Remove small numbers from transfer function

Question

Jason Gauthier 2020-4-9

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/516746-remove-small-numbers-from-transfer-function

评论： Ameer Hamza 2020-4-10

采纳的回答： Ameer Hamza

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Greetings,

Is there a simple way to remove small numbes from a transfer function?

           -0.8921
  -------------------------
  s^2 + 1.035 s - 1.533e-14 
 

The last term is so incredible small, it's pointless. I have a very set of TFs (12 outputs and 4 inputs.) I'd just like to sweep through and easily clean them up.

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Answer 1

Ameer Hamza 2020-4-10

3
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/516746-remove-small-numbers-from-transfer-function#answer_425159

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try this

sys(1) = tf(1, [1 2 1.2e-12]);
sys(2) = tf(1, [2 3 1.5e-11]);
sys(3) = tf(1, [3 4 5.5e-13]);
sys(4) = tf(1, [4 5 2.7e-12]);
[n,d] = tfdata(sys);
n = cellfun(@(x) {x.*(x>1e-7)}, n);
d = cellfun(@(x) {x.*(x>1e-7)}, d);
sys = tf(n, d);

It filters all coefficient with magnitude less than

.

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Jason Gauthier 2020-4-10

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Thank you! I had to use

n = cellfun(@(x) {x.*(abs(x)>1e-7)}, n);
d = cellfun(@(x) {x.*(abs(x)>1e-7)}, d);

Since some of the coefficients were negative, but this worked great!

Ameer Hamza 2020-4-10

Glad to be of help. On a side note, negative coefficients in a transfer function indicate instability. But if these values are just noise, then it should be fine to ignore it.

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