• Journal of the Korean Society of Physical Medicine
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• v.7 no.2
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• pp.205-212
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• 2012

Purpose : The aim of this study was to investigate the relationship between weight-supporting asymmetry and gait symmetry in patients with stroke. Methods : Sixty two stroke patients with hemiplegia stood quietly with eye opens on a force platform to calculate weight-supporting asymmetry from vertical reaction force. The GAITRite was used to evaluate their gait parameters. The data were analyzed using Pearson correlation. Results : The results of this study was showed that the medio-lateral index (ML) was correlated with symmetry rate (SR), symmetry index (SI), and Gait asymmetry (GA) of step time and length but stronger correlation with spatial gait symmetry than temporal symmetry. In gait symmetry, step length has stronger correlation with weight-supporting asymmetry than step time. Conclusions : The results of this study shows weight-supporting asymmetry was correlated with more spatial gait symmetry than temporal symmetry.

• Journal of Electrical Engineering and Technology
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• v.11 no.3
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• pp.733-740
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• 2016

To achieve bipedal walking in real human environments, a bipedal robot should be capable of modifiable walking both on uneven terrain with different heights and on flat terrain. In this paper, a novel walking pattern generator based on a 3-D linear inverted pendulum model (LIPM) is proposed to achieve this objective. By adopting a zero moment point (ZMP) variation scheme in real time, it is possible to change the center-of-mass (COM) position and the velocity of the 3-D LIPM throughout the single support phase. Consequently, the proposed method offers the ability to generate a modifiable pattern for walking on uneven terrain without the necessity for any extra footsteps to adjust the COM motion. In addition, a control strategy for bipedal walking on uneven terrain with unknown height is developed. The torques and ground reaction force are measured through force-sensing resisters (FSRs) on each foot and the foot of the robot is modeled as three virtual spring-damper models for the disturbance compensation. The methods for generating the foot and vertical COM of 3-D LIPM trajectories are proposed to achieve modifiable bipedal walking on uneven terrain without any information regarding the height of the terrain. The effectiveness of the proposed method is confirmed through dynamic simulations.

• Proceedings of the ESK Conference
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• 1993.04a
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• pp.1-9
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• 1993

A human gait study is required for the biomechanical design of running shoes. A tow-dimensional dynamic model was developed in order to analyze lower extremity kinematics and loadings at the right ankle, knee, and hip joints. The dynamic model consists of three segments, the upper leg, the lower leg, and the foot. Each segment was assumed to be a rigid body with one or two frictionless hinge joints. The lower extremity motion was assumed to be planar in the sagittal plane. A young male subject was involved in the gait test and his anthropometric data were measured for the calculation of segement mass and moment of inertia. The experimental data were obtained from three trials of walking at 1.2m/s. The foot-floor reaction data were measured from a Kistler force plate. The kinematic data were acquired using a three-dimensional motion measurement system (Expert Vision) with six markers, five of which were placed on the right lower extremity segments and the rest one was attached to the force plate. Based on the model and experimental data for the stance phase of the right foot, the calculated vertical forces reached up to 492, 540, and 561 N at the hip, knee, ankle joints, respectively. The flexion-extension moments reached up to 155, 119, and 33 Nm in magnitude at the corresponding joints.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1992.04a
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• pp.7-12
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• 1992

The variable node plate bending element, ie, the element with one or two additional mid-side nodes is used in the analysis of mat foundation to generate the nearly ideal grid model in which more nodes are defined near the column location. The plate bending element used in this study is the one based on Mindlin/Reissner plate theory with substitute shear strain field and the nodal stresses of that element are obtained by the local smoothing technique. The interaction of the soil material with the mat foundation is modeled with Winkler springs connected to the nodal points in the mat model. The vertical stiffness of the soil material are represented in terms of a modulus of subgrade reaction and are computed in the same way as to the computation of consistent nodal force of uniform surface loading. Several mesh schemes were proposed and tested to find the most suitable scheme for mat foundation analysis.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.1
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• pp.15-21
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• 2013

The safety and stability of 5MW class offshore wind turbine Jack-up platform was investigated through ocean basin experiment. For simulating the environmental condition of yellow sea in the South Korea, diverse waves, winds and currents were performed based on Froude's number. Regular wave and irregular wave based on Froude's number were applied to the wind turbine structure. In experiments, the height and period of regular wave type were scaled down as the 1:50 ratio of real wave condition. Irregular wave type was simulated with TMA(Texel Storm, Marsen and Arsloe)spectrum. The vertical reaction force, resonance period and wave pressure applied to multi-supporters of wind offshore structure were measured experimentally. Finally, the results showed that the capsizing situation of the offshore structure was generated by the severe environmental condition.

• Korean Journal of Applied Biomechanics
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• v.25 no.1
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• pp.85-94
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• 2015

Purpose : The purpose of this study was to investigate the influence on the ground reaction force parameters according to wearing positions of backpack for during stair ascending and descending. Methods : Participants selected as subject were consisted of young female(n=10) and performed stairs walks(ascending and descending) with 2 types of wearing position(front of trunk[FT], rear of trunk[RT]). Passive(Fz 1) and active(Fz 2) forces of the vertical GRF were determined from time function and frequency domain. Also shear forces(Fx, Fy 1, Fy 2), dynamic postural stability index(MLSI, APSI, VSI, DPSI), loading rate and center of pressure (${\Delta}COPx$, ${\Delta}COPy$, COP area) were calculated from time function and frequency domain. Results : Fx, Fy 1, Fy 2, and Fz 1 in GRF didn't show significant differences statistically according to the wearing positions of backpack(p>.05), but stair descending showed higher forces than that of stair ascending. Particularly, Fz 2 of stair ascending showed higher forces than that of stair descending(p<.001), RT types showed higher than that of FT types(p<.05). MLSI, APSI, VSI, and DPSI of stair descending showed the increased stability index than that of stair ascending(p<.05), MLSI of RT types showed the decreased stability index than that of FT types(p<.05). Loading rate didn't show significant differences statistically according to the wearing positions of backpack(p>.05), but stair descending showed higher loading rate than that of stair ascending(p<.001). Also, ${\Delta}COPx$ in stair descending showed the increased movement than that of stair ascending(p<.05). Conclusions : A backpack of 10 kg(10 kg(ratio of body weights $17.61{\pm}1.17%$) showed significantly change GRF parameters according to wearing positions during stair ascending and descending. If possible, we suggest that the dynamic stability, in case of stairs walking with a smaller weights can be further improved.

• Korean Journal of Applied Biomechanics
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• v.18 no.1
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• pp.169-178
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• 2008

The goals of this study were to provide data of 3 dimensional ground reaction force(GRF) parameters during stair ascent and descent on three different stair runs and to investigate variability and asymmetry index of them. 10 healthy adults participated in this study and performed 7 different types of gait with 10 trials each. After data analysis, following results were found. Firstly, stair run did not affect on the pattern of GRF parameters, coefficient of variation and asymmetry index. Secondly, a significant different GRF pattern was found between level walking and stair walking. Especially, ascending stair walking has only large Fz1 and small Fz3 while level walking and descending stair walking have a "M" shape connected by Fz1, Fz2 and Fz3. Thirdly, only vertical GRF parameters of stair walking revealed acceptable coefficient of variation and asymmetry index.

• Journal of Biomedical Engineering Research
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• v.32 no.1
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• pp.61-73
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• 2011

The purpose of this study was to investigate changes in the center of pressure (COP), ground reaction force (GRF) and joint angles of elderly people and young people while stair-descent. The participants in this experiment were 5 elderly people and 5 young people, each of which was asked to descend stairs of three different heights (8 cm, 16 cm, and 32 cm). As they climbed down the stairs, they received vibration stimulation on the lower limb. The change of COP, GRF and joint angles were analyzed during the standing phase. COP decreased as the Achilles tendon and tibialis anterior tendon were vibrated. Vertical GRF increased as the Achilles tendon was vibrated, and the joint angle differed according to vibration stimulation conditions. These results mean that ankle joint, knee joint and hip joint were influenced by the vibrations on the lower limb as the participants descended the stairs. It was concluded that the vibration stimulation on the lower limb allowed the participants to efficiently climb down the stairs.

• Korean Journal of Applied Biomechanics
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• v.25 no.3
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• pp.241-248
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• 2015

Objective : The purpose of this study was to investigate the theta on the components of ground reaction force according to the ground conditions during gait. Method : Six healthy women(mean age: 22 yrs, mean height: $166.14{\pm}2.51cm$, mean body weights: $56.61{\pm}4.58kg$) participated in this study. The medial-lateral GRF(Fx 1), anterior-posterior GRF(Fy 1, Fy 2), vertical GRF(Fz 1, Fz 2, Fz 3), and impact loading rate were determined from time function and frequency domain. Also, GRF theta were time function and forces. Results : Fx 1, Fy 1 and Fy 2 of stair descending showed significant statistically higher forces than that of level walking, and ascending. Fz 1 of stairs descending showed significant statistically higher forces than that of level walking and stairs ascending(theta $88.62^{\circ}$). Also, Fz 2 of level walking showed significant statistically higher forces than that of stairs ascending and descending(theta $65.78^{\circ}$). Fz 3 of stairs ascending showed significant statistically higher forces than that of level walking and stairs descending($65.26^{\circ}$). Impact loading rate of stairs descending showed significant statistically higher forces than that of level and ascending walking. The GRF showed similar correlation with GRF theta(r=.603) according to the ground conditions during gait. Conclusion : These results suggest that the GRF theta can be used in conjunction with a gait characteristics, prediction of loading rate and dynamic stability.

• Journal of Digital Convergence
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• v.12 no.11
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• pp.451-459
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• 2014

This study was to performed to get the reference data of the kinetic parameters for normal subjects according to the arm swing type. Forty-five normal subjects($22.62{\pm}2.69years$) pariticpated in this study and preformed 4 sequence according to the arm swing type as follows; first procedure-normal arm swing, second procedure-one arm swing, thrid procedure-no arm swing, fourth procedure-fitness arm swing. There were significant differences according to the arm swing type in the kinetic parameters such as walking speed, hip power, ground reaction force of vertical in terminal stance phase(p<.05). These finding can be utilized (a) as a reference for kinetic data of gait analysis in normal subjects, and (b) as an aide in evaluating and treating patients who have problems relating to gait.