Intelligent Robotics Laboratory Vanderbilt School of Engineering Artificial Muscle based on Flexinol motor wire Scott Renkes Advisor: David Noelle

Intelligent Robotics LaboratoryVanderbilt School of Engineering

Artificial Muscle based on Artificial Muscle based on Flexinol motor wireFlexinol motor wire

Scott RenkesScott Renkes

Advisor: David NoelleAdvisor: David Noelle


GoalsGoals

Design an actuator that mimics human Design an actuator that mimics human muscle movements using Flexinol motor muscle movements using Flexinol motor wire arranged in a bundle like structurewire arranged in a bundle like structure

Control the actuator with an artificial neural Control the actuator with an artificial neural network that utilizes the properties of the network that utilizes the properties of the motor wiremotor wire

Design the system to be easy to interface, Design the system to be easy to interface, modular and user-friendlymodular and user-friendly


Current TechnologyCurrent Technology

ActuatorActuator ProsPros ConsCons

Electric Electric MotorsMotors

Light weightLight weight

Low power Low power consumptionconsumption

Limited torqueLimited torque

Stress on axelStress on axel

HydraulicsHydraulics High forceHigh force HeavyHeavy

Pump requiredPump required

PneumaticsPneumatics Medium forceMedium force

ElasticElastic

Non linearNon linear

Pump requiredPump required


Why a new actuator?Why a new actuator?

Replicate human movementReplicate human movement Reduce stress on userReduce stress on user Better human interactionBetter human interaction

Refined force and velocity control of deviceRefined force and velocity control of device Utilize the function approximation of controllerUtilize the function approximation of controller

Human like movement allows for better man Human like movement allows for better man machine integrationmachine integration Less training timeLess training time

Humanoid robots can more easily mimic humansHumanoid robots can more easily mimic humans Robot more acceptableRobot more acceptable


FlexinolFlexinol

DensityDensity

(g/cc)(g/cc)

Energy Energy conversion conversion EfficiencyEfficiency

(%)(%)

Max Max Deformation Deformation

RatioRatio

(%)(%)

Breaking Breaking StrengthStrength

(MPa)(MPa)

MuscleMuscle 1.041.04 2525 33 72527252

FlexinolFlexinol 6.456.45 55 88 1,0001,000

Shape memory alloyShape memory alloy Returns to memorized shape when stimulatedReturns to memorized shape when stimulated Heat stimulusHeat stimulus Only responds to stretchingOnly responds to stretching


Fibrous Bundled StructureFibrous Bundled Structure

Flexinol motor wire to Flexinol motor wire to replace muscle fibersreplace muscle fibers

Package wires similar Package wires similar to muscleto muscle

Flexinol/muscle fiber Flexinol/muscle fiber proportional elasticityproportional elasticity

Similar force/length Similar force/length curvescurves


RecruitmentRecruitment

One bundle, one neuronOne bundle, one neuron Weak fast, slow strongWeak fast, slow strong Properties of motor wire Properties of motor wire

allow for variety of activationallow for variety of activation Neural Network ControllerNeural Network Controller Force feedback trainingForce feedback training Inverse Dynamics Inverse Dynamics


FeedbackFeedback

Force feedbackForce feedback Golgi tendon organGolgi tendon organ Strain gaugeStrain gauge

Length feedbackLength feedback Muscle spindleMuscle spindle Approximation of Approximation of

Flexinol propertiesFlexinol properties

nawrot.psych.ndsu.nodak.edu/ .../Movement/Reflex.html


Flexinol PropertiesFlexinol Properties

DiameterDiameter

(mm)(mm)Linear Linear ResistanceResistance

/m)/m)

Max Max currentcurrent

(A)(A)

Deformation Deformation WeightWeight

(g)(g)

Recovery Recovery WeightWeight

(g)(g)

Typical Typical RateRate

(cyc/min)(cyc/min)

Max Max

PowerPower

(Watt)(Watt)

3737 860860 0.30.3 44 2020 5555 60.560.5

100100 150150 1.81.8 2828 150150 4343 11.3411.34

250250 3131 6.16.1 110110 930930 1919 4.864.86

375375 88 27.527.5 393393 20002000 55 0.7740.774


Neural Net RecruitingNeural Net Recruiting

Back Propagation Back Propagation NetworkNetwork

Neural Net Neural Net ImplementationImplementation ComputerComputer IC to Operation Voltage IC to Operation Voltage

AmplifierAmplifier Force ControlledForce Controlled

Force feedbackForce feedback Desired ForceDesired Force Maximize F/t^2Maximize F/t^2

Ensure recruitmentEnsure recruitment


Force Length ComparisonForce Length Comparison

Muscle Force LengthMuscle Force Length See figureSee figure

Flexinol Force LengthFlexinol Force Length Steeper slopes Steeper slopes

Nature of Force Nature of Force Length RelationshipLength Relationship TensionTension stretchstretch


EMG ControllerEMG Controller

Muscle Voltage vs Muscle Voltage vs Muscle ForceMuscle Force

EMG signals represent EMG signals represent muscle forcemuscle force

Neural Network for EMG Neural Network for EMG pattern recognitionpattern recognition Scaled EMG of biscep as Scaled EMG of biscep as

inputinput Desired force as ouputDesired force as ouput

Relative to min and maxRelative to min and max The green line is bicep voltage

The blue line is tricep voltage

3 and 4 are unused channels


Circuit DiagramCircuit Diagram


Artificial Muscle ImplementationArtificial Muscle Implementation

LoadBundle

Insertion Point

Strain Gauge+ -

CrimpTendon TendonCrimp


Sneak Preview Mk1Sneak Preview Mk1


Sneak Preview Mk2Sneak Preview Mk2


Mass productionMass production

Actuator is single wireActuator is single wire n loop n loop coil tension equalizedcoil tension equalized each end crimped to wireeach end crimped to wire

Epoxy to attach “tendon”Epoxy to attach “tendon” Coated for biological applicationsCoated for biological applications Portable battery and controllersPortable battery and controllers


CostCost

1 meter each1 meter each Flexinol HT 375Flexinol HT 375 Flexinol HT 200Flexinol HT 200 Flexinol HT 100Flexinol HT 100 Flexinol HT 037Flexinol HT 037

Microprocessor X 2Microprocessor X 2 MultiplexerMultiplexer Voltage AmplifierVoltage Amplifier WiringWiring EpoxyEpoxy CableCable

TotalTotal

$22.95$22.95 $19.95$19.95 $17.95$17.95 $16.95$16.95

$50.00$50.00 $8.00$8.00 $10.00$10.00 $10.00$10.00 $8.00$8.00 $8.00$8.00

$171.80$171.80


Project StatusProject Status

Completed workCompleted work Study properties of motor wireStudy properties of motor wire Calculate efficiency of passive coolingCalculate efficiency of passive cooling Develop Structure and Control for the deviceDevelop Structure and Control for the device Design test bedDesign test bed Build actuatorBuild actuator

Current WorkCurrent Work Finish neural network controllerFinish neural network controller


Future WorkFuture Work

Examine biocompatibilityExamine biocompatibility Calculate mass production costsCalculate mass production costs Evaluate production and market feasibilityEvaluate production and market feasibility


Questions?Questions?

Documents

Intelligent Robotics Laboratory Vanderbilt School of Engineering Artificial Muscle based on Flexinol motor wire Scott Renkes Advisor: David Noelle