• Earthquakes and Structures
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• 제8권1호
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• pp.205-224
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• 2015

A new method for designing moment resisting concrete frames failing in a global mode is presented in this paper. Starting from the analysis of the typical collapse mechanisms of frames subjected to horizontal forces, the method is based on the application of the kinematic theorem of plastic collapse. The beam section properties are assumed to be known quantities, because they are designed to resist vertical loads. As a consequence, the unknowns of the design problem are the column sections. They are determined by means of design conditions expressing that the kinematically admissible multiplier of the horizontal forces corresponding to the global mechanism has to be the smallest among all kinematically admissible multipliers. In addition, the proposed design method includes the influence of second-order effects. In particular, second-order effects can play an important role in the seismic design and can be accounted for by means of the mechanism equilibrium curves of the analysed collapse mechanism. The practical application of the proposed methodology is herein presented with reference to the design of a multi-storey frame whose pattern of yielding is validated by means of push-over analysis.

• 대한물리의학회지
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• 제7권1호
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• pp.69-75
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• 2012

Purpose : The study was designed to investigate analysis of kinematics of lower extremity in healthy adults during walking with external loads on trunk. Methods : Fifteen healthy adults were recruited and The subjects provided written and informed consent prior to participation. They walked on a ten-meter walkway at a self-selected pace with loads of 0, 5, 10, and 15kg. They completed three trials in each condition and kinematic changes were measured. A three-dimensional motion analysis system was used to analyze lower extremity kinematic data. The data collected by each way of walking task and analyzed by One-way ANOVA. Results : There were significant differences in hip and knee joint on saggittal plane at initial contact and preswing, and significant differences in ankle joint on transverse plane at preswing. Conclusion : These findings revealed that increased external loads were changed joint angles and influenced postural strategies because of kinematic mechanism and future studies is recommended to find out prevention from damage of activities of daily living.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.621-625
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• 2005

This paper presents a new hybrid serial-parallel robot(HSPR), which has six degrees of freedom driven by ball screw linear actuators and motored joints. This hybrid robot design presents a compromise between high rigidity of fully parallel manipulators and extended workspace of serial manipulators. The hybrid robot has a large, singularity-free workspace and high stiffness. Therefore, the presented kinematic structure of the hybrid robot is particularly suitable for multi-tasking machining processes such as milling, drilling, deburring and grinding. In addition to the machining processes, the hybrid robot can be used for welding, fixturing, material handling and so on. The study on design of the hybrid robot is performed. A kinematic analysis and mechanism description of the hybrid robot with six-controlled degree of freedom is presented. In the virtual design works by DADS, workspace and force analysis are discussed. A numerical model is treated to demonstrate our analysis and to determine the range of permissible extension of the struts. Also, we determine some important design parameters for the hybrid robot.

• 한국정밀공학회지
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• 제30권9호
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• pp.923-930
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• 2013

These days, the interests on the high speed handling robots are increasing because it is important to get down the unit cost of production to get the price competitiveness. The parallel kinematic mechanism is more suitable to implement the high speed robot system as well known. The moving parts of the high speed parallel robot have to be designed for light weight. But the vibration motion is induced by the light weight links because they drive in high acceleration and deceleration. In this reason, the structural analysis of the high speed parallel kinematic robot is very important in the design process. In this paper, the study on the structural analysis of a high speed parallel robot has been done and the research results will be introduced.

• 대한기계학회논문집
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• 제18권2호
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• pp.351-358
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• 1994

A probabilistic model and analysis methods to determine the means and variances of the velocity and acceleration in stochastically-defined planar pin jointed kinematic chains are presented. The presented model considers the effect of tolerances on link length and radial clearance and uncertainty of pin location as a net effect on the link's effective length. The determination of the mean values and variances of the output variables requires the calculation of sensitivities of secondary variables with respect to the random variables. It is shown that this computation is straightforward and can be accomplished by a conventional kinematic analysis package with minor modification. Thus, the concepts of tolerance and clearance have been captured by the model and analysis. The only input data are the nominal linkage model and statistical information. The "effective link length" model is shown to be applicable to both analytical solution and Monte Carlo simulation. The results from both methods are compared. This paper Ksolves the higher-order kinematic problems for the probabilistic design analysis of stochastically-defined mechanisms.echanisms.

• 한국운동역학회지
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• 제29권4호
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• pp.219-226
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• 2019

Objective: The purpose of this study is to provide a better understanding of short turn mechanism by describing short turns after kinematic analysis and provide skiers and winter sports instructors with data through which they are able to analyze right postures for turns in skiing in a systematic, rational and scientific manner. Method: For this, a mean difference of kinematic variables (ski-hip angle, ski-shoulder twist angle, pole checking angle, the center of gravity (CG) displacement, trunk forward lean angle) was verified against a total of 12 skiers (skilled and unskilled, 6 persons each), regarding motions from the up-start to down-end points for short turns. Results: There was no difference in a ski-hip twist angle. The ski-shoulder twist angle was large at the up-start point while a pole-checking angle was high at the down-end point in skilled skiers. Concerning the horizontal displacement of CG, skilled skiers were positioned on the right side at the upstart point. No significant difference was observed in the trunk forward lean angle. Conclusion: According to the ski-shoulder twist angle and CG horizontal displacement results, the upper body should be kept leant toward the pole. In addition, big turns should be made via edging and angulation. During pole checking, the hand holding the pole should be thrown and released toward a vector direction of the forearm.

• 한국철도학회논문집
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• 제8권6호
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• pp.500-506
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• 2005

The development of tilting train has been required for speed-up on the conventional electric railroad due to the characteristic of Korean railroad with a lot of curve track. The study and development of a tilting system and a tilting bogie which have a different mechanism with high speed train will play a important role for enhancement of technology for Korean railway. The study for tilting pantograph mechanism to decrease the displacement between a catenary and a center of pantograph happened when the carbody is tilted in order to maintain the ride comfort and stability m a curving track is proceeding with the development of tilting train. In this paper, we introduce the design concept for the tilting mechanism of pantograph and the role and characteristics for several devices adopted in the tilting mechanism of pantograph. Through the kinematic analysis of tilting mechanism, we will obtain and calculate the optimal tilting angular velocity and acceleration in order to keep the contact behavior of a pantograph and a catenary according to tilting of a carbody.

• 대한기계학회논문집
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• 제18권11호
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• pp.2846-2859
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• 1994

This work deals with kinematic analysis of fault-tolerant 3 degree-of-freedom spherical modules which have force redundancies in its parallel structure. The performance of a redundantly actuated four-legged module with no actuator failure, a single actuator failure, partial and half failure of dual actuator are compared to that of a three-legged module, in terms of maximum force transmission ratio, isotropic characteristics, and fault-tolerant capability. Additionally, a system with an excess number of small floating actuators is considered, and the contribution of these small actuators to the force transmission and fault-tolerant capability is evaluated. This study illustrates that the redundant actuation mode allows significant saving of input actuation effort, and also delivers a fault tolerance.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.711-714
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• 2001

As the life cycle of the vehicle become shorter, the method that reduce the development time of new model become more important. In this reason, the development of the simulator that provides similar environment with the actual vehicle road characteristics is increasing. In this paper, the multi-axis simulator is designed and analyzed by kinematic method. The simulator has a function simulating the 3 load elements; vertical, longitudinal, and lateral force respectively and simultaneously. The result of this paper can be used for developing the multi-axis simulator linkage.

• 한국정밀공학회지
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• 제15권1호
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• pp.60-68
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• 1998

Parallel link manipulators have an ability of more precise positioning than serial open-loop manipulators. However. general parallel link manipulators have been restricted to the real applications since they have limited workspace due to interference among actuators. In this study, we suggest a closed-loop manipulator with 6 degrees-of-freedom and with enlarged workspace. It consists of two parts for minimizing the interference among actuators. One part is lower structure with planar 3 degrees-of-freedom and the other is upper one with spatial 3 degrees-of-freedom. Forward kinematics and inverse kinematics are solved, research about singularity points are carried out and workspace is evaluated. The comparison of workspace between Stewart platform, which is the typical parallel link manipulator, and the suggested manipulator shows that the workspace of the latter is wider than that of the former. Especially, simulation results also show that the suggested manipulator is more suitable when there needs rotation in the end-effector.