Question about cascaded transfer functions

Thread Starter

Amanda_Riley

Joined May 12, 2010
22
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?
 

Georacer

Joined Nov 25, 2009
5,182
By cascaded you mean connected in series? If yes, then the Transfer Function that occurs is independent of the input of the system.

Georacer said:
Is your question about the amplitude of the response? In that case, yes I think it should be:
Y=50e^-5t - 50e^-10t
I really messed up this one. The correct answer is given by the method explained by the post next to mine.
 
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dewasiuk

Joined Feb 14, 2011
24
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?
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
 
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