Handheld Spy Chopper

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Handheld Spy Chopper
Group 10 Chris Alexander Bryant
Barrenechea Wilther J. Merchan Shrirag Nair Jason
Ng David Wang
Published by Popular Science
Stevens Institute of Technology Oct 2nd, 2008 E
130
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Past Panel Concerns

• Material Selection
• Carbon Fiber
• Expensive
• Molding Issues
• Previous Project
• Reasons for Failure
• New improvements?

3
Issues with Last Years Design

• Restricted airflow-shell design
• Weight-roughly 2 lbs
• Similar RC helicopters with that motor weigh 7 oz
• Uniform Design
• Landing
• Lifting off
• Not enough thrust
• Controlling direction

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Weight Past and Present

• Past
• Batteries 5oz.
• Non-uniform fiberglass shell wood frame
• Motor gt ½ lb.
• Total wt. is an estimated 2 lb.
• Present
• Battery 1.52 oz
• Alternative shell/frame material
• Motor lt 4 oz.
• Total wt. will approximately be 8 oz!

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Battery Past and Present

• Past
• Flight Power Lithium Polymer (LiPo) 11.1 V,
  800mAh x 2
• Cost 33.99 each (67.98 total)
• 2.50 oz x 2 (5.00 oz total)
• 3.77 x 0.94 x 0.47
• 15 minutes flight time
• Present
• E-Flite LiPo 7.4V, 800mAh
• Cost 27.99
• 1.52 oz
• Size 2.7 x 1.18 x 0.573
• 15 minutes flight time

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Design Past and Present

• Past
• 14 diameter fiberglass shell
• gt2lb mass concentrated in center
• Two batteries
• Propeller size incorrect
• Restrictive air flow
• Stabilizer issues
• Present
• 4 x 3 tombstone shape foam shell
• 8 oz total weight
• 1 battery
• Larger Diameter propeller
• Open Air Design
• Address stabilizing issues early

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Theory Counter-Rotating Rotors

• Issues Counter rotating rotors address
• conservation of angular momentum
• the blades apply equal yet opposite torque to the
  body, causing the body to gain spin angular
  momentum in the other direction
• spinning in the opposite direction to that of the
  rotors
• dissymmetry of lift
• One side of the rotor blade travels fast
• One side of the rotor travels much slower
• Can enter a stall condition and fail to produce
  lift and flight instability.
• Size / Space
• Easier to balance
• Occupy less space

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Theory - Lift

• The lift of a wing is proportional to the amount
  of air diverted down times the downward velocity
  of that air.
• To increase lift
• Divert more airmass by increase foil size
• Increase downward airmass velocity by increasing
  angle of attack or increase speed of wing
• Restrictions
• Lift begins to decrease at an angle of attack of
  about 15 degrees.
• Force needed to bend the air gt Air viscosity, so
  airflow separates from wing

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Concept Matrix
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Material Decisions

• Past
• Fiberglass Shell
• Wooden Support Frame
• Composite Center Shaft and Blades
• Present
• Styrofoam Nose Cone
• Composite Frame
• Composite Center Shaft and Blades
• Decided against the use of carbon fiber due to
  the inability to easily mold shape

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Material Decisions Cont.
Pros Lightweight, Low Density, High Compressive
Strength, Fits in our Temperature Range
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Camera

• SPECIFICATIONS
• Camera and transmitter weight only 9 grams!
• Camera and transmitter size 15mm x 22mm x 32mm
  (5/8" x 7/8" x 1 1/4")
• Camera Lux lt3 _at_ f1.2
• Camera Auto Electronic Exposure of 1/60 to
  1/15000 sec. w/ Auto Gain White Balance
• Camera Signal to Noise Ratio gt48dB
• 365K (PAL) or 250K (NTSC) camera pixel resolution
  
• Wireless Transmission Range 150M (450 FEET),
  Line-Of-Sight
• Transmitter RF Output Power EC RTTE Compliant
• Receiver Video Input/Output 1Vp-p/75 ohm

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Audio

• Audio capabilities of the UAV have been abandoned
• Suitable device hard to find
• Short range lt100 ft
• Too large (Parabolic Microphone)
• Motor noise interference
• Wind interference
• Additional battery draw
• Needs additional channel

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Preliminary Design Specs

• Controller 2.4GHz DSM Radio Control
• At least 5 channel transmitter
• 2-cell 7.4V 800mAh Li-Po Battery
• 2 -180 Motor
• Coaxial, counter-rotating rotor blades
• Two Micro Servos
• 4-in-1 control unit - CCA
• Main Motor Proportional Mix
• Allows adjustment of mixing between main motors
• Aerodynamic Shell

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Design Whole Model
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Design Different Views
Side View
Front View
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Top View
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Design Counter-Rotating Propellers
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Design Swash Plate

• Known as cyclic pitch
• Allows the helicopter rotor to provide selective
  lift in any direction
• One fixed plate (bottom plate)
• Connected to 2 oscillating servos
• Adjusts the orientation of top plate
• Rotating Plate
• Connector to rotor
• Transfers the fixed plate changes to the
  propellers

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Calculations - Lift
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Calculations - Drag
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Drag Calculations Assumptions

• Air Density at 70 degrees F
• Chose rounded body for least drag
• Velocity determined from information on current
  RC helicopters

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Calculations - Thrust

• Momentum Theory is applied to calculate the
  expected thrust from the system.
• Drag component
• Non-uniform inflow is ignored (ideal)
• Tip losses
• Figures of merits reflect hover conditions.
• Suitable alternative to Blade Element Theory.

? density of air R rotor blade radius v
induced velocity T Thrust P Power required
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Thrust vs. Coaxial Rotor Blade Size
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Thrust produced via rotor

• Fixed pitch coaxial rotor
• RPM has control over altitude

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Phase 3 Preparations

• Revise and update budget
• More accurate pricing
• Cheaper cost due to design changes
• Analysis
• Airfoil
• Pitch
• Propeller diameter
• Weight Distribution
• Finalize Part Selection
• Controller, Motor, Battery, Servos, Propeller,
  Camera
• Vendor Selection