How does Linear Actuator work?
Defined simply, an actuator is a device that converts energy, which may be electric, hydraulic, pneumatic, etc., to mechanical in such a way that it can be controlled. The quantity and the nature of input depend on the kind of energy to be converted and the function of the actuator. Electric and piezoelectric actuators, for instance, work on the input of electric current or voltage, for hydraulic actuators, its incompressible liquid, and for pneumatic actuators, the input is air. The output is always mechanical energy.
Actuators are not something you would read about every day in media, unlike artificial intelligence and machine learning. But the reality is that it plays a critical role in the modern world almost like no other device ever invented.
In the industrial mechatronics systems, for instance, they are solely responsible for ensuring a device such as a robotic arm is able to move when electric input is provided. Your car uses actuators in the engine control system to regulate air flaps for torque and optimization of power, idle speed, and fuel management for ideal combustion.
Actuators are not something you would read about every day in media, unlike artificial intelligence and machine learning. But the reality is that it plays a critical role in the modern world almost like no other device ever invented.
They are not just seen in large applications. At home, actuators are the critical devices that help you to set up consoles or cabinets that could hold televisions and can be opened at the touch of a button. They are also seen in TV and table lifts which users can adjust through electric switches or buttons at their convenience.
Fancy a recliner to watch the TV? In all likelihood, it has a movable head or footrest that uses an actuator too. Home automation systems that can intuitively close window blinds depending on the amount of light streaming in are also dependent on actuators. In short, their use is endless because any mechanical movement requires them, and most devices require some form of mechanical movement.
Following are the usual components that are part of the functioning of an actuator:
- Power source: This provides the energy input that is necessary to drive the actuator. These are often electric or fluid in nature in the industrial sectors.
- Power converter: The role of the power converter is to supply power from the source to the actuator in accordance with the measurements set by the controller. Hydraulic proportional valves and electrical inverters are examples of power converters in industrial systems.
- Actuator: The actual device that converts the supplied energy to mechanical force.
- Mechanical load: The energy converted by the actuator is usually used to make a mechanical device function. The mechanical load refers to this mechanical system that is being driven by the actuator.
- Controller: A controller ensures that the system functions seamlessly with the appropriate input quantities and other setpoints decided by an operator.
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Selecting a Linear actuator
As we have seen already, actuators have myriad applications in different fields. But this doesn’t mean that all actuators are made equal. When purchasing an actuator, you should be able to know which suits your requirements best. Here is a comprehensive guide on how to choose the right actuator for your needs.
Step 1. Assess the movement required:
Does the object you need to move in your project require linear or rotary movement? Linear actuators are useful in exerting a mechanical force that would move an object in a straight line while rotary actuators, as the name suggests, generate circular motion.
Step 2: Consider the energy input:
Electrical actuators are becoming more and more popular due to their increasing sophistication and flexibility in handling various kinds of operations. But that doesn’t mean it's suited for every work out there. Consider hydraulic or pneumatic actuators if your work does not include electrical voltage input.
Step 3: Assess the precision level required:
Some actuators are ideal for heavy-duty work in rough environments, but they may not work well when it comes to handling smaller work like packaging which requires precision and the ability to repeat the same action hundreds or thousands of times.
Step 4 : Find out how much force you need:
The purpose of an actuator is to move or lift an object. Find out, in your case, how much this object weighs. The load capacity of an actuator decides how much it can lift, and although many actuators may look similar, their load capacity will vary. Before you buy an actuator, make sure the weight of your object matches the capacity of the actuator.
Step 5: Find out how far you need the object moved:
Distance, or stroke length as it is technically known, matters here. The stroke length decides how far your object can be moved. Manufacturers often sell actuators of varying stroke length.
Step 6: How fast do you want the movement to be:
The speed of the actuator is often an important factor for most people, depending on their project. Usually, projects that require actuators to exert high force would move slower than those that generate low force. Speed of an actuator is measured in distance per second.
Step 7: Consider the operating environment:
Does the actuator need to work in a rugged or rough environment, where dust or humidity is a concern? If this is the case, you would want to choose a product with higher protection rating.
Step 8: Decide on the mounting style:
Actuators in the market come in different mounting styles and understanding their benefits is necessary before buying an actuator. For instance, a dual-pivot mounting method in a linear electric actuator allows the device to pivot on both sides while extending and retracting. With this, the application gets to have two free pivot points while moving on a fixed path.
Conversely, stationary mounting, which secures the actuator to an object along the shaft, is useful for actions such as pushing a button. At this stage, you should be able to narrow down your options to a significantly smaller pool from where you started. From here, you will need to narrow down further. For instance, linear actuators come in different styles for different kinds of functions. Rod-style, for instance, is the most common and simple among them, with a shaft that expands and retracts. Track style, which does not change its overall length or size during operations are more suited when space constraints are an issue. There are also column lifts and other actuators that would be ideal for setting up TV and table lifts. Factors such as operating voltage and motor type may also be worth considering.
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Capabilities of a Linear Actuator
Performance metrics are quantifiable outputs that help you evaluate the quality of a particular product. Actuators can be considered under several performance metrics. Traditionally, most common among them have been torque, speed, and durability. These days, energy efficiency is also considered equally important. Other factors that may be considered include volume, mass, operating conditions, etc.
Torque or force
Naturally, torque is one of the most important aspects to consider in the performance of an actuator. A key factor here is to note that there are two kinds of torque metric to consider, static and dynamic load. Static load torque or force refers to the actuator’s capacity when it is at rest. The dynamic metric refers to the device’s torque capacity when it is in motion.
Speed
Speed of an actuator differs depending on the weight of the load it is supposed to carry. Usually, the higher the weight, the lower the speed. Hence the speed metric should first be looked at when the actuator is not carrying any load.
Durability
The type of actuator and the manufacturer’s design decides the durability of an actuator. Although those such as hydraulic actuators are considered more durable and rugged compared to electric actuators, the detail specs on the quality of the material used will be up to the manufacturer.
Energy efficiency
With increasing concerns on energy conservation and its direct impact on operational costs, energy efficiency is becoming more and more a decisive metric in all kinds of machinery. Here the lesser the quantity of energy required for an actuator to achieve its goal, the better.
How to connect linear actuators
Given the broad spectrum of actuators that are out there, different methods are used to connect them to the control. Connecting an electric linear actuator is a rather simple process. Many electric linear actuators come with four pins these days and their connection is as simple as plugging them in. However, if your actuator does not have four pins, the process is slightly different. You will need to buy an additional connector, which often comes in 6- and 2-foot length.
- Prepare the wires
- Connect the wires
- All set
Your actuator might come with wires exposed at the end. You can strip back this a bit if required before connecting to a 4-pin connector. If the connector’s wire is not exposed enough, strip that back as well.
Connect the linear actuator to the 4-pin connector by twisting the right exposed wires together and covering it up with electrical tape. Often the wires on the actuator and connector come in blue and brown colors and they can be connected accordingly.
Sometimes, the colors may be different on the actuator. For example, if the actuator has red and black wires, connect the red to the brown wire of the actuator and black to the blue. If it comes with red and blue, connect the red to the brown and blue to the blue wire on the connector. If the wires of the actuator are red and yellow, connect red to the brown wire and yellow to the blue wire.
Now you are good to go. Plugin your connector and plug in the control box to the power socket. In case you run into trouble despite this, click here for a more detailed guide on connecting actuator to a connector.
A complete A-Z guide on how to select, test and implement linear motion for any application. Written by engineers, for engineers.
How to mount a linear actuator
Choosing an actuator and connecting it properly is only half the job done. Equally important is mounting the actuator in a method that is right for your application. Below are two common methods that are used to mount an electric linear actuator.
Dual pivot mounting
This method involves fixing an actuator on both sides with a mounting point that is free to pivot, which usually consists of a mounting pin or a clevis. Dual pivot mounting allows the actuator to pivot on either side as it extends and retracts, allowing the application to achieve a fixed path motion with two free pivot points.
One of the most useful applications of this method is to open and close doors. When the actuator extends, the dual fixed points enable the door to swing open. The action of the door closing and opening causes changes in angle, but the pivot provides ample space for the two mounting points to rotate. While using this method, make sure that there is enough room for the actuator to extend, without any obstacles on its way.
Stationary mounting
In this method, the actuator is mounted in a stationary position with a shaft mounting bracket fixing it to the shaft. Common uses of this kind of mounting are to achieve action similar to pushing something head-on. For instance, this form of mounting is ideal for switching a button on or off. When deciding on this method, ensure that the mounting apparatus can handle the load of the actuator.
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Linear Actuator Applications & Capabilities
The uses of linear electric actuators are virtually endless. Manufacturing plants use them in material handling. Cutting equipment that moves up and down and valves that control flow of raw materials are examples of this. Robots and robotic arms within and outside the manufacturing industry also make use of linear actuator systems to achieve movement in a straight line.
As automation trends become increasingly popular, customers are always looking for ways to implement linear actuators into their applications.
With home automation systems becoming popular, electric linear actuators have become useful in the function of automated window shades. Home appliances like TV can be placed at optimum height without hassle using TV lifts that make use of linear electric actuators. There are also table lifts which use actuators to adjust the height to the needs of users.
In the solar power industry, they help in moving the panels to the direction of the sunlight. Even in industries like agriculture, where heavy machinery that uses hydraulic actuators are more common, electric linear actuators are used for fine and delicate movements.
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