1. P14042: Una-Crutch Right Move, Right Place, Right Time
Subsystems Design Review
Ana Allen
Joanna Dzionara-Norsen
Beverly Liriano
Dan Sawicki
DAN
QUESTIONS TO ANSWER IN SYSTEM DESIGN REVIEW
•Do requirements "flow down" to functions, and are all requirements addressed?
•Do your functions map to the physical architecture?
•What analysis have you done to support decisions about critical technologies and selected concepts?
•What are the performance limits?
•How are you going to test that requirements are met?
•Do you have the capabilities and resources to realize your design?
•What are the major risks (technology, project)? Do you have mitigation plans?
•Has you design been adequately reviewed?

2. Agenda Review (Weeks 1-6) Identifying Critical Subsystems
Background
Problem Definition
Additional Project Deliverables
Identifying Critical Subsystems
Engineering Requirements
Risk Assessment
Functional Decomposition
System Architecture
Proof Of Concept
Overview of Prototypes / Prototype Test Plan
User Feedback
Second- Order Analysis
Feasibility
Manufacturing Analysis
Detailed Design Preview (Weeks 10-12)
DAN
***Do requirements “flow down” to subsystems & are all requirements addressed?
•Have you demonstrated “proof-of-concept”? What analysis/prototyping have you done to demonstrate feasibility of critical subsystems?
Prototypes created
***How are you going to test that requirements are met?
•Has your design been adequately reviewed?
Analysis: Focus Group, Second Order Analysis

3. Review (weeks 1-6)
JOANNA

4. Many designs all revolving around two SEPERATE crutches.
Current Product
Many designs all revolving around two SEPERATE crutches.
Una-Crutch is a design that can combine from 2 separate pieces into 1 universal device
JOANNA

5. P14042 Problem Statement Current State Standard axilla crutches
A prototype was developed by Kyra, but the product is non-load bearing and has no effective connective mechanism
Desired State
A functional product which is ergonomically friendly, has a quick and intuitive method of connection, and can be marketed to companies
Project Goals
Perform analysis of standard axilla crutches, crutch patents, and assistive technologies used specifically for lower body injuries
Constraints
Consider Intellectual Property for the connective mechanism
JOANNA
The Una-Crutch is an assistive technology which supports and allows mobility for any user who has a lower body injury.  The device is a two-crutch design which snaps together to form one crutch when needed, thus eliminating the burden of handling an unused crutch.  The standard two-crutch design is not comfortable for the user and does not have any connective mechanism.  A current prototype of the Una-Crutch is not designed with load-bearing capabilities or cheap mass production, and refinement is required in ergonomics, comfort, and the connective mechanism.
The goals of this project are to analyze the current Una-Crutch prototype and identify opportunities to improve the comfort of the design, the adjustability, ease of use, and the production costs, while maintaining the functionality of a standard crutch.  The final result will be a functional prototype which will be manufactured for market production.

6. Additional Project Deliverables
Functional prototype which will be targeted towards the majority of crutch users and will be available as a household item.
The product will have an aesthetic appeal and will have the potential to be manufactured right away.
Patent Documentation
Logbook
Prove the concept – prototyping
Protection of Intellectual Property
Conduction of market research
JOANNA
Consistent, thorough, and chronological logbook notes and documentation
Design with manufacturing process identified
Testing / Analysis with ‘x’ number of people to demonstrate functionality
Exploration in materials
Design drivers: innovative design that is completely new

7. Prototypes Introduced Week 6A B C D E F
JOANNA

8. Identifying Critical Subsystems
ANA
•Consider your risk list
–Highest technical risks: review with team
•Consider your functional decomposition
–Most challenging technically: review with team
•Consider your engineering requirements
–Most important 4-8 system level requirements
•Consider the required system-level behavior
–Most important behaviors
•Other considerations??

9. Risk Assessment
ANA

10. Identifying Critical Sub Systems
Risk Assessment
Connective Mechanism Failure
User treats crutch as toy
User Cannot connect the crutches while immobilized on one leg
ANA

11. Functional Decomposition
Support independent user with lower extremity injury walking from point A to point B in multiple types of environments.
Position Crutches
Access crutch assembly
Permit height adjustment
Permit connective versatility
Transport User
Support user weight
Maintain contact with the ground
Stabilize user in vertical position
Mobilizes user
Release User
Disengage from crutch-user interface
ANA

12. Identifying Critical Sub Systems
Risk Assessment
Connective Mechanism Failure
User treats crutch as toy
User Cannot connect the crutches while immobilized on one leg
Functional Decomposition
Permit height adjustment
Permit connective versatility
ANA

13. Engineering Requirements
ANA

14. Identifying Critical Sub Systems
Risk Assessment
Connective Mechanism Failure
User treats crutch as toy
User Cannot connect the crutches while immobilized on one leg
Functional Decomposition
Permit height adjustment
Permit connective versatility
Engineering Requirements
Do not fracture or break under user load on double crutch or ½ user load on one crutch
User will be able to use the Una-Crutch without compromising comfort
Interfacing mechanism does not unlock due to user weight
Appealing to the majority
ANA

15. System Architecture
ANA

16. Identifying Critical Sub Systems
Risk Assessment
Connective Mechanism Failure
User treats crutch as toy
User Cannot connect the crutches while immobilized on one leg
Functional Decomposition
Permit height adjustment
Permit connective versatility
Engineering Requirements
Do not fracture or break under user load on double crutch or ½ user load on one crutch
User will be able to use the Una-Crutch without compromising comfort
Interfacing mechanism does not unlock due to user weight
Appealing to the majority
System Architecture
User Interface
Height Adjustment
Connective Mechanism
ANA

17. Identifying Critical Sub Systems
Risk Assessment
Connective Mechanism Failure
User treats crutch as toy
User Cannot connect the crutches while immobilized on one leg
Functional Decomposition
Permit height adjustment
Permit connective versatility
Engineering Requirements
Do not fracture or break under user load on double crutch or ½ user load on one crutch
User will be able to use the Una-Crutch without compromising comfort
Interfacing mechanism does not unlock due to user weight
Appealing to the majority
System Architecture
User Interface
Height Adjustment
Connective Mechanism
ANA
Connective Mechanism

18. Identifying Critical Sub Systems
Risk Assessment
Connective Mechanism Failure
User treats crutch as toy
User Cannot connect the crutches while immobilized on one leg
Functional Decomposition
Permit height adjustment
Permit connective versatility
Engineering Requirements
Do not fracture or break under user load on double crutch or ½ user load on one crutch
User will be able to use the Una-Crutch without compromising comfort
Interfacing mechanism does not unlock due to user weight
Appealing to the majority
System Architecture
User Interface
Height Adjustment
Connective Mechanism
ANA
Connective Mechanism
Axilla Pad/ Handles

19. Identifying Critical Sub Systems
Risk Assessment
Connective Mechanism Failure
User treats crutch as toy
User Cannot connect the crutches while immobilized on one leg
Functional Decomposition
Permit height adjustment
Permit connective versatility
Engineering Requirements
Do not fracture or break under user load on double crutch or ½ user load on one crutch
User will be able to use the Una-Crutch without compromising comfort
Interfacing mechanism does not unlock due to user weight
Appealing to the majority
System Architecture
User Interface
Height Adjustment
Connective Mechanism
ANA
Connective Mechanism
Axilla Pad/ Handles
Frame

20. Critical Subsystems Defined
Connective Mechanism
Frame
Axilla Pad/
Handles
ANA

21. Proof-of-Concept DAN Technical feasibility:
–Analysis (what questions are you answering?)
•Simple models first to get approximate magnitudes
•Estimate complexity to answer key questions
•Several analyses to answer all key questions
–Demonstration or prototyping (what behaviors are you trying to show?)
•Functional demonstration (cause-effect) that proposal should work
•Physical mock-up
–Experimentation (what questions are you answering?)
•Controlled and measured to quantify feasibility
–Description of system behavior (what behaviors are you describing?)
•Logic based flow charts
•Feature descriptions, use cases, operating modes

22. Prototypes Introduced Week 6A B C D E F
DAN

23. Prototypes Introduced Week 6A B C D E F
DAN
REVISED

24. Prototype G Pros: Cons: Compact Design Usable for all ages Stable
Male/female mold
Pros:
Compact Design
Usable for all ages
Stable
Cons:
Not necessarily aesthetically pleasing
Two separate bases
Pad is in contact with the ground
Pin
DAN

25. Prototype H Pros: Cons: Lightweight Easy to manufacture
Sliding button
Pros:
Lightweight
Easy to manufacture
Sliding button connective mechanism
Cons:
Design resembles standard axilla crutch
DAN

26. 1. Axilla Pads and Handles 2. Frames and Connective Mechanisms
Prototypes to Create
1. Axilla Pads and Handles
2. Frames and Connective Mechanisms B C G H
DAN

27. Axilla Pads and Handles Prototypes Created
BEV

28. Frames and Connective Mechanisms Prototype B and C
BEV C

29. Frames and Connective Mechanisms Prototype G
BEV G

30. Frames and Connective Mechanisms Prototype H
BEV
Symmetric VS. Assymetric

31. Prototype Test Plan
BEVERLY

32. User Feedback
Axilla Pads and Handles
BEV

33. User Feedback
Axilla Pads and Handles
BEV

34. User Feedback
Frames and Connective Mechanisms
BEV

35. Second-Order Analysis
Magnetic Analysis
Bike Clamp Analysis
Connective Mechanism Analysis
CAD Model
Spring Analysis
Deflection Analysis
B/C Prototype Analysis
BEV

36. Magnetic Analysis Two configurations: Two shapes:
Magnet to Magnet
Magnet to Plate
Two shapes:
Square/ Rectangular
Cylindrical/ Disk
Analyzing Grade 42 magnets
Engineering Requirement S5:
Interfacing mechanism does not unlock due to user weight.
Ideal value: 3 lbs.
Marginal Value: 5 lbs.
DAN

37. Magnetic Analysis Magnetism Physics on a Crutch
DAN
Pull Force: quantity required to separate two attracting magnets.
Pull Force Equations: The Lorentz Equations
Pull Force Increases as Area Increases.
Pull Force Decreases as Distance Increases.

38. Magnetic Analysis Configurations Analyzed
Square Magnets Chosen
Easier to embed in material.
Proper amount of Pull Force.
DAN

39. Prototype Design Tested
Magnet Overview
DAN
Prototype Design Tested
Note: If used in final design, magnets will have a small distance separating them.

40. Bike Clamp Analysis Split-Ring Clamp Type Shaft Collar Analysis:
Torque necessary to achieve pre-load
Axial holding force of seat post collar
Hoop Tension in collar
JOANNA

41. Bike Clamp Analysis Torque in Cap Screw
Assume:
Cap screw is coarse pitch
Low or medium carbon
Non-permanent connection
Screw diameter = 6 mm
Torque = 6.11 Nm
JOANNA

42. Bike Clamp Analysis Axial Holding Force
Assume:
Coefficient of friction = 0.61
Fx = 13,000 N
JOANNA

43. Bike Clamp Analysis Hoop Tension
Assume:
Collar width = 12 mm
Internal radius mm
Internal pressure = 7.08 MPa
Fh = 540 Pa
JOANNA

44. CAD Model: B/C Prototype
Cheetah Leg Connection Mechanism
Grip Connection Mechanism

45. Spring Analysis N Analyzing Spring at Base of Crutch.
Normal Force = Spring Force
N = user load
Two Stresses on Spring:
Torsion Shear Stress
Direct Shear Stress
DAN N

46. Spring Analysis Results
DAN
Stress absorbed by the springs results in a large stress.
May give user more endurance to use crutches longer.

47. Deflection of Cheetah Leg BaseR2
Assume:
Carbon fiber material
Circular cross-section
r = 0.75in = 1.91x10-2m
R2 = 0.3 m
Deflection = 0.08in = 0.002m P
JOANNA M D P P

48. Feasibility
BEV

49. Manufacturing Processes
BEV
Summary
•What questions do you need to answer to demonstrate feasibility of your critical subsystems? What are the most efficient and effective means to answer questions?
•Add-up key contributors to critical system requirements. Can system requirements be achieved thru your critical subsystems?
•Iterate and converge as needed
•Update your risk assessment

50. Brinkman Lab Resources
3D Printing (Connective Mechanisms)
Water Jet (Frames)
RTV Mold (Axilla Pads/ Hand grips)
ANA

51. Detailed Design Preview
ANA

52. Detailed Design Phase (Weeks 10-12)
ANA

53. Detailed Design Phase (Weeks 10-12)
Cost and Material Analysis (Friction Analysis)
Connective Mechanism Prototypes from Brinkman Lab
Focus Group for New Prototypes
FEA and Detailed Design Analysis
Bill of Materials
ANA

54. Questions? Thank you! DAN
Focus on areas with greatest impact (or risk) to success, and invite “critics” to challenge your assumptions & decisions
Show evidence (analysis) used to support key decisions
Follow agenda – if more time needed, schedule follow-up
Thank you!

55. Backup Slides

56. Customer Requirements
BEV

57. Final Product Test Plan