Actuators - What is an Actuator?

When Purchasing an Electric Linear Actuator, there are a few things you must consider. Firstly Linear Actuators have 4 main characteristics, each of which has different importance levels to any application.  These are Stroke - Force - Speed - IP Rating.  Typically you would choose the ideal Actuator based on the Stroke first, then force, then speed. Remember the Speed and Force trade-off against each other. So this means that you can have a high force, but then the speed will likely be lower. If you want High speed, then the force will likely be lower. 

When selecting the ideal electric linear actuator, several factors should be considered, including:

1. Load Capacity: The actuator should be capable of supporting the load that it will be moving. Consider the weight of the load and any other factors that may affect the actuator's ability to move it.
2. Speed: The speed of the actuator should match the speed required for the application. This will depend on the specific use case and may involve trade-offs between speed and other factors such as force and precision.
3. Stroke Length: The actuator should have a stroke length that is appropriate for the application. Consider the distance that the actuator needs to travel and any physical constraints that may limit the stroke length.
4. Force: The actuator should be able to generate enough force to move the load and overcome any friction or resistance in the system. This may involve calculating the required force based on the load and the desired acceleration or deceleration.
5. Precision: The actuator should be precise enough to meet the requirements of the application. This may involve considering factors such as accuracy, repeatability, and backlash.
6. Environmental Factors: The actuator should be able to operate in the intended environment, taking into account factors such as temperature, humidity, and exposure to dust or other contaminants.
7. Power Supply: The actuator should be compatible with the available power supply and voltage requirements of the application.
8. Noise: The actuator should operate at a noise level that is acceptable for the application.
9. Control Options: Consider the available control options, such as manual controls, programmable controllers, and sensors, and choose the one that best meets the needs of the application.

By carefully considering these factors, it is possible to select an electric linear actuator that will meet the specific requirements of the application, ensuring optimal performance and reliability.

The Stroke of an Actuator can also be called the extension. This is the distance of which the rod will move through and extend in and out. Usually, these are measured in Inches and can range from 1" (inch) stroke to around 40" Stroke. It's not normal to have Actuators with a stroke of longer than 40" to 50" due to the mechanical limitations of the leadscrew inside the Actuator that provides the pushing and pulling force.

The speed of the actuator is directly related to the gear ratio inside of it. A high gear ratio will slow down the speed of the rod that extends in and out of the actuator but also increases the force dramatically. Actuators range from forces as low as a few lbs to a few thousand pounds. Another way to get more speed and force is to make the motor larger. So if you have a large-diameter DC motor, it can spin faster and give more force. So, it's also notable that size also trades off with speed and force too, just to complicate things further.

Much like step 2, in this step, you have to think about what speed you can live with if you need a high force Actuator. The higher force will mean slower speed and vice versa. When considering the force requirements for selecting the ideal actuator, several factors should be taken into account, including:

1. Load Weight: The weight of the load that the actuator will be moving is a key factor in determining the force required. The actuator should be able to generate enough force to overcome the weight of the load, as well as any friction or resistance in the system.
2. Acceleration and Deceleration: The required force will also depend on the acceleration and deceleration rates needed for the application. If the load needs to be moved quickly, a higher force may be required to achieve the desired acceleration.
3. Distance and Speed: The force requirements will also be affected by the distance that the actuator needs to travel and the speed at which it needs to move. A longer stroke length or faster speed will require more force.
4. Inertia: The inertia of the load and the actuator itself can also affect the force requirements. If the load has high inertia, a higher force may be needed to get it moving, while a lower force may be sufficient to maintain its motion once it is moving.
5. Friction and Resistance: Friction and resistance in the system can increase the force requirements, as the actuator will need to generate enough force to overcome these factors in addition to moving the load.
6. Safety Factors: It is also important to consider any safety factors when determining the force requirements. A higher force may be necessary to ensure that the load is moved safely and securely, without any risk of damage or injury.

By taking these factors into account, it is possible to select an actuator with the appropriate force capabilities for the specific application, ensuring optimal performance and reliability.

The IP rating is the level of weather protection an Actuator has. A higher IP rating means the actuator can withstand more harsh environments such as rain and temperatures. A high IP rating of 66, is considered a very good outside type of weather application Actuator. However, for indoor use, an IP rating of 42 is adequate. When considering the IP (Ingress Protection) requirements for selecting the ideal actuator, several factors should be taken into account, including::

1. Environment: The environment in which the actuator will be used is a key factor in determining the required IP rating. Consider factors such as temperature, humidity, dust, and water exposure.
2. Location: The location of the actuator within the system can also affect the IP requirements. If the actuator is located in a high-risk area, such as near a water source or in an area with high levels of dust, a higher IP rating may be required.
3. Regulatory Requirements: Regulatory requirements may also dictate the minimum IP rating required for the application. Be sure to check any relevant regulations or standards to ensure compliance.
4. Expected Lifespan: The expected lifespan of the actuator can also be a factor in determining the required IP rating. If the actuator is expected to be in service for a long period of time, a higher IP rating may be necessary to ensure durability and longevity.
5. Maintenance Requirements: Consider the maintenance requirements for the actuator and how the IP rating may affect maintenance procedures. For example, a higher IP rating may make it more difficult to access and service components inside the actuator.

By considering these factors, it is possible to select an actuator with the appropriate IP rating for the specific application, ensuring that the actuator will operate reliably and safely in the intended environment.

So now you have the Actuator, but how do you mount it? All actuators come with what's called a Clevis on each and of the unit. This is where you connect the actuator to some type of bracket. For our Actuators, each actuator has a certain size of bracket that fits on both ends. Some actuators have special brackets to fit over the body of the actuator, but these can have restrictive movement effects on the actuator during motion. 

There are other factors that you need to think about when selecting the ideal Actuator. Voltage, for example, may be important. Typically Actuators come in 12 or 24vdc as standard. How about Feedback control? If you need positional control of the Actuator then you may need an Actuator that has some level of feedback like a hall sensor, optical sensor, or even a Potentiometer built into the actuator. These devices all provide a feedback signal so that a controller knows its position at any time. This is needed for applications where you need more than simple end-to-end control. We have written another blog post dedicated just to this topic of Feedback actuators here.

There are many ways to connect the Actuator, and this will depend on what type of control you have or need. A simple rocker switch control is by far the easiest way to connect one, but you may also want a remote control as another form of control. For positional control, you may need a more detailed connection. Typically most Electric actuators, offer a 2 wire configuration for connecting to power or a switch. +/- voltage are the wires leading from the actuator, and reversing those wires to the power source is what makes the actuator change direction. This process is called "reversing the polarity". A rocker switch does that for you inside the switch.

The most common type of Actuator is a 2 wire system. simply connecting these wires directly to a power supply (usually 12vdc) will make the actuator move, and reversing the wires will make the actuator move in the opposite direction. A rocker switch is what does this for you, so connect the 2 wires from the actuator to the switch and connect the 2 wires from the power source to the switch and you are done. Our switches all have the wiring diagrams on each product page to make this simple

Other Types

Pneumatic

These types of actuators use pressurized gas or air in a cylinder created by a high-pressure pump to move a piston to create linear motion. Like hydraulic actuators, the design of a pneumatic linear actuator has been around for a long time. An air compressor is used to pressurize the air or inert gas in a tank, and  high-pressure air is used to make the actuator's piston slide in and out. Once the piston in the actuator has reached the end of the travel, a valve switch is then moved to open the valve to the other end of the actuator where again high-pressure air then pushes the piston in the actuator in the other direction. 

The benefits of using pneumatics are:

1. High speed is possible and is controlled by the pressure valve and volumetric capacity of the system.
2. Fairly high forces can be achieved.
3. Little sound is emitted apart from the pump pressurizing the tank.
4. Very long strokes are possible.
5. Extremely high cycle reliability and durability.
6. The Actuators can be very small and compact since they are quite simple in construction. 

Drawbacks of pneumatic are:

1. Additional equipment is required such as a tank and high-pressure pump.
2. The entire system can not be allowed to leak if the system fails.
3. Air is a compressible gas, meaning when a pneumatic actuator is moving a high force, there is always a lag because the gas/air will naturally compress first before it moves the piston inside the actuator. This means there will be a lag in the system. Hydraulic Actuators do not have this problem.
4. Very low positional control is achievable. Watch the video below where we use Lego to demonstrate the lack of control compared to a mechanical Actuator, and use a DTI (Dial Test Indicator) to show the difference

Where are they used?

They are used where high-speed motion is required, upwards of 30 inches per second. Once installed they are hard to move from one place to another as they require a lot of installation time. These Actuators are found on the assembly lines of manufacturing factories as they are ideal for performing millions of cycles with no maintenance, and they can move very quickly. 

Hydraulic

Hydraulic Actuators operate exactly the same way as Pneumatic actuators, except instead of using high-pressure air or gas they use a non-compressible liquid called hydraulic fluid. Because the fluid is non-compressible it has a huge advantage over pneumatics, these systems are capable of immense forces. This is why you see them used exclusively on heavy-duty construction equipment like diggers, dump trucks, forklift trucks, tractors, etc.

How do they work?

Hydraulic Actuators use high-pressure fluid to push a piston backward and forward where the switching is done through valve switches. These systems require high-pressure pumps, high-pressure valves and piping, and a tank to hold hydraulic fluid in. So, if you have a lot of space and money and require a very high amount of force, hydraulics could be the way to go.

The benefits of using hydraulic actuators are:

1. Moderate speed is possible and is controlled by the pump speed.
2. Extremely high forces can be achieved. 
3. Very long strokes are possible.
4. Extremely high cycle reliability and durability.
5. The Actuators can be very small and compact in size since they are quite simple in construction. 

The Drawbacks are:

1. Control. Hydraulic Actuators have very little precision control.
2. Hydraulic fluid is required for the system to work, and the fluid is very toxic. If the system fails, it could leak.
3. When the hydraulic pump is operating it can be very noisy, and the higher the required force, the louder the noise.
4. Hydraulic fluid relies on predictable viscosity, so it does not flow smoothly through pipes and valves, etc. This requires additional energy to push fluid at high pressure through pipes and fittings. As a result, hydraulic systems are very inefficient to operate and use, especially in varying climates.
5. Price. These systems are expensive to buy and install. 

Rotary

Another type of actuator is a rotary actuator, which functions primarily by utilizing an electric power supply with limited rotational movement or continuous rotational movement, depending on the application's needs. One major advantage of rotary Actuators is that they run at lower speeds but produces higher torque values effectively making them ideal for use in robotics and other industrial Automation applications, as well as consumer-grade electronics demanding high-torque systems for consistent operation cycles. The rotary motor generates this torque while gearing downs speeding up the driveshaft rotation thus creating smooth circular motions without interruptions whatsoever. For optimum performance consistency during operation, the actuator uses a sensor to detect its position measurements typically in the form of a hall sensor or encoder, thus sending back signals to the brain for readability. Moreover, for space concerns, these efficient actuators come with a remarkable feature-user-friendly small-size capability; hence allowing them to be used even in confined spaces areas.

The principle:

The motion produced by these types of actuators may be either continuous rotation, as seen in an electric motor, or movement could be a fixed angular rotation. With a rotary actuator that's pneumatically or hydraulically controlled they are more likely to be a fixed angular rotation type, this is because the rack or piston that rotates the main shaft can only move so far and so the rotational movement is restricted by the linear stroke available. If more rotation is required, the piston would need to slide further, and a different gear ratio is used to translate the motion. 

Rotary Servo

There exists another category of rotary actuator, namely the servo motor and stepper motor. These actuators are controlled via electricity. Thereby providing a continuous rotational motion while simultaneously offering noteworthy precision in terms of rotational control.

These types of actuators are commonly used in Robotics and consumer electronics where rotational movement and torque are produced by a rotary motor. The speed is reduced and torque increased by a gear system to create the rotary motion. To get precise control, the actuator will have a sensor that measures position. This is usually in the form of a hall sensor or encoder that sends a signal back to the 'brain' to translate into a position. A great feature of servo motors is that they can be made very small and used in very tight places. 

Summary

Actuators come in many different types, from rotary to linear, hydraulic and pneumatic, solenoid, and electro-mechanical. Each type has an ideal application. Large industrial rotary actuators that are hydraulically driven are great for opening huge oil-pipe valves, and micro-actuators can be powered by small 12v power sources with great accuracy and precision for robotics and small applications. For more details on Actuators, we have written a white paper that goes into a little more depth in the world of actuators. Please read that article here. 

FIRGELLI®  actuators are specially designed and produced with high-quality materials to give you the perfect balance of power, control, and price to build your automation systems.