I am trying to understand the technical meaning of the term 'feed-forward', when and where it can be used and where it cannot be used? I have seen this term in various different areas.
For example:
Vector Field oriented of AC Motors
Convolutional Neural Networks
Digital Filter Design
It looks like that this is a fundamental term. But I could not find its fundamental technical definition.
What phenomenon is encapsulated in this term. And if a certain phenomenon is labeled as 'feed-forward' then what are the attributes and properties that are understood that will be possessed by that phenomenon?
Best Answer
Feed forward refers to the direction of the signal flow. For feed forward, the direction is, well, forward :-)
I think it is easier to show an example. I know that many "sigma-delta" ADCs (analog to digital converters) use a combination of feedback and feed forward.
I found an example of a block diagram of such an ADC here in this article, about Higher-order incremental delta-sigma analog-to-digital converters.
The general direction of the signal flow is from left to right. The input of the ADC is at the left, the output at the right.
Note how there is a feedback line at the bottom of the diagram, from the output of the Quantizer back via b to a summation point near the input.
Note that by changing the value of b this can be either positive feedback or negative feedback. But it is feedback as the signal "goes back" (in the direction of the input).
Then there are the three signals at the top of the diagram which feed a signal from left to right so in the "forward" direction. These are the "feed forward" paths. Again, depending on the coefficients a1 and a2 these signals can give either positive feed forward or negative feed forward. But both are feed forward as the direction is towards the output.