Diapositiva 1

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Actuators
Josep Amat and Alícia Casals Automatic
Control and Computer Engineering Department
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User
External Sensors
Programming and Supervision
Environment
Sensors Interns
Control Unit
Actuators
Mechanical Structure
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ACTUATORS
1 Pneumatic actuators
Cylinders
2 Hydraulic actuadors
Cylinders
Motors
3 Electrical actuators
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1 Pneumatic actuators (cylinders)
Double effect pneumatic cylinders
F P S

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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.
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V
v
- The impact produced when reaching the end of
the run is reduced using a shock absorber.
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Electrical valve
- Electrical valve the hydraulic-electrical
interface
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Distributor
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Double effect cylinders
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Example of commercial pneumatic cylinders
(Lateral guides to prevent axial rotation )
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Oval pistons to prevent the rotation of the axis
avoiding the need of auxiliary guides
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Classical cylinders drawbacks a displacement of
length l requires an additional length l.
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Solutions to reduce the occupied space
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Example of pneumatic manipulator, and its
mechanical states (End positions of all its
cylinders)
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ACTUATORS
1 Pneumatic actuators
Cylinders
Motors
2 Hydraulic actuadors
Cylinders
Motors
3 Electrical actuators
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2 Hydraulic actuators (cylinders)
Dl (cm)
v (cm/seg.)
Energy source oil pressurized between 20 and 300
bars.
- Controllable position
- Controllable speed
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Hydraulic circuit showing its essential elements
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The regulation of the cylinder retention force
regulates the oil output producing a pressure
drop.
Schema of a pressure regulator
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Control
Electrical valve
Ideal characteristic
R
A
P
B
R
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Control
Electrical valve
R
A
P
B
R
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Control
Electrical valve
R
A
P
B
R
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Real characteristic
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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.
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ACTUATORS
1 Pneumatic actuators
Cylinders
Motors
2 Hydraulic actuadors
Cylinders
Motors
3 Electrical actuators
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Fix caudal
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Fix caudal
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Hydraulic pumps
( Kind of radial pistons)
Variable caudal
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Caudal variation as a function of eccentricity e
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Hydraulic pumps and motors
( Kind of blades)
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Hydraulic pumps or motors
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Hydraulic actuators
- Low working speed
- Hydraulic group noisy in operation
- Possible oil leakage