Actuators - What is an Actuator?

The Basics of Linear Actuators

An actuator is a mechanism that converts energy into movement, creating mechanical force to drive motion. It operates by taking input energy and translating it into either linear or rotary motion, making it a key component in machinery.

Actuators are a fundamental part of our lives, and are a widely used device that makes its way into every facet of your existence and its importance in the modern world can't be under-estimated. In fact, actuators are the key for making almost every machine move once an electrical energy source is provided.

Lets learn about the main types of actuators and their various applications across industries and understand how actuators operate, how you connect to them and move things.

What is an Actuator

An actuator is the part of any machine that lets it create motion. Just like the muscles in the human body allow legs, arms, fingers, and other parts to move, the actuator is the component that enables movement in mechanical apparatus.

It does this by converting incoming energy and signals into a mechanical force. This incoming force can be electric, pneumatic (air), or hydraulic (water), while the outgoing motion can be rotary or linear.

Linear Actuators are present in everything around us, from the access control systems on our doors to the robots doing the heavy lifting at the local warehouse. Even our mobile phones have actuators to create vibrations when they're turned on silent.

Different Types of Actuators

Electric actuators are motor-driven and tend to trigger other circuitry functions. They are powered using an electrical current and typically used within control systems. These types of linear actuators carry numerous benefits: they are simple to build or apply, carry minimal noise, and are cost and energy-efficient. Their downsides are that they are low speed and inappropriate for heavy loads.

Hydraulic actuators, on the other hand, can handle a burden of over 10 kilonewtons. A typical hydraulic actuator is a piston-like actuator comprised of a cylinder, piston, and spring. It also requires a hydraulic supply and return line and stem. They can handle high-force applications and don't need to be located near their pumps and motors while retaining the same power. They do have disadvantages, however, in that they can leak fluid, which can cost them efficiency and cause potential damage. They also need various ancillary parts like release valves, hoses, tanks, and regulators.

Pneumatic actuators sit somewhere in between electricity and hydraulic in terms of capability and can handle small to large loads. Pneumatic actuators use compressed air or gas to move a piston along a hollow cylinder and build pressure to move the load. Pneumatic actuators are generally lauded for the fast motion they create but like hydraulic actuators, they require complementary parts like valves, tubes, and a compressor.

Choosing an Actuator

Selecting the right linear actuator requires detailed consideration as there is no one-size-fits-all model and the type of actuator — linear pneumatic, electric rotary, rotary pneumatic, etc — depends on the industry and the application.

Inside an Actuator: Key Components Explained

An actuator converts energy into motion and controls that motion effectively. While various factors influence actuator performance, several key components are consistent across different types of actuators.

Key Components:

• Power Source: The energy source that powers the linear actuator can be electrical, pneumatic (air), hydraulic (water), or other types. Each source offers unique advantages depending on the application, and the choice of power source significantly affects the actuator's design and functionality.
• Power Converter: This component transfers energy from the power source to the actuator, adjusting the energy to align with the required output parameters. For instance, a hydraulic proportional valve regulates water flow to ensure consistency between input and desired motion output, while electrical inverters convert direct current (DC) to alternating current (AC) for electric actuators.
• Actuator: The physical-mechanical device that performs the energy conversion. The design varies based on the type and function of the actuator. For example, a door handle actuator may be a plastic box with plungers, whereas a hydraulic actuator consists of metal pistons. Its effectiveness lies in how well it transforms energy into mechanical motion tailored to specific needs.
• Mechanical Load: The physical stress or opposing force acting on the actuator system. This load requires the actuator to produce more power to overcome it. An everyday analogy is a car driving uphill, where the slope acts as a load that the engine must counteract to maintain speed.
• Controller: The device that activates the actuator and governs its output, including direction, force, and longevity. It prevents the system from operating autonomously and allows the operator to set limits on both ends of the conversion process. Controllers can be electric, electronic, or mechanical and may take various forms, such as buttons, levers, switches, or dials.

Main Types of Actuators

Actuator types vary according to the energy source, the type and speed of movement required, and its function. Actuator types do evolve and develop but it is helpful to understand the basics around some common actuators in use.

Electric Linear Actuator

Electric linear actuators use electrical energy to produce motion in a straight line using a piston that moves backwards and forwards triggered by electric signals. They produce pulling, pushing, ejection, or lifting movements. Their motors produce high-speed rotational motion with a gearbox that reduces speed or impact.

Electric Rotary Actuator

Electric rotary actuators use electrical energy to produce rotational movement, either for continuous motion or towards a fixed angle. They involve the combination of an electric motor, multistage gearbox, and limit switch. It creates rotation and torque when the current enters a magnetic field and from the force produced.

Hydraulic Linear Actuator

Hydraulic linear actuators use water pressure or other pressurized fluid to generate straight movements. They can produce torque strong enough to move external objects, hence their industrial applications. Hydraulic actuators consist of pistons that move in one direction and a spring that produces the reverse motion. There are also double-acting hydraulic actuators in which pressures comes at both ends to move the piston back and forth for more uniform motion.

Pneumatic Linear Actuator

Pneumatic linear actuators use compressed air to create motion by moving pistons back and forth or by pushing and pulling a carriage through a driveway or tube. Springs are used to bring the piston back. Alternatively, fluid is sometimes used at the opposite end to push it back. Pneumatic linear actuators can produce high speed and torque for short distances and are resistant to opposing pressure like wind or explosions.

Determining the Best Actuator for Your Needs

There are many types of actuators used across different fields, but not all will be suitable for your specific purposes. Here's a streamlined guide to help you choose the right one.

Key Considerations:

• Movement Type: Actuators provide either linear or rotary motion. Decide if you need precise linear movement or more dynamic, continuous rotary motion. Additionally, consider how far the movement needs to travel — whether short, sharp actions or longer strokes.
• Energy Input: Electrical actuators are commonly used and versatile, but may not always be practical. In cases where high voltage is undesirable, hydraulic or pneumatic actuators can provide reliable performance without the need for electrical input.
• Precision Needs: Some tasks require high precision, especially for delicate or intricate work like picking and handling. For heavy-duty tasks, precision may be less critical. Understanding how much accuracy you need will help narrow down your actuator options.
• Force Requirements: The load capacity of the actuator depends on the weight and size of the object it must move. Make sure to choose one that provides adequate force for your application.
• Stroke Length & Speed: Determine how far the actuator needs to move the object (stroke length) and at what speed. Keep in mind that actuators delivering higher force may move slower. Speed is typically measured in distance per second.
• Environment: Actuators used in industrial or rugged environments should be rated for protection, while those used indoors in labs or workshops may require less protection.
• Mounting Options: Actuators can be mounted in various ways depending on your needs. For example, a dual-pivot system allows swiveling, while a stationary system keeps the actuator in place.

With these considerations, you'll be able to narrow down your options.

Assessing Actuator Performance

Once you've selected an actuator, it's crucial to evaluate its performance using a few key metrics:

• Torque and Force: Torque refers to the twisting force that a linear actuator can produce, important in rotary actuators. Both static and dynamic loads should be considered — static load measures capacity when the actuator is at rest, while dynamic load measures capacity during movement.
• Load-Free Speed: Speed is important, especially when an actuator isn’t under load. Compare this "unloaded" speed to ensure it meets your performance requirements.
• Durability: Linear Actuator durability depends on type and design. Hydraulic actuators tend to be more durable for heavy-duty applications. A good actuator should have robust components that resist wear over time.
• Energy Efficiency: Efficient actuators use less energy to perform their tasks, which is important for sustainability and cost management. Opt for designs that minimize energy consumption while maintaining performance.

Connecting an Actuator

The types of actuators and the functions they relate to are broad. It follows, there is unlikely to be a blueprint or universal instruction manual when it comes to connecting actuators.

However, a common actuator, electric linear actuators, are relatively simple to connect and can be useful in varied household functions. Here is a rundown of connecting one to a device or a control mechanism like a rocker switch.

Connecting to a Device

Some electric linear actuators have four pins that are easily connected to your device. In this instance, the process is as easy as plugging in the linear actuator and walking away.

If your actuator does not come with the four pins included, you can buy a four-pin connector, available in six-foot and two-foot lengths.

Connect the connector to the actuator by finding the wires, which are hopefully exposed. You need to twist the wires to the connector before plugging it in. Use electrical tape to cover any exposed wires. If you can't find the wires or there is not enough, you can cut back the rubber for better give to connect to the connector.

The actuators may have different colored wires to the connector. If the actuator has red and black wires and the connector has brown and blue, for instance, connect red to brown and black to blue. If it has a red-blue combination, connect red to brown and blue to blue. If the actuator wires are red and yellow, connect red to brown wire and yellow to blue.

Connecting to a Rocker Switch

Rocker switches are the easiest way to control a linear electrical actuator either via a momentary rocker switch — those that move when the button is pressed — or a non-momentary switch, which can be switched between an "extend" movement, "retract" movement, or "off."

To connect a rocker switch, you will need a 12VDC battery or a 110VAC/220VAC to 12VDC power adapter in addition to your switch and linear actuator.

Connect the negative power to the third terminal of the rocker switch and use the second wire to connect terminals 3 and 4. The positive power of the power source connects to terminal 6 of the switch while the second wire connects terminal 6 to terminal 1. Connect the wires from terminals 2 and 5 to the actuator, which should now give you a working controller.

This is a simple, yet common example of connecting an electric linear actuator that has diverse uses. If you need help connecting your Actuator to your rocker switch and power supply, we have made a Wiring Diagram Generator for you.

Mounting an Actuator

Once you connect your actuator to the device or controller, you need to mount it, ready for use. There are two methods for this — dual pivoting and stationary mounting, as mentioned earlier.

Dual Pivot Mounting

Fixing a linear actuator on a platform that allows it to pivot involves using a mounting pin or clevis fixed to each bracket on each end of the actuator. A cross pin slides through the bracket and actuator to connect the two, we call these mounting brackets. The linear actuator can pivot around each pin, which means the actuator can shift alongside the object it is moving, allowing a little more dynamic function. A very common application of this type of mounting method is seen on doors allowing them to swing open and closed.

Stationary mounting

Stationary mounting involves fixing the actuator to a shaft mounting bracket and allows the actuator to create push or pull motions from a set position. This is how a button is mounted, for instance.

In both mounting methods, it is also important to make sure the mounting apparatus can handle the actuator's load as undue load could damage the actuator or cause it to veer off-kilter.

It is also important to consider the environment you are operating your actuator and any propensity to dust or water. Like any mechanical device, your actuator, mount, and ancillary components require maintenance. If you look after your actuator and take time to understand its capability and mechanisms, it could serve you for a long time.