Z transfer fcn under simulink and cmd line
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I create a simple cmd from S to Z domain as below, and the result is matched with my understanding;
clear
rth1=0.0268;
tau1=1066.6;
Ts=0.05;
tf1=tf(rth1,[tau1 1])
dtf1=c2d(tf1,Ts)
figure;
step(tf1);
figure
step(dtf1);
but when i create this under simulink, the result is not matched, as you can see the Z transfer fcn output is quite different with the S transfer fcn.
Is there anyone can help me?
Accepted Answer
Jon
on 5 Apr 2023
This appears to be due to a round off error in the denominator of the discrete transfer function input to Simulink.
Try for example with the denominator set to
[1 -0.999949]
instead of
[1 -1]
and you will see that the step response of the continuous and discrete approximation are now much closer
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