• 신재생에너지
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• 제16권2호
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• pp.1-13
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• 2020

The reduction of noise from wind turbines has been studied using various methods. Some examples include controlling wind turbine blades, designing low-noise-emitting wind turbine blades, and using trailing-edge serrations. Among these methods, serration is considered an effective noise reduction method. Various studies have aimed to understand the effects of trailing-edge serration parameters. Most studies, however, have focused on fixed-wing concepts, and few have analyzed noise reduction or developed a prediction method for rotor-type blades. Herein, a noise prediction method, composed of two noise prediction methods for a wind turbine with trailing-edge serrations, is proposed. From the flow information obtained by an in-house program (WINFAS), the noise from non-serrated blades is calculated by turbulent ingestion noise and airfoil self-noise prediction methods. The degree of noise reduction caused by the trailing-edge serrations is predicted in the frequency domain by Lyu's method. The amount of noise reduction is subtracted from the predicted result of the non-serrated blade and the total reduction of the noise from the rotor blades is calculated.

• 한국항공우주학회지
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• 제33권7호
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• pp.76-84
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• 2005

스마트 무인기 비행하중해석을 위해서는 규정과 하중조건을 준비하고, 공기력, 중량 및 구조 모델링을 수행해야 한다. 항공기 비행하중 해석시 공기력은 일반적으로 패널방법을 이용하여 산출하게 된다. 본 연구에서는 하중해석을 위해 In-house 프로그램인 ARGON을 사용하였다. ARGON은 KARI와 TsAGI가 공동 개발한 고정익 항공기 설계 프로그램으로서 비행하중, 지상하중, 플러터 및 응력해석을 지원한다. 본 논문에서는 FAR 23급 항공기인 스마트 무인기의 비행하중해석을 ARGON을 이용하여 수행하였고 그 결과를 제시하였다.

• 한국농공학회논문집
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• 제57권6호
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• pp.91-97
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• 2015

The Unmanned Aerial Vehicles (UAVs) have several advantages over conventional RS techniques. They can acquire high-resolution images quickly and repeatedly. And with a comparatively lower flight altitude i.e. 80~400 m, they can obtain good quality images even in cloudy weather. Therefore, they are ideal for acquiring spatial data in cases of small agricultural field with mixed crop, abundant in South Korea. This paper discuss the use of low cost UAV based remote sensing for classifying crops. The study area, Gochang is produced by several crops such as red pepper, radish, Chinese cabbage, rubus coreanus, welsh onion, bean in South Korea. This study acquired images using fixed wing UAV on September 23, 2014. An object-based technique is used for classification of crops. The results showed that scale 250, shape 0.1, color 0.9, compactness 0.5 and smoothness 0.5 were the optimum parameter values in image segmentation. As a result, the kappa coefficient was 0.82 and the overall accuracy of classification was 85.0 %. The result of the present study validate our attempts for crop classification using high resolution UAV image as well as established the possibility of using such remote sensing techniques widely to resolve the difficulty of remote sensing data acquisition in agricultural sector.

• 한국군사과학기술학회지
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• 제19권5호
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• pp.654-661
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• 2016

An unmanned aircraft refers to an aircraft which carries no human pilot and is operated under remote control or in autonomous operational mode. An unmanned aircraft system consist of a one system which include UAV(s), UAV control station and data link, etc. As the UAVs can perform the dull, dangerous and difficult missions, various kinds of UAVs with different sizes and weights have been developed and operated for both civil and military areas. It is important to develop the airworthiness certification criteria of the UAVs to minimize the risks of fatal impacts on human life and environment and to achieve the equivalent level of safety to the manned aircraft. Analysis of the KAS Part 23 and STANAG 4671 can provide guidelines for the generation of the airworthiness certification criteria for the UAVs in civil application.

• 한국토양비료학회지
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• 제50권5호
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• pp.409-421
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• 2017

Recently Unmanned Aerial Vehicle (UAV) technology offers new opportunities for assessing crop growth condition using UAV imagery. The objective of this study was to select optimal vegetation indices and regression model for estimating of rice growth using UAV images. This study was conducted using a fixed-wing UAV (Model : Ebee) with Cannon S110 and Cannon IXUS camera during farming season in 2016 on the experiment field of National Institute of Crop Science. Before heading stage of rice, there were strong relationships between rice growth parameters (plant height, dry weight and LAI (Leaf Area Index)) and NDVI (Normalized Difference Vegetation Index) using natural exponential function ($R{\geq}0.97$). After heading stage, there were strong relationships between rice dry weight and NDVI, gNDVI (green NDVI), RVI (Ratio Vegetation Index), CI-G (Chlorophyll Index-Green) using quadratic function ($R{\leq}-0.98$). There were no apparent relationships between rice growth parameters and vegetation indices using only Red-Green-Blue band images.

• 항공우주시스템공학회지
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• 제9권3호
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• pp.1-7
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• 2015

In this study, the design of compound smart materials hydraulic pump that can be applied to a small-medium size UAV having a limited space envelope and weight has been conducted. Compound Smart Material Pump(CSMP) proposed in this paper is composed of a pressurize pump and a flow pump for supplying the high pressure and fluid displacement to overcome the disadvantages of the piezoelectric actuator which has a small strain. Though this compound smart material pump has been designed as small size and lightweight as possible, it can sequentially supply the sufficient large flow rate and pressure required for the brake operation. For the design of CSMP, about 2,700 kg (6,000 lb) class fixed wing manned aircraft was selected. Based on the established requirements, the design of the CSMP have been done by strength, vibration, and fluid flow analysis.

• 상하수도학회지
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• 제32권6호
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• pp.573-581
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• 2018

The purpose of this study is to evaluate the fixed wing type domestic UAV for monitoring of algae bloom in aquatic environment. The UAV used in this study is operated automatically in-flight using an automatic navigation device, and flies along a path targeting preconfigured GPS coordinates of desired measurement sites input by a flight path controller. The sensors used in this study were Sequoia multi-spectral cameras. The photographed images were processed using orthomosaics, georeferenced digital surface models, and 3D mapping software such as Pix4D. In this study, NDVI(Normalized distribution vegetation index) was used for estimating the concentration of chlorophyll-a in river. Based on the NDVI analysis, the distribution areas of chlorophyll-a could be analyzed. The UAV image was compared with a airborne image at a similar time and place. UAV images were found to be effective for monitoring of chlorophyll-a in river.

• Advances in aircraft and spacecraft science
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• 제6권1호
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• pp.31-49
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• 2019

Flutter is a dangerous phenomenon encountered in flexible structures subjected to aerodynamic forces. This includes aircraft, helicopter blades, engine rotors, buildings and bridges. Flutter occurs as a result of interactions between aerodynamic, stiffness and inertia forces on a structure. The conventional method for designing a rotor blade to be free from flutter instability throughout the helicopter's flight regime is to design the blade so that the aerodynamic center (AC), elastic axis (EA) and center of gravity (CG) are coincident and located at the quarter-chord. While this assures freedom from flutter, it adds constraints on rotor blade design which are not usually followed in fixed wing design. Periodic Structures have been in the focus of research for their useful characteristics and ability to attenuate vibration in frequency bands called "stop-bands". A periodic structure consists of cells which differ in material or geometry. As vibration waves travel along the structure and face the cell boundaries, some waves pass and some are reflected back, which may cause destructive interference with the succeeding waves. In this work, we analyze the flutter characteristics of a helicopter blades with a periodic change in their sandwich material using a finite element structural model. Results shows great improvements in the flutter forward speed of the rotating blade obtained by using periodic design and increasing the number of periodic cells.

• 한국항공운항학회지
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• 제31권1호
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• pp.11-17
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• 2023

In this study, the correlation analysis between total system error and environmental factor variables was performed to confirm the effect on the performance of the integrated navigation system by various environmental factors. To collect flight data of hybrid vertical take-off and landing UAVs, scenarios including various turning sections and straight sections such as left turn, right turn, turning rate, and path change angle were selected, and environmental data of wind direction, wind speed, temperature, air pressure, and humidity were collected in real time through weather station. As a result of the correlation analysis between the collected flight data and environmental data, it was concluded that the performance of the integrated navigation system by environmental factors within the collected data was not significant affected and was robust.

• 한국항공운항학회지
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• 제31권2호
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• pp.66-71
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• 2023

In the case of the Navy, if some of the co-pilots are included in the long-term promotion process due to the limited number of co-pilots, operational flight and administrative tasks will be added to the co-pilots not included in the rest of the Pilot in commander process. Therefore, to solve this problem, the co-pilot who has passed the PQS step-by-step process minimizes the personnel gap in the flight operation unit through a system that evaluates whether it is possible to perform its duties as a co-pilot through actual flight after entering the school. The advantage of the PQS course is that you can control flight plans on your own and minimize gaps in flight and ground work while carrying out the curriculum, but you can't focus on education or improve your skills due to irregular training flight cycles. Therefore, in this study, after collecting opinions on effective flight cycles through a survey of pilots of P-3C, the Navy's fixed-wing aircraft representative, we will analyze the association of aircraft volume performance by flight cycle to derive the optimal flight cycle of the P-3C pilot course.