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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

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

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

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

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

Pitching Moment Generation in an Insect-Mimicking Flapping-Wing System

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Journal of Bionic Engineering 2014年第1期11卷 36-51页

作者： Tri Quang Truong vu hoang phan Sanjay P. Sane Hoon Cheol Park Biomimetics and Intelligent Microsystem Laboratory & Artificial Muscle Research Center Konkuk University Seoul 143-70 l Korea Department of Advanced Technology Fusion Konkuk University Seoul 143-701 Korea National Centre for Biological Sciences Tata Institute of Fundamental Research Bangalore India

Unlike birds, insects lack control surfaces at the tail and hence most insects modify their wing kinematics to produce control forces or moments while flapping their wings. Change of the flapping angle range is one of the ways to modify wing kinematics, resulting in relocation of the mean Aerodynamic force Center （mean AC） and finally creating control moments. In an attempt to mimic this feature, we developed a flapping-wing system that generates a desired pitching moment during flap- ping-wing motion. The system comprises a flapping mechanism that creates a large and symmetric flapping motion in a pair of wings, a flapping angle change mechanism that modifies the flapping angle range, artificial wings, and a power source. From the measured wing kinematics, we have found that the flapping-wing system can properly modify the flapping angle ranges. The measured pitching moments show that the flapping-wing system generates a pitching moment in a desired direction by shifting the flapping angle range. We also demonstrated that the system can in practice change the longitudinal attitude by generating a nonzero pitching moment.

关键词： flapping-wing system pitching moment flapping angle unsteady blade element theory mean aerodynamic center,center of gravity

Structural Characteristics of Allomyrina Dichotoma Beetle＇s Hind Wings for Flapping Wing Micro Air Vehicle

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Journal of Bionic Engineering 2014年第2期11卷 226-235页

作者： Ngoc San Ha Quang Tri Truong hoang vu phan Nam Seo Goo Hoon Cheol Park Biomimetics and Intelligent Microsystem Laboratory Department of Advanced Technology Fusion Division of Interdisciplinary Studies Konkuk University Seoul 143-701 Republic of Korea

In this study, we present a complete structural analysis ofAllomyrina dichotoma beetle＇s hind wings by investigating their static and dynamic characteristics. The wing was subjected to the static loading to determine its overall flexural stiffness. Dy- namic characteristics such as natural frequency, mode shape, and damping ratio of vibration modes in the operating frequency range were determined using a Bruel ＆ Kjaer fast Fourier transform analyzer along with a laser sensor. The static and dynamic characteristics of natural Allomyrina dichotoma beetle＇s hind wings were compared to those of a fabricated artificial wing. The results indicate that natural frequencies of the natural wing were significantly correlated to the wing surface area density that was defined as the wing mass divided by the hind wing surface area. Moreover, the bending behaviors of the natural wing and artificial wing were similar to that of a cantilever beam. Furthermore, the flexural stiffness of the artificial wing was a little higher than that of the natural one whereas the natural frequency of the natural wing was close to that of the artificial wing. These results provide important information for the biomimetic design of insect-scale artificial wings, with which highly ma- neuverable and efficient micro air vehicles can be designed.

关键词： beetle hind wing flexural stiffness natural frequency mode shape Micro Air Vehicles (MAVs)

Stable Vertical Takeoff of an Insect-Mimicking Flapping-Wing System Without Guide Implementing Inherent Pitching Stability

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Journal of Bionic Engineering 2012年第4期9卷 391-401页

作者： hoang vu phan Quoc Viet Nguyen Quang Tri Truong Tien Van Truong Hoon Cheol Park Nam Seo Goo Doyoung Byun Min Jun Kim Department of Advanced Technology Fusion Konkuk University Seoul 143-701 Korea Department of Aerospace Engineering Konkuk University Seoul 143-701 Korea Department of Mechanical Engineering Sungkyunkwan University Seoul 143-701 Korea Department of Mechanical Engineering and Mechanics Drexel University Philadelphia USA

We briefly summarized how to design and fabricate an insect-mimicking flapping-wing system and demonstrate how to implement inherent pitching stability for stable vertical takeoff. The effect of relative locations of the Center of Gravity （CG） and the mean Aerodynamic Center （AC） on vertical flight was theoretically examined through static force balance considera- tion. We conducted a series of vertical takeoff tests in which the location of the mean AC was determined using an unsteady Blade Element Theory （BET） previously developed by the authors. Sequential images were captured during the takeoff tests using a high-speed camera. The results demonstrated that inherent pitching stability for vertical takeoff can be achieved by controlling the relative position between the CG and the mean AC of the flapping system.

关键词： beetle flapping-wing system insect-mimicking insect flight inherent pitching stability vertical takeoff

Hydrogen roles approaching ideal electrical and optical properties for undoped and Al doped ZnO thin films

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Journal of Materiomics 2022年第1期8卷 123-135页

作者： Dung Van hoang Nam hoang vu Nga Thi Do Anh Tuan Thanh Pham Truong Huu Nguyen Jer-Lai Kuo Thang Bach phan Vinh Cao Tran Laboratory of Advanced Materials University of ScienceHoChiMinh City700000Viet Nam Vietnam National University HoChiMinh City700000Viet Nam HoChiMinh City Institute of Physics HoChiMinh City700000Viet Nam Institute of Atomic and Molecular Sciences Academia SinicaTaipei10617Taiwan Center for Innovative Materials and Architectures(INOMAR) HoChiMinh City700000Viet Nam Faculty of Materials Science&Technology University of ScienceHoChiMinh City700000Viet Nam

This paper distinguished hydrogen roles to improve electron mobility and carrier concentration in ZnO and Al doped ZnO sputtered *** combining experimental evidences and theoretical results,we find out that hydrogen located at oxygen vacancy sites(H_(O))is the main factor gives rise to increase simultaneously mobility and carrier concentration which has not been mentioned *** appropriate hydrogen content during sputtering not only results in crystalline relaxation but also supports doping Al into ZnO,increasing carrier concentration and electron mobility in the *** principles calculations confirmed hydrogen substitutional stability for oxygen vacancy,significantly reducing electron conductivity effective mass and hence increasing electron *** particular,0.8%hydrogen partial pressure ratio achieved 61 cm^(2)V^(-1)s^(-1)maximum electron mobility,optical transmittance above 82%in visible and near-infrared regions,and 2×10^(20) cm^(-3)carrier concentrations for H-Al co-doped ZnO *** values approach ideal electrical and optical properties for transparent conducting oxide *** presence of one maximum electron mobility was attributed to competition between increasing mobility due to restoring effective electron mass and hydrogen passivation of native defects,and decreased electron mobility due to electron-phonon scattering.

关键词： High electron mobility Hydrogen roles Passivation effects Effective electron mass DFT calculations Doped ZnO thin Film

Robust exponential stability and stabilization of linear uncertain polytopic time-delay systems

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控制理论与应用（英文版） 2008年第2期6卷 163-170页

作者： Nam phan T. Phat vu N. Department of Mathematics Quynhon UniversityQuynhonBinhdinhVietnam Institute of Mathematics 18 Hoang Quoc Viet RoadHanoiVietnam

This paper proposes new sufficient conditions for the exponential stability and *** linear uncertain polytopic time-delay systems. The conditions for exponential stability are expressed in terms of Kharitonov-type linear matrix inequalities （LMIs） and we develop control design methods based on LMIs for solving stabilization problem. Our method consists of a combination of the LMI approach and the use of parameter-dependent Lyapunov functionals, which allows to compute simultaneously the two bounds that characterize the exponetial stability rate of the solution. Numerical examples illustrating the conditions are given.

关键词： Polytopic time-delay system Exponential stability Stabilization Parameter-dependent Lyapunov function Linear matrix inequalities