Terrain Detection System for Foot Drop

1. Terrain Detection System for Foot Drop Christopher R. Sullivan Mechanical Engineering April 18th, 2012 Advisor: Elizabeth A. DeBartolo, Ph.D.

2. Gait Cycle and Foot Drop Stance Swing Swing Initial Double-Limb Support Terminal Swing Second Double-Limb Support Mid-Swing Single-Limb Stance Initial Swing Periods Terminal Swing Initial Swing Mid-Swing Periods Foot Strike Opposite Toe-Off Opposite Foot Strike Tibia Vertical Foot Clearance Foot Strike Toe-Off Toe-Off % of Cycle Foot Crash Mid Trip Fallen 62% 0% 100% % of Cycle 62% 100% Image Source: http://sports.jrank.org/article_images/sports.jrank.org/dorsiflexion.1.jpg

3. What is an Ankle Foot Orthotic? • Replace lost ankle functionality • Foot drop • Correct brace for the correct problem Dynamic Walk Jointed Brace Solid Brace Image Source: http://www.mobilelimbandbrace.com/images/Articulating_AFO_Overlap.gif http://www.spsco.com/assets/images/dynamic-walk-single-side-2_large.jpg http://proactiveasia.com/web_image/orthotics/Trulife%20semi-solid-afo_web.gif

4. Project Goal • Create an Ankle mounted system for identifying specific ground conditions • Today’s talk • Needs assessment • Data Collection Techniques • Preliminary Results Image Source: http://transit-safety.volpe.dot.gov/publications/safety/pedestrian/html/images/dot-tsc-umta-84-36_p0009a.gif

5. Stakeholder Interviews • Interviewed Clients, Clinicians,and ProsthetistOrthotist • Major takeaways • Foot drop has many other compound symptoms • Pros • Allow clients to walk • Cons • weight/bulk of the AFO • Instability on ramps and stairs • AFO user’s needs can differ widely Image Source: http://www.humanresourcesdegree.net/images/stories/School%20Logos%20-%20Masters/NazarethCollege.jpg http://www.workforcediversitynetwork.com/images/logos/RGHS_stacked_150.jpg http://www.rochesterorthopedic.com/

6. Distance Detected Level Ground vs. Descending Stairs

7. IR Range Finder Walking Up Stairs Raw Distance Sensor Voltage • Range Finder Selected • GP2Y0A02Yk 1.5” 4” 8” 12” 24” 31.5” 40” 59.5” 216.5” Image Source: http://www.technologicalarts.com/myfiles/data/gp2d120.pdf Minimum Range Maximum Range

8. RANSAC • RANdom SAmple Consensus • Starting Assumptions • Inliers • Fit to a model • Outliners • Can come from noisy data, or erroneous assumptions Image Source: http://en.wikipedia.org/wiki/RANSAC

9. RANSAC • Input: • Data • Minimum number of data points • Added guess at the gait period • Number of iterations • Minimum error • Minimum number of points for a real model • Output: • Best model • Best consensus set • Best error

10. Determining Gait Period • Piezoelectric plate • Identifying the proper gait period • Pick two similar high point and test the rest of the data for similarities • Differentiation between direction change and heel strike Level Walking Gait Period Analysis

11. When the results are not so pretty Down Stairs Gait Period Analysis

12. RANSAC • Model to be fit Fourth Order Fourier series • Adaptation • Picking the correct repeating curve • Checking the rest of the data Level Walking RANSAC fit

13. RANSAC Results

14. Next Steps • Finding better determination of foot ground collision. • Filtering out of erroneous models given from noisy data. • Using new ground collision data to enhance existing predictive program. • Find determination of when a patient is not walking. • Put all of this onto a microcontroller

15. Future Application • Integrating system into an AFO • Adding functionality of tracking long term change of patients’ gait characteristics.

16. Acknowledgments Funding was supplied by the RGHS RIT alliance Seed fund Rochester General Hospital Richard L Barbano, MD, Ph.D., FAAN Advisor Elizabeth A. DeBartolo, Ph.D. Thesis Committee Mario Gomes, Ph.D. Kathleen Lamkin-Kennard, Ph.D. Nazareth College Physical Therapy Clinic J.J. Mowder-Tinney PT, PhD, NCS Rochester Orthopedic Labs Shawn Biehler, CPO

17. Questions?

18. LaGrange's Method LaGrangian operator LaGrangian force Link kinetic energy Link potential energy Resistive Energy

20. Proposed Design • Attaches to the back of existing AFO • Linear actuator shifts carriage to either side • Carriage holds two individually adjustable backstops • The actuator doesn’t have to support the foot • Infrared range finder • Detect terrain

21. Issues with Design • It adds weight • Make the Brace Lighter • Attaching to the back of an existing AFO • Adhesive • Vacuum • Use existing backstop • Velcro • Actuation • Piezoelectric Linear actuator • Knowing the Ground • Accelerometer • IR Range Finder

22. Accelerometers • Require a lot of data analysis • Drift in integration accuracy • Measuring many different things • Most of which I am uninterested in • Most of which is very noise

23. Functional Block Diagram Multi Surface Sensing Ankle Foot Orthotic Micro-Controller Ground Identification Sensor If Ground Profile Level Ground Range of Motion Stairs or Ramp Position Power Actuator

24. Customer Needs • Fits into a shoe • Ease of access • Adjustability • Light weight • Portable • Inexpensive • Able to be used on both sides of the body • Safety • Durability/fatigue life • Biocompatible surface • Able to be cleaned/sterilized • Functionality • Provide appropriate support for the foot at the appropriate time • Stairs • Ramp • Level surface • Provide accurate assessment of ground conditions, before the foot hits the ground.

25. Defining the Target Clients • They should be able to supply feedback • Would not be a candidate for a commercially available AFO • Must use a jointed brace

26. Constraints

27. Brainstorming

28. Solution Combinations Design 1 Variable peek Rod Design 3 Variable peek Rod Geo Fit

29. Initial Design Matrix

30. Carbon Fiber Brace • Breaks the project up into 2 areas • Bulk reduction in weight and size will help get patients excited about their brace • Spring properties of carbon fiber Figure 7. Carbon Fiber