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The characteristic equation of a closed-loop system is given by
s4 + 6s3 + 11s2 + 6s + K = 0
Stable closed loop behaviour can be ensured when gain K is such that
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- 0 < K < 10
- K > 10
- – ∞ < K < ∞
- 0 < K < 20
Correct Option: A
s4 + 6s3 + 11s2 + 6s + K = 0
| s4 | 1 | 11 | K |
| s3 | 6 | 6 | – |
| s2 | 10 | K | – |
| s1 | 6 – 0.6 K | – | – |
| s0 | K | – | – |
For stability
K ≥ 0 and also 6 (1 – 0.1 K) ≥ 0
Thus, 0 ≤ K ≤ 10.
