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I am having issues trying to get the root locus plot for the following complex transfer function (H):

% Ax = b Form
A =    1.0e+06 *[0.0713 - 0.0073i,...
                 -1.8793 - 0.0357i];
b = -32.4298;

%TF
G = A\b;

%PI controller gain
Kp = 100; %proportional gain      
Ki = 1; %integral gain
K = pid(Kp,Ki);  %PI controller

%Open Loop TF
H = G*K;

rlocus(G)

The error I get is the following: "Cannot compute the root locus of models with complex data."

Can I just drop the imaginary parts of the TF (shown below) to do the root locus?

   (0.001725-3.277e-05i) s + (1.725e-05-3.277e-07i)
 ------------------------------------------------
                          s
Jesus
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  • Transfer function having complex polynomial coefficients? How are you getting them? – Sardar Usama Aug 27 '18 at 18:17
  • @SardarUsama, Based on "Ax = b" My A matrix is a 1x2 with complex data and b matrix is a 2x1 with real data. So when I calculate my TF (b/A) I get complex coefficients. I am using a PI controller and multiplying it by my TF to get the system's open loop TF. – Jesus Aug 27 '18 at 18:22
  • Are you sure that all the calculations that lead to the above transfer function are correct? – Sardar Usama Aug 27 '18 at 18:26
  • Can you post the matrix A and b and the PI controller? – Andrea Bellizzi Aug 27 '18 at 19:13
  • @SardarUsama, I cheked multimple times and it seems to be correct. I edited the above question to include more details. Thanks – Jesus Aug 27 '18 at 19:46
  • @AndreaBellizzi, Yes, I edited the above question. Thanks. – Jesus Aug 27 '18 at 19:46
  • @Jesus I've some doubt, the matrix A isn't square, have you model the system well? maybe you have missed some information. Also, what are the C matrix and D matrix? – Andrea Bellizzi Aug 28 '18 at 06:31

0 Answers0