Micro Air Vehicle Senior Design team

Zach Kilcer, Bill Strong, Joe Olles, Sean Dittrich, Brian Stumper, Doug Brown

2

Introduction: MAV History

• 1996 DARPA initiative to develop a small unmanned aircraft for military applications.

• 1998 AeroVironment successful in launching the Black Widow. – six inches in linear

dimension – transmits video, GPS,

altitude, velocity and heading

3

Introduction: MAV Global View

• Government funding of large-scale development has ended.

• Possible private sector applications of MAV technology has kept interest alive.

• Research has continued to flourish at Universities around the world.– UF, UA, Notre Dame, Brigham Young

• Annual international competition to keep interest in the field strong.

4

Introduction: MAV at RIT

• Fourth year MAV Team at RIT

• Offshoot of the RIT Aero Design Team

• Current MAV Senior Design effort in support of MAV Team which competes annually.

5

Introduction: Current SD Goals

• Current senior design team will develop the 2005-06 propulsion system to be implemented in the 2005-06 airframe.

• Design will surpass previous design specs:– 80g thrust– 80.5g total weight– withstand the routine crash landings– sustain flight for 15 minutes– compatible with the future airframes/electrical

components – cross-over with 2005-06 winter/spring MAV team

6

Concepts for design

• Internal combustion Engine with a Propeller

• Jet Turbine Engine

• Variable Pitch Propeller

• Shrouded Propeller

• Ducted Propeller

7

Internal combustion Engine with a Propeller

• Loads of power (.27 horsepower @17000 rpm)

• No assembly or modification required

8

Jet Turbine Engine

• Produces large amount of thrust (13-50lbs)

• No assembly or modification required

9

Ducted Propeller

• Significantly increase thrust

• Reduce propeller tip vortices

• Increase durability of propulsion system

10

Variable Pitch Propeller

• Maximizes efficiency of the propeller blade at both cruise and takeoff

• Would be groundbreaking for an MAV

11

Shrouded Propeller

• Increase thrust and efficiency

• Reduce propeller tip vortices

• Increase durability of propulsion system

12

Concept Evaluation: Pugh Chart

Evaluation Chart

05 MAV Jet turbineInternal

combustion engine

Ducted PropShrouded

propVariable

Pitch Prop

Cost 0 - 0 - 0 -

weight 0 - - - - -

thrust 0 + + + + +

size 0 - - 0 0 0

durability 0 0 0 + + 0

drag 0 - - - 0 +

number of parts

0 - 0 - - -

ease of integration

0 - - + 0 -

Complexity of Design

0 - - 0 0 -

Total + 0 1 1 3 2 2

Total - 0 7 5 4 2 5

Sum 0 -6 -4 -1 0 -3

13

Pugh Evaluation rationale• In discounting the IC engine and the jet turbine, the

groups main focus was on the complexity of these designs.– Both designs will require some sort of controlled fuel delivery

system which will then need to be integrated to the propulsion system

• Variable pitch was also hit hard by complexity of design– The system will require miniaturized components that most likely

would not be located commercially– It would require additional powered components for movement

• All these systems would require excessive funds to produce, as well as put additional (excessive-IC/Jet) weight onto the airframe.

• Shrouded and ducted propellers seem to offer the best chance for an overall increase in thrust before propeller optimization

14

Design Concepts to be Explored

• Based on Results from Pugh Chart – 3 Designs

1.) Maximizing 2005 Design

2.) Shrouded Propeller

3.) Ducted Propeller

15

Maximizing 05 Design• Easy design to produce with the teams limited

resources

• New motor findings will increase performance

16

Propeller Slippage and Tip Vortices

• Propeller Slippage– Difference in Geometric and Effective Pitch

• Tip Vortices– tip vortices occur where the high pressure area of the

blade tries to invade the lower pressure area

17

Shrouded Propeller• Reduce tip vortices and increase performance of

a propeller• Increase durability of propulsion system• Easy design to produce with the teams limited

resources

18

Ducted Propeller• Reduce propeller tip vortices • Significantly increase thrust

– acts as a nozzle, raising the exit velocity • Increase durability of propulsion system• Equation for Open

and Ducted Props

openopenducted TTT 26.12 3

1

19

Feasibility Testing• Static Test Stand Will be Used to:

– Bench mark 2005 design– Effect of thrust by shrouding

• Difference should be losses due to tip vortices

– Prove thrust increase in ducted propeller

• Limited research available on small scale propulsion systems

20

Feasibility Testing

• Limited research available on small scale propulsion systems.

• Need to benchmark 05 design.

• Need to prove ducted propeller concept.

21

Test

• Test uses load cell to compute force of propulsion system

• Compare different concepts to each other-Thrust -Power Input -Drag

22

Test Matrix

Initial CalibrationParameters Unweighted 20g Static Load 50g Static Load 70g Static Load 100g Static LoadLoad Cell Supply Current (Amps)Load Cell Supply VoltageLoad Cell Output Voltage

TestingParameters 1/4 Throttle 1/2 Throttle 3/4 Throttle Full ThrottlePropulsion ConfigurationLoad Cell Supply CurrentLoad Cell Supply VoltageLoad Cell Output VoltageMotor Current Draw (Amps)RPM

Ambient Air TemperatureAmbient Air PressureAmbient Air Humidity

MAV Propulsion Static Load Test Matrix

Additional Parameters

23

Future Plans

• Narrow to one main design concept

• Optimize duct or shroud design

• Optimize propeller design– Manufactured or molded– Plastic or composite

• Electronics integration & optimization

24

Other Possible Features

• Custom Propeller Blades– Would provide superior efficiency, weight, and

durability– Requires custom built molds

25

Propeller Design

• Two main theories used to design propellers:– Inverse Methods– Momentum/Blade Element Theory

26

Inverse Methods

• Two Inverse methods to chose from:– First, based on the Prandtl-Betz Theory

• Starts with an optimal circulation distribution and relates chord and angle of attack for the best design case.

– Second, computes profiles from velocity distributions

• Based on propeller airfoil requirements• Tip requirements determined by compressible flow,

hub determined by viscous effects.

27

Momentum Theory

• Blade Element theory:– The airflow is treated as a

2D flow with no mutual interaction between blade sections.

– The blade is composed of independent elements

– The differential element of fixed chord, is located at a specific radius-chord changes with respect to radius

28

The Velocity Triangle

• The propeller blade does not only feel the effects of the upstream velocity, but also the velocity of rotation.

• This is accounted for in the velocity triangle where actual velocity seen is the square root of upstream velocity squared plus tangential velocity squared.

29

Velocity Considerations

• Since the foreward velocity of the MAV can be considered small compared to the rotational velocity of the propeller there isn’t much increase in velocity seen by the propeller

• Even though small, the increase must be accounted for or errors in thrust analysis will occur

30

Velocity Considerations

100.0000

150.0000

200.0000

250.0000

300.0000

350.0000

400.0000

450.0000

500.0000

0 10 20 30 40 50 60 70 80

Upstream Velocity (ft/s)

Ex

pe

rie

nc

ed

Ve

loc

ity

(ft

/s)

1 in radius 2 in radius 3 in radius

31

Reynolds Number Considerations

• As the radius is increased, the Reynolds Number curve grows steeper

• Moving outward from the hub, Reynolds Number increases linearly

32

Reynolds Number Considerations

0.00E+00

2.00E+06

4.00E+06

6.00E+06

8.00E+06

1.00E+07

1.20E+07

1.40E+07

1.60E+07

0 0.1 0.2 0.3 0.4 0.5 0.6

Chord (in)

Re

yn

old

s N

um

be

r

1 in radius 2 in radius 3 in radius

33

Electronic Considerations – Electric Motor

• Electronic Motor includes three (3) types:– Brushed– Brushless– Coreless

• Selection Criteria– Weight– Current– Thrust– Propeller configuration

• Optimize using gathered data given propeller specifications.

Coreless DC Motor

Brushless DC Motor

Brushed DC Motor

Average Thrust @ 7.4V vs Maximum Current

Thrust = 32.982(i) + 47.252

R2 = 0.9863

0

100

200

300

400

500

600

700

0 2 4 6 8 10 12 14 16

Maximum Current (Amps)

Av

era

ge

Th

rus

t (g

ram

s)

34

Electronic Considerations - Battery

• LiPoly Batteries will provide the necessary power for all of the onboard electronics (present and future).

• LiPoly chosen over nickel metal-hydride (NiMH) and nickel-cadmium (NiCad) for high charge density

• Optimal battery selection by using the charts below

Current Rating vs. Mass for Different Single Cell (3.7V) Lithium Polymer Batteries

i = 0.1565(m) + 0.3209

R2 = 0.9288

0

1

2

3

4

5

6

7

8

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0

Weight (Grams)

Cu

rre

nt

Ra

tin

g (

Am

ps

)

LiPoly Batteries

Lifetime vs. Mass for Different Single Cell (3.7V) Lithium Polymer Batteries

tlif e = 48.195(m) - 21.067

R2 = 0.9745

0

500

1000

1500

2000

2500

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0

Weight (Grams)

Lif

eti

me

(m

Ah

)

35

Electronic Considerations – Control System

• Control System includes two (2) components:– RF receiver– Speed controller

• Selection Criteria– Number of channels– Compatibility with existing

RF transmitters– Size– weight– Range– Motor compatibility

Speed Controller

RF Receiver

RF Transmitter

Electronic Subsystem

Primary Electronics

• RF Transmitter• RF Receiver• Battery• Electric Motor• Speed Controller

Future Electronics

• Servo Motors• Video Camera• Video Transmitter• Video Receiver

RF ReceiverSpeed

Controller

VideoTransmitter

Servo Motors

ElectronicMotor

RF Transmitter

Control System

BatteryVideo

Receiver

VideoCamera

RF ReceiverSpeed

Controller

VideoTransmitter

Servo Motors

ElectronicMotor

RF Transmitter

Control System

BatteryVideo

Receiver

VideoCamera

Block Diagram of MAV Electronic System

37

Electronic Considerations – Future Requirements

• Future Technology:– Two (2) servo motors– A video surveillance

system

• Considerations– Weight– Dimensions– Power requirements

Video Camera Video Transmitter

Video Receiver Servo Motor

38

Future Plans

• Narrow to one main design concept

• Communicate interface points with the MAV club

• Select and purchase components

• Build and test design

• Use results for further optimization

• Evaluate the performance of design