Machine-translated by Google. Questions are authored in English.
Top

Discussion

The transfer function \(\left(\frac{C(s)}{R(s)}\right)\) of the system shown in figure below is :

Block diagram: R(s) passes through G1 to a summing point, then through G2 to a second summing point whose output is C(s); R(s) is also fed directly to each summing point, all signs plus

  • A.\(1 + G_{2} + G_{1}G_{2}\)
  • B.\(1 + G_{1} + G_{2} + G_{1}G_{2}\)
  • C.\(\frac{1 + G_{1}G_{2}}{1 + G_{1} + G_{2} + G_{1}G_{2}}\)
  • D.\(\frac{(1 + G_{1}) \cdot G_{2}}{1 + G_{2} + G_{1}G_{2}}\)

Answer: A

The transfer function is \(1 + G_{2} + G_{1}G_{2}\).

Follow the signal forward. The first summing point adds R(s) to the output of \(G_{1}\), so its output is \(R(1 + G_{1})\). This passes through \(G_{2}\), and the second summing point adds R(s) once more:

\[ \begin{aligned} C &= G_{2}R(1 + G_{1}) + R \\ &= R(1 + G_{2} + G_{1}G_{2}) \end{aligned} \]

There is no feedback loop, only feedforward paths, so the result has no denominator, which rules out the two fractional options. \(1 + G_{1} + G_{2} + G_{1}G_{2}\) would need a direct path through \(G_{1}\) alone to the output, which the diagram does not have.

No comment is present. Be the first to comment.
Loading…

Post your comment

Please log in or register to post a comment.