P14042: UNA-CRUTCH
Right Move, Right Place, Right Time
Systems Design Review Day 2
Ana Allen
Joanna Dzionara-Norsen
Beverly Liriano
Dan Sawicki
Agenda
Thursday
Tuesday
Background
•
•
•
•
•
•
Problem Statement Summary
Customer Requirements
Engineering Requirements
HOQ
Market Analysis/ Benchmarking
Functional Analysis
Concept and Architecture Development
Engineering Analysis
• Risk Assessment
• Test Plan
CONCEPT AND
ARCHITECTURE
DEVELOPMENT
Concepts
Initial Concepts Rev 1
Pugh Chart
Initial Concepts Rev 1
Pugh Chart (Continued)
Initial Concepts Rev 2
Pugh Chart
Initial Concepts Rev 2
Pugh Chart (Continued)
New Concepts Rev 3
Pugh Chart
Connective Mechanism Terms
Male/ Female
Connection
Guide Track
Pin
Magnetic
Clamp
Rubber Snap
Tupperware
Snap
Concept NA
• Pros:
• Springs relax user tension
Pin
Hinge
• Large surface area on single
crutch
• Hinge is simple to use
• Cons:
• Expensive
• Many components
• Too many steps to assemble
Concept NB
Male/female mold
• Pros:
• Easy connection
• Aesthetically pleasing
Male/female mold and/or pin
• Innovative design
• Minimal components
• Spring base
• Cons:
• Bulky
• Potentially expensive
• Magnetic Connection
Magnetic
Concept NC
Male/female mold
• Pros:
• Adjustable handle
• Spring base
Male/female mold
• Male/female mold is an easy
connection
• Innovative design
• Cons:
• Stability
• Thickness
Clamp
Concept ND
Guide track
• Pros:
• Lightweight
• Revolutionary handle design
• Cons:
Male/female mold
• Base connection is
inconvenient if user is on one
leg
• Similar to axilla crutch
Snap
Concept NE
Male/female mold
• Pros:
• Foldable into a cane
• Lightweight
• Stable
Pin
• Cons:
• Two separate bases
• Not aesthetically pleasing
• Pad is in contact with the
ground
Concept NF
Male/female mold
for elbows
• Pros:
• Largest surface area for
connection
• No axillary component
• Spring base
• Minimal components
• Cons:
• Not aesthetically pleasing
• Stability compromised
New Concepts Rev 4
Pugh Chart
System Architecture
ENGINEERING ANALYSIS
Engineering Analysis Overview
Friction Analysis
Cantilevered Beam Analysis
Static Analysis
Loads: Statics Analysis of Axilla Crutch
Analyzed from user recommended
angles between 0° and 45°.
Three Forces acting on object.
Friction Force Increases as θ
increases.
θ[deg] θ[rad] cos(θ) [deg] sin(θ) [deg] Px
Py
P
N
Ff
[deg] [rad]
[deg]
[deg]
[lbf] [lbf] [lbf] [lbf] [lbf]
30.000 0.524 0.866
0.500 75.000 -129.904 150.000 129.904 75.000
High
μs
value
to
low
μs
value
Ice will result
in slip the
quickest!
Concrete is
least likely to
slip!
Cantilevered Beam Analysis
• Crutch handle modeled as a cantilevered beam with a
distributed load and external moment:
• Cross-sections considered: circular, square, hollow
circular, I-beam, T-beam
• Maximum stress from bending:
σ𝑐𝑖𝑟𝑐, 𝑠𝑞 = 25 MPa
σ𝐴𝑙 = 27.6 MPa
OD = 0.47 in
= 12 mm
L = 0.39in
L = 0.39in
= 10 mm
Smallest dimensions at which the maximum stress from bending does not
exceed the yield strength of aluminum
Static Analysis
ASSUMPTIONS:
Negligible out of plane
loads
Entire user load is on the
hand grip
The underarm pad is being
held by a screw.
P
ΣFy=ma=0
Σfy=-P+Nf=0
P=Nf
Nf
Static Analysis
ASSUMPTIONS:
Force on Dy can be
neglected
Force Dx has a direct relation
with Cx being Dx=Cx/2
Cx
Cy
Dx
Dy
Nf
ΣFy=ma=0
ΣFy=Nf-Cy=0
Nf=Cy=P
Static Analysis
P
BX
BX
By
By
ΣFy=ma=0
ΣFy=2By-P=0
By=P/2
Statics Analysis
Ax
Ax
Static Analysis
Ax
Bx
ASSUMPTIONS:
Force on Dy can be
neglected
By
Cy
Cx
Dx
Dy
unknown: 3 unknowns
Ax,BX,Cx
Equations: 3 equations
ΣFy=ma=0
ΣFx=ma=0
ΣM=0
Prototype Test Plan
Risk Assessment
Action Items for Subsystem Design Phase
Week 7
Week 8
Week 9
Nazareth
Orthopedic
Clinic
Connective
Mechanism
Prototypes
CAD Design
Continue
Mechanical
Analysis
User
Interface
Prototypes
FEA Analysis
of Prototype
Continue
Concept
Design
Experimental
Friction
Analysis
THANK YOU AND WE ARE NOW OPEN
FOR QUESTIONS!
BACKUP SLIDE
Detailed Project Plan (Week 7)
Detailed Project Plan (Week 8-9)
Bill of Materials
Final Product Test Plan
QUESTIONS?