DDR DorsiflexionAssisting Ankle Brace

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DDRDorsiflexion-Assisting Ankle Brace

• Andrea Albergo
• Thomas Burney
• Lauren Gallagher
• Alice Hammer
• Sheila Powenski
• Ben Yaffe

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Problem Statement

• Function Ankle Brace custom engineered for
  Jason Williams, which will aid dorsiflexion by
  exerting an upward force on the toes when desired
  and will simultaneously not hinder plantar
  flexion or other movement.
• Requirements
• Must resist natural tendency of the toe to slap
  the floor after heel strike
• Must simultaneously not hinder foots ability to
  push off the floor or other movement of the body
• Must be light weight (less than 2 lbs)
• Engineering Hurdles
• Must be durable under high speeds and thus high
  friction and wear
• Must have greater range of motion than brace of a
  normal patient with just a walking brace
• Must allow running, sprinting, and jumping, which
  all require different types of movement

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Product Design Specification

• Product Title
• Dorsiflexion-Assisting Ankle Brace
• Mission Statement
• We will design a ankle brace for Jason Williams
  that will help him run and train on the
  basketball court, through an assisted
  dorsiflexion and cushioned heel strike.
• Customer Needs
• Brace must resist the natural tendency of the toe
  to slap the floor after a heel strike.
• Full range of ankle motion
• Lightweight 2 lbs. or less
• Comfort

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Product Design Specification (cont.)

• Design Requirements
• Performance
• Durable cycle limit gt 106
• Non-Limiting must allow full plantar flexion
• Quick response must pull foot back before next
  step
• Safety
• No protruding parts that could easily get caught
  on other players
• Comfort
• Weight as low as possible
• Operating Environment
• Room temperature, 60-80 degrees Fahrenheit
• Repetitive, highly varying stress
• Service Life
• should last gt15 games/practices without needing
  replacement parts

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Product Design Specification (cont.)

• Competition
• No existing products that enable athletic
  performance in this type of brace.
• Intended Market
• Product designed specifically for Jason Williams,
  if successful the brace could possibly be a model
  for more versatile braces for non-athletic
  patients.
• Cost Prediction
• 150 - 250, plus occasional part replacement
  costs

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Material Selection
Current Material
Replacement Material
Properties of 351 Stainless Steel
Properties of 7075 (Air Craft) Aluminum

• Density 8.03 g/cc
• UTS 485 MPa
• YTS 205 MPa

• Density 2.81 g/cc
• UTS 505 Mpa
• YTS 435 Mpa
• Fatigue Strength 150 MPa (21800 psi)

In addition to the higher strength and reduced
weight of the Aluminum frame, it is easily
machined and relatively resistant to fatigue.
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TRIZ Chart
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TRIZ Recommendations

• 29. Use Pneumatic/Hydraulic Construction
• Solution - Use Rheonetic Magnetic Fluid inside a
  spring to control stiffness of spring for
  different movements and positions of foot

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Triz Recommendations Cont.

• 27. Inexpensive Short-life Object instead of an
  Expensive Durable One
• Solution - For parts that may wear easily, such
  as small springs, pivot joints, or ball-bearings,
  use inexpensive ones, so that they can be
  replaced as often as every week, rather than
  trying to find a spring that will never wear out,
  but will be almost impossible to make.

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Triz Recommendations Cont.

• 40. Composite Materials 3. Local Quality
• Solution - For spring, instead of using just one
  material with one spring stiffness, use a spring
  with varying materials as you go along the
  spring, to create a non-linear spring with
  varying spring constants depending on the amount
  the spring is extended or compressed

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Triz Recommendations Cont.

• 28. Replacement of a Mechanical System,
• 23. Feedback, 15. Dynamicity
• Solution Replace damper with an electrical
  sensor in toe and heel to indicate foot position
  and signal system to react depending on motion of
  person

Micro sensors
Mini sensors
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QFD
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Pugh Decision Matrix
Score BBetter, WWorse, SSame
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Fabrication and Materials

• 7075 aircraft aluminum parts
• Lightweight
• Corrosion resistant
• Precision steel piano-wire springs
• Oil-impregnated bronze bearing parts
• Stainless steel ball bearings and axle

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Coulomb Damper

• Self lubricating
• SAE 841 impregnated bronze bearing parts
• Adjustable damping
• Set screw clamping system
• Easy to take apart and reassemble
• Stainless axle

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Ankle Joint

• Unrestricted dorsaflexion/ plantarflexion
• 60 of rotation
• Adjustable springs allow for preloading
• Reduced friction increases toe return speed
• Robust design crucial parts protected
• Mounted on outside of ankle

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Finite Element Analysis of Hammer

• Hot spot diagram shows vulnerable points at
  middle of rounds
• Maximum stress 150 psi
• Yield strength 15 ksi
• Factor of Safety 100