Multi Surface Sensing Ankle foot Orthotic
• Put a slide here describing your overall project goals, and what you’re focusing on for this talk
• Add a slide here with an overview of foot drop, and pictures of a couple of typical AFOs
• Might not be a bad idea to show a typical ankle flexion plot through the gait cycle, along with Walking Stick Man
Interviews at NAZ• 10 patients have been interviewed• All of them were stroke victims, with the exception of one with
MS.• All of the patients were elderly, and lived with the assistance
of a spouse or nurse. • All Patients had AFOs for more than 6 months
Interviews at NAZ• Major Takeaways• Foot Drop has many other compound symptoms.
• Rolling of the ankle • Clenching of the toes
• Most AFOs are designed with level surface conditions in mind.• Patients complained about walking down stairs, and ramps
• Patients complained about the weight of the AFO.• Patients also complained about the bulkiness of their braces.• These AFOs are the only things that lets these patients walk
Interviews with Rochester Orthopedics Lab• Why the braces where bulky?• Rolling ankle, distribution of force
• The supplier of numerous commercially available AFOs• Ossur• Becker• Dynamic Walk• Otto Bock• Allard• Tamarack
• Most Commercially available AFOs are meant for patients with just Drop Foot
Figure 1. Dynamic Walk Single
Interview with Dr. Barbano• Patients at Rochester General are under 6 months• Still dealing with many other problems caused by the stroke
• Most Patients are given a solid AFO before they are released• At the hospital it is not common to see these other kinds of
braces• The patents are referred to other clinics in the area, to help
them with physical therapy
Defining the target patient and general needs• Should be based off of the patents
observed at NAZ• They seem to be the patents that we will end
up have to test it on• Should be well into the recovery after their
stroke• They should be able to supply feedback
• Would not be a candidate for a commercially available AFO
• Must use a kind of jointed brace • There gait could also be impaired by rolling
of the ankle or toe curling
Source: http://www.tamarackhti.com/joints/dorsiflexion.asp
Figure 2. Tamarack joint
Customer needs• Functionality• Lifts foot up at appropriate time
• Sit to stand• Stairs• Inclined surface• level surface
• Constraints• 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
Metrics
Metric Units Test Importance (1-4) Ref
Sit to Stand 70 to 85
deg
Detects and Allows for adequate motion of the ankle while attempting to stand from a seated position
4
A Motion Control of a Robotic Walker for
Continuous Assistance
during Standing, Walking and Seating
Operation
Stairs Accent82 to 58
deg
Detects and Allows for freedom of the ankle so the patient could walk with successive foot motion up and down a flight of stairs
3
Ankle-Foot-Orthosis Control in
Inclinations and Stairs
Stairs Decent82 to 45
deg
Detects and Allows for freedom of the ankle so the patient could walk with successive foot motion up and down a flight of stairs
3
Ankle-Foot-Orthosis Control in
Inclinations and Stairs
Inclined surface accent 82 to 46 deg
Detects and Allows for motion of the foot during decent or assent of a ramp
2Ankle-Foot-Orthosis
Control in Inclinations and
Stairs
Inclined surface decent 60 to 80 deg
Detects and Allows for motion of the foot during decent or assent of a ramp
2Ankle-Foot-Orthosis
Control in Inclinations and
Stairs
Level Surface 75 to 45 deg
Patient does not drag there foot on the ground. 1
Constraints
Metric Units Test Importance (1-7)
Fits into a shoe BinaryAttempt 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 1Inexpensive <1000$ BOM 6Able to be used on both sides of the body Binary Can it be used on both sides of
the body? 7
Safety
Metric Units Test Importance (1-3)
Durability/ Fatigue LifeCycles
Fatigue test the AFO (or at least identify weakest component and test that)
3
Biocompatible surface Binary Documentation of material must support claim 2
Able to be Cleaned/Sterilized Binary Documentation of material must support claim 1
Functional block diagram
Initial Design ComponentsStraps Comments Power Comments Passive Elements Comments
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, 20000 cycles Carbon Fiber
Can be used for a leaf Spring
Special Sock Similar to amputee patients Passive Run until material Failure Rotary Dampers
Geometrybased on geometry the brace holds itself onto the patient Pressurized air
Pressurizing air on demand would require a battery Metal Springs
Knee braceuses 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 Comments Sensors Comments Microcontrollers Comments
Linear Actuator BulkyADXL345 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 TeensySmall 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
Initial Design CombinationsDesign
# NameAdd 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
2Adjustable Plantar Stop add-on Yes none Li-ion Metal Springs Linear Actuator Changes the location on the Back Stop
3Variable PEEK rod AFO With Geo Fit no
Carbon Fiber Geometry Li-ion Peek rods
Piezoelectric Linear Actuator
Pulls Peek rod into it changing Spring initial Loading Uses Geometry of Spring to Hold leg in place
4 N/A no Carbon Fiber Velcro LI-ion Bushing Tilt Joint Linear Actuator Has a variable axis Moved by linear actuator
5 Rotary Damper AFO yes none Li-ion Rotary DampersRotary damper added on though a variable transmission, dampening used to stop foot
6Variable Rotary Damper AFO no
Polyethylene Velcro LI-ion
Variable Rotary damper
change damping to stop foot when needed should be paired with a way to move the foot
7 Stripper Motors AFO no Carbon Fiber Velcro LI-ion Torsion Spring Stepper Motor Holds the foot in position at proper time
8Vareable Carbon Fiber Leaf Spring AFO no
Carbon Fiber Velcro LI-ion Carbon Fiber Linear Actuator
Carbon Fiber used as leaf spring in back of AFO with movable interfering piece, much like prostatic foot design, but variable
Figure 3. Variable peek Rod Figure 4. Variable peek Rod Geo Fit
Initial Design MatrixCriteria 1 2 3 4 5 6 7 8 AFOFits into a shoe + 0 + - - - - + 0Ease of access 0 0 + 0 0 0 0 0 0Adjustability of overall foot position + + + + 0 + + + 0
Variable axis + + + + - - - + 0Portable battery life/ battery dead? - 0 - - - - - - 0
Inexpensive - - - - - - - - 0Feasibility (back stop change is base line) - 0 - - - - - - +
Level Surface + + + 0 0 0 + + 0Can Be adjusted to Stairs + + + + + + + + 0Can Be adjusted to Ramps + + + + + + + + 0Safety features? 0 0 0 - 0 - - 0 0Durability - - - - - - - - 0Able to be cleaned - - - - - - - - 0Total + 6 5 7 4 2 3 4 6 1Total - 5 3 5 7 7 8 8 5 0Sum 1 2 2 -3 -5 -5 -4 1 1
Design # Name Concerns1 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 AFOLook into complete mechanically driven brace, i.e. no control system
Adjustable Plantar Stop• Attaches to the back of existing
AFO• Two individually adjustable back
stops attached to rotating joint• Linear actuator offset to the side • It rotates the back stop in and
out of position• But structurally isn't what is
inevitably holding the foot
Figure 5. Y rocker AFO
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 Figure 6. Shell Stopping AFO
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
Steps to Carbon Fiber Brace• Working with Rochester Orthotics Lab• Using old molds• General facilities
• Sitting in on Composites• Figure out how the carbon fiber will react• Build brace for project
Piezoelectric Linear actuator• Small Light weight Linear actuators• 23g• 22 x 10 x 19 mm
• Holding Force• 6.5N
• Stall Force• 7N
Source: http://www.piezomotor.se/uploaded/LL1011_150010_00.pdf
Figure 8. Piezoelectric Actuator
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
IR Rang Finder• Initial Look into expected data
Source: http://www.technologicalarts.com/myfiles/data/gp2d120.pdf
Figure 9. Sharp IR sensors
Figure 10. Sharp IR sensors Technical Drawing
Level Ground
Descending Stairs
Distance Detected Level Ground vs. Descending Stairs
Descending Ramp
Distance Detected Level Ground vs. Descending Ramps
Ramp
Next Steps• Figure out how it is going to attach to the brace• Find Ramp Gait Data• Test out IR sensor• Define algorithm for determining floor surface• Model Design
Questions?