What are Actuators, its principle and applications

• Agent

• Agent Requirements

• Introduction to Actuators

• Actuator Components

• Actuator Types

• Actuator Applications

• Conclusion
• Links & References

An Agent

• Perceives environment
• Think for the results through their intelligence
• Perform actions as a result

Types

• Human
• Robot
• Software

Intelligent Agent

Agent Environment

Before we design an intelligent agent, we must specify its “task environment”:

• Performance measure
• Environment
• Actuators
• Sensors

• Electromechanical 
  • 1. Electromagnetic
    2. Electrodynamics
• Fluid mechanical 
  • 1. Pneumatic
    2. Hydraulic 
• Thermal

Electric Actuators

It uses ELECTRICAL energy for the activation function It may result in

• 1. Rotation 
  2. Linear movement
  3. linear movement with gear or with real linear motor

Main Features

• Easy to control
• From mW to MW

Main Features

• Normally high velocities 1000 – 10000 rpm
• Several types
• Accurate servo control
• Ideal torque for driving
• Excellent efficiency
• Autonomous power system difficult

Principal of Operation

An electric current in a presence of magnetic field produces a force    F= I L X B    . . . (1)

• to produce a more uniform to torque, in pratical motor we should have more loops.
• Electromagnets produce magnetic field and are called field coils 

Types of Motors

AC Motors
DC Motors

• Modified from Basic AC DC Motors
  1. Torque Motors
  2. Servomotors
  3. Stepper Motors
  4. Brushless Motors
  5. Linear Motors

Hydraulic Actuators

• It uses HYDRAULIC head (of water) for the actuation function
• Main Components
  1. Motor & pump actuator combination 
  2. Motor, generator, battery
  3. Motor & gear combination
• Main Features
  1. Linear movement
  2. Larger forces without gears

Main Features

• 1. Actuators are simple
  2. In mobile machines
  3. Bad efficiency
  4. Many times larger load can be manipulated

Medium used

• 1. Oil
  2. oil/water mix (non flammable)

• water + corrosion inhibitors
  – virtually incompressible
  – viscosity heavily temperature dependent

Pressure Range

• Up to about 30 MPa – 200 MPa for diesel injectors

Applications

• Positioning with high load rigidity precision in closed loop control systems

Hydraulic Systems

Pneumatic Actuators

•              Main Features                                               

1.            Quick response
2.            Large forces with elasticity
3.            No leak problems

•             Medium used 

1.          Usually air 

1.          Up to about 1 MPa

•      Applications
•        Lower power and force / torque requirements,
•        Positioning by mechanical stops in open loop systems.

Thermal Actuators

• Working Principal

1. Thermal Expansion

• In bimetallic strip
• In thermoloid material

          Operation

•         When current is applied

•         Thermoloid material, sealed in the actuator, changes phase from a solid to a     liquid and expands

•        The volume of the Thermoloid material the material is essentially incompressible and encased in a rigid housing

•          The piston moves and extends

•          Motion occurs over a narrow temperature range

1.              Merits

•  precise control of a device at a specific temperature
• operating temperature is extremely stable
• repeatable and accurate

1.          Applications

• Temperature actuated valves
• Switches & Latches
• Clamps and control devices
•  Instrument calibration

Piezoelectric Actuators