Recent and Future Research for Bird-like Flapping MAVs of NPU

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Recent and Future Research for Bird-like Flapping
MAVs of NPU
Prof. B.F.Song
Aeronautics School of Northwestern Polytechnical
University
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Main point

• Introduction
• Summary of PY-1
• Some Research Developments in Flapping Wings
  Aerodynamics and Mechanism
• Fix-wing MAVs developed in NPU
• Wing Tunnel and Some Special Test Tools

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0 Introduction

• In 2000, a research team in NPU (Northwestern
  Polytechnical 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.

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The parameters of PY-1
wing span 100
cm weight 280
g cruise time no
less than 12 min flight speed
5-15m/s mission equipment weight
20 g flapping frequency 510
Hz flapping angle 64 deg
power
motor polymer
A clear image about ground objects has obtained
by the colour video camera on-board.
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• 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.

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our research plan for flapping wings with no more
than 50 cm and the problems to be solved
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1 Summary of PY-1
PY-1 prototype
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Aerodynamic Characteristics
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.
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• Some aerodynamic characteristics of PY-1

(a)
(b)
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(c)
(d)
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• Flapping Mechanism System

principle and prototype of flapping mechanism
system
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• Fabrication and Flight test

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• 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
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PY-1 in flight
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• Some Research Developments in Flapping Wings
• Aerodynamics and Mechanism

• Aerodynamics

• Aerodynamic Performance Prediction System of
  Flapping Wing (APPSFW)

• according to J.D.Delauriers 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

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• 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

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• 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.

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• 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 Navier-Stokes equations at
  low Reynolds is solved. The flow field around a
  rectangular wing and NACA0006 cross section in
  the motion of flap and twist is calculated.

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• 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

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• 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 airfoils 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.

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• 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.
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• 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 .
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• Type 3

designed to make the flapping motion be
symmetrical Most simple and light Be of great
potential to study further
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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.

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• The specifications of the Fix-Wing MAVs.

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
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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
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• To demonstrate the developed the Fix-wing MAVs
  prototypes, a large amount of flight tests have
  been done.

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4 Wing Tunnel and Some Special Test Tools

• 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
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lift-to-drag ratio curve
lift coefficient curve
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drag coefficient curve
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• Some special test equipments and manufacture
  tools

force and moment test table of the motor/
propeller combination
center of gravity measurement instrument
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inertia measurement apparatus
laser cutting tool
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Thanks a lot !