Bode plot and Step Response for 2 Real Poles and 2RP1RZ

Cuthbert Nyack

This applet shows the Bode plot of a 2 pole and 2 pole, 1 zero system:-
For the 2 pole case the the phase goes from 0 to -p and the magnitude plot has slope 0 at low frequencies and -40dB/decade at high frequencies.
The effect of the zero can be illustrated by the eg parameters (10.0, 1.0, 1.0, 20.0, 1.0, 2.0). This shows a break in the magnitude plot and a phase advance of 45° at 20rad/s.
To have an effect on the step response the zero has to be moved to lower frequencies eg (10.0, 1.0, 1.0, 1.6, 0.5, 2.0). In this case the phase margin is ~90° for the pole zero case and ~45° for the 1 pole case.

Gif image below shows how applet should appear.

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