Sunday, 5 March 2017
Types of Actuators used for Motion in Automation with Advantages Disadvantages
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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