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Summation of Bode Plots

Posted 10 years ago
POSTED BY: DJ Swack
5 Replies
Posted 10 years ago

missed the "s" sorry.

POSTED BY: DJ Swack
Posted 10 years ago

I have mathematica 8 and it doesn't seem to recognize the SystemModelSeriesConnect function. Am I missing something obvious?

POSTED BY: DJ Swack
Posted 10 years ago

That sounds right to me. I just did not know the syntax for doing what I wanted to do. Appreciate the help!!!!

POSTED BY: DJ Swack
Posted 10 years ago

Hi DJ,

It depends on what you mean by sum. On a Bode plot gains are in dB, so summing is equivalent to multiplication of gains, which is a series connection for transfer functions. (Or multiplication in the s-domain.) Such multiplication also sums phase response. Below tf1 has DC gain 1 and a single pole at -10; tf2 has gain 2 and a pole at -1000; tfSum is the series connection.

tf1 = TransferFunctionModel[{{{{}}}, {{{-10}}}, {{1 10}}}, s]

tf2 = TransferFunctionModel[{{{{}}}, {{{-1000}}}, {{2 1000}}}, s]

tfSum = SystemsModelSeriesConnect[tf1, tf2]

BodePlot[{tf1, tf2, tfSum}, PlotLegends -> {"TF1", "TF2", "Sum"}]

enter image description here

POSTED BY: David Keith
Posted 10 years ago

I'll have a think about this one and get back to you later.

POSTED BY: Norman Dewane
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