• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.7
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• pp.527-534
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• 2018

The endurance of the multi-copter is one of the important variables that determine the mission performance. Therefore, accurate endurance should be defined as essential for performing effective missions. In this paper, we present the results of the study on the flight performance of the aircraft, especially the hovering of the drone(multi-copter). Unlike conventional aircraft, which consider aerodynamic performance by the fuselage, the multi-copter is mostly determined by the propulsion system. Therefore, the research method classifies the various parts constituting the drone system into functions, analyzes the performance of the unit parts and obtains the experimental data by sorting out the specifications and functions at the component level and mathematical formulation, The results of this study are as follows. In addition, the 5kg class quad copter was used to predict and verify the voltage change with endurance through analysis of in situ flight. By predicting endurance under various conditions, it can help design/build the right Multi-copter for mission.

• Journal of Advanced Navigation Technology
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• v.21 no.5
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• pp.450-458
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• 2017

This paper presents dynamic modelling and simulation study on attitude/altitude control of an insect-mimicking flapping micro aerial vehicle during hovering. Mathematical modelling consists of three parts: simplified flapping kinematics, flapping-wing aerodynamics, and six degree of freedom dynamics. Attitude stabilization is accomplished through linear quadratic regulator based on the linearized model of the time-varying nonlinear system, and altitude control is designed in the outer loop using PID control. The performance of the proposed controller is verified through numerical simulation where attitude stabilization and altitude control is done for hovering. In addition, it is confirmed that the attitude channel by periodic control is marginally stable against periodic pitching moment caused by flapping.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.6
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• pp.1-9
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• 2006

본 연구의 목적은 여러 가지 비행 모드 상의 로터 성능을 효율적으로 예측하는 것이다. 헬리콥터의 공력 특성을 예측하기 위한 비정상 source-doublet 패널 기법 기반의 수치 기법을 개발하였다. 후류의 형상 예측에는 시간 전진 자유후류모델이 사용되었다. 점성에 의한 확산을 고려한 후류의 roll-up 모사를 위하여 후류의 doublet 패널은 같은 강도의 와류고리로 대체하여 계산하였다. 후류와 양력면의 충돌 문제는 표면격자 내부에 들어간 와류고리의 포텐셜값을 제거하여 해결하였다. 제자리비행의 해석 시에 나타나는 와류 불안정성의 해결에는 slow starting과 vortex core growth 모델을 사용하였다. 로터 공력 해석 프로그램은 제자리비행과 전진비행에 대한 실험 결과와 비교하여 검증하였으며, 실험치와 일치하는 결과를 얻을 수 있었다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.1
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• pp.1-12
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• 2022

Wind tunnel test for a small scale electric ducted fan with a 104mm diameter was conducted to analyze the aerodynamic characteristics when it was used as a propulsion system of tilt-propeller UAV. Experimental conditions were derived from flight conditions of a sub-scaled OPPAV. Forces and moments of the ducted fan model were measured by a 6-axis balance and 3-dimensional wake vectors which could induce an aerodynamic influence in the vehicle were measured by 5-hole probes. Thrust and torque on hover and cruise conditions were measured and analyzed to drive out the operating conditions when it was applied in the sub-scaled OPPAV. On transition conditions, thrust keep its value with tilt angle variation below 40° and increase after that. But, sideforce increase constantly until 75°. The maximum axial velocity in the wake on hover and cruise conditions was around 60m/s and tangential velocity was around 12m/s. The position of the maximum axial velocity and vortex center move off the fan rotation center line as the tilt angle increases.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.10
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• pp.975-983
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• 2009

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 ($Re\;{\approx}3{\times}10^5$), as well as for verifying the test stand itself for acquiring hover performance.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.3
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• pp.215-223
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• 2009

In this paper, the helicopter aerodynamics is simulated in hovering and forward flight. Also, an overlapped grid technique is applied in this simulation to consider the blade motion and moving effects. The Caradonna & Tung's rotor blade was selected to analyze the unsteady aerodynamics in hovering and non-lift forward flight. Also, the AH-1G rotor blade was selected in forward flight. In forward flight case, the numerical trim was applied to determine the cyclic pitching angles using Newton-Raphson method, and the numerical results were in good agreement with experimental data, especially, the BVI effects were well simulated in advancing side in comparison other numerical results. The governing equation is a three dimensional unsteady Euler equation, and the Riemann invariants condition is used for inflow and outflow at the boundary.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.1
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• pp.59-67
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• 2018

In this paper, the test facility for coaxial propellers at low Reynolds developed and validated by measured data. The test equipment was designed to measure the hovering performance of propellers according to distances between the upper/lower propellers. Thrust, torque, rotational speed, vibration, and amperage of upper and lower propellers can be measured separately. The data acquisition system was built to collect signals of sensors, and LabVIEW software was used to control the motor and collect the signal. The hover performance tests of single propellers were preceded for the facility validation, and then the performance values of coaxial propellers were measured according to distances and diameter differences between the upper/lower propellers. The results showed that the high efficiency is achieved at 20%~30% distance between the upper propeller and lower one. The configuration that the upper propeller has shorter diameter than the lower one has the highest efficiency than other configuration.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.3
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• pp.243-250
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• 2012

In this paper, a systematic consequence of evaluation method, procedure, and flight data analysis is investigated for application of ADS-33E-PRF to UAV. And it is applied to unmanned rotorcraft for evaluation. CNUHELI-020, which is developed in Chungnam National University, is used for assessment of handling quality: decoupled longitudinal and lateral/directional model were used to assess handling qualities. Evaluation flight maneuvers are categorized as hover/low-speed requirements, small-amplitude attitude change, and moderate-amplitude attitude change requirements.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.11
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• pp.1073-1079
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• 2009

The proper orthogonal decomposition (POD) method can identify principal modes that optimally capture the energy content from large multi-dimensional data set. In this study unsteady pressure fields on the rotor blade surface of a helicopter in forward flight are expressed by a reduced order model based on the POD method. Special modes containing high energy are analyzed to investigate the aerodynamic characteristics in more efficient way. The CFD simulation of flowfields around helicopter rotor blade in hovering motion is also conducted to validate its prediction with experimental result. In the process 7 modes containing energy ratio 99% from 240 snapshots information are identified and utilized to construct a reduced order model.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.10
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• pp.833-844
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• 2018

This paper aims to predict the aerodynamic characteristics of individual rotor for the gust and flight conditions. Transformation procedure into the wind frame is conducted to analyze the gust. Hover, forward, and climb flight conditions of an individual rotor are analyzed using the blade element momentum theory (BEMT) considering the rigid blade flapping motion. XFOIL is used to derive aerodynamic results. Validation for hover, forward flight, and climb conditions are conducted using the present BEMT. In addition, a static experimental environment is constructed. The experimental results and the present BEMT are compared and verified.