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Integrated MAV Systems:Hovering:Rotary-Wings & Flapping-Wings
Alfred Gessow Rotorcraft CenterUNIVERSITY OF MARYLAND
1st US-European Micro-Aerial Vehicle TechnologyDemonstration and Assessment, Germany
September 20, 2005
Inderjit ChopraAlfred Gessow Professor &
Dirctor Alfred Gessow Rotorcraft Center([email protected])
• Design Requirements• No dimension exceeds 15 cm (6 inch)• Gross takeoff weight 100 grams• Loiter time of 60 minutes• Payload capacity of at least 20 grams
• Additional considerations• Minimum mechanical complexity• Fully autonomous (out of sight operations)• All weather operations• Low production cost• Rapid deployment• Low detection
Micro Air Vehicles: Definition
Hover
Small
Novel
• Military• Surveillance missions (over the hill
and confined areas)• Infrared images of battlefields and
urban areas (around the corner)• Mine detection in war zone
• Civil• Biological/chemical agent detection• Agriculture Monitoring• Communication Nodes/GPS• Traffic monitoring (long endurance)• Counter-drug operations
Urban MAV Missions•Monitoring Traffic Flow•Surveillance Imagery
MAV Applications
• Increasing terrorists and Urban warfare threats• Miniaturized Sensors: Availability• Expanded capability of data acquisition, analysis and
transmission (IT & wireless technology)• Micro actuators and multifunctional smart materials• Potential for long endurance systems• Low cost systems
(can be organic with a soldier)• Increasing focus on biologically-
inspired flight systems
Micro Air Vehicles: Key Drivers!!
MAV Weight Breakdown Foch (NRL)
• Airframe ~ 21%• Engine ~ 11%• Battery ~ 30%• Payload ~ 21%• Avionics etc ~ 17%
10-3 10-2 10-1 1 10 10010-8
10-6
10-4
10-2
1
102
104
Wing Span or Rotor Diameter [m]
Mas
s [k
g]
Rotorcraft
Birds
Insects
Rotaryseeds
UAVs
Some Perspective on ScaleSome Perspective on Scale
Reynolds NumberReynolds Number
Aerodynamic ScaleAerodynamic Scale
ρ = air density
c = chord
V = velocity
µ = fluid viscosity
ρµcV
ForceViscousForceInertial =
MAVs operate in the very low Reynolds number flight regimeMAVs operate in the very low Reynolds number flight regime
Reynolds Number
Gro
ss W
eigh
t (lb
s)-
Adapted from:
McMichael, J. and Francis, M.,
“Micro Air Vehicles – Toward
a New Dimension in Flight”,
DARPA, 1997.
Aerodynamic EnvironmentAerodynamic Environment
106104
1021
10-2
10-4
Sender
Pioneer
Cessna 150
F/A- 18 Hornet
C-5 GalaxyMAVs
MAVs
Less than 6”
3 104
105
106 10 7
108
Dragonfly
Hummingbird
10
Reynolds Number EffectReynolds Number Effect
Max Lift to DragRatio
Max Lift Max Drag
Reynolds Number EffectReynolds Number Effect
Reference Reynolds Number Reref=105
Profile DragRe>105 Cd=Cd0refRe<105 Cd= Cd0ref (Reref/Re)1/2
CLmin drag( )CLmin drag( )
ref
=CL min power( )
CLmin power( )ref
=Reref
Re
14
If Reynolds number is reduced from 105 (Reference) to 103,profile drag increases 10 times its reference value andlift coefficient for minimum drag or power has to increase over 3 times its reference value (say CLref=.8, CLnew =2.5)
Most Small Insects100 < Re < 1000
Large Insects to Small Birds1000 < Re < 15000
BirdsRe >15000
•Delayed stall•Wake capture•Rotational circulation
•Dynamic stall•Delayed stall•Wake capture
•Bound circulation•Quasi-Steady mechanisms
Biological Lifting Mechanisms at Low Re
MICRO HOVERING AIR VEHICLES
• Non-Hovering Vehicles: Fixed-wing based
• Hovering Vehicles: Rotor Based• Single main rotor (with & without tail rotor)• Ducted fan rotor• Co-axial rotor• Tiltrotor, tiltwing, quadrotor, hybrid systems• Revolutionary designs
• Hovering Vehicles: Flapping-Wing Based• Bird-flight based• Insect-flight based (Efficiency at small scale?)
• Hovering Vehicles: Reaction Based(power intensive)
Micro Hovering Air Vehicles:Rotor-Based
MICOR (University of Maryland)MICOR (University of Maryland)
15 cm (6”)15 cm (6”) dia dia coaxial 2coaxial 2--bladed rotorsbladed rotors
Weight~100 g, Payload ~10g8% camber circular arc airfoilsRe.75R ~20,000Endurance ~ 10 minutesFixed pitch, variable speedrotors (feedback on lower)
Swashplate controls only lower rotor
First generationNo lateral control
Second generationLateral control implemented
Using swashplate
(Video)
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
Rotor system
MotorVanes foranti-torque
Yaw control surfacesServos
Rotor diameter 27 cm
Battery pack
Main rotor- Two bladed teetering - Pitch flap coupling(δδδδ3 angle of -45°)
-Servo paddles
Swashplate Control- Longitudinal- Vertical- Lateral- Pitch- Roll
Vanes (feedback)- Anti-torque- Yaw control Electronics
3 micro-servos Receiver, brushless motor controllers
Main rotorStabilizer bar
Motor
Anti-torque vanes
Protective ring
Weight breakup
20 . 6.5Swashplate
40 . 13Electronics28 . 9Rotor system
58 . 19Motor (brushless DC)55 . 18Battery (700 mAh Li-Poly)
106 . 34.5Structure
307 . 100Total
Weight (gms) %
Component
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
Thrust load cell
Torque Sensor
Hall effect sensor
Measurement of HoverPerformance:
•Thrust•Torque•Rotational speed
Hover test stand
FMCTCP
Inverted rotor
FM =Ideal Power required to hover
Actual Power required to hover
Rotor Hover Test
Figure of Merit
Blade Airfoil Variations
Baseline
Twisted
Tip-Taper
Planform-Taper
Planform-Taper
Camber Distribution Planform Distribution
Experimental Results
4500RPM
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0 0.005 0.01 0.015 0.02 0.025CT
FM Twisted 8%
Untwisted 8%
NACA 0012
Flat plates
3500RPM
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0 0.005 0.01 0.015 0.02 0.025CT
FM Twisted 8%
Untwisted 8%
NACA 0012
Flat plates
Maximum FM at 4500 RPM is 0.43 with twisted 8% camber bladesFM of full scale helicopters ranges from 0.7 to 0.85
FM: Figure of Merit
Sharpened Leading-Edge Airfoils
• Sharp leading-edge increases FM
• Smaller rise in FM for cambered airfoil
Sharpened LE can improve airfoil performance
7.0% camber 7.0% camber
FM
CT/σσσσ0 0.04 0.1 0.14 0.2
0
0.1
0.2
0.3
0.4
0.50.55
7.0% camber
with LE camber sharpened LE
Flat plate
Flat plate with sharpened LE 15º
CT/σσσσ
Blade Tip Design
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 0.005 0.01 0.015 0.02
CT
FM
Prandtl’s Tip
Rectangular Tip
Improved rotor performanceby modifying tip shape
Thrust/Power of MAV
Better power-loading curve for cambered blades
Higher power-loading at reduced disk loading
Planform variation has small effect 0 5 10 15 20 25 30 35 400.05
0.1
0.15
0.2
0.25
Disk Loading [N/m2]
Pow
er L
oadi
ng [N
/W]
7.0% camber at x/c=1/2 and sharpened LESharpened LE flate plate 15oSharpened LE flate plate 15o with 2:1 tip taper
Camber FM =.53
Flat Plate FM=.40
Flow Visualization
7% camber, 2.75% thickness with sharpened LED=6” 2-bladed rotor, 3600 RPM, Re=36.8*103
Main Vortex
VortexSheet
Rotor Plane
Wake Obstruction
MainVortex
Strong tip vortices
High induced velocities in tip region
Vortical shed wake obstruction increases DL and lowers FM
Rotating-Wing MAV Performance
ProfileEffects
InducedEffects
•Better designs may come through careful aerodynamic optimization•Gains may not come through improvements in airfoils alone•Performance goals met through understanding of flow physics•Induced and profile effects have strongly interdependent effects
Improvement of hover efficiency using duct around the rotor (plus safety protection of rotor)
Figure of Merit M: Hover Efficiency is defined in terms thrust production per unit input powerFor present designs: M is less than 0.5Goal:Increase M over 0.8
Rotor Hover Efficiency
Shrouded-Rotor Concept
Key Design Parameters
• Expansion ratio/Diffuser angle– Want this to be as large as
possible for best performance
• Inlet lip radius– Incoming flow forms a suction peak
on the inlet lip; cause of thrust augmentation
• Blade tip clearance– Proximity of shroud wall reduces strengthof blade tip vortices; reduces blade tip losses
Experiment: Model Configurations
Test stand
Electric motor
Rotor by itself Rotor with shroud attached
Rotor inside shroud, not connected to
shroud
Experiment: Thrust Ratio vs. Total Power
Thrust Coefficient, CT Thrust Ratio, Ttotal / Tfree
0 0.005 0.01 0.0150
0.01
0.02
0.03
Total Power Coefficient, CP
LR13-D00 LR09-D20-δδδδ
LR06-D10 LR09-D20
Free Rotor
0 0.005 0.01 0.0151.2
1.4
1.6
1.8
Total Power Coefficient, CP
LR13-D00
LR09-D20-δδδδ
LR06-D10 LR09-D20
Increase lip radius: Increase thrust
Decrease tip clearance: Increase thrustDiffuser angle: Thrust increases with small angle <100
PowerPower
0 0.2 0.4 0.6 0.8 1
-0.5
0
0.5
1
1.5
2
2.5
r / R
v / v
iShrouded Rotor Wake:
Effect of Blade Tip Clearance
δδδδtip = 0.1%
δδδδtip = 0.8%
δδδδtip = 1.6%
Isolated rotor
LR13-D10, 31% l/Dt
(z/R = 0.62)
As tip gap decreases, wake profile approaches to uniform
Shrouded-Rotor
Inlet Diffuser
0.00
0.02
0.04
0.06
0.08
13579111315
Tap #
Pre
ssur
e C
oeff
icie
nt, -
Cp
Rotor Plane
40o
30o
20o
10o
Optimized Configuration: 13% lip radius, 100 diffuser angle and 72% diffuser length results in 95% increase in thrust for same power
Challenge: Structural weight of shroud must be less than lift augmentation plus lower performance degradation in forward flight
Rotary Wing Micro Air Vehicles:
Unconventional Configurations
Problems with Conventional Rotary-Wing Systems
• Poor hover efficiency at small scales– Mainly due to low Re– Profile power dominates
• Maximum Figure of Merit (FM) < 60%– Full scale helicopters have FM~80%
• Unconventional rotor-based configurations- Cycloidal propulsion- Whirling arm rotor- Other configurations?
power Actualpower Ideal=FM
Cycloidal Propulsion System
•Pitch angle of each blade is varied sinusoidal in each revolution•Thrust vector changes with pitch amplitude and phase
MAV Vehicle Model
Cycloidal Rotors
Electronics Package
Fuselage/Landing Gear
Electric Motors
Battery
Two Cycloidal Rotors rotating in opposite directions
Cycloidal Propulsion System
•Good Points:Ability to change direction of thrust instantly up to 360 deg
Good maneuverability
High thrust possibility
•Weak Points:•Limited previous work
•Complex airflow
•Weight of mechanism
Cycloidal Propulsion System
•Challenges:To achieve a higher figure of merit with low structural weight
Simplify pitch changing mechanism
Optimize BladesThrust
0 400 800 1,200 1600
20
40
60
80
100
120Theoretical, 25 degreesTheoretical, 10 degreesExperimental, 25 degreesExperimental, 10 degrees
Rotation
Whirling Arm Rotor
!"
•Good Points:Reduced induced power due to simulated forward flightPotential for higher figure of merit
•Weak Points:•Complex airflow•Asymmetric lift distribution•Complexity of 2 rotors
Whirling Arm RotorV∞∞∞∞
V∞∞∞∞
Ω
Induced
Profile
Total“ Power Bucket ”
µµµµ
P/Ph
#! $
0 0.1 0.2 0.3 0.4 0.5
! %
&'%(
$%
!! %
•• Develop innovationsDevelop innovations rotor designs to increase hover rotor designs to increase hover
figure of merit (~0.8)figure of merit (~0.8)
•• Requires a good understanding wake phenomena and Requires a good understanding wake phenomena and
unsteady aerodynamicsunsteady aerodynamics at low Reynolds numbersat low Reynolds numbers
-- DevelopDevelop comprehensive CFD toolscomprehensive CFD tools detailed detailed testingstestings at low at low
Reynolds numberReynolds number flightsflights
MAV RotaryMAV Rotary--Wing Aerodynamics: Wing Aerodynamics: Summary ConclusionsSummary Conclusions
Micro Hovering Air Vehicles:Flapping-Wing Based
Mechanism of Flapping-Wing FlightInsects vs Birds
What can be learned from nature?
Bird Flight
Down Stroke: power stroke, outer and faster moving parts, also moving forward especially towards the end of stroke, At the end of stoke, the wing first rotate upward from the shoulder while the elbow is relaxed so the outer wing bends down as well as rotate to present least resistance to forward motion, During the down stroke, primary feathers are held close, perfect airfoil
Up Stroke: move up not to produce unnecessary drag and lose lift involving acomplex bending and twisting motion, Approximately halfway through the upstroke , the outer wing is moved up and back at a very rapid rate with outerfeathers separated, this reduces drag and produce extra lift, During up stroke the primary feathers get separated (slots)
Take off and landing: forward speed low, fast flapping, high amplitude, wings are spread wide
QuickTime™ and aMicrosoft Video 1 decompressorare needed to see this picture.
Adaptive Morphing Vehicle Geometries Inspired by Nature
Active Wing Tips for Roll Control
Aeilerons for Maneuvering
)*)* $$
+*+*
ROTATIONAL phaseROTATIONAL phase –– when the wings when the wings
rapidly rotate and reverse directionrapidly rotate and reverse direction
The wing stroke of a hovering insect is divided into four The wing stroke of a hovering insect is divided into four kinematic stages:kinematic stages:
,*,* -.-.
/*/* ..
TRANSLATIONAL phaseTRANSLATIONAL phase –– when the wings when the wings
sweep through the air with a high pitch anglesweep through the air with a high pitch angle
1 2 3
4 5
stroke plane
wing path
net force
wing section
downstroke
upstroke
Insect Flight FundamentalsInsect Flight Fundamentals
Rotational Lift producedduring pronation and supination by Magnus effect
Wing quickly rotates, using the shed vorticity of previous stroke to create lift: wake capture
Unsteady Mechanisms
Delayed Dynamic Stall: During translation phases, intense leading edge vortex stabilized by radial flow
Leading edge vortex
Wingmotion
StartingVortex
wing section
Aerodynamic Net-force
Birds vs Insects
<10,000>10,000Reynolds No.
Modest, tilting body and stroke plane
High, wing morphingSpeed
Quite commonVery rareHovering
High >50HzModest <10 HzWing frequency
Rigid wing, base motionActive wing morphingMorphing
UnsteadyLift enhancement
Quasi-steadyDrag-reduction
Aerodynamics
.1m and less0.15 to 3mSize
Less than .2g20g to 15 kgWeight
InsectBirdFunction
This mechanism is insect based flapping wing, passive pitch, biThis mechanism is insect based flapping wing, passive pitch, bi--stable stable device that is capable of replicating the complex kinematics of device that is capable of replicating the complex kinematics of insect insect wings in hoverwings in hover
Wings
Brushless motor4:1 gearbox
Crossedroller slide
Scotch yoke
Flap bearingassembly
Pitch bearingAssembly
Pitch actuators
Rotating diskassembly
Insect-Based Flapping-Wing Mechanism
Experimental Setup
QuickTime™ and aCinepak decompressor
are needed to see this picture.
QuickTime™ and aCinepak decompressor
are needed to see this picture.
Experimental Setup
Miniature Bending Beam Load-cell
Scaled-up Fruit Fly Wing Mounted on the Load-cell
Test Results & Validation
Wing III produces larger thrust from rotational circulation & improves prediction
Average ThrustPitching axis
0.5c
0.5c
0.2c
Mass: 1.8 grams
Mass: 1.1 grams
Mass: 1.1 grams
4 6 8 100
1
2
3
4
5
6
Frequency (Hz)
Thrust (grams)
Stroke : 80o
Pitch : +30o/-30o
Analysis (Wing III)
Analysis (Wing II)
Experiment (Wing II)
Experiment (Wing III)
3 11
Power Measurements
Wing IIIStroke : 800
Pitch: Downstroke 450, Upstroke -450
Thrust decreases rapidly at high frequencyWing III too heavy for high frequency operations
Flapping Frequency (Hz)
Thrust (grams)
9 10 11 121
2
3
4
5
6
7
9 10 11 120.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Flapping Frequency (Hz)
Power (Watts)
Power = flap vel. x horizontal force= aero power + inertial power
Light Wings
Wing III (1.3 grams) : too heavyLighter wings with composite frames were built
Results: Thrust increases marginal
Wing III
Wing VII
Wing IV
Wing IX
Wing VIII
1.3 grams
0.49 grams
0.86 grams
0.56 grams
0.61 grams
RC Microlite
Light Composite Wings
Visualization at 50% Span for Half Cycle
0o180o
Wing “Starting” Vortex
• Formation of LEV occurs during translation – form of dynamic stall• Powerful starting vortex at trailing edge until mid-stroke, with time-varying strength
The images represent 0 to 60 deg of wing cycle0 deg 13 deg
25 deg 40 deg 60 deg
Dynamic Stall Vortex (LEV)
• LEV: grows in size gaining more energy as the translation continues• LEV “spills” from leading edge (dynamic stall)• A secondary LEV is clearly visible• “Wagner” starting vortex, even though diffused, is present until mid-stroke
The images represent 65 to 90 deg of wing cycle
65 deg 75 deg 80 deg
90 deg 97 deg
Multiple LEVsImages represent 107 to 153 deg of flapping wing cycle
• LEV starts shedding (clearly a form of dynamic stall)• A new LEV forms before the first LEV reaches mid-chord• Presence of multiple vortices on top of the wing – can be a source of enhanced lift• Occurence depends upon the operating Re and the span location
107 deg 117 deg
137 deg 153 deg
Flow Developments During Supination
The images represent 157 to 196 deg of wing cycle
• Secondary LEV starts shedding • Shed wake vortices are clearly visible – complex 3-D flow field
157 deg 173 deg 180 deg
188 deg 196 deg
Schematic of Flow Structures
A strong leading-edge vortex during early part of stroke and gains energy from shed wake and then shed from LE
Second LE vortex forms before shedding of first from trailing-edge
Spanwise flow is of same order as tip speed, not strong enough to stabilize le vortex
Multiple vortices that enhance lift
Complex wakes: numerous vortices over the surface Complex wakes: numerous vortices over the surface
and welland well--structured wakes below the wingsstructured wakes below the wings
Unsteady aerodynamic phenomena dominantUnsteady aerodynamic phenomena dominant
Understanding of wake phenomena and modeling Understanding of wake phenomena and modeling
lackinglacking
-- Requires detailed experimental testing and Requires detailed experimental testing and
comprehensive CFD modeling (prediction tools)comprehensive CFD modeling (prediction tools)
FlappingFlapping--Wing Aerodynamics: Wing Aerodynamics: Summary ConclusionsSummary Conclusions
• Torque applied by an eddy current brake• Signal to speed controller varied to maintain constant
motor RPM• Voltage, current, torque, RPM are measured• Efficiency is
• Losses in speed controller are included in measurements
Electric motor testing
power Electricalpower Mechanical=η
Measured motor efficiency
0
10
20
30
40
50
60
0 5 10 15 20 25 30 35 40
Mechanical Power, Watts
Efficiency, %2000 rpm
3000 rpm
4000 rpm5000 rpm
0
0.1
0.2
0.3
0.4
0.5
0.04 0.08 0.12 0.16CT /σσσσ
FMMech FM
Elec FM
Measured Figure of Merit
Motor efficiency is approximately 50 %
Soft HingesFluidic Sensor
Piezoelectric Directional Fibers
Nanofiber Composites
Lithium Ion Battery
ElectrodeFiberElectrode
Multifunctional Wing
Multi-Functional Structure•Loads Carrying•Energy storage•Energy harvesting•Communication
Micro Hovering Air Vehicles:Power Issues
Hovering MAV
1
10
100
10 100 1000 10000 100000 1000000
Storage Efficiency Qr (W-Hr/Kg)
Pow
er P
lant
Eff
icie
ncy ηη ηη
pwr
(%)
JP10
Batteries
Model Aircraft Engine(378g; Methanol)
DARPA DMFC Objective
Endurance 1.0 min100 min
10 min1000 min
χf = 0.2
ηr = 0.4
drotor = 10 cmM = 100g
+−
=
fdiscr
Rpwr Lg
Qχ
ρηητ1
112
Challenges
IC Engines• Efficiency is THE critical parameter
– Scales unfavorably with decreasing size:» Increased storage volume leads to increased thermal losses» Thermal coupling to structure increases volume required for
complete combustion
• Reaction rate– Scales unfavorably with increasing storage efficiency (Qr)
» More energy dense fuels tend to be heavier (higher MW) and therefore react more slowly requiring larger volumes
– Can be slowed dramatically via heat loss to structure
• Mixing– Hydrocarbon fuels can be difficult to atomize and mix with air in small
volumes
• While the micro-engine projects seem promising, practical implementation in MAVs is still years away
– Enormous manufacturing challenges– Very inefficient– Governing physics at small scale not well understood
• Small hobby engines offer an interim solution– Plentiful and cheap– Problems:
» Quantitative performance data not available» Would be nice to have a reliable scaling relationship that designers of
MAVs could use to estimate how power output and fuel efficiency changes with engine size
» Noise level too high» Present efficiency level inadequate - but can be improved with modest
investment in research
Problem vs. Opportunity
OS OS
OS
OS
Performance Scaling
Reliable scaling relationships for efficiency do not exist!
1
10
100
0.01 1 100 10000 1000000
Mass (kg)
Effi
cien
cy (%
)
Estimated from Manufacturer's data
Measured
?
What is required?
• Fundamental investigation of physical processes impeding the miniaturization of heat engines– Thermal losses– Fluid-structure coupling– Flame broadening– Micro-scale mixing
• Quantification of performance of existing engines– Power output– Fuel efficiency – Scaling of performance with size– Quieting
Enable high-performance UAVs of the future
Understand what can be done TODAY
Micro Hovering Air Vehicles:Navigational Issues
Goal:Goal: Examine application of insect navigational strategies in the deExamine application of insect navigational strategies in the design sign of autonomous navigational system (outof autonomous navigational system (out--ofof--sight) for an MAV for sight) for an MAV for collision avoidance, terrain following and landing, insect collision avoidance, terrain following and landing, insect ocellusocellus--based based sensors for roll stabilization and panoramic vision systemsensors for roll stabilization and panoramic vision system
Insect vision and navigational systemInsect vision and navigational systemGood Points: fast, reliable and accurateGood Points: fast, reliable and accurateWeak Points: Not a simple reflexive system, simple nervous systeWeak Points: Not a simple reflexive system, simple nervous systemm
Insect Navigation
On-board stabilization
• Inertial Measurement Unit (IMU), GPS• Interface sensors and actuators with
microcontroller• Implement open and closed loop control• Hardware testbed: implement yaw
stabilization• Improving the sensor output (filter)• Implement control/semi-automation on MAV
Requires comprehensive understanding and Requires comprehensive understanding and
modeling of insectmodeling of insect--inspired visual guidanceinspired visual guidance
Development of algorithms for collision avoidance Development of algorithms for collision avoidance
and panoramic vision system in single and swarm and panoramic vision system in single and swarm
flight modeflight mode
Requires a set of light weight sensors including Requires a set of light weight sensors including
miniaturized camera for outminiaturized camera for out--ofof--sight flight guidancesight flight guidance
Insect Navigation: Summary Insect Navigation: Summary ConclusionsConclusions
Insects Birds Airplanes
•Airfoil very thin flat•Modest active camber•Sharp leading-edge• L/D~2-6
•Moderately thick•Flat, modest camber and twist• Rounded leading-edge• Max camber at leading-edge• L/D~10
• Thick airfoil• Rounded leading-edge• Sharp trailing-edge• Max camber at mid-chord• L/D>10
Comparison: Insects, Birds & Airplanes
Hovering MAV Goals
Micro-engineBatteryPower
SwashplatelessSwashplatePrimary
All DOFVerticalControl
10 km50 mRange
>20 g0Payload
<100 g>100 gGross Weight
Vision-basedNoneAutonomous
20 m/s3 m/sSpeed
.85.5Hover FM
60 Minutes<10-15 MinutesEndurance
Expected LevelCurrent LevelItem
• Aerodynamics at low Reynolds numbers• Laminar flow modeling and viscous drag prediction• Flow separation control (passive or active, synthetic jets, blowing,suction, etc.)• Unsteady aerodynamics and wakes modeling
• Efficient power/propulsion at small scale• Modeling of phenomena associated with energy conversion devices• Energy Density efficiency prediction
• Structures and Materials• Modeling of nonlinear coupled motions• Morphological shape changes
• Stability and Navigational tools• Insect-inspired navigational strategies• Algorithms development for flight• Panoramic view from limited vision• Modeling Collision avoidance• Swarm mode of flight
• System Integration• Comprehensive aeroelastic models• Electronics Miniaturization• Flight testing and validation
10-4
10-3
10-2
10-1
1
101
102
103
104
105
106
Reynolds Number103 104 105 106 107 108
Micro Air Vehicles(Less than 6”)
MAVsGro
ss W
eigh
t (kg
)
Sender
F-18
Modeling Challenges and Technical Barriers
Propulsion and Power- micro engine- Thermo efficiency- Efficient fuel- Energy Storage
Maneuvering Capability- control surfaces- distributed sensors and actuators
Lightweight Wing Structures- Active shape deformation- Wing morphing
Sensing and Navigation- miniature electronics- Mems & insect based Low Reynolds Number Flow
- delayed Stall- flow control- wake capture
Biomimetic Kinematics- actuation (thorax)- efficiency- scaling
Flight Inspired by Nature at Low Re
AcknowledgementsGraduate StudentsMat TarascioBeerinder SinghtJason PereiraBen HeinEric ParsonsBeverly BeasleyJaye FallsNitin GuptaPeter CoppBrandon FitchettMoble BenedictA. Abhishek
Faculty ColleaguesNorm Wereley (Aero)Darryll Pines (Aero)Jayant Sirohi (Aero)Paul Samuel (Aero)Anubhav Datta (Aero)Gordon Leishman (Aero)Roberto Celi (Aero)Jim Baeder (Aero)Ben Shapiro (Aero)Ella Etkins (Aero)Chirs Cadou (Aero)Fred Schmitz (Aero)Marat Tishchenko (Aero)Bala Balachandran (Mech)Elisbeth Smela (Mech)Satinder Gupta (Mech)Rama Chellappa (EE)Reza Ghodesi (EE)Shivjumar (NCA&T)Srini Srinivasan (ANU)
SponsorARO (Gary Anderson)NRTC (Yung Yu)