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