Hi Jesus,
As per my understanding, you would like to find the Nyquist plot of the Transfer function
G1(s) = 4/((s^0.7)*(s+1)^2).
You might have tried using the 'nyquist' function to get the Nyquist plot but encountered some errors on your end. It looks like the transfer function '1/s^0.7' is not directly compatible with the 'nyquist' function in MATLAB because the exponent of 0.7 is not a valid transfer function power.
I suggest you take a numerical approach to approximate the 'nyquist' plot for the transfer function by defining a frequency range for evaluation.
Here is an example showing how you can do it:
close all;
% Frequency Range for evaluation
w = logspace(-3,3,1000);
% Complex Frequency
s = 1i*w;
% Transfer Function
G = 4./((s.^0.7).*(s+1).^2);
% Plotting the Nyquist plot numerically
figure;
plot(real(G) , imag(G));
xlim([-1 0]);
ylim([-0.15 0.1]);
title('Approximated Nyquist Plot');
xlabel('Real Axis');
ylabel('Imaginary Axis');
grid on
Please refer to the following documentation links to know more about
- 'Plot' function: https://www.mathworks.com/help/matlab/ref/plot.html
- 'Nyquist' function: https://www.mathworks.com/help/control/ref/dynamicsystem.nyquist.html
