• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 A
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• pp.59-61
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• 1995

This paper presents the cogging torque analysis of the permanent magnet type AC servo motor which have the closed slot structure. Generally, existence of the slot opening causes the cogging torque. But the cogging torque exists in this type motor(having closed slot structure) because the bridge part is saturated by the rotor flux. In this paper, the finite element analysis is used to calculate the cogging torque and the rated torque. As the size of the bridge part-the thickness and the width-changes, the cogging torque and the rated torque are obtained repeatedly like as upper procedures. Finally, the trends of the cogging torque and the rated torque versus the size of the bridge part are obtained from this analysis procedures. By this approach, the optimal geometry of the bridge part can be found which minimize the cogging torque satisfying the required value of the rated torque.

• 대한기계학회논문집B
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• 제40권6호
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• pp.397-402
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• 2016

원자력 발전소와 화력 발전소에서는 양질의 전기를 생산하기 위해서는 발전기에 연결된 고압 및 저압 증기터빈에 최적량의 증기를 공급하여야 한다. 터빈에 증기를 공급하거나 차단하는 특수한 밸브인 터빈출력제어장치를 사용하고 있으며, 이 터빈출력제어장치는 유압서보 액추에이터로 구동 된다. 발전소에서는 유압시스템에서 생성되는 기체로 인하여 유압서보 액추에이터의 성능이 저하되거나, 생성된 기체가 압축되면서 발생하는 열로서 씰을 태우고 마모를 증가시켜서 빈번한 고장이 유발된다. 일부 발전소에서는 고정형 오리피스를 사용하여 공기를 배출하고 있지만 많은 유량배출에 따른 동력 손실과 빈번하게 작동되는 펌프, 전기모터 및 밸브 등의 고장을 발생시킨다. 본 연구에서는 기존의 고정형 오리피스와 같이 초기에 많은 량의 공기를 배출하고 정상운전에서는 매우 미세한 유량만 통과 시킬 수 있는 부하 감응형 공기 배출밸브를 모델링하고 해석하여 장착함으로서 유압서보 액추에이터의 제어 정밀성 확보와 기체 압축으로 인한 고장을 방지할 수 있게 하였다.

• Agricultural and Biosystems Engineering
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• 제7권1호
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• pp.1-7
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• 2006

A need exists to monitor and control the localized high temperatures often experienced in solar grain dryers, which result in grain cracking, reduced germination and loss of cooking quality. A verified finite element model would be a useful to monitor and control the drying process. This study examined the feasibility of the finite element method (FEM) to predict temperature distribution in solar grain dryers. To achieve this, an indirect solar grain dryer system was developed. It consisted of a solar collector, plenum and drying chambers, and an electric fan. The system was used to acquire the necessary input and output data for the finite element model. The input data comprised ambient and plenum chamber temperatures, prevailing wind velocities, thermal conductivities of air, grain and dryer wall, and node locations in the xy-plane. The outputs were temperature at the different nodes, and these were compared with measured values. The ${\pm}5%$ residual error interval employed in the analysis yielded an overall prediction performance level of 83.3% for temperature distribution in the dryer. Satisfactory prediction levels were also attained for the lateral (61.5-96.2%) and vertical (73.1-92.3%) directions of grain drying. These results demonstrate that it is feasible to use a two-dimensional (2-D) finite element model to predict temperature distribution in a grain solar dryer. Consequently, the method offers considerable advantage over experimental approaches as it reduces time requirements and the need for expensive measuring equipment, and it also yields relatively accurate results.

• Journal of Biosystems Engineering
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• 제25권3호
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• pp.213-220
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• 2000

Grafting of fruit-bearing vegetables has been widely used to increase the resistance to soil-borne diseases, to increase the tolerance to low temperature or to soil salinity, to increase the plant vigor, and to extend the duration of economic harvest time. After grafting, it is important to control the environment around grafted seedlings for the robust joining of a scion and rootstock. Usually the shading materials and plastic films are used to keep the high relative humidity and low light intensity in greenhouse or tunnel. It is quite difficult to optimally control the environment for healing and acclimation of grafted seedlings under natural light. So the farmers or growers rely on their experience for the production of grafted seedling with high quality. If artificial light is used as a lighting source for graft-taking of grafted seedlings, the light intensity and photoperiod can be easily controlled. The purpose of this study was to develop a prototype system for the graft-taking enhancement of grafted seedlings using artificial lighting and to investigate the effect of air current speed on the distribution of air temperature and relative humidity in a graft-taking enhancement system. A prototype graft-taking system was consisted by polyurethane panels, air-conditioning unit, system controller and lighting unit. Three band fluorescent lamps (FL20SEX-D/18, Kumho Electric, Inc.) were used as a lighting source. Anemometer (Climomaster 6521, KANOMAX), T-type thermocouples and humidity sensors (CHS-UPS, TDK) were used to measure the air current speed, air temperature and relative humidity in a graft-taking system. In this system, air flow acted as a driving force for the diffusion of heat and water vapor. Air current speed, air temperature and relative humidity controlled by a programmable logic controller (UP750, Yokogawa Electric Co) and an inverter (MOSCON-G3, SAMSUNG) had an even distribution. Distribution of air temperature and relative humidity in a graft-taking enhancement system was fairly affected by air current speed. Air current speed higher than 0.1m/s was required to obtain the even distribution of environmental factors in this system. At low air current speed of 0.1m/s, the evapotranspiration rate of grafted seedlings would be suppressed and thus graft-taking would be enhanced. This system could be used to investigate the effects of air temperature, relative humidity, air current speed and light intensity on the evaportranspiration rate of grafted seedlings.

• 한국방재안전학회논문집
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• 제10권1호
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• pp.85-90
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• 2017

본 연구는 빌딩과 공공시설에 설치되는 중요 전기 시설물인 수배전반이, 규모 8.3급 지진에도 국내최초로 정상적으로 작동될 수 있도록, 전기를 사용하는 각종 시설물 및 기계장치의 전원공급 및 제어하는 수배전반 하부에 상하굴절형 내진패드를 설치하여, 수배전반 하부구조 보호와 상부에 케이블 단락방지 등이 가능하도록 하여, 상하좌우 모든 지진파에 잘 적응되는 내진형 수배전반 제조기술로 한국전력이 기준으로 제시한 GR-63-CORE(규모 8.3 급) 내진성능을 만족하는, 내진형 수배전반 방재기술이다. 연구 성과로서, 전기 및 통신 기반시설을 보호할 수 있게 되어 지진발생시 전기시설을 정상상태로 복구하는 시간을 단축하는데 기여할 수 있고, 지진발생시 전기공급 시설의 파괴로 인한 화재발생을 방지할 수 있어 일본의 경우처럼 대규모 지진 발생시 발생하는 화재의 확산을 최소화하여 인명피해와 재산피해를 최소화할 수 있으며, 시민들이 대규모 지진을 겪은 후에도 일상생활로 신속히 복구할 수 있는 전기기반시설을 확보 등에 기여할 수 있다. 또한, 통신 및 전산실의 장비의 내진을 확보하기 위하여, 본 기술이 적용될 수 있고, 나아가 지진시 기반이 흔들려 시설기능이 정지될 수 있는 분야에도 다양하게 적용될 수 있을 것이다.

• Journal of Biosystems Engineering
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• 제22권4호
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• pp.469-478
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• 1997

This study was conducted to develop an automatic nutrient-solution mixing system for small-scale sewers. The nutrient-solution mixing system consisted of a low-cost and precise metering device and data acquisition ＆ control system with a personal computer. and, the metering device was composed of three parts those were supply pumps, metering cylinders and venturi tube. The system controlled electric conductivity(EC) and pH of nutrient-solution based on the time-based feedback control method with the information about temperature, EC, and pH of the nutrient-solution. The performance of the nutrient-solution mixing system was evaluated through the control of EC and pH while compared with those of commercial system. Also an experimental cultivation of tomato was conducted to verify and to improve the developed system. Results of this study were as follows. 1. The correlation coefficient of meteing device between the flow rate and operating time was 0.9999, and the linear reuession equation computed was y=21.759x, where y is the discharge($g$) and x is the operating time(s). 2. Calculated errors for the developed metering device and two commercial pump were $\pm$0.3% $\pm$2.45% and $\pm$1.38 % FS error respectively. 3. An automatic nutrient-solution mixing system based on a low-cost and precise metering device was developed. 4. The full scale errors of the developed system in controlling EC and pH at 23$\pm$1$^{\circ}C$ were $\pm$0.05mS/cm and $\pm$0.2, respectively 5. When using the commercial system, the controlled values of EC and pH of the 500 $\ell$ of water were 1.29 mS/cm and 6.1 pH for the setting points of 1.4 mS/cm and 6.0 pH respectively at 23$pm1^{\circ}C$. 6. The developed nutrient-solution control system showed $\pm$0.05 ms/cm of deviation from the setting EC value over the experimental cultivation period. 7. The deviation from the average values of Ca and Mg mass content in the several nutrient-solution were 0.5% and 1.8% respectively.

• Tribology and Lubricants
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• 제15권3호
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• pp.278-286
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• 1999

To predict the behavior of the intravascular micro active endoscope in the real human vascular system, a human mock circulation system was developed. The intravascular micro active endoscope which consists of micro active bending catheter and micro drug infusion catheter was driven in the velocity, Re number and temperature controlled flow. The three SMA (Shape Memory Alloy) zigzag type spring in the micro active bending catheter was heated by the electric current generated by PWM controller, and the shape memory effect made the actuator bend to any direction. The micro drug infusion catheter was driven through the inner hole of the micro active bending catheter. A mock circulation system is shaped from Ascending Arota to Femoral artery according to a human data (the data contains many vascular sizes and hydrographs of many control points). We developed a vascular model with glass and silicone tubes, and set the flow system with circulation parts, flow settling parts, and lots of valves. The heater and heat-controller was added to the How system to centre! the temperature of the How at 36.5$^{\circ}C$. The result showed that the developed intravascular micro active endoscope could be induced to any point in the vascular model.

• Journal of Biosystems Engineering
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• 제32권6호
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• pp.455-461
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• 2007

The electric current of a flow injection type enzyme-sensor was measured to confirm the stable operating conditions of the sensor. The current of the sensor was decreased as the buffer solution velocity increased. Under the limitation of the cycle time to be below 10 minutes, the effective ranges of the buffer solution velocity were suggested $0.10{\sim}0.26$, $0.12{\sim}0.24$, $0.1{\sim}0.25$ and $0.05{\sim}0.10\;cm/s$ of 1.0, 1.4, 2.4 and 3.4 mm of the electrode diameters, respectively. As the reaction time of the enzyme and the substrate was increased, the current was decreased because of the dilution between the sample and buffer solution. Therefore, it could be recommended that the reaction time was able to be selected as shortly as possible in consideration of the total cycle time. As the result of the experiments using a different volume ratio of the enzyme to substrate, it was concluded that the substrate had to be mixed with the same amount of the enzyme. The current have increased remarkably in proportion to the electrode diameter under 0.1 cm/s of the buffer solution velocity but there was no difference over 0.1 cm/s of the buffer solution velocity. The cross type arrangement of the electrode was highly suggested for application and machining of the sensor.

• Journal of Biosystems Engineering
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• 제27권6호
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• pp.565-572
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• 2002

In order to control the root-zone temperature of greenhouse crops in the hydroponics at hot and cold season, heat pump system for cooling and heating was built and tested in this work. The system was air-to-water type and vapour compression type. The heating and cooling mode was selected by the four way valve. Capacity of the compressor was 3.75㎾ and heat transfer area of the evaporator and the condenser were 3.05㎡ and 0.6㎡, respectively. According to the performance test, it could supply heat of 42,360 to 64,372kJ/h depending on the water circulation rate of 600 to 1,500ℓ/h, respectively, when indoor air temperature was 10∼20$\^{C}$. COP of heat pump system was 3.0 to 4.0 in the heating mode. But, COP of the cooling mode was 1.3 to 2.1 at indoor temperature of 20∼35$\^{C}$. The feasibility test in the greenhouse the developed heating and cooling system was installed, showed that the heating cost of the developed system was only about 13% of that of the conventional heating system. The heating cost of the developed system was 367won/day(electric consumption 9.7㎾h/day), while that of the conventional system was 2,803won/day(oil consumption 7.7ℓ/day) at the same heating mode.

• 생물환경조절학회지
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• 제27권2호
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• pp.166-172
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• 2018

본 연구에서는 우선, 농작물의 생육 및 환경관련 데이터를 활용하여 온실의 최적 환경 구현을 위한 시스템을 선정하고 생산성 향상에 대한 연구에 앞서 현재 국내에 보급되어 있는 스마트 온실의 실태를 파악하기 위하여 7가지의 유형별 스마트 온실 농가를 대상으로 현장조사를 실시하였다. 그 결과 현장에서 전하는 유형별 스마트 팜 선도 사례의 주목적을 보면, 지능형이나 첨단형 정도가 스마트 팜에 가까운 것으로 판단되었다. 연령대를 보면, 상대적으로 40대 및 60대가 가장 많았지만, 50대 이하가 21개 농가로서 전체의 약 70.0%정도를 차지하였고, 재배경력은 10년 이하가 가장 많았다. 온실의 형태로는 1-2W형이 전체의 50.0%정도이고, 연동형이 전체의 80.0%정도로서 24개 농가였다. 재배작물의 경우, 화훼류는 3개 농가뿐이고, 나머지 농가는 채소류 중에서도 과채류만 재배하는 것으로 나타났다. 과채류 중에서도 상대적으로 토마토와 파프리카가 전체 중에 약 63.6%를 차지하였다. 제어시스템은 약 77.4%정도인 24개 농가가 국산제품을 사용하고 있었다. 제어시스템의 제어방식의 경우, 3개 농가는 제어패널만을 사용하여 온습도 등을 조절하였고 나머지 농가는 패널과 컴퓨터에 의한 디지털 제어방식이었다. 디지털 제어의 경우, 휴대폰을 통한 애플리케이션으로 원격조절도 가능하게 설계되어 있고, 대부분 농가에 CCTV도 설치되어 있었다. 계측 및 조절 대상 환경인자는 온도를 포함하여 9개 정도이며, 온도는 전체 조사대상 농가가 계측하고 있었지만, 환기 및 공기유동 팬이나 탄산가스 농도 등의 경우는 다른 인자에 비해 상대적으로 낮았다. 난방시스템의 경우, 대상 농가 중에 46.7%가 전기보일러를 사용하는 것으로 조사되었다. 이 외에도 온수보일러, 히트펌프 및 등유보일러 등으로 나타났다. 제어시스템에 투자한 규모의 경우, 1,000만 원에서 1억원까지로 투자규모가 농가마다 다르게 나타났다.