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Multi Surface Sensing Ankle Foot Orthotic for Foot Drop
Name, department, event, date, advisor Christopher R. Sullivan Mechanical Engineering Student Research & innovation Symposium August 12th, 2011 Advisor: Elizabeth A. DeBartolo, Ph.D.
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Gait Cycle and Foot Drop
100% Foot Strike Opposite Toe-Off Opposite Foot Strike Toe-Off Foot Clearance Tibia Vertical Periods Initial Double-Limb Support Single-Limb Stance Second Double-Limb Support Initial Swing Mid-Swing Terminal Swing Stance Swing % of Cycle 0% 62% Periods Initial Swing Mid-Swing Terminal Swing Toe-Off Swing % of Cycle 62% 100% Mid Trip Foot Crash Fallen Foot Drop is characterized by Inability to control the foot during the Gait Cycle Stroke Cerebral Palsy Direct injury to the Peroneal Nerve Image Source:
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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:
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Project Goal Create an Ankle Foot Orthotic (AFO) that adapts to differing terrain to provide the correct amount of support Todays talk Stakeholder interviews Needs assessment Preliminary design Preliminary analysis Image Source:
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Stakeholder Interviews
Interviewed Clients, Clinicians, and Prosthetist Orthotist 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 Do justice to the differences in patients We talk to a bunch of different patients and all of them had a couple stricking things in common They needed there AFO to walk, so anything that I build would have to continue to allow them to walk All of the patients complained about the instability they felt on stairs Explain why they feel uncomfortable !!!!!!!!! Rochester orthopedic PEDIC LABS Peoples needs vary widely! Image Source:
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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 I intend to test this device on people and they are going to need to be able to communicate back with me about if they
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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
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Functional Block Diagram
Multi Surface Sensing Ankle Foot Orthotic Micro-Controller If Stairs or Ramp Level Ground Ground Identification Sensor Ground Profile Range of Motion Position Inputs out puts Fit the 3 slids you are missing into this one Talk about separating out these different criteria into ways to generate more designs Power Actuator
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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 Include detailed schematic only of final proposed design
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Distance Detected Level Ground vs. Descending Stairs
Feasability talk about using gait data from other studies to generate simulations of what a distance sensor would need to see Infra red range finders
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Moment about the Ankle During Swing
θ1 θ2 θ3 θ4 θ5 m4 m5 m3 m2 m1 x I need to know if my design would be able to support the ankle during swing, too gait data and using LaGrange's method calculated out the dynamic moment felt by the ankle due to the weight of the foot and the momentum of it moving.
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Next Steps Device attachment to brace Find Ramp Gait Data
Select and test Range Finder Select and test Actuator Define algorithm for determining floor surface Model Design Build and test
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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
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Questions?
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LaGrange's Method 𝑞 𝑖 LaGrangian operator 𝑄 𝑖 LaGrangian force 𝑇 𝑖 Link kinetic energy 𝑉 𝑖 Link potential energy 𝑅 𝑖 Resistive Energy 𝑑 𝑑𝑡 𝜕𝑇 𝜕 𝑞 𝑖 − 𝜕𝑇 𝜕 𝑞 𝑖 + 𝜕𝑅 𝜕 𝑞 𝑖 + 𝜕𝑉 𝜕 𝑞 𝑖 = 𝑄 𝑖 𝑀 5 = 𝑎 5 𝑚 5 𝜃 1 𝑙 1 cos 𝜃 1 − 𝜃 𝜃 2 𝑙 2 cos 𝜃 2 − 𝜃 𝜃 3 𝑙 3 cos 𝜃 3 − 𝜃 𝜃 4 𝑙 4 cos 𝜃 4 − 𝜃 5 + 𝑎 5 𝜃 5 − 𝜃 𝑙 1 sin 𝜃 1 − 𝜃 5 − 𝜃 𝑙 2 sin 𝜃 2 − 𝜃 5 − 𝜃 𝑙 3 sin 𝜃 3 − 𝜃 5 − 𝜃 𝑙 4 sin 𝜃 4 − 𝜃 5 +𝑔 sin 𝜃 𝜃 4 𝑙 4 cos 𝜃 4 − 𝜃 5 + 𝑎 5 𝜃 5 − 𝜃 𝑙 1 sin 𝜃 1 − 𝜃 5 − 𝜃 𝑙 2 sin 𝜃 2 − 𝜃 𝜃 1 𝑙 1 cos 𝜃 1 − 𝜃 𝜃 2 𝑙 2 cos 𝜃 2 − 𝜃 𝜃 3 𝑙 3 cos 𝜃 3 − 𝜃 𝜃 4 𝑙 4 cos 𝜃 4 − 𝜃 5 + 𝑎 5 𝜃 5 − 𝜃 𝑙 1 sin 𝜃 1 − 𝜃 5 − 𝜃 𝑙 2 sin 𝜃 2 − 𝜃 5 − 𝜃 𝑙 3 sin 𝜃 3 − 𝜃 5 − 𝜃 𝑙 4 sin 𝜃 4 − 𝜃 5 +𝑔 sin 𝜃 5
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Constraints Metric Units Test Importance (1-7) Fits into a shoe Binary Attempt to fit into a shoe possibly using a floppy (find a better word) foot 2 Ease of access 10 Min Attempt to put on with one hand, time results document relative range of motion necessary to complete task 3 Adjustability cm What rand of body types can this AFO fit? 5 Light weight <1 kg Use hard plastic AFO as benchmark for weight 4 Portable 10hr Operation length 1 Inexpensive <1000$ BOM 6 Able to be used on both sides of the body Can it be used on both sides of the body? 7 You might want to skip this slide for Friday’s presentation.
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Brainstorming Talk through quickly – explain your process Straps
Comments Power Passive Elements Velcro Cheap, has a short lifespan, trouble getting proper contact Li-ion High Energy Density, 1200 cycles PEEK rods Flexible polymer Rods Plastic ratchet Relatively more expensive longer life time, solid connection NiH2 lower energy density, cycles Carbon Fiber Can be used for a leaf Spring Special Sock Similar to amputee patients Passive Run until material Failure Rotary Dampers Geometry based on geometry the brace holds itself onto the patient Pressurized air Pressurizing air on demand would require a battery Metal Springs Knee brace uses the knee as an anchor hold the brace on the leg Mechanical wound To run like a clock (not a very likely choice) Bushing tilt Joint Half of a skate board Truck Active Elements Sensors Microcontrollers Linear Actuator Bulky ADXL345 Accelerometer Accelerometers are hard to use, drift Arduino Some are rather Large, but it has a good development community Electric Motor Requires gear box Sharp IR Range Finder No drift, but could hit pants Teensy Small same kind of Dev. Community as Arduino Piezoelectric Linear Actuator Hold position at zero power Seeeduino Smaller Arduino bigger than the Teensy Stepper motor Easy location Variable Rotary Dampers Hard to find Talk through quickly – explain your process
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Solution Combinations
Design # Name Add on? Brace Material Straps Power Passive Elements Active Elements Comments 1 Variable PEEK rod AFO no Carbon Fiber Velcro LI-ion Peek rods Piezoelectric Linear Actuator Pulls Peek rod into it changing Spring initial Loading 2 Adjustable Plantar Stop add-on Yes none Li-ion Metal Springs Linear Actuator Changes the location on the Back Stop 3 Variable PEEK rod AFO With Geo Fit Geometry Pulls Peek rod into it changing Spring initial Loading Uses Geometry of Spring to Hold leg in place 4 N/A Bushing Tilt Joint Has a variable axis Moved by linear actuator 5 Rotary Damper AFO yes Rotary Dampers Rotary damper added on though a variable transmission, dampening used to stop foot 6 Variable Rotary Damper AFO Polyethylene Variable Rotary damper change damping to stop foot when needed should be paired with a way to move the foot 7 Stripper Motors AFO Torsion Spring Stepper Motor Holds the foot in position at proper time 8 Vareable Carbon Fiber Leaf Spring AFO Carbon Fiber used as leaf spring in back of AFO with movable interfering piece, much like prostatic foot design, but variable Let’s see how you do for time, and then figure out whether to keep, scale back, or remove these slides (this and next one) Design 1 Variable peek Rod Design 3 Variable peek Rod Geo Fit
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Initial Design Matrix Criteria 1 2 3 4 5 6 7 8 AFO Fits into a shoe +
- Ease of access Adjustability of overall foot position Variable axis Portable battery life/ battery dead? Inexpensive Feasibility (back stop change is base line) Level Surface Can Be adjusted to Stairs Can Be adjusted to Ramps Safety features? Durability Able to be cleaned Total + Total - Sum -3 -5 -4 Design # Name Concerns 1 Variable PEEK rod AFO LEG actuators can take different actuation rods 2 Adjustable Plantar Stop add-on Linear actuator to hold plantar stop 3 Variable PEEK rod AFO With Geo Fit Is geo fit possible? And can it be used on all kinds of patients 8 Vareable Carbon Fiber Leaf Spring AFO Look into complete mechanically driven brace, i.e. no control system
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IR Range Finder Feasibility Look into expected data
1.5” ” ” ” ” ” ” ” ” Figure 9. Sharp IR sensors Replace technical drawing with chart from next page showing range Maximum Range Minimum Range Figure 10. Sharp IR sensors Distance Illustration Source:
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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 Remove, or keep as backup
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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 Same, or remove if you’re not going this route
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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 Focus on the mechanism for this talk – eliminate or keep as backup Figure 7. Carbon Fiber
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