Actuators Complete

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  • 1. BME 601:Superhuman Bionics BME 601:Superhuman Bionics Actuators

2. Actuators:Definition BME 601:Superhuman Bionics BME 601:Superhuman Bionics Signal (electrical, chemical, optical, etc.) Kinetic Energy Example: Electric motor Example:Muscle, Hydraulic Cylinder Amplification LinearRotational Linear/Rotational Energy Conversion Examples: Piston Antagonistic Setup 3. Actuators:Design Goals

  • Simple
  • Large Range of Force / Displacement
    • Fine motor control
  • Fast Response Times
  • Light Weight
  • Low energy input

BME 601:Superhuman Bionics 4. BME 601:Superhuman Bionics BME 601:Superhuman Bionics Electroactive Polymer Actuation Piezoelectric Actuation Pneumatic Actuation Contractile Polymer Actuation ELECTROMAGNETIC ACTUATION METHODS OFACTUATION 5. Actuators:EM Actuation BME 601:Superhuman Bionics BME 601:Superhuman Bionics Electromagnetic ForceF = (I dl)BF 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 6. Actuators:EM Actuation BME 601:Superhuman Bionics BME 601:Superhuman Bionics Electric Motor Theory Brushless Motor 7. BME 601:Superhuman Bionics BME 601:Superhuman Bionics - Linear electromagnetic actuator - Small displacements Actuators:EM Actuation Solenoid Actuator 8. Actuators:EM Actuation BME 601:Superhuman Bionics BME 601:Superhuman Bionics Servo = Electric Motor Reduction Gearbox Displacement Feedback Sensors Shown below, exploded and assembled ProDigit prosthetic finger made by Touch Bionics using servo technology. 9.

  • Advantages
  • Low-cost and reliable based on ~ 50 years of practical use
  • Bidirectional
  • Servo motors - precise displacementsand variable speed
  • Disadvantages
  • Not as energy-efficient as newer actuator designs
  • Spinning parts cause friction - develops large amounts of excess heat
  • Low Strength/Weight ratio

BME 601:Superhuman Bionics BME 601:Superhuman Bionics Actuators:EM Actuation 10.

  • Stress vs. Strain

BME 601:Superhuman Bionics Actuators:Stress/Strain L/L

    • Strain= ratio of length change to original length

= F/S

    • Stress= force applied per unit area

11. BME 601:Superhuman Bionics BME 601:Superhuman Bionics Piezoelectric Actuation Pneumatic Actuation Contractile Polymer Actuation Electromagnetic Actuation ELECTROACTIVE POLYMER ACTUATION METHODS OFACTUATION 12.

  • Voltage gives electrodes opposite charges
  • Plates attract one another displacing polymer

BME 601:Superhuman Bionics BME 601:Superhuman Bionics Actuators:EAP Actuation Electroactive Polymer Theory 13.

  • Critical EAP Performance Properties

BME 601:Superhuman Bionics BME 601:Superhuman Bionics Actuators:EAP Actuation 1.Low Elastic Modulus & Pre-strain Compliant, conductive electrodes Carbon-Impregnated Grease Graphite Mixtures 2.High Poissons RatioIncreasein length is accompanied bydecreasesin width and thickness 14. Actuators:EAP Actuation BME 601:Superhuman Bionics BME 601:Superhuman Bionics Elastomer Examples:Acrylic or Silicone Compounds

  • Critical EAP Performance Properties

3.High Dielectric Constant 4.High Ionization Energy 15. BME 601:Superhuman Bionics BME 601:Superhuman Bionics Actuators:EAP Actuation EAP Actuator Setup Resembling Human Muscle Universal Muscle Actuator Platformfrom ArtificialMuscle, Inc. 2006 Antagonistic setup 16.

  • 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

BME 601:Superhuman Bionics BME 601:Superhuman Bionics Actuators:EAP Actuation 17. BME 601:Superhuman Bionics BME 601:Superhuman Bionics Pneumatic Actuation Contractile Polymer Actuation Electromagnetic Actuation Electroactive Polymer Actuation PIEZOELECTRICACTUATION METHODS OFACTUATION 18. BME 601:Superhuman Bionics BME 601:Superhuman Bionics Actuators:Piezoelectric Direct Piezoelectric Effect Stress Voltage Inverse Piezoelectric Effect Voltage Stress 19. Actuators:Piezoelectric BME 601:Superhuman Bionics BME 601:Superhuman Bionics Performance at Different Voltages Piezoelectric Applications: Vibration Damping, Sound Generation/Detection, Small Valves, Scanning Tunneling Electron and Atomic Force Microscopes, etc. Examples ofPiezoelectric Materials: Quartz, Cane Sugar, Biological Bone Tissue, Some types of Ceramics, Certain Polymers 20.

  • Advantages
  • Simple Operation
  • High Stress Generated
  • Wide operating frequency range
  • Disadvantages
  • Very Low Strain
  • Decreasing Force with Displacement

BME 601:Superhuman Bionics BME 601:Superhuman Bionics Actuators:Piezoelectric 21. BME 601:Superhuman Bionics BME 601:Superhuman Bionics Contractile Polymer Actuation Electromagnetic Actuation Electroactive Polymer Actuation Piezoelectric Actuation PNEUMATICACTUATION METHODS OFACTUATION 22. BME 601:Superhuman Bionics BME 601:Superhuman Bionics Actuators:Pneumatic

  • Air Muscle Structure

Enclosure 23.

  • Air Muscle Contraction

BME 601:Superhuman Bionics BME 601:Superhuman Bionics Actuators:Pneumatic a b c 24. BME 601:Superhuman Bionics BME 601:Superhuman Bionics Actuators:Pneumatic Compliance = Inverse of Stiffness (K) F = Force Developed p = Air Pressure V = Volume of Air l = Length of Muscle

  • Air Muscle Performance

25. BME 601:Superhuman Bionics BME 601:Superhuman Bionics Actuators:Pneumatic

  • Air Muscle Materials

Example:Para-aramid fiber (Kevlar) Examples:Rubber, Polypropylene Hydrogen Bond Pi Bonds (into and out of the page) Elastic Airtight Enclosure Supports Air Pressure Load Stiff, Embedded Fibers Support Tensile Load + 26. BME 601:Superhuman Bionics BME 601:Superhuman Bionics Actuators:Pneumatic Pneumatic Cylinder Air Muscle Greater Displacement, Less Force Greater Force,Less Displacement 27.

  • 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

BME 601:Superhuman Bionics BME 601:Superhuman Bionics Actuators:Pneumatic 28. BME 601:Superhuman Bionics BME 601:Superhuman Bionics Electromagnetic Actuation Electroactive Polymer Actuation Piezoelectric Actuation Pneumatic Actuation CONTRACTILE POLYMER ACTUATION METHODS OFACTUATION 29. BME 601:Superhuman Bionics BME 601:Superhuman Bionics Actuators:Contractile Polymer MIT 1991 Pump-Based Design Polyvinylalcohol Contractile Fibers Volume of acid and base pumped into enclosure dictates contraction

  • Pump Design

30. BME 601:Superhuman Bionics BME 601:Superhuman Bionics Actuators: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 31.

  • Advantages
  • Simplicity
    • electrochemicaldesign eliminates pump system
  • Elasticity
    • - shock absorption
  • Disadvantages
  • Reaction time
  • Corrosive chemicals
  • Unidirectional
  • Weight

BME 601:Superhuman Bionics BME 601:Superhuman Bionics Actuators:Contractile Polymer 32. BME 601:Superhuman Bionics BME 601:Superhuman Bionics Actuators: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 0.3 300) 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 0.3 300) 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 0.3 300) 1(7) >450 60-90 Medium Fast High Piezoelectric Actuators (1.7) (131) >1000 >90 Very Fast Fairly High Air Muscle