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