system requirements review - purdue university · the payload weight for the uav incorporates the...

AAE 451 – Aircraft Senior Design Spring 2007

Continuous Area Coverage via Fixed-Wing Unmanned Aerial

Systems

System Requirements Review

Team 3

Sumitero Darsono Charles Hagenbush

Keith Higdon Seung-il Kim Matt Lewis

Matt Richter Jeff Tippmann

Alex Zaubi

System Definition Review Team 3

Table of Contents Table of Content…………………………………………………………………………. 1

1. Executive Summary……………………………………………………………….... 2

2. System Requirement Review………………………………………………………3-5

2.1. Business Case………………………………………………………………….3

2.2. Target Market………………………………………………………………….4

2.3. Concept of Operation………………………………………………………….5

2.3.1. Military………………………………………………………………..5

2.3.2. Law Enforcement……………………………………………………...5

3. Payload and UAV Components………………………………….………………..6-10

3.1. Camera………………………………………………………………………6-8

3.2. Avionics……………………………………………………………………..8-9

3.3. Fuel Cells…………………………………………………………………..9-10

4. Powerplant……………………………………………………………………….11-17

4.1. Engine………………………………………………………………………..11

4.2. Propeller Selection………………………………………………………..11-17

5. Aircraft Sizing…………………………………………………………………...18-21

5.1. Constraint Diagram……………………………………………………….18-20

5.2. Current UAV Characteristic……………………………………………...20-21

6. Aircraft Concept Selection………………………………………………………22-27

6.1. Pugh concept selection method………………………………………………22

6.2. Design Criteria……………………………………………………………22-24

6.3. Evaluation………………………………………………………………...24-25

6.4. Hybrid Concepts………………………………………………………….26-27

6.5. Improvements on design……………………………………………………..27

7. Conclusion and Next Step…………………………………………………………...28

8. Reference……………………………………………………………………………29

9. Appendix………………………………………………………………………...30-32

Page 1


1. Executive Summary Unmanned Aerial Vehicles (UAVs) are remotely piloted or self-piloted aircraft that carry

specific payloads such as cameras, sensors, communications and other equipments during

a mission to perform specific task. This includes forward reconnaissance and

surveillance. The Department of Defense (DoD) has classified the UAV into seven main

categories, the Pioneer, Tactical UAV, Joint Tactical UAV, Medium Altitude Endurance

UAV, High Altitude Endurance UAV, Tactical Control System and the Micro Unmanned

Aerial Vehicles9.

Currently, there are large numbers of UAVs available in the market. However, the

availability of a UAV that is small, light, portable, cheap, and that is able to provide an

endurance of greater than four hours is very limited. This project aims to explore the

small UAV market for military and law enforcement and to provide an unmanned aerial

system that is more capable than those that exist in the current market.

Throughout the initial trade studies and aircraft sizing, the approximate weight of the

UAV is 10 lbs with endurance of approximately four hours. The dimension of the UAV

will be small enough such that it can be stored inside a Humvee or a police car. The

UAV must also be hand launched to allow for rapid deployment in case of emergency. In

addition, the UAV will be powered by a fuel cell and carry a small thermal imaging

camera for forward reconnaissance.

The concept generation and evaluation of the UAV is developed from the Pugh’s Method.

The evaluation involved several different configurations of the UAV based on its ability

to perform the design requirement of the project. The resultant design is the integration

of all the different configurations into one optimum design. Future work for the project

includes validation of the aircraft sizing code, selecting an airfoil, determining the basic

structure layout and components placement, and estimation of the aircraft c.g. and static

margin.

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2. System Requirement Review

Mission Statement:

To provide a continuous aerial coverage using an UAS that is small, light, portable and

allows for rapid deployment

The business case of the UAV, target market, and the preliminary design concept and

parameters were part of the system requirement review. Based on the system

requirement review, the UAV design will feature small size, portability, light-weight, low

cost, and rapid deployment as the main criteria in the design mission.

2.1. Business Case

Currently, there are a large number of UAV available in the market. However, the idea

of a small UAV that is light, portable, cheap, and allow rapid deployment is something

that the market has yet to explore. The current UAVs available in the market either have

a limited endurance or larger size. The design of this UAV will solve both problems.

Figure 1.: Evolution XTS – L3 BAI Aerosystems

In order to provide continuous coverage, the unmanned aerial system (UAS) will consist

of a system of multiple aircraft and support equipment. They will work in conjunction to

provide continuous aerial coverage over the area within a five-mile radius. The aircraft

will house a small payload consisting of a video camera, a thermal imaging camera, or a

chemical detector. The aircraft will either have a module payload or will carry all of the

payload types simultaneously depending upon the final payload weight and the weight of

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the cameras. The aircraft itself will be a micro unmanned aerial vehicle (UAV) that can

be hand launched and carried in a military style backpack. The entire system will be

transportable by two or three people depending on the number of aircraft needed. The

support equipment is very limited and will consist of a small transmission unit and a

laptop to program waypoints and view the incoming video feeds. The aircraft and

transmission equipment will both be portable so that they can be used anywhere that

surveillance is necessary.

2.2. Target Market

The proposed system focuses on a surveillance market, which includes mainly military

and law enforcement personnel. The military will deploy the system UAS out of either a

backpack when on foot or out of a Humvee when traveling. The main uses for the UAS

by the military will be for surveillance around a temporary base or convoy or for forward

reconnaissance. Law enforcement will deploy the UAS out of the back of a squad car.

The main use for law enforcement will be for assessing a hazardous situation before

committing personnel or providing continuous surveillance of large groups.

Projected Budget for Procurement of Small UA Systems

05

10

152025

05 06 07 08 09

Fiscal Year

Bud

get (

$M)

Figure2.: Projected Budget for Procurement of Small UAS8

Since the beginning of the War on Terror, the market for small Unmanned Aerial

Systems for the military sector has grown dramatically. Due to advances in sensors,

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materials and batteries, the mission capabilities of small UAVs are ever increasing.

Combined with the changing scope of warfare, current small UA systems are seeing more

and more use in places such as Iraq and Afghanistan, and the United States military has

decided to invest substantially in similar systems. In addition, the Department of Defense

also planned to spend more than $20M on small UAV over the next three years (figure

2)8.

2.3. Concept of Operation

2.3.1. Military

Current unmanned vehicles of this size, the Dragon Eye and Raven for example, provide

simple “over the hill” type missions where they observe a target location for a few

minutes and then return; our system provides the capability to observe a location or

multiple locations for hours at a time. The system can be deployed with the infantry at

the squadron or platoon level. Similar to other systems of this size, the aircraft is simply

launched by hand and does not require a runway. In addition, the entire system: aircraft,

laptop, and supporting equipment would be transported via backpack or a small container

in a Humvee (refer to Appendix III).

2.3.2. Law Enforcement

Typically, police agencies can use the UAV to provide overhead surveillance in assessing

hazardous situations before committing personnel. Similar to the military, police officers

need to gather information on each mission before performing their actions. Usually, the

law enforcement personnel carry out these missions. However, placing a police officer in

a situation that is relatively unknown risky may jeopardize the police officer’s safety.

Currently, the alternative method is aerial surveillance provided by helicopter.

Helicopters are very expensive to buy and operate, require dedicated pilots, and their

availability is limited. Law enforcement agencies can use UAVs as a perfect substitute

for a helicopter in the aerial surveillance role.3

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3. Payload and UAV Components The payload weight for the UAV incorporates the sensor and communication equipment.

Looking at sensors of the low resolution type, these components typically have weights

around 2 – 4 lbs. The UAV will carry a system of visual and infrared cameras to provide

day and night surveillance. A study conducted on many visual and infrared cameras to

find the best set of cameras, communications package, and fuel cells. The selected

components have to be light but and capable of performing the designed mission.

Currently, the selected camera is the Photon OEM Core IR Camera with two lens option,

35 mm and 50 mm. For the avionics is the Advanced Miniature UAV, MP2128LRC,

Autopilots by Micro Pilots and the fuel will be the Protonex Procore fuel cell. The

current estimated of all the components weight can be seen from Table 1.

Component 35 mm

Lens

50 mm

Lens

Camera 0.275 lbs 0.275 lbs

Lens 0.470 lbs 0.560 lbs

Avionics 0.727 lbs 0.727 lbs

Fuel Cells 4.41 lbs 4.41 lbs

Total Weight 5.882 lbs 5.972 lbs Table 1: Current Estimate of UAV Component’s Weight

3.1. Camera5

For the aircraft payload, the limiting factor is the higher weight of the thermal imaging

camera. The camera, the Photon OEM Core IR camera, is a small, rugged thermal

imaging camera that is currently used in many micro unmanned aerial vehicles. The

camera is produced by FLIR systems and has 320 by 240 pixels resolution. The camera

updates 30 times a second, which produces continuous video to the human eye. The

camera fits the current needs of the aircraft being produced because of its small weight

and power consumption. The camera, without the lens, weighs about a quarter of a pound.

It also has a very small volume slightly less than eight cubic inches. The camera also has

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a power consumption of about 1.5 watts. This small power consumption will allow for

longer flight time. The camera can be seen in figure 3.

Figure 3.: the Photon OEM Core IR camera5

The camera has the option of multiple lenses to suit different purposes. For the purposes

of the aircrafts prescribed mission, the camera needs a resolution of greater than one pixel

for every two square feet. Table 2 shows the necessary lens focal length for the given

number of pixels per square foot.

Distance (ft) Dimension (ft) Resulting Pixels Focal Length (mm)

2000 7 4 43

1500 5 4 46

1000 5 4 30 Table 2: Projected Results from the Camera5

From the data in Table 2 the aircraft will have two lens options of 35.0 mm or 50.0 mm.

The 35.0 mm lens operates well at altitudes of 1000 ft or less AGL. The 50.0 mm lens

will operate at altitudes of greater than 1000 ft and up to 2000 ft AGL. The 35.0 mm lens

has a horizontal field of view of 20 degrees and weighs .19 lbs giving a total camera

weight of .47 lbs. The 50.0 mm lens has a horizontal field of view of 14 degrees and

weighs .28 lbs giving a total camera weight of .56 lbs. The camera and lenses can be

seen in Figure 4.

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Figure4.: the Photon OEM Camera with Lenses

3.2. Avionics4

For the UAV to be able to perform the specify capabilities, it needs a controller for the

aircraft. Based on the design of the aircraft, the autopilot chips need to be light and

consume minimum power. Currently, there are several miniature UAV autopilot

controllers available on the market. Based on the mission criteria of the UAV, the

autopilot chips must be able to perform both the autonomous flight using the GPS and the

manual control flight.

The design of the autopilot chip comes with aluminum enclosures. With the enclosure

the weight of the component will be 0.727 lbs. With a volume of 38.5 inch3, it is small

enough to fit in inside the fuselage of the UAV design. However, it is under study that

the aluminum enclosure could possibly be replaced by composite material to reduce the

weight of the UAV.

Figure 5: The Micropilot UAV Chip Weight at 28 g (0.06lbs)4

The Advanced Miniature UAV, MP2128LRC, Autopilots by Micro Pilots is the world

smallest UAV autopilot currently available in the market. The chip only weighs 0.06 lbs

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(includes the GPS receiver) with an extremely low power requirement of 1 Watt. The

autopilot chip has the capability to perform GPS waypoint navigation while maintaining

constant altitude and airspeed. The autopilot can be controlled using three different

modes, autonomous flight using the GPS, manual control flight, and the emergency direct

servo control. The emergency direct servo control will be activated when the UAV loses

contact with the transmitter, and it will direct the UAV back to the starting or

predetermined location.

Figure 6: The Micropilot UAV Chip Weight at 28 g (0.06lbs)4

In addition, the transmitter has a range of more than 30 miles. This excess range of the

transmitter allows the UAV to operate in the urban environment without the need to

worry about the interference created by additional building.

Parameters Value

Weight 0.06 lbs

Weight with Aluminum Enclosures 0.727 lbs

Power Requirement 1 W

Volume 38.5 in3

Table 3: Specification for the Avionics4

3.3. Fuel Cells6

Based on preliminary trade studies performed in the System Requirements Review, the

UAV requires a power system with a power density beyond the range of current batteries.

This provides the necessary endurance and hand launch capability. Fuel cells have

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shown promise in providing these high power densities and are just now entering the

market. Protonex has developed the ProCore fuel cell system, which is specifically

tailored to miniature UAV applications. The fuel cell relies on sodium borohydride a

the fuel rather than hydrogen, which could be dangerous in a military UAV application

s

.

he specifications of the fuel cell are shown below in Table 4 and a picture of the product

Parameters Value

1

T

is shown in Figure 76.

Output Power 50-200 W

Output Voltage 20-30 V

Output Current 1 -10 Amps

Total Available Energy 770 W-h

Weight 2000 g (4.41 lbs)

Volume 170.8 in3

Table cations of Protonex ProC ll 4: Specifi ore Fuel Ce

Figure 7: Protonex ProCore Fuel Cell

s seen in, Table 4 this power system has an energy density of 335 W-h/kg, which is

A

well above the 200 W-h/kg that the best batteries can provide. The power and voltage

supplied by the ProCore system also appear to be sufficient to power the propulsion

system as well as the payload and avionics.

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4. Powerplant

tor was chosen on the constraints of most power for the least amount of

rom the necessary characteristics, a motor study was done from available remote control

4.2. Propeller Selection

ber of different aspects of the aircraft. It affects the thrust of

4.1. Motor1

The aircraft mo

weight. To improve efficiency characteristics such as a brushless motor and non-ferrite

magnets should be used. Because of the aircraft weight, the motor selection was limited

to motors with the ability to lift 10 lbs on take-off as well as low rpm motors so that a

gear box was not necessary to slow the motor rpm to a value that could be used to turn

the chosen propeller.

F

aircraft motors. Through the study, the best motor for the aircraft was chosen to be the

Model Motors AXI 4120/18 Gold Line. This motor is brushless and boasts neodymium

magnets that produce larger magnetic fields than ferrite magnets and thus more torque.

The motor can spin as fast as 9,000 rpm and has a maximum efficiency of 86%. The

motor is applicable to aircraft weighing 2 kg to 5 kg, which encompasses the current

aircraft weight. The motor can be seen in figure 8.

Figure 8: AXI4120/18 Goldline Engine1

The propeller affects a num

the aircraft, the speed of the aircraft, and the amount of power required from the fuel cell

in order to fly at a specific speed. The efficiency of the propeller also has a large affect

Page 11


on the range and endurance of an aircraft. Due to the small size of our aircraft, as well a

the desire to keep development and acquisition costs as low as possible, existing model

aircraft propellers became the focus of the selection process.

s

here are a number of different model aircraft propellers available, varying both in

ce

d

re

ce

two bladed propeller was chosen over three- or four- bladed propellers because of the

r

by the

conducting trade studies and analyses of different types of propeller geometry, several

T

geometry and material. There are several different types of materials such as wood,

aluminum, plastic, nylon, and composite material available in the current market. Sin

weight is a major consideration, choosing a lightweight propeller is of major importance.

The lightest propellers are made of nylon, and are very flexible, which would aid in

survivability on landing. However, the efficiency of a nylon propeller is very low, an

would not achieve the necessary flight performance in order to operate. Composite

propellers are both lightweight and efficient, but they are not very rugged and are mo

expensive than most other types of propellers. Aluminum propellers are efficient, but

very heavy. A plastic propeller is the best choice for our aircraft, as it has a good balan

of efficiency, low weight, and durability.

A

low power availability from the fuel cell. While the thrust produced by the propeller is

lower, the power required is significantly less. In addition to this, a tractor-type propelle

was chosen over a pusher. The reason for this is the increased efficiency of a tractor

propeller over a pusher propeller, because the airflow into a tractor propeller is

undisturbed, or “clean”. The airflow into a pusher propeller has been disturbed

wing and fuselage, so the efficiency of a pusher propeller is less than that of a tractor.

In

variables were considered. These variables were propeller rotation speed, flight velocity,

propeller pitch and diameter, thrust provided, power consumed, and propeller efficiency.

Certain flight regimes and equipment place limitations on many of these variables, and

from these limitations, the propeller best suited to for the UAV can be selected. The two

flight regimes analyzed are takeoff and cruise/loiter. Takeoff is particularly important

due to the fact that the aircraft is hand-launched. This places minimum requirements on

Page 12


the initial velocity and thrust needed to successfully maintain flight after the UAV is

released. The cruise and loiter regime is important because the flight conditions there

determine the endurance of the aircraft, which is of major importance.

he takeoff regime requires a velocity of approximately 30 ft/s, or 20 mph, and the motor

of

r

9,

ometry

T

operates at a rotational speed of 9000 rpm. This is a reasonable speed at which to expect

the person hand-launching the aircraft to throw it. In order to maintain flight while

climbing to its operational altitude, the aircraft requires slightly more than 2 pounds

thrust. This is based on a thrust-to-weight ratio of .2. The maximum power available fo

use from the fuel cell is 200 W, and there are approximately 5 W of power required to

run the other onboard systems. This leaves a maximum available 195 W for use by the

motor. Using plots of velocity, efficiency, thrust and power, the operating areas are

obtained, and the best propeller geometry is chosen. These plots are given in Figure

with the design point marked on each graph. The curves on the plot are different

pitch/diameter ratios. The diameter is held constant at 10 inches, limited by the ge

of the airplane. If the propeller were larger, it would strike the ground on landing.

0 20 40 60 80 100 120 1400

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

V (ft/s)

η

Propeller Efficiency vs Velocity for Several Different Pitch/Diameter Ratios

P/D=0.9P/D=0.8P/D=0.7P/D=0.6P/D=0.5

Figure 9a. Propeller Velocity vs. Efficiency for Takeoff Regime

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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

0.5

1

1.5

2

2.5

3

3.5

4

η

Thru

st

Propeller Efficiency vs thrust for Several Different Pitch/Diameter Ratios

P/D=0.9P/D=0.8P/D=0.7P/D=0.6P/D=0.5

Figure 9b: Propeller Efficiency vs. Thrust for Takeoff Regime

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

50

100

150

200

250

300

η

P (w

att)

Propeller Efficiency vs Power for Several Different Pitch/Diameter Ratios

P/D=0.9P/D=0.8P/D=0.7P/D=0.6P/D=0.5

Figure 9c: Propeller Efficiency vs. Power Plot for Takeoff Regime

Page 14


he cruise regime requires a velocity of approximately 50 ft/s, or 34 mph, and a motor

T

rotation speed of 7000 rpm. According to the thrust matching principle for steady, level

flight, the thrust-to-weight ratio should be equal to the inverse of the lift-drag ratio. The

estimated lift-drag ratio for the aircraft is 15. The minimum required thrust-to-weight

ratio is then .067. The maximum available power is the same in this case as for takeoff,

though the aircraft requires more power during takeoff, so that is the limiting condition.

The plots for the cruise condition are given in Figure 10, with the operating point being

indicated. The propeller size is limited by the takeoff condition, so the operating point

simply reflects the point of operation at the previously selected pitch and diameter.

0 20 40 60 80 100 1200

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

V (ft/s)

η

Propeller Efficiency vs Velocity for Several Different Pitch/Diameter Ratios

P/D=0.9P/D=0.8P/D=0.7P/D=0.6P/D=0.5

Figure 10a: Propeller Velocity vs. Efficiency for Cruise Regime

Page 15


0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

0.5

1

1.5

2

2.5

η

Thru

st

Propeller Efficiency vs thrust for Several Different Pitch/Diameter Ratios

P/D=0.9P/D=0.8P/D=0.7P/D=0.6P/D=0.5

Figure 10b: Propeller Efficiency vs. Thrust for Cruise Regime

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

20

40

60

80

100

120

140

η

P (w

att)

Propeller Efficiency vs Power for Several Different Pitch/Diameter Ratios

P/D=0.9P/D=0.8P/D=0.7P/D=0.6P/D=0.5

Figure 10c. Propeller Efficiency vs. Power for Cruise Regime

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As can be seen from Figures 9 and 10, the chosen propeller has a pitch of 7 inches in

addition to the 10-inch diameter. A plastic propeller of these dimensions is readily

available from many different suppliers, costing approximately $3 – $5. Compared to the

overall cost of the aircraft, this is a small amount. The low cost also enables easy

replacement of any propeller that may be broken on landing.

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5. Aircraft Sizing 5.1. Constraint Diagram

After selecting an initial concept, the aircraft must meet the desired performance

capabilities specified by the customer or the concept of operations. Clearly, there are

many variables and factors that influence the performance of the aircraft, so a constraint

analysis is used to narrow down the choices to a specific region where further decisions

can be made. The constraint analysis is a graphical method that is based on specific

excess power, and plots the power to weight ratio as a function of the takeoff wing

loading. The main equation in the constraint analysis is given below as Equation 11,

⎪⎭

⎪⎬⎫

⎪⎩

⎪⎨⎧

++⎥⎥⎦

⎤

⎢⎢⎣

⎡⎟⎟⎠

⎞⎜⎜⎝

⎛+=

dtdV

gdtdh

VSW

qn

eARSWCqV

WP TO

TO

D

pTO

SL 111/

20 β

πβαηβ (1)

For this aircraft, the stall speed will also be a dominant constraint as it defines the speed

at which the aircraft must be thrown for takeoff. The wing loading for a specified stall

speed is given in Equation 2,

max2

21

LstallTO CVS

Wρ= (2)

To continue with the constraint analysis, the requirements of the customer and concept of

operations must be translated into terms that can be used in the above equation. The

following constraints were used to satisfy our specific requirements:

- climb at 200 ft/min at 20% above stall speed in order to clear any

obstacles near takeoff

- perform a 2-g turn at a speed of 30 knots in order to maneuver in urban

environments

- loiter at 30 knots

- accelerate at 0.35 ft/s2 at 10% above the stall speed

- stall speed must be less than 15.7 knots (18 mph) because that is the

speed required for hand-launching the aircraft

Page 18


The resulting constraint diagram is shown below in Figure 11, and the values chosen for

the unknown parameters in Equation 1 are shown in Table 5. Note that this constraint

diagram was done for sea level standard day conditions.

Figure 11: Constraint Diagram

Parameters Value

0.7 at Loiter Propeller Efficiency (ηp)

0.5 at Takeoff

CD0 0.02

CLmax 1.3

Efficiency factor (e) 0.8

Aspect Ratio (AR) 6

Fuel Fraction (β) 1 (electric power)

Thrust Lapse Rate (α) 1 (electric motor) Table 5: Parameters used in Constraint Analysis

Page 19


From the diagram in Figure 11, the design point is the intersection between the stall speed

constraint and the 2-g turn requirement, where the region above the 2-g turn constraint

and left of the stall speed constraint defines the design space. This sets the design point

at a power to weight ratio of approximately 15 W/lb and a wing loading of approximately

1.1 lb/ft2. As a sanity check, the target takeoff weight of the aircraft is 10 lbs, which,

from the constraint analysis, puts the power requirement at nearly 150 Watts, well below

the 200 Watts available from the chosen fuel cell2. It appears that the current design

point is a feasible solution that will allow the aircraft to meet the concept of operations;

however, should the parameters in Table 5 change significantly or additional

requirements arise, the constraint diagram will have to be revisited.

5.2. Current UAV Characteristic

The current design of the UAV depends on the mission that the UAV needs to perform.

Currently, the constraints for UAV characteristics are:

- For the aircraft to be able to be hand launched, the aircraft must launch at a speed

that is above the stall speed of the aircraft. To do this, the aircraft has to be small

and light weight. Currently, the estimated weight of the aircraft is 10 lbs.

- Endurance of the UAV will allow the aircraft to be deployed for a longer period.

This factor is limited by the battery, the amount of power available, and the

powerplant efficiency. Currently, the battery will allow the UAV to operate for

approximately 4 hours.

- Similar to endurance, the range of the UAV will be limited by the battery and the

power plant. In addition, the communication relay and avionics of the aircraft will

also affect the range. Since the CONOP of the UAV is to operate it near personnel

or a ground station, the range of 5 miles should be sufficient.

- Payload weight is determined by the weight of the camera, lenses and the avionics.

The selections of these three components have been completed and it is estimated

that the three components will weight approximately 1.395 lbs.

- A fuel cell will be used due to lower weight and provide higher energy density.

From the selected fuel cell, approximately 770 Watt-Hr will be available.

Page 20


Parameters Current

Value

Target Threshold Units

Weight 10 10 20 lbs

Endurance 3.5 4 4 hrs

Range 5 5 10 miles

Payloads Weight 1.395 2 4 lbs

Components Weight 5.972 6 6.5 lbs

Weight Fraction 0.4028 0.4 0.5 We/Wo Table 6: Current Estimated of the UAV Characteristic

Page 21


6. Aircraft Concept Selection Many current small UAV’s performing similar missions were looked at for ideas for

concept designs. Three designs, the AeroVironment Raven, Elbit Skylark IV, and L3

Evoution XTS each have unique characteristic. A successful design, and one to beat out

the market, needs to look at what each of those aircraft provide, include the positive

features and leave out the negative ones.

6.1. Pugh concept selection method

The team developed the UAV concept using Pugh’s Selection Method2. By having a

concept generation phase, many ideas can be created. With each design critiqued against

an existing UAV, the team developed a matrix to aid in the selection of the best design.

The matrix compares each design to the existing UAV by a set of design criteria. The

design criteria are set by the mission and operations of the aircraft. Most often, a second

iteration of Pugh’s method is performed. Hybrid designs are added into the second

iteration based on the key positive and negative features from the first iteration.

6.2. Design Criteria

6.2.1. Hand Launch Capabilities

Figure 12 – Hand launching of AeroVironment Raven

The AeroVironment Raven has a very well suited fuselage for a hand tossed aircraft as

can be seen in Figure 12. Just as the landing gear on an airplane is carefully placed, the

Page 22


fuselage must be able to be held and thrown at the takeoff speed. Also, any propellers

must also be placed in a spot which will not strike the throwers hand or arm.

.

6.2.2. Propeller Performance

The propeller performance of a pusher design is less efficient than the performance of a

tractor propeller7. Because the goal of this UAS is to provide longer coverage than

existing UAS’s, the plane needs to be as efficient as possible.

6.2.3. Crash Worthiness

The design requirement of having the plane land without landing gear makes the bottom

of the fuselage more rigid for harder landings. Any surface on the bottom of the fuselage

will be damage prone. Because the front is where the visual sensors need to be, a

replaceable cheap plastic cover will need to be placed over the visual camera as

protection.

6.2.4. Handling

In order to operate in an urban environment where other buildings obstruct the view and

streets turn very quickly, the UAV will need to have sufficient handling abilities. The

handling characteristics also need to be steady enough for an operator to control the

aircraft remotely when the occasion arises.

6.2.5. View from Sensor

Figure 13 - L3 Evolution XTS, side mounted camera

The sensor needs to be mounted in the front of the aircraft to provide the need viewing

capabilities. The view from the sensor of the Skylark has front and side capabilities,

allowing the operator to pan to his target of interest. However, the Evolution XTS and

Page 23


Raven have a fixed side mounted camera, allowing only one direction on the camera.

Another important feature to consider is when the camera is in the front, the target being

monitored becomes bigger rather than further away.

6.3 Evaluation

With the design criteria, each design was compared to the Skylark I.

Figure 14 - Elbit Systems Skylark I

Design Criteria 1 2 3 4 5 6 7 8Grip - E E - E - - -Stall Speed + E E E E E E EPropeller Performance - E E E - - - -Crash Worthiness - E - E + - - -Handling - E + E E + E +View from Sensor E E E + E - - E

Minus 4 0 0 1 1 4 4 3Plus 1 0 1 1 1 1 0 1Even 1 6 5 4 4 1 2 2

Table 7: Aircraft Concept Selection Comparison

Page 24


Figure 14: Aircraft Design Concept from top left to right: Concept #1 to 8

Page 25


6.4 Hybrid Concepts

Though some designs have more negative comparisons, a couple of the other positive

traits are merged into two hybrid concepts. The first hybrid takes Design 6 and improves

on the grip by making the fuselage taller, but keeps the dual propellers. The dual

propellers can be designed to survive a crash by keeping the blade out of the horizontal

plane when tilted. Though front propellers have greater risk, the increase in performance

is needed. However, if it is determined there is not enough power for one motor, then

two will be used.

V-Tail

SensorTwo Propellers

Detachable Wings

Detachable Figure 15: Hybrid Model of the UAV Design

The second hybrid design takes Design 2 and keeps the single propeller, sensor

placement, and fuselage shape. The conventional tail is replaced by a V-tail to improve

the handling characteristics and keep the tail surfaces safe from damage during landing.

The second design is the chosen concept for this UAV as propeller data shows one

propeller will be sufficient.

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V-Tail

SensorSingle Propeller Detachable Boom

Selected Concept

Detachable Wings

Figure 16: Selected Concept of the UAV Design

6.5 Improvements on design

The wing span, tail size, fuselage depth and height, boom length, and airfoil will change

the shape of the selected concept based on final sizing parameters and component layout.

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7. Conclusion and Next Step The design of the UAV that is small, light, low cost, and allows rapid deployment will

provide the military and law enforcement greater reconnaissance and surveillance

capability. Currently, the general concept of the UAV has been determined along with the

components of the UAV, including the camera, avionics, fuel cell, engine and the

propellers. In addition, preliminary constraints on the characteristics of the aircraft have

been determined from the constraint analysis.

As a next step, the team will further detail the dimensions and weights of the aircraft.

Further study on the aerodynamic of the aircraft including the airfoil selection, aircraft

drag polar, and aircraft performance will be performed. Work will also be put into the

basic structural layout, component placement, and the stability of the aircraft.

Page 28


8. Reference 1. AXI4120/xx. Model motors S.R.O.

http://www.modelmotors.cz/index.php?page=60&kategorie=4120

2. Clausing, Don. Total Quality Development. New York: ASME Press, 1994

3. “Law Enforcement UAVs”. Aeronautics Defense System Ltd. January 25, 2007.

http://www.aeronautics-sys.com/Index.asp?CategoryID=116&ArticleID=

280&Page=1

4. MicroPilot – World Leader in Small UAV Autopilot.

http://www.micropilot.com/index.htm

5. Photon OEM Core Camera. http://www.visioncom.co.il/m4_Thremal_Photon.asp

6. Protonex Technology Corporation. http://www.protonex.com/procoreuav.html.

7. Raymer P, Daniel. Aircraft Design: A Conceptual Approach.Blacksburg, Virginaia:

AIAA Education Series. 2006

8. “Unmanned Aerial Systems Roadmap 2005-2030,” Department of Defense, August

2005, pp 39-51.

9. Unmanned Aerial Vehicle (UAVs) – Military Aircraft . March 1, 2007. March 01,

2007 http://www.fas.org/irp/program/collect/uav.htm

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9. Appendix Appendix I: QFD

Page 30


Appendix II: UAV Database

Vehic

le N

am

eE

mpt

y W

eigh

t (lb

s)G

ross

W

eigh

t (lb

s)P

aylo

ad

Wei

ght (

lbs)

Max

imum

E

ndur

ance

(h

rs)

Cru

ise

Velo

city

Azim

uth

14.3

5.5

4.4

231

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S4.

994

7.19

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20.

7520

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Poin

ter F

QM

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994

82.

002

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ift -

Eye

3.96

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60.

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Jave

lin8.

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555

azi

mut 2

5.5

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4.4

265

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dro

ne

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22

6.6

1.5

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rosa

nde

419

.833

1124

24.3

Seas

can

24.2

533

.95

7.05

415

56.3

8M

KY

6635

.230

.82

67Lu

na X

-200

6644

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343

.73

Phan

tom

8850

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.04

356

.4M

KY2

132

57.2

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380

.5AP

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ini-

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uard

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104.

7220

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40.2

7Te

rn44

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125

29.9

25

75

Altit

ude

We/

w0

985

0.38

4630

000.

6942

1250

00.

6243

1400

00.

2813

3000

0.48

2898

40.

2778

984

0.70

0019

880

0.60

0016

000

0.71

4398

400.

5333

9800

0.66

6798

000.

5750

1312

00.

4333

985

0.63

6430

000.

8088

1000

00.

3590

Dak

ota

70.8

413

2.66

49.9

43.

412

6.58

515

000

0.53

40Fo

x Tx

264

143

665

56.4

1150

00.

5417

Futu

ra U

CAV

4415

433

1.1

195

984

0.28

57C

hacal 2

66165

444

173

9840

0.40

00M

K-1

05 F

lash

105.

619

859

.43

5010

000

0.53

33Vi

xen/

Hel

lfox

139.

719

9.54

49.9

44

6425

000.

7001

Page 31


Appendix III: Military CONOPS

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system requirements review - purdue university · the payload weight for the uav incorporates the...

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