Simulink Control Design™ - MathWorks

Step 2: Describing Function Analysis of Saturation Nonlinearity

The saturation nonlinearity has the following sinusoidal input describing function:

where for a saturation with upper and lower limits of 0.5 and -0.5, respectively

where A is the amplitude of the sinusoidal input signal.

Compute and plot the describing function, N_A(A), vs. amplitude, A, for amplitudes

varying between 0.1 and 2.1:

A = linspace(0.1,2.1,21);

N_A = saturationDF(0.5./A);

plot(A, N_A);

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

5 Frequency Response Estimation