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Bionic Ankle

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.

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Bionic Ankle

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  1. Bionic Ankle Bionic Ankle Mario Liuzza | Chris Loughnane | Ashley Pierce | Dan Spangler

  2. 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. And that’s only in the United States. “ 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 ” -

  3. Objective | Scope Scope To 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 Objective Develop an actively controlled below-knee (BK) prosthetic that minimizes knee damaging torque by improving upon contemporary standards for stability in varying terrain.

  4. Marketplace Ossur Vari-Flex No Control System Single Axis of Rotation Weight: 0.89 lb Capacity: 365 lb Ossur ProprioFoot Actively Controlled Single Axis of Rotation Weight: 2.7 lb Capacity: 250 lb College Park TruStep No control system Anatomically incorrect second axis of rotation Weight: 1.43 lb Capacity: 300lb College Park Trustep

  5. What is missing?

  6. Design Y Z Leg Member X Subtalar Actuator • High Ankle Actuator • Experiences loads of up to 700 N • High Ankle Member • 20º of dorsiflexion | 45º of plantar flexion • Subtalar Axis • Located 42° from the XZ plane and 23° from the XY plane. • Subtalar Member • 25-30° of inversion and 5-15° of eversion. Leaf Spring Foot

  7. Considerations

  8. Moment Analysis High Ankle Axis Subtalar Axis

  9. High Ankle Kinetics W Ry Rx COM COP Fx Fy

  10. Subtalar Kinetics

  11. FEA: Stress Max = 315 MPa

  12. FEA: Strain Max = 315 MPa Max = 0.1059%

  13. Material Selection Leg Member – 6061 Aluminum High Ankle – 6061 Aluminum Subtalar Member – 6061 Aluminum Leaf Spring – Spring Steel Foot Body – Delrin

  14. Control System Sensing Actuation Control

  15. Layout Options • 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 Strain Gauge • Measures the unbalance in foot member • Economical ($10-$100) • Half Wheatstone bridge Configuration

  16. LabVIEW Subtalar Retract Retract Extend Extend High Ankle LabVIEW Block Diagram Sensor Relationships Actuator Reaction

  17. Electric 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

  18. Pneumatics • Air Regulator • 3 Position Valves • Pneumatic Actuators • High Ankle: 7/8” Ø (60lbs Force @ 25 psi) • Subtalar: 9/16” Ø (25lbs Force @ 25 psi)

  19. Test Fixture Full Test Fixture Simplified Design

  20. Range of Motion

  21. Future 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

  22. Bionic Ankle Specials Thanks To: Professor Greg Kowalski Brian Weinberg Pat and the Northeast Automation Crew Jeff Doughty Kevin McCue John Doughty Questions?

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