Linear Actuator, Its Functions and Applications

What is a linear actuator?

An actuator is used to move or transfer entities in mechanical, electro-mechanical industries. A linear actuator is one which converts any type of motion into linear motion.
Input energy for these actuators can be of any type. In simple words it means that they can be operated using hydraulic, pnumatic, or electric energies.

How a linear actuator works?

Different types of actuators and their working is given below in detail.

Mechanical actuator

If an actuator is energized using hydraulic pressures, it is called mechanical actuator. They can be operated using different techniques –
1. Screw - They operate using the principle of screw. The actuator's nut is rotated and accordingly , the screw shaft moves in a line.
2. Wheel and axle- A wheel or axle is moved and linear member moves in its accordance.) A linear member can be in any form such as a cable, rack, chain or belt.
3. Cam: They run on a principle of the wedge, but they give relatively limited travel. As a wheel-like cam moves in circular motion, its eccentric shape gives a thrust at the base of a shaft.

Hydraulic Actuators

Hydraulic actuators give pressure to a piston kept in a hollow cylinder. The movement happens at the axis.

Pneumatic Actuators

Pneumatic actuator uses compressed gas to give pressure in place of a liquid.

Piezoelectric actuators

This actuator is brought in use where short range of motion is needed. It also gives very high control of linear motor.

Electro-mechanical actuators

As the name tells, this is a mechanical actuator operated using an electric motor.

The pros and cons of the above actuator types are listed below.

1. A mechanical actuator is cost effective, repeatable. No power source is required. It is self contained. It has same behavior while extending or retracting. But they have manual operation only. No automation is possible.
2. Hydraulic actuator can be used for very high forces. The problem is it can leak. It requires position feedback for repeatability. Also, external hydraulic pump required. Some are good in compression only.
3. Pneumatic actuator is strong, is light weight, and has simple functioning. The speed is fast. The main problem is its position control is not possible except at full stops.
4. Electro-mechanical actuator is cheap in cost. It is repeatable. Its operation can be automated. It is self-contained. It also has identical behavior extending or retracting. Position feedback of electro-mechanical actuators is possible. The flip side its moving parts are prone to wear.

A standard linear actuator commonly has the motor as a separate cylinder attached to the side of the actuator, It is attached either in parallel way with the actuator or it sticks out to the side 90 degrees to the actuator. Motion control also plays an important role in the working of this device.The motor may also be attached to the back of the actuator. The drive motor has a solid drive shaft. This shaft is geared to the drive nut or drive screw.

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