• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.4
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• pp.129-140
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• 1998

A numerical method is proposed to optimize automotive cam profiles. An acceleration curve of a cam follower motion is described by Hermite spline curves. Because of the intrinsic characteristics of the Hermite curve, it is possible to design an acceleration curve with arbitrary shape. Design variables in the optimization problem are location of control points which define the acceleration curve. Objective function includes dynamic performances as well as kinematic properties of a valve train. Similar optimization procedure was also performed using Polydyne cam profile synthesis method. Optimized profiles using the Hermite curve are proved to be superior to those using the Polydyne method.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.10a
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• pp.153-159
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• 1999

A material handling crane is composed of many complex structural components which require sufficient strength, stiffness and stability throughout its service life and need to be light in weight, and satisfy the required functions under the entire range of operating conditions. In this study, the analysis system for material handling cranes is presented. This program integrate various structural analyses modules with the GU(Graphic User Interface) concept. Utilizing basic variables as input data, the analysis system performs quasi-static, eigenvalue, buckling, fatigue and stability analysis. Using this program, the designer can generate optimal design data for the cranes without my actual measurements. This system will also be extended to other mechanical structures with kinematic motion like crane.

• Journal of the Ergonomics Society of Korea
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• v.17 no.2
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• pp.11-23
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• 1998

Dynamic motion difference between normal subjects and low-back pain (LBP) patients has been investigated in terms of kinematic variables such as range of motion, velocity and acceleration of the back and hip. Ten healthy subjects and ten LBP patients were recruited in this study. Electro-goniometer such as Lumbar Motion Monitor and Hip Monitor have been used for quantitative measurement of the trunk motion during repetitive flexion and extension for ten seconds. Results indicated that the velocity and acceleration of the back and hip were important parameters to quantitatively identify LBP patients. The consistency of cyclic trunk motion and the relationship between the back and hip were measured in terms of Variance Ratio and Phase Angle in order to accurately assess the motion characteristics of LBP patients. In particular, the hip motion has been proven to be a very important factor in describing the kinematics of damaged lower back. The functional evaluation technique suggested in this study will be a tool to assist physicians for an accurate diagnosis and timely rehabilitation along with current image diagnosis techniques.

• Korean Journal of Applied Biomechanics
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• v.24 no.4
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• pp.455-461
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• 2014

The purposes of this study were to reveal the kinematic and kinetic difference of hard ground soccer shoe, firm ground soccer shoe and soft ground soccer shoe. Soccer players were shoes of varying stud designs with some preferring the bladed studs while others opting for the conventional studded stud. Statistics were used one way-ANOVA and Tukey's Honestly Significant Difference Method. Seven healthy college soccer players were attended a test. All parameters were recorded using the Zebris system. Spatio-temporal variables were no significant difference. Lateral symmetry was statistically significant differences (p<.05). Vertical GRF parameters were no significant difference. Medial midfoot pressure, lateral midfoot pressure and central forefoot pressure were statistically significant differences (p<.05). This study demonstrates that playing surface significantly affects difference soccer shoes during soccer game. Furthermore, epidemiological investigation is warranted to determine the effects of playing surfaces on sport specific injury mechanisms.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.66.6-66
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• 2001

In this paper, we studied the error compensation using an error budget method for repeatability improvement of the precision positioning system. The precision positioning system is developed for micro-pressing machine. We performed the force and displacement analysis about parts of the system. Proposed system determines the position and orientation of the materials manufactured by micro-pressing machine. It is consisted of x-y-z linear stages setting the position, and the gripper system setting the orientation. We executed kinematic and dynamic modeling of the whole precision positioning system. By generalizing the design variables, precision positioning system has the flexibility of material dimension. As we tried an error compensation using ...

• Korean Journal of Applied Biomechanics
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• v.14 no.3
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• pp.235-257
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• 2004

The purpose of this study was to analyze the kinematical traits variables when performing Uchimata(inner thigh reaping throw) by Voluntary Resistance Levels(VRL) and two postures of Uke in Judo. The subjects, who were one male judoka(YH) for 1992 Barcelona Olympic Games, and one male trainee Y. I. University representative member(SDK) and were filmed on two S-VHS 16 mm video cameras(60fields/sec.), that posture of Uke were Shizenhontai(straight defensive posture) and Jigohontai(straight natural posture), VRL of Uke were 0% and 100%. The kinematical variables were temporal(total time-required: TR), potures and COG variables etc., The data of this study collection were digitized by SIMI Motion Program computed the mean values and the standard deviation calculated for each variables. When performing according to each posture and VRL, from the data analysis and discussion, the conclusions were as follows : 1. Temporal variables total time-required(TR) when performing Uchimata was shown the shortest time YH than SDK by each posture and VRL. TR of each posture were shown the shorten trends or equal in DP by lower than NP, In existence and / or nonexistence of VRL was shown the shorten trends in VRL 0% than 100% of Uke. 2. Posture variables : In attacking right knee angle, YH was performing flexion($147{\rightarrow}103degree$) from Tsukuri(set-up) to Kake(execution) in regardless of postures and VRLs, SDK was performing not exchange extension and flexion in VRL 100%, and extension($120{\rightarrow}142degree$) in VRL 0%, respectively. In supporting left hee angle, YH was performing extension($119{\rightarrow}163degree$) from Tsukuri(set-up) to Kake(at(execution) in regardless of postures and VRLs, SDK extension($93{\rightarrow}139degree$), respectively. In attacking right hip angle, from Tsukuri to Kake, YH was performing extension($133{\rightarrow}169degree$), except in VRL 0%($156{\rightarrow}137degree$) NP, SDK was performing flexion($159{\rightarrow}126degree$) accept in VRL 100%($149{\rightarrow}152degree$) NP, In left hip angle, from Tsukuri to Kake, YH was performing flexion NP(70, 50degree) more than DP(27, 57degree), SDK was performing flexion DP(73, 52degree) more than NP(34, 20degree). 3. COG variables : When performing Uchimata, vertical COG variables was shown YH(:$2{\sim}8cm$), SDK(:$15{\sim}24cm$) lower than Uke's COG level position, in existence and / or nonexistence of postures and VRL, during Kake as maximum force point of throwing techniques in Judo.

• Korean Journal of Applied Biomechanics
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• v.14 no.3
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• pp.1-15
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• 2004

The purpose of this study was to investigate the kinematic variables of the upper part of the body for 8 elderly men during walking. For this study, kinematic data were collected using a six-camera (240Hz) Qualisys ProReflex system. The room coordinate system was right-handed and fixed in space, with righted orthogonal segment coordinate systems defined for the head, trunk, and pelvis. Based on a rigid body model, reflective marker triads were attached on the 3 segments. Three-dimensional Cartesian coordinates for each marker were determined at the time of recording using a nonlinear transformation(NLT) technique with ProReflex software (Qualisys, Inc.). Coordinate data were low-pass filtered using a fourth-order Butterworth with cutoff frequency of 6Hz. Three-dimensional angles of the head, trunk, and pelvis segment were determined using a Cardan method. On the basis of each segment angle, angle-angle plot used to estimated the movement coordinations between segments. The conclusions were as follows; (1) During the support phase of walking, the elderly people generally kept their, head the flexional and abductional posture. Particularly, the elderly displayed little internal/external rotation. (2) The elderly people showed extensional and external rotation postures in the trunk movement. Particularly, It showed the change from adduction into abduction at the heel contact event of the stance phase. (3) The elderly people showed almost same pelvis movement from the flexion into extension, from the abduction into adduction, and from internal rotation into external rotation at the mid stance and toe off of the stance phase.

• Korean Journal of Applied Biomechanics
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• v.21 no.4
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• pp.421-427
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• 2011

The purpose of this study was to analyze the difference between male and female tennis players' two-handed backhand stroke and to provide basic data which helps precise and efficient instruction for the sake of precise postures, enhanced performances and skills. 5 male and 5 female university players were recruited as subjects, and the mean difference between the kinematic variables such as the time from backswing to impact and total swing time, racket head velocity, change of the center of body gravity in two-handed backhand stroke through three-dimensional motion analysis. The test data was analyzed by t-test, and the alpha level of ${\alpha}$=.05 was set for all tests of significance. The findings of the study were as follows; First, there was no difference in the time from backswing to impact and total time of

• Journal of Drive and Control
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• v.13 no.4
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• pp.14-22
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• 2016

This paper presents a stochastic and predictive working-risk-assessment algorithm for excavators based on a one-layer laser scanner. The one-layer laser scanner is employed to detect objects and to estimate an object's dynamic behaviors such as the position, velocity, heading angle, and heading rate. To estimate the state variables, extended and linear Kalman filters are applied in consideration of laser-scanner information as the measurements. The excavator's working area is derived based on a kinematic analysis of the excavator's working parts. With the estimated dynamic behaviors and the kinematic analysis of the excavator's working parts, an object's behavior and the excavator's working area such as the maximum, actual, and predicted areas are computed for a working risk assessment. The four working-risk levels are defined using the predicted behavior and the working area, and the intersection-area-based quantitative-risk level has been computed. An actual test-data-based performance evaluation of the designed stochastic and predictive risk-assessment algorithm is conducted using a typical working scenario. The results show that the algorithm can evaluate the working-risk levels of the excavator during its operation.

• Korean Journal of Applied Biomechanics
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• v.18 no.1
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• pp.97-105
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• 2008

The kinematic variables for swimming and fin-swimming start motions were analyzed and compared using 3-dimensional cinematography. For the swimming start, the arm segment moved towards the upper rear and trunk towards the upper front followed by a descent towards the lower front, while the fin-swimming start motion showed movement towards the lower front for all segments. The total body center of gravity for the swimming start showed horizontal movement far to the front followed by a rapid descent while the fin-swimming start showed close movement towards the lower front in a short period of time. Upon entering the water, the center of gravity for swimming showed high vertical velocities while fin swimming had high horizontal velocities. For both swimming and fin swimming, the upper extremity velocity had more influence on the total center of gravity velocity than the lower extremities. Flexion of the hip joint was observed before the jump for the fin swimming start while the swimming start showed two flexions in mid-air succeeding the jump. The flexion and extension movements at the knee joint during the fin-swimming start motion were shown to be larger and more rapid than those of fin-swimming.