Not all actuators are the same. Naturally, different industries and applications have different motion control needs and therefore require different types of linear actuators.
Each unique system of motion control harnesses the power from different types of energy to create force. Within each system, there are also different ways to create this force, including, but not limited to: screw, chain, hoist roller, vacuum, thermal, magnetic and ultrasonic. Each variation brings along its own unique advantages and disadvantages. Most manufacturers use their own proprietary versions of these types of linear actuators.
Here we will briefly explain the basic differences of each main system.
Common Types of Linear Actuators:
- Hydraulic
- Pneumatic
- Piezoelectric
- Mechanical
- Electric
Hydraulic
Hydraulic actuators use pressurized liquid to create force. They can be quite precise and powerful, generating a lot of force, however they are often limited by speed.
Advantages
- Extremely Powerful
- Precise
- Easy to transport (compared to pneumatic)
Disadvantages
- Expensive
- Limited speed
- Complicated system
- Prone to leakage
- Expensive for maintenance
Industry examples include: hydraulic car jacks, forklifts and other construction vehicles with lifting/moving capabilities.
Pneumatic
Pneumatic actuators use pressurized gas to create forced motion (similar to hydraulic but using gas instead of liquid). They typically cannot handle very heavy loads, however they are useful for lighter weight applications because the input power source is compressed air and they are generally cheaper than hydraulic. The downside is that they are often large, bulky, complicated and loud.
Advantages
- Strong
- Fast
- Can be relatively inexpensive (compared to hydraulic)
- Can use force powered by external air and compressor
Disadvantages
- Large
- Bulky
- Noisy
- Difficult to achieve precise positioning
- Difficult to transport
Industry examples include: automobile combustible engines, compressed air pumps, nail guns and mail tubes
Piezoelectric
Piezoelectric actuators convert electrical energy into mechanical motion. They can be extremely precise, stable, can be scaled to very small sizes and used in extreme cold temperatures.
The drawbacks of these types of linear actuators are that they typically require high voltages, require special protection and usually only offer limited stroke capabilities. Another problem is they are prone to hysteresis, which causes its reactions to change over time.
Advantages
- Do not need lubrication
- Can work in extreme cold temperatures
- Extremely accurate
- Scalable for very small or large applications
Disadvantages
- Brittle / need special protection
- Require high voltages
- Can be expensive
- Short stroke range
- Prone to hysteresis
Industry examples include: applications in cryogenics and aerospace industries.
Mechanical
Mechanical actuators are the most basic of actuators, generally taking rotary motion and converting it into linear motion. The power to lift, push or pull is commonly done using a crank, knob, winch, wheel or handle – done either by human or machine.
Mechanical actuators are often used for very heavy-duty, industrial applications, since they are usually the strongest and most reliable.
Advantages
- Can handle very heavy loads
- Can be scaled for very large applications
- Simple system
- Easy to maintain
- Reliable
- Flexible capabilities
- Wide range of options
Disadvantages
- Usually human or mechanically controlled (no automation)
- Not as precise as other systems
- Some options only provide pull capabilities
- Some options only provide push capabilities
Industry examples include: simple car jack
Electric
Electric linear actuators are similar to mechanical ones, except instead of using a crank, knob, winch, wheel or handle, they draw power from an electrical motor.
They are perhaps the most common type of linear actuator due to their ease of use and maintain, cost effectiveness, accuracy and broad configuration capabilities.
The disadvantage is that the heavier the object being moved is, the slower an electric linear actuator will be able to move it and the more current will be drawn to do so. Also, there is risk that the actuator shaft can move downwards with gravity (aka, backdrive) if the load is too heavy for it to hold up once the power has stopped.
Electric and mechanical types of linear actuators both take the energy of rotary power and convert that force to make it move in a straight line.
Advantages
- Inexpensive
- Powerful
- Efficient
- Reliable
- Simple system
- Easy to maintain
- Repeatable precision
- Can be automated
- Can be scaled for large or small applications
- Work well in wide range of temperatures
- Requires little voltage
- Low friction (ball nut)
- Flexible capabilities
- Wide range of options
Disadvantages
- Needs lubrication
- Needs protection from debris
- Can backdrive
- Compromise speed with force
- Moving parts prone to wear
Industry examples include: automobile power steering, aircraft, robotics, DIY, home automation, RC vehicles
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