MATLAB: Difference in simulation results of continuous and discrete transfer function in simulink

c2ddiscreteMATLABsimulink

Hi,
I am trying to compare the continuous (s-domain) and discrete (z-domain) implementation of a system in simulink. My model is simple as shown.
My input signal is a sine of amplitude = '1' and frequency = '2*pi*1e3' rad/sec. The discrete domain TF is obtained by using 'c2d' function of Matlab with a sampling time of '1e-5' seconds. But I am getting entirely different responses to the same. It would be of great help if someone can clarify why this is happening.
   Many thanks in advance
      Karthik R

Best Answer

Check the poles of your discrete model, they are unstable while your continuous model is stable. That means the discretization was unsuccessful. I think it's due to numeric calculation error. The denominator of your continuous model, maybe is the cause. D=[1 a b] with b very big then 1 and a. Try to make a discretization manually.
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