UAV Research International

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UAV Research International

• Providing integrated consultation to MAV project
  engineers at Eglin AFB
• Chris McGrath
• Neil Graham
• Alex von Oetinger
• John Dascomb
• Sponsor
• Dr. Gregg Abate
• April 6, 2006

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Overview

• Problem Statement
• Design Specifications
• Design Solution
• Scale Model Design/Fabrication
• Testing

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Problem Statement

• To design a means of characterizing MAV handling
  during flight
• Test must be repeatable
• Data must be collected to characterize the MAV

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Project Specifications

• Weight ? 100 200 grams (g)
• Flight Speed ? 0 25 meters per second (m/s)
• Exterior Material ? Carbon Fiber Composite
• Wing Tip Length ? 15 30 centimeters (cm)
• MAV Flight Control ? Both 2 and 3 axis
• Type of Thrust ? Pusher, Puller, None

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Design SelectionFree Flight Wind Tunnel

• The free flight wind tunnel has been successfully
  created before
• Design is a conventional wind tunnel with
  unobstructed test section
• Relative velocity of MAV to the ground is zero

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MAV Handling Initial Set-up
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MAV HandlingReel and Restraint Set-up
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Wind Tunnel Design

• In wind tunnel design Three properties are most
  important to consider
• Tunnel geometry
• Flow quality
• Fan Selection

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Wind Tunnel Design
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Wind Tunnel GeometryTest section Dimensions

• For the minimum analysis of the flight, the MAV
  needs to move laterally or vertically twice its
  wingspan
• Minimum cross section for 12 wingspan is 4.5 ft
  x 4.5 ft
• Allow ten feet for longitudinal motion

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Wind Tunnel Geometry
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Wind Tunnel Geometry1st Diffuser

• Expands the ducting from area of test section to
  the area of the fan
• Diffuser angle

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Wind Tunnel Geometry
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Wind Tunnel DesignTurns 1 and 2

• Corner Vanes assist flow around the 4 90 degree
  turns
• Corner Vanes improve efficiency by decreasing
  pressure loss
• Even with vanes 61 of all pressure loss occurs
  at the 1st two turns

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Wind Tunnel Geometry
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Wind Tunnel Design Fan Selection

• Fan selection based on volume flow rate and
  static pressure loss in tunnel
• Volume flow rate at maximum of 25 m/s is 100000
  CFM
• Total pressure loss in tunnel 600 Pa

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Wind Tunnel Design Fan Selection

• Howden Buffalo 54-26 series fan
• Fan has a 54 in diameter, and a 125 HP motor

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Wind Tunnel Design Flow Quality

• Motor housing
• Anti-swirl vanes

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Wind Tunnel Geometry
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Wind Tunnel Geometry 2nd Diffuser, Turns 3 and 4

• Diffuser increases area final area ratio of 6
• Final area ratio is most important factor in
  tunnel
• Turning vanes keep flow as laminar as possible

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Wind Tunnel Geometry
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Wind Tunnel Design Flow Quality

• Honeycombs - remove lateral components of
  turbulence
• 3 Screens remove axial components of turbulence

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Wind Tunnel Geometry Contraction Cone

• Contraction cone quickly increases flow velocity
• When condensing, flow will not separate like
  diffuser

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Wind Tunnel Geometry Tunnel Geometry
Constrained tunnel
Total tunnel length is 36.6 ft
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Instrumentation

• On-Board Measurement
• Flow Quality Measurement
• Traversing System
• Data Collection Software
• Data Acquisition System

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On-Board Measurement

• Kestrel Autopilot
• 16.65 grams (2 x 1.37 x .47)
• Three-axis rate gyros
• Accelerometers
• Air pressure sensors

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Data Collection Software

• Virtual Cockpit
• Labview

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Cost Analysis
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Scale Model

• Too expensive to build the designed tunnel
• Built a 1/12 scale model
• Physically test flow quality of full scale design
  to determine if free flight is feasible

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Scale Effects

• Scale model Reynolds number 1/12 that of full
  scale model
• Use hot-wire Anemometer to measure velocity
  fluctuation though test section
• Velocity is not dependent on Reynolds number,
  scaling effects can be ignored for our tests

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Scale Model
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Contraction Cone
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Contraction Cone
Total Elapsed Time
2 Hours
20 Hours
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Contraction Cone
Total Elapsed Time 41 Hours
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Contraction Cone
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Joining Method
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Turning Vanes
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Diffusers
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Settling Chamber
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Fan
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Model Results

• Manufacturing Complete
• Testing
• Initial correction of flow through turning vanes
• Inconclusive analysis of tunnel due to lack of
  testing
• Potential Testing
• Fine tune internal geometry
• Correction of all Turning vanes
• Measuring Pressure fluctuations through test
  section

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Problems Encountered

• Wait time on ordered parts
• MSC acrylic sheets
• McMaster-Carr fan order
• Fabrication of contraction cone
• Testing Time Constraints

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Questions?