actuators complete
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BME 601: Superhuman BionicsBME 601: Superhuman Bionics 11BME 601: Superhuman BionicsBME 601: Superhuman Bionics
ActuatorsActuatorsActuatorsActuators
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
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
BME 601: Superhuman BionicsBME 601: Superhuman Bionics 44BME 601: Superhuman BionicsBME 601: Superhuman Bionics
Electroactive PolymerActuation
PiezoelectricActuation
PneumaticActuation
Contractile PolymerActuation
ELECTROMAGNETICACTUATION
METHODS OF ACTUATION
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
BME 601: Superhuman BionicsBME 601: Superhuman Bionics 66BME 601: Superhuman BionicsBME 601: Superhuman Bionics
Actuators: EM ActuationActuators: EM Actuation
Electric Motor Theory Brushless Motor
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
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
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
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
BME 601: Superhuman BionicsBME 601: Superhuman Bionics 1111BME 601: Superhuman BionicsBME 601: Superhuman Bionics
PiezoelectricActuation
PneumaticActuation
Contractile PolymerActuation
ElectromagneticActuation
ELECTROACTIVE POLYMERACTUATION
METHODS OF ACTUATION
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
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
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
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
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
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
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
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
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
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
BME 601: Superhuman BionicsBME 601: Superhuman Bionics 2222BME 601: Superhuman BionicsBME 601: Superhuman Bionics
Actuators: PneumaticActuators: Pneumatic
Air Muscle Structure Air Muscle Structure
Enclosure
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
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
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+
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
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
BME 601: Superhuman BionicsBME 601: Superhuman Bionics 2828BME 601: Superhuman BionicsBME 601: Superhuman Bionics
ElectromagneticActuation
Electroactive PolymerActuation
PiezoelectricActuation
PneumaticActuation
CONTRACTILE POLYMERACTUATION
METHODS OF ACTUATION
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
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
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
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
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
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
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
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
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
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
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