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?