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Bionic Ank le. Bionic Ankle. Mario Liuzza | Chris Loughnane | Ashley Pierce | Dan Spangler. Background and Need. Background & Need. Background and need. In 2002, more than 110,000 lower extremities were amputated . That’s more amputations than there are people in Cambridge. - PowerPoint PPT Presentation
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Mario Liuzza | Chris Loughnane | Ashley Pierce | Dan Spangler
Bionic AnkleBionic AnkleBionic Ankle
Background and need
The challenge for anyone devising a new ankle is to make one that has a good degree of flexion (i.e. one that makes it easy to walk up and down hills, rotate etc) whilst at the same time retaining enough support for the person using it to feel confident in its stability Amputee Forum Moderator, In response
to a query posed by the Bionic Ankle Group regarding the biggest complaints amputees have about their prosthetics
In 2002, more than 110,000 lower extremities were amputated.
That’s more amputations than there are people in Cambridge.
And that’s only in the United States.
Background and NeedBackground and NeedBackground & NeedBackground & Need
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Objective | ScopeObjective | Scope
ObjectiveDevelop an actively controlled below-knee (BK) prosthetic that minimizes knee
damaging torque by improving upon contemporary standards for stability in varying terrain.
ScopeTo develop the base technology that allows the user to achieve stability on a variety of terrain. As stability is achieved between heel strike and foot flat, this will be the focus
Ossur Vari-Flex No Control System Single Axis of Rotation Weight: 0.89 lb Capacity: 365 lb
Ossur ProprioFootActively Controlled
Single Axis of RotationWeight: 2.7 lb
Capacity: 250 lb
College Park TruStep No control system Anatomically incorrect second axis of rotation Weight: 1.43 lb Capacity: 300lbCollege Park Trustep
MarketplaceMarketplace
What is missing?What is missing?
Leg Member
High Ankle Actuator
• Experiences loads of up to 700 N
High Ankle Member
• 20º of dorsiflexion | 45º of plantar flexionSubtalar Axis
• Located 42° from the XZ plane and 23° from the XY plane.
Subtalar Actuator
Leaf Spring
Subtalar Member
• 25-30° of inversion and 5-15° of eversion.
Foot
DesignDesign
X
YZ
ConsiderationsConsiderations
High Ankle Axis
Subtalar Axis
Moment AnalysisMoment Analysis
Force Vector High Ankle
0
100
200
300
400
500
600
700
800
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45
Time (s)
Fo
rce (
N)
High Ankle KineticsHigh Ankle Kinetics
Ry
W
Rx
FxFy
COM
COP
xXXX maFRF
YYbYY maFWRF
IM o
Optimized ST Moment Arm of Normal Force
-1.5
-1
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Length of foot (0% = Heel, 100% = Toe)
Mo
men
t ar
m o
f n
orm
al f
orc
e ab
ou
t S
ub
tala
r A
xis
(in
)
After Initial Optimization
Current Prototype
Subtalar KineticsSubtalar Kinetics
Max = 315 MPa
FEA: StressFEA: Stress
Max = 315 MPa
Max = 0.1059%
FEA: StrainFEA: Strain
Material SelectionMaterial Selection
Foot Body – Delrin
Leaf Spring – Spring Steel
Subtalar Member – 6061 Aluminum
Leg Member – 6061 Aluminum
High Ankle – 6061 Aluminum
Control SystemControl System
SensingSensing ActuationActuation
ControlControl
Layout OptionsLayout Options
Strain Gauge• Measures the unbalance in foot member• Economical ($10-$100)• Half Wheatstone bridge Configuration
Pressure Pad:
•Dynamic force input
•Cost prohibitive ($10,000-$20,000).
Dynamic Force Transducer
•Measures constant pressure output
•Price ($400-$1000)
•Size can limited the array of sensors used
LabVIEWLabVIEW
Sensor Relationships Actuator Reaction
LabVIEW Block Diagram
Retract
Retract
Extend
Extend
Subtalar
High Ankle
Electric vs. Pneumatic ActuatorElectric vs. Pneumatic Actuator
Electric: -High Force or High Speed: Not Both-Support System: DC Power Source
Pneumatics:-High Force and Speed (at high PSI)-Support System: DC Power Source + Compressed Air
PneumaticsPneumatics
• Air Regulator
• 3 Position Valves
• Pneumatic Actuators– High Ankle: 7/8” Ø (60lbs Force @ 25 psi)– Subtalar: 9/16” Ø (25lbs Force @ 25 psi)
Test FixtureTest Fixture
Full Test Fixture
Simplified Design
Range of MotionRange of Motion
Future ImprovementsFuture Improvements
• Install Flow Controls for the Actuators • Implement More Sensors on the Bottom of the Foot• Smooth Out the Control Responses• Optimize Prosthetic Parameters• Consider the option of a PLC Board
Bionic AnkleBionic Ankle
Questions?
Specials Thanks To:
Professor Greg Kowalski Brian Weinberg
Pat and the Northeast Automation Crew Jeff Doughty
Kevin McCue John Doughty
