P13001: Ankle-Foot Orthotic Tethered, Air Muscle

Planning & Execution

Table of Contents

Project Summary

The primary focus of this project is to design a mechanical device to assist patients who suffer from a condition known as foot drop. Foot drop is caused by nerve damage in the lower leg, which generally results from either a stroke, a degenerative nerve disease such as ALS or Multiple Sclerosis, or in some instances, external trauma. These patients typically lack the ability to lift their foot up (dorsi-flexion), which causes problems while walking. To combat this, most people receive Ankle Foot Orthotics (AFO’s), which generally provide rigid ankle stability with limited flexibility. Many passive devices also exist that use an elastomer hinge to dorsi-flex the foot while no weight is on it. This is an effective method, however it does not address a patient’s ability to walk up and down inclined planes, or down stairs. For these motions, full plantar-flexion is also needed. By replacing the natural muscle function with power from an air muscle, full plantar-flexion can be achieved and assist a patient in stabilizing their gait. The air muscles are lightweight and therefore cause minimal interference with natural human motion. It is important however to make sure the muscle contractions do not impair the gait cycle, or cause injury to the patients.

Since the air muscles need an air supply, the project is going to be limited to a tethered system. The biggest application for a tethered orthotic would be in a clinical setting, either on a treadmill or in a pool. By excluding portable power and a supply tank, it will allow for greater detailing with the actual mechanics of the orthotic. This ideally would pave the way for future groups to focus on untethered systems.

In order to better predict the gait cycle, particularly of a specific patient, the air muscle orthotic will incorporate the use of a terrain sensing mechanism. This system will use two sensors, one of which is binary and measures the vertical motion of stepping, and a second one with a continuous signal mapping changes in the ground ahead. This will allow the AFO to predict the required motion needed for the upcoming terrain. Ideally, the muscles would assist in a smooth step regardless of terrain type, and help minimize “foot slap,” which is a result of not being able to plantar flex well, and/or toe flex.

Ultimately, the device needs to interact well with patients. It is intended to assist with rehabilitation and therefore must be conscious of their health and needs. Normal cooling of the leg should be maintained, sharp edges should be removed to prevent cuts and pressure sores, and it should allow for regular knee function. In addition to being comfortable to wear, a fully functional AFO must also meet all safety criteria and guidelines, and integrate well for a variety of feet and gaits. Without the support of the patients and physical therapists, the device will loose its practical application, and therefore patient interface is an extremely important aspect of the project.

National Science Foundation Disclaimer

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.

Customer Needs

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NOTE: The shaded regions above are low priority objectives, intended more for future generations of this project.


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NOTE: The shaded regions above are low priority specifications, intended more for future generations of this project.

Code of Ethics

What are your expectations for team behavior?

Minimal conflict, and be willing to compromise on major decisions Text other members of the team at least 1 hour before a meeting if you are unable to attend, and had previously said you would Complete all assigned work within set deadlines

How will you ensure balanced distribution of work?

Divide work at the end of every meeting/session and base the distributed work off of each other’s strengths and weaknesses. If one person knows more about a certain aspect of the project, they will not have to do all of the associated work; rather they will lead that aspect of the project and help instruct the others in the group (if need be) as they give their input

How will you determine roles and responsibilities?

Based off of strengths, weaknesses and previous knowledge

How will you honor the strengths of individuals?

By assigning appropriate roles and responsibilities, and by allowing those with specific strengths to be a “sub-project lead” that correlates with their strength

How will you interact with your guide?

We will meet with Dr. DeBartolo on a weekly basis outside of the Friday session to update her on our progress. Dr. DeBartolo will also be a vital resource for helping us integrate previous, similar projects into our work, and helping to keep our project heading in the correct direction.

How will you communicate with each other?

Face-to-face, phone, and email

How will you make decisions?

Democratically. If we come to a point where we are still divided we will bring the issue to our guide if need be.

What are the expectations for integrity or responsibility with assigned tasks?

Solid effort in a professional and timely manner

How will you manage conflict when these expectations are not met?

This will be decided as each situation arises

Project Plans & Schedules

Priority Deadlines:

Fall Week 5 (October 5, 2012): System Design Review

Fall Week 9 (November 2, 2012): Detailed Design Review

Winter Week 5 (January 11, 2013): ASME Biomedical Device Conference Application Submission

Winter Week 10 (February 11, 2013): Project Presentation

Schedule of Action Items

Peer Reviews

Peer Reviews

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