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1 – 10 of 268Adnan Maqsood and Tiauw Hiong Go
The purpose of this paper is to describe the research performed on flexible-wing micro air vehicle (MAV). Typical attributes associated with the aerodynamics of MAVs are low…
Abstract
Purpose
The purpose of this paper is to describe the research performed on flexible-wing micro air vehicle (MAV). Typical attributes associated with the aerodynamics of MAVs are low Reynolds number, low altitude flying environments and low aspect ratio platforms. These attributes give birth to several challenges such as poor aerodynamic performance, nonlinear lift patterns and reduced gust tolerance. Flexible-wing MAV is renowned for improved aerodynamic characteristics such as smooth flight in gusty conditions than its rigid-wing counterpart.
Design/methodology/approach
The wind-tunnel experiments are carried out for various configurations to determine the ways of further enhancing lift. The baseline geometric description for all MAVs includes 15-cm box dimension and an aspect ratio of 1. The experimental results of the baseline configuration are compared with other experimental results available in literature. After due validation, the effects of following parameters are quantized and compared with the rigid-wing counterpart: underlying skeleton; wing membrane extension; wing membrane relaxation; and wing membrane material (latex, silk, poly-vinyl chloride plastic sheet and nylon).
Findings
It is found that the skeleton layout significantly governs the lift characteristics. The effect of membrane extension and relaxation proved to be of little advantage. Latex sheets are found to be the best choice for membrane material. The aerodynamic assessment at low Reynolds number has demonstrated significant improvement of lift characteristics for flexible wings over rigid-wing counterparts.
Research limitations/implications
The results presented in this paper are based on wind-tunnel experimentation. Further experimentation through flight test may be needed to reveal the true aerodynamic performance under unsteady maneuvers.
Practical implications
The material properties vary significantly during fabrication. A technique to standardize the properties of flexible membranes is a missing link in literature and warrants further investigation.
Originality/value
This concept of flexible wing has shown high potential. The primary objective of this paper is to experimentally investigate ways of further enhancing the lift of flexible-wing MAVs by controlling flexibility passively. While various researchers have spent many years on developing the optimum wing frame for the flexible wing, research on different wing materials has been limited. This is the first paper of its kind covering all aspects of wing-frame design, material, effects of extension and relaxation on wing membrane.
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Mustafa Serdar Genç, Hacımurat Demir, Mustafa Özden and Tuna Murat Bodur
The purpose of this exhaustive experimental study is to investigate the fluid-structure interaction in the flexible membrane wings over a range of angles of attack for various…
Abstract
Purpose
The purpose of this exhaustive experimental study is to investigate the fluid-structure interaction in the flexible membrane wings over a range of angles of attack for various Reynolds numbers.
Design/methodology/approach
In this paper, an experimental study on fluid-structure interaction of flexible membrane wings was presented at Reynolds numbers of 2.5 × 104, 5 × 104 and 7.5 × 104. In the experimental studies, flow visualization, velocity and deformation measurements for flexible membrane wings were performed by the smoke-wire technique, multichannel constant temperature anemometer and digital image correlation system, respectively. All experimental results were combined and fluid-structure interaction was discussed.
Findings
In the flexible wings with the higher aspect ratio, higher vibration modes were noticed because the leading-edge separation was dominant at lower angles of attack. As both Reynolds number and the aspect ratio increased, the maximum membrane deformations increased and the vibrations became visible, secondary vibration modes were observed with growing the leading-edge vortices at moderate angles of attack. Moreover, in the graphs of the spectral analysis of the membrane displacement and the velocity; the dominant frequencies coincided because of the interaction of the flow over the wings and the membrane deformations.
Originality/value
Unlike available literature, obtained results were presented comparatively using the sketches of the smoke-wire photographs with deformation measurement or turbulence statistics from the velocity measurements. In this study, fluid-structure interaction and leading-edge vortices of membrane wings were investigated in detail with increasing both Reynolds number and the aspect ratio.
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Syam Narayanan S. and Asad Ahmed R.
The purpose of this study is to experimentally analyse the effect of flexible and stiffened membrane wings in the lift generation of flapping micro air vehicle (MAV).
Abstract
Purpose
The purpose of this study is to experimentally analyse the effect of flexible and stiffened membrane wings in the lift generation of flapping micro air vehicle (MAV).
Design/methodology/approach
This is analysed by the rectangle wing made up of polyethylene terephthalate sheets of 100 microns. MAV is tested for the free stream velocity of 2 m/s, 4 m/s, 6 m/s and k* of 0, 0.25, 1, 3, 8. This test is repeated for flapping MAV of the free flapping frequency of 2 Hz, 4 Hz, 6 Hz, 10 Hz and 12 Hz.
Findings
This study shows that the membrane wing with proper stiffeners can give better lift generation capacity than a flexible wing.
Research limitations/implications
Only a normal force component is measured, which is perpendicular to the longitudinal axis of the model.
Practical implications
In MAVs, the wing structures are thin and light, so the effect of fluid-structure interactions is important at low Reynold’s numbers. This data are useful for the MAV developments.
Originality/value
The effect of chord-wise flexibility in lift generation is the study of the effect of a flexible wing and rigid wing in MAV. It is analysed by the rectangle wing. The coefficient of normal force at different free stream conditions was analysed.
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Syam Narayanan S., Asad Ahmed R., Jijo Philip Varghese, Gopinath S., Jedidiah Paulraj and Muthukumar M.
The purpose of this paper is to experimentally analyze the effect of wing shape of various insects of different species in a flapping micro aerial vehicle (MAV).
Abstract
Purpose
The purpose of this paper is to experimentally analyze the effect of wing shape of various insects of different species in a flapping micro aerial vehicle (MAV).
Design/methodology/approach
Six different wings are fabricated for the MAV configuration, which is restricted to the size of 15 cm length and width; all wings have different surface area and constant span length of 6 cm. The force is being measured with the help of a force-sensing resistor (FSR), and the coefficients of lift were calculated and compared.
Findings
This study shows that the wing “Tipula sp” has better value of lift than other insect wings, except for the negative angle of attacks. The wing “Aeshna multicolor” gives the better values of lift in negative angles of attack.
Practical implications
This paper lays the foundation for the development of flapping MAVs with the insect wings. This type of wing can be used for spying purpose in the military zone and also can be used to survey remote and dangerous places where humans cannot enter.
Originality/value
This paper covers all basic insect wing configurations of different species with exact mimics of the veins. As the experimental investigation was carried for different angle of attacks, velocities and flapping frequencies, this paper can be used as reference for future flapping wing MAV developers.
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Hoang Vu Phan, Quang-Tri Truong and Hoon-Cheol Park
The purpose of this paper is to demonstrate the uncontrolled vertical takeoff of an insect-mimicking flapping-wing micro air vehicle (FW-MAV) of 12.5 cm wing span with a body…
Abstract
Purpose
The purpose of this paper is to demonstrate the uncontrolled vertical takeoff of an insect-mimicking flapping-wing micro air vehicle (FW-MAV) of 12.5 cm wing span with a body weight of 7.36 g after installing batteries and power control.
Design/methodology/approach
The forces were measured using a load cell and estimated by the unsteady blade element theory (UBET), which is based on full three-dimensional wing kinematics. In addition, the mean aerodynamic force center (AC) was determined based on the UBET calculations using the measured wing kinematics.
Findings
The wing flapping frequency can reach to 43 Hz at the flapping angle of 150°. By flapping wings at a frequency of 34 Hz, the FW-MAV can produce enough thrust to over its own weight. For this condition, the difference between the estimated and average measured vertical forces was about 7.3 percent with respect to the estimated force. All parts for the FW-MAV were integrated such that the distance between the mean AC and the center of gravity is close to zero. In this manner, pitching moment generation was prevented to facilitate stable vertical takeoff. An uncontrolled takeoff test successfully demonstrated that the FW-MAV possesses initial pitching stability for takeoff.
Originality/value
This work has successfully demonstrated an insect-mimicking flapping-wing MAV that can stably takeoff with initial stability.
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Zihao Chen, Weiping Zhang, Jiawang Mou and Kexin Zheng
Vertical take-off is commonly adopted in most insect-mimicking flapping-wing micro air vehicles (FMAV) while insects also adopt horizontal take-off from the ground. The purpose of…
Abstract
Purpose
Vertical take-off is commonly adopted in most insect-mimicking flapping-wing micro air vehicles (FMAV) while insects also adopt horizontal take-off from the ground. The purpose of this paper is to study how insects adjust their attitude in such a short time during horizontal take-off by means of designing and testing an FMAV based on stroke plane modulation.
Design/methodology/approach
An FMAV prototype based on stroke plane rotating modulation is built to test the flight performance during horizontal take-off. Dynamic gain and decoupling mixer is added to compensate for the nonlinearity during the rotation angle of the stroke plane getting too large at the beginning of take-off. Force/torque test based on a six-axis sensor validates the change of aerodynamic force and torque at different rotation angles. High-speed camera and motion capture system test the flight performance of horizontal take-off.
Findings
Stroke plane modulation can provide a great initial pitch toque for FMAV to realize horizontal take-off. But the large range of rotation angles causes nonlinearity and coupling of roll and yaw. A dynamic gain and a mixer are added in the controller, and the FMAV successfully achieves horizontally taking off in less than 1 s.
Originality/value
The research in this paper shows stroke plane modulation is suitable for insect’s horizontal take-off
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Joydeep Bhowmik, Debopam Das and Saurav Kumar Ghosh
The purpose of the work is to design a flapping wing that generates net positive propulsive force and vertical force over a flapping cycle operating at a given freestream…
Abstract
Purpose
The purpose of the work is to design a flapping wing that generates net positive propulsive force and vertical force over a flapping cycle operating at a given freestream velocity. In addition, an optimal wing is designed based on the comparison of the force estimated from the quasi‐steady theory, with the wind‐tunnel experiments. Based on the designed wing configuration, a flapping wing ornithopter is fabricated.
Design/methodology/approach
This paper presents a theoretical aerodynamic model of the design of an ornithopter with specific twist distribution that results generation of substantial net positive vertical force and thrust over a cycle at non‐zero advance ratio. The wing has a specific but different twist distribution during the downstroke and the upstroke that maintains the designed angle of attack during the strokes. The wing is divided into spanwise strips and Prandtl's lifting line theory is applied to estimate aerodynamic forces with the assumptions of quasi‐steady flow and the wings are without any dihedral or anhedral. Spanwise circulation distribution is obtained and hence lift is calculated. The lift is resolved along the freestream velocity and perpendicular to the freestream velocity to obtain vertical force and propulsive thrust force. Experiments are performed in a wind tunnel to find the forces generated in a flapping cycle which compares well with the theoretical estimation at low flying speeds.
Findings
The estimated aerodynamic force indicates whether the wing geometry and operating conditions are sufficient to carry the weight of the vehicle for a sustainable flight. The variation of the aerodynamic forces with varying flapping frequencies and freestream velocities has been illustrated and compared with experimental data that shows a reasonable match with the theoretical estimations. Based on the calculations a prototype has been fabricated and successfully flown.
Research limitations/implications
The theory does not take into account the unsteady effects and estimates the aerodynamic forces at wing level condition. It doesn’t predict stall and ignores structural deformations due to aerodynamic loads. The airfoil section is only specified by the chord, zero lift angle of attack, lift slope, profile drag coefficient and angle of attack as given inputs. To fabricate a light weight wing that maintains a very accurate geometric twist and camber distribution as per the theoretical requirement is challenging.
Practical implications
Useful for designing ornithopter wing (preferably bigger) involving an unswept rigid spar with flapping and twisting.
Originality/value
The novelty of the present wing design is the appropriate spanwise geometric twisting about the leading edge spar.
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Jih‐Lung Lin, Chin‐Yi Wei and Chi‐Yu Lin
This study aims to design and test some fixed‐wing micro aerial vehicles (MAV).
Abstract
Purpose
This study aims to design and test some fixed‐wing micro aerial vehicles (MAV).
Design/methodology/approach
The MAV wing planform in this study was designed based on previous results and the need to reduce the weight of the MAV. The MAV had a wing planform with a 6 percent Gottingen‐329 camber airfoil, a 20° swept‐back leading edge and a straight trailing edge. The fuselage was designed to contain a motor, an electronic control system and a video camera with a built‐in transmitter. The battery was located outside the fuselage to trim the center of gravity and enable the battery to be changed easily when it has run out. Two exaggerated vertical stabilizers were installed to prevent the MAV from rolling. The materials, the power plant and the electronics used to fabricate the MAV herein were either the lightest or the smallest from that could be obtained off‐the‐shelf. Since, MAVs should be expendable, the cost was kept under US$250 (including the cost of an onboard video camera system, which costs US$170).
Findings
Flight tests were performed following fabrication. The MAV was launched by hand, flew within a radius of 30 ∼ 50 m, and eventually glided to a grassy ground. The flight was stable and the quality of the downlink video was acceptable for surveillance purpose. The MAVs presented in this work were proven to have successful designs.
Originality/value
MAVs were successfully designed herein based on previous results. The materials and the fabrication processes were carefully selected and tested, to keep the mass of a flyable MAV under 65 g, while ensuring it has sufficient structural strength. The cost was reduced to US$250, making the MAV truly expendable.
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A bibliographical review of the finite element methods (FEMs) applied for the linear and nonlinear, static and dynamic analyses of basic structural elements from the theoretical…
Abstract
A bibliographical review of the finite element methods (FEMs) applied for the linear and nonlinear, static and dynamic analyses of basic structural elements from the theoretical as well as practical points of view is given. The bibliography at the end of the paper contains 1,726 references to papers, conference proceedings and theses/dissertations dealing with the analysis of beams, columns, rods, bars, cables, discs, blades, shafts, membranes, plates and shells that were published in 1996‐1999.
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Mostafa Arasteh, Yegane Azargoon and M.H. Djavareshkian
Ground effect is one of the important factors in the enhancement of wing aerodynamic performance. This study aims to investigate the aerodynamic forces and performance of a…
Abstract
Purpose
Ground effect is one of the important factors in the enhancement of wing aerodynamic performance. This study aims to investigate the aerodynamic forces and performance of a flapping wing with the bending deflection angel under the ground effect.
Design/methodology/approach
In this study, the wing and flapping mechanism were designed and manufactured based on the seagull flight and then assembled. It is worth noting that this mechanism is capable of wing bending in the upstroke flight as big birds. Finally, the model was examined at bending deflection angles of 0° and 107° and different distances from the surface, flapping frequencies and velocities in forward flight in a wind tunnel.
Findings
The results revealed that the aerodynamic performance of flapping wings in forward flight improved due to the ground effect. The effect of the bending deflection mechanism on lift generation was escalated when the flapping wing was close to the surface, where the maximum power loading occurred.
Practical implications
Flapping wings have many different applications, such as maintenance, traffic control, pollution monitoring, meteorology and high-risk operations. Unlike fixed-wing micro aerial vehicles, flapping wings are capable of operating in very-low Reynolds-number flow regimes. On the other hand, ground effect poses positive impacts on the provision of aerodynamic forces in the take-off process.
Originality/value
Bending deflection in the flapping motion and ground effect are two influential factors in the enhancement of the aerodynamic performance of flapping wings. The combined effects of these two factors have not been studied yet, which is addressed in this study.
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