Re: transfer function in simulink: denominator > numerator

Hi Airo,

The reason simulink objects is because the transfer function

(0.54s^2+1.65s+1)/0.6s

is not causal. I would recommend adding a low pass filter to the transfer
fuction

(0.54s^2+1.65s+1)/0.6s * 1/(s/N+1)

and choose N to be a frequency large enough not affect any dynamics you are
interested or trying to affect.
This will give you a causal transfer function.

Here also a link on the drawbacks of using the derivative block in simulink
when implenting a pid structure.
http://www.mathworks.com/support/solutions/data/1-20NZJZ.html?solution=1-20NZJZ

-craig

"airol" <hairoljb@xxxxxxxxx> wrote in message
news:8886df28-2e5d-4636-8343-8e35306b1b7c@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
hi guys,

i try to model a circuit using transfer function. i've got problem
with order of denominator > numerator, simulink do not accept that.
i've search through this newsgroup and find 2 relevant threads, but
couldn't understand how to solve this specifically. can anybody give
me any idea to solve this. my trans. function is:

(0.54s^2+1.65s+1)/0.6s

thanks in advance.
airo,
liverpool


.

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