Recent and Future Research for Bird-like Flapping MAVs of NPU
Prof. B.F.Song
Aeronautics School of Northwestern Polytechnical University
Main point
Introduction
Summary of PY-1
Some Research Developments in Flapping Wing’s Aerodynamics and Mechanism
Fix-wing MAVs developed in NPU
Wing Tunnel and Some Special Test Tools
0 Introduction
In 2000, a research team in NPU (Northwestern Polyte
chnical University) began to study flight mechanism and
make some flight test models of bird-like flapping MAVs
In 2004, a successful flight test mode, called as PY-1,
is achieved.
The parameters of PY-1
wing span 100 cmweight 280 gcruise time no less than 12 minflight speed 5-15m/smission equipment weight 20 gflapping frequency 5~10 Hzflapping angle 64 deg power motor + polymer
A clear image about ground objects has obtained by the colour video camera on-board.
At present, the research team is doing
research on the bird-like flapping MAV with
25-50cm wing span and it will be of
independent or half-independent flight
capacity.
our research plan for flapping wings with no more than 50 cm and the problems to be solved
wing span 100 cmmission equipment weight 20 gflight speed 5~ 10 m/scruise time no less than 10 min.flight control radio control
present Flapping MAV
wing span 25~50 cmmission equipment weight 20 gflight speed 5~ 10 m/scruise time no less than 10 min.flight control independent or half-independent flight capacity
future Flipping MAV
improving lift and propulsion efficiency of flapping wing
improving flapping mechanical efficiency and reducing energy loss
improving energy storage, reducing structure weight, increasing cruise time
increasing flight stability and flight capacity
independent or half- independent flight capacity
aerodynamics of bird-like MAV
bionic flapping mechanism
flexible wing techniques
Integrated battery and structure
Micromation and integrated equipments on board
innovate flaping wing MAV or sub-syetems
1 Summary of PY-1
PY-1 prototype
Based on The Aerodynamic Performance
Prediction System of Flapping Wing (APPSFW)
developed by our research group, the aerodynamic
characteristics of PY-1 could be predicted.
Aerodynamic Characteristics
V= 7m/sF=8Hz
V= 10m/sF=8Hz
(a) (b)
Some aerodynamic characteristics of PY-1
V= 8m/sF=10Hz
V= 10m/sF=10Hz
(c) (d)
O
A
B
C
principle and prototype of flapping mechanism system
Flapping Mechanism System
Fabrication and Flight test
(a) Designing (b) Laser cutting
(c) Machining (c) Assembling
In early flight test, the PY-1 could fly at about 30 m height for 10 minutes.
the color camera and photo taken in the air
PY-1 in flight
2 Some Research Developments in Flapping Wing’s Aerodynamics and Mechanism
Aerodynamics Aerodynamic Performance Prediction System of Flapping Wing (APPSFW)
according to J.D.Delaurier’s aerodynamic model
using modified strip theory
influence of vortex-wake, partial leading edge suction and post stall is
included
contributions of sectional mean angle of attack, camber and viscous
friction drag are also taken into account
The developed code can calculate the following aerodynamic characteristics of flapping wing in equilibrium flight:
average lift
average thrust
the input power required
the propulsive efficiency
Numerical Simulation of Finite Span Flapping Wings Using
Unsteady Euler Equations
With the moving grid strategy, a time accurate unsteady Euler Solver
based on dual-time stepping method is developed.
The developed code is able to calculate the unsteady flow field around
the flapping wings in three-dimensional flexible flapping and twist
motions as well as to evaluate the lift and the thrust output for different
wing motions.
Investigation of Numerical Solutions of Unsteady Navier-Stokes Equations for Wings at Low Reynolds Number
Based on the dual-time stepping method, the unsteady compressible Navi
er-Stokes equations at low Reynolds is solved. The flow field around a rect
angular wing and NACA0006 cross section in the motion of flap and twist i
s calculated.
The Investigation of unsteady flow mechanism of airfoil in arbitrary
motion at low Reynolds number
The flow filed around the airfoils in ups-downs motion, the airfoils in
pitching motion and the airfoils in ups - downs /pitching combination motion
are simulated and the lift and trust characteristics are investigated,
respectively.
The influence of frequency, amplitude of airfoil motion is investigated
and some conclusion can be drawn from the computational results:
a) The airfoil in symmetric ups- downs motion can produce only thrust
b) In the asymmetric ups-downs motion of flap, the larger frequency up
and lower frequency down of airfoil can produce significant lift
c) The mean angle of attack of pitching airfoil has an great effect on the
airfoil’s average lift
d) In ups - downs /pitching combination motion of airfoils, the most
favorable aerodynamic characteristics is achieved when the phasing
between the pitching and ups - downs motion is approximate 90
degrees.
Study on Principle of Flapping Mechanism
Type 1
This Flapping Mechanism can insure the symmetry of two flapping wings in flapping motion, but it is more complicated and heavier.
Type 2
The less components lead to lighter weight.
The motion of flapping wings is asymmetric, but it shows no problem in practical flight test, because of the high frequency .
Type 3
designed to make the flapping motion be symmetrical
Most simple and light
Be of great potential to study further
3 Fix-wing MAVs developed in NPU
developed more than 14 different Fix-wing MAVs
maximum dimension from 40cm to 20cm
flight endurance from less than 3min to more than 15min.
Some of them can carry color video camera and transmit
images of the objects back to the ground station.
Pictures Max. Dimension Weight Flight Time Payload
40cm 136.4g Above 15min 10g
40cm 128g Above 15min 10g
35cm 86.4g Above 5min 10g
35cm 80.5g Above 5min 10g
The specifications of the Fix-Wing MAVs.
Pictures Max. Dimension Weight Flight Time Payload
30cm 75.3g Above 5min 10g
25cm 145g Above 8 10g
24.5cm 65.5g Above 5min 10g
20cm 74g Above 3min -
20cm 68.5 Above 5min 10g
To demonstrate the developed the Fix-wing MAVs prototypes, a large amount of flight tests have been done.
Wind Tunnel
In NPU, a Low Turbulent Flow Wind Tunnel (LTFWT) has being built to research low Reynolds number flow characteristics of MAVs.
Test model of a flexible fixed-wing MAV
4 Wing Tunnel and Some Special Test Tools
lift-to-drag ratio curve lift coefficient curve
drag coefficient curve
Some special test equipments and manufacture tools
force and moment test table ofthe motor/ propeller combination
center of gravity measurement instrument
inertia measurement apparatus
laser cutting tool
Thanks a lot !