Question:

Feedback control systems are:

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Feedback Sensitivity. Negative feedback significantly reduces the sensitivity of the overall system performance to variations in the forward path gain (G). However, the system remains sensitive (sensitivity approaches -1) to variations in the feedback path gain (H).
Updated On: May 7, 2025
  • Insensitive to both forward and feedback path parameter changes
  • Less sensitive to feedback path parameter changes than to forward path parameter changes
  • Less sensitive to forward path parameter changes that to feedback path parameter changes
  • Equally sensitive to forward feedback path parameter changes % Typo: "forward and feedback"
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The Correct Option is C

Solution and Explanation

One of the primary advantages of using negative feedback in control systems is the reduction of sensitivity to variations in the parameters of the forward path (e
g
, the plant or amplifier gain)
The closed-loop gain or transfer function \( T(s) = \frac{G(s)}{1 + G(s)H(s)} \), where G(s) is the forward path transfer function and H(s) is the feedback path transfer function
The sensitivity of the closed-loop transfer function T to changes in G (\( S^T_G \)) is approximately \( \frac{1}{1 + G(s)H(s)} \)
If the loop gain \(G(s)H(s)\) is large, this sensitivity is significantly reduced
The sensitivity of T to changes in H (\( S^T_H \)) is approximately \( \frac{-G(s)H(s)}{1 + G(s)H(s)} \), which approaches -1 for large loop gain
This means the closed-loop system's performance is much less sensitive to variations in the forward path elements (G) compared to variations in the feedback path elements (H)
Changes in the feedback path have a more direct and pronounced effect on the overall performance
Therefore, feedback control systems are less sensitive to forward path parameter changes than to feedback path parameter changes
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