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The open-loop transfer function of a unity negative feed back control system is given by
G(s) = K(s + 2) (s + 1)(s - 7)
the stability of the open-loop and closed-loop configuration of the system are respectively—
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- stable and stable
- unstable and stable
- stable and unstable
- unstable and unstable
- stable and stable
Correct Option: B
Since there is a pole in right half plane. Hence the open loop system is unstable.
For unity feedback closed-loop system, the C.E. is
K (s + 2) + (s + 1) (s – 7) = 0
or s2 + s (K – 6) + (2K – 7) = 0
s2 1 2K-7
s1 K-6 0
s0 2K-7
K – 6 > 0 for stable system, since for value K > 6 all the elements in the first column of R.H. array are positive.
