• 전기전자학회논문지
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• 제24권4호
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• pp.954-960
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• 2020

본 논문은 단상 영구자석 동기전동기의 속도 가변형 비례공진 전류제어 기법을 제안한다. 단상 영구자석 동기전동기는 전자기적 특성상 고정자 전류와 역기전력의 위상차에 따른 부토크 및 영토크가 발생하며 센서리스 운전 시 낮은 고정자 저항과 인덕턴스로 인해 과전류 제한이 필요하다. 이러한 조건하에서 전류제어를 위해 3상 교류 전동기에 사용되는 벡터 제어를 이용할 경우, 좌표변환, 역좌표변환 및 가상의 dq축 성분을 생성하는 과정이 필요하다. 하지만, 단상 영구자석 동기전동기의 자기적 특성을 고려하여 제안한 속도 가변형 비례공진 전류제어 기법은 3상 교류 전동기에 사용되는 좌표변환 과정이 필요하지 않다. 본 논문에서는 가변 비례공진 전류제어 기법을 이용하여 안정적인 기동 성능을 확인하며 일정 속도 도달 시 위치 센서 없이 단상 영구자석 동기전동기의 수학적 모델 기반 센서리스 제어로 제안한 전류제어 기법의 효용성을 다수의 실험을 통해 검증하였다.

• 한국해양공학회지
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• 제35권4호
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• pp.266-272
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• 2021

Mooring systems are among the most important elements employed to control the motion of floating offshore structures on the sea. Considering the use of polymer material, a new method is proposed to address the creep characteristics rather than the method of using a tension load cell for measuring the tension of the mooring line. This study uses a synthetic mooring rope made from a polymer material, which usually consists of three parts: center, eye, and splice, and which makes a joint for two successive ropes. We integrate the optical sensor into the synthetic mooring ropes to measure the rope tension. The different structure of the mooring line in the longitudinal direction can be used to measure the loads with the entire mooring configuration in series, which can be defined as SMART (Smart Mooring and Riser Truncation) mooring. To determine the characteristics of the basic SMART mooring, a SMART mooring with a diameter of 3 mm made of three different polymer materials is observed to change the wavelength that responds as the length changes. By performing the longitudinal tension experiment using three different SMART moorings, it was confirmed that there were linear wavelength changes in the response characteristics of the 3-mm-diameter SMART moorings. A 54-mm-diameter SMART mooring is produced to measure the response of longitudinal tension on the center, eye, and splice of the mooring, and a longitudinal tension of 100 t in step-by-step applied for the Maintained Test and Fatigue Cycle Test is conducted. By performing a longitudinal tension experiment, wavelength changes were detected in the center, eye, and splice position of the SMART moorings. The results obtained from each part of the installed sensors indicated a different strain measurement depending on the position of the SMART moorings. The variation of the strain measurement with the position was more than twice the result of the difference measurement, while the applied external load increased step-by-step. It appears that there is a correlation with an externally generated longitudinal tensional force depending on the cross-sectional area of each part of the SMART mooring.

• 한국정보통신학회논문지
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• 제25권12호
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• pp.1874-1881
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• 2021

폭설로 인한 도로 미끄러짐과 함께 영하의 기온으로 도로와 차량 통행용 다리, 터널 출입구 쪽에서 주로 발생하는 블랙아이스는 운전자의 시야에서는 아스팔트의 이미지가 투과되어 보이기에 잘 인식되지 않아서 자동차들이 미끄러지는 (슬립 현상) 상황을 발생시키기에 차량이 제동력을 잃어서, 대형 교통사고로 이어져 심각한 인명과 재산상 손실을 초래하고 있다. 본 논문에서는 기존에 연구되었던 블랙아이스 감지 방법들(인공위성 촬영, 초음파 수신으로 미끄러짐의 패턴을 확인, 도로 표면의 온도측정, 차량 주행 중 타이어의 마찰력 차이를 확인하기)의 단점들을 보완하고, 블랙아이스를 감지하는 센서의 크기를 줄여서 많은 이동체에 적용할 수 있도록 하고자 적외선 카메라를 이용하여 도로 상태를 확인하고, 이 정보를 딥러닝 학습을 통하여 블랙아이스를 판별하는 방법을 제안하고자 한다.

• 문화기술의 융합
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• 제8권6호
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• pp.435-439
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• 2022

2022년 2월 24일, 우크라이나-러시아 전쟁이 발발했다. 이 전쟁에서 특이한 현상들이 발생하고 있는데, 그중에 하나가 2차 세계대전 이후 장군들의 전사율이 가장 높다는 것이다. 이것은 우크라이나군이 러시아군의 장군들만을 제거하는 핀셋작전을 전개하고 있기 때문이다. 이를 위해, 우크라이나군은 군사정보팀이라는 특수작전 부대를 운용하고 있는데, 이들은 자체, 미군·나토군, 민간 등의 자산을 융복합하여 다영역에서 활용함으로써 시너지를 창출하고 있다. 특히, 이들은 스타링크를 활용하여 '감시-결심-타격' 활동을 실시간 초연결함으로써 생존성과 작전효용성을 극대화하고 있다. 한국군 또한 다양한 특수작전부대를 보유하고 있고, 한반도에는 대량살상무기 위협이 내재되어 있다. 따라서 우크라이나군에서 운용하는 군사정보팀의 조직편성, 무기체계 및 운용 방법은 한국군이 미래 위협을 상쇄하는데 방향성을 제공할 수 있다.

• Design & Manufacturing
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• 제17권1호
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• pp.56-63
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• 2023

In this study, the vibration signal of the mold was measured and analyzed to monitor the process information and characteristics during the press molding process. A necklace-type picture frame mold was used for press molding, and the vibration signal was measured by GY-61 acceleration sensor module attached to the surface of the upper (movable) mold base. The change of the vibration signal of the mold according to press speed was analyzed. As a result, the vibration signal had a large change at five sections: "Holder contact", "Punch contact and start of pressing", "End of pressing", "Mold open", and "Demolding". The time difference between "Punch contact and start of pressing" and "End of pressing" means the pressing time which is the actual time the material is molded under pressing pressure. The time intervals for each section, represented by the time interval between "Holder contact" and "Punch contact and start of pressing", can be used to compare and evaluate the press speed applied to the process. By comparing the vibration signals at 60 rpm and 90 rpm, the amplitude at the section of "Punch contact and start of pressing" increased as the press speed increased. This result means that as the press speed increases, more force and pressure is applied to the material. Also, the peak values of the other sections were found to increase as the press speed increased. It was found that the pressing time, the time interval between "Punch contact and start of pressing" and "End of pressing", decreases as the pressing speed increases. Similarly, press speed factor, the time interval between "Holder contact", and "Punch contact and start of pressing", is found to be shorter. Therefore, based on the result of this study, the pressing time, press speed, pressing(punching) pressure of each cycle can be monitored by measuring the vibration signal of the mold. Also, it was confirmed that the level and trend of process information and characterization can be evaluated as the change of the mold vibration during press molding.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2021년도 추계학술대회
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• pp.667-669
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• 2021

최근 RFID/USN 기술은 물류, 환경, 교육, 홈 네트워크, 방재, 군사, 의료 등 다양한 분야에서 적용되고 있으나 RFID/USN 기술의 눈부실 발달에도 불구하고 열악한 해양 환경의 특성상 해양 산업현장에 적용하기에는 많은 애로사항이 있다. 따라서 해양분야에서는 주로 위성을 사용하고 있으며 연안에서는 기존 통신망을 사용하고 있어 원양에서의 선반 단독 근거리 네트워크 형성을 위한 방안이 고려되고 있다. 본 논문에서는 기존 PS-LTE 및 LTE 네트워크에서의 USN을 활용하여 기지국 역할 위한 방안으로 드론을 USN의 이동 기지국으로 활용하는 방안을 고려하고 있다. 자율운항선박은 시스템의 지능화를 지향하므로 선원의 수와 노동력을 절감하고 보다 안정적이고 지능화된 ICT융합 기술형태의 자율적 네트워크 형성 기능이 강화되어야 한다.

• 농업과학연구
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• 제51권1호
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• pp.63-77
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• 2024

Yield monitoring systems have become integral to precision agriculture, providing insights into the spatial variability of crop yield and playing an important role in modern harvesting technology. This paper aims to review current research trends in yield monitoring systems, specifically designed for non-grain crops, including cabbages, radishes, potatoes, and tomatoes. A systematic literature survey was conducted to evaluate the performance of various monitoring methods for non-grain crop yields. This study also assesses both mass- and volume-based yield monitoring systems to provide precise evaluations of agricultural productivity. Integrating load cell technology enables precise mass flow rate measurements and cumulative weighing, offering an accurate representation of crop yields, and the incorporation of image-based analysis enhances the overall system accuracy by facilitating volumetric flow rate calculations and refined volume estimations. Mass flow methods, including weighing, force impact, and radiometric approaches, have demonstrated impressive results, with some measurement error levels below 5%. Volume flow methods, including paddle wheel and optical methodologies, yielded error levels below 3%. Signal processing and correction measures also play a crucial role in achieving accurate yield estimations. Moreover, the selection of sensing approach, sensor layout, and mounting significantly influence the performance of monitoring systems for specific crops.

• 한국구조물진단유지관리공학회 논문집
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• 제27권3호
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• pp.21-29
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• 2023

본 연구에서는 FCM 공법에서 교각과 캔틸레버 세그먼트의 임시고정을 위하여 주로 적용하고 있는 "내부 프리스트레싱 긴장재에 의한 임시 고정시스템(Stiching System)"에서 강봉의 응력특성을 분석하였다. 본 시스템에서 강봉은 교각과 PSC BOX를 내부에서 연결하여 인장 및 장착하므로 초기 긴장력의 변화 추이를 확인하기 어려웠다. 따라서, 강봉에 부착하여 강봉의 미세 길이변화를 측정할 수 있는 FBG센서를 활용하여 각 세그먼트 완료 전후에 계측 및 분석을 수행하였다. 분석 결과 캔틸레버 세그먼트 완료까지 발생한 강봉의 최대 연직 수축량의 75% ~ 90%가 강봉의 정착 ~ 1세그먼트에서 발생되었고, 이때 도입 긴장력의 최대 손실은 39%로 나타났다. 이와 같은 강봉의 정착 ~ 1세그먼트 완료까지의 긴장력의 과대 손실은 강봉 정착 중 시공의 정밀도 향상과 1세그먼트의 완료 이후 캔틸레버 세그먼트의 전도에 대한 안정성 확보를 위하여 재 긴장이 필요함을 의미한다. 2 ~ 마지막 세그먼트에서는 강봉의 응력이 완만하게 감소하였고 하절기에는 주두부 콘크리트의 연직방향 체적 증가에 상응한 강봉의 길이 증가로 인하여 응력의 감소가 일부 회복되는 경향을 보여 2~마지막 세그먼트에서는 대기 온도에 따른 강봉의 길이변화가 응력변화의 지배적인 요인인 것으로 판단된다. 강봉의 길이변화와 달리 강봉의 릴랙세이션에 의한 응력이완은 1.2 ~ 2.7%로서 매우 작은 비율로 나타났고, 강봉의 온도응력에 상응하는 반대방향 응력(강봉의 상하부 고정, 강봉과 콘크리트의 열팽창계수가 상이한 영향으로 발생)으로 대부분 상쇄되었다. 따라서, 강봉 정착 시기 조절 등 강봉의 내부응력 향상을 위한 방안을 제시하였다.

• 한국운동역학회지
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• 제14권3호
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• pp.99-118
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• 2004

The aim of this study is to evaluate tennis shoes's plantar pressure distribution in tennis prayers and to determine the influence of the shoe on various tennis movements. When investigating the biomechanics of movement in tennis, one of the first things to do is to understand the movement patterns of the sport, specifically how these patterns relate to different tennis shoes. Once these patterns are understood, footwear company can design tennis shoes that match the individual needs of tennis players. Plantar pressure measurement is widely employed to study foot function, the mechanical pathogenesis for foot disease and as a diagnostic and outcome measurement tool for many performance. Measurements were taken of plantar pressure distribution across the foot and using F-Scan(Tekscan Inc.) systems respectively. The F-Scan system for dynamic in-shoe foot pressure measurements has enabled us to assess quantitatively the efficacy of different types of footwear in reducing foot pressures. The Tekscan F-Scan system consists of a flexible, 0.18mm thick sole-shape having 1260 pressure sensors, the sensor insole was trimmed to fit the subjects' right, left shoes. For this study 4 university male, high level tennis players were instructed to hit alternated forehand stroke, backhand stroke, forehand volley, backhand volley, smash, service movement in 4 different tennis shoes. 1. When impact in tennis movement, peak pressure distribution of landing foot displayed D>C>B>A, A displayed the best low pressure distribution. A style's tennis shoes will suggest prayer with high impact. If prayer with high impact feeling during pray in tennis wear A style, it will decrease injury, will have performance improvement. 2. When impact in tennis movement, plantar pattern of pressure distribution in landing foot displayed B>A>C>D in stability performance. During tennis, prayer want to stability movement suggest B style tennis shoes when tennis movement impact keep stability of human body. B style tennis shoes give performance improvement 3. When impact in tennis movement, plantar pattern of center of force(C.O.F.)trajectory in landing foot analyzed this : 1) When stroke movement and volley movement in tennis, prayer better to rearfoot movement. 2) when service movement, prayer midfoot strike movement. 3) when smash movement, prayer have forefoot strike movement.

• 한국농공학회지
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• 제31권2호
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• pp.104-115
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• 1989

In an effort to clarify the wetted patterns of sandy loam soil under trickle irrigation conditions, the distance of wetted zone, infiltration capacity and soil wetted patterns, etc. were measured by gypsum block as soil moisture sensor located every 5 cm vertically and horizontaly in the soil bin under the such conditions as a). irrigation rates set to 2, 4, 6, 8 liters per hour b). total amount of water applied fixed to 14.62 liters per soil bin c) the hearing force of soil measured by plate penetrometer ranging from 1.04 to 1.22kg/cm$_2$ The results can be summarized as follows ; 1. The wetted distance in horizontal direction(H), the wetted distance in vertical direction(D), the horizontal infiltration capacity (iH) and the vertical infiltration capacity(in)could by explained as a function of time t. 2. The horizontal wetted distance (H) is explained by an exponetial function H= a$.$ t where b was found ranging from 021 to 026 under surface trickle irrigation, which was considered a lotlower than the classical value of 0.5 and these measurements were indifferent to the increasing irrigation rates. 3. As for the surface trickle irrigation where horizontal infiltration capacity(iH) is explained as iH = A $.$ t h, the coefficient A increases with respect to irrigation rates within the limits of 0.89~1.34. 4. In terms of surface trickle irrigation of the ratio of Dm Which is maximum vertical wetted distance to Hm, which is maximum horizontal wetted distance, found to be within range of 1.0 to 1.21. It was also noted that the value of Dm decreses when irrigation rates increases while the value of Hm changes the opposite direction. 5. The optimum location of sensors from emitter for surface trickle irrigation should he inside of hemisphere whose lateral radius is 28~30cm long and vertical radius is 10~12cm long. The distance between emitters should be within 60cm long. 6. In the study of vertical wetted distance( D) where D= a $.$ tb, the exponential coefficient b ranged from 0.61 to 0.75 in surface trickle irrigation, and from 0A9 to 0.68 for subsurface trickle irrigation. These measurements showed an increasing tendency to with respect to irrigation rates. 7. In case of vertical infiltration capacity( in), where iD= A $.$ t 1-h, the coefficient A for surface trickle irrigation found to be within range of 0.16 to 0.19 and did not show any relationships with varying degree of irrigation rates. However, the coefficient was varying from 0.09 to 0.22 and showed a tendency to increase vis-a-vis irrigation rates for subsurface trickle irrigation, in contrast. 8. In the observation of subsurface trickle irrigation, it was found that Dm/Hm ratio was within 1.52 to 1.91 and showed a decreasing tendency with respect to increasing rates of irrigation. 9. The location of sensors for subsurface trickle irrigation follows same pattern as above, with vertical distance from emitter being 10~17cm long and horizontal 22~25cm long. The location of emitter should be 50 cm. 10.The relationship between VS which is the volume of wetted soil and Q which is the total amount of water when soil is reached field capacity could be explained as VS= 2.914Q0.91and the irrigation rates showed no impacts on the above relationship.