Negative feedback is a regulatory mechanism in which a 'stimulus' causes an opposite 'output' in order to maintain an ideal level of whatever is being regulated. Steps of Negative Feedback Loops All negative feedback loops occur in a series of steps. Let's continue to use a thermostat as an example.
In feedforward control the systems output can change without any reaction from the controller while in feedback control any change in the system output will provoke a reaction of the controller. Since the important aspect is the systems output and the feedforward controller does not react to changes in the output it can be considered a non-reactive control method.
Positive feedback, or affirming comments about past behavior. These are things that went well and need to be repeated. Negative feedforward, or corrective comments about future behavior. These are things that don’t need to be repeated next time.