1 / 43

Active Ankle-Foot Orthotic

Active Ankle-Foot Orthotic. Team P13001 Nathan Couper, ME Bob Day, ME Patrick Renahan, IE Patrick Streeter, ME. Air Muscle Tethered.

xena
Download Presentation

Active Ankle-Foot Orthotic

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Active Ankle-Foot Orthotic Team P13001 Nathan Couper, ME Bob Day, ME Patrick Renahan, IE Patrick Streeter, ME Air Muscle Tethered This material is based upon work supported by the National Science Foundation under Award No. BES-0527358. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation.

  2. Agenda • Assumptions • Customer Needs • Engineering Specifications • Test Plan • Mechanical Analysis • Proximal Attachment • Static Analysis • Fatigue Analysis • Distal Attachment • Static Analysis • Fatigue Analysis • Air Muscle Testing • Transient Flow • Muscle Contractions • Risk Assessment • Proposed Schedule • Questions and Criticism

  3. Assumptions and Project Scope • Patient maintains zero muscle control over dorsi-flexion, plantar-flexion, and toe extension • This product is designed to be used on a treadmill in a clinical setting; but can be incorporated into an aquatic setting • Tethered System • The elastomer can be adjusted on a patient basis so that when the patient’s full weight is applied on the AFO, the foot rests at angle slightly above 90 degrees with respect to the patient’s lower limb • Designed patient has the ability to use a dorsi-flex assist AFO without receiving tone-lock spasms • For calculations: • Anthropometric Data is from the ANSUR (military) Database • Based on the 50th percentile man • 2D system • no resistive forces/friction associated with the joints • a normal gait cycle time of 1.2 to 1.5 steps per second is assumed • Isotropic, Elastic Materials

  4. Customer Needs

  5. Engineering Specs *Nominal value represents the initial target value for specifications. **Ideal value represents the adjusted target value for specifications based on research and adjusted objectives.

  6. Engineering Specs

  7. Engineering Specs

  8. Testing Plan – Required Tests

  9. Testing Plan – Required Equipment

  10. Gait Analysis Based on 88 cycles per minute: 0.30 seconds from foot off to foot strike.

  11. Assumed AFO Design • Designs based around AFO of this structure • Design is flexible so it will be able to work on many different AFO designs and shapes • Assumed material =

  12. Proximal Muscle Attachment • Relatively simple components • Low Profile • Strong • Removable • Key Components: • Weld Nut • Exterior threading for nut • Secures device to AFO • Screw clamps air inlet and muscle attachment to weld nut • Nozzle screws into block

  13. Weld Nut • Uses 5/16” Nut to secure against AFO • Note external threads not shown • 316 Stainless Steel • Allows for easy removal of device • Stress Calculations: • Treated like a cantilever beam • 130 N force (Max force air muscle can apply) • Max Bending Stress: 57.45 Mpa • Shear Stress: 7.49 MPa

  14. Proximal Anchor and Air Inlet • Houses weld nut and exterior nut • Applies force on weld nut • Also clamped on by ¼-20 screw • 1/4-inch air inlet channel • Threaded hole for nozzle insertion • 316 Stainless Steel

  15. Proximal Anchor and Air Inlet Element Type: Solid 10node187 (tetrahedral) Max Stress: 45 MPa

  16. Proximal Anchor and Air Inlet All displacement is about 0 meters

  17. Nozzle • Proposed Materials: Delrin or Stainless Steel • Threading • External Threading not pictured • Screws into Proximal Anchor to allow air supply to muscle • Air muscle clamps on to cylinder • Max Stress: 2.85 Mpa • Yield Stress: • 63 MPa (Delrin) • 290 Mpa (316)

  18. Fatigue Analysis • Fatigue Results: (Using an applied force of 53 N rather than 130N) • Weld Nut • FOS=15.53 • Proximal Anchor • FOS=20.46 • Nozzle (316 Stainless Steel) • FOS=316.9 • Nozzle (Delrin) • FOS=37.6 • 316 Stainless Steel Properties: • Endurance Limit (Se): 270 MPa • Ultimate Strength (Sut): 579 MPa • Delrin Properties: • Endurance Limit (Se): 32 MPa • Ultimate Strength (Sut): 69 MPa

  19. Distal Muscle Attachment Assembly

  20. Tendon Cable Use 1.5 mm diameter cable Will use bicycle brake cable Braided Stainless Steel cable Tension can be easily adjusted Preliminary calculations make us believe this solution will be more durable than previous air muscle tendon materials Maximum stress = 100.2 MPa; yield stress = 290 Mpa Factor of Safety = 11.5 Maximum Deformation = 0.233 mm

  21. Distal Muscle Plug • Presses against Distal Muscle Plug Plate with slot for tendon cable to rest in • Plugs distal end of air muscle • No air nozzle needed at the distal end • Proposed Material = Delrin

  22. Maximum Stress = 8.5 MPa Yield Stress = 63 MPa

  23. Distal Muscle Plug Plate • Presses against Distal Muscle Plug • Creates friction on tendon cable, • Allows for tension in tendon cable to be easily adjusted • Proposed Material = 316 Stainless Steel • Necessary Screw Clamping Force = 0.358 N-m

  24. Heel Cable Attachment Point • Attaches distal end of tendon cable to AFO heel protrusion • Held in place by 10-24 screw at distal end, Heel Cable Attachment Pin at proximal end • Allows for: • full range of motion of tendon cable • ease of cable changeover • Proposed Material = 316 Stainless Steel

  25. ANSYS Simulation

  26. Fatigue Analysis • Analyzed with stresses from 53 N force as opposed to 130 N • This will be more realistic to values seen during normal operation • Ultimate Strength = 579 MPa • Endurance Strength = 270 MPa • Factor of Safety = 36.8

  27. Heel Cable Attachment Pin Proposed Material = 316 Stainless Steel

  28. Air Muscle Construction • Outer Sleeve • Inner Tube • Clamp • End

  29. Muscle Testing • Goal of .1 sec inflation time, max of .2 sec, estimated via gait analysis • Function of pressure and flow rate • 4.45cm contraction required for full range of motion • Function of muscle construction

  30. Transient testing • Started by calculating the theoretical flow • Realized this is questionably accurate and very complex • Decided it would be easier and more accurate to directly measure inflation time • Took video of the muscle inflating and counted the number of frames it took to move.

  31. Transient testing • 5 video tests

  32. Muscle Contraction • The muscle was loaded with 53N and inflated

  33. Transient results

  34. Input from Terrain Sensing System Flat terrain Ascending terrain (up stairs/up ramp) Descending terrain (down stairs/down ramp) Relax air muscle Release air Ankle angle at foot strike = -14.65 deg Ankle angle at foot strike = -44.96 deg Gait speed info from sensors Gait speed info from sensors. Programming Flow Chart

  35. Test Plan https://edge.rit.edu/edge/P13001/public/WorkingDocuments/Project%20Management See Edge:

  36. Updated Risk Assessment

  37. Bill of Materials

  38. Schedule for MSD II • Reference EDGE website for working, detailed project schedule: • Planning and Execution – Project Plans and Schedules – “Schedule of Action Items” • http://edge.rit.edu/edge/P13001/public/Planning%20%26%20Execution

  39. Questions?

More Related