축소형 틸트로터 무인기의 전자동 비행시험을 위한 문제해결과정

강영신,박범진,유창선,구삼옥,이장호 한국항공우주연구원 2009 항공우주기술 Vol.8 No.1

The ground integration test of Smart UAV has been performed according to the flight test plan. The flight test of full scaled model will be performed followed by 4 DOF ground rig test and a tethered hover test. Smart UAV is the first indigenous tiltrotor aircraft which can fly with fast cruise speed and take off or land vertically. In order to prove the flight control law of Smart UAV, the 40% scaled airplane was developed and have been tested. During flight test of small scaled model, many unique and unexpected problems occurred. After clearing these problems, fully automatic flight test was performed successfully. The experiences about many trouble shooting and resolving the problems would be basic material to avoid the unexpected but similar flight test problems hidden behind of the full scaled Smart UAV. This paper presents the detailed procedures of trouble shootings to solve the unique problems which occurred during the flight test of small scaled tiltrotor UAV. 스마트무인기는 수직이착륙과 고속비행이 동시에 가능하도록 헬리콥터와 고정익 항공기의 장점을 결합한 틸트로터 항공기이다. 현재 지상통합시험을 수행중이며, 4자유도 지상치구시험과 안전줄 호버시험을 거쳐 비행시험을 수행할 예정이다. 스마트무인기에 적용된 제어법칙을 검증하기 위해서 40%축소기를 개발하여 비행시험을 수행하였다. 비행시험결과 예측하기 어려웠던 틸트로터 항공기의 고유한 기술적인 문제점들이 발생하였으며, 이러한 문제점을 해결하여 전자동 비행시험을 완료하였다. 본 논문에서는 국내 최초로 수행된 축소형 틸트로터 항공기의 비행시험 과정 중에 발생한 주요한 문제점을 서술하고, 그 해결과정을 상세하게 기술하였다. 축소형 틸트로터 항공기의 전자동 비행시험 수행을 통해 경험한 시행착오와 개선사항은 향후 계획된 스마트 무인기의 실물기 비행시험을 성공할 수 있는 훌륭한 초석이 될 것이다.

Modified Similitude Law for Pseudodynamic Test on Small-scale Steel Models

Kim Nam-Sik,Kwak, Young Hak,Chang Sung pil 한국지진공학회 2003 한국지진공학회논문집 Vol.7 No.6

지진하중에 대한 구조물의 동적 거동과 내진성능을 평가하기 위하여 유사동적실험기법이 흔히 사용되고 있으나, 실험장비의 제약과 구조물의 규모 등으로 대부분 축소모형실험에 의존하고 있다. 그러나 일반적인 상사법칙은 탄성범위에서 유도된 것으로 지진거동과 같은 비탄성 거동을 예측하는 경우에는 한계가 있기 때문에 축소모형의 실험결과를 원형 구조물에 직접 적용하는 것은 많은 주의가 필요하다. 본 연구에서는 원형구조물과 축소모형에 대한 철골모형을 실험 대상으로 하여 실제 축소모형 실험결과로부터 원형구조물의 거동을 예측하는 경우의 문제점을 확인하고, 그 해결방법을 모색하고자 한다. 실제로 축소모형실험에서는 원형구조물의 경계조건을 정확히 재현하기 어려우며, 축소모형의 제작과정과 실험과정에서의 모든 오차가 강성의 변화로 반영되어 나타난다. 따라서 본 연구에서는 기하학적 상사율과 축소모형의 변화된 강성비를 함께 고려한 수정된 상사법칙을 제안하였으며, 수정된 상사법칙이 적용된 축소모형에 대하여 유사동적실험을 수행하여 지진응답결과를 원형구조물의 결과와 비교하였다. 축소모형에 대한 유사동적실험결과로부터 제안된 상사법칙을 적용함으로써 원형구조물의 지진응답 재현이 효과적임을 입증하였다. Although there are several experimental techniques to evaluate the seismic behavior and performance of civil structures, small-scale models in mast of physical tests, instead of prototypes or large-scale models, would be used due to a limitation on capacities of testing equipments. However, the inelastic seismic response prediction of small-scale models has some discrepancies inherently because the similitude law is generally derived in the elastic range. Thus, a special attention is required to regard the seismic behavior of small-scale models as one of prototypes. In this paper, differences between prototypes and small-scale models pseudodynamically tested on steel column specimens are investigated and an alternative to minimize them is suggested. In general, small-scale models could have the distorted stiffness induced from some experimental errors on test setup, steel fabrication and so on. Therefore, a modified similitude law considering both a scale factor for length and a stiffness ratio of small-scale model to prototype is proposed. Using the modified similitude law to compensate experimental errors, the pseudodynamic test results from modified small-scale model are much improved as compared with the results of prototype. According to the pseudodynamic test results of small-scale steel models, it can be concluded that the modified similitude law proposed could be effective in simulating the seismic response of prototype structures.

Experimental hover performance evaluation on a small-scale rotor using a rotor test stand

Lee, Byoung-Eon,Byun, Young-Seop,Kim, Jeong,Kang, Beom-Soo 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.6

This paper presents the work being carried out in order to deduce hover performance of a small-scale single rotor blade as a preliminary study of a small coaxial rotor helicopter development. As an initial research, a test stand capable of measuring thrust and torque of a small-scale rotor blade in hover state was constructed and fabricated. The test stand consists of three parts; a rotating device, a load measuring sensor and a data acquisition system. Thrust and torque were measured with varying collective pitch angle at fixed RPM. Through this research, hover performance tests were conducted for a small-scale single rotor blade operating in low Reynolds numbers ($Re{\approx}3{\times}10^5$). The rotor blades investigated in this paper have maximum FM values varying from 0.59 to 0.65, which are low relative to modem full-scale helicopters. From these differences in FM between a small and a full-scale helicopter, the induced power factor is determined as varying from 1.35 to 1.42. Through this study, tests of hover performance were conducted for a single small-scale rotor blade, as well as verifying the test stand itself for the acquisition of hover performance.

A Study on the Fracture Toughness Evaluation Method of High Strength Steel for containership

Hong-Yeol Bae(배홍열),Do Yup Lee(이도엽),Bo Young Jeong(정보영) 대한용접·접합학회 2021 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2021 No.5

As the size of the container ship increased, the strength and thickness of steel applied to the UD and HSC part also increased. Thus also it increased probability of unstable fracture. Reflecting this situation, the IACS has made mandatory regulations requiring steel plate with excellent fracture toughness(BCA steel) to be applied. In general, Kca and CAT are widely used as parameters representing the fracture toughness of steel. However, in order to obtain these parameter, a large scale tensile test machine with a capacity of over 1400 tons is generally required. In addition, this is an experiment using the full thickness of the steel, and about 3 to 5 specimens are required per set. Therefore, this large-scale test is very expensive and time consuming. Particularly, most of the international class societies require a guarantee of fracture toughness for each steel plate when production stage. Therefore, it is very difficult to producing BCA steel. To solve this problem, a small-scale test method that can replace the large-scale test has been proposed, and studies have been conducted by many researchers. Of course, there are test methods that have already been developed and are commonly applied, but as the thickness and strength of steels increase, many researchers have raised many problems with the reliability of the existing small-scale test methods. This is because BCA steel was developed through the unique technology of each steel company due to its characteristics. Therefore, it was suggested that it would be reasonable to independently develop a small-scale test method suitable for each company’s development concept rather than a test method that can be applied generally. This study is about a small-scale test method that considers the development concept of the BCA steel independently developed by POSCO.

소형 로터 블레이드의 제자리 비행 성능 시험장치 개발 및 검증

이병언(Byoung-Eon Lee),서진우(Jin-Woo Seo),변영섭(Young-Seop Byun),김정(Jeong Kim),이관중(Kwanjung Yee),강범수(Beom-Soo Kang) 한국항공우주학회 2009 韓國航空宇宙學會誌 Vol.37 No.10

본 논문은 동축반전 로터 블레이드의 성능 특성 파악을 위한 선행연구로서, 단일 로터 블레이드에 대한 공력 데이터 획득 및 성능 특성을 확인하기 위한 연구에 중점을 두었다. 이를 위해 제자리 비행 상태에서 추력과 토크의 측정이 가능한 소형 로터 블레이드용 회전 시험장치를 구성하고 제작하였다. 로터 회전 시험장치는 회전장치부, 센서부, 그리고 데이터 획득 시스템으로 구성되었으며, 고정된 회전속도에서 콜렉티브 피치각을 변화시키면서 추력과 토크를 측정할 수 있도록 하였다. 이를 통하여 저 레이놀즈 수 (Re?3×10?) 영역에서 운용되는 단일 로터의 제자리 비행 성능 시험을 수행하였고 소형 로터 블레이드의 제자리 비행 성능을 획득하여 로터 회전 시험장치의 성능을 검증하였다. This paper presents the work being carried out in order to deduce hover performance of a small-scale single rotor blade as a preliminary study of a small coaxial rotor helicopter development. As an initial research, a test stand capable of measuring thrust and torque of a small-scale rotor blade in hover state was constructed and fabricated. The test stand consists of three parts; a rotating device, a load measuring sensor and a data acquisition system. Thrust and torque were measured with varying collective pitch angle at fixed RPM. Through this research, hover performance tests were conducted for a small-scale single rotor blade operating in low Reynolds number (Re ?3×10?), as well as for verifying the test stand itself for acquiring hover performance.

직경 2m급 축소로터 시험장치 개조 및 보완

송근웅(Song Keun Woong),이재하(Lee Jae Ha),김승호(Kim Seoung Ho) 한국소음진동공학회 2012 한국소음진동공학회 학술대회논문집 Vol.2012 No.10

Small-scaled Rotor Test facility(GSRTS, General Small-scaled Rotor Test Facility) in KARI could not use the test because facility aging and parts discontinued. Also in order to perform a joint international research, GSRTS modifications should be needed. So requirements of GSRTS modifications were established and according to the requirements, GSRTS modifications were conducted. Facility operation test, 6-component fixed balance calibration, Small-scaled OLS rotor performance test were performed to verify the results of GSRTS modifications. Reasonable results were obtained in comparison to calculation results. Then GSRTS ready was completed to conduct international collaborative research and wind tunnel test.

Fire Resistance of Hybrid Floor Based on Small-Scale Furnace Tests and Energy-Based Time Equivalent Approach

박민재,배재훈,류재호,주영규 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.6

A novel hybrid floor, which was a prefabricated composite system infilled using polymers with hollow cores between its top and bottom steel plates, was previously developed for application in steel structures. In addition, the structural performance of the steel floor, including its bending capacity, floor vibration, and dynamic characteristics, were investigated. However, as the fire resistance performance of the hybrid floor had not been investigated, it was installed in actual buildings using insulating materials, which caused problems, such as a dirty workplace and additional work that prolonged the construction period. In this study, small-scale furnace tests, whose specimens have fewer variables in comparison with those of full-scale tests, were conducted instead of full-scale furnace tests to analyze the effects of various variables on the fire resistance performance of the hybrid floor. In fact, the heating curves obtained via the small-scale furnace tests were not similar those suggested by Korean Standards (KS). The energy-based time equivalent approach was applied to calibrate the results. Thus, the fire resistance ratings were estimated based on small-scale furnace tests via the energy-based time equivalent approach with respect to polymer thickness and aspect ratio, which were expressed using the lengths and widths of the specimens.

진동대실험을 통한 축소 아치구조물의 고유진동주기 분석

김기철,강주원,Kim, Gee-Cheol,Kang, Joo-Won 한국공간구조학회 2015 한국공간구조학회지 Vol.15 No.4

Large spatial structures can not easily predict the dynamic behavior due to the lack of construction and design practices. The spatial structures are generally analyzed through the numerical simulation and experimental test in order to investigate the seismic response of large spatial structures. In the case of analysis for seismic response of large spatial structure, the many studies by the numerical analysis was carried out, researches by the shaking table test are very rare. In this study, a shaking table test of a small-scale arch structure was conducted and the dynamic characteristics of arch structure are analyzed. And the dynamic characteristics of arch structures are investigated according to the various column cross-section and length. It is found that the natural vibration periods of the small-scaled arch structure that have large column stiffness are very similar to the natural vibration period of the non-column arch structure. And in case of arch structure with large column stiffness, primary natural frequency period by numerical analysis is very similar to the primary natural frequency period of by shaking table test. These are because the dynamic characteristics of the roof structure are affected by the column stiffness of the spatial structure.

Prediction of Hover Performance on Development of Small-Scale UAV Using Experimental and Numerical Approach

Byoung-Eon Lee,Sang-Deok Kim,Young-Seop Byun,Jeong Kim,Beom-Soo Kang 한국항공우주학회 2008 한국항공우주학회 학술발표회 논문집 Vol.- No.-

Prediction of the rotor blade performance is important for determining design factors such as weight and size in development of a small-scale helicopter. Generally, prediction of helicopter performance means the estimation of the power required for a given flight condition. However, due to lack of test data and analyzed results for small-scale rotor blade (Re ? 3×10?) this is not an easy task. As an initial research, this work performed a modeling of a single rotor configuration with FLlGHTLAB, a representative commercial comprehensive helicopter simulation tool. Where the experimental data of the induced power factor and the average profile drag coefficients of the blades from rotor test stand was used. Rotor test stand was constructed to investigate aerodynamic characteristics of small rotors, for the test bed operation, the thrust and torque were measured with varying collective pitch angle and fixed RPM. An extra emphasis of the work was on the correction effort that applies experimental aerodynamic data to the existing airfoil data improving reliability of the simulation. In this process, we performed small-scale isolated single rotor by experimental and numerical method and achieved good agreement of the hover performance on the test data and simulation results.

KARI 축소 로터 시험장치(GSRTS) 구조해석

김덕관(Deog-Kwan Kim) 한국항공우주연구원 2008 항공우주기술 Vol.7 No.1

본 논문은 항우연에서 운용 중에 있는 축소 로터 시험장치(General Small-scaled Rotor Test System, GSRTS)에 대한 구조 안전성 확보를 위한 구조해석 수행 결과를 제시하고 있다. 프루드(froude) 축소 및 마하(mach) 축소 시험을 수행하고, 관절형 및 무한지 로터 등 다양한 로터 시스템 적용을 위해서는 시험장치의 안전성 확보와 운용상의 능력 범위를 확인하기 위해 로터 운용 조건에서 나오는 기준하중을 이용하여 구조 안전계수를 산출하였다. 특히, 구동계통(drive system)은 베어링 및 기어, 축 등으로 구성되어 있어 운용상의 안전성 확보가 우선적으로 요구되는 필수 항목이다. 구조해석은 구동계통의 기본 부품의 형 상 및 재료 물성치를 이용하여 해석적 방법으로 구하였다. 본 로터 시험장치는 설계된 안전계수 안에서 운용을 해야 하며, 향후 KUH 축소 풍동모델 시험을 적용할 때도 하중계산을 통해서 시험시 운용조건의 범위를 정해야한다. This paper describes the structural analysis results of KARI General Small-scaled Rotor Test System (GSRTS) operated in KARI to verify operational safety. This GSRTS was developed to conduct a froude and mach small-scaled rotor test. Tills analysis was performed to investigate the structural Factor of Safety for the various small-scale rotor system like articulated or hingeless rotor and to check the operational capability using given operational design load. Specially, drive system has several bearings, mechanical gears, shaft, etc. and these parts must be required to achieve an operational safety. The calculation was done by using geometric data and material properties by analytical method. This rotor test system should be operated within these calculated Factor of Safety. Furthermore, the operational limitation should be defined as applied to small-scale rotor system of KUH in future.