Friday, March 9, 2012

Open loop and closed loop system


Open loop control system

Advantage
  • Sensors are not needed to measure variable as feedback is absent.
  • It is easier to build and less expensive.
  • It is more stable as feedback is absent.
Disadvantage

  • It has no accuracy.
  • If non-linearity is present in the input then it cannot be reduced because of absent of feedback.
  • More sensitive to system parameter variation.
  • Transient response and steady state response cannot be controlled effectively.
Example:
  • An automatic faster
  • Control of furnace for coal heating
  • An electric washing machine
 Closed loop control system






   Advantage
  • It gives more accuracy.
  • If non-linearity is present in the input then it is reduced by the feedback.
  • It is less sensitive to system parameter variation.
  • Transient response and steady state response can be controlled more conveniently.
    Disadvantage
  • Sensors are needed as feedback is present.
  • It is very difficult to build.
  • It is comparatively less stable. 
     Example:
  • Pressure control system
  • Speed Control System
  • Robot Control System

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