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Influence of Center of Gravity Location on Flight Dynamic Stability in a Hovering Tailless FW-MAV: Lateral Motion

Journal of Bionic Engineering 2020年第1期17卷 148-160页

作者： Loan Thi Kim Au Hoon Cheol Park Department of Smart Vehicle Engineering and Artificial Muscle Research Center Konkuk UniversitySeoul 05029Korea

This paper reports the effect of the Center of Gravity(CG)position on lateral flight dynamic stability of hovering KUBeetle,a tailless FW-MAV,providing further insights on the effects of asymmetries in body mass distribution and wing kinematics.For the current study,the standard linearized equations of motion were applied as in the previous work on longitudinal dynamic stability.The stability derivatives were acquired using the computational fluid dynamic methods via the commercial software of ANSYS Fluent.There exists a stable region for CG between 2.6%and 3.5%of the mean chord below the wing pivot point,in which the lateral motion of hovering KUBeetle is passively stable.For CG below the stable region,because of an unstable oscillatory mode,the lateral motion of the FW-MAV is unstable but can be stabilized using rolling rate feedback.For CG above the stable region,because of a divergence mode,the system remains unstable even with the rolling rate feedback.Comparison with other works on an FW-MAV based on a quasi-steady aerodynamic model and on insect showed similar characteristics for flapping flight.It is also interesting to note that the asymmetries in body mass and wing kinematics can enlarge the stable region of the system by a non-zero Ixz which approaches the root square of√IxIz,a negative LrNp,and a positive Ix2(Ir+Np).Combining the current result with that of the previous work on longitudinal motion,the most beneficial region of the CG for full 6-DOF flight dynamic stability of hovering KUBeetle was suggested.

关键词： FW-MAV center of gravity flight dynamic stability lateral motion asymmetry computational fluid dynamics bioinspired flight

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Generation of Control Moments in an Insect-like Tailless Flapping-wing Micro Air Vehicle by Changing the Stroke-plane Angle

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Journal of Bionic Engineering 2016年第3期13卷 449-457页

作者： Hoang Vu Phan Hoon Cheol Park Artificial Muscle Research Center Konkuk University Seoul 143-701 South Korea Deptment of Advanced Technology Fusion Konkuk University Seoul 143-701 South Korea

We propose a control moment generator to control the attitude of an insect-like tailless Flapping-wing Micro Air Vehicle （FW-MAV）, where the flapping wings simultaneously produce the flight force and control moments. The generator tilts the stroke plane of each wing independently to direct the resultant aerodynamic force in the desired direction to ultimately generate pitch and yaw moments. A roll moment is produced by an additional mechanism that shifts the trailing edge, which changes the wing rotation angles of the two flapping wings and produces an asymmetric thrust. Images of the flapping wings are captured with a high-speed camera and clearly show that the FW-MAV can independently change the stroke planes of its two wings. The measured force and moment data prove that the control moment generator produces reasonable pitch and yaw moments by tilting the stroke plane and realizes a roll moment by shifting the position of the trailing edge at the wing root.

关键词： insect-like Flapping-wing Micro Air Vehicle （FW-MAV） control mechanism stroke plane beetle flight

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Longitudinal Flight Dynamic Analysis on Vertical Takeoff of a Tailless Flapping-Wing Micro Air Vehicle

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Journal of Bionic Engineering 2018年第2期15卷 283-297页

作者： Loan Thi Kim Au Vu Hoang Phan Hoon Cheol Park Department of Advanced Technology Fusion and Artificial Muscle Research Center Konkuk University Seou105029 Korea

This paper first analyzed the longitudinal dynamic behavior during vertical takeoff without control of a Flapping-Wing Micro Air Vehicle （FW-MAV）. The standard linear flight dynamics based on small disturbances from trim condition was not applicable for our analysis because the initial flight condition, which was at rest on the ground, could be such a large disturbance from the trim condition that the linearization is invalid. Therefore, we derived linearized Equations of Motion （EoM） which can treat an untrimmed flight condition as a reference for disturbances. The Computational Fluid Dynamic （CFD） software ANSYS Fluent was used to compute the aerodynamic forces and pitching moments. Three flight modes were found： a fast subsidence mode, a slow subsidence mode and a divergence oscil- latory mode. Due to divergence oscillatory mode, the deviation from the reference flight grew with time; the FW-MAV tumbled without control. The simulation showed for the first 0.5 second after leaving the ground （the time that is long enough for delay of feedback control）, the FW-MAV flew up to a height of 6 cm with small horizontal and pitching motion, which is close to a vertical flight.

关键词： bioinspired FW-MAV flight dynamics vertical takeoff CFD linear theory

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Comparison of Aerodynamic Forces and Moments Calculated by Three-dimensional Unsteady Blade Element Theory and Computational Fluid Dynamics

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Journal of Bionic Engineering 2017年第4期14卷 746-758页

作者： Loan Thi Kim Au Hoang Vu Phan Hoon Cheol Park Department of Advanced Technology Fusion and Artificial Muscle Research Center Konkuk University Seoul Korea

In previous work, we modified blade element theory by implementing three-dimensional wing kinematics and modeled the unsteady aerodynamic effects by adding the added mass and rotational forces. This method is referred to as Unsteady Blade Element Theory （UBET）. A comparison between UBET and Computational Fluid Dynamics （CFD） for flapping wings with high flapping frequencies （〉30 Hz） could not be found in literature survey. In this paper, UBET that considers the movement of pressure center in pitching-moment estimation was validated using the CFD method. We investigated three three-dimensional （3D） wing kinematics that produce negative, zero, and positive aerodynamic pitching moments. For all cases, the instantaneous aerodynamic forces and pitching moments estimated via UBET and CFD showed similar trends. The differences in average vertical forces and pitching moments about the center of gravity were about 10% and 12%, respectively. Therefore, UBET is proven to reasonably estimate the aerodynamic forces and pitching moment for flight dynamic study of FW-MAV. However, the differences in average wing drags and pitching moments about the feather axis were more than 20%. Since study of aerodynamic power requires reasonable estimation of wing drag and pitching moment about the feather axis, UBET needs further im- provement for hilzher accuracy.

关键词： blade element theory unsteady computational fluid dynamics flapping wings biomimetic

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Optimal Wing Rotation Angle by the Unsteady Blade Element Theory for Maximum Translational Force Generation in Insect-mimicking Flapping-wing Micro Air Vehicle

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Journal of Bionic Engineering 2016年第2期13卷 261-270页

作者： Loan Thi Kim Au Hoang Vu Phan Hoon Cheol Park Department of Advanced Technology Fusion Konkuk University Seoul 143-701 South Korea

This paper provides a parametric study to obtain the optimal wing rotation angle for the generation of maximum transla- tional force in an insect-mimicking Flapping-Wing Micro Air Vehicle （FWMAV） during hovering. The blade element theory and momentum theory were combined to obtain the equation from which the translational aerodynamic force could be esti- mated. This equation was converted into a non-dimensional form, so that the effect of normalized parameters on the thrust coefficient could be analyzed. The research showed that the thrust coefficient for a given wing section depends on two factors, the rotation angle of the wing section and the ratio of the chord to the travel distance of the wing section in one flapping cycle. For each ratio that we investigated, we could arrive at an optimal rotation angle corresponding to a maximum thrust coefficient. This study may be able to provide guidance for the FWMAV design.

关键词： FWMAV optimal rotation angle parametric study blade element theory momentum theory

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Design and Demonstration of Insect Mimicking Foldable Artificial Wing Using Four-Bar Linkage Systems

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Journal of Bionic Engineering 2014年第3期11卷 449-458页

作者： Quang-Tri Truong Byoma Wing Argyoganendro Hoon Cheol Park Laboratory of Applied Mechanics Faculty of Applied Science HCMUT Ho Chi Minh City 740-128 Vietnam Biomimetics and Intelligent Microsystem Laboratory Konkuk University Seoul 143-701 Korea Department of Advanced Technology Fusion Konkuk University Seoul 143-701 Korea Artificial Muscle Research Center Konkuk University Seoul 143-701 Korea

In this work, we develop an artificial foldable wing that mimics the hind wing of a beetle （Allomyrina dichotoma）. In real flight, the beetle unfolds forewings and hind wings, and maintains the unfolded configuration unless it is exhausted. The artificial wing has to be able to maintain a fully unfolded configuration while flapping at a desirable flapping frequency. The artificial foldable hind wing developed in this work is based on two four-bar linkages which adapt the behaviors of the beetle＇s hind wing. The four-bar-linkages are designed to mimic rotational motion of the wing base and the vein folding/unfolding motion of the beetle＇s hind wing. The behavior of the artificial wings, which are installed in a flapping-wing system, is observed using a high-speed camera. The observation shows that the wing could maintain a fully unfolded configuration during flapping motion. A series of thrust measurements are also conducted to estimate the force generated by the flapping-wing system with foldable artificial wings. Although the artificial foldable wings give added burden to the flapping-wing system because of its weight, the thrust measurement results show that the flapping-wing system could still generate reasonable thrust.

关键词： beetle＇s hind wing folding/unfolding motion flapping-wing system foldable wing four-bar linkage configuration thrust measurement

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Thrust Analysis of a Fish Robot Actuated by Piezoceramic Composite Actuators

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Journal of Bionic Engineering 2011年第2期8卷 158-164页

作者： Quang Sang Nguyen Hoon Cheol Park Doyoung Byun Biomimetics and bltelligent Microsystems Laboratory Department of Advanced Technology Fusion Konkuk University Seoul 143-701 South Korea Department of Advanced Technology Fusion Konkuk University Seoul 143-701 South Korea Department of Aerospace Engineering Konkuk University Seoul 143-701 South Korea

In this work, a three-dimensional （3D） Computational Fluid Dynamics （CFD） model was built to simulate the tail fin motion of a fish robot actuated by a piezoceramic composite actuator, and to determine the maximum thrust tail-beat frequency. A simulation of the tail fin at a tail-beat frequency was performed to confirm measured thrust data from a previous study. The computed and measured thrusts were in good agreement. A series of thrust simulations were conducted for various tail-beat frequencies to confirm the maximum thrust frequency that was obtained from thrust measurements in the previous study. The largest thrust was calculated at a tail-beat frequency of 3.7 Hz and vortices around the tail were fully separated. The calculated maximum thrust tail-beat frequency was in good agreement with the measured frequency. Flow characteristics during tail fin motion were examined to explain why the largest thrust occurred at this particular tail-beat frequency.

关键词： fish robot CFD LIPCA thrust measurement thrust analysis composite actuator vortex shedding

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Influence of Center of Gravity Location on Flight Dynamic Stability in a Hovering Tailless FW-MAV:Longitudinal Motion

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Journal of Bionic Engineering 2019年第1期16卷 130-144页

作者： Loan Thi Kim Au Hoon Cheol Park Department of Smart Vehicle Engineering and Artificial Muscle Research Center Konkuk UniversitySeou105029Korea

The influence of Center of Gravity(CG)location on longitudinal dynamic stability of hovering KUBeetle,a tailless Flapping-Wing Micro Air Vehicle(FW-MAV),is reported in this paper.The rigid-body approximation was assumed,allowing application of the standard equations of motion used for fixed-wing aircraft.For each considered location of CG,stability derivatives were obtained using the computational fluid dynamics method via the commercial software of ANSYS Fluent.The dynamic stability was studied using technique of eigenvalue analysis.There exists a narrow stable region for CG between 23%-24%of mean chord above the wing pivot point,where the longitudinal hovering of KUBeetle is passively stable.When CG is located below the stable region,the analysis identifies two subsidence modes and one unstable oscillatory mode,which makes the hovering of KUBeetle unstable.However,it can be stabilized using pitching rate feedback.When CG is located above the stable region,the system yields one stable oscillatory mode,one subsidence mode,and one divergence mode.Because of the divergence mode,the system remains unstable even with the angular rate feedback.These results share similar characteristics to another FW-MAV and insects.This study may provide a reference for FW-MAV developers.

关键词： center of gravity hovering longitudinal dynamic stability computational fluid dynamics flapping wings bioinspired flight

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Design and Demonstration of a Locust-Like Jumping Mechanism for Small-Scale Robots

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Journal of Bionic Engineering 2012年第3期9卷 271-281页

作者： Quoc-Viet Nguyen Hoon Cheol Park Department of Advanced Technology Fusion Konkuk University Seoul 143-701 Republic of Korea

A jumping mechanism can be an efficient mode of motion for small robots to overcome large obstacles on the ground and rough terrain. In this paper, we present a 7 g prototype of locust-inspired jumping mechanism that uses springs, wire, reduction gears, and a motor as the actuation components. The leg structure and muscles of a locust or grasshopper were mimicked using springs and wire, springs for passive extensor muscles, and a wire as a flexor muscle. A small motor was used to slowly charge the spring through a lever and gear system, and a cam with a special profile was used as a clicking mechanism for quick release of elastic energy stored in the springs to create a sudden kick for a quick jump. Performance analysis and experiments were conducted for comparison and performance estimation of the jumping mechanism prototype. Our prototype could produce standing jumps over obstacles that were about 14 times its own size （approximate to 71 cm） and a jumping distance of 20 times its own size （approximate to 100 cm）.

关键词： biomimetics locust jumping mechanism passive tibia extensor muscle

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Effect of Wing Kinematics Modulation on Aerodynamic Force Generation in Hovering Insect-mimicking Flapping-wing Micro Air Vehicle

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Journal of Bionic Engineering 2015年第4期12卷 539-554页

作者： Hoang Vu Phan Quang Tri Truong Thi Kim Loan Au Hoon Cheol Park Artificial Muscle Research Center Konkuk University Seoul 143-701 South Korea National Research Laboratory for Biomimetics and Intelligent Microsystems Konkuk University Seoul 143-701 South Korea Department of Advanced Technology Fusion Konkuk University Seoul 143-701 South Korea Laboratory of Applied Mechanics Faculty of Applied Science Ho Chi Minh City University of Technology Ho Chi Minh 740-128 Vietnam

We investigated the effect of wing kinematics modulation, which was achieved by adjusting the location of trailing-edge constraint at the wing-root, i.e., by adjusting the wing-root offset, on the generation of aerodynamic forces in a hovering in- sect-mimicking Flapping-Wing Micro Air Vehicle （FW-MAV） by numerical and experimental studies. Three-dimensional wing kinematics measured using three synchronized high-speed cameras revealed a clear difference in the wing rotation angle of a wing section for different wing-root offsets. The extrapolated wing kinematics were in good agreement with the measured ones for various wing-root offsets. The Unsteady Blade Element Theory （UBET） was used to estimate the forces generated by the flapping wings and validated by comparison with results of measurements performed using a load cell. Although the thrust produced by a flapping wing with a wing-root offset of 0.20 c was about 4% less, its force-to-input-power ratio was about 30% and 10% higher than those with the offsets of 0.10 c and 0.15 c, respectively. This result could be explained by analyzing the effective Angle of Attack （AoA） and the force components computed by the UBET. Thus, a flapping wing with a wing-root offset of 0.20 c can be regarded as an optimal twist configuration for the development of the FW-MAV.

关键词： wing kinematics flapping-wing MAV biomimetics beetle-mimicking insect flight linear extrapolation

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