• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.101-103
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• 2006

외전형 유도전동기 모터는 내전형에 비해 소형화 및 경량화 시킬 수 있는 장점이 있다. 하지만 회전자와 고정자간의 공극사이에 이심률이 있을 때, 불균형 모멘트로 인한 토크 리플이 내 전형보다 더 크게 일어나는 단점이 있다. 이러한 토크리플은 모터의 정속적인 운전을 방해시킬 뿐만 아니라 불규칙한 출력토크로 인한 작동상의 오류를 초래한다. 본 논문에서는 의전형 모터에서 이심률에 따른 불균형력이 최소화 될 수 있는 슬롯 형태에 대해서 연구하기 위해, 전폐형, 반폐형, 개구형태의 3가지 슬롯 형태에 대한 특성을 비교 하였다. 개구형의 경우 슬롯 누설 리액턴스가 낮아져 토크 형성율이 매우 높아 높은 토크를 발생시킬 것을 예상 하였지만, 토크 리플에 따른 출력 감소로 오히려 출력토크가 감소할 뿐만 아니라 이심률 증가에 따른 불균형력 또한 매우 컸다. 이에 비해 전폐형태의 슬롯은 누설리엑턴스의 영향으로 토크 형성 자체는 10% 정도 저감 되었으나, 이심률 증가에 따른 분균형력이 가장 적어 의전형 모터에 가장 적함한 형태임을 알 수 있었다.

• 대한기계학회논문집A
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• 제33권10호
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• pp.1029-1037
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• 2009

Recently, the technologies of mobile robots have been growing rapidly in the fields such as cleaning robot, explosive ordnance disposal robot, patrol robot, etc. However, the researches about the autonomous underwater robots have not been done so much, and they still remain at the low level of technology. This paper describes a model of 3-joint (4 links) fish robot type. Then we calculate the dynamic motion equation of this fish robot and use Singular Value Decomposition (SVD) method to reduce the divergence of fish robot's motion when it operates in the underwater environment. And also, we analysis response characteristic of fish robot according to the parameters of input torque function and compare characteristic of fish robot with 3 joint and fish robot with 2 joint. Next, fish robot's maximum velocity is optimized by using the combination of Hill Climbing Algorithm (HCA) and Genetic Algorithm (GA). HCA is used to generate the good initial population for GA and then use GA is used to find the optimal parameters set that give maximum propulsion power in order to make fish robot swim at the fastest velocity.

• Journal of Electrical Engineering and Technology
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• 제12권5호
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• pp.1842-1850
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• 2017

Reducing the noise and vibration of the BLDC motors is very essential for some special applications. In this paper, a new structural design is introduced to increase the natural frequencies of the stator in BLDC motors as increasing the natural frequencies can reduce the severe effects of the structural resonances, including high levels of noise and vibration. The design is based on placing a single hole on definite regions at the stator cross sectional area (each region contains one tooth and its upper parts in the stator yoke) in an optimum way by which the natural frequencies at different modes are shifted to the higher values. The optimum diameter and locations for the holes are extracted by the Response Surface Methodology (RSM) and the modal analyses in the iterative process are done by Finite Element Method (FEM). Moreover, the motor performance by the optimum stator structure is analyzed by FEM and compared with the prototype motor. Preventing the stator magnetic saturation and the motor cogging torque enhancement are the two constraints of the optimization problem. The optimal structural design method is applied experimentally and the validity of the design method is confirmed by the simulated and experimental results.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권3호
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• pp.246-255
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• 2017

The proposed design methodology represents a new approach to optimize the propeller-hull system simultaneously. In this paper, two objective functions are considered, the first objective function is Lifetime Fuel Consumption (LFC) and the other one is cost function including thrust, torque, open water and skew efficiencies. The variables of the propeller geometries (Z, EAR, P/D and D) and ship hull parameters (L/B, B/T, T and $C_B$) are considered to be optimized with cavitation, blades stress of propeller. The well-known evolutionary algorithm based on NSGA-II is employed to optimize a multi-objective problem, where the main propeller and hull dimensions are considered as design variables. The results are presented for a series 60 ship with B-series propeller. The results showed that the proposed method is an appropriate and effective approach for simultaneously propeller-hull system design and is able to minimize both of the objective functions significantly.

• 한국기계가공학회지
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• 제16권3호
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• pp.113-118
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• 2017

In this paper, a study on the performance evaluation of a cycloid reducer for remote weapons systems is presented. Reduction gears applied to remote weapons vehicles need to be compact and capable of large torque transmissions as well as require structural optimization, high load capacity, and high precision position control. To meet these requirements, a cycloid reducer with low backlash, high precision, high overload capability, high rigidity, and high efficiency is required. Thus, a cycloid reducer with a reduction ratio of 127:1, backlash of 1 arcmin (1/60 deg) or less, and reduction gear efficiency of 70% or more, which are the design requirements for a remote weapons system, was designed utilizing a design and analysis program (HEXAGON) for gear engineering. To confirm the performance of the cycloid reducer, the hardness of the main components of the manufactured cycloid reducer, reduction ratio, and efficiency were measured.

• 한국정밀공학회지
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• 제30권11호
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• pp.1187-1192
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• 2013

In the case of 4 wheel drive (4-WD) type car, power switching occurs to 4-WD by operating lever or switch that operates power switching device attached in transfer case which can operate motor by electric signal. So if the RPM of motor is high, power switching will not exactly occur and can cause damage to gear in transfer case according to circumstances. So in this study, we applied 2 level of planet gear type motor spindle of motor drive part of a power train. And conducted decelerating to increase torque to switch power safe and accurately. Also, we researched efficiency of gear by designing reduction gear ratio and gear type and by calculating contact stress and bending strength. Based on researched content, we made drive head of power switching device and a reduction module which uses type that uses motor spindle as sun gear and ring gear as cover.

• Journal of Electrical Engineering and Technology
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• 제9권1호
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• pp.162-169
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• 2014

The analysis and comparation of the half-coiled short-pitch windings with different phase belt are presented in the paper. The half-coiled short-pitch windings can supply the odd and even harmonics simultaneously, which can be applied in multiphase bearingless motor (MBLM). The space harmonic distribution of the half-coiled short-pitch windings with two kinds of phase belt is studied wi th respect to different coil pitch, and the suitable coil pitch can be selected from the analysis results to reduce the additional radial force and torque pulse. The two kinds of half-coiled short-pitch windings are applied to the five- and six-phase bearingless motor, and the comparation from the Finite Element Method (FEM) results shows that the winding with $2{\pi}/m$ phase belt is fit for the five phase bearingless motor and the winding with ${\pi}/m$ phase belt is suitable for the six phase bearingless motor. Finally, a five phase surface-mounted permanent magnet (PM) bearingless motor is built and the experimental results are presented to verify the validity and feasibility of the analysis. The results presented in this paper will give useful guidelines for design optimization of the MBLM.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.373-378
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• 2013

Impact wrench has a sophisticated structure to implement various pre-designed mechanisms with specific functions. In the structure of impact wrench, the gear box has an important role to generate impacting force of anvil from actuating torque. Since, it requires to design systematically the gear box for accurate mechanism of operation and transferring motions. In this paper, a methodology of dynamic analysis, which is useful to design mechanical system, is proposed and applied to impact wrench, sequentially. At first, the way to perform dynamic analysis for design, which is progressed from component to assembled system, is introduced. Secondly, the proposed methodology is applied to designing impact wrench. Eventually, the results of parameter study with proposed methodology are applied to actual design for design optimization. And optimized-design is evaluated in the view of accurate operation and structural stability.

• 한국군사과학기술학회지
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• 제22권3호
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• pp.392-400
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• 2019

This paper provides a fin actuation system of missile based on electromagnetic-spring mechanism to miniaturize the system and lower the cost. Compared with proportional electro-mechanical actuators, the output of Electromagnetic-Spring Actuators(EMSA) has two or three discrete states, but the mechanical configuration of EMSA is simple since it does not need power trains like gears. The simple mechanism of EMSA makes it easy to build small size, low cost, and relatively high torque actuators. However, fast response time is required to improve the dynamic performance and accuracy of missiles since bang-off-bang operation of EMSA affects the flight performance of missile. In this paper the development of EMSA including parameter optimization and mathematical modeling is described. The simulation results using Simulink and experimental test results of prototype EMSAs are presented.

• Structural Engineering and Mechanics
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• 제78권5호
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• pp.519-528
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• 2021

One of the most efficient designs of solar trackers for photovoltaic panels is the single-axis tracker, which holds the panels along a torque tube that is driven by a motor at the central section. These trackers have evolved to become extremely slender structures due to mechanical optimization against static load and the need of cost reduction in a very competitive market. Owing to the corresponding decrease in mechanical resistance, some of these trackers have suffered aeroelastic instability even at moderate wind speeds, leading to catastrophic failures. In the present work, an analytical and experimental approach has been developed to study that phenomenon. The analytical study has led to identify the dimensionless parameters that govern the motion of the panel-tracker structure. Also, systematic wind tunnel experiments have been carried out on a 3D aeroelastic scale model. The tests have been successful in reproducing the aeroelastic phenomena arising in real-scale cases and have allowed the identification and a close characterization of the phenomenon. The main results have been the determination of the critical velocity for torsional galloping as a function of tilt angle and a calculation methodology for the optimal sizing of solar tracker shafts.