Feedback

This is a control term.

In any control system you have an 'input', 'process' and 'output'

But there is fourth item that may - or may not - be present. This item is called 'feedback'.

Feedback is a method of letting the input know what the output is doing. This means feedback can affect the way the control system works.

Feedback is often a good idea as it makes the system more accurate and responsive. The disadvantage is that it makes the design more complicated - it must be done right or the whole thing becomes unstable.

 

An 'unstable' system is where the output is swinging wildly from one value to another. For example if you place a microphone too close to the speakers of a music system, you will hear a horrible screeching noise - this is an 'unstable system' where there is too much positive feedback.

A control system is said to be 'closed loop' if it includes feedback

A control system is said to be 'open loop' of it does not contain feedback.

2020-10