• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.697-697
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• 2012

하나의 측선에 대해 3점법으로 세 지점의 유속을 동시에 측정할 수 있는 장치를 고안하였으며, '다수심 유속계'라 명명하였다. 본 장치는 5단의 관절부를 이용하여 등수심을 유지하며, 표면에서 수심을 측정하는 동시에 피그미 유속계를 이용하여 3지점의 유속 (V0.2, V0.6, V0.8)을 취득할 수 있다. 다수심 유속계의 현장 적용 실험을 실시하였다. 프로펠러 유속계와 다수심 유속계를 이용하여 유량을 측정한 결과, 거의 유사한 유량을 확인할 수 있었다. 하지만 측정시간의 경우 프로펠러 유속계는 약 1시간, 다수심 유속계는 약 30분으로 약 2배에 가까운 차이를 확인할 수 있었다. 한편 현재 개발 단계에 있는 다수심 유속계는 25cm 이상의 수심에서 3점자료 취득이 가능함으로써 하천 형상에 따른 유체 흐름 파악에 적합하며, 관측 자료의 신뢰도 향상에 기여할 수 있다고 판단된다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.6
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• pp.455-462
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• 2017

In recent decades, many researchers have been struggling to developing the compound aircraft that is capable high speed and VTOL flight. And in recent years, multi-copters are very popular because of having advantages of VTOL and easy handling, but they are lack of doing long-range mission. Therefore, we presents simple aircraft architecture which is equipped fixed wing, multi propellers and no control surfaces. In this paper, we designed the attitude control for the compound aircraft prototype and measured the attitude control performance with flight test for validating prototype's performance. We analysed the attitude control test result comparing with similar size of a fixed wing aircraft. The performance was almost same as fixed wing aircraft.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.2
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• pp.107-120
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• 2021

Electric-powered distributed propulsion aircraft possess a complex wake flow and mutual interference with the airframe, due to the use of many propellers. Accordingly, in the early design stage, rapid aerodynamic and load analysis considering the effect of propellers for various configurations and flight conditions are required. In this study, an efficient panel-based aerodynamic analysis method that can take into account the propeller effects is developed and validated. The induced velocity field in the region of propeller wake is calculated based on Actuator Disk Theory (ADT) and is considered as the boundary condition at the vehicle's surface in the three-dimensional steady source-doublet panel method. Analyses are carried out by selecting an isolated propeller of the Korea Aerospace Research Institute (KARI)'s Quad Tilt Propeller (QTP) aircraft and the propeller-wing configuration of the former experimental study as benchmark problems. Through comparisons with the results of computational fluid dynamics (CFD) based on actuator methods, the wake velocity of propeller and the changes in the aerodynamic load distribution of the wing due to the propeller operation are validated. The method is applied to the analysis of the Optional Piloted Personal Aerial Vehicle (OPPAV) and QTP, and the practicality and validity of the method are confirmed through comparison and analysis of the computational time and results with CFD.

• Journal of the Korean Society of Marine Environment & Safety
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• v.30 no.1
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• pp.108-117
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• 2024

In this study, simulations based on computational fluid dynamics were performed for self-propulsion performance prediction of a catamaran that has asymmetrical inside and outside hull form and numerous knuckle lines. In the simulations, the Moving Reference Frame (MRF) or Sliding Mesh (SDM) techniques were used, and the rotation angle of the propeller per time step was different to identify the difference using the analysis technique and condition. The propeller rotation angle used in the MRF technique was 1˚ and those used in the SDM technique were 1˚, 5˚, or 10˚. The torque of the propeller was similar in both the techniques; however, the thrust and resistance of the hull were computed lower when the SDM technique was applied than when the MRF technique was applied, and higher as the rotation angle of the propeller per time step in the SDM technique was smaller in the simulations for several revolutions of the propeller to estimate the self-propulsion condition. The revolutions, thrust, and torque of the propeller in the self-propulsion condition obtained using linear interpolation and the delivered power, wake fraction, thrust deduction factor, and revolutions of the propeller obtained using the full-scale prediction method showed the same trend for both the techniques; however, most of the self-propulsion efficiency showed the opposite trend for these techniques. The accuracy of the propeller wake was low in the simulations when the MRF technique was applied, and slight difference existed in the expression of the wake according to the rotation angle of the propeller per time step when the SDM technique was applied.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2002.11a
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• pp.91-95
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• 2002

This paper describes the design of planar circulators with propellers resonator including a plurality of symmetric magnetic walls. One purpose of the paper is to present insertion loss on this resonator for magnetic loss, dielectric loss, magnetic field and saturation magnetization. Another is to study the effect of propeller resonator on response characteristics. The paper includes the description of one commercial circulator that is compatible with the data obtained

• Journal of Advanced Navigation Technology
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• v.27 no.2
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• pp.214-220
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• 2023

Because there exist a region in the rotational speed and torque map that the a particular combination of a motor and an ESC (Electronic Speed Control) can maintain its peak efficiency, identifying this region is important for designing an efficient system. Firstly the accuracy of the measurement device is verified using the published propeller measurement data. And then, the combined motor-ESC efficiencies of an individual propeller are measured at a wide range of rotational speeds. With measurements obtained from a large number of different propellers, efficiency contours are obtained. It is shown that there exist a significant difference between the measured combined efficiency and the motor efficiency computed using a simple model. In addition, with the same motor, the combined efficiency can have a meaningful variation depending on the model of the ESC. The efficiency contours derived from this study will be useful for the design and optimization of electric propulsion systems of an aircraft where propulsion efficiency is critical.

• Proceedings of the Korea Information Processing Society Conference
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• 2019.10a
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• pp.1056-1059
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• 2019

본 논문은 SLAM 기술로 3D 매핑하고 태양광 발전기 패널 표면의 오염영역을 파악하여 청소하는 자율비행 드론에 대한 연구이다. 본 프로젝트에서 구현된 드론은 SLAM 기술을 활용하여 3D 매핑과 ROS Topic 통신으로 자율비행을 하면서 카메라로 촬영한 영상에서 태양광 발전기 패널을 파악하고 패널에 있는 얇은 먼지막을 프로펠러에 의하여 발생하는 바람으로 제거한다. 그리고 열화상 카메라로 확인된 고오염 또는 고장으로 인한 발열 부분에 페인트 볼을 떨어트려 시각적으로 표시하고 관리자에게 능동적으로 알린다. 이로 인해 제안된 방법에 따라 넓은 영역에 분포된 다수의 태양광 발전기 패널의 오염정도를 쉽게 파악하고 저오염 영역의 즉각적인 청소 및 고오염 영역의 빠른 보고로 인하여 전반적인 태양광 발전 효율을 제고할 수 있으며, 수동으로 이루어지는 인력 관리에 비하여 오염지역 파악 및 제거 시간이 보다 빠르고 정확하게 이루어질 수 있다.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06a
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• pp.403-406
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• 2011

한국해양연구원에서는 국토해양부의 지원을 받아 2010년 7월부터 새로운 개념의 해저로봇 개발에 착수하였다. 새로이 개발되는 해저로봇은 프로펠러 방식으로 추력을 얻는 기존의 해저로봇과는 달리 여러 개의 관절로 이루어진 6개의 다리를 이용하여 해저면에 근접해서 보행과 유영으로 이동하는 해저로봇으로 강조류와 악시계의 환경에서도 운용이 가능한 로봇이다. 이 해저보행로봇 시스템은 선상시스템과 완충기, 그리고 해저보행로봇으로 구성되며, 이들 사이는 광변환기를 통해서 광케이블로 연결된다. 선상시스템에는 해저로봇의 제어 및 모니터링을 위하여 10대의 컴퓨터가 설치되어 있고, 완충기와 해저로봇에 각각 1대의 입출력 컴퓨터가 내장되어 장착된 센서와 모터의 인터페이스를 담당한다. 본 논문에서는 해저보행로봇의 통신 시스템을 소개하고, 이 통신 시스템에서 사용되기 위하여 설계된 메시지의 통신 프로토콜을 설명한다. 해저보행로봇 시스템의 주 네트워크는 기가비트 이더넷이며, 안정된 통신 환경의 소규모 독립 네트워크이다. 완충기와 해저보행로봇에는 최대 100㎐로 동작하는 다양한 직렬 통신 방식을 갖는 다수의 센서와 모터가 장착되어 있는데, 입출력 컴퓨터가 이더넷 네트워크와의 인터페이스 역할을 수행하여 계층적 네트워크를 구성한다. 로봇 제어에서는 실시간성이 중요하기 때문에 이더넷에서 통신 메시지는 한 번의 전송으로 여러 컴퓨터에 전달할 수 있도록 멀티캐스팅을 사용하여 전송된다. 설계된 통신 프로토콜은 이러한 해저로봇 시스템의 특성에 적합한 간결한 구조로 설계되었으며, 최대 255개의 주소를 지정할 수 있고 255 종류의 메시지 형태를 설정할 수 있다.

• The Journal of the Acoustical Society of Korea
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• v.35 no.2
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• pp.110-117
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• 2016

Passive sonar systems detect and classify the target by analyzing the radiated noises from vessels. If multiple noise sources exist within the sonar detection range, it gets difficult to classify each noise source because mixture of noise sources are observed. To overcome this problem, a beamforming technique is used to separate noise sources spatially though it has various limitations. In this paper, we propose a new method that uses a FDICA (Frequency Domain Independent Component Analysis) to separate noise sources from the mixture. For experiments, each noise source signal was synthesized by considering the features such as machinery tonal components and propeller tonal components. And the results of before and after separation were compared by using LOFAR (Low Frequency Analysis and Recording), DEMON (Detection Envelope Modulation On Noise) analysis.