Ankle Linear Force Comparison

A (reference) B C D

Current Passive-Dorsi-flex AFO Dorsi-flex assist AFO Plantar-flex assist AFO Plantar/Dorsi assist AFO

Segment

Selection Criteria Weight Required Force (N) Wtd Required Force

(N) Wtd Required Force (N) Wtd Required Force

(N) Wtd

Required Plantar Flexion Force

50%

0 0.00 17.82 8.91 0 0.00 17.82 8.91

Required Dorsi Flexion Force

50%

0 0.00 0 0.00 38.16 19.08 38.16 19.08

Total Force 0.00 8.91 19.08 27.99

Risk Assessment

ID Risk Item Effect Cause

Likelihood

Severity

Importance Action to Minimize Risk Owner

Describe the risk briefly What is the effect on any or all of the project deliverables if the cause actually happens?

What are the possible cause(s) of this risk?

L*S What action(s) will you take (and by when) to prevent, reduce the impact of, or transfer the risk of this occurring?

Who is responsible for following through on mitigation?

1

Failure of the device while the air muscles are activated

The patient will not be able to release from plantar-flexion

Solenoid failure; air source failure

2 2 4 Developed a backup system within the solenoid bank. Many risks cannot be accounted for in the design of the system

Bob Day

2Stretching of the tendon wire

The air muscles will not control the joint movement as well

Poor material selection/inability to re-tension tendon cables 3 2 6

Implement a cable tensioning device (ie: bicycle cable tensioner) to allow for adjustable tension Pat Renahan

3Generating tone-lock spasms

Inability to move your foot out of the position in which the nerve fiber locks the muscle

Rapid movement of the foot 2 1 2

Keep the air muscle activation at a slow enough rate to reduce this risk. Full control over this risk is impossible as it is a patient-specific, neurological malfunction Bob Day

4Pressure source attachment points

Air muscle detachment from commercial AFO

Poor material selection/stress-strain analysis 2 3 6

Over-engineer the air muscle attachment point design

Patrick Streeter

5

All attachment points on the AFO that could result in an irritation or pressure sore

Pressure sores or irritations found on patients using device

Rough attachment points to AFO 2 1 2

Smooth padding located on the inside of the commercial AFO, small muscle to AFO attachment points

Patrick Streeter

6

Popping the pressure-fed air muscles when too much or too little counteracting force is applied

Loss of air muscle power, and would result in the need to replace air muscles

Inadequate dynamic analysis or pressure-failure system development 2 3 6

Develop a program that coordinates the firing of the pneumatic system with the gait cycle of the patient Bob Day

7Inadequate 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

8Completion of work within scheduled times

Ladder-effect of other work getting pushed behind, or work-overload at the end of the quarter

Poor project planning and management 2 1 2

Continually update project schedule, and meet bi-weekly at minimum Pat Renahan

9Unbalanced distribution of work load

Different team members carrying the majority of the workload at different points during the design process

Poor distribution of workload and poor project management 2 1 2

Discuss workload and time commitments from the previous week at bi-weekly meetings

10Completing the project within the specified budget

Inability to continue to fund the project through completion

Poor project management and inadequate budget calculations 1 1 1

Develop an in-depth budget, and continually update it as progress continues to be made Pat Renahan

12Over 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

Work in sub-teams of two or greater to allow for a checks and balances system for calculations

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

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

Likelihood scale Severity scale1 - This cause is unlikely to happen 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 - This cause could conceivably happen 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 - This cause is very likely to happen 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

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

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”