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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.

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

Disadvantages:
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).

Advantages:

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

Disadvantages:
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

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

Disadvantages:
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.

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

Disadvantages:
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.

                        Advantages:
         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

                        Disadvantages:
         1. Limited position control
         2. Relatively larger size

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

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

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

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