• IE interfaces
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• v.23 no.2
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• pp.100-107
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• 2010

For proper ergonomic evaluation using a digital human model simulation (DHMS) system such as $RAMSIS^{(R)}$, the postures of humanoids for designated tasks need to be predicted accurately. The present study (1) evaluated the accuracy of driving postures of humanoids predicted by RAMSIS, (2) proposed a method to improve its accuracy, and (3) examined the effectiveness of the proposed method. The driving postures of 12 participants in a seating buck were measured by a motion capture system and compared with their corresponding postures predicted by RAMSIS. Significant discrepancies ($8.7^{\circ}$ to $74.9^{\circ}$) between predicted and measured postures were observed for different body parts and driving tasks. Two methods (constraints addition and user-defined posture) were proposed and their effects on posture estimation accuracy were examined. Of the two proposed methods, the user-defined posture method was found preferred, reducing posture estimation errors by 11.5% to 84.9%. Both the posture prediction accuracy assessment protocol and user-defined posture method would be of use for practitioners to improve the accuracy of predicted postures of humanoids in virtual environments.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.1
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• pp.121-126
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• 2013

Cycloconverter used as a power conversion device in the speed and torque control system of AC machines has the advantage of a simple control and a large torque at low speed. In addition, because a rectifier, a DC link, and an inverter are not installed, this system is simple and suitable for large power system. If a power conversion device, which is currently used as a propulsion motor of large vessel, is changed into cycloconverter, the system is simplified and then the installation costs can be significantly reduced. However, conventional cycloconverter has the increased harmonics because the power loss is large and the waveform of output voltage is distorted, due to the high-speed switching of power semiconductor devices. In order to improve these shortcomings, this paper describes a phase shifting filter which is composed of two inputs with different phases in the primary side and one output in the secondary one. As the voltage waveforms with two different phases are added and transformed into the secondary side, these outputs are close to sinusoidal waves. Thereby the voltage waveforms, which are applied to the propulsion motors, are improved and total harmonic distortions (THDs) are significantly reduced.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.12
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• pp.1925-1930
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• 2010

For high-speed/high-accuracy position control of a gantry-moving-type linear motor, we propose a nonlinear adaptive controller including a synchronization algorithm. Linear motors are easily affected by force ripple, friction, and parameter variations because there is no mechanical transmission to reduce the effects of model uncertainties and external disturbances. Synchronization error is also caused by skew motion, model uncertainties, and force disturbance on each axis. Nonlinear effects such as friction and ripple force are estimated and compensated for. The synchronization algorithm is used to reduce the synchronous error of the two side pillars. The performance of the controller is evaluated via computer simulations.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.11
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• pp.1433-1439
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• 2012

This paper introduces a sensor system based on indoor locations in order to implement the Building Energy Management System. This system consists of a thermopile sensor and an ultrasonic sensor. The sensor module is rotated by $360^{\circ}$ and yawed up-and-down by two electric motors. Therefore, it can simultaneously detect the number and location of the inhabitants in the room. It uses wireless technology to communicate with the building manager or the smart-home server, and it can save electric energy by controlling the lighting system or heating/air conditioning equipment automatically. We also demonstrate the usefulness of the proposed system by applying it to a real environment.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.4
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• pp.194-201
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• 2004

Optical fibers are indispensable fer optical communication systems that transmit large volumes of data at high speed. But the aligning technology under the sub-micron accuracy is required for the precise axis adjustment and connection. For the purpose of precise alignment of the optical arrays, in this research, we have developed the 12-axis(with 8 automated axis and 4 manual axis) automatic optical fiber alignment system including the image processing-based searching system, the automatic loading system using the robot and the suction toot and the automatic UV bonding system. In order to obtain the sub-micron alignment accuracy, two 4-axis PC-based motion controllers and the two 50nm resolution 6-aixs micro-stage actuated by micro stepping motors are adopted. The fiber aligning procedure consists of two steps. Firstly, the optical wave guide and an input optical array are aligned by the 6-axis input micro-stage with the IR camera. The image processing technique is introduced to reduce primary manual aligning time and result in achieving the 50% decrease of aligning time. Secondly, the IR camera is replaced by the output micro-stage and a wave guide and two optical arrays are aligned simultaneously before the laser power intensity delivered to the optical powermeter reached the threshold value. When the aligning procedure is finished, the wave guide and arrays are W bonded. The automatic loading/unloading system is also introduced and the entire wave guide handing time is reduced significantly compared to the former commercial aligning system.

• International Journal of Aeronautical and Space Sciences
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• v.8 no.2
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• pp.11-16
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• 2007

This paper describes the cycloidal wind turbine, which is a straight blade vertical axis wind turbine using the cycloidal blade system. Cycloidal blade system consists of several blades rotating about an axis in parallel direction. Each blade changes its pitch angle periodically. Cycloidal wind turbine is different from the previous turbines. The wind turbine operates with optimum rotating forces through active control of the blade to change pitch angle and phase angle according to the changes of wind direction and wind speed. Various numerical experiments were conducted to develop a small vertical axis wind turbine of 1 kW class. For this numerical analysis, the rotor system equips four blades consisting of a symmetric airfoil NACA0018 of 1.0m in span, 0.22m in chord and 1.0m in radius. A general purpose commercial CFD program, STAR-CD, was used for numerical analysis. PCL of MSC/PATRAN was used for efficient parametric auto mesh generation. Variables of wind speed, pitch angle, phase angle and rotating speed were set in the numerical experiments. The generated power was obtained according to the various combinations of these variables. Optimal pitch angle and phase angle of cycloidal blade system were obtained according to the change of the wind direction and the wind speed. Based on data obtained from the above analysis, control device was designed. The wind direction and the wind speed were sensed by a wind indicator and an anemometer. Each blades were actuated to optimal performance values by servo motors.

• Journal of Korea Society of Industrial Information Systems
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• v.17 no.7
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• pp.35-41
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• 2012

To control screen door installed in the subway platform, geared BLDC motors have been being used. However, because of the geared mechanisms, the control profile of the screen door in slow speed is very poor. Moreover, geared mechanism tends to leads system malfunctions and low efficiency. To overcome those problems, in this paper, the techniques of developing hi-efficiency direct drive gearless PMAC motor controller and application example to control the screen door of subway platforms are proposed. The developed system has advantages that; the energy efficiency has been increased by adopting gearless PMAC motor; the system break-down factor has been decreased due to the actuator mechanism has been simplified. In this paper, the screen door control system structure, PMAC motor drive circuit design, implementations of vector control algorithm, and test results are shown.

• Journal of Powder Materials
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• v.23 no.5
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• pp.391-396
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• 2016

In this study, ultra-fine soft-magnetic micro-powders are prepared by high-pressure gas atomization of an Fe-based alloy, Fe-Hf-B-Nb-P-C. Spherical powders are successfully obtained by disintegration of the alloy melts under high-pressure He or $N_2$ gas. The mean particle diameter of the obtained powders is $25.7{\mu}m$ and $42.1{\mu}m$ for He and $N_2$ gas, respectively. Their crystallographic structure is confirmed to be amorphous throughout the interior when the particle diameter is less than $45{\mu}m$. The prepared powders show excellent soft magnetic properties with a saturation magnetization of 164.5 emu/g and a coercivity of 9.0 Oe. Finally, a toroidal core is fabricated for measuring the magnetic permeability, and a ${\mu}_r$ of up to 78.5 is obtained. It is strongly believed that soft magnetic powders prepared by gas atomization will be beneficial in the fabrication of high-performance devices, including inductors and motors.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.5
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• pp.118-124
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• 2007

The efficiency of the hybrid systems which are composed of compound planetary gear sets depend on the amount of the recirculating energy among the motors and battery. This paper studies the analysis of the system efficiency with the parameters, ${\alpha},\;{\beta},\;{\gamma_a},\;{\gamma_b}$ and $\gamma_s$. The efficiency of the systems and the relative torque, speed and power of the power resources are represented by these parameters. The recuperating parameter $\kappa$ which makes the systems generalized is introduced, so the efficiencies of the modes such as the hybrid mode, the engine mode, the motoring mode and the recuperating mode are analyzed with simple equations. The tendency of the system efficiency according to the variations of the $\gamma_s$ and $\kappa$ are studied, by which it can be possible to reduce the loss of the power because the strategies for avoiding the singular speed ratio $\gamma_s$ are helpful for the system efficiency and specific value of $\kappa$ can increase the efficiency of the systems.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.2
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• pp.15-21
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• 2007

The aim of this paper is controlling ignition timing and load in homogeneous charge compression ignition (HCCI) combustion with low cetane number fuel, hydrogen. Homogeneous charge compression ignition (HCCI) combustion is an advanced combustion technology that achieves higher thermal efficiency and lower $NO_x$ emissions than that of conventional combustion system. Dimethyl ether (DME), which has been researched widely as the most attractive alternative fuel of diesel, is attractive for HCCI combustion because of the easy evaporation. In this study, the single cylinder DME engine operated with a direct injection system has been used to investigate combustion processes and emissions of DME HCCI with a premixed hydrogen supply. The experiment was carried out under various engine speed and fraction rates of hydrogen. As a result, the increase of fraction rates of hydrogen retard the DME ignition timing and eliminated the knocking during high engine speed condition. IMEP was increased with increase of fraction rates of hydrogen by 30%. 40% of the fraction rates of hydrogen resulted in misfiring. The $NO_x$ emission was reduced by increasing the fraction rates of hydrogen, but HC emission was increased.