EDIT: Running the same code through R2023a has solved the problem, but it did not work in R2022b.
I'm using Matlab to create a lead-lag controller with certain specifications (university course), and to find the compensator value, I wanted to use the margin() function to find and plot the gain and phase margins. However, Matlab calculates a phase margin of infinity, when I can see that the phase margin is approximately 18 in the plot itself. The plot also isn't showing the dotted lines anywhere on the phase subplot, which I haven't seen before.
Plot without the compensator, with a missing phase margin:
Similar plot with slightly different input transfer function:
Is there a reason that I'm not seeing the phase margin elements in the upper plot like I expected?
Input transfer function are below:
Cs = tf([alpha*Tz*K1,K1],[Tz,1]); % s-domain TF
Cz = c2d(Cs,T,'Tustin'); % z-domain TF using 'Tustin' method
Gs = tf(K,[Je,Be,0]);
Gz = c2d(Gs,T);
figure(8);
margin(Cz*Gz);
The constants used were generated in previous steps from Matlab:
alpha = 14.717, Tz = 6.901e-04, K1 = 1, K = 2.0329, Je = 7e-04, Be = 0.0061
