Previous UpNext

5  Other responses

5.1  Nyquist plot

Nyquist plot of the open loop plant G(s) can be seen by clicking on ``Response-->Nyquist''. The gain and phase margin is displayed on the plot. If you find that your plot is too coarse or cluttered, you can change the minimum and maximum frequency in ``Settings-->Nyquist-Nichols plot''. The units for frequency can be changed in "Settings->Frequency units".

5.2  Nichols plot

Nichols plot for G(s) is obtained by selecting ``Response-->Nichols''. If the grid (in the main menu) is set to ``on'' you will see the logarithmic grid superimposed on the Nichols plot. Here too, you can select the desired frequency units  in "Settings->Frequency units". 

5.3  Popov plot

The Popov plot can be used to predict the stability of the closed loop system with a sector bound nonlinearity in loop. We plot real part of G(iw) on the real axis and w Imaginary   G(iw) on the imaginary axis. A simple construction then gives the range of the ``Popov sector'' and the ``multiplier''. Please see any standard text on nonlinear systems for more details on the Popov plot.


PreviousUpNext