P13002: Ankle-Foot Orthotic Un-Tethered, Mechanical

1. P13002: Ankle-Foot Orthotic Un-Tethered, Mechanical Detailed 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 • Project Background • System Architecture • Locking Mechanism • Power Characterization • Sensor Characterization • Microcontroller/ Coding Progress • Component Testing • Bill of Materials • Budget Breakdown • Updated Risk Assessment

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. 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:

7. Key Engineering Specifications

8. Walking Patterns Characterizations used for calculations • Average # of steps per day: 10,000 • # steps on stairs: 100 • # steps on ramps: 100 • Time for rotation: ~0.6 seconds

9. System Architecture • CAD model Reservoir Sensors Battery Processor Valve Piston/Cylinder Mounting Bracket

10. CAD Model: DOF Analysis 3 4 2 1

11. Locking Mechanism:Selection Matrix

12. Cylinder Selection • In order to swing foot, joint must apply ~2.75Nm • If locking device is 1.5” (3.81cm) away from joint, • Round up to 9/16” to be safe

13. Cylinder Benchmarks

14. Valve Selection Criteria • Capable of 125 Psi • #10-32 or 1/8” NPT threads • Allows max flow rate of 0.6213 in3/s • Cv > 0.013 • Assuming laminar, incompressible flow

15. Valve Selection • Cv=0.035 • Solenoid Powered • Normally Closed (solenoid opens valve) • 12 or 24 VDC • 1/8” NPT threaded • ~3 ms response time

16. Locking Mechanism: Stress Calculations • HD Polyethylene • E=125,000 Psi • Yield Strength=4,600

17. Locking Mechanism: Stress Calculations Stress at Bolt Locations: 2000 Psi Stress at Joint: 5000 Psi

18. Locking Mechanism: Stress Calculations 1.67” F M F=17 lbf M=22.695 in-lb

19. Locking Mechanism: Stress Calculations Stress at Piston Connection: 1250 Psi Stress at Joint: 1500 Psi

20. Locking Mechanism:Component Breakdown • What we plan on buying: • Piston/Cylinder • Valve • Fluid Reservoir, 0.72 in3 • Pivot bracket to mount cylinder to top of AFO • What we need to make • Bracket to mount piston to bottom of AFO

21. Power Calculations

22. Battery Selection

23. Circuit Design

24. Sensor Characterization • Measure the output when compared to a known distance. • Yardstick or tape measure required. • Initial comparisons indicate strong correlation between expected and measured characterization curves. • Short range IR sensor: 10-80 cm (4-31 in) • Long range IR sensor: 20-150 cm (8-59 in)

25. Calibration with Paper

26. Calibration with Paper

27. Multiple Surface Testing

28. Multiple Surface Testing

29. Placement of the Sensors: Top 31.63 in 10.25 in 30 in

30. Placement of the Sensors: Bottom Lower Sensor Heel Strike: ~15 cm (5.9 in) Lift-Off: >~15 cm (5.9 in) Tolerance: +/- 2 cm (.79 in) Angle of Lower Sensor: ~20° from vertical 15 cm

31. Coding Progress • Functions written for determining upcoming terrain based on sensor readings • Function written to read sensor values • Working on what needs to be written for SD card • Working on function calculation for gait cycle time

32. System UML

33. Microcontroller Selection • Price: $5 for each model • TI-MSP430G2553 • Stellaris • Memory capability • MSP430 16KB flash memory • Stellaris 256KB flash memory • Speed • MSP430 16 MHz • Stellaris80 MHz • No need to create separate PCB • Ability to connect SD card for writing out data Currently using 2 MSP430 For final assembly: will be using 1 Stellaris *If not enough memory, will add 1 MSP430 NOTE: Stellaris due to come in mid-December

34. Component Testing Subsystem/ Function/ Feature Name: Locking Mechanism- Cylinder Owner: Shane/Pattie Subsystem/ Function/ Feature Name: Locking Mechanism- Reservoir Owner: Shane/Pattie Subsystem/ Function/ Feature Name: Locking Mechanism- Valve Owner: Shane/Pattie

35. Component Testing Subsystem/ Function/ Feature Name: Sensors Owner: John/Dana Subsystem/ Function/ Feature Name: Microcontroller Owner: Sam/John

36. Component Testing Subsystem/ Function/ Feature Name: Battery/ Electrical components Owner: Rob/Dana Subsystem/ Function/ Feature Name: Orthotic Owner: Shane/Pattie

37. Bill of Materials/Budget Breakdown • Projected budget usage: $235.49 • Total estimated weight: 0.51 kg

38. Updated Risk Assessment

39. Updated Risk Assessment

40. Updated Risk Assessment

41. What’s Next

42. Questions?