• Composites Research
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• v.33 no.3
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• pp.133-139
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• 2020

In this research, the vibration characteristics of composite quadcopter are analyzed, and avoidance design and analysis are performed to avoid resonance. The full platform of a commercial quadcopter with composite rotor arm is analyzed to see the vibration characteristics using FEM program. The manufactured stacking sequences of rotor arm is used for analysis, and the natural frequencies are compared with experimental results and simple analytic model results. It is also confirmed that the natural frequency of the particular mode is included within the operation range of the motor. The resonance avoidance design is carried out by selecting three variables from the existing model: stacking sequence, rotor-arm pipe length, and pipe thickness.

• Proceedings of the KIEE Conference
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• 1998.07g
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• pp.2381-2383
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• 1998

직류직권모터는 전동지게차와 같은 물류용 전동차에서 사용되는데, 우수한 기동 토오크를 가지는 반면에 파라미터의 열적, 변화가 심하고 마찰과 부하의 비선형성이 존재해 기존의 제어기로는 만족할 만한 성능을 내지 못한다. 본 논문에서는 이를 해결하기 위해 퍼지제어기를 사용한다. 퍼지제어기는 변수의 애매성에 바탕을 두고 제어하기 때문에 이러한 비선형성에 대해 강인하나, 소속함수의 결정과 퍼지규칙의 선정이 어려우며, 체계적인 방법이 존재하지 않는다. 이러한 퍼지제 어의 결점을 해결하기 위해 소속함수는 유전 알고리즘을 통해 자기동조 시키며 퍼지규칙은 오차와 오차변화율의 위상평면을 이용하여 결정한다. 실용성을 검증하기 위해 TI사의 DSP TMS320F240을 이용해 실시스템에 적용했으며, 이를 통해 부하의 변동 및 기준 속도의 변화에도 잘 대처함을 알 수가 있었다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.6
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• pp.635-642
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• 2014

In this paper, an efficient technique is developed to predict failure probability of three failure modes(case rupture, fracture and bolt breakage) related to solid rocket motor case due to the inner pressure during the mission flight. The overall procedure consists of the steps: 1) design parameters affecting the case failure are identified and their uncertainties are modelled by probability distribution, 2) combustion analysis in the interior of the case is carried out to obtain maximum expected operating pressure(MEOP), 3) stress and other structural performances are evaluated by finite element analysis(FEA), and 4) failure probabilities are calculated for the above mentioned failure modes. Axi-symmetric assumption for FEA is employed for simplification while contact between bolted joint is accounted for. Efficient procedure is developed to evaluate failure probability which consists of finding first an Most Probable Failure Point(MPP) using First-Order Reliability Method(FORM), next making a response surface model around the MPP using Latin Hypercube Sampling(LHS), and finally calculating failure probability by employing Importance Sampling.

• Archives of design research
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• v.17 no.1
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• pp.383-392
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• 2004

The power tools is the product using working power generated by electric motor. Many companies are manufacturing numerous devices. Main features of tools are included various assembled products, small, light and solid and durable enough to match several standards. Fundamental requirements for the product is excellent performance and convenience for use. The quality of them depends on the equipped motor'(s) capability, accuracy of gear and endurance against worn-out. By adapting the state-of-the-art parts, they could be used in the place from home to heavy industry broadly. They can be classified electronic drills, grinders, saws and sanders families for the household appliances. For industrial tools, bore drill, grinder, polisher, and driver drill are classified as special and high priced group. This study presents the strategy of power tool development of BOSCH, BLACK&DECKER and KEYANG. Their products were analyzed in terms of product line and product mix concept. Then they are examined by design elements, such as color, shape and material for housing. As an analysis method, the image scale parameter and criteria were applied to each company's product.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.1
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• pp.151-159
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• 1998

Elelctrical properties of $BaTiO_3$ were characterized with addition of $Y_2O_3, CaO,SiO_2$ and Mn to develope the composition of PTC thermistor suitable as a current limiting device for automobile motor system. With the addition of 0.2 mol% $Y_{2}O_3$ to $BaTiO_3$, the minimum resistance of 16.5 ${\Omega}{\cdot}$cm was obtained at room temperature. $(Ba_{0.996}Y_{0.004})TiO_3$ exibited a minimum resistance of 50${\Omega}{\cdot}$cm with addition of 1.6 mol% $SiO_2$. The grain size of $(Ba_{0.996}Y_{0.004})TiO_3$ decreased from 34.95 ${\mu}$m to 13.4 ${\mu}$m and thus breakdown voltage could be improved by changing the composition as $(Ba_{0.996}Y_{0.004}Ca_{0.05}) TiO_3$ with substition of 5 mol% Ca into Basites. When 0.04 mol% Mn was added, the optimum PTCR properties could be obtained : the resistivity at room temperature and ${\rho}_{max}/{\rho}_{min}$ were 30~40${\Omega}{\cdot}$cm and $1.5{\times}10^5$ respectively.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1885-1889
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• 2006

제주지역은 대륙과 해양을 연결하는 요충지로서 한라산을 중심으로 동서사면은 $3{\sim}5^{\circ}$의 완만한 경사를 이루고 있다. 연평균 강우량은 1,975mm로서 국내 최다우 지역이나 제주도의 지질 특성상 도내 대부분의 지역이 투수성이 높은 다공질 현무암으로 구성되어 있는 관계로 지표수의 발달이 미약한 반면 지하수가 풍부하게 부존되어 있으며 기저지하수, 준 기저지하수, 상위지하수, 기반암지하수로 이루어져 있다. 최근 우리나라의 교토의정서 비준으로 인한 온실가스 감축이 불가피함에 따라 대체 재생가능한 에너지를 이용한 풍력발전시대가 도래하고 있으며, 제주 행원풍력발전단지에 설치된 총 15기 발전장치의 현실성과 경제성 입증을 통해 제주지역의 풍력에너지를 이용한 지하수 취수시스템을 제안하였다. 본 연구는 제주, 고산, 서귀포, 성산포지역에 대한 제주지방기상청 연평균 풍속자료$(2004{\sim}2005)$를 통하여 대상지역내 적용 가능한 로터(Roter), 나셀(Nacelle), 타워(Tower), 발전기를 포함한 발전장치를 선정하였으며, 공기역학적(Aerodynamic)특성에서 전기에너지로 변환한 풍력에너지를 지하수 취수시스템으로 적용하기까지의 전력공급절차를 도출하였다. 또한 생산되어진 풍력에너지 용량에 적용 가능한 수중.육상모터펌프를 산정하여 '제주도 지하수개발.이용시설 설치 및 관리기준(2004)'에서 제시한 구조도를 바탕으로 대상지역내 지하수위를 고려한 지하수 취수시스템을 도시하였다. 제주도는 지형 및 지질적인 특성상 수자원을 지하수에 의존할 수밖에 없는 특수한 지역이므로 2002년말 통계를 살펴보면 생활용, 공업용, 농업용으로 각각 57만$m^2$, 11만$m^2$, 56만$m^2$를 포함한 1일 최대 124만$m^2$의 지하수를 사용하고 있다. 따라서 풍력에너지를 이용한 지하수 취수시스템을 도입하여 재생가능한 에너지이용 효과와 세계인이 공감하는 청정한 관광자원으로 활용 가능할 것이라 판단된다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.5
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• pp.2381-2387
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• 2013

This paper deals with an optimal angle error reduction method of magnetic hall sensor using hall effect elements with yoke. The magnetic position sensor is required to generate ideal sine and cosine waveforms from its hall effect elements according to rotation angle for precise angle information. However, the output signals are easy to include harmonics due to uneven magnetic field distribution from disturbance in the vicinity of hall effect elements. Thus, The paper studies a way which makes sine and cosine waveforms robust in disturbance and reduces harmonics by installing a yoke around Hall effect elements. The angle detection simulation for the magnetic hall sensor is performed by 3 dimensional finite element method and Taguchi method, one of the design of experiments. For the Taguchi method, three design parameters related to position of hall effect elements and shape of hall effect element yoke are selected.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.11
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• pp.1327-1334
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• 2012

This study shows the conformance-based design results of a fourth-order dynamic actuator showing a performance variation caused by variation in the components as well as aero-induced disturbances. The actuator comprises a BLDC motor, spur gear and worm gear assembly, and canard. The actuator performance was evaluated by using time-variant angle information of the canard. Based on the response surface models, critical system variables were screened using F-tests, and then, the performance was approximated as a function of the variables because it is difficult to determine the performance of a high-order dynamic system as a function of system variables through analytical approaches. In this study, the conformance of uncertain performance to the specification was defined as a probability measure. The design variables obtained by optimizing the measure can provide actuator performance conforming to the specifications considered, even though there is a variation in both the components and the aero-induced disturbances.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.3
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• pp.243-253
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• 2014

This paper deals with the Quantitative Feedback Thoery(QFT) guaranteeing robustness in spite of the plant parametric uncertainty. In the frequency domain, the QFT guarantees the robustness of the design specification on the uncertainty of plant parameters and disturbance. In order to use the QFT, a selected plant is a Quad Rotor Vehicle(QRV) which has excellent maneuverability and possibility of vertical take-off and landing like the helicopter. And attitude control is examined the possibility satisfied the requirement specification under the setting parametric uncertainty of motors driving 4-blades. Additionally, in an attitude control, the pre-filter considering parameter range and operating range of a QRV was used. For these purpose, in this paper, by using QFTCT, that is the QFT Control Toolbox designing the controller in MATLAB by the QFT, each design phases are introduced.

• Clean Technology
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• v.20 no.3
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• pp.283-289
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• 2014

General household vacuum cleaners consist of dust collector, pre filter, motor and exhaust filter, and the filtered clean air is discharged to the atmosphere. By using the CFD methods, we estimated the internal flow in two types of commercial cyclone vacuum cleaners to evaluate the dust collection performance. From the analysis, it was known that the number of revolution had higher values in cyclone cone region. CFD analysis in a specific showed non-uniform velocity distribution at outlet, which results in the deterioration of particle collection performance. In order to improve flow condition, the installation of baffle was proposed and the values of velocity RMS were estimated.