Transcript Systems Design Presentation

Active Ankle-Foot Orthotic
Air Muscle Tethered
Team P13001
Nathan Couper, ME
Bob Day, ME
Patrick Renahan, IE
Patrick Streeter, ME
This material is based upon work supported by the National Science Foundation under Award No. BES-0527358.
Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and
do not necessarily reflect the views of the National Science Foundation.
Agenda
• Project Description
– Assumptions and Project Scope
– Functional Decomposition
– Customer Needs/Specifications
• Proposed Solution
– Physical Decomposition
• Concept Generation and Feasibility
– Morphology Chart
– Concept Screening
– Concept Selection
• Air Muscle Assessment
• Pneumatic Feasibility
• Risk Assessment
• Proposed Schedule
• Questions and Criticism
Description of Problem
• Aiming to design a device that mechanically assists patients
suffering from foot drop
• Foot Drop
– Caused by nerve damage in the lower leg
• Strokes, ALS, MS, Car Accidents, Other Trauma
– Loss of muscle control prevents patient from dorsi-flexing the foot
while walking, as well as extending the toes
– AFO’s are current solution
• Generally rigid support that lifts the foot to a proper angle
– Elastomer Hinge
• Does not allow for smooth gait cycle
• Difficult to go up inclined surfaces, up/down stairs, and on uneven terrain
• Depending on AFO, Plantar-Flexion is not allowed
Assumptions and Project Scope
• Patient maintains zero muscle control over dorsi-flexion, plantarflexion, and toe extension
• This product is designed to be used on a treadmill in a clinical
setting; but can be incorporated into an aquatic setting
– Tethered System
• The elastomer can be adjusted on a patient basis so that when the
patient’s full weight is applied on the AFO, the foot rests at angle
slightly above 90 degrees with respect to the patient’s lower limb
• Designed patient has the ability to use a dorsi-flex assist AFO
without receiving tone-lock spasms
• For calculations:
– Anthropometric Data is from the ANSUR (military) Database
• Based on the 50th percentile man
– 2D system
– no resistive forces/friction associated with the joints
– a normal gait cycle time of 1.2 to 1.5 steps per second is assumed
Functional Decomposition
Customer Needs
Red: Rated 7-9
Directly relates to
project purpose
or patient safety
Yellow: Rated 4-6
Relates to lower
priority patient
interaction, and
periphery project
goals
Green: Rated 1-3
Not critical to
solving primary
issue
Project Specifications
General Breakdown:
•Sensory Specifications
•Movement Specifications
•Force Specifications
•Safety Specifications
•User
•Equipment
Agenda
• Project Description
– Assumptions and Project Scope
– Functional Decomposition
– Customer Needs/Specifications
• Proposed Solution
– Physical Decomposition
• Concept Generation and Feasibility
– Morphology Chart
– Concept Screening
– Concept Selection
• Air Muscle Assessment
• Pneumatic Feasibility
• Risk Assessment
• Proposed Schedule
• Questions and Criticism
Proposed Solution
• Air muscle powers plantar flexion
• Elastomer passively causes
dorsi-flexion (dorsi-assist)
• Less bulky
• Simpler to control
Physical Decomposition
Tethered AnkleFoot Orthotic
AFO (the orthotic
itself)
Molded Case
Air Regulation
System
Air Muscles
Computer
Control System
Regulator
Air Regulation
Controls
Foot Bed
Bladder
Air Source
Control Outputs
Calf Cradle
Sheath
Tubes
Control Inputs
Hinge
Fittings
Fittings
Straps
Elastomer
Tendons
Hardware
(screws/structure)
Clamps
Agenda
• Project Description
– Assumptions and Project Scope
– Functional Decomposition
– Customer Needs/Specifications
• Proposed Solution
– Physical Decomposition
• Concept Generation and Feasibility
– Morphology Chart
– Concept Screening
– Concept Selection
• Air Muscle Assessment
• Pneumatic Feasibility
• Risk Assessment
• Proposed Schedule
• Questions and Criticism
Morphological Design Considerations
AFO actuation
Concept
Air Muscle
Connection
What motions are air muscles responsible for?
How are air muscles attached to AFO?
Tendon Design
How does force from Air Muscle actuate AFO?
Air Supply
How will air muscles be filled and regulated
AFO
Construction
Type
Traction
What construction style will the AFO have?
What will keep the AFO from slipping?
AFO actuation
Concept
Air Muscle
Connection
Tendon Design
Air Supply
AFO
Construction
Type
Traction
A
B
C
D
(Reference)
Passive Dorsi Assist
No Plantar Assist
Passive Dorsi
Assist
Active Plantar
Assist
Active Dorsi
Assist
Passive Plantar
Assist
Active Dorsi
Assist
Active Plantar
Assist
(Reference)
No Air Muscle
Rigid Anchor to
AFO
Cable Attachment
AFO snaps into
Air muscle
Construct
(Reference)
No Air Muscle
Air muscle
Direct mount
Cable and
housing
Steel leader (see
Crab)
Compressor
Regenerative
automatic
foot pump
Hybrid (hard foot
bed, soft calf
sleeve)
(Reference)
No Air Muscle
Compressed air
tank
(Reference)
Hard shell (hinged)
Soft shell
Fully rigid hingeLess
(Reference)
Shoe reliant
Knurled AFO
bottom
Rubberized AFO
bottom
AFO actuation
Concept
Air Muscle
Connection
Tendon Design
Air Supply
AFO
Construction
Type
Traction
A
B
C
D
(Reference)
Passive Dorsi Assist
No Plantar Assist
Passive Dorsi
Assist
Active Plantar
Assist
Active Dorsi
Assist
Passive Plantar
Assist
Active Dorsi
Assist
Active Plantar
Assist
(Reference)
No Air Muscle
Rigid Anchor to
AFO
Cable Attachment
AFO snaps into
Air muscle
Construct
(Reference)
No Air Muscle
Air muscle
Direct mount
Cable and
housing
Steel leader (see
Crab)
Compressor
Regenerative
automatic
foot pump
Hybrid (hard foot
bed, soft calf
sleeve)
(Reference)
No Air Muscle
Compressed air
tank
(Reference)
Hard shell (hinged)
Soft shell
Fully rigid hingeLess
(Reference)
Shoe reliant
Knurled AFO
bottom
Rubberized AFO
bottom
Performance Metrics
No sharp protrusions
Hold up foot when stepping forward/resist foot slap
Secure foot in orthotic
Integration of terrain sensing system
Allow for both plantar and dorsi-flexion of the foot
Ease of attachment/customization
Ease of customizable programming per individual
Fit customization to individual
Installation/ease of use
AFO actuation
Concept
Air Muscle
Connection
Tendon Design
Air Supply
AFO
Construction
Type
Traction
A
B
C
D
(Reference)
Passive Dorsi Assist
No Plantar Assist
Passive Dorsi
Assist
Active Plantar
Assist
Active Dorsi
Assist
Passive Plantar
Assist
Active Dorsi
Assist
Active Plantar
Assist
(Reference)
No Air Muscle
Rigid Anchor to
AFO
Cable Attachment
AFO snaps into
Air muscle
Construct
(Reference)
No Air Muscle
Air muscle
Direct mount
Cable and
housing
Steel leader (see
Crab)
Compressor
Regenerative
automatic
foot pump
Hybrid (hard foot
bed, soft calf
sleeve)
(Reference)
No Air Muscle
Compressed air
tank
(Reference)
Hard shell (hinged)
Soft shell
Fully rigid hingeLess
(Reference)
Shoe reliant
Knurled AFO
bottom
Rubberized AFO
bottom
Function/Component
1
2
3
Active Dorsi Assist
Active Plantar Assist
Active Dorsi Assist
Active Plantar Assist
Active Dorsi Assist
Active Plantar Assist
No Air Muscles
Cable Attachment
Rigid Anchor to AFO
AFO snaps into air
muscle construct
Tendon Design
No Air Muscles
Cable and housing
Cable and housing
Cable and housing
Air Supply
No Air Muscles
Compressed air tank
Compressed air tank
Compressed air tank
AFO Construction Type
Hard Shell (hinged)
Hard shell (hinged)
Hard shell (hinged)
Hard shell (hinged)
Traction
Shoe reliant
Shoe reliant
Shoe reliant
Shoe reliant
No sharp protrusions
0
0
-
+
Hold up foot when
stepping forward/resist
foot slap
0
0
0
0
Secure foot in orthotic
0
0
0
-
Integration of terrain
sensing system
0
0
0
0
Allow for both plantar and
dorsi-flexion of the foot
0
+
+
+
Ease of
attachment/customization
0
-
-
0
Ease of customizable
programming per
Individual
0
-
-
-
Fit customization to
Individual
0
0
0
+
Installation/Ease of use
0
-
-
-
Net
0
-2
-3
0
AFO actuation concept
Air Muscle Anchor
Reference
Passive Dorsi Assist
No Plantar Assist
AFO actuation
Concept
Air Muscle
Connection
Tendon Design
Air Supply
AFO
Construction
Type
Traction
A
B
C
D
(Reference)
Passive Dorsi Assist
No Plantar Assist
Passive Dorsi
Assist
Active Plantar
Assist
Active Dorsi
Assist
Passive Plantar
Assist
Active Dorsi
Assist
Active Plantar
Assist
(Reference)
No Air Muscle
Rigid Anchor to
AFO
Cable Attachment
AFO snaps into
Air muscle
Construct
(Reference)
No Air Muscle
Air muscle
Direct mount
Cable and
housing
Steel leader (see
Crab)
Compressor
Regenerative
automatic
foot pump
Hybrid (hard foot
bed, soft calf
sleeve)
(Reference)
No Air Muscle
Compressed air
tank
(Reference)
Hard shell (hinged)
Soft shell
Fully rigid hingeLess
(Reference)
Shoe reliant
Knurled AFO
bottom
Rubberized AFO
bottom
Function/Component
Reference
4
5
6
AFO actuation concept
Passive Dorsi Assist
No Plantar Assist
Passive Dorsi Assist
Active Plantar Assist
Passive Dorsi Assist
Active Plantar Assist
Passive Dorsi Assist
Active Plantar Assist
No Air Muscles
Cable Attachment
Rigid Anchor to AFO
AFO snaps into air
muscle construct
Tendon Design
No Air Muscles
Cable and housing
Cable and housing
Cable and housing
Air Supply
No Air Muscles
Compressed air tank
Compressed air tank
Compressed air tank
AFO Construction Type
Hard Shell (hinged)
Hard shell (hinged)
Hard shell (hinged)
Hard shell (hinged)
Traction
Shoe reliant
Shoe reliant
Shoe reliant
Shoe reliant
No sharp protrusions
0
0
-
+
Hold up foot when
stepping forward/resist
foot slap
0
0
0
0
Secure foot in orthotic
0
0
0
-
Integration of terrain
sensing system
0
0
0
0
Allow for both plantar and
dorsi-flexion of the foot
0
+
+
+
Ease of
attachment/customization
0
+
-
0
Ease of customizable
programming per
Individual
0
+
+
+
Fit customization to
Individual
0
0
0
+
Installation/Ease of use
0
0
0
-
Net
0
3
0
2
Air Muscle Anchor
Function/Component
Reference
7
8
9
AFO actuation concept
Passive Dorsi Assist
No Plantar Assist
Passive Dorsi Assist
Active Plantar Assist
Passive Dorsi Assist
Active Plantar Assist
Passive Dorsi Assist
Active Plantar Assist
No Air Muscles
AFO snaps into air
muscle construct
Cable Attachment
Cable Attachment
Tendon Design
No Air Muscles
Cable and housing
Cable and housing
Cable and housing
Air Supply
No Air Muscles
Compressed air tank
Compressed air tank
Compressed air tank
AFO Construction Type
Hard Shell (hinged)
Hard shell (hinged)
Soft shell
Hybrid
Traction
Shoe reliant
Rubberized AFO bottom
Shoe reliant
Shoe reliant
No sharp protrusions
0
+
+
+
Hold up foot when
stepping forward/resist
foot slap
0
0
-
-
Secure foot in orthotic
0
0
0
0
Integration of terrain
sensing system
0
0
-
-
Allow for both plantar and
dorsi-flexion of the foot
0
+
+
+
Ease of
attachment/customization
0
0
0
0
Ease of customizable
programming per
individual
0
+
-
+
Fit customization to
individual
0
+
+
+
Installation/Ease of use
0
-
0
0
Net
0
3
0
2
Air Muscle Anchor
Morphological Design Results
AFO actuation
Concept
Air Muscle
Connection
Tendon Design
Air Supply
AFO
Construction
Type
Traction
Passive dorsi assist, active planter assist
Cable attachment
Cable and housing
Compressed air tank
Rigid construction with dorsi assist hinge
Shoe dependent
Elastomer Force Variation
AFO Elastomer Force Variation versus Displacement
60
50
Force (N)
40
30
20
10
0
0
0.005
0.01
0.015
0.02
0.025
ΔHeight (m)
0.03
0.035
0.04
0.045
0.05
Ankle Linear Force Comparison
Ankle Free-Body Diagram
Air Muscle Extension Data
Source: Senior Design Project P12029
Air Muscle Force Data
30lbs = 133N
Source: Senior Design Project P12029
Air Supply
• Concerns
– Instantaneous Flow rate
• Air muscle filling
– Stored Energy
• Size of supply required
• Tank filling cost/convenience
– Sizing of Lines and Solenoids
• Size of Solenoid required
Transient Muscle Filling
• Main factor is orifice size in the solenoid
and muscle size
• Desire .1s fill time minimum
– Requires 11.7 in3/sec (0.4 CFM)
– Max flow through .125” orifice at 60psi is
approximately 12.7 in3/sec
• Near the maximum, may require a slower
fill time or larger solenoids. Must be
examined in detailed design closely
Solenoid Diagram
Continuous supply
• Low continuous air usage
– 48ci 3000psi tank = 2050 steps or 3.2km
– 15 Gal 150psi air compressor = 11.8km
• Assuming 1 muscle event per 2 steps and .8m per
step
• Requirements are reasonable and do not
likely pose an issue
Agenda
• Project Description
– Assumptions and Project Scope
– Functional Decomposition
– Customer Needs/Specifications
• Proposed Solution
– Physical Decomposition
• Concept Generation and Feasibility
– Morphology Chart
– Concept Screening
– Concept Selection
• Air Muscle Assessment
• Pneumatic Feasibility
• Risk Assessment
• Proposed Schedule
• Questions and Criticism
7
Inadequate material
durability
Failure of selected
materials in differing
environments
Poor material
selection/analysis
2
2
4
Over-engineer the materials used
in the AFO device and attachments
Nate Couper
2
Continually update project
schedule, and meet bi-weekly at
minimum
Pat
Renahan
2
Discuss workload and time
commitments from the previous
week at bi-weekly meetings
1
Develop an in-depth budget, and
continually update it as progress
continues to be made
Pat
Renahan
Work in sub-teams of two or
greater to allow for a checks and
balances system for calculations
Implement a muffler system for the
pneumatics that reduces the noise
as much as possible maintaining
minimal size and mass, and
avoiding negative effects on the
pneumatics system
Bob Day
8
Completion of work within
scheduled times
9
Unbalanced distribution of
work load
Ladder-effect of other
work getting pushed
behind, or workoverload at the end of
the quarter
Different team
members carrying the
majority of the
workload at different
points during the
design process
10
Completing the project
within the specified
budget
Inability to continue to
fund the project
through completion
Poor project
management and
inadequate budget
calculations
12
Over simplifying the
analytical model
Inadequate supply of
power or inadequate
material selection due
to assuming certain
forces negligible
Desire to reduce
needed calculations
and oversimplifying
to make calculations
easier
1
2
2
13
Keeping the noise level of
the air muscle system
below 60 dB
Uncomfortable
surroundings in the
clinical setting
Inadequate muffling
of the pneumatics
system
2
1
2
Likelihood scale
1 - This cause is unlikely to happen
2 - This cause could conceivably
happen
3 - This cause is very likely to happen
Poor project
planning and
management
Poor distribution of
workload and poor
project management
2
2
1
1
1
1
Severity scale
1 - The impact on the project is very minor. We will still meet deliverables on time and
within budget, but it will cause extra work
2 - The impact on the project is noticeable. We will deliver reduced functionality, go over
budget, or fail to meet some of our Engineering Specifications.
3 - The impact on the project is severe. We will not be able to deliver, or what we deliver
will not meet the customer's needs.
Plan B Actions
(for those with importance rating of 4 or higher)
• Failure of the device while air
muscles are activated
– Allow for the air system to be
easily disconnected (quick
connects)
– Allow for the air system to be
easily shut-off in case of an
unexpected design failure
• Pressure source attachment
point failure
– Allow for the air muscles to be
quickly connected to the AFO
by a commonly used material
(zip ties)
– Supply the clinic/setting with
spare muscle assemblies
• Popping the pressure-fed air
muscles when too little or too
much force is applied
– Supply the clinic/setting using
this device with spare air
muscle assemblies
• Inadequate material durability
– Supply the clinic/setting using
this device with spare air
muscle assemblies
• Tendon wire stretching
– Develop a few separate
feasible options for tendon
wire materials
NOTE: Due to the clinical setting of our
patients, these actions are not of much
concern as the patient is in a safe
environment where the device can be
easily manipulated and fixed
Agenda
• Project Description
– Assumptions and Project Scope
– Functional Decomposition
– Customer Needs/Specifications
• Proposed Solution
– Physical Decomposition
• Concept Generation and Feasibility
– Morphology Chart
– Concept Screening
– Concept Selection
• Air Muscle Assessment
• Pneumatic Feasibility
• Risk Assessment
• Proposed Schedule
• Questions and Criticism
Project Schedule
• Upcoming priority deadlines:
– Fall Quarter Week 9: Detailed Design Review
Reference EDGE website for working,
detailed project schedule:
• Planning and Execution – Project Plans and
Schedules – “Schedule of Action Items”
• http://edge.rit.edu/edge/P13001/public/Planning%2
0%26%20Execution
Questions or Comments?