Question

A unity feedback control system has a forward path transfer function equal to

\(\frac{{42.25}}{{s\left( {s + 6.5} \right)}}\)

The unit step response of this system starting from rest, will have its maximum value at a time equal to

1. 0 sec.
2. 0.56 sec.
3. 5.6 sec.
4. infinity

Answer 1

Correct Answer - Option 4 : infinity

\(\begin{array}{l} \frac{{42.25}}{{s\left( {s + 6.5} \right)}} = \frac{1}{{s + 6.5}} + \frac{{6.5}}{{{s^2}}} - \frac{1}{s}\\ c\left( t \right) = {e^{ - 6.5t}} + 6.5u\left( t \right) - u\left( t \right) \end{array}\)

At t → ∞, c (t) → ∞.