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 !