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P13002: Ankle-Foot Orthotic Un-Tethered, Mechanical

P13002: Ankle-Foot Orthotic Un-Tethered, Mechanical. System Design Review. The Team. Team Members: Pattie Schiotis – Team Manager (ME) Shane Reardon – Lead Engineer (ME) Dana Kjolner (EE) Robert Ellsworth (EE) Sam Hosig (CE) John Williams (CE) Faculty Guide: Dr. DeBartolo. Agenda.

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P13002: Ankle-Foot Orthotic Un-Tethered, Mechanical

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  1. P13002: Ankle-Foot Orthotic Un-Tethered, Mechanical System Design Review

  2. The Team • Team Members: • Pattie Schiotis – Team Manager (ME) • Shane Reardon – Lead Engineer (ME) • Dana Kjolner (EE) • Robert Ellsworth (EE) • Sam Hosig (CE) • John Williams (CE) • Faculty Guide: Dr. DeBartolo

  3. Agenda • Introduction • Work Breakdown Structure • Customer Needs • Engineering Specifications • Functional Decomposition • Concepts • Component Benchmarking • Risk Assessment • MSD I Project Plan

  4. Project Background • Lasting side effect of a stroke: foot drop • Inability to dorsiflex the foot • Ankle Foot Orthotics (AFOs) currently used to aid dorsi-flexion. • Passive devices don’t allow for movement when walking on ramps and stairs • Foot is always pointed upwards

  5. Assumptions & Constraints • User will have no ability to either plantar-flex or dorsi-flex their foot • Side to side stability of the foot will be ignored • Worst case will be analyzed: • 95 percentile male having heavy foot. • Fast walker – gait cycle less than 1 second. • Device may not use air muscles as an actuation source

  6. Work Breakdown Structure

  7. Key Customer Needs • Safety • Portable • Lasts all day without charging/refueling • Lightweight • Tolerable to wear all day • Reliable • Accommodates Flat Terrain • Accommodates Special Terrain • Stairs • Ramps • Obstacles • Comfortable • Aesthetically Pleasing • Durable • Water Resistant • Corrosion Resistant • Salt & Environment • Biocompatibility • Convenient • Easy to put on and take off Primary Needs: Secondary Needs:

  8. Key Engineering Specifications

  9. Functional Decomposition

  10. Concept Generation Table

  11. Design Option 1 • Mechanical Locking MethodUses a solenoid to unlock theheel which allows the foot todrop.

  12. Design Option 1 • Mechanical Locking Method • Mechanically restrict the foot from dorsi/plantar flexing while in the air. • Use gravity to help the foot plantar-flex as needed (stairs/ramps) • Methods: • Use a solenoid to unlock the heel which allows the foot to drop. • Use a brake to unlock the heel which allows the foot to drop. • Ratcheting Device attached to ankle

  13. Design Option 2 • Active Actuation • Uses a linear actuator to force the foot into the proper position. • Methods: • Solenoid • Piezoelectric • Power Screw • Hybrid • Power Screw with electric motor

  14. Design Option 3 • Hard StopTwo preset distances can be moved back and forth using a servo motor and screw.

  15. Preliminary Calculations • Anthropometric Data for male, 95 percentile: • Stature=1.868 m • Foot Weight=1.4 kg Fw 42% 0.152H If our actuator is 1.5” (3.3 cm) behind ankle joint:

  16. Calculations Continued Dorsi-flexion: θ=20° Plantar-flexion: Total stroke=3.61 cm In 0.4s, we need 9 cm/s

  17. Active Actuation Sources

  18. Pros and Cons

  19. Concept Selection Matrix

  20. System Component: Sensors • Bounces infrared light off terrain to determine distance • 10 cm to 80 cm range • Worst case power consumption per sensor is 0.00176 kWhr • Output from -0.3 to +0.3 volts • Highly accurate within operational ranges • Low cost (~$15) • https://www.sparkfun.com/products/242

  21. IR Distance and Terrain Type Sensor A Sensor B Terrain

  22. Sensor Calibration • Nonlinear response • Reflective ratio of materials is mostly irrelevant • Static position • Concerns about irregular terrain types • https://www.sparkfun.com/products/242

  23. Current Code: Developed by Chappy • Predicts what type of terrain we are walking on • Calculates where in the gait cycle we are • Has some modeling that improves performance of predictions NEED TO CHANGE • Need to be able to fully implement in C • Error checking for invalid states • Nothing is done at run-time

  24. System Component: Micro Controller

  25. System Component: Micro Controller • Micro controller needs: • Interface with two IR sensors and possible angle senor • ADC • Control actuation method • PMW or Digital I/O • Other considerations • Must run on battery power for at least 8 hours • Must be able to simulate system in “real time” • Must be able to fit on orthotic • Must be able to export data to sd card if needed

  26. Power Consumption

  27. Risk Assessment

  28. Project Plan

  29. Closing Remarks/Comments • Scope of project is to design a modified AFO that includes: • Energy storage medium • Foot rotation device • Terrain sensing system • Microcontroller • We will focus on a detailed design following the “Mechanical Locking Mechanism” concept.

  30. Questions?

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