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Actuators

Actuators. Josep Amat and Alícia Casals Automatic Control and Computer Engineering Department . User. External Sensors. Programming and Supervision. Environment. Sensors Interns. Control Unit. Actuators. Mechanical Structure. Dc motors. Ac motors. Steeper motors. ACTUATORS.

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Actuators

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  1. Actuators Josep Amat and Alícia Casals Automatic Control and Computer Engineering Department

  2. User External Sensors Programming and Supervision Environment Sensors Interns Control Unit Actuators Mechanical Structure

  3. Dc motors. Ac motors Steeper motors. ACTUATORS 1 – Pneumatic actuators Cylinders 2 – Hydraulic actuadors Cylinders Motors 3 – Electrical actuators

  4. 1 – Pneumatic actuators (cylinders) Double effect pneumatic cylinders F = P S *

  5. v a F = P S * P S - k v2 * * a = F - Ff = M a * M Ff = k v2 * V Speed is not controllable. The cylinder maximum speed is achieved when friction forces (kv2) equal those that produce the advancing movement (F = P.S), and a = 0.

  6. v v a a V v - The impact produced when reaching the end of the run is reduced using a shock absorber.

  7. Electrical valve - Electrical valve: the hydraulic-electrical interface

  8. Distributor

  9. Single effect cylinders Double effect cylinders

  10. Example of commercial pneumatic cylinders (Lateral guides to prevent axial rotation )

  11. Oval pistons to prevent the rotation of the axis avoiding the need of auxiliary guides

  12. l l 2 Classical cylinders drawbacks: a displacement of length l requires an additional length l.

  13. Dl l Solutions to reduce the occupied space

  14. Movement transmission Adjusting band Shock-absorber adjustment Cylinder’s sleeve Piston Adjusting band

  15. Pneumatic actuators (cylinders) - Economic - Reliable - High operation speed - Operation at constant force - Resistant to overloads - No speed control - Poor position speed - Noisy operation

  16. Example of pneumatic manipulator, and its mechanical states (End positions of all its cylinders)

  17. Dc motors. Ac motors Steeper motors. ACTUATORS 1 – Pneumatic actuators Cylinders Motors 2 – Hydraulic actuadors Cylinders Motors 3 – Electrical actuators

  18. Dv (cm3) Q (l/min) ∞ If P ^^ F  F = P S * 2 – Hydraulic actuators (cylinders) Dl(cm) v (cm/seg.) Energy source: oil pressurized between 20 and 300 bars. - Controllable position - Controllable speed

  19. Control Electrical valve R P Pressure regulator M B Pressure Refrigeration Level Temperature Hydraulic circuit showing its essential elements

  20. Atm. P The regulation of the cylinder retention force regulates the oil output producing a pressure drop. Schema of a pressure regulator

  21. QA d QB R P d Control Electrical valve Ideal characteristic R A P B R

  22. QA d QB R P d Control Electrical valve R A P B R

  23. QA d QB R P d Control Electrical valve R A P B R

  24. QA d Control Electrical valve QB R P R A P B R d Real characteristic

  25. QA QB Sensor Control Servo valve R P Control A Set point QA QB Qo B Sensor d The use of a position sensor d makes the position servo control possible and thus hysteresis is minimized. The dead zone is minimized as well.

  26. Dc motors. Ac motors Steeper motors. ACTUATORS 1 – Pneumatic actuators Cylinders Motors 2 – Hydraulic actuadors Cylinders Motors 3 – Electrical actuators

  27. Hydraulic pumps and motors ( Kind of gears) Fix caudal

  28. Hydraulic pumps and motors ( Kind of gears) Fix caudal

  29. Cylindrical pumps Hydraulic pumps ( Kind of radial pistons) Variable caudal

  30. e e Caudal variation as a function of eccentricity e

  31. Hydraulic pumps and motors ( Kind of blades)

  32. Hydraulic pumps or motors

  33. - Economic - Reliable - Able to support heavy loads - Resistant to overloads Hydraulic actuators - Low working speed - Hydraulic group noisy in operation - Possible oil leakage

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