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ACTUATOR

An actuator is a mechanical device for moving or controlling a mechanism or system. It takes energy, usually transported by air, electric current, or liquid, and converts that into some kind of motion. or A device used to transfer motion from one object to another is called an actuator. It activates a movement or a process.
Actuators are typically used in manufacturing or industrial applications and may be used in things like motors, pumps, switches, and valves. In engineering, actuators are frequently used as mechanisms to introduce motion, or to clamp an object so as to prevent motion.

In electronic engineering, actuators are a subdivision of transducers. They can create a linear motion, rotary motion, or oscillatory motion. That is, they can create motion in one direction, in a circular motion, or in opposite directions at regular intervals. Hydraulic and air cylinders are classified as single acting, meaning that the energy source causes movement in one direction and a spring in the other direction.

TYPES OF ACTUATORS

There are basically two types of actuators.

Rotary actuator:

That produces a rotary motion or torque. e.g. stepper motor, servo motor.

Rotary actuator

Electric rotary valve actuator controlling a butterfly valve

Linear Actuators:

Linear actuators translate rotary motion into linear motion. There are several types of linear actuators, the most common of them are following;

^Mechanical actuators
^Hydraulic actuators
^Pneumatic actuators
^Piezoelectric actuators
^Electro-mechanical actuators

Mechanical actuators

Mechanical Actuators are used as a mechanism to translate mechanical motion (often rotary) into linear motion or with the help of gearing into rotary motion at a different speed. These actuators are typically part of a larger system which includes a power drive, mechanical interconnects, and feedback devices to control the motion of multiple devices. Mechanical linear actuators operate by conversion of rotary motion into linear motion. Conversion is commonly made via a few simple types of mechanism.

Screw:

Screw jack, ball screw and roller screw actuators all operate on the principle of the simple machine known as the screw. By rotating the actuator’s nut, the screw shaft moves in a line. By moving the screw shaft, the nut rotates.

Wheel and axle:

rack and pinion, chain drive, belt drive, rigid chain and rigid belt actuators operate on the principle of the wheel and axle. By rotating a wheel/axle (e.g. drum, gear, pulley or shaft) a linear member (e.g. cable, rack, chain or belt) moves. By moving the linear member, the wheel/axle rotates.

rack and pinion

Advantages:
^They are Cheap.
^Repeatable.
^No power source required. Thy have Self contained power source.
^Identical behavior extending or retracting.
Disadvantages:
^Manual operation only. No automation.

Hydraulic actuators

Hydraulic actuators operate with minimal mechanical parts. They use fluid to pressurize pistons used to facilitate mechanical operation. As hydraulic fluid is incompressible, hydraulic actuators typically take longer to gain speed and power while requiring more time to slow back down. Because they are more commonly used over extended periods of time in power equipment that will run steadily with infrequent stops, they can also be equipped with fail-safe features to permit quick stops for emergency conditions.

Hydraulic actuator

Pneumatic actuators

Pneumatic actuators, or pneumatic cylinders, use compressed gas to provide pressure instead of a liquid. These actuators also operate with minimal parts. They use air to pressurize pistons. Pneumatic actuators do not require regulation because of air’s compressibility. As the power source does not need to be stored in reserve for operation, pneumatic actuators can respond quickly in starting and stopping, which makes them more desirable for mechanical equipment that requires frequent changes in pressure to execute a desired result.
Pneumatic actuator

Piezoelectric actuators

The Piezoelectric effect is a property of certain materials in which application of a voltage to the material causes it to expand. Very high voltages correspond to only tiny expansions. As a result, piezoelectric actuators can achieve extremely fine positioning resolution, but also have a very short range of motion. In addition, piezoelectric materials exhibit hysteresis which makes it difficult to control their expansion in a repeatable manner.
Piezoelectric actuators

Advantages

Compactness and light weight, rapid response, practically unlimited resolution, no magnetic field, large force generation, broad operating frequency range, high stability, solid state, low power consumption, proportional to the applied voltage displacement, and 50% and more energy conversion efficiency.

Applications

micro manipulation, noise and vibration suppression systems, valves, lasers, Optics, ultrasonic motors, positioning devices, relays, pumps, in automotive industry, industrial automation Systems, telecommunications, computers, and so forth.

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Reference

What are Actuators and Different Types of Actuators?

 

 

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