Connection With Classical Feedback Theory
Classical feedback theory neglects feedforward (G0). If feedforward is dropped, the gain from the asymptotic gain model becomes
while in classical feedback theory, in terms of the open loop gain A, the gain with feedback (closed loop gain) is:
Comparison of the two expressions indicates the feedback factor βFB is:
while the open-loop gain is:
If the accuracy is adequate (usually it is), these formulas suggest an alternative evaluation of T: evaluate the open-loop gain and G∞ and use these expressions to find T. Often these two evaluations are easier than evaluation of T directly.
Read more about this topic: Asymptotic Gain Model
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