Feedback Control 


This concept justifies the use of the word negative in three ways:
• The negative aspect of feeding the measured signal backwards
from the output to the input of the system. (Actual definition of
negative feedback control).
• The control correction must be negative in that a correction
rather than a compounding of error must occur.
• The fact that an error must occur before a correction can take
place, i.e., retrospective or negative control action.
In the next section we will study in more detail the methods used to
effect the necessary control corrections.