Morphing wing concept for small UAV

VASILE PRISACARIU1,a , MIRCEA BOSCOIANU2,b, IONICĂ CÎRCIU2,c

1”Transilvania” University, 1 Colina Universităţii, Braşov, Romania 2 “Henri Coandă” Air Force Academy, 160 Mihai Viteazu, Braşov, Romania

a aerosavelli73@yahoo.com, bboscoianu.mircea@yahoo.com, ccirciuionica@yahoo.co.uk

Keywords: morphing wing, airfoil, aerodynamic analysis, sensors, actuators

Abstract: The biological flight involves the movement of a wing (lift surface) in viscous medium

and it generates lift and resistance for going forward through friction compared to Reynolds

number. The morphing concept is generally based on optimizing the aerodynamic form during the

mission so it can execute a maneuver flight. This article desires a short passage through the

mathematical aspect in 2D of the morphing profile concept.

Introduction

Generally a biological flight involves the movement of a wing (lift surface) in viscous medium

and it generates bearing and resistance for going forward through friction compared to Reynolds

number. The lift force is generated by the airfoil of the wing due to pressure difference between the

two surfaces of the wings and the resistance for going forward is due to the friction principal in

contact with the air and the vortex from the downstream of the wing located in different incident

angles.

Morphing transformations

Starting from the recent studies from the big universities and research centers (Bristol

University, NASA, DARPA) we can establish a classification of the morphing concept (figure 1):

omni-morphing (internal morphology with multiple non planar dynamic volume); active poly-

morphing (local multidirectional geometrical modifications and the wing is aero-elastic active:

sliding wings, telescopic wings, folding rotating wings, folding wings); passive poly-morphing

(local multidirectional geometrical modifications); active mono-morphing (local multidirectional

geometrical modifications: interconnected flaps with flight stabilizer, spoilers, weight reduction of

the wings, variable volume, variable chord wing, vectorial traction); unidirectional and discreet

mono-morphing (local multidirectional geometrical modifications: discreet spoilers as controlled

surfaces, flaps)[1].

Fig.1 Morphing concept

Biomechanics of the flying wing

Senses/ sensors. Flying creatures and machines must be capable to detect and feel the weird

atmosphere near them as well as their own position, location and structural configuration to perform

the flight activity into a given medium.

Applied Mechanics and Materials Vol. 332 (2013) pp 44-49Online available since 2013/Jul/15 at www.scientific.net© (2013) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMM.332.44

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Birds are capable of using these senses, like sight, hearing, smell but also special sensor systems

like: eco-location (bats), the linear and angular acceleration capacity with the help of the ears and

mechanic receptors at insects that feel a potential approach from something. Birds can feel the

electromagnetic field of the Earth that informs information for navigation.

Example of sensors (figure 2) and collected data: weather (temperature and humidity),

biometrical (the quality of the atmosphere-smoke, gas, contaminated atmosphere), navigation

(GPS), telemetry (speed, altitude, pressure), attitude (the position compared to other objects, the

position/form of the wing at every moment). This capacity can use special sensors like angular

gyroscopes for orientation and capitation widgets for air pressure through the wing.

a b c

Fig. 2 Ultrasonic sensor (a), pressure and temperature sensor (b), video sensor (c) [2]

Processing/ hardware. The signal entries from the birds senses (eyes, ears), must be integrated

and worked in the brain or flight computer. The processes and functions include special algorithms

for control, flight stability and navigation. Stability during the flight is the most important function

because without it you can not fly. At aerial vectors the processes which serve for the flight stability

are executed at top speeds.

In biological flight the commands are electrical impulses from the brain which stimulates

muscles and specific organs. At aerial vectors the commands are electrical signals that activate the

execution elements (actuators). Within the navigation processes we compare the information from

the passing points with a known geographical orientation so that we can calculate the best flight

course to our destination. The control function executes information and guidance and it generates

commands tot the action system to fly through the calculated course.

Actuation / actuators. The natural biological flight requires a special skeleton structure and

muscles [3] so it can perform flight figures and acrobatics (figure 3).

Fig. 3 Pterosaurs: first vertebrates in the flight Fig. 4 Morphing wing mechanisms

Oxford University 2008

Flight in the morphing concept requires specialized structures and elements so that it can modify

the position of the elements and structures the way we desire (figure 4). Also, the new types of

servo-actuators, movable winglets [4] and morphlets [5] extend the operational envelopes of the

future UAV together with the introduction and use of the GPS modules and autopilot for command

and control, (figure 5).

Applied Mechanics and Materials Vol. 332 45

Fig.5 Kestrel [6] and MP 2128x autopilot [7]

Advanced materials. The advanced morphing technologies, like compliant structures [8] with bi-

stable materials and aero-elastic manufacturing [9] should allow a multi-role design for aircrafts

with the same level of performance and flight quality.

.

The proposed morphing concept

The presented morphing concept is based on the wing torsion along of the wing span. The

extreme end of the wing will realize a difference of the incidence 200.

Fig. 6 Morphing by wing torsion

Fig. 7 Clark YH airfoil, morphing angle ± 100

[10]

Calculations regarding the airfoil with morphing. Starting from a classic aerodynamic profile,

we will calculate the aerodynamic features depending on the skeleton profile initially not deformed

and the morphing angle equivalent to β, (figure 8) [11].

we have increased incidence τ∆ :

βππ

βτ

−≅

−+=∆

c

c

c

c

c

c

c

c

c

c 11111 17,014

1arcsin2

Experimental we obtained the following relation

c

c1βτ ≅∆ (1)

where

c-the rope of the modified profile

c1-the rope of the morphing profile

β -morphing angel

46 OPTIROB 2013

Fig. 8 Morphing airfoil (medium torsion)

and the modification of the momentary coefficient

β3

11 12

−−=∆

c

c

c

cCm (2)

The hinge moment of the command surfaces. By turning o morphing command surface we will

modify the aerodynamic force which will produce a hinge moment (Eq.3), will be written as a form

that will obvious stake out the dependence on aerodynamic pressure, the geometrical features of the

commanded surface and the dimensionless coefficient:

mMAc CcSVM 2

2

ρ= , (3)

where Sc- the command surface area

CMA-the medium chord of the same surface

Cm- the moment coefficient

The dimensionless coefficient of the virtual hinge moment depends on the incident angle of the

fixed surface α and the turning angle δ of the command surface (Eq.4):

Ch=Ch(α, δ). (4)

With the help of the Profili v.2.25 software [12] we can obviously stake out the command on

each half-wing (simultaneously and alternative) which will lead to a handling grade that will be

according to the geometrical and mass features of the flying wing (figure 9, figure 10). We will

need to pay special attention to the internal structure of the lift surface because the handling

difficulty directly depends on the elasticity/rigidity of the flying wing [13].

Analysis was performed at Re = 272,000, for a speed V = 10m / s and c = 0.40 m chord profile.

We observe, as expected, in figures 9 and 10, a significant difference in lift and moment

coefficients. In Table 1 are shown the values of the coefficients on the three morphing angles.

Applied Mechanics and Materials Vol. 332 47

morphing 00 angle morphing 10

0 angle morphing -10

0 angle

Fig.9 Chart Cl-α and Cd-α

Fig.10 Chart Cl/Cd- α and Cm- α

Table 1. Data for morphing angles

morph 00 morph 10

0 morph -10

0

Conclusions

The special UAV missions require exceptional evolutions from UAV (evolutions at small

speeds, small turns, and quick maneuver). The proposed, implemented, analyzed morphing

solutions compared to a global indicator on reliability, control, maneuver and low fabrication costs

are all important for the selection of a morphing strategy.

Advanced sensors used to measure response features for flight maneuvers; the latest software

together with quality analysis methods for performances will lead to a global improvement of the

bearing surfaces.

Acknowledgment

The authors wish to thank the “Transilvania” University of Braşov and "Henri Coandă" Air

Force Academy of Braşov for supporting the research necessary for writing this article.

48 OPTIROB 2013

References

[1] Melin T., Isikveren A. T., Friswell M.I., Cost appreciation of morphing uav projects at a

conceptual design stage, 2008, p 6., information on http://michael.friswell.com/PDF_Files

/C239.pdf, accessed at 07.12.2012

[2] Information on http://www.diydrones.com, accessed at 10.01.2013

[3] Page C., Yuan F. G., Biologically Inspired Morphing Flight for MAV design, Department of

Mechanical and Aerospace Engineering North Carolina State University, (August 20, 2008),

information on http://www.mae.ncsu.edu/ssml/Materials/MAE478/Biologically%20Inspired

%20Morphing%20Flight.pdf, accessed at 10.12.2012

[4] Bourdin, P. Gatto, A. and Friswell, M.I. "The Application of Variable Cant Angle Winglets

for Morphing Aircraft Control", 24th

Applied Aerodynamics Conference, 5 - 8 June 2006,

San Francisco, California.

[5] Ursache, N.M. et.al., “Morphing Winglets for Aircraft Multi-Phase Improvement” AIAA-

2007-7813 7th AIAA ATIO Conf, 2nd

CEIAT Int'l Conf on Innov and Integr in Aero

Sciences,17th LTA Systems Tech Conf; followed by 2nd TEOS Forum, Belfast, Northern

Ireland, Sep. 18-20, 2007

[6] UAV flying guide, Kestrel autopilot system, 2008, 27p, information on

http://www.procerusuav.com /index.php, accessed at 12.01.2013

[7] Information on http://www.micropilot.com, accessed at 1701.2013

[8] D. Baker, D., Friswell M.I. "Design of a compliant aerofoil using topology optimisation",

International Workshop, Smart Materials and Structures, 12 - 13 October 2006, Toronto,

Ontario, Canada.

[9] F. Mattioni, et.al. "The application of residual stress tailoring of snap-through composites

for variable sweep wings", 47th

AIAA/ASME/ASCE/AHS/ASC Structures, Structural

Dynamics, and Materials Conference, 1 - 4 May 2006, Newport, Rhode Island.

[10] Guidelines for XFLR5 v6.03, 2011, 71p., information on www.xflr5.com, accessed at

15.12.2012

[11] Constantinescu, N.V., Găletuşe, S., Mecanica fluidelor şi elemente de aerodinamică, Editura

Didactică şi Pedagogică, Bucureşti, 1983, 506p.

[12] Duranti S. Profili 2.21 software, 2012, Feltre-Italia, information on www.profili2.com,

accessed at 14.12.2012

[13] Boscoianu M, Coman A, Pahonie R, “The optimization of CUMULUS micro aerial vehicle

aerodynamics by using the adaptive flexible wing concept”, in International Conference on

Fluid Mechanics and Aerodynamics, New Aspects of Fluid Mechanics and Aerodynamics,

Rhodos, Greece, August 20-22, 2008, ISSN 1790-5095, ISBN 978-960-6766-98-5

Applied Mechanics and Materials Vol. 332 49

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