• Journal of the Korean Society for Precision Engineering
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• v.26 no.2
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• pp.126-132
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• 2009

This study examined the differences in spatio-temporal parameters, joint angle, ground reaction force (GRF), and joint power according to the changes of gait speed for trans-tibial amputees to investigate the features of the energy-storing foot for sports. The subjects walked at normal speed and at fast speed, wearing a single-axis type foot (Korec) and an energy-storing foot for sports (Renegade) respectively. The results showed that Renegade yielded faster gait speed as well as more symmetric gait pattern, compared to Korec. However, as gait speed was increased, there was no significant difference in kinematics, ground reaction force, and joint power between two artificial foots. This was similar to the results from previous studies regarding the energy-storing foot, where the walking velocity and gait symmetry have been improved. Nevertheless, the result of this study differed from the previous ones which reported that joint angle, joint power, and GRF increased as the gait speed increased except spatio-temporal parameters.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.7
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• pp.779-784
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• 2014

This study provided the analytical model describing the friction-induced noise in the ball joint system under the edge loading condition. The frictional and conformal contact kinematics between the spherical bearing and the hemispherical socket was derived and the dynamic equations of the perturbed motion were established. The numerical results revealed that the bending modes of the ball joint system can become unstable due to friction, and the axial load and contact stiffness strongly influenced the dynamic instability. In contrast, the tilting angle of the socket was not found to significantly contribute to the dynamic instability of the ball joint.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.2
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• pp.183-190
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• 2008

This paper deals with the characteristics of idle vibration due to the type of constant velocity joints. Based on the kinematics model of constant velocity joints, a offset between the tripod center and tullip center plays a important role in generating unwelcome forces. Moreover, it induced additional forces in lateral direction of a vehicle movement according to the angle of the spider in idle vibration. The difference of mass for each constant velocity joint types affect the natural frequency of the driveshaft and the powertrain. When the static torque is applied to the constant velocity joints, the natural frequencies of the driveshaft are reduced nearby 50Hz. There will be a big opportunity that the dirveshaft and constant velocity joints would be a transfer path of idle vibration at D or R gear range. Experiments indicate that TJ type is better than SFJ and DOJ in idle vibration.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1995.04a
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• pp.629-634
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• 1995

The purpose of this paper is to develop a method of Collision-Free Path Planning (CFPP) for an articulated robot. First, the configuration of the robot is formed by a set of robot joint angles derived fromm robot inverse kinematics. The joint space that is made of the joint angle set, forms a Configuration space (Cspace). Obstacles in the robot workcell are also transformed and mapped into the Cspace, which makes Cobstacles in the Cspace. (The Cobstacles represented in the Cspace is actually the configurations of the robot causing collision.) Secondly, a connected graph, a kind of roadmap, is constructed from the free configurations in the 3 dimensional Cspace, where the configurations are randomly sampled form the free Cspace. Thirdly, robot paths are optimally in order to minimize of the sum of joint angle movements. A path searching algorithm based on A is employed in determining the paths. Finally, the whole procedures for the CFPP method are illustrated with a 3 axis articulated robot. The main characteristics of the method are; 1) it deals with CFPP for an articulated robot in a 3-dimensional workcell, 2) it guarantees finding a collision free path, if such a path exists, 3) it provides distance optimization in terms of joint angle movements. The whole procedures are implemented by C on an IBM compatible 486 PC. GL (Graphic Library) on an IRIS CAD workstation is utilized to produce fine graphic outputs.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.882-887
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• 2003

This paper presented a design and control of a new RGO(reciprocating gait orthosis)and its simulation. The new RGO was distinguished from the other one by which had a very light-weight and a new RGO(reciprocating gait orthosis) system. The vibration evaluation of the hip joint system on the new RGO(reciprocating gait orthosis)was used to access by the 3-axis accelerometer with a low frequency vibration of less than 30 ㎐. The gait of the new RGO depended on the constrains of mechanical kinematics and the initial posture. The stability of dynamic walking was investigated by analyzing the ZMP (zero moment point) of the new RGO. It was designed according to the human wear type and was able to accomodate itself to the environments of S.C.I. Patients. The joints of each leg were adopted with a good kinematic characteristics. To analyse joint kinematic properties, we made the hip joint system of FEM and the hip joint system by 1-axis and 3-axis Accelerometers.

• The Journal of Korean Physical Therapy
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• v.28 no.1
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• pp.14-21
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• 2016

Purpose: The purpose of this study was to investigate examine how the kinematics and kinetics of lower limb joints were changed depending on the unstable shoes (US) during sit-to-stand task (SitTS). Methods: Nineteen healthy females were participated in this study. The subjects performed sit-to-stand task with US and barefoot. The experiment was repeated three times for each tasks with conditions. The kinematics and kinetics of lower limb joint were measured and analyzed using a 3-D motion analysis system. A paired t-test was utilised performed for to identificationy of changes in mean of angle, force, and moment between both the two conditions. Results: The results of this study showed kinematic differences in lower limb joints during SitTS based on the US. The hip, knee, and ankle angle showed statistically significant differences during SitTS. At the initial of SitTS, Tthe force and moment of the hip flexor, hip extensor, knee flexor, knee extensor, ankle flexor, and ankle extensor showed statistically significant differences. At the terminal of SitTS, Tthe force and moment of the hip flexor, hip extensor, knee flexor, knee extensor, ankle flexor, and ankle extensor showed statistically significant differences. At the maximum of SitTS, Tthe moment of the hip extensor showed statistically significant differences. The force and moment of the ankle flexor, extensor moment showed statistically significant differences. Conclusion: Therefore, Wwearing US is considered to influence on the lower limb joints kinematics and kinetics during SitTS movements, and thus suggests the possibility that of reducing the risks of pain, and osteoarthritis caused by changes in the loading of lower limb joints.

• Korean Journal of Applied Biomechanics
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• v.31 no.3
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• pp.205-213
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• 2021

Objective: The aim of this study was to analyze body stability Joint coordination pattern though as bending stiffness of shoes during stance phase of running. Method: 47 male subjects (Age: 26.33 ± 2.11 years, Height: 177.32 ± 4.31 cm, Weight: 65.8 ± 3.87 kg) participated in this study. All subjects tested wearing the same type of running shoes by classifying bending stiffness (A shoes: 3.2~4.1 N, B shoes: 9.25~10.53 N, C shoes: 20.22~21.59 N). They ran 10 m at 3.3 m/s (SD ±3%) speed, and the speed was monitored by installing a speedometer at 3 m intervals between force plate, and the measured data were analyzed five times. During running, ankle joint, MTP joint, coupling angle, inclination angle (anterior-posterior, medial-lateral) was collected and analyzed. Vector coding methods were used to calculate vector angle of 2 joint couples during running: MTP-Ankle joint frontal plane. All analyses were performed with SPSS 21.0 and for repeated measured ANOVA and Post-hoc was Bonferroni. Results: Results indicated that there was an interaction between three shoes and phases for MTP (Metatarsalphalangeal) joint angle (p = .045), the phases in the three shoes showed difference with heel strike~impact peak (p1) (p = .000), impact peak~active peak (p2) (p = .002), from active peak to half the distance to take-off until take-off (p4) (p = .032) except for active peak~from active peak to half the distance to take-off (p3) (p = .155). ML IA (medial-lateral inclination angle) for C shoes was increased than other shoes. The coupling angle of ankle angle and MTP joint showed that there was significantly difference of p2 (p = .005), p4 (p = .045), and the characteristics of C shoes were that single-joint pattern (ankle-phase, MTP-phase) was shown in each phase. Conclusion: In conclusion, by wearing high bending stiffness shoes, their body instability was increased during running.

• Clinics in Shoulder and Elbow
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• v.13 no.1
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• pp.141-145
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• 2010

Purpose: Understanding elbow biomechanics is necessary to understand the pathophysiologic mechanism of elbow injury and to provide a scientific basis for clinical practice. This article provides a summary of key concepts that are relevant to understanding common elbow injuries and their management. Materials and Methods: The biomechanics of the elbow joint can be divided into kinematics, stability and force transmission through the elbow joint. Active and passive stabilizers include bony articular geometry; soft tissues provide joint stability, compression force and motion. Results and Conclusion: Knowledge of elbow biomechanics will help (i) advance surgical procedures and trauma management, (ii) develop new elbow prostheses and (iii) stimulate future research.

• Journal of the Ergonomics Society of Korea
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• v.15 no.2
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• pp.15-24
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• 1996

To generate workspace analytically using the robot kinematics, data on range of human joints motion, especially range of two degrees of freedom motion, are needed. However, these data have not been investigated up to now. Therefore, in this research, we are to investigate an interaction effect of motions with two degrees of freedom occurred simultaneously at the shoulder, virtual hip(L5/S1) and hip joints, respectively, for 47 young male students. When motion with two degrees of freedom occurred at a joint such as shoulder, virtual hip and hip joints, it was found from the results of ANOVA that the action of a degree of freedom motion may either decrease or increase the effective functioning of the other degree of freedom motion. In other words, the shoulder flexion was decreased as the shoulder was adducted or abducted to $60^{\circ}C$TEX>or abducted from $60^{\circ}C$TEX>to maximum degree of abduction, while the shoulder flexion increased as the joint was abducted from $60^{\circ}C$TEX> to $60^{\circ}C$TEX> The flexion was decreased as the virtual hip was bent laterally at the virtual hip joint, and also did as the hip was adducted or abducted from the neutral position. It is expected that workspace can be generated more precisely based the data on the range of two degrees of joint motion measured in this study.

• The Journal of Korea Robotics Society
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• v.13 no.2
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• pp.129-141
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• 2018

This paper proposes a unified framework that overcomes four motion constraints including joint limit, kinematic singularity, algorithmic singularity and obstacles. The proposed framework is based on our previous works which can insert or remove tasks continuously using activation parameters and be applied to avoid joint limit and singularity. Additionally, we develop a method for avoiding obstacles and combine it into the framework to consider four motion constraints simultaneously. The performance of the proposed framework was demonstrated by simulation tests with considering four motion constraints. Results of the simulations verified the framework's effectiveness near joint limit, kinematic singularity, algorithmic singularity and obstacles. We also analyzed sensitivity of our algorithm near singularity when using closed loop inverse kinematics depending on magnitude of gain matrix.