MATLAB: How to set to display “Minimum Stability Margins” by default on the Nyquist frequency response in Control System Toolbox 8.0 (R2007a)

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I would like to set to display "Minimum Stability Margins" by default on the Nyquist frequency response.

Best Answer

You cannot set "Minimum Stability Margins" by default on Nyquist plots in Control System Toolbox 8.0 (R2007a) and there are no workarounds.

However, you can observe the "Minimum Stability Margins" after you plot the Nyquist diagram. To do so,

1. Right click in the display area of the Nyquist figure window.

2. Select the "Characteristics" tab.

3. Check the "Minimum Stability Margins" option.

Related Solutions

MATLAB: How does MARGIN from Control System Toolbox 8.4 (R2009b) choose which Gain margin to display

MARGIN function calls ALLMARGINS function to calculate the gain (and phase) margin of the system. When ALLMARGIN returns multiple gain margins MARGIN chooses the smallest gain by taking the smallest gain in dB, not taking the sign into account.

For the example 0.2 (-14 dB) and 2.4 (7.6 dB) that gives the latter is returned as gain margin of the system.

MATLAB: Is the gain margin returned by the MARGIN function in the Control Systems Toolbox different than the gain margin shown in the associated bode plot

This enhancement has been incorporated in Release 2006a (R2006a). For previous product releases, read below for any possible workarounds:

To convert the gain margin Gm to have units in dB, use the following code:

Gm_dB = 20*log10(Gm)

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Related Solutions

MATLAB: How does MARGIN from Control System Toolbox 8.4 (R2009b) choose which Gain margin to display

MATLAB: Is the gain margin returned by the MARGIN function in the Control Systems Toolbox different than the gain margin shown in the associated bode plot

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