Question about cascaded transfer functions

Discussion in 'Homework Help' started by Amanda_Riley, Apr 2, 2011.

  1. Amanda_Riley

    Thread Starter New Member

    May 12, 2010
    22
    0
    I have two 1st order transfer functions of:

    5/s+5 and 10/s+10

    when they are cascaded you get 50/(s+5)(s+10) if an impulse function of 1 is input.

    How is the output 10e^-5t - 10e^-10t?
     
  2. Georacer

    Moderator

    Nov 25, 2009
    5,142
    1,266
    By cascaded you mean connected in series? If yes, then the Transfer Function that occurs is independent of the input of the system.

    I really messed up this one. The correct answer is given by the method explained by the post next to mine.
     
    Last edited: Apr 2, 2011
  3. dewasiuk

    New Member

    Feb 14, 2011
    24
    0
    If you use partial fraction expansion, you can easily take the inverse laplace transform to transform your terms to the time domain.

    50/(s+5)(s+10) = a/(s+5) + b/(s+5)

    Solve for both a and b, and then you can then easily apply laplace techniques, if you've already learned them.

    My solution: http://img864.imageshack.us/i/laplace.jpg/

    Table of transforms: http://www.intmath.com/Laplace-transformation/Table-laplace-transforms.php
     
    Last edited: Apr 2, 2011
  4. Amanda_Riley

    Thread Starter New Member

    May 12, 2010
    22
    0
    Thank you for this x
     
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