Types of Actuators used for Motion in Automation with Advantages & Disadvantages

The actuators used for performing motion (which includes control of speed, positional accuracy or torque) are

• Air Motors

• AC Induction Motors

• Clutch/Brake

• Stepper Motors

• Hydraulic Motors

• Servomotors

 1) Air Motors
This uses “compressed air” to create motion. Pressure and flow determine speed and torque. Positional accuracy is not a required.

1. Low cost
2. Available components
3. Maintenance easy
4. Simple
5 .Centralized power source

1. Audible compressor noise
2. Difficult to regulate speed
3 Prone to contamination
4. Energy inefficient

 2) Hydraulic motors
This uses “pressurized oil” to move a piston. Higher pressure results in higher torque (i.e. brute force).


1 .Easy to apply
2. High torques
3. Centralized power source
4. Simple

1. Audible noise
2. Difficult to control speed
3. Slow positioning
4. Prone to leaks
5. Energy inefficient
6. High maintenance required

 3) Clutch/Brake

A device couples a continuously rotating shaft and a load. Uncoupling the load results in stopping of shaft. Varying on/off time results in varying distances

1. Easy to apply
2. Low cost
3. Good for start/stop (not used with high loads)
4. Easy to provide speed matching

1. Uncontrolled acceleration
2. Inaccurate
3. Prone to wear
4. Non-repeatable performance

4) Stepping Motors

Electromechanical device which converts one digital pulse into a specific rotational movement/Step or displacement. A "train of pulses" results in rotational speed.

1. Simple control
2. Moderate cost
3. Good for constant loads
4. Good positional accuracy

1. Prone to losing steps
2. Not good for varying loads
3. Energy inefficient
4. Large motor size
5. Resonance problems

 5) AC Induction Motors –
Widely used for constant speed requirements. Electric "starters" provide connections/start-up/overload protection. Newer technology provides variable speed Drive capability.

         1. Simple motor
         2. Low cost
         3. Mature technology
         4. Straightforward on/off control
         5. Affordable coarse speed control
         6 .Simple wiring
         7. Wide product variety
         8. Many vendors available

         1. Limited position control
         2. Relatively larger size

 6) Servomotors
A motor with a "feedback" device called as encoder. High speed and position accuracy

1. High performance
2. Small size
3. Wide variety of components
4. High speeds available with specialized controls

1. High cost
2. High performance limited by controls
3. High speed, torque is limited.

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