Simulink Control Design™ - MathWorks

Current plot held

The Simulink response exhibits small residual oscillations. The notch filter discretization

is the likely culprit because the notch frequency is close to the Nyquist frequency pi/

0.002=1570 rad/s. By default the notch is discretized using the ZOH method. Compare

this with the Tustin method prewarped at the notch frequency:

wn = damp(N); % natural frequency of the notch filter

Ts = 0.002; % sample time of discrete notch filter

Nd1 = c2d(N,Ts,'zoh');

Nd2 = c2d(N,Ts,'tustin',c2dOptions('PrewarpFrequency',wn(1)));

clf, bode(N,Nd1,Nd2)

12 Loop-Shaping Design