---

---

Open Loop Control System

• Open Loop Control Systems are systems in which the control action is independent of the output. In open loop system the output remains constant for constant input provided disturbances are unchanged.

• In any open-loop system the output is not compared with the input and hence the output cannot be regulated.

• If exposed to external factors that affect the output an open loop system won’t produce the desired output. 

Closed Loop Control System

Closed loop control Systems are systems in which the control action is dependent on the realtime output. In closed loop control system the realtime error signal ( difference between the input signal and the output signal ) is fed back to the controller so as to reduce the error and get the desired output response.

Comparison

 

Open Loop	Closed Loop
Any change in output has no effect on the input i.e. feedback does not  exists.	Changes in output, affects the input which is possible by use of feedback.
Feedback element is absent.	Feedback element is present.
It is inaccurate and unreliable.	Highly accurate and reliable.
Highly sensitive to the disturbances.	Less sensitive to the disturbances.
Bandwidth is small.	Bandwidth is large.
Simple to construct and cheap.	Complicated to design and hence costly.
Generally are stable in nature.	Stability    is    the    major consideration    while designing
Highly affected by nonlinearities.	Reduced effect of nonlinearities.

 

---

---