• 한국지능시스템학회논문지
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• 제26권3호
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• pp.196-201
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• 2016

본 논문에서는 인간의 팔꿈치 관절의 기능을 활성화하기 위한 강성 기반 재활 메커니즘의 특성을 분석하 고자 한다.여기서,팔굼치 관절의 재활을 위한 도구는 탄성 줄을 사용하고, 사용된 줄은 선형 스프링으로 모델링하여 강성값으로 나타낸다. 이러한 메커니즘을 이용한 팔꿈치 관절 재활 훈련을 효과적으로 하기 위해서는 줄의 강성값에 따라 팔꿈치 관절에 가용할 수 있는 토오크 특성을 분석할 필요가 있다. 이러한 관점에서 다양한 시뮬레이션을 통하여 탄성 줄의 강성값 설정에 따른 팔꿈치 관절의 토오크 패턴 및 범위를 사전에 정의된 팔꿈치 관절의 운동 경로에 대하여 확인한다. 결과적으로, 이러한 강성 기반 재활 메커니즘이 팔꿈치 관절의 효과적인 재활을 수행하는데 유용하게 활용될 수 있음을 보인다.

• 로봇학회논문지
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• 제3권1호
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• pp.9-15
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• 2008

Unlike robotic systems, humans excel at a variety of tasks by utilizing their intrinsic impedance, force sensation, and tactile contact clues. By examining human strategy in arm impedance control, we may be able to teach robotic manipulators human''s superior motor skills in contact tasks. This paper develops a novel method for estimating and predicting the human joint impedance using the electromyogram(EMG) signals and limb position measurements. The EMG signal is the summation of MUAPs (motor unit action potentials). Determination of the relationship between the EMG signals and joint stiffness is difficult, due to irregularities and uncertainties of the EMG signals. In this research, an artificial neural network(ANN) model was developed to model the relation between the EMG and joint stiffness. The proposed method estimates and predicts the multi joint stiffness without complex calculation and specialized apparatus. The feasibility of the developed model was confirmed by experiments and simulations.

• 한국공작기계학회논문집
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• 제13권1호
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• pp.94-99
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• 2004

The global stiffnesses and vibration characteristics of vehicle structures are mainly influenced by local stiffnesses of the joint structures consisted of complicated thin-walled panels. In this paper, the parametric study for the stiffnesses of the center pillar-roof rail joint of vehicle structure is performed through the linear static analysis. The analysis result shows that the reinforcement panel much affects the joint stiffness of out-plane direction (i.e., z-direction). And also, the flange radius and width of the joint structure much affect the Joint stiffness of out-plane direction. The study shows that vehicle joint stiffnesses can be effectively determined in designing vehicle structure through the parametric study.

• 소음진동
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• 제9권5호
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• pp.975-983
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• 1999

This paper describes the dynamic characteristics of the joint structures in case of using the simplified beam model in the F. E. analysis. The modeling errors, when replace the shell with the beam, are investigated through F. E. normal modes analysis. Normal mode analysis were performed to obtain the natural frequencies of the L and T shaped joints with various type of channels. The results were analyzed to access the effects of the models on the accuracy of F.E. analysis by identifying the geometric factors which cause the error. The geometric factors considered are joint angle, channel length, thickness and area ratio of the hollow section to the filled one. The joint stiffness evaluation technique is developed in this study using normal modes analysis with Lumped Mass. With this method, the progressively improved results of F. E. analysis are obtained using the simplified beam model. The static and normal modes analysis are performed with the joint stiffness values obtained by the Kazunori Shimonkakis' virtual stiffness method and the proposed method and these simplified modeling errors are compared.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.177-184
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• 2008

Vehicle body frame stiffness affects the dynamic and static characteristics. Vehicle frame structure performance is greatly affected by crossmember and joint design. While the structural characteristic of these joint vary widely, there is no known tool currently in use that quickly predicts joint stiffness early in design cycle. This paper present the joint design factors affecting on low frequency vibration. The joint factors are joint panel thickness, flange width and weld point space. To study the effect on vehicle low frequency vibration, case studies for these factors are performed. The result can present design guide for high-stiffness vehicle.

• 한국운동역학회지
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• 제23권4호
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• pp.357-367
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• 2013

The purposes of this study were investigated physical compensation for gait on induced knee stiffness in normal subjects. Ten subjects were participated in the experiment(age: $26.0{\pm}6.3$ yrs, height: $175.5{\pm}5.3$ cm, weight: $69.1{\pm}6.1$ kg). The study method adopted 3D analysis with five cameras and ground reaction force with two force-plate. Induced knee stiffness level were classified as gait pattern on ROM of knee(free level, $30^{\circ}$ restriction level, fix level). The results were as follows; In angular displacement of hip joint, left hip joint was the more extended in mid-stance on induced right knee stiffness. In angular displacement of knee joint, there was no physical compensation on induced right knee stiffness, but free knee level gait was more flexed in swing phase of right knee joint. In angular displacement of ankle joint, right ankle joint was the more dorsiflexed on induced right knee stiffness, and $30^{\circ}$ restriction level and fix level gait were less plantarflexed in TO2. In trunk tilt, free and $30^{\circ}$ restriction level gait was more backward tilt on induced right knee stiffness. In ROM of each joint, right knee joint was more larger and trunk tilt was more lower on induced right knee stiffness. In GRF, Fx was more bigger lateral force in free and $30^{\circ}$ restriction level gait, and was more bigger medial force in fix level gait. Fy was more bigger propulsion force in free level gait, and was was more bigger braking force in $30^{\circ}$ restriction level gait. Left braking force in $30^{\circ}$ restriction level gait was more bigger. Fz was no significant.

• 한국기계가공학회지
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• 제18권2호
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• pp.58-64
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• 2019

This paper describes the analysis of dynamic characteristics and prediction of the stiffness for the joint between structural members. In the process of deriving the governing equations, the stiffness values responsible for the moment and shear force were modelled by using linear and torsional springs in the middle of a clamped-clamped beam. The sensitivities of the natural frequency and modal assurance criterion were investigated as a function of the dimensionless linear and torsional spring stiffness. The reliability of the predictions for the linear and torsional stiffness values was verified by the inverse computations of the stiffness matrix. The predictive and exact theoretical stiffness values were compared for the stiffness element in the finite element formulation, and their results show an excellent correlation. It is strongly anticipated that although the proposed methodology is currently limited to the analytical utilization, it will provide a useful tool to estimate unknown joint stiffness values based on the experimental natural frequency and mode shape.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.202-209
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• 2007

Vehicle body frame stiffness affects the dynamic and static characteristics. Vehicle frame structural performance is greatly affected by crossmember and joint design. While the structural characteristics of these joints vary widely, there is no known tool currently in use that quickly predicts joint stiffness early in design cycle. This paper presents the joint design factors affecting on low frequency vibration. The joint factors are joint panel thickness, section property, flange width and weld point space. To study the effect on vehicle low frequency vibration, case studies for these factors are performed. And Sensitivity analysis for section property is performed. The result can present design guide for high-stiffness vehicle.

• Structural Engineering and Mechanics
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• 제45권4호
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• pp.423-437
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• 2013

Complex structures are usually assembled from several substructures with joints connecting them together. These joints have significant effects on the dynamic behavior of the assembled structure and must be accurately modeled. In structural analysis, these joints are often simplified by assuming ideal boundary conditions. However, the dynamic behavior predicted on the basis of the simplified model may have significant errors. This has prompted the researchers to include the effect of joint stiffness in the structural model and to estimate the stiffness parameters using inverse dynamics. In the present work, structural joints have been modeled as a pair of translational and rotational springs and frequency equation of the overall system has been developed using sub-structure synthesis. It is shown that using first few natural frequencies of the system, one can obtain a set of over-determined system of equations involving the unknown stiffness parameters. Method of multi-linear regression is then applied to obtain the best estimate of the unknown stiffness parameters. The estimation procedure has been developed for a two parameter joint stiffness matrix.

• Structural Engineering and Mechanics
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• 제83권3호
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• pp.341-351
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• 2022

During bolted flange assembly, the contact stiffness of some areas of the joint surface may be low due to the elastic interaction. In order to improve the contact stiffness at the lowest position of bolted flange, the correlation model between the initial bolt pre-tightening force and the contact stiffness of bolted flange is established in this paper. According to the stress distribution model of a single bolt, an assumption of uniform local contact stiffness of bolted flange is made. Moreover, the joint surface is divided into the compressive stress region and the elastic interaction region. Based on the fractal contact theory, the relationship model of contact stiffness and contact force of the joint surface is proposed. Considering the elastic interaction coefficient method, the correlation model of the initial bolt pre-tightening force and the contact stiffness of bolted flange is established. This model can be employed to reverse determine the tightening strategy of the bolt group according to working conditions. As a result, this provides a new idea for the digital design of tightening strategy of bolt group for contact stiffness of bolted flange. The tightening strategy of the bolted flange is optimized by using the correlation model of initial bolt pre-tightening force and the contact stiffness of bolted flange. After optimization, the average contact stiffness of the joint surface increased by 5%, and the minimum contact stiffness increased by 6%.