Nyquist Plot for 2 Real Poles and 2 Real Poles 1 Real Zero

Cuthbert Nyack

Applet shows the Nyquist plot and step response for 2 real(red,orange), 2 real poles and 1 real zero(green,pink) system. Since all systems are type 0, then plots start on the +ve real axis.
Second order starts in the first and ends in the second quadrant(phase from 0 to -180°) eg (2.0, 1.0, 1.0, 4.0, 1.0, 0.61). Both systems are always stable.
eg parameters (10.0, 1.0, 1.0, 40.0, 1.0, 3.0) show Nyquist plot and step response being little affected by a zero which is far to the left of the origin in the s plane.
(10.0, 1.0, 1.0, 6.8, 1.0, 3.01) show Nyquist plot for the 2 pole system having a phase margin of ~37° at w = 3.01 and the 2p1z system having a phase margin of 60° at w = 3.16.
(10.0, 1.0, 1.0, 2.1, 1.0, 4.93) show the step response of the 2p1z system when the phase margin is 90°.

Gif image below shows how applet should appear.

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