• Journal of Institute of Control, Robotics and Systems
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• v.14 no.10
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• pp.1038-1046
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• 2008

This paper presents a framework to generate human-like movements of a humanoid in real time using the movement primitive database of a human. The framework consists of two processes: 1) the offline motion imitation learning based on an Evolutionary Algorithm and 2) the online motion generation of a humanoid using the database updated bγ the motion imitation teaming. For the offline process, the initial database contains the kinetic characteristics of a human, since it is full of human's captured motions. The database then develops through the proposed framework of motion teaming based on an Evolutionary Algorithm, having the kinetic characteristics of a humanoid in aspect of minimal torque or joint jerk. The humanoid generates human-like movements far a given purpose in real time by linearly interpolating the primitive motions in the developed database. The movement of catching a ball was examined in simulation.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.5
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• pp.507-512
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• 2013

This paper proposes a new model to compensate for errors of a five-axis machine tool. A matrix with error components, that is, an error matrix, is separated from the error synthesis model of a five-axis machine tool. Based on the kinematics and inversion of the error matrix which can be obtained not by using a numerical method, an error compensation model is established and used to calculate compensation values of joint variables. The proposed compensation model does not need numerical methods to find the compensation values from the error compensation model, which includes nonlinear equations. An experiment using a double ball-bar is implemented to verify the proposed model.

• Korean Journal of Applied Biomechanics
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• v.13 no.3
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• pp.217-229
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• 2003

The purpose of this study was to present the basic data on improving the skills for 3 junior high school national badminton players in clear and drop motion through the 3-dimensional image analysis. Therefore, the results of this study are as follows: 1. In the duration times per phase, subject C relatively showed a similar time between clear and drop motion. Accordingly, C took a more effective motion than A and B. 2. In the velocities of racket head, subject A and C showed similar changes relatively. However, in case of subject B, the velocity was decreased before back swing(E2) and increased until impact(E3). 3. Regardless of clear and drop motion, the changing phases of joint angle for wrist and elbow showed similar changes comparatively. 4. In the angles of upper body, clear motion was average 85.0 degree and drop one was average 80.7 degree during the impact(E3). Hence, it showed that drop motion hit the ball bowing the upper body more than clear one. 5. In the angles of racket head, clear motion was average 87.7 degree and drop one was average 85.6 degree during the impact(E3). Consequently, drop motion was impacted forward more than clear one.

• Tribology and Lubricants
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• v.26 no.1
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• pp.61-67
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• 2010

The purpose of this paper is to study and analyze the failure examples on tribological characteristics of an automotive steering system. In this failure study, the grease leakage may stick leaked grease, dust, and wear particles between pinion and rack gears in mechanical steering system. In the case of seal failures such as a rod seal, o-ring and oil seals, the gear box and oil pump do not operate properly due to lack of oils. This means that oil pump does not supply a working fluid and produce a normal oil pressure of the steering system. This leads to leak a working fluid from the seals and produce a wear between pinion and rack gears. Especially, the leaked oil is usually mixed with internal wear particles and foreign dust/fine sands. Thus no leakage of working oils is very important design concepts, which is strongly related to the sealing components and smoothly operating of the mechanical friction parts of power steering system.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.2
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• pp.343-350
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• 2008

In this paper, a six degree-of-freedom robot arm which is very light but capable of delivering heavy loads was studied. The proposed robot arm has much higher load capacity than conventional robot arms actuated by motors with speed reducers such as the harmonic drive since a new type of robot actuator based on a closed chain mechanism driven by the ball screw was adopted. Analysis on the design scheme and on the mechanism of the joint actuator of the robot arm were made. Since the robot arm was designed very light, it has deflection in the links. To analyze this, a finite element analysis on the structure of the designed robot links was made using ANSYS software. Verifying experiments on the performance of high load capacity of the robot arm was performed by loading heavy weights on the robot arm. Through experiments. the correctness of the numerical analysis was also verified.

• International Journal of Automotive Technology
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• v.8 no.6
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• pp.745-752
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• 2007

In this study, the effects of flexible bodies in vehicle suspension components were investigated to enhance the accuracy of multibody dynamic simulation results. Front and rear suspension components were investigated. Subframes, a stabilizer bar, a tie rod, a front lower control arm, a front knuckle, and front struts were selected. Reverse engineering techniques were used to construct a virtual vehicle model. Hard points and inertia data of the components were measured with surface scanning equipment. The mechanical characteristics of bushings and dampers were obtained from experiments. Reaction forces calculated from the multibody dynamics simulations were compared with test results at the ball joint of the lower control arm in both time-history and range-pair counting plots. Simulation results showed that the flexibility of the strut component had considerable influence on the lateral reaction force. Among the suspension components, the flexibility of the sub-frame, steering knuckle and upper strut resulted in better correlations with test results while the other flexible bodies could be neglected.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.5
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• pp.199-205
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• 2002

The scale of repair parts market reached 0.1 billion won. Above all, it is remarkable that the automotive insurance business world is paying f3r 40 ~5o% of the whole repair cost. The repair parts consist of a genuine parts, non-genuine parts, recycling used parts. It is the recent trend that recycled parts are more popular than the genuine parts f3r repairing crashed cars due to the cost. Performance of recycled continuous velocity(CV) joints and power steering(PS) gear box as replacement parts was tested and analysed in this study. To examine the durability of the recycled parts, the replaced CV joints and PS gear box after repair were tested and analysed periodically. The results were showed that basic performance of the recycled parts was normal. However the ball cage of CV joints was more frequently damaged than genuine parts. We concluded that a test standard and amendment of related laws for recycled parts is required to get a safe and durable parts.

• Korean Journal of Applied Biomechanics
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• v.28 no.3
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• pp.187-191
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• 2018

Objective: The purpose of the present study is to investigate the effect of a muscle activity by applying the complex exercise method of sling in accordance with the provision of various vibration intensities for paraplegia-spinal cord injury. Method: The subjects of the study were 15 men in their 40s and 50s with lower limb disabilities and low potential risk, who were randomly divided into a sling exercise group (SG n=4), a sling with low frequency vibration group (SLVG n=4), a sling with mid-frequency vibration group (SMVG n=4), and a sling with high frequency group (SHVG n=4) in accordance with the provision of slings and vibration stimuli. The vibratory intensity provided was divided into low frequency (30 Hz), mid-frequency (50 Hz), and high frequency (70 Hz). The anterior deltoid (AD), the posterior deltoid (PD), the pectoralis major (PM), the upper trapezius (UT), the latissimus dorsi (LD), and the multifidus (MF) were measured to compare and analyze muscle activity. Results: The closed kinetic chain (CKC) exercise to the shoulder joint showed higher muscle activity in most muscles for the SMVG, and statistically significant differences in the anterior deltoid (AD), the pectoralis major (PM), and the multifidus (MF) in particular. Conclusion: The intermediate frequency (50 Hz) string vibration was the effective vibration stimuli for Closed kinetic chain (CKC) exercises.

• Steel and Composite Structures
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• v.25 no.5
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• pp.571-579
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• 2017

The grid structure with bolt-sphere joints is widely adopted by industrial plants with suspending crane. The alternating reciprocating action of the suspending crane will cause fatigue problems of the grid structure with bolt-sphere joints with respect to the rod, the cone, the sealing plate, the bolt ball and the high strength bolt; while the fatigue of the high strength bolt is the key issue of fatigue failure. Based on efficient and smooth loading equipment with the AMSLER fatigue testing machine, this paper conducted a constant amplitude fatigue test on 18 M20 and 14 M30 high strength bolts with 40Cr material, and obtained 19 valid failure points, 9 unspoiled points with more than 2 million cycles, and 4 abnormal failure points. In addition, it established the constant amplitude fatigue design method, ${[{\Delta}{\sigma}]_{{2{\times}10}}{^6=58.91MPa}$, and analyzed the stress concentration and the fatigue fracture of high strength bolts. It can be explained that the geometrical stress concentration of high-strength bolt caused by spiral burr is severe.

• Journal of the Korean Society for Precision Engineering
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• v.34 no.4
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• pp.243-246
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• 2017

In this study, flexible fixtures and end effectors are conceptually designed for the holding of thin-walled carbon-fiber reinforced-plastic (CFRP) workpieces in machining processes. Firstly, the fixture scenarios and system requirements for the conceptual designs of flexible-fixture and core units are proposed, including the propounding of the workpiece-holding mechanism and the core-unit requirements. A ball-joint pneumatic system is determined as a locking mechanism of the flexible-fixture system for the machining of thin-walled components. Secondly, conceptual designs of the core units are suggested with the driven requirements from the fixture scenarios. A self-tilting mechanism and an end-effector return mechanism are also proposed. Finally, the prototypes of the core units are manufactured, and the workpiece-holding capacity of each prototype is measured.