Closed loop system | Definition | Advantages | Disadvantages

Here we learn about Closed loop system, Definition, Advantages and disadvantages of closed loop system, Examples of closed Loop system.

Closed Loop System

Definition of closed Loop system :

~ A system in which the controlling action is some how dependent on the output is called as closed loop system.

~ Such system uses a feedback that is part of the output is feedback to the input and it is compared with the reference input.

~ Feedback is the property of the control system which allows the output to be compared with the reference input so that appropriate controlling action can be executed.
~ It is then compared with the reference input giving error signal e= R ± b. When feedback signal sign is positive, system is called as, positive feedback system (e = R+ b) and when feedback sign is negative system is called as negative feedback system (e= R-b).
~ This error is then manipulated by the controller generating manipulated actuating signal for the process to be controlled. This manipulation is such that to make error in the system exactly zero. The process then gives the controlled output C (t).

Fig. of closed Loop system

Advantages of closed Loop system :

(1) It reduces effects of process (plant) disturbances.
(2) It makes system insensitive to process variations.
(3) It stabilizes an unstable system.
(4) It creates well-defined relations between output and reference.
(5) It is more accurate than open loop systems.
(6) It performs job faster than human beings
(7) It clear out the errors between input and output signals.

Disadvantages of closed Loop system :

(1) These are relatively more complex in construction.
2) These are costlier than open loop system.
3) These are less stable than open loop system.

Examples of closed Loop system :

~ An example 0f closed-loop control system is a person steering an automobile by looking at the auto's location on the road and making the appropriate adjustments.
~ Car washing by a responsible human being is an example of closed-loop control system.
~ A refrigerator is a closed-loop $ystem. Its temperature is measured by a thermostat which turns the motor ON when the temperature rises above the desired value and turns the motor OFF when the temperature again reaches the desired value.