Feedback in Control Systems

In daily life we use this word feedback when we want any review or opinion or any suggestions about us or our work. So basically feedback is returning the output (with some function on it) back to the input. This feedback is the core component in any Control System.

We know that if we have a system which gets some input, process on it according to its transfer function and then give output. Now if this output has no implications on input or we say input is not governed by the nature of the output then the system would not be giving actual desired result as it is needed.

Types of Feedback in Control

There are two types of feedback used in control systems.

1. Positive Feedback
2. Negative Feedback

Both Feedbacks have their own importance in typical applications.

1. Positive Feedback

      The positive feedback means adding the output back into the input. It is shown below

Positive Feedback with unity gain

This is a very simple feedback system in which the feedback has unity gain i.e the output is directly fed back to the input and is added. The positive feedback has limited applications as it adds to the input and causes the response of the system to increase.

1. Negative Feedback

 This is the most widely used type of the feedback. In negative feedback the output is fed back and is subtracted from to input to generate a compare signal (also called error signal or actuating signal) which drives the system and make it possible the desired output should be obtained. It is shown below.

Negative Feedback with unity gain

How Negative Feedback Works

The negative feedback is actually the comparison of the input and the generated output. We can represent it more intuitively as below.

Referenced Feedback

  Now this block diagram correctly represents how a negative feedback works. The reference signal is applied to the system which is actually the desired response which we require. The output then obtained is compared back with this reference signal. If the output differs from the reference then an actuating/error signal is generated which drives the system until the output becomes equal to the input and hence the process continues and controlled output is obtained.

The feedbacks are worth important in every control system because if we don't know what we are getting we cannot appropriately apply input.

This is the basic introduction of the feedbacks.

Thanks

Waiting for your Feedbacks