SBC2013-14689:Un-Tethered, Active Ankle-Foot Orthotic

Rochester Institute of TechnologyRochester, NY

Team Members:◦Pattie Schiotis – Team Manager (ME)◦Shane Reardon – Lead Engineer (ME)◦Dana Kjolner (EE)◦Robert Ellsworth (EE)◦Sam Hosig (CE)◦John Williams (CE)

•Faculty Guide: Dr. Elizabeth DeBartolo

The Team

Introduction Project Background Key Customer Needs System Architecture Component Breakdown

◦ Mechanical Locking System◦ Electronics Circuit and PCB◦ Sensors◦ Microcontroller

Testing Results Future Work Demo

Agenda

Inability to dorsiflex the foot due to loss of control of peroneal nerve

Lasting side effect of a stroke, affecting approximately 20% of stroke survivors◦ ~20 million people per year

Condition can also occur as a side effect of ALS (Lou Gherig's Disease), Multiple Sclerosis, or injury to the peroneal nerve, increasing the number of people affected

People with this condition have difficulty maintaining a proper gait cycle◦ “Foot crash”

Project Background: Foot Drop

Patients have adopted the use of ankle foot orthotics (AFOs) to aid with dorsi flexion

Market consists mostly of “passive” devices◦ Rigid braces which prevent unwanted plantar flexion. Foot is always pointed in

the upwards direction.

These devices do not allow for safe maneuvering down stairs and ramps

The goal of this project is to design and develop an “active” AFO which allows safe movement on flat surfaces as well as up and down stairs and ramps

Project Background: AFO Market

User will have no ability to either plantar-flex or dorsi-flex their foot

Side to side stability of the foot will be ignored

Worst case will be analyzed:◦ 95 percentile male having heavy foot.◦ Fast walker – gait cycle less than 1 second.

Device may not use air muscles as an actuation source

AFO Custom made for each client

Assumptions & Constraints

Key Customer NeedsPrimary Needs: Secondary Needs:

Safety Portable

◦ Lasts all day without charging/refueling

◦ Lightweight◦ Tolerable to wear all day

Reliable Accommodates Flat Terrain Accommodates Special

Terrain◦ Stairs◦ Ramps◦ Obstacles

Comfortable◦ Aesthetically Pleasing

Durable◦ Water Resistant◦ Corrosion Resistant

Salt & Environment Biocompatibility

Convenient◦ Easy to put on and take

off

Key Engineering Specifications

Spec Number Engineering Specification Description Units of

MeasureNominal

Value

s1 Torque on Foot ft-lbf ±2

s2 System response time (sensing terrain to actuating device) ms <400

s4 predicts step down yes/no yess5 predict flat yes/no yess7 predicts ramp down yes/no yes

s10 allowable range of motion between foot and shin degrees 70 to 135

s12 untethered usage time hrs/steps 10 hrs/ 3000 steps

s17 force to secure constraints lbf < 18s18 force to remove constraints lbf < 18s23 radius of edges/corners on AFO in <0.02

s24 weight of entire device lbf ≤2.2

s28 Operates in environment temperature range °F 0-100

CAD modelSystem Architecture

Sensors

Piston/Cylinder

Mounting Bracket

Valve

Battery

Processor

Reservoir

Concept: Selectively prevent foot from plantar flexing while off the ground

Piston-cylinder arrangement attached posterior to heal and calf via 2 pin joints

Piston actuates within cylinder as dorsi & plantar flexion occurs

Mechanical Locking System

Mechanical Locking System

“Locked” Mode “Free” Mode

Valve on top of the cylinder is closed

Water inside cylinder is compressed by piston upon plantar-flexion

Motion of piston is therefore restricted, preventing plantar flexion

Valve is open Water is free to travel

between cylinder and reservoir upon actuation of piston

Allows for plantar and dorsi flexion

Electronic Circuit and Board Design

Charger ConnectorD 1

D 1N 4002

Micro Controller and SensorsM1

IR F 530

V 112V

VBSD 1 -S IP

6

24

V O U TVIN

GND

U 31 2

D 2

D 1N 4002

C 1

100uF

R 2

10k

C 2

100uF

Solenoid

LED

SD CardSwitch

Connector

Utilize sensor system developed by MS student Christopher Sullivan

Vertical sensor determines if the foot is on or off ground

Forward sensors detects upcoming terrain

Sensors

Processing path of microcontroller

Microcontroller

Range of Motion◦ 70.03º-147.27º

Weight of Device◦ 2.42 lbs

Terrain prediction◦ Detects flat, descending stairs and ramps

System Response Time◦ Average ~300ms

Testing Results

Create smaller electronics box◦ Reduce weight, improve aesthetics, switch in correct

location Different battery

◦ Reduce size and weight, improve usage time Recommend using plastic fittings

◦ Weight reduction, corrosion resistance, could not find in store

SD card expansion board◦ Improve data collection

Human Trials with AFO that fits user◦ More accurate data collection

Areas of Improvement

Budget breakdown…

Economic Feasibility

Demonstration

Questions?