Prof. Jean-Marc MoschettaProfessor of AerodynamicsDepartment of AerodynamicsEnergetics and PropulsionISAE BP54032, 31055 Toulouse [email protected].
Hovering Capabilities of Fixed-WingMicro-Aerial Vehicles
Jean-Marc Moschetta1, Institut Supérieur de l’Aéronautique et de l’Espace, Université de Toulouse, Franceand
Sergey V. Shkarayev2, Department of Aerospace and Mechanical Engineering, University of Arizona, Tucson, Arizona
Fixed-wing micro air vehicles (MAV) are very attractive for outdoor surveillance missions since theygenerally offer better payload and endurance capabilities than rotorcraft or flapping-wing vehicles ofequal size. They are generally less challenging to control than rotorcraft in outdoor environment andallow for a dash capability to escape enemy attention. On the other hand, they usually fail miserablyto perform vertical take-off and landing (VTOL) and sustain stable hover flight which proves to becrucial for urban surveillance missions including building intrusion. The present paper investigatesthe possibility to improve the aerodynamic performance of fixed-wing MAV concepts so as to allowfor true hovering capabilities and still maintain high cruise speed for covertness.
Several combinations of rotors and fixed-lifting surfaces were tested, analyzed and compared. First,a tandem-rotor biplane MAV configuration was designed and tested as a result of different biplanepowered configurations. A low-speed autonomous fixed-wing MAV was fabricated and flight testedto perform multi-tasking outdoor surveillance missions. Secondly a side-by-side comparison of a tilt-wing and a tilt-body powered configuration with a pair of counter-rotating motors in tractor configurationwith MAV configurations were carried out. The tilt-body configuration was shown to be more suitablefor MAV applications with higher hovering performances. Second, a coaxial tilt-body concept basedon coaxial motors and contra-rotating propellers inspired from the Convair XFY1 “Pogo” experimentalaircraft was designed and tested. A wind tunnel test was carried out to fully characterize theaerodynamic performances of the coaxial tail-sitter configuration, named Vertigo. An autonomousversion was developed in order to autonomously perform transitions between horizontal and verticalflight. A smaller 300-mm span version, called mini-Vertigo, was designed and fabricated based on aseries of wind tunnel tests using miniaturized coaxial-rotor propulsion set. Autonomous altitude holdand attitude stability augmentation were then achieved using specific control laws adapted for thePaparazzi autopilot system. Thirdly, a new no-through-shaft coaxial-rotor configuration has beenproposed in order to enhance the prototype ruggedness through an embedded spherical structuremade of carbon rods. It is believed that such a crash-proof VTOL MAV, called Cyclope, can be veryattractive for the use of MAV systems in real operations and allows for further size reduction such asfor Nano Air Vehicles applications. Current prospects include both further wind tunnel tests usingnew high-precision micro sting-balances on coaxial-rotor tail-sitter MAVs and the development ofcontrol laws to autonomously perform transition flights.
1 Professor of Aerodynamics, Department of Aerodynamics, Energetics and Propulsion, ISAE BP54032, 31055 Toulouse Cedex, France, jean-
[email protected] Associate Professor, Department of Aerospace and Mechanical Engineering, The University of Arizona, PO Box 210119, Tucson AZ 85721-
00119,[email protected].
Hovering Capabilities of Fixed-Wing Micro Air Vehicles
Jean-Marc MoschettaInstitut Supérieur de l’Aéronautique et de l’Espace , Toulouse, France
Sergey ShkarayevUniversity of Arizona , Tucson, Arizona
1st US-Asian Demonstration & Assessment of Micro-Aerial & Unmanned Ground Vehicle Technology, 10-15 March, Agra, India
2MAV’08March 10-15, 2008
Motivation
Launch
Loiter
Hover
Building intrusion
Dash
Phase 1Phase 1Phase 1Phase 1Phase 2Phase 2Phase 2Phase 2
Phase 3Phase 3Phase 3Phase 3
Phase 4Phase 4Phase 4Phase 4
Typical MAV mission profile
3MAV’08March 10-15, 2008
MAV design challenges
• Challenging to control
• Fast horizontal flight
Fixed Wing MAVs Rotorcraft MAVs
• VTOL Fixed-Wing MAV– High speed for covertness
– Low speed for clear images
– Limited electric consumption
• Poor image capturing
• Maneuverability in confined environment
MinusKiool (2003)
20 cm, 60 g
Br2C (2007)
36 cm, 490 g
4MAV’08March 10-15, 2008
Camber changes h = 3-9% with synchronous change of reflex hi = 1-3%
Test flights were conducted with Pitot tube sensor
With camber increases from 3% to 9% minimal speed decreases by about 100%
A low-speed in-flight adaptive wing MAV
5MAV’08March 10-15, 2008
A low-speed tandem wing MAV
TYTO250g - 40 cm
• Tandem-wing MAV
• Gimbaled 2-axis camera
Moschetta, Thipyopas, J Aircraft, vol. 44, 2007
6MAV’08March 10-15, 2008
New MAV concepts
Tilt-body
Tilt-rotor
Tilt-wing
7MAV’08March 10-15, 2008
• Wind tunnel
– Test section 45 x 45cm
– Velocity 2-20 m/s
• Measurements
– Improved 5-component balance :
• force 0.004 N
• moment 0.002 N.cm
Experimental setup
Ground
LC4
LC2
LC1
LC3Motor
LC6
LC5
Adjustableplate controlledby motor tochange AoA.
Left Strut
Right Strut
Aft Strutalwaysperpendicular tothe model
longitudinal axis
Pivot Point
LC1 – 4 are fixed onto the ground,LC5 - 6 are supported by adjustable plate and alwaysrotate with the model
rl
Free Stream Velocity
Kochersberger, AIAA paper 2005-4759
Suharyono, Aerospace Sc. & Tech., 2006
8MAV’08March 10-15, 2008
Future MAV wind tunnel (2009)
Length 19 mWidth 4.5 mHeight 7 m
Test section 120 x 80 cmContraction ratio 10:1Turbulence 0.3%Speed 0 - 25 m/s
Variable-pitch fan
Test section length 2.5 m
6-component sting micro-balance: 8-mm
diameter, 100g max load,
9MAV’08March 10-15, 2008
Tilt-wing vs. tilt-body
• Speed 0-15 m/s
• tilt angles 0°, 30°, 60°, 90°
• PWM signal 40, 60, 80, 100%
• Struts corrections (AoA, speed)
30°
60°
Tilt-body (0°)
10MAV’08March 10-15, 2008
Λ,S2
,2
ΛS
( )02ααπ −Λ×= qSLTB ( ) TBTW L
SqL ×=−Λ×=
2
1
422 0ααπ
( ) ( )204
1 ααπ −×Λ= qSDi TB ( ) ( ) ( )TBTW DiqSDi ×=−×Λ=2
1
8
1 20ααπ
Tilt-body Tilt-wingααα == TBTW
11MAV’08March 10-15, 2008
Λ,S2
,2
ΛS
( ) WqSL TBTB =−Λ×= 02ααπ ( ) W
SqL TWTW =−Λ×= 042
2 ααπ
02 ααα −= TBTW
( ) ( )204
1 ααπ −×Λ= TBTB qSDi ( ) ( ) ( )TBTWTW DiqSDi ×=−×Λ= 28
1 20ααπ
WLL TBTW ==Tilt-body Tilt-wing
12MAV’08March 10-15, 2008
Tilt-wing vs. tilt-body
0
10
20
30
40
50
60
70
80
90
0 5 10 15 20
Velocity (m/s)
Tilt
ang
le o
r an
gle
of a
ttack
(de
g)
tilt wing
tilt body
0
20
40
60
80
100
0 5 10 15 20
Velocity (m/s)P
WM
Sig
nal (
%)
tilt wing
tilt body
Lift = Weight
Drag = Thrust
Tilt-wing may benefitfrom vortical lift effects
Tilt-wing requires more power near hover
Downwardforce
13MAV’08March 10-15, 2008
Tilt-wing vs. tilt-body
-0,009
-0,008
-0,007
-0,006
-0,005
-0,004
-0,003
-0,002
-0,001
0
0,001
0 5 10 15 20
Velocity (m/s)
dM(C
G)/d
AoA
tilt wing
tilt body
• « CG » located at 10% chord ahead of the AC at 16 m/s
• Each gradient calculated aroundequilibrium points
• Longitudinal stabilitygreatly reduced at lowspeeds
• Tilt-wing / tilt-bodyMAV configurations very comparable
14MAV’08March 10-15, 2008
A coaxial tail-sitter mini-UAV
• Tilt-body
• Coaxial rotor in tractor configuration
• Autonomoustransition flight
• rotor 500 mm
• weight 1.6 kg (incl. IMU, GPS, Modem…)
Convair « Pogo » XFY-1
(1954)
ISAE « Vertigo » mini-UAV
(2006)
15MAV’08March 10-15, 2008
Wind tunnel measurements
-0,6
-0,4
-0,2
0
0,2
0,4
0,6
0,8
1
1,2
-20 0 20 40 60 80 100
AoA°C
L
• Sting-mounted model
• Speed 0, 5, 10, 15, 20 m/s
• AoA -10°to 90°, sideslip
• flap efficiency, throttle
• strong vortical effects on wing-alone tests
• CD0 = 0.054, L/Dmax = 4
• CL > 0.8 at AoA 15°-55°
Stallangle
16MAV’08March 10-15, 2008
Coaxial tail-sitter
-0,3
-0,25
-0,2
-0,15
-0,1
-0,05
0
0,05
0,1
-20 0 20 40 60 80 100
AoA°
CM
@C
G
stallangle
• Stabilizing vortical effects (low aspect-ratio)
• Constant pitching moment gradient after stall (CoP)
17MAV’08March 10-15, 2008
Powered tests
0
2
4
6
8
1 0
1 2
1 4
0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0
Ao A °
V(m
/s)
0,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
1,6
1,8
0 10 20 30 40 50 60 70 80 90 100
For
ces
(daN
)
0,00
0,02
0,04
0,06
0,08
0,10
0,12
0,14
0,16
0,18
Pitc
hing
mom
ent (
daN
.m)
Aircraft horizontal force
Aircraft vertical force
Propeller horizontal force
Propeller vertical force
Aircraft pitching moment
Propeller pitching moment
• Balanced lift and drag (V, AoA, throttle)
• Propeller-alone tests carried out to evaluate propellers contribution during transition
• Equilibrium found throughout transition
• Propeller-induced nose-up pitching moment (side force)
• Aircraft pitching moment almost constant in transition (flap efficiency)
18MAV’08March 10-15, 2008
Propeller-wing interaction
10 20 30 40 50 60 70 80 900
2
4
6
8
10
12
14
AoA, deg
V, m
/s
1cos22
0
2
00
3
0
4
0
=
+
+
w
V
w
w
w
V
w
w
w
w α
2
0
2
000
sin2cos2
+
+= αα
w
w
w
w
w
V
w
VR
= − αα sin2sin 0
0
1
RS V
w
w
w
T
2w V
α
αS VR
Acknowledgement: Boris Bataillé & Damien Poinsot, ISAE & ONERA, Toulouse
McCormick
exp.
+ model
19MAV’08March 10-15, 2008
Simulation of transition flight
10 20 30 40 50 60 70 80 900
5
10
15
20
AoA, deg
AoA
w, d
eg
10 20 30 40 50 60 70 80 900
5
10
15
AoA, deg
Del
ta m
, deg
10 20 30 40 50 60 70 80 900
2
4
6
8
10
12
14
AoA
Vel
ocity
, m/s
VV
r
Effective wing AoA Relative wind speed Flap deflection
• Unstalled wing (stall angle 23°)
• Flap efficiency throughout transitionPoinsot et al., VTOL conference, RAeS 2008
20MAV’08March 10-15, 2008
MiniVertigo
200
Speedcontroller
Servo
Battery cell
2 Bolts, D2
Carbon tube 6 mm
Fiberglass 2 plies/side
Fiberglass, 1 ply/side Plastic insert
46
Motor mount
RC Receiver
Carbon tube 3 mm
Elevon300
Gyro-stabilized prototype
(2007)
Dual motor-propeller 50 g
3-cell Li-Poly batteries 60 g
Speed controller & receiver 16 g
Gyros & servos 22 g
Airframe 44 g-------------------------------------------------Total weight 192 g
21MAV’08March 10-15, 2008
Scaling effects
4 x 104
16 x 104
Rec
30
65
Size
(cm)
3216051.91Mini-Vertigo
671600241.80Vertigo
m/S (g/dm²)m (g)S (dm²)ΛMAV
8.229.0451011.55140Mini-Vertigo
9010.51658015.7500Vertigo
Pind(W)
PL (W/N)
P (W)DL (N/m2)T (N)Drotor(mm)
MAV
• Mini-Vertigo used high-pitch counter-rotating propellers (low RPM)
• Power loading (PL) includes motor efficiency
Shkarayev et al., J Aircraft (submitted), 2007
22MAV’08March 10-15, 2008
Conclusions
• Tilt-body MAV configurations combining tandem/coaxial rotors and fixed wings are promising candidates for complex outdoor/indoor surveillance missions in autonomous mode
• Tilt-body better than tilt-wing MAV
• Coaxial tail-sitter allows for balanced transition
23MAV’08March 10-15, 2008
Current prospects: nanorotors
• Weight decreases with size as
• FoM and power loading decrease with size (XROTOR)
535.1884.17 dW = Acknowledgements
Liu Zhen, PhD candidate, ISAE, Feb. 2008
24MAV’08March 10-15, 2008
Current prospects: autonomy
• Step 1: altitude/attitude hold
• Step 2: autonomous transitionAcknowledgements
Roman Krashanitsa, Univ. Arizona, 2007
25MAV’08March 10-15, 2008
Current prospects : improved airframe
• Embedded coaxial fixed-wing
• No through-shaft system
• Roll & fly
Vision (35 cm, 450 g)
Frankfurt, Germany, oct. 2007
MAV’07, Toulouse, France, sept. 2007
Acknowledgements
Dominique Bernard, ISAE, 2007
26MAV’08March 10-15, 2008
Thank you
Cyclope (20 cm, 100g)