• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.43 no.9
• /
• pp.765-772
• /
• 2015

Aerodynamic force measurements and phase-locked PIV study were carried out to check the bio-mimetic MAV applicability of a swift flight. Two-rotational DOF robotic wing model and blowing-type wind tunnel were employed. The amplitude of twist angle were ${\pm}0$, ${\pm}5$, ${\pm}10$, and ${\pm}20$ deg. and stroke angles were manipulated by simple harmonic function with out-of-phase in regards to the stroke motion. It is acknowledged that the time-varying lift coefficients in accordance with the change of the twist angle did not result in any noticeable differences, just the small decrease and delay. However, the drag exhibited that the small change of the twist angle can produce large thrust. These findings imply why a swift uses small twist angle during flight. The PIV results displayed that the delay of aerodynamic forces is highly associated with the vortical structures around the wing. It is therefore indicated that a process of designing a swift-based Micro Air Vehicle should take the twist angle into consideration, as the essential parameter.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.40 no.8
• /
• pp.662-669
• /
• 2012

The effect of aspect ratio (AR) on the aerodynamic characteristics of a flapping wing was examined to analyze the design parameters of an insect-based MAV. The experimental model constructed with 4-bar linkages was operated in a water tank with the condition of a low Reynolds number. A water-proof micro-force load cell was fabricated and installed at the root of the wing which is made of a plexiglas. The wing shapes were based on the planform of a fruit fly wing. The ARs selected were 1.87, 3.74 and 7.48 and the Reynolds number was fixed at $10^4$. For AR=1.87 and 3.74, distinct lift peaks which indicate unsteady effects such as 'wake-capture' were observed at the moment of the start of the wing-stroke. However, for AR=7.48, no unsteady effects were observed. These phenomena were also observed in the delayed rotation case. The results indicate that a larger AR provides better aerodynamic performance for the insect-based flapping wing which can be applied in MAV designs.

• 한국전산유체공학회:학술대회논문집
• /
• 2010.05a
• /
• pp.32-36
• /
• 2010

This paper dealt with the flow simulation for the optimum designed propeller for Micro Aerial Vehicle, using a commercial CFD program(FLUENT). The propeller was modeled by the Multiple Reference Frame(MRF) method. For the validation of the computational method, the flow field analysis results for the propeller were compared with the flow analysis results, which are using Xfoil, for the optimum design, and with the wind tunnel data of a similar propeller model. By these validation processes, the reliability of MRF method was confirmed.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.39 no.10
• /
• pp.905-911
• /
• 2011

With the progress of micro actuator technology, studies on the development of micro air flapping wing vehicles are actively undergoing. In the present study, the changes of both lift and thrust characteristics of the wings are investigated using a boundary element method. Lift of the heaving wing is not generated when the wing is beating with smaller frequencies than 1 Hz. Thrust increases with amplitude and frequency. As the wing's taper and aspect ratios increase, both lift and thrust also increase. Results on the pitching oscillation and flapping motion will be included in the future work.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.32 no.8
• /
• pp.145-150
• /
• 2004

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.30 no.4
• /
• pp.289-296
• /
• 2017

In this paper, geometrical optimization for newly designed flapping mechanism for insect-like micro air vehicle is presented. The mechanism uses strings to convert rotation of motor to reciprocating wing motion to reduce the total weight and inertial force. The governing algorithm of movement of the mechanism is established considering the characteristic of string that only tensile force can be acted by string, to optimize the kinematics. Modified pattern search method which is complemented to avoid converging into local optimum is adopted to the geometrical optimization of the mechanism. Then, prototype of the optimized geometry is produced and experimented to check the feasibility of the mechanism and the optimization method. The results from optimization and experiment shows good agreement in flapping amplitude and other wing kinematics. Further research will be conducted on dynamic analysis of the mechanism and detailed specification of the prototype.

• The Science & Technology
• /
• v.34 no.12 s.391
• /
• pp.26-27
• /
• 2001

건국대 능동구조재료연구실은 1991년에 문을 열어 항공우주용 고성능 능동복합재료작동기 개발에 한창이다. 소형 무인항공기, 우주 구조물 및 로봇, 정비기기에 근육형 작동기 응용부품 및 서브시스템을 개발하여 적용함으로써 그 성능을 혁신적으로 향상시키는 것을 최종 목표로 하고 있다.

• Journal of Aerospace System Engineering
• /
• v.9 no.1
• /
• pp.7-11
• /
• 2015

최근 무인기와 초소형비행체를 위한 프로펠러 연구수요가 증가하고 있다. 일반적인 프로펠러와 다른 점은 저 레이놀즈수 유동조건에서 구동된다는 점이다. 본 연구는 저 레이놀즈수 유동조건에서 비행하는 인간 동력 항공기를 위한 프로펠러 공력설계 및 성능해석에 관한 연구다. 저 레이놀즈수 유동조건에서 발생하는 공력천이현상을 고려한 3차원 공력특성 변화를 정확히 반영하지 못하는 상용 프로그램의 단점을 보완하여 프로펠러 공력설계 및 성능해석이 가능한 프로그램을 개발했다. 개발된 프로그램으로 인간 동력 항공기 설계요구조건에 충족하는 프로펠러 공력설계 및 성능해석을 수행하였다. 또한 프로펠러 회전수와 장착각도 변화에 따른 성능변화를 예측하여 비행당시 상황에 따라 비행 가능한 성능출력이 가능하도록 하였다.

• Journal of Aerospace System Engineering
• /
• v.16 no.2
• /
• pp.63-72
• /
• 2022

As interest in microsatellites increases, research has been actively conducted recently on the performance and use, as well as the orbital design and deployment techniques, for the microsatellite constellations. The purpose of this study was to investigate orbital deployment techniques using thrust and differential atmospheric drag control (DADC) for the Walker-delta constellation. When using thrust, the time and thrust required for orbital deployment vary, depending on the separation speed and direction of the satellite with respect to the launch vehicle. A control strategy to complete the orbital deployment with limited performance of the propulsion system is suggested and it was analyzed. As a result, the relationship between the deployment period and the total thrust consumption was derived. It takes a relatively longer deployment time using differential air drag rather than consuming thrusts. It was verified that the satellites can be deployed only with differential air drag at a general orbit of a microsatellite constellation. The conclusion of this study suggests that the deployment strategy in this paper can be used for the microsatellite constellation.

• Journal of Space Technology and Applications
• /
• v.1 no.3
• /
• pp.319-336
• /
• 2021

This paper discusses the results of launch environment tests for the engineering qualification model (EQM) of nanosatellite Scale magNetospheric and Ionospheric Plasma Experiment (SNIPE) for scientific missions and lessons learned for the design of nanosatellites. SNIPE is a group of four formation-flying 6U nanosatellites with a range of payloads for missions including space weather measurement. We developed the EQM to verify the preliminary design prior to fabricating the flight model. Launch environment test of EQM was conducted for the first time in 2019, and all failures were corrected and verified at the second test conducted in 2021. A notable point of the two tests is that the nanosatellite deployer used in the first test is different from that of the second test. The second deployer has the capability to fix the internal satellite whereas the first deployer just contains and deploys the satellite. Thus actual mechanical loads the satellite receives is reduced for the second test compared to the first test. This work compares the mechanical responses of two tests and proposes general guidelines for structural design of nanosatellites.