Design of a Solar-Powered Low Altitude Unmanned Aerial Vehicle

Conceptual Aircraft Design

Project Management

Team

UAV Design

Carlos Sanchez

Aerodynamics & Performance

Roberto Mendoza

Aerodynamics & Flight Dynamics

Jorge Escudero

Structures & Materials

Edwin Jurado Propulsion & CAD

Need Recognition & Quantification • UAV development history • Market demand

– $17.9 billion, next 10 years

• Need identification – Aerial surveillance – Student project testing – Research purposes

• Solutions for the need – UAV development

• Budgetary parameters – Affordable – Small

Problem Definition

• Design objective: – Develop an Unmanned Aerial Vehicle:

• Surveillance within 5 km from NMSU • Up to 1 kg of payload (electronic equipment) capability • At least 1 hour flight time • Maximum altitude of 3,000 m above sea level

• Design constraints

– Time – Budget – Legal – Personnel – Material Properties and Availability – Manufacturability

Requirements

Concept Development

System Design – Wing - Fuselage - Tail

Aerodynamics – Wing Airfoil Selection

Figure 10.s1223 airfoil

Figure 11.Fx 74-CL5-140 airfoil

Figure 12.LA2573A airfoil

Airfoil S1223 Fx 74-CL5-140 LA2573A

Max thickness (%) 12.1 14 13.7

Max camber (%) 8.7 9.9 3.2

Weight Criteria Airfoil 1 Airfoil 2 Airfoil 3

2 Lift 1 -1 0

1 Landing Drag -1 1 0

1 Take off Drag 1 1 0

2 Pitching moment -1 1 0

1 Overall Performance (0.06-0.14 Drag) -1 -1 0

1 Manufacturing 1 2 0

Total 0 3 0

Weight Criteria Airfoil 1 Airfoil 2 Airfoil 3

2 Lift 1 -1 0

1 Landing Drag -1 1 0

1 Take off Drag 1 1 0

2 Pitching moment -1 1 0

1 Overall Performance (0.02-0.04 Drag) 1 -1 0

1 Manufacturing 1 2 0

Total 2 3 0

Aerodynamics – Tail Airfoil Selection

Airfoil NACA 0008

Thickness (%) 8.0

Chamber (%) 0

Trailing Edge Angle (ᵒ) 14.2

Lower Flatness (%) 74.5

Leading edge radius (%) 2.2

Max CL 0.586

Max CL Angle (ᵒ) 11.0

Max L/D 23.164

Max L/D Angle (ᵒ) 3.0

Stall Angle (ᵒ) 9.0

Zero - Lift Angle (ᵒ) -3.0

Figure 19. NACA 0008 airfoil geometry

Table 3. NACA 0008 airfoil characteristics

Aerodynamics – Wing – Tail CAD

Wing CAD Design

Tail CAD design Tail CAD design

Elevator

Rudders

Aerodynamics – Coefficients

Aircraft lift coefficient at cruise Maximum lift coefficient

𝐶𝐿 =𝐿

𝑞∗𝑆𝑟𝑒𝑓= 0.805

Aircraft lift coefficient at take off

𝐶𝐿𝑡𝑎𝑘𝑒 𝑜𝑓𝑓 = 𝐶𝐿𝑚𝑎𝑥𝑉𝑠𝑡𝑎𝑙𝑙

𝑉𝑡𝑎𝑘𝑒 𝑜𝑓𝑓

2

= 0.6188

Aircraft drag coefficient at cruise

𝐶𝐷 = (CfcFFcQcSwetc)

Sref+ CDmisc + CDL&𝑃 +

𝐶𝐿2𝑐𝑟𝑢𝑖𝑠𝑒

𝜋𝑒𝐴𝑅= 0.0492

Total drag at take off

CDtake off = CDO +CL2take off

πeAR = (CfcFFcQcSwetc)

Sref+ CDmisc + CDL&𝑃 +

𝐶𝐿2𝑡𝑎𝑘𝑒 𝑜𝑓𝑓

𝜋𝑒𝐴𝑅= 0.0359

1.35

12

Stall angle

Figure 21. Lift coefficient vs angle of attack

1.35

12

Stall angle

Flight Dynamics – Static Stability

Center of gravity

Longitudinal Static Stability and Control

Directional Static Stability and Control

yaw roll

Flight Performance

Stall velocity

𝑉𝑠𝑡𝑎𝑙𝑙 =2𝑊

𝜌𝑆𝐶𝐿𝑚𝑎𝑥= 5.9 𝑚/𝑠

Take-off velocity

𝑉𝑡𝑎𝑘𝑒 𝑜𝑓𝑓=1.4*𝑉𝑠𝑡𝑎𝑙𝑙 = 8.25 𝑚/𝑠

Approach speed

𝑉𝑎𝑝𝑝𝑟𝑜𝑎𝑐ℎ = 1.3 ∗ 𝑉𝑠𝑡𝑎𝑙𝑙= 7.67 𝑚/𝑠

Fuselage Design & Materials

In this UAV the fuselage has to be able to hold a camera, two batteries,

the avionics, the engine, the wings which are connected to the tail boom

and the landing gear. In this UAV there are different combinations of

materials. The materials are composite materials like fiberglass, carbon

fiber, wood-plastic composite, and other kinds of materials like aluminum

alloy and PVC. Superlight balsa elements also are used to make the UAV.

Payload and Landing Gear

The payload is the total weight of passengers, crew, instruments, or equipment carried by an aircraft.

The landing gear must have 3 points of ground contact.

UAV structure design

• Materials chosen for this UAV:

– Balsa wood

– Plastic (PVC)

– Fiberglass

– Aluminum alloy

– Carbon fiber composite

Optional design of UAV

• Materials chosen for this optional design:

– Balsa wood

– Aluminum alloy

– Carbon fiber composite

Materials of the UAV

Material Durability Tensile Strength

@73 F Stiffness (E)

Method of

manufacture Total price

Aluminum sheet Very high 30,000 psi 70,000 MPa Forging Expensive

Balsa wood High 550 psi 10,000 MPa Adhesive Bonding Cheap

Plastics (PVC) Regular 7,000 psi 3,000 MPa Vacuum forming Cheap

Carbon fiber Very high 100,000 psi 50,000 MPa Epoxy Resin Very expensive

Fiber glass Very high 75,000 psi 40,000 MPa Epoxy Resin Expensive

Material Durability

Tensile

Strength

@73 F

Stiffness (E) Method of

manufacture Total price

Aluminum

sheet Very high 30,000 psi 70,000 MPa Forging Expensive

Balsa wood High 550 psi 10,000 MPa Adhesive

Bonding Cheap

Carbon fiber Very high 100,000 psi 50,000 MPa Epoxy Resin Very

expensive

Internal Structure of the UAV

Internal structure of the fuselage Internal structure of the wings

Propulsion System

• Brushed and Brushless motors

Advantages Disadvantages

Brushed

Low cost of construction

Replaceable brushes for

extended life

No controller is required for

fixed speeds

Does not require electronics

Works in extreme

environmental conditions

Periodic maintenance

Speed/torque is moderately flat

Poor heat dissipation

May cause electrical-magnetical

interference due to brush arcing

Lower speed range

Brushless

Electronic commutation based

on sensors

Less maintenance

High efficiency, no voltage drop

across brushes

Reduced size

High output power to size ratio

Higher speed range

Low electric noise generation

Higher cost of construction

Control is more complex and expensive

Electric controller is required to keep the

motor running, and it may be more

expensive than the motor itself

Section Volume (m3) Density (kg/m3) Mass (kg)

Fuselage skin 0.001109 800 0.8872

Fuselage carbon skin 0.000362 1700 0.6154

Fuselage internal structure 0.000517 800 0.4136

Wing internal structure 0.000281 800 0.2243888

Vertical and horizontal

stabilizers 0.000494 800 0.3952

Wing booms 0.000032 1600 0.0512

Booms 0.000368 1600 0.5888

Landing gear 0.000126 2700 0.3402

Total 3.5159888

Min Max

Wattage range (W) 546.93 703.2

Minimum wattage: 546.93 W Maximum Wattage: 703.2 W Selected motor: Brushless outrunner

Himax Brushless Outrunner Motor W/ Cooling Fan HC3514-2900

5.5x4.5 Propeller

Technical Specifications

Weight 103g

Max Power 800W

Max RPM 40,000 RPM

Diameter 35.2mm

Length 38mm

Shaft Diameter 4.0mm

Mount Screws M3, max depth 5mm,

on 25mm, (1.0”) circle

Maximum Case

Temperature 65°C

Electrical Specifications

Kv 2900

Rm .0076

Efficient Operating

Current

25-80A, 90A Max 15

seconds

Actual device 3D Design

A-300 High-Performance Solar Cell By SunPower Corp.

Stored battery energy

(mA)

Time to empty the battery (min) Solar panel gained energy

(mA)

27,000 60 9,000

9,000 20 3,000

3,000 6.67 1,000

1,000 2.22 333.33

333.33 0.74 111.11

111.11 0.25 37.037

37.037 0.082 12.34

Total Time 89.96

Available area (m2) 0.2697

Cell area (m2) 0.015625

Number of cells 17.2608

Current per cell (mA) 540

Total current (mA) 9320.832

Total flight time: 90 minutes

Solar Panels on aircraft wings

Conclusion

• Our solution has complied with the initial requirements:

– The aircraft is small and buildable by students

– It is intended to have a low price of materials

– It surpasses the minimum flight time (60 min)

– It can carry the desired payload

– It can survey a range of 5 km