Korea Aerospace Research Institute Research Articles

Development and Conversion Flight Test of a Small Tiltrotor Unmanned Aerial Vehicle

T HE tiltrotor configuration was selected as the unmanned aerial vehicle (UAV) platform for the Smart UAV (SUAV) development program, which is one of the 21st Frontier research and development programs supported by the Korean government [1]. Some of the subsystems of the SUAV, such as the rotor system, drive system, andflight control system, were especially challenging for the Korea Aerospace Research Institute to develop, due to lack of previous development experience. To reduce the risk of failure during the development, the ironbird test of the rotor and drive system and flight simulation was conducted. Although the flight simulation mitigated the risk in the flight control system development, a downscaled model was constructed in an effort to ensure the safety in the flight test of the full-scale vehicle. The small-scale platform is shown in Fig. 1. It is expected from the flight test of the small scale model to enhance the understanding of the features of the actual tiltrotor vehicle. The size of the downscaledmodelwas determined to be 1=2:5 (2m overall length) of the full-scale SUAV (5 m overall length) so as to have large enough space for the simple flight control computer, the navigation system, and the other components such as the engine and actuators. The aerodynamic performance of the 1=2:5-scale tiltrotor was analyzed using the in-house performance code. The calculated performance data were used for scheduling the control devices, such as the collective pitch of the rotors and the flaperon deflection, in the flight control logic. In this Note, sizing and performance analysis of the downscaled tiltrotor are presented in which simple codes based on blade element and momentum theory were used. The conversion corridor of the tiltrotor was predicted and the nacelle tilt angle and air speed were compared with flight-test results. After a series of progressive flight tests, conversion flight from helicopter to fixed-wing mode was accomplished. This verified that the stability and control augmentation algorithmwork properly in the flight control software. This small tiltrotor flight test is expected to reduce risks in flight test of the 5-m-span full-scale tiltrotor UAV called Smart UAV. II. Sizing of the Tiltrotor

Wind Tunnel Testing on Crosswind Aerodynamic Forces Acting on Railway Vehicles

This study is devoted to measure the aerodynamic forces acting on two railway trains, one of which is a high-speed train at 300km/h maximum operation speed, and the other is a conventional train at the operating speed 100km/h. The three-dimensional train shapes have been modeled as detailed as possible including the inter-car, the upper cavity for pantograph, and the bogie systems. The aerodynamic forces on each vehicle of the trains have been measured in the subsonic wind tunnel with 4m×3m test section of Korea Aerospace Research Institute at Daejeon, Korea. The aerodynamic forces and moments of the train models have been plotted for various yaw angles and the characteristics of the aerodynamic coefficients has been discussed relating to the experimental conditions.

Acoustic measurement for 12% scaled model of NREL Phase VI wind turbine by using beamforming

Wind tunnel test for the 12% scaled model of NREL Phase VI wind turbine was conducted at Korea Aerospace Research Institute (KARI) low speed wind tunnel. Test condition for the scaled model was decided to match the blade tip mach number with real scale model test which was conducted at NASA Ames (80′ × 120′) Tunnel. Aerodynamic performance represented by torque of the blades was measured by using the torque sensor installed in rotating shaft and compared with real scale model test results. Acoustic noise for scaled model was also measured at closed type test section with acoustic array of 144 microphones. Time based beamforming method to identify the rotating noise source position was applied to analyze the test results. 1/3 octave band was used in post processing for various wind speeds. Test results shows that the main acoustic noise source position moves toward the blade tip as frequency increases and the noise level at low frequency below 2 kHz has much higher when the blade is in stall condition.

Cooperative Task Assignment/Path Planning of Multiple Unmanned Aerial Vehicles Using Genetic Algorithm

This research was supported by the Korea Aerospace Research Institute for a program of development of the Communications, Navigation, Surveillance/Air Traffic Management system for the next generation.

위성발사체용 GPS 수신기 시스템의 개발

A GPS receiver system utilized on satellite launch vehicles should operate normally under harsh environments as well as high-dynamic conditions. The GPS receiver system to use for range safety of KSLV(Korea Space Launch Vehicle)-I that is the first satellite launch vehicle developed by KARI(Korea Aerospace Research Institute) has been confirmed to survive under the environment of the launcher through extensive terrestrial tests including humidity, high and low temperatures, vacuum, sinusoidal and random vibrations, shocks, acceleration, EMI/EMC(Electromagnetic Interference/ Electromagnetic Compatibility), etc. Several performance tests have been also carried out in order to evaluate tracking capability and accuracy of the GPS receiver under high-dynamic conditions using a GPS signal simulator. Some lessons-learned during development of the GPS receiver system and its special characteristics compared with COTS(Commercial-Off-The-Shelf) GPS receiver systems are described in this paper.

Dynamics of satellite with deployable rigid solar arrays

This research is concerned with the dynamic modeling of satellite with deployable solar arrays equipped with strain energy hinges (SEH). The SEH is a new deployment device consisting of a strip tape measure, which utilizes the buckling behavior of a thin curved shell to produce nonlinear dynamic characteristics during deployment of solar arrays. For dynamic simulation, the SEH is assumed to be a massless-nonlinear elastic member and the solar panels are assumed to be rigid bodies which are connected by the SEHs. The planar deployment is of interest in this study since the deployment of solar arrays mainly occurs in a two-dimensional plane. In deriving the equations of motion, we developed a new systematic approach suitable for the simulation of solar array deployment in space. The simulation results were compared to the ground experimental results obtained at the laboratory of Korea Aerospace Research Institute. In the ground experiments, the hub of the solar arrays was attached to the frictionless rotational bearing, and the solar arrays were hanged by bungee cables. Even though the dynamic model was derived for the space deployment of the solar arrays, the simulation result corresponding to the solar array deployment was similar to the ground experimental results thus validating the simulation model developed in this paper.

The Korean Sounding Rocket Program

As a part of the Korea National Space Program, the Korean government has led the Sounding Rocket Program by Korea Aerospace Research Institute (KARI) providing enhanced capabilities across a spectrum of earth sciences and/or astrophysics-related disciplines. In this paper, the Korean Sounding Rocket Program during 1993–2002 is introduced. This program includes Korea Sounding Rocket (KSR)-I, KSR-II, and KSR-III, and a total of five soundings were carried out. Two had flown in KSR-I series, two in KSR-II, and one in KSR-III. The main mission objective is to provide the opportunity to scientists for researching earth sciences and/or astrophysics and to improve Korean rocket development technologies including payload instruments, flight systems, ground systems, operational techniques, and interfaces between subsystems. As demand increased for launching of low-orbit earth satellites internally and externally, the Korean government was ambitiously firing the Korea Space Launch Vehicle (KSLV) Program in 2002, based on experience throughout the Sounding Rocket Program and preparing the world market for space launch vehicles.

Development of Block type Inlet Distortion Simulating Device for Gas Turbine Engine Inlet Distortion Test

In late 1960's, engineers of the engine manufacturer experienced that the distortion of inlet flow of turbofan and turbojet engine could cause the surge in compressor and affect overall engine operational performance, which result in the deterioration of stability of the engine. In this study, block type of inlet distortion simulating device has been developed in order to investigate the effect of inlet distortion on the deterioration of overall engine operational performance. The inlet distortion simulating device was installed in front of engine inlet in order to simulate distortion of inlet flow. The degree of inlet distortion was measured by rakes installed upstream the inlet distortion simulating device and between the engine inlet and inlet distortion simulating device. Before applying the inlet distortion simulating device to real engine, preliminary tests were performed with a simulated engine in order to verify the degree of inlet distortion by the device. Preliminary inlet distortion tests were performed in Altitude Engine Test Facility(AETF) of Korea Aerospace Research Institute(KARI) and results showed that the inlet distortion simulating device could be used in simulating various inlet distortion cases.

C-CMG Cluster for Small Satellites

This article presents the details of a designed control moment gyroscope (CMG) with a constant speed momentum wheel and one-axis-gimbal, and its experimental results performed at Korea Aerospace Research Institute. The CMG which is able to produce a torque of lOO mNm per each, is mounted in a pyramid configuration with four SGCMGs. Each CMG test and a single axis maneuver test with four-CMG cluster configuration are performed to confirm their performance on a ground-test facilities consisted of three major parts: a vibration isolation system, a dynamic force plate (Kistler sensor), and a DSP board. These facilities provide the accurate data of three axial and torques from the control moment gyro. Details of the CMG experimental results are presented with discussion of the experimental errors. The experimental data are compared with theoretical results and both results are used to verify their performance specifications.

터보펌프용 미케니컬 페이스 실의 수락시험

??A mechanical face seal has been tested in Korea Aerospace Research Institute for turbopump applications. In this paper the acceptance test results of the mechanical face seal are described. By means of simulating a practical operating environment, the performance against leakage of mechanical face seal is monitored. In addition the carbon wear is measured to estimate the life of a mechanical face seal. The test results show the acceptable leakage performance and resonable wear tendency as well Lastly the repeated test had been carried out to guarantee the endurance performance of mechanical face seal based on the turbopump life.

균등 및 비균등 배열 헬리콥터 반토오크 시스템 성능 및 소음특성

This paper described the performance test and sound characteristics of helicopter `Tail-Fan` anti-torque system. In this research, Korea Aerospace Research Institute(KARI) developed `Tail-Fan` anti-torque system for a helicopter and carried out performance and sound capturing tests of even and uneven tail fans. The performance test is carried out and the noise signals which are generated during the test are saved with microphones at the same time. The performance test`s results meet the design requirements. Tone-corrected perceived noise level is reduced by replacing the even product with the uneven one.

헬리콥터용 차세대 블레이드의 공력탄성학적 안정성에 관한 시험적 연구

This paper describes the aeroelastic stability test of the small-scaled `Next-generation Blade(NRSB)` with NRSH (next-generation hub system) and HCTH hingeless hub system in hover and forward flight conditions. Excitation tests of rotor system installed in GSRTS (general small-scale rotor test system) at KARI (Korea Aerospace Research Institute) were carried out to get lead-lag damping ratio of blades with flexures as hub flexure. MBA(moving block analysis) technique was used for the estimation of lead-lag damping ratio. First, NRSB-1F blades with HCTH hub system, then NRSB- 1F with NRSH hub system were tested. Second, NRSB-2F blades with NRSH hub system were tested. Tests were done on the ground and in the wind tunnel according to the test conditions of hover and forward flight, respectively. Non-rotating natural frequencies, non-rotating damping ratios and rotating natural frequencies were showed similar level for each cases. Estimated damping ratios of NRSB-1F, NRSB-2F with HCTH and NRSH were above 0.5%, and damping ratio increased by collective pitch angle increasement. Furthermore damping ratios of NRSB-2F were higher than damping ratios of NRSB-1F in high Pitch angle. It was confirmed that the blade design for noise reduction would give observable improvement in aeroelastic stability compared to paddle blade and NRSB-1F design.

Components Map Generation of Gas Turbine Engine Using Genetic Algorithms and Engine Performance Deck Data

In order to estimate the gas turbine engine performance precisely, the component maps containing their own performance characteristics should be used. Because the components map is an engine manufacturer’s propriety obtained from many experimental tests with high cost, they are not provided to the customer generally. Some scaling methods for gas turbine component maps using experimental data or data partially given by engine manufacturers had been proposed in a previous study. Among them the map generation method using experimental data and genetic algorithms had showed the possibility of composing the component maps from some random test data. However not only does this method need more experimental data to obtain more realistic component maps but it also requires some more calculation time to treat the additional random test data by the component map generation program. Moreover some unnecessary test data may introduced to generate inaccuracy in component maps. The map generation method called the system identification method using partially given data from the engine manufacturer (Kong and Ki, 2003, ASME J. Eng. Gas Turbines Power, 125, 958–979) can improve the traditional scaling methods by multiplying the scaling factors at design point to off-design point data of the original performance maps, but some reference map data at off-design points should be needed. In this study a component map generation method, which may identify the component map conversely from some calculation results of a performance deck provided by the engine manufacturer using the genetic algorithms, was newly proposed to overcome the previous difficulties. As a demonstration example for this study, the PW206C turbo shaft engine for the tilt rotor type smart unmanned aerial vehicle which has been developed by Korea Aerospace Research Institute was used. In order to verify the proposed method, steady-state performance analysis results using the newly generated component maps were compared with them performed by the Estimated Engine Performance Program deck provided by the engine manufacturer. The performance results using the identified maps were also compared with them using the traditional scaling method. In this investigation, it was found that the newly proposed map generation method would be more effective than the traditional scaling method and the methods explained above.

Development of Korean High Altitude Platform Systems

A 10-year program to develop a stratospheric airship for telecommunication relays and ground observations at 20 km altitude has started in December 2000. The program consists of 3 Phases. In 1st Phase, a 50 m unmanned airship will be developed with basic research for stratospheric airship to secure technologies required for 2nd Phase development. During the 2nd Phase development, a prototype stratospheric airship will be launched for station keeping at 20 km. The 2nd Phase development plan will take concrete shape based on the result of the 1st Phase. Then, stratospheric airship will be commercialized through 3rd Phase development. KARI, Korea Aerospace Research Institute, has been developing a 50 m unmanned airship system as its 1st Phase Program during last 3 years. KARI finished design of the system, manufacturing of components and sub-systems, tests of components and sub-systems, and total system check for flight test. KARI’s general plan and approach for developing stratospheric airship are described in this paper. The characteristics of KARI’s 50 m unmanned airship system are briefly introduced with ground and flight test results. Also, some activities for the 2nd phase are described.

초음속 충동형 터빈에 대한 시험적 고찰

1.6 MW class supersonic partial admission impulse turbine has been designed and tested in Korea Aerospace Research Institute for the liquid rocket engine application. The test has been performed using a high pressure air source facility in KARI. For the turbine power absorption, a hydraulic dynamometer has been used. Appropriate similarity relations are used for the determination of test condition. Various settings of turbine pressure ratio and rotational speed are tested to investigate global turbine characteristics. From measured data, parameters related to the turbine design are derived and validated.

테일홴 성능시험장치의 운용과 진동특성

This paper described operation and vibration characteristics of a 'tail-fan' anti-torque performance test system. KARI (Korea Aerospace Research Institute) developed a 'tail-fan' anti-torque system of a helicopter and a performance test-rig to test the performance of the tail-fan. The performance test-rig consists of driving, supporting and rotating parts. In the process of the performance test, firstly, operation test of the test-rig were carried out to verify design specifications. Secondly, natural frequencies of fan blade and test-rig were measured respectively. Lastly, to find the operation rotating speed for the performance test, vibration test were carried out using accelerometers on tail gear box. The performance test conditions of the tail-fan to avoid a resonance were found from the fan-plot and vibration test results. The tail-fan performance tests were well done safely.

고압 터보펌프용 연료펌프의 수력설계 및 성능 평가

A low NPSH and high pressure fuel pump has been designed for a turbopump system. The fuel pump has an axial inducer and a centrifugal impeller. A meanline method has been established for the preliminary design and performance prediction of pumps at design or off-design points. KeRC(Kelyish Research Center) carried out a model testing of the fuel pump with water as a working fluid at the reduced speed. Predicted performances by the method are shown to be in good agreement with experimental results for cavitating and non-cavitating conditions. The established meanline method can be used for the performance prediction and preliminary design of high speed pumps which have a inducer, impeller and volute. In the current study, the three dimensional viscous flow in the fuel pump was investigated through numerical computation. A modified design of the fuel pump was generated to improve pump performance by utilizing CFD results. The modified fuel pump was experimentally tested by ROTEM and KARI(Korea Aerospace Research Institute). The measured non-cavitating and cavitating performance showed a good agreement with designed performance.

비행 시험을 통한 비행선의 운동 특성 해석 및 시험 결과 분석

For decades, airships have being developed in Europe (especially German) and America. Airships are planning to be used for advertisements and airliners as well. In Korea, KARI (Korea Aerospace Research Institute) is developing stratospheric communication airship and the similar research is carried out in Japan. Among them, Zeppelin of German has the cutting-edge airship technology with Zeppelin NT. In this paper, the flight performance and stability were evaluated by comparing mathematical theory and the real test. The stability was examined through dynamic modeling and assured by designing controllers at each flight mode. Elevator angle, rudder angle, magnitude of thrust and tilting angle of thrust vector were used as control inputs. Moreover, after measuring the airship velocity, flight direction, magnitude and direction of the wind, attitude angles and trajectories of the airship at each flight mode, the results were compared with the simulation. To get the reasonable data, low-pass filter and band-stop filter were designed to get rid of the sensor noise and engine vibration. The test was accomplished at cruise mode, turning mode, and deceleration. To conclude, with comparing the simulation data and flight test data, it could be known that the dynamic model used in this paper was reasonable.

신경회로망을 이용한 틸트로터 항공기 SCAS 설계

This paper presents the design and evaluation of a tiltrotor attitude controller. The implemented response type of the command augumentation system is Attitude Command Attitude Hold. The controller architecture can alleviate the need for extensive gain scheduling and thus has the potential to reduce development time. The control algorithm is constructed using the feedback linearization technique. And an on-line adaptive architecture that employs a neural network compensating the model inversion error caused by the deficiency of full knowledge tiltrotor aircraft dynamics is applied to augment the attitude control system. The use of Lyapunov stability analysis guarantees boundedness of the tracking error and network parameters. The performance of the controller is evaluated against ADS-33E criteria, using the nonlinear tiltrotor simulation code for Bell TR301 developed by KARI. (Korea Aerospace Research Institute)

틸트로터 항공기의 경로점 추종 비행유도제어 알고리즘 설계 : 헬리콥터 비행모드

This paper deals with an autonomous flight guidance and control algorithm design for TR301 tilt-rotor airplane under development by Korea Aerospace Research Institute for simulation purpose. The objective of this study is to design autonomous flight algorithm in which the tilt-rotor airplane should follow the given waypoints precisely. The approach to this objective in this study is that, first of all, model-based inversion is applied to the highly nonlinear tilt-rotor dynamics, where the tilt-rotor airplane is assumed to fly at helicopter flight mode(nacelle angle