Types of Feedback Controls

Types of Feedback Controls

There are two types of Feedback Controls are as follows :- 
1) Open Loop Control System ,and 
2) Close Loop Control System

Open Loop Control System :

Here Output has no effect on the controller action, because no such feedback path is provided. The output only depends on the Reference Input (R).

Following figure represents a Open Loop Control System -:

Close Loop Control System :

Here, Output depends on both the Input Reference Signal and the feedback path of Input Signal. It is one of the type Feedback System.

Following figure depicts the Close loop control system :-

Difference Between Open and Close Loop Control System -:

OPEN LOOP -

1) In Open Loop Control System Output has no effect on Control Action.

2) Due to the absence of feedback path, no comparison is done between Input and the previous Output Signal.

3) Open Loops are Stable and less accurate system.

4) Operation of Open Loop system affected due to the presence of the non - linearities in its Elements.


CLOSE LOOP -

1) In Close Loop Control System Output depends on both the Input and the previous Output Signal.

2) Error Function is the difference between the Input and previous Output Signal.

3) Close Loop can become unstable under some conditions (feedback) and the system is highly accurate.

4) Close Loop system adjusts the effect of non - linearities in the Elements.