Actuators are devices used to produce action or motion.

Input(mainly electrical signal , air, fluids)

Electrical signal can be low power or high power.

Actuators output can be position or rate i. e.linear displacement or velocity.

Actuation can be from few microns to few meters

APower

amplification & modulation

Energy conversion

Control signal

Actuator

Output

Unmodulate Energy source

Linear actuator: solenoid, Hydraulic/Pneumatic.

Rotary actuator: motor, Hydraulic/Pneumatic.

A solenoid is a coil wound into a tightly packed helix.

In physics, the term solenoid refers to a long, thin loop of wire, and wrapped around a metallic core.

which produces a magnetic field when an electric current is passed through it.

Pneumatic valve.

Car door openers.

Hydraulic cylinder

Single pressure line

Hydraulic systems are used to control & transmit power.

A pump driven by prime mover (electric motor) creates flow of fluid

Linear actuator (hydraulic cylinder)-Provides motion in straight line.Linear displacement depends on stroke length.Usually referred to as cylinders, rams (single acting cylinders) or jacks.

Rotary actuators (Hydraulic motors)-Produces continuous rotational motion.Pump shaft is rotated to generate flow.A motor shaft is caused to rotate by fluid being forced into the driving chambers.

Semi rotary actuators-Produces non-continuous rotational motion.Limited to less than one revolution (<360°).Used to produce oscillatory motions in mechanisms.

Hydraulic jack.

Hydraulic brake.

Hydraulic ram.

Used as sensor.Close loop velocity controlling.Highly precise positioning for heavy loads.

It convert energy formed by compressed air at high pressure into ether linear or rotary motion. Quickly respond in operation.

Pneumatic actuatorPneumatic actuator

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Hydraulic & pneumatic actuators: cylindersHydraulic & pneumatic actuators: cylinders

Single acting: work can be done only in one direction

Piston

Double acting piston:

Piston rod on both sides

Plunger

Work is done in both directions

TelescopicTelescopic

Tandem

Non cushioned cylinders are suitable for full stroke working at slow speed.

Higher speeds with external cushions.

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Rotary hydraulic actuatorsRotary hydraulic actuators

Vane rotary actuator: Limited angle in both directions.

Maximum angle always smaller than 360°

The same torque in both directions.

Piston rotary actuator: With rack and gear coupling.

Here maximum angle may be larger than 360°

Limited angle rotary actuator

Limited angle rotary actuator

Parallel piston rotary

actuator

Mechanical linear actuators typically operate by conversion of rotary motion into linear motion.

Screw

Wheel and axle

Cam

Electrically actuated system are very widely used in control system

There are three types of motor used in control system

D.C. motor

A.C. motor Stepper motor

Every motor works on the principle that when a current-carrying conductor is placed in a magnetic field, it experiences a mechanical force.

Working Principle of motor

A.C. motor

Stepper motor

Permanent magnet type

Variable reluctance type

Hybrid type

A stepper motor is an electromechanical device which converts electrical pulses into discrete mechanical movements.

Pierre and Jacques Curie discovered the piezoelectric effect in 1880.

The application of an electric field to a piezoelectric crystal leads to a physical deformation of the crystal.

Piezoelectric materials are: Quartz, Ceramics, PZT(lead zirconate titanade). Advantages

short response time.An ability to create high forces.A high efficiency and a high mechanical durability.

Disadvantage

Have small strains. (0.1-.2%)High supply voltage needed.(60-1000V)Large hysteresis.(actuator doesn’t go back to exactly where it started).

A piezo ceramic crystal is coated with silver on both sides.

Glued to a brass, nickel alloy, or stainless steel disk.

Brass:Commercial & industrial use.(not subjected to environment )

Nickel alloy:

Use where it subjected to environment.

Stainless steel:Uses where it subjected to solvent, corrosive chemical, Underwater .Medical fields.

Piezoelectric Stack ActuatorsProduce linear motion.

Heaters - used with temperature sensors And temperature controller to control the temperature in automated moulding Equipment and in soldering operation.

Lights - Lights are used on almost all machines to indicate the machine state and provide feedback to the operator.

LEDLCD’sGas plasma displayCRT

Sirens/Horns - Sirens or horns can be useful for unattended or dangerous machines to make conditions well known.