Artificial Muscle Actuators Artificial Muscle Actuators for Upper Limb Prosthesesfor Upper Limb Prostheses

Presented by :Presented by :Faranak Farzan andFaranak Farzan andPawel Pietruszczak Pawel Pietruszczak

The Amputee PopulationThe Amputee PopulationNational Center for Health Statistics estimates for the USA:National Center for Health Statistics estimates for the USA:Major amputations occur in 1 out of 300 individuals: 23% of thisMajor amputations occur in 1 out of 300 individuals: 23% of thispopulation represents upper limb amputeespopulation represents upper limb amputeesA continual need for prosthetics, with over 50,000 amputations A continual need for prosthetics, with over 50,000 amputations every year every year Demographics estimate: 60% of amputees are between 21Demographics estimate: 60% of amputees are between 21--64 64 years, 10% under 21 years of ageyears, 10% under 21 years of age

Primary Causes of upper extremity amputation:Primary Causes of upper extremity amputation:–– Trauma: 77%Trauma: 77%–– Congenital: 8.9%Congenital: 8.9%–– Tumor: 8.2%Tumor: 8.2%–– Disease: 5.8%Disease: 5.8%

The Clinical Solution: The Clinical Solution: Upper Extremity ProsthesesUpper Extremity Prostheses

Prosthetics have been around for thousands of years, with Prosthetics have been around for thousands of years, with early prosthetics made out of leather, wood and metalearly prosthetics made out of leather, wood and metal

Development of prosthetics in the past century largely a Development of prosthetics in the past century largely a result of warsresult of warsUS Civil War (1861US Civil War (1861--1865) Government provided prostheses 1865) Government provided prostheses for veteransfor veterans1863 1863 –– invention of rubber: cosmetic dimension to prosthesesinvention of rubber: cosmetic dimension to prostheses

First functional moving hand produced in Russia (1960)First functional moving hand produced in Russia (1960)First commercially available electrical prostheses in the US First commercially available electrical prostheses in the US available since 1980savailable since 1980s

Currently available prosthetics include passive, body powered, Currently available prosthetics include passive, body powered, and electrical prostheses with silicone covers or hooksand electrical prostheses with silicone covers or hooks

Evolution has been towards more extensive control, function Evolution has been towards more extensive control, function and cosmeticsand cosmetics

The Prosthesis Clinical RealityThe Prosthesis Clinical Reality

Of a population of 10,000 new upper limb amputees per year, Of a population of 10,000 new upper limb amputees per year, only half are fitted with a prosthesisonly half are fitted with a prosthesisHalf of those fitted with prosthesis continue to use their Half of those fitted with prosthesis continue to use their replacement limb at the end of a yearreplacement limb at the end of a year3030--50% of patients do not use their prosthetic hand regularly50% of patients do not use their prosthetic hand regularly

Engineering solution must maintain a focus on patient choice Engineering solution must maintain a focus on patient choice to find an optimal solutionto find an optimal solution–– Personal choices: Patient motivation, appearance, performance Personal choices: Patient motivation, appearance, performance

requirementsrequirements–– Work within Patient Limiting Factors: length and degree of Work within Patient Limiting Factors: length and degree of

amputation, weight tolerance, muscle strength, skin condition, samputation, weight tolerance, muscle strength, skin condition, stress tress from activitiesfrom activities

Current SolutionsCurrent SolutionsPassive ProsthesesPassive Prostheses–– Focus on cosmetic issuesFocus on cosmetic issues–– Cosmetic engineering focus: (stain Cosmetic engineering focus: (stain

resistance, natural appearance, durability)resistance, natural appearance, durability)–– Available for prostheses ranging from single Available for prostheses ranging from single

digits, to full limbs and covers for existing digits, to full limbs and covers for existing prosthesesprostheses

AdvantagesAdvantages–– not drawing attention to the prostheses usernot drawing attention to the prostheses user

DisadvantagesDisadvantages–– Low degree of manipulative functionalityLow degree of manipulative functionality–– Addition to a powered prosthesis lowers Addition to a powered prosthesis lowers

mechanical functionalitymechanical functionality

http://www.alatheia.com/

Current SolutionsCurrent SolutionsBodyBody--Powered ProsthesesPowered Prostheses1. Gross body movements 1. Gross body movements -- captured by a harness attached to a cable captured by a harness attached to a cable system that connects to a terminal device (system that connects to a terminal device (ieie hook, hand)hook, hand)–– Patient must have sufficient residual limb length, musculature aPatient must have sufficient residual limb length, musculature and range of nd range of

motionmotion–– minimum ability of one shoulder movement or chest expansionminimum ability of one shoulder movement or chest expansion

2. Finer muscle movements2. Finer muscle movements–– Requires surgical procedure of Requires surgical procedure of CineplastyCineplasty– prior to prosthesis, loops of muscle are surgically isolated and amplified for

movement outputAdvantagesAdvantages: : –– LightweightLightweight–– Increased control due to Increased control due to proprioceptionproprioception (feedback (feedback

from harness system/muscles)from harness system/muscles)–– Low cost Low cost -- makes prosthesis accessiblemakes prosthesis accessible

DisadvantagesDisadvantages::–– Harness system: may be uncomfortable. Control is Harness system: may be uncomfortable. Control is

restrictiverestrictive–– Functional envelope limited from waist to mouthFunctional envelope limited from waist to mouth–– Control movements draw attention to usersControl movements draw attention to users

Current SolutionsCurrent SolutionsExternally Powered ProsthesesExternally Powered Prostheses–– example: UTAH arm (electrically powered)example: UTAH arm (electrically powered)

–– Microprocessor controlledMicroprocessor controlled–– Uses electrical signals from surface Uses electrical signals from surface

electrodes generated by muscle contraction electrodes generated by muscle contraction –– Input control either determined by the Input control either determined by the

magnitude or location of muscle contractionmagnitude or location of muscle contraction

Advantages:Advantages:–– Cosmetically pleasingCosmetically pleasing–– sensitive control of elbow, hand and sensitive control of elbow, hand and

wristwristDisadvantagesDisadvantages–– Learning CurveLearning Curve–– High cost, maintenanceHigh cost, maintenance–– Less user feedbackLess user feedback–– Lacks many degrees of freedomLacks many degrees of freedom

Modeling an Advanced Prosthetic HandModeling an Advanced Prosthetic Hand

Environment ModuleEnvironment ModuleRain, External Forces, Temperature Fluctuation,Rain, External Forces, Temperature Fluctuation,

Assembly ModuleAssembly ModuleMechanical Housing and Structural ElementMechanical Housing and Structural Element

Measurement ModuleMeasurement ModuleForceForce, Pressure, Temperature, Pressure, Temperature

Communication ModuleCommunication ModuleTransmits information between the modules within Transmits information between the modules within

the system (the system (egeg. wires). wires)

Modeling and Advanced Prosthetic HandModeling and Advanced Prosthetic HandActuation ModuleActuation Module

Drives that cause the motion of the hand and produce the Drives that cause the motion of the hand and produce the force needed to carry out activities. (Artificial Muscles)force needed to carry out activities. (Artificial Muscles)

Interface ModuleInterface ModuleThe Link between the user and the interface.The Link between the user and the interface.

egeg. Myoelectric sensors, Neural Interface. Myoelectric sensors, Neural Interface

Processor Module Processor Module Responsible for processing storing and utilizing the informationResponsible for processing storing and utilizing the information provided provided by the interface module and the measurement module.by the interface module and the measurement module.

Software ModuleSoftware ModuleOperating instructions Operating instructions

Defines the algorithm for the processing moduleDefines the algorithm for the processing module

Bradley DiagramBradley Diagram

Electric Signal

Current Developments: Current Developments: Biomechanical ChallengeBiomechanical Challenge

Human hand has 15 joints (including the wrist)Human hand has 15 joints (including the wrist)40 muscles controlling the hand, including intrinsic and 40 muscles controlling the hand, including intrinsic and extrinsicextrinsic

Current goal in a upper limb prosthesis: to mimic all the Current goal in a upper limb prosthesis: to mimic all the motor functions of the human handmotor functions of the human handProvide dexterity: allow a full range of motion, with Provide dexterity: allow a full range of motion, with sufficient force and controlsufficient force and control

Biomechanical ChallengeBiomechanical ChallengeTotal 21 DOF in the human hand Total 21 DOF in the human hand –– (not including wrist)(not including wrist)

InterphalangealInterphalangeal joints: 1 Degree of joints: 1 Degree of Freedom (DOF) Freedom (DOF) –– Flexion/extensionFlexion/extension

MetacarpophalangealMetacarpophalangeal joints: 2 DOF joints: 2 DOF –– flexion/flexion/extension&abductionextension&abduction/adduction/adduction

Thumb joint has additional 2 DOFThumb joint has additional 2 DOFWrist has 6 DOFWrist has 6 DOF

Current Developments: ActuatorsCurrent Developments: Actuators

To meet the constructive and functional needs, To meet the constructive and functional needs, actuators need to aim for:actuators need to aim for:–– LightweightLightweight–– Small sizeSmall size–– Low energy consumptionLow energy consumption–– High TorqueHigh Torque–– Quiet OperationQuiet Operation–– Minimum heat generationMinimum heat generation–– Fast responseFast response–– Easy controlEasy control

ActuatorsActuators

Conventional Actuators– Operating principle is based DC motors–– E.g. DC E.g. DC MicromotorsMicromotors, Servomotors, Hydraulic and Pneumatic actuators, Servomotors, Hydraulic and Pneumatic actuators

Non-conventional Actuators (potential)– Operating principle is based on material’s atomic structure– E.g. Metal alloys, Peizoelectric materials, Polymeric gel type

materials, Electro Active Polymers

Conventional ActuatorsConventional ActuatorsI) DC motorsI) DC motorsCoreless/Brushless DC MicromotorsCoreless/Brushless DC Micromotors

8mm8mm--48mm , 0.1848mm , 0.18--15 Watt15 WattLong operational life, ReliableLong operational life, ReliableResponse to control is sensitive, fast & precise Response to control is sensitive, fast & precise High rotation High rotation Loud distracting noiseLoud distracting noiseLow torque Low torque Weak strength, slow motion &Weak strength, slow motion &gearboxes required to set them in motiongearboxes required to set them in motion

BrushBrush--switch set switch set Requires maintenanceRequires maintenance

Brushless MicromotorsBrushless MicromotorsMore compact More compact Easily fitted into theEasily fitted into the

Prosthetic cavityProsthetic cavityNo brush No brush No maintenanceNo maintenance

Conventional ActuatorsConventional ActuatorsII) ServomotorsII) ServomotorsConsists of DC micromotorConsists of DC micromotorreduction systemreduction systemcontrol system control system

High Torque High Torque Low costLow cost

Sao Carlos Finger: (prototype phase)Sao Carlos Finger: (prototype phase)

InexpensiveInexpensiveLight and compactLight and compact3 3 DofDof per finger (3 phalanges)per finger (3 phalanges)

Hydraulic and Pneumatic ActuatorsHydraulic and Pneumatic ActuatorsPneumatic ActuatorPneumatic Actuator: : IeIe McKibbenMcKibben Artificial MuscleArtificial Muscle

Advantages:Advantages:–– Similar forceSimilar force--length properties of human muscle, but not forcelength properties of human muscle, but not force--velocity propertiesvelocity properties–– Studied extensively, many models developedStudied extensively, many models developedDisadvantages: Disadvantages: –– difficulty in minimizing size of tubes (force proportional to sqdifficulty in minimizing size of tubes (force proportional to square of tube’s radius) uare of tube’s radius) –– low DOFlow DOF–– low operating frequencylow operating frequency–– loud operationloud operation

Hydraulic Actuator:Hydraulic Actuator:–– uses a DC micrometer to generate mechanical energy transferred tuses a DC micrometer to generate mechanical energy transferred to a fluido a fluid–– Motor can generate 0.6 Motor can generate 0.6 MPaMPa of hydraulic pressureof hydraulic pressureAdvantagesAdvantages: : –– High power efficiencyHigh power efficiency–– Amplifiable force outputAmplifiable force outputDisadvantages:Disadvantages:–– Low flexibility Low flexibility –– low DOFlow DOF–– Low operating frequencyLow operating frequency

Unconventional Actuators: PolymersUnconventional Actuators: PolymersUndergo a reasonable amount of strain when exposed to external Undergo a reasonable amount of strain when exposed to external stimulus such as: chemical, thermal, electricalstimulus such as: chemical, thermal, electrical

Abrupt changes in volume, Low mass ,Occupy little space, SimulatAbrupt changes in volume, Low mass ,Occupy little space, Simulate e movements of natural muscles (e.g. Frequency, efficiency, Max movements of natural muscles (e.g. Frequency, efficiency, Max σσ, , Energy/Area, Power/Volume) ,Generate High ForcesEnergy/Area, Power/Volume) ,Generate High Forces

Differ in Composition (gels, solids, liquids) and type of stimulDiffer in Composition (gels, solids, liquids) and type of stimulususPAA PAA PolyacidPolyacid acrylic acrylic change in PH.change in PH.NIPA NIPA NN--isopropylacrylamideisopropylacrylamide thermally stimulatedthermally stimulatedPAM PAM PolyacrylamidePolyacrylamide Electric Field Electric Field

EAPS: ELECTRO ACTIVE POLYMERSEAPS: ELECTRO ACTIVE POLYMERSPlastic that change shape in response to ELECTRICITY.Plastic that change shape in response to ELECTRICITY.

Ionic EAPs Electronic EAPsIonic EAPs Electronic EAPs

Ionic EAPsIonic EAPsWork on the bases of electrochemistryWork on the bases of electrochemistry“Mobility and diffusion of changed ion”“Mobility and diffusion of changed ion”

Pros: Pros: Low voltage ( single digit!) Low voltage ( single digit!)

Can run directly off batteriesCan run directly off batteries(Portable)(Portable)

Cons: Cons: Need to be wet ( coating)Need to be wet ( coating)As long as electricity is on, muscle As long as electricity is on, muscle keeps moving (permanent keeps moving (permanent damgedamge))

Electronic EAPsElectronic EAPsE.g. E.g. elastomerselastomers, acrylic , acrylic elastomerselastomers, ,

electrostrictiveelectrostrictive elastomerselastomers..Driven by electric fieldDriven by electric fieldPros & Cons:Pros & Cons:React quickly React quickly –– deliver strong mechanical forcesdeliver strong mechanical forces

No protective coatingNo protective coatingLow current but High voltage (2Low current but High voltage (2--5 5 KV)KV)

cause uncomfortable shockcause uncomfortable shockPower delivery is a problemPower delivery is a problem

Life Cycle ( more study)Life Cycle ( more study)e.g. Dielectric e.g. Dielectric elastomerselastomers55--10% strain 10 million cycle10% strain 10 million cycle50% area strain 1 million cycle50% area strain 1 million cycle

Piezoelectric ActuatorsPiezoelectric ActuatorsBased on Piezoelectric materials that convert mechanical Based on Piezoelectric materials that convert mechanical displacements (strains) into electrical energydisplacements (strains) into electrical energyAn electrical field is applied to the material creating minute An electrical field is applied to the material creating minute strains that are translated into mechanical energystrains that are translated into mechanical energyRotary and Ultrasonic MotorsRotary and Ultrasonic Motors

Advantages: Advantages: –– High power densityHigh power density–– Small size, low mass, high torqueSmall size, low mass, high torque–– Silent functionSilent function–– Fast responseFast response–– no magnetic fields generatedno magnetic fields generated

Disadvantages:Disadvantages:–– Difficult to build, costlyDifficult to build, costly–– Need high frequency energy Need high frequency energy

sourcessources–– Short service lifeShort service life–– Low efficiency (compared with Low efficiency (compared with

electric)electric)

Shape Memory AlloysShape Memory AlloysEx. NiEx. Ni--Ti wiresTi wiresExhibit the “Shape Memory Effect” : when heated above a Exhibit the “Shape Memory Effect” : when heated above a certain temperature, the material returns to a predetermined certain temperature, the material returns to a predetermined shape and sizeshape and sizeHeating accomplished through flow of electrical current in Heating accomplished through flow of electrical current in materialmaterial

Shape Memory AlloysShape Memory AlloysHas been demonstrated in micro Has been demonstrated in micro robotic and medical applicationsrobotic and medical applications

Successful prototype of a finger with 4 Successful prototype of a finger with 4 DOF (Rutgers Hand (NJ)). Design of 20 DOF (Rutgers Hand (NJ)). Design of 20 DOF hand.DOF hand.

AdvantagesAdvantages–– light weight (good strength)light weight (good strength)–– small size and volume of material, small size and volume of material,

potential for high DOFpotential for high DOF–– low material costlow material cost–– quiet operationquiet operation–– high force density (high grasping high force density (high grasping

strength)strength)

DisadvantagesDisadvantages: : –– temperature temperature hysteresishysteresis --

strain/temperature relationship is strain/temperature relationship is affected. Control/modeling difficultyaffected. Control/modeling difficulty

–– Problems in consecutive flexion/extension Problems in consecutive flexion/extension without adjustment (Rutgers)without adjustment (Rutgers)

–– Low energy efficiency (improved Low energy efficiency (improved actuators provide 53.4N at 14.5W actuators provide 53.4N at 14.5W --> > 6.67N fingertip)6.67N fingertip)

–– Low strain (2%Low strain (2%--8%)8%)–– Limited life cycleLimited life cycle

FutureFutureDevelopment of Control systemDevelopment of Control system

--increased myoelectric signal processingincreased myoelectric signal processing--increased user feedbackincreased user feedback--direct control using input from the braindirect control using input from the brain

Development of ActuatorsDevelopment of Actuators--use of the new materials in novel biomechanical use of the new materials in novel biomechanical

configurationsconfigurations

Questions?Questions?

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