Wearable Essential Wearable Essential Tremor SolutionTremor Solution

University of FloridaUniversity of FloridaBiomedical EngineeringBiomedical Engineering

Jason Winters, Philip Jason Winters, Philip BarishBarish, Nikita , Nikita AgarwalAgarwal, , Jennifer Jackson ,Ethan Sherman, Tang TeJennifer Jackson ,Ethan Sherman, Tang Te

What is Essential Tremor?What is Essential Tremor?

Common neurological disorderCommon neurological disorderShaking of hands and headShaking of hands and headOccurs during intentional movementsOccurs during intentional movementsCan affect almost any part of the bodyCan affect almost any part of the body

Head, neck, torso, legs, tongue, voiceHead, neck, torso, legs, tongue, voiceAffects 10 million Americans (mostly over Affects 10 million Americans (mostly over 60 years old)60 years old)Not linked to other diseasesNot linked to other diseases

Essential Tremor PatientEssential Tremor Patient

(click picture to watch video)

Patients drawings show improvement with medication

EffectsEffects

Not debilitating, but is distressingNot debilitating, but is distressingSocial embarrassmentSocial embarrassmentCan lead to depressionCan lead to depressionEveryday tasks and those requiring fine Everyday tasks and those requiring fine motor skills are difficultmotor skills are difficult

Decrease in quality of lifeDecrease in quality of life

Current SolutionsCurrent Solutions

Deep Brain Stimulation (Thalamus)Deep Brain Stimulation (Thalamus)MedicationMedicationMechanical RestraintsMechanical RestraintsModerate alcohol consumptionModerate alcohol consumption

Neater Eater Bledsoe Arm Brace

Project GoalProject Goal

Design a wearable device to mechanically Design a wearable device to mechanically or electrically alter or minimize tremor.or electrically alter or minimize tremor.

Solutions ConsideredSolutions Considered

GyroscopesGyroscopesResistance bandsResistance bandsWorkstation with fixed objectsWorkstation with fixed objectsActive servo controlActive servo controlMuscle stimulationMuscle stimulationMechanical DampingMechanical Damping

Initial Design Initial Design Servo Assisted Servo Assisted MovementMovement

ComputerComputer--controlled controlled feedback systemfeedback systemResists high Resists high frequency tremor frequency tremor motion motion Allows motion only Allows motion only under persistent force under persistent force (low frequency)(low frequency)Measures current Measures current needed to maintain needed to maintain positionposition

MaterialsMaterials

Hobby servo (Futaba S3003)Hobby servo (Futaba S3003)Servo control board (NetMediaServo control board (NetMedias SRV8s SRV8--T)T)Power sourcePower sourceVisual Basic programVisual Basic programGraphical displayGraphical display

System ComponentsSystem Components

Computer running visual basic control software

6Vbattery

servo control circuit

Futaba S3003 servo

RS-232 link

Theory of OperationTheory of Operation

tremor

Intended motion

Reset condition

Intended motion timer triggered

Actual motion of servo & couple joint

Time (sec)A

ppro

xim

atio

n of

Tor

que

0 4.0

torque trigger threshold

Drawbacks with DesignDrawbacks with Design

Relies on software to decide patients Relies on software to decide patients intended movementsintended movementsComplicatedComplicatedRequires power sourceRequires power sourceNot waterproofNot waterproofDelicate mechanismDelicate mechanism

Final Design Final Design Viscous Damper DeviceViscous Damper Device

Single DOF Single DOF mechanism allowing mechanism allowing flexion/extension flexion/extension motion of wristmotion of wristSuppresses high Suppresses high frequency tremor but frequency tremor but permits slower permits slower movements using movements using viscous dampingviscous dampingAttaches to forearm Attaches to forearm and hand

(click picture to watch video)and hand

System ComponentsSystem Componentslinkage dashpotsfinger loop frame

elastic bandage

adjustable valve

finger loop rail hinge joint

ConstructionConstruction

Frame made of 6061 Frame made of 6061 alumimunalumimun alloyalloyElastic bandage attached to frame using Elastic bandage attached to frame using 22--part epoxypart epoxy

Dashpots adapted from 10ml plastic Dashpots adapted from 10ml plastic syringessyringes

Dashpot carriage held together with Dashpot carriage held together with 22--part epoxypart epoxyWater used as viscous fluid (dye added for Water used as viscous fluid (dye added for visibility)visibility)

Viscous DampeningViscous Dampening

Dissipates energy by Dissipates energy by restricting viscous fluid restricting viscous fluid flow though small orificeflow though small orificeDamping force is Damping force is proportional to vibrating proportional to vibrating bodybody

F = cv

flow restricting orifice

velocity

damping force

viscous fluid

F = damping force

c = dampening coefficient

v = velocity of piston

(Piston in cylinder dashpot arrangement)

Double dashpot designDouble dashpot design

Opposing dashpots Opposing dashpots attached to one attached to one carriagecarriageDashpots function as Dashpots function as reservoirs as wellreservoirs as wellOvercomes Overcomes suction suction cavitationcavitation problem of problem of single dashpot designsingle dashpot designConvenient place for Convenient place for flow restriction valveflow restriction valve (click picture to watch video)

Essential Tremor SimulationsEssential Tremor Simulations

Mass

Simple massSimple mass--springspring--damper simulation damper simulation shows influence of mechanical dampening shows influence of mechanical dampening on tremor on tremor

spring (k)damper (c)

xF(t)

mx + cx + kx = F(t).. .

Normal Movement SimulationNormal Movement Simulation

(click picture to watch video)

Movement with Essential TremorMovement with Essential Tremor

(click picture to watch video)

Essential Tremor Patient with DampingEssential Tremor Patient with Damping

(click picture to watch video)

Slower movements but motion from tremor is suppressed.

Attachment to BodyAttachment to Body

Elastic bandage with VelcroElastic bandage with Velcro provides provides adjustable yet secure attachment to adjustable yet secure attachment to forearm.forearm.Finger loop holds rail tight to back of hand Finger loop holds rail tight to back of hand but allows translation along length but allows translation along length

Needed since wrist joint and device hinge Needed since wrist joint and device hinge joint arenjoint arent coincidentt coincident

General Device InformationGeneral Device Information

Minimum torque required to overcome Minimum torque required to overcome mechanical friction = 0.37 Nmmechanical friction = 0.37 Nm

Equivalent to flexion of wrist while Equivalent to flexion of wrist while gripping 1 pound weightgripping 1 pound weight

Total range of motion = 100 Total range of motion = 100 Flexion: 60Flexion: 60ExtentionExtention: 40: 40

Device weight = 10 ozDevice weight = 10 oz

ValidationValidationtrial 1 (Hz) trial 2 (Hz) trial 3 (Hz)

Test 1 2.35 2.45 2.3Test 2 1 1.3 1.25Test 3 0.8 0.95 0.9

Duration = 20 secTest 1: no deviceTest 2: device on, stopcock open fullTest 3: device on, stopcock mostly closed

Frequency

User was asked to cycle device as many times as possible in given time.

Mean Frequency Comparison Between Different Tests

0

0.5

1

1.5

2

2.5

3

Test 1 Test 2 Test 3

Freq

uenc

y (H

z)

Mean

Damping constant has clear effect on motion suppression.

AdvantagesAdvantages

Damping force adapts to tremor vibrationDamping force adapts to tremor vibrationEasily adjustable damping constantEasily adjustable damping constantRequires no power sourceRequires no power sourceSimpleSimpleInexpensiveInexpensiveRobustRobust

Design IssuesDesign Issues

Attachment to the bodyAttachment to the bodySlight play with the hingeSlight play with the hingeLeaks possible under heavy loadingLeaks possible under heavy loadingDifficult to attach to body on oneDifficult to attach to body on ones owns ownPatient testing neededPatient testing needed

Future ImplementationFuture Implementation

Currently designed for wrist joint but can Currently designed for wrist joint but can be applied to other hinge joints (i.e. elbow)be applied to other hinge joints (i.e. elbow)

More joints need damping to greatly suppress More joints need damping to greatly suppress tremortremor

High precision machining to reduce play in High precision machining to reduce play in linkageslinkagesCustom molded cuffs for easier Custom molded cuffs for easier attachment to bodyattachment to bodyMore compact designMore compact design

Wearable Essential Tremor SolutionWhat is Essential Tremor?Essential Tremor PatientEffectsCurrent SolutionsProject GoalSolutions ConsideredInitial Design Servo Assisted MovementMaterialsSystem ComponentsTheory of OperationDrawbacks with DesignFinal Design Viscous Damper DeviceSystem ComponentsConstructionViscous DampeningDouble dashpot designEssential Tremor SimulationsNormal Movement SimulationMovement with Essential TremorEssential Tremor Patient with DampingAttachment to BodyGeneral Device InformationValidationAdvantagesDesign IssuesFuture Implementation