Simulink Control Design™ - MathWorks

N_A_withfrest(ct) = real(sysest.resp);

end

plot(A,N_A,A,N_A_withfrest,'r*')

xlabel('Amplitude');ylabel('N_A(A)');title('Describing function for saturation');

close_system(mdl);

Step 3: Closed-Loop Describing Function Analysis

You can also run a closed-loop describing function analysis over a frequency range. You

can begin by analytically computing the frequency response from reference to output

using describing functions. To do this, first compute the amplitude of the input signal

"nonlinear_input" for the nonlinearity, given the reference amplitude and frequency. Note

that the input amplitude for the nonlinearity is not necessarily equal to reference

amplitude.

5 Frequency Response Estimation