AIAA-2010-1018

American Institute of Aeronautics and Astronautics

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Development of Flapping Wing Micro Air Vehicles -Design, CFD, Experiment and Actual Flight

Cheng-Kuei Hsu1, James Evans2, Sunil Vytla3 and P. G. Huang4 Wright State University, Dayton, Ohio, 45435-00001

In the paper, we discuss an approach we used to design flapping wing Micro Air Vehicles (MAV). The approach makes use of the conventional precision machining methods, such as Rapid Prototyping 3D printing, Electrical Discharge Machining and Laser Micromachining techniques, to manufacture the MAV parts. The current generation of MAV’s has a total weight of 10.8 grams (12.56 grams with one Camera) and a span of 20 cm and it can achieve a payload of around 3 grams. The MAV’s not only are capable of performing simple acrobatic maneuver in the air but also can hover in place with very little drift. We are in the process of redesigning the next generation of MAV’s, which not only offer a reduction in size but also make use of vision-based tracking technique to perform obstacle-avoidance flight adjustments.

Nomenclature P = a given point Pl = a pixel captured by left camera, the projection of P Pr = a pixel captured by right camera, the projection of P Fl = focal point Fr = focal point El = intersection between left image plane and the line of focal points Er = intersection between right image plane and the line of focal points I = image d = displacement

I. Introduction The development of UAV/MAV has become increasingly important due to the recent successes of UAV in both

military and civilian uses. To name a few, US military UAV’s from all services logged nearly 400,000 hours in 2008, not counting “man-portable” aircraft and the US Custom and Border Protection Agency has employed more than 200 UAV’s for border patrol. Although the deployment of UAV has been very successful, it was not designed to fly in the urban and in-door environments. As the terrorism will be the main focus of the future warfare, the intelligence, surveillance and reconnaissance mission will most likely be executed in an in-door or urban environment. For various military applications, the US Air Force has set forth a goal of deploying a bird-sized MAV by 2015 and insect size versions by 2030. The MAV potentially has a variety of civilian as well as military uses too difficult or dangerous for humans, from searching buildings or caves for terrorists to probing damaged nuclear power plants for radiation leaks or collapsed mine shafts for survivors.

The small scale of such vehicles poses a need for a dramatic change in the air vehicle design paradigm, one as great as that faced by the Wright Brothers in which they identified that control was the missing link in a workable aircraft. This new paradigm is simultaneous multi-disciplinary design of integrated multi-functional components and systems. This new paradigm is simultaneous multi-disciplinary design of integrated multi-functional components and systems. This small scale no longer affords the luxury of separately designing thrust, control, lift, actuation and sensing with subsequent integration and adjustment of designs. For example, because the eddy created by the

1 Postdoctoral researcher, Department of Mechanical and materials Engineering, [email protected]. 2 Ph. D. student, Department of Mechanical and materials Engineering, [email protected] 3 Ph. D. student, Department of Mechanical and materials Engineering, [email protected] 4 Professor and chair, Department of Mechanical and materials Engineering, [email protected]

48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition4 - 7 January 2010, Orlando, Florida

AIAA 2010-1018

Copyright © 2010 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.


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dynamic flapping wings is as large as the vehicle itself, the exact full body shape becomes crucial to the aerodynamic design of MAV's. This is the most fundamental difference between the design of MAV's and that of the large fixed wing aircraft, in which the flow is mainly dominant by the 2-D airfoil shape and wind tunnel testing can be conducted with a simplified geometry under steady-state conditions.

MAV work has been populated since early ’90. A comprehensive review of the MAV activities can be seen in the book by Mueller et al1. Pornsin-sirirak et al.2 created Caltech’s “Micro-Bat” with a 6-min flight record of flapping MAVs using MEMS process and the titanium-parylene material in 2001. Barrett et al.3 announced the successful hovering of TU Delft’s “Delfly” composed of a pair of dragonfly-like flexible wings in 2005. The team also developed in 2008 the smallest ornithopter fitted with a camera, the Delfly Micro4. Although this version measures 10 cm and weighs 3 grams, it still requires some work in flying outdoor. Jones et al.5 of Naval Graduate School of US made a fixed-wing type MAV with a scissor-like clapping tail thruster in 2005. Banala et al.6 at Delaware University employed a 5-bar mechanism for generating a prescribed wing motion taken from a hawk moth kinematic flight data in 2005. McIntosh et al.7 designed a mechanism for biaxial rotation of a wing for a hovering MAV in 2006. Robert Wood8 at Harvard University developed the smallest ornithopter, at just 3 cm, but this craft is flying between the guided poles and it gets its power through a wire.

II. Aerodynamics Considerations Our understanding of the fundamental flight aerodynamics for MAV is limited. Traditional fixed wing flight

concepts begin to fail as the dynamics enter a regime of bird-sized flights. MAV’s typically operate at a Reynolds number range of about 5,000 to about 200,000. Flow transition to turbulence often occurs within this Reynolds number range and very little information on the performance of various airfoil shapes (wings) exits within this flight regime. Due to its lightweight and thus its being very sensitive to external wind (or temperature gradients) conditions, MAV must be designed to maneuver quickly to adjust its flow trajectory so that the vehicle can maintain its stability. As a result, there is almost no “cruising” period and hence using the assumption of a steady state aerodynamics condition to design an MAV may not be appropriate. If one is to consider flapping wing vehicles, as selected by the nature evolution (interestingly, propeller was never used and the jet propulsion was only restricted to sea animals), the aeroelastic of the wing design must also be taken in account. Compounded with the complexity of geometry, the multi-objective design of such a vehicle may be a formidable task.

The approach often used is a combination of the observation of the nature by bio-mimicking of a small bird’s or an insect’s aerodynamics, and CFD and/or wind tunnel (or wind house) testing of the flight mechanics with full body scale. Figure 1 shows a 3-D high speed camera setup to study the kinematics of the wing flapping of a dragon fly. The wing kinematics is then reconstructed by computer and a CAD/CAM model is built, as shown in figure 2(a). CFD of model is then used to extract useful information, such as shown in Figure 2(b)-(d)9.

Figure 1. Study of the wing kinematics of a dragon fly using a 3-D high speed camera.


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Figure 2. CAD model of the dragon fly and its CFD study.

III. Design and Manufacturing Regarding design and manufacturing, we followed the current technology in precision machinery, such as Multi-

Jet Modeling (MJM) rapid prototyping machining, Electric Discharge Machining (EDM) and Laser Micromachining (LM) technologies. The MJM rapid prototyping machine we used is capable printing 656 x 656 x 800 DPI in x, y and z direction with accuracy of 0.025 to 0.0035 mm of resolution. Once the CAD/CAM drawing is available, plastic gears and supporting parts can be printed directly from the RP machine in around 2-4 hours, as shown in Figure 3(a). The wax support can be used (and removed for finished parts) to produce gears and their supporting system in one piece to avoid slip between the gears, shown in Figure 3(b). The material we used is the proprietary EX200 UV curable acrylic plastic designed to provide fine features, sharp edges and smooth curves in 3-D printing.

Figure 3. Rapid prototype manufacturing of MAV parts.

The EDM is used to produce metal parts such as gear-and-motor holder, gear cam and links. The wire for the EDM we used has a diameter of 0.102 mm with a positioning accuracy of ±0.00254 mm. Figure 4 shows the finishing aluminum-alloy 7075 parts produced by using the wire EDM: (a) is the gear-and-motor holder, (b) is the gear cam and (c) and (d) are the gear links. Typically, a product can be cut in less than 1-3 hour directly from the CAD/CAM drawing. It should be noted that the EDM technology using a wire diameter of 0.02 mm and a position accuracy of ±1µm is now possible and it may used to prepare a part with radii of 0.015 mm.


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Figure 4. Finishing MAV parts using wire EDM.

Laser micromachining we used includes a variety of processes including hole drilling, ablation, milling, cutting and surface texturing. We use solid-state laser technology combined with multi-axis work stations and through-axis cameras to offer a fully integrated micromachining capability. This equipment uses CAD drawings to direct-write the customer required geometry. The Laser Micromachining can produces features as small as 15 microns in a very wide variety of materials including metals, ceramics, polymers, and composites.

As an example of what might be achieved with laser micromachining, we have produced artificial wings based on natural insect wings, as illustrated in Figure 5. White light interferometry was used to gather data on the 3-dimensional shape of a natural housefly wing. AutoCAD was then used to translate this data directly into laser micromachining commands that reproduced the shape in a polymer (Kapton). The finished replica has a length of 8.5 mm (identical to the natural wing), with thickness ranging from 40 to 80 microns, the “veins” of the wing being the thicker regions. The entire wing is machined in ~15 seconds, and can be cut from metals or composites in addition to polymers.

Figure 5. Laser machining of an artificial wing.

The gears shown in Figure 6 are made out of polyimide and stainless steel, although the same features could be achieved in a wide variety of materials. With the Laser machining technology we are ready to produce gear as small as 2 mm. Figure 7 shows the stages of producing a miniature motor and gear case, in which the individual parts were designed in CAD/CAM and fabricated via laser microcutting of titanium. The components were then laser welded to complete the assembly, in a turnaround time of 2 days. The assembly has an overall size of 22 × 22 × 4 mm and weighs only 0.45 g.

Figure 6. Laser machined miniature gears: (a) 15 mm diameter polyimide gear, (b) 2 mm diameter stainless steel gear.


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Figure 7. Miniature assemblies and welding: (a) 3D drawing of assembly, (b) finished assembly, (c) detail of laser-welded joints.

In this study, we propose a novel design of the three-way clap and fling mechanism, as shown in Figure 8. Within one flapping period, the clap and fling motion was observed not only in left and right sides, but also exists on the upper side of the wings. Other MAV’s, such as i-Bird 7 and Delfly-II 8 also used the four wing mechanism but did not seem to provide a full upper clap and fling motion. As will be demonstrated in this paper, the upper clap and fling motion not only provides a wider flapping motion of the wings but also gives rise to a stronger forward motion of the vehicle as compared to that without the full upper motion.

Figure 8. The transmission model and the final designs.

The wing span of the MAV is 20 cm and its surface is covered with a thin polyester (PET) film with a thickness of 25 µm. The PET film is glued directly to the spar and rib rods with a double-sized adhesive tape. It was found that this simple approach is sufficiently strong enough to withstand the highest frequency (20 Hz) of flapping motion without encountering any difficulty. To provide additional strength to the wings, a trapezoid tape was layered along the leading edge to enhance the stiffness of the film near the area. In the current design, the motor was power by a commercial poly-lithium battery of 30 or 90 mAh.

The total weight of the MAV including camera and battery is 12.56 gram. Table 1 shows the breakdown of the weight for each component.

Table 1. Breakdown of the weight for each component of the MAV with camera. No. Item Weight (g) No. Item Weight (g) 1 3-channel receiver 0.95 7 Tail 1.22 2 Actuator 0.98 8 Wings 1.05 3 Motor 2.80 9 2 Drive Gears 0.30 4 Frame 0.24 10 Drive Links 0.25 5 Battery (3.7v 30mAh) 1.25 11 Tape, Glue, Carbon Frame 1.00 6 Camera 1.85 12 Camera Battery 0.67

Total Weight 12.56 g

IV. Wind tunnel testing In the wind tunnel test, the 4-link flapping wing mechanism is mounted on a 6 degree of freedom (DoF) force

transducer; the dimensions of wind tunnel test section is 60 cm × 60 cm × 600 cm, as shown in Figure 9. The force transducer is capable of measuring the unsteady aerodynamic force and momentum generated from the flapping wing in the order 1 N and 7 N-m, respectively, in all three directions with a maximum error 0.2%.


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Figure 9. Wind tunnel test system: (a) 6-DoF load cell , (b) wind tunnel.

Since the MAV we have developed is small enough to fit into the test section of the wind tunnel, we are able to conduct the experiments in full scale, as shown in the flow visualization of the smoke in Figure 10(a). The input power to the motor and the wind speeds are varied from 1.5 to 2.2 Watts and 0 to 1.5 m/s, respectively. The corresponding flapping frequency may range from 15 to 20 Hz. The data had a sample rate of 1,000 points per second for a total of 13 seconds. This corresponds to 260 and 195 cycles per measurement for a flapping frequency of 20 and 15 Hz, respectively.

The applied voltages for the MAV are 3.3, 3.7 and 4.1 volts. The angle of attack (AOA) is set at 0 degrees and the wind speed ranges from 0 to 1.5 m/s. The plots for the aerodynamic performance vs. power are depicted in Fig. 10(b)-(d). Fig. 10(b) shows the mean lift force is positive even at 0 degree of AOA and it increases with increasing wind speed and flapping frequency. Fig. 10(c) shows that the thrust force stalled at 15 gf under 18 Hz of flapping frequency and it decreases with increasing wind speed. The stall phenomenon may be caused by aeroelastic effects of the wing structure. Therefore, the maximum performance of the MAV is running at around 17 Hz. It should be noted that when the MAV is hovering, it will subject to an angle of attack of 57 degree to maintain a total MAV weight of 12.56 gram.

(a) (b)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

1 1.5 2 2.5

Power (watt)

Lift

forc

e (gf

) . U= 0 m/s

U=0.5 m/sU=1.0 m/sU=1.5 m/s

(c)

6

8

10

12

14

16

1 1.5 2 2.5

Power (watt)

Thru

st (g

f)

. U= 0 m/sU=0.5 m/sU=1.0 m/sU=1.5 m/s

(d)

15

17

19

21

1 1.5 2 2.5

Power (watt)

Freq

uenc

y (H

z)

. U= 0 m/sU=0.5 m/sU=1.0 m/sU=1.5 m/s

Figure 10. Wind Tunnel Results.

V. CFD Simulation The Computational Fluid Dynamics (CFD) program, SC/Tetra10, developed by Software Cradle Company was

used to simulate the MAV design. The model is the exact replicate of the origin design shown in Figure 8 but it does not include the electronics, motor, and gears. Excluding these from the model will simplify the geometry, making it easier for gridding. Also, these features will not significantly affect the air flow generated by the wings. The main goal of this research is to optimize shape and size of the MAV and compare with the experimental design. Our overall goal is to reduce the wingspan while maintaining functionality and controllability. The results assume that the MAV has rigid wings. Since the aeroelastic effects of the wings are not taken into account here, a direct


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comparison with experiments is not possible. However, the simulation of a MAV with a flexible wing by coupling SC/Tetra CFD and ABAQUS FEA software is currently in progress.

The overset mesh with moving elements feature in Sc/Tetra was used to simulate the flapping wings of the MAV. This feature will also be implemented to study the effects of the control surfaces found in the tail of the MAV. Currently, the simulation is of a stationary MAV with zero angle of attack and the flapping frequency simulated was 100 radians per second (approximately 16 Hz). Particles were released from the wing’s surfaces during the simulation. These particles are used to observe the vortices produced from the edge of the wing surfaces shown in Fig. 11.

Figure 11. A snapshot of CFD results - particle tracking.

The dynamic lift coefficients obtained from CFD are shown in Figure 12. A key characteristic of the MAV being studied is that it generates lift which is in accord with the wind tunnel observation. Some key observation points in the wing oscillation period are the minimum, zero, and maximum lift points. These points are marked with the numbers one through five. Also shown are the surface pressure contours that correspond to these points. The point where the lift coefficient is zero corresponds to a very low surface pressure when compared to the other three positions in the cycle.

Figure 12. CFD results of the MAV with rigid flapping wing - Lift Coefficient and Surface Pressure.


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VI. Flight Test After assembling all the components, includes the transmission model, flapping wings, fuselage, tail, receiver,

battery, and actuators, the total weight is 10.8 grams (12.56 grams with Camera) with a span of 20 cm, as shown in Fig. 13. The small size and light weight of the MAV enables it to have a more outstanding flight performance than other MAVs. The flapping MAV demonstrated the ability to perform acrobatic moves, such as dashing, rapid turning, taking off and landing, looping and hovering. The record speed was 15 mph and the record flight time was 1,088 seconds with a 90 mAh poly-lithium battery. The flapping MAV demonstrated the ability to perform simple acrobatic maneuver and to carry on an ISR mission in the air, as shown in Fig. 13. The MAV has also flown successfully outdoor with a gust wind of 5 mph. The video clips of flight tests of the present MAV are available at the www.youtube.com website: http://www.youtube.com/watch?v=My-6LLXDaKM (speeding demonstration) http://www.youtube.com/watch?v=evPWcU6FGx0(indoor demonstration) http://www.youtube.com/watch?v=nxCL5t7347U&feature=related (outdoor demonstration).

(a) (b)

Figure 13. Actual flight tests of the current MAV: (a) during an acrobatic maneuver & (b) during an ISR mission.

VII. Towards Autonomous Flights Although we have designed a light-weight single-camera MAV capable of flying indoors and outdoors, it is

still based on human remote control. Because the payload and battery-power restrictions are very limited, our design for autonomous flying implies tremendous constraints in terms of energy power consumption, sensor simplicity, and airframe architecture. Moreover, controlling such systems is quite different from controlling more conventional outdoor micro aerial vehicles, which can rely on high-precision inertial measurement units, GPS, laser scanning, radars, and visual horizon detection systems.

Current autonomous flight control algorithms for UAS were designed to follow a given trajectory defined by a set of GPS waypoints navigation. If the mission entails Intelligence, Surveillance, Reconnaissance (ISR), there is a need for the vehicles to loiter (or hover) upon arrival at the target area in order to collect useful data information. Loitering/Hovering requires a significant change in the guidance and control methods of air vehicles, especially in the urban environment. It is often desirable for the vehicles to maneuver through complex urban environments with significant turbulence-like effect created by winds in the presence of buildings, obstacles and unexpected objects. In addition, the flight will have the possibility of autonomously and opportunistically choosing its own trajectory so as to react to unexpected gust wind and it will gain attitude by turning into thermal gradients, or/and make use of slope-winds to exploit wind gradients in order to save energy. These demands require advanced control algorithms and techniques to provide safe, reliable and long-endurance autonomous flight, along with an extremely maneuverable flight vehicle.

Obstacle avoidance is a necessary capability of MAV to fly in urban and indoor environments. Here we adapted a combination of two techniques to achieve obstacle avoidance mission; Edge detection image processing techniques to identify the location of the tracked objects and determine their shape and extent and the Lucas-Kanade tracking algorithm to provide velocity vector relative to objects and environments.

In the current work, the vision-based system is equipped with a pair of optical sensors to measure distances to objects similar to the human vision system11. Although in real MAV applications, smaller and low-powered cameras will be used, as a demonstration, figure 14 shows a camera setup that was utilized for experiments on a shake table to explore the effect of seismic events on office equipment. The cameras will be mounted in such a way that they can capture images of a similar area but at different angles to ensure that 3D locations of objects in the vicinity can be computed relative to the MAV. The images will be transferred wirelessly to the computer controlling the MAV.


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Using image processing techniques, such as edge detection, the moving objects were tracked as shown in Figure 15. Once the tracked objects are matched within the two sets of images captures by the pair of cameras using image registration techniques, 3D location of the tracked objects relative to the camera setup can be computed based on epipolar geometry. Obviously, a single camera can only provide a two-dimensional location of the tracked object relative to the camera. When using a second camera, the distance to the camera can also be determined resulting in a three-dimensional location. The principle of epipolar geometry is illustrated in Figure 16. In order to determine the distance for a given point P that resulted in a pixel Pl captured by the left camera, the light ray is traced backward from the focal point Fl of that camera through the pixel Pl. This ray eventually encounters the point P. However, the exact distance is not known at this point. By using the second camera, this distance can now be computed. The line represented by the connections between the points Er and Pr, where Er is simply the intersection between the image plane of the right camera and the line connecting the focal points of both cameras; i.e., Fl and Fr; and Pr is the projection of the point P as captured by the camera; i.e., the intersection between the image plane of the right camera and the point P and the focal point Fr, now resembles the projection of the light ray that was traced back from the focal point of the left camera Fl through the projected point Pl captured by the left camera all the way to the actual point P. As a result, the distance between the left camera and the point P can now be computed based on the distance between the points Er and Pr within the image captured by the right camera.

Salient features selected from the edge detection image processing techniques defined in the previous frames are selected in the subwindow and tracked using the Lucas-Kanade feature tracker12. Given a feature point (x,y) and a small window centered at this point in the current image I, the tracking algorithm gives the displacement

[ , ]x yd d d=r

by minimizing the 2L norm: ( ) 2[ , ] arg min , , [ , , )x y x yd d I x y t I x d y d t t⎡ ⎤= − + + + Δ⎣ ⎦∑ .

By assuming a small displacement vector dr

, the linear closed-form solution becomes: 1d H b−=r

,

where x x x y

y x y y

I I I IH

I I I I⎡ ⎤

= ⎢ ⎥⎣ ⎦

∑ ∑∑ ∑

, x t

y t

I Ib

I I⎡ ⎤

= − ⎢ ⎥⎣ ⎦

∑∑

and xI , yI and tI are x, y, and t derivatives of the image.

The equations will be solved by the iterative Newton-Raphson method in pyramids of images on a small subset of distinctive pixel windows, as shown in Figure 17. From the correspondences of the tracked features, the algorithm estimates the relative motion of the vehicle, which will then be used for MAV real-time control application.

Figure 14. Set of two cameras to allow for estimating distances.

(a) (b)

Figure 15. Edge detection image processing techniques: (a) identify the location of the tracked objects, (b) determine their shape and extent.


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`

P

Pl

Pr

Fl Fr

El ER

`

P

Pl

Pr

Fl Fr

El ER

Figure 16. Epipolar geometry.

Figure 17. The Lucas-Kanade tracker where the white dots are selected feature points.

VIII. Concluding Remarks There are at least eight inter-connected scientific disciplines within the MAV design trade space, as shown in

Figure 18: airframe & structures, aerodynamics, navigation, feedback & control, materials, sensors & actuators, propulsion & power, and communications. Because the size, shape, weight and aerodynamic restrictions imposed on the vehicles, all these areas are intertwined among one another and therefore a system consideration of the total design cannot be shortcut even at the earlier stage of the design cycle.

Figure 18. Multi-disciplinary researches for the development of MAV.


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The research for an autonomous MAV is just begun, what was described here is only the tip of the iceberg. There are still many unexplored areas needing attention if our final goal is to mimic the nature such that an MAV can be as agile as a dragon fly or a fruit fly.

Acknowledgments The author would like to thank his MAV team members for their contributions to this paper: Alexander Feist,

Jaderic Dawson, Jeremy Crank, Dr. Larry Dosser of MLPC, Professor Joseph Shang, Professor Haibo Dong and Professor Thomas Wischgoll. The participations of the US Air Force Wright Patterson Research Laboratory, Software Cradle Co., Ltd. and Mount Laser & Photonics Center, Inc. to our MAV program are also appreciated.

References 1Muller, T. J., Kellogg, J. C, Ifju, P. G. and Shkarayev, S. V., Introduction to the Design of Fixed-Wing Micro Air Vehicles,

American Institute of Aeronautics and Astronautics, Inc, 2006. 2Pornsin-sirirak, T. N., Tai, Y. C., Nassef, H., and Ho, C. M., “Titanium-Alloy MEMS Wing Technology for a Micro Aerial

Vehicle Application,” Sensors and Actuators A: Physical, Vol. 89, No. 1-2, pp. 95-103, 2001. 3Barrett, R., McMurtry, R., Vos, R., Tiso, P., De Breuker, R. Barrett, R., McMurtry, R., Vos, R., Tiso, P., and De Breuker, R.,

“Post-Buckled Precompressed (PBP) Elements: A New Class of Flight Control Actuators Enhancing High-Speed Autonomous VTOL MAVs,” Proceedings of SPIE - The International Society for Optical Engineering, Vol. 5762, pp. 111-122, 2005.

4TU Delft, website: http://www.defly.nl/ 5Jones, K. D., Bradshaw, C. J., Papadopoulos, J., and Platzer, M. F., “Bio-Inspired Design of Flapping-Wing Micro Aerial

Vehicles,” Aeronautical Journal, Vol. 109, No. 1098, pp. 385-393, 2005. 6Banala, S. K. and Agrawal, S. K., “Design and Optimization of a Mechanism for Out-of-Plane Insect Wing like Motion with

Twist,” Journal of Mechanical Design/ Transactions of the ASME, Vol. 127, No. 4, pp. 841-844, 2005. 7McIntosh, S.H., Agrawal, S.K., Khan, Z., “Design of a Mechanism for Biaxial Rotation of a Wing for a Hovering Vehicle”,

IEEE/ASME Transactions on Mechatronics, Vol. 11, No. 2, pp. 145-153, 2006. 8Harvard Microrobotics Lab website: http://micro.seas.harvard.edu/ 9Liang, Z. and Dong, “Computational Study of Wing-Wake Interactions between Ipsilateral Wings of Dragonfly in Flight”,

AIAA 2009-4192, 2009. 10Software Cradle Company, User Manuals and Guide, 2008. 11Wischgoll, T., Hutchinson, T. C., Küster, F, “Optical (Camera-Based) Technology for Seismic Risk Assessment”, ASME

International Mechanical Engineering Congress & Exposition, Washington, D.C., 2003. 12Kanade, T., Amidi, O., and Ke, Q, "Real-Time and 3D Vision for Autonomous Small and Micro Air Vehicles," 43rd IEEE

Conference on Decision and Control, December, 2004.

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