait to develop more advanced prostheses. The aim of this study was quantitatively to analyze the stair climbing task for the above-knee amputee with a prosthesis and to predict muscle forces and joint moments at musculoskeletal joints by dynamic analysis. The three-dimensional musculoskeletal model of lower extremities was constructed by gait analysis and transformation software for one above-knee amputee and ten healthy people. The measured ground reaction forces and kinematical data of each joint by gait analysis were used as input data during inverse dynamic analysis. Lastly, dynamic analysis of above-knee amputee during stair climbing were performed using musculoskeletal models. The results showed that summed muscle farces of hip extensor of amputated leg were greater than those of sound leg but the opposite results were revealed at hip abductor and knee flexor of amputated leg. We could also find that the higher moments at hip and knee joint of sound leg were needed to overcome the flexion moment caused by body weight and amputated leg. In conclusion, dynamic analysis using musculoskeletal models may be a useful mean to predict muscle forces and joint moments for specific motion tasks related to rehacilitation therapy..

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.1
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• pp.30-33
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• 2008

Understanding the characteristics of amputee gait is key in developing more advanced prostheses. The aim of this study was to quantitatively analyze a stair-climbing task for transfemoral amputees with a prosthesis and to predict the muscle forces and joint moments at musculoskeletal joints using a dynamic analysis. A three-dimensional musculoskeletal model of the lower extremities was constructed from a gait analysis using transformation software for two transfemoral amputees and ten healthy people. The measured ground reaction forces and kinematical data of each joint from the gait analysis were used as input data for an inverse dynamic analysis. Dynamic analyses of an transfemoral amputee climbing stairs were performed using musculoskeletal models. The results showed that the summed muscle forces of the hip extensor of an amputated leg were greater than those of a sound leg. The opposite was true at the hip abductor and knee flexor of an amputated leg. We also found that higher moments at the hip and knee joints of the sound leg were required to overcome the flexion moment caused by the body weight and amputated leg. Dynamic analyses using musculoskeletal models may be a useful means to predict muscle forces and joint moments for specific motion tasks related to rehabilitation therapy.

• Proceedings of the Korean Geotechical Society Conference
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• 1993.10a
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• pp.63-68
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• 1993

Soil nailing is a method of reinforcing natural deposits of soil with passive inclusions, called nails, of steel or other materials. Its purpose is mainly to increase the tensile and shear strength of the soil mass. This method has been widely used during the last two decades to stabilize steep slopes in several countries (France, Germany, USA, Japan, etc.). The design methods that have been mostly used are Davis method, German method, and French method which are based on limit equilibrium approaches, and Juran method which utilizes the kinematical limit equilibrium design concept. This paper is focussed on the evaluation of the available design methods(especially, the France, Davis and German design methods) through comparison with each different assumption for the failure surface, the concept of failure mechanism and the definition of safety factor. The parametric study to identify the effects of design parameters on the overall factor of safety has also been conducted. By considering the results along with the associated assumptions which have been postulated in the several methods, the applicability of the method for a given soil and nail conditions has been evaluated.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.12 s.177
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• pp.190-197
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• 2005

For precise micro-grooving and surface machining, a mechanism for creating elliptical vibration cutting (EVC) motion is proposed which uses two parallel piezoelectric actuators. And based on its kinematical analysis, variations of EVC path are investigated as a function of dimensional changes in the mechanism, phase difference and amplitude of excitation sinusoidal voltages. Using the proposed PZT mechanism, various types of two dimensional EVC paths including one dimensional vibration cutting path along the cutting direction and thrust direction can be easily obtained by changing the phase lag, the amplitude of the piezoelectric actuators, and the dimension of the mechanism.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.6
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• pp.486-494
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• 2004

This paper addresses the dynamic modeling and closed-loop eigenvibration analysis of composite rotating pretwisted fan blade modeled as non-uniform thin-walled beam with bi-convex cross-section fixed at the certain presetting angle and incorporating piezoelectric induced damping capabilities. The blade model incorporates non-classical features such as transverse shear, rotary inertia and includes the centrifugal and Coriolis force field. A velocity feedback control law relating the piezoelectiriccally induced transversal bending moment at the beam tip with the appropriately selected kinematical response quantity is used and the beneficial effects upon the closed loop eigenvibration of the blade are highlighted.