For the sake of this article we will focus on the different types of Actuators that are referred to as Linear Actuators. Linear motion is the to and from motion or axial motion. The word ‘actuators’ refers to a component which is used for moving and controlling the mechanism or a system. Linear actuators are one which is used to convert the rotational motion into linear motion. This conversion of motion can be done either with the help of AC or DC motor or using some hydraulic and pneumatic source. The speed can be varied based on the gear ratio in case of motors. Linear actuators are indeed the best solution when it comes to precise motion or smooth motion control. There are a lot of applications of linear actuators. They have a vital role in automation industries where linear positioning required. Moreover, in the automation industries they are used to control the damper and to adjust the height. They are also used in home automation. Opening and shutting dampers, locking entryways, slowing down machine movements, and so on are the common applications of linear actuators.
Figure 1: Electric linear actuator
There are many types of linear actuators. Some are described here:
Mechanical linear actuator:
These actuators normally works by conversion of rotary motion to the linear motion. The mechanism that is used to make this conversion consist of screw, wheel and axel and cam. The rotary motion of the control knob was converted in to linear motion with the help of screws attach to the knob. Some mechanical actuators are designed to only push while other are made for only pull such as chain drive. Hydraulic and pneumatic cylinders can used to provide force in both direction. Mechanical linear actuators are mostly use in laser and optics etc.
These actuators use pressurized fluid such as oil in order to make linear motion. The design of hydraulic actuator is years old. They are used in the application were high force is required to operate. Beside actuator, there are some other additional equipment such as valves, fluid reservoirs, pumps and motor which is used to reduce the heat and noise that is generated during the functionality. Moreover, they have leakage problem. The common application of this actuator is car hydraulic jack. Hydraulic linear actuators are used in many applications such as engineering machines, marine and aerospace engineering.
Pneumatic linear actuators:
These type of actuators use pressurized gas or air to make linear motion. Like hydraulic actuators, the design of pneumatic linear actuator is very old. The air compressor is used in order to give power to operate the actuator. They are used when high speed is required or when a large amount of linear distance is needed to cover in one second, such as inches per second or 30 inches per second. Once, installed they are had to move from one place to another. The application of pneumatic linear actuators ranges from sensors, switches, door closer etc.
Piezoelectric linear actuators:
These actuators use voltage in order to expand the material, such as ceramic. A large amount of voltage is required for very small change in length. It is used for very small ranges. But can be used in tons of load. They are basically used for scientific purposes.
Electric linear actuators:
In these type of actuators the conversion of motion is done by a single motor. The rotary motion of the motor is then converted to the linear motion. They can be used anywhere, whether to push or pull the load, raise or lower it or even for roughly position it. They can be controlled, hence a feedback system can be made with the help of feedback sensors such as a potentiometer or optical sensor. In this way the motion can be controlled very accurately.
Why are electric linear actuators a good choice?
It is the best option when one wants clean, smooth and simple movement with a great accuracy. Irrespective to hydraulic and pneumatic linear actuators, there is no need for any valves, compressor and other things to hold that fluid. The piezoelectric actuators on the other hand requires a very large voltage for a small change in length. Hence, the electric actuators are budget friendly as compare to all other actuators. Moreover, there is no fear of leakage in the electric actuators. Furthermore, they don’t need a lot of maintenance and the maintenance cost is also very low.
Hence it is the excellent choice for one who want clean and non-toxic conversion of movement from rotary to linear as it full fills all the demands and concern regarding environmental friendly equipment.
More types of electric linear actuators
There are different forms of electric linear actuators which are used depending upon the requirement. Some are explained here:
Feedback linear actuator:
These are the linear actuators that are used for close loop systems. The feedback linear actuators itself have different types based on the sensor that is used in the feedback. The sensors could be potentiometer, optical or hall sensors. In the potentiometer type of feedback actuator, the potentiometer is used to find the position of the actuator by change in the voltage. Similarly, in the optical type, the optical sensor and a rotating disc with holes is attached to the gear box. The position is fed back through light by sending pulse to control box. In the hall sensors effect, the spinning magnetic field is placed in the gearbox. The number of revolutions is counted by sensor through positive negative poles of magnetic field. For some application, there is a need for the feedback in order to control the speed of two motors, the feedback linear actuator is best for those. For accurate positional control you would also need to use an Actuator with some level of feedback technology.
Track linear actuator:
The track linear actuator is same as the typical linear actuator except that its scope of movement is encased in a track rather than in open air. Hence, this is why, it is sensitive to dust and water. Because of the pre-defined path, it can deal with more force as compare to other same physical size actuator. The track linear actuators are best for indoor applications where one requires fix horizontal and vertical motion.
Figure 3: Track linear actuator
Column linear actuator:
The column linear actuator is type of actuator which extends upward while retaining the stability. Because of the multiple stages that column actuators have, they produce a long stock. There are many advantages of column actuator. They are designed for only vertical motion. One of the advantage is that it doesn’t require external guiding as linear guiding is built within the structure of actuator. They can easily be installed without using any other additional supporting brackets. As they have guiding system in their lift, it makes them a better option than any other actuator in various applications such a cabinet lifting etc.
Figure 4: Column linear actuator
Micro Linear Actuators
They’re small, light, quiet and very durable. These electric micro linear actuators are extremely useful to create custom automation in homes, businesses, vehicles, yachts, RV’s, aircraft, robotics, radio control vehicles, multi-copter drones, as well as artistic installations, medical applications and more. A typical Micro Linear Actuator offers a very small compact size with small strokes, their small compact micro size does however mean that they are going to be limited in Force.
Types of motors used in electric linear actuators
AC and DC motors can be used in electric linear actuator. Both of the motor types have some standard ranges. Most commonly Dc motors are used. Among DC motors 12V dc motors are most popular. 24V DC motors are used for large force application. Similarly when it comes AC motors, it could be 220-240V single phase or 220V-240 or 380-415VAC three phase AC motors are used depending upon the industrial applications.
Choosing the right linear actuator for use
In order to choose the right actuator for the application is not a big issue. Indeed, the linear actuators have a lot of application in medical, industrial work or home automation etc. There are some steps that need to be focused while deciding best linear actuator for one’s application. The steps are described below
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Find out the amount of force required
This is the first step in order to find out the correct linear actuator for one’s application. The weight of the object which is needed to lift should be known. Moreover, how the linear actuator should be attached plays a very important role in determining the force which is used to select the actuator.
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Find out the distance actuator need to move
The next step is to find out how far the linear actuator should need to move in order to fulfill the requirements of the task. The stock length determine how far an actuator will go. Depending upon the application, it is chosen weather to have a linear actuator with large stoke length or small stoke length.
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Find out the required speed
The speed requirement would also help in order to select the linear actuator. Whether the task need to move fast or slow. Once it is figured out, the next step is to look the specification sheet in order to determine the speed of the linear actuator. Moreover, as we all know larger the force, slower the speed will be.
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Select the best type of linear actuator
After collecting all the above data, now selection for the type of the linear actuators that fits according to your task. The trach linear actuator is best for the small spaces because it doesn’t extends outwards. Moreover, rod-type actuator is used for simple extension and retraction purposes. If one want to have a long stock with respect to retracted size, then column linear actuator is best for such application.
For help selecting the right Linear Actuator we created a Calculator. Simply enter some basic parameters for your application and the Calculator will give you some options. Visit the Calculator by clicking here
