Articles

Types of Actuators

What is an Actuator?

Actuators are electro-mechanical or mechanical devices that use a form of power to convert a control signal into mechanical motion. They can be operated electrically, manually, or by various fluids such as hydraulic, air, etc.

Plant automation companies/industrial plants use actuators to operate valves, fluid couplings, dampers, and other devices required for industrial process control. Examples of actuators include Electric motor, Stepper motor, Hydraulic cylinder, Hydraulic actuators, Screw jack, Piezoelectric actuator etc.

When opting an actuator, it must have the below-mentioned performance characteristics as they will enable a control system to perform as designed.

The key actuator performance characteristics are:

•    Actuators must perform consistently and unaltered by load
•    They must have rugged industrial design that is capable of operating in different environments without an effect on performance
•    Minimum periodic maintenance is needed.
•    Actuators must have accurate, repeatable positioning typically better than 0.15% of span
•    An actuator must possess the capability to start and stop immediately without dead time or position overshoot

An actuator containing the above-mentioned performance characteristics provides two advantages:

a) A capability to follow the demand signal from the controller precisely and instantly. This guarantees that an actuator responds exactly as directed by the controller. In this case, it showcases that the actuator is not the limiting factor in the control loop and the controller can function to its optimal levels.

b) When designed with the above performance characteristics, actuators will be more rugged than typical actuators. They will be capable of a much degree of reliability.

Types of Actuators:

Below are the types of actuators:

•    Electric Linear
•    Electric Rotary
•    Fluid Power Linear
•    Fluid Power Rotary
•    Linear Chain Actuators
•    Manual Linear

a) Electric Linear Actuators

Electric Linear Actuators are electrically powered, mechanical devices consisting of motors, linear guides, and drive mechanisms. These actuators are used to convert electrical energy into linear displacement through mechanical transmission, electro-magnetism, or thermal expansion to provide straight line  push/pull motion.

Key Specifications:
Drive type, motor type, the mounting configuration, as well as other physical dimensions and electrical characteristics.

Uses:
•    They are used in automation applications when a machine component, tool etc requires a controlled movement to a particular position.
•    Electric Linear Actuators are extensively used in a wide range of industries where linear  positioning is required

Applications
Typical applications include opening and closing dampers, locking doors, braking machine motions, etc.

b) Electric Rotary

Electric Rotary Actuators are used to convert electrical energy into rotational motion. They are electrically powered, mechanical devices containing motors and output shafts mechanisms with limited rotary travel.

Key Specifications:
They include the intended application, drive method, output configurations, number of positions, mounting configuration, as well as physical dimensions and electrical characteristics as required.

Uses:
They are used in automation applications when a gate, valve, etc. requires controlled movement to particular rotational positions. They are used in a wide range of industries where positioning is needed.

Applications
Typical applications of  Electric Rotary Actuators include quarter-turn valves, windows, robotics, etc.

c) Fluid Power Linear

Fluid Power Linear Actuators are mechanical devices containing cylinder and piston mechanisms that produce linear displacement by means of hydraulic fluid, gas, or differential air pressure.

Key Specifications:
They include the intended application, fluid power type, mounting configuration, travel length, and force capacities, as well as physical dimensions as required.

Uses:
Fluid power linear actuators are used primarily in automation applications when an item requires a controlled movement to a particular position. They are used in a wide range of industries where linear positioning is needed.

Applications
Typical applications include the opening and closing of damper doors, clamping, welding, etc.

d) Linear Chain Actuators

Linear Chain Actuators are mechanical devices that contain sprockets and sections of chain that are used for providing linear motion via the free ends of the specially designed chains.

Key Specifications:
Linear Chain Actuators specifications include the intended application, actuation length, drive method and mechanism, chain size, and the mounting configuration.

Uses:
They are used in motion control applications for providing a straight line push or pull motion.

e) Manual Linear Actuators

Manual linear actuators provide linear displacement through the translation of manually rotated screws or gears. They consist of hand operated knobs or wheels, gearboxes, and guided linear mechanisms.

Key Specifications:
The key specifications of manual linear actuators include intended application, actuator type, drive mechanisms, travel length, and other physical dimensions as required.

Uses:
These kind of actuators are used primarily in commercial applications for positioning such as manipulating tools or workpieces. They have a rotating knob or hand wheel to operate.