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BME 601: Superhuman Bionics 1 BME 601: Superhuman Bionics Actuators Actuators

Actuators Complete

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Page 1: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 11BME 601: Superhuman BionicsBME 601: Superhuman Bionics

ActuatorsActuatorsActuatorsActuators

Page 2: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 22BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Actuators: DefinitionActuators: Definition

Signal (electrical, chemical, optical, etc.)

Kinetic Energy

Example: Electric

motor Example: Muscle, Hydraulic Cylinder

Amplification

Linear Rotational

Linear/Rotational Energy Conversion

Examples:

Piston Antagonistic Setup

Page 3: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 33

Actuators: Design GoalsActuators: Design Goals

1. Simple

2. Large Range of Force / Displacement Fine motor control

3. Fast Response Times

4. Light Weight

5. Low energy input

1. Simple

2. Large Range of Force / Displacement Fine motor control

3. Fast Response Times

4. Light Weight

5. Low energy input

Page 4: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 44BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Electroactive PolymerActuation

PiezoelectricActuation

PneumaticActuation

Contractile PolymerActuation

ELECTROMAGNETICACTUATION

METHODS OF ACTUATION

Page 5: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 55BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Actuators: EM ActuationActuators: EM Actuation

Electromagnetic Force F = (I·dl) × B

F is the electromagnetic force on a moving charge

I is the current magnitude and dl is the direction of the current

B is the magnetic field

Page 6: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 66BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Actuators: EM ActuationActuators: EM Actuation

Electric Motor Theory Brushless Motor

Page 7: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 77BME 601: Superhuman BionicsBME 601: Superhuman Bionics

- Linear electromagnetic actuator

- Small displacements

Actuators: EM ActuationActuators: EM Actuation

Solenoid Actuator

Page 8: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 88BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Actuators: EM ActuationActuators: EM Actuation

Shown below, exploded and assembled – ProDigit prosthetic finger made by Touch Bionics using servo technology.

Servo =Electric Motor

Reduction Gearbox

Displacement Feedback Sensors

Page 9: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 99BME 601: Superhuman BionicsBME 601: Superhuman Bionics

AdvantagesLow-cost and reliable

based on ~ 50 years of practical use

Bidirectional

Servo motors - precise displacements and variable speed

AdvantagesLow-cost and reliable

based on ~ 50 years of practical use

Bidirectional

Servo motors - precise displacements and variable speed

DisadvantagesNot as energy-efficient

as newer actuator designs

Spinning parts cause friction - develops large amounts of excess heat

Low Strength/Weight ratio

DisadvantagesNot as energy-efficient

as newer actuator designs

Spinning parts cause friction - develops large amounts of excess heat

Low Strength/Weight ratio

Actuators: EM ActuationActuators: EM Actuation

Page 10: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 1010

Stress vs. StrainStress vs. Strain

Actuators: Stress/StrainActuators: Stress/Strain

L/LStrain = ratio of length change to original length

= F/SStress = force applied per unit area

Page 11: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 1111BME 601: Superhuman BionicsBME 601: Superhuman Bionics

PiezoelectricActuation

PneumaticActuation

Contractile PolymerActuation

ElectromagneticActuation

ELECTROACTIVE POLYMERACTUATION

METHODS OF ACTUATION

Page 12: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 1212BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Actuators: EAP ActuationActuators: EAP Actuation

Electroactive Polymer Theory

Voltage gives electrodes opposite charges

Plates attract one another displacing polymer

Voltage gives electrodes opposite charges

Plates attract one another displacing polymer

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BME 601: Superhuman BionicsBME 601: Superhuman Bionics 1313BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Actuators: EAP ActuationActuators: EAP Actuation

1. Low Elastic Modulus & Pre-strain

Compliant, conductive electrodesCarbon-Impregnated Grease

Graphite Mixtures

Critical EAP Performance Properties Critical EAP Performance Properties

2. High Poisson’s Ratio Increase in length is accompanied by decreases in width and thickness

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BME 601: Superhuman BionicsBME 601: Superhuman Bionics 1414BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Actuators: EAP ActuationActuators: EAP Actuation

3. High Dielectric Constant 4. High Ionization Energy

Elastomer Examples: Acrylic or Silicone Compounds

Critical EAP Performance Properties Critical EAP Performance Properties

Page 15: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 1515BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Actuators: EAP ActuationActuators: EAP Actuation

EAP Actuator Setup Resembling Human Muscle

Universal Muscle Actuator Platform from Artificial Muscle, Inc. 2006

Antagonistic setup

Page 16: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 1616BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Advantages Simple design and

operation Elastic – shock

absorption High speed Wide operating

frequency range Recovers electric

potential returning to original state

Strength/Weight ratio Pre-strain Cost

Advantages Simple design and

operation Elastic – shock

absorption High speed Wide operating

frequency range Recovers electric

potential returning to original state

Strength/Weight ratio Pre-strain Cost

Disadvantages Force decreases with

displacement Unidirectional Elasticity – lower

displacement precision

Disadvantages Force decreases with

displacement Unidirectional Elasticity – lower

displacement precision

Actuators: EAP ActuationActuators: EAP Actuation

Page 17: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 1717BME 601: Superhuman BionicsBME 601: Superhuman Bionics

PneumaticActuation

Contractile PolymerActuation

ElectromagneticActuation

Electroactive PolymerActuation

PIEZOELECTRIC ACTUATION

METHODS OF ACTUATION

Page 18: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 1818BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Actuators: PiezoelectricActuators: Piezoelectric

Direct Piezoelectric Effect

Stress Voltage

Inverse Piezoelectric Effect

Voltage Stress

Page 19: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 1919BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Actuators: PiezoelectricActuators: Piezoelectric

Performance at Different VoltagesPiezoelectric Applications:

Vibration Damping, Sound Generation/Detection, Small Valves, Scanning Tunneling Electron and Atomic Force

Microscopes, etc.

Examples of Piezoelectric Materials:

Quartz, Cane Sugar, Biological Bone Tissue,

Some types of Ceramics, Certain Polymers

Page 20: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 2020BME 601: Superhuman BionicsBME 601: Superhuman Bionics

AdvantagesSimple Operation

High Stress Generated

Wide operating frequency range

AdvantagesSimple Operation

High Stress Generated

Wide operating frequency range

DisadvantagesVery Low Strain

Decreasing Force with Displacement

DisadvantagesVery Low Strain

Decreasing Force with Displacement

Actuators: PiezoelectricActuators: Piezoelectric

Page 21: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 2121BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Contractile PolymerActuation

Electromagnetic Actuation

Electroactive PolymerActuation

PiezoelectricActuation

PNEUMATIC ACTUATION

METHODS OF ACTUATION

Page 22: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 2222BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Actuators: PneumaticActuators: Pneumatic

Air Muscle Structure Air Muscle Structure

Enclosure

Page 23: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 2323BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Actuators: PneumaticActuators: Pneumatic

Air Muscle Contraction Air Muscle Contraction

a b c

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BME 601: Superhuman BionicsBME 601: Superhuman Bionics 2424BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Actuators: PneumaticActuators: Pneumatic

Compliance = Inverse of

Stiffness (K)

F = Force Developed

p = Air Pressure

V = Volume of Air

l = Length of Muscle

Air Muscle Performance Air Muscle Performance

Page 25: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 2525BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Actuators: PneumaticActuators: Pneumatic

Example: Para-aramid fiber (Kevlar)Examples: Rubber, Polypropylene

Hydrogen Bond

Pi Bonds (into and out of the page)

Air Muscle Materials Air Muscle Materials

Elastic Airtight Enclosure Supports Air Pressure Load

Stiff, Embedded Fibers Support Tensile Load+

Page 26: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 2626BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Actuators: PneumaticActuators: Pneumatic

Pneumatic Cylinder Air Muscle

Greater Displacement, Less Force

Greater Force, Less Displacement

Page 27: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 2727BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Advantages

Resemblance to biological muscle

Weight & Strength

Contraction speed

Simplicity

Compliance of air – shock absorption

Advantages

Resemblance to biological muscle

Weight & Strength

Contraction speed

Simplicity

Compliance of air – shock absorption

Disadvantages

Unidirectional

Force decreases with displacement

Compliance – decreased precision

Airtight enclosure failure due to trauma

Disadvantages

Unidirectional

Force decreases with displacement

Compliance – decreased precision

Airtight enclosure failure due to trauma

Actuators: PneumaticActuators: Pneumatic

Page 28: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 2828BME 601: Superhuman BionicsBME 601: Superhuman Bionics

ElectromagneticActuation

Electroactive PolymerActuation

PiezoelectricActuation

PneumaticActuation

CONTRACTILE POLYMERACTUATION

METHODS OF ACTUATION

Page 29: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 2929BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Actuators: Contractile PolymerActuators: Contractile Polymer

MIT 1991 – Pump-Based Design Polyvinylalcohol Contractile Fibers

Volume of acid and base pumped into enclosure dictates contraction

Pump Design Pump Design

Page 30: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 3030BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Actuators: Contractile PolymerActuators: Contractile Polymer

University of Nevada and Environmental Robots, Inc. 2006 Electrochemical Design, Polyacrylonitrile Contractile Fibers

Voltage Potential Across Electrodes

Electrolysis in NaCl Solution

Anode attracts H+ Ions

Local pH Gradient Around Polyacrylonitrile

Page 31: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 3131BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Advantages

Simplicity- electrochemical

design eliminates pump system

Elasticity

- shock absorption

Advantages

Simplicity- electrochemical

design eliminates pump system

Elasticity

- shock absorption

Disadvantages

Reaction time

Corrosive chemicals

Unidirectional

Weight

Disadvantages

Reaction time

Corrosive chemicals

Unidirectional

Weight

Actuators: Contractile PolymerActuators: Contractile Polymer

Page 32: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 3232BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Actuators: ConclusionsActuators: Conclusions

Actuator Type Typical (Max) Strain (%)

Typical (Max) Stress(MPa)

Peak Strain rate (%/s)

Est. Max Efficiency (%)

Relative Speed (full cycle)

Relative Strength to Weight Ratio

Biological Skeletal Muscle

20(40) 0.1(0.35) >50 ? Medium Very High

Electromagnetic Actuators(Solenoid-Motor)

50-N/A 0.1-N/A 1000-200 80-50 Fast-Medium Low

Electroactive Polymer Actuators

25(>300) 1(7) >450 60-90 Medium Fast High

Piezoelectric Actuators

(1.7) (131) >1000 >90 Very Fast Fairly High

Air Muscles 20(40) 0.3(1) 200 ? Medium High

Contractile Polymer Actuators

>40 0.3 <<1 30 Very Slow Low

Page 33: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 3333BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Actuators: ConclusionsActuators: Conclusions

Actuator Type Typical (Max) Strain (%)

Typical (Max) Stress(MPa)

Peak Strain rate (%/s)

Est. Max Efficiency (%)

Relative Speed (full cycle)

Relative Strength to Weight Ratio

Biological Skeletal Muscle

20(40) 0.1(0.35) >50 ? Medium Very High

Electromagnetic Actuators(Solenoid-Motor)

50-N/A 0.1-N/A 1000-200 80-50 Fast-Medium Low

Electroactive Polymer Actuators

25(>300) 1(7) >450 60-90 Medium Fast High

Piezoelectric Actuators

(1.7) (131) >1000 >90 Very Fast Fairly High

Air Muscles 20(40) 0.3(1) 200 ? Medium High

Contractile Polymer Actuators

>40 0.3 <<1 30 Very Slow Low

Page 34: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 3434BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Actuators: ConclusionsActuators: Conclusions

Actuator Type Typical (Max) Strain (%)

Typical (Max) Stress(MPa)

Peak Strain rate (%/s)

Est. Max Efficiency (%)

Relative Speed (full cycle)

Relative Strength to Weight Ratio

Biological Skeletal Muscle

20(40) 0.1(0.35) >50 ? Medium Very High

Electromagnetic Actuators(Solenoid-Motor)

50-N/A 0.1-N/A 1000-200 80-50 Fast-Medium Low

Electroactive Polymer Actuators

25(>300) 1(7) >450 60-90 Medium Fast High

Piezoelectric Actuators

(1.7) (131) >1000 >90 Very Fast Fairly High

Air Muscles 20(40) 0.3(1) 200 ? Medium High

Contractile Polymer Actuators

>40 0.3 <<1 30 Very Slow Low

Page 35: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 3535BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Actuators: ConclusionsActuators: Conclusions

Actuator Type Typical (Max) Strain (%)

Typical (Max) Stress(MPa)

Peak Strain rate (%/s)

Est. Max Efficiency (%)

Relative Speed (full cycle)

Relative Strength to Weight Ratio

Biological Skeletal Muscle

20(40) 0.1(0.35) >50 ? Medium Very High

Electromagnetic Actuators(Solenoid-Motor)

50-N/A 0.1-N/A 1000-200 80-50 Fast-Medium Low

Electroactive Polymer Actuators

25(>300) 1(7) >450 60-90 Medium Fast High

Piezoelectric Actuators

(1.7) (131) >1000 >90 Very Fast Fairly High

Air Muscles 20(40) 0.3(1) 200 ? Medium High

Contractile Polymer Actuators

>40 0.3 <<1 30 Very Slow Low

Page 36: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 3636BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Actuators: ConclusionsActuators: Conclusions

Actuator Type Typical (Max) Strain (%)

Typical (Max) Stress(MPa)

Peak Strain rate (%/s)

Est. Max Efficiency (%)

Relative Speed (full cycle)

Relative Strength to Weight Ratio

Biological Skeletal Muscle

20(40) 0.1(0.35) >50 ? Medium Very High

Electromagnetic Actuators(Solenoid-Motor)

50-N/A 0.1-N/A 1000-200 80-50 Fast-Medium Low

Electroactive Polymer Actuators

25(>300) 1(7) >450 60-90 Medium Fast High

Piezoelectric Actuators

(1.7) (131) >1000 >90 Very Fast Fairly High

Air Muscles 20(40) 0.3(1) 200 ? Medium High

Contractile Polymer Actuators

>40 0.3 <<1 30 Very Slow Low

Page 37: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 3737BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Actuators: ConclusionsActuators: Conclusions

Actuator Type Typical (Max) Strain (%)

Typical (Max) Stress(MPa)

Peak Strain rate (%/s)

Est. Max Efficiency (%)

Relative Speed (full cycle)

Relative Strength to Weight Ratio

Biological Skeletal Muscle

20(40) 0.1(0.35) >50 ? Medium Very High

Electromagnetic Actuators(Solenoid-Motor)

50-N/A 0.1-N/A 1000-200 80-50 Fast-Medium Low

Electroactive Polymer Actuators

25(>300) 1(7) >450 60-90 Medium Fast High

Piezoelectric Actuators

(1.7) (131) >1000 >90 Very Fast Fairly High

Air Muscles 20(40) 0.3(1) 200 ? Medium High

Contractile Polymer Actuators

>40 0.3 <<1 30 Very Slow Low

Page 38: Actuators Complete

BME 601: Superhuman BionicsBME 601: Superhuman Bionics 3838BME 601: Superhuman BionicsBME 601: Superhuman Bionics

Actuators: ConclusionsActuators: Conclusions

Actuator Type Typical (Max) Strain (%)

Typical (Max) Stress(MPa)

Peak Strain rate (%/s)

Est. Max Efficiency (%)

Relative Speed (full cycle)

Relative Strength to Weight Ratio

Biological Skeletal Muscle

20(40) 0.1(0.35) >50 ? Medium Very High

Electromagnetic Actuators(Solenoid-Motor)

50-N/A 0.1-N/A 1000-200 80-50 Fast-Medium Low

Electroactive Polymer Actuators

25(>300) 1(7) >450 60-90 Medium Fast High

Piezoelectric Actuators

(1.7) (131) >1000 >90 Very Fast Fairly High

Air Muscles 20(40) 0.3(1) 200 ? Medium High

Contractile Polymer Actuators

>40 0.3 <<1 30 Very Slow Low