Bode Plot Display All Stability Margins

Hi,

Is there a way to programmitically set "All Stability Margins" for a Bode plot from matlab script or command window? I don't want to have to set it everytime in the plot characteristics window.

-Andy

[Adam Danz]

https://www.mathworks.com/matlabcentral/answers/136462-how-can-you-turn-on-all-stability-margins-when-using-the-bode-function-via-script

[Andrew Hunter]

The margin function does not show all stability margins, it will only show the minimum. The question you forwarded me to has a misleading title.

[Adam Danz]

I have 0 experience with bode plots or these setting but after some tinkering, I hope this can get you started.

% Produce bodd plot
sys = rss(5);
h = bodeplot(sys);
p = get(h);
% Settings
p.CharacteristicManager(1).CharacteristicLabel = 'All Stability Margins';
p.CharacteristicManager(2).CharacteristicLabel = 'All Stability Margins';
p.CharacteristicManager(3).CharacteristicLabel = 'All Stability Margins';

[Andrew Hunter]

Ahh this is exactly what i was looking for! Thank you! This function characteristicmanager doesnt seem to be available anywhere on the matlab web documentation. Do you know where i can find a comprehensive documentation of the matlab “language” and built in functions?

[Adam Danz]

Glad I could help (and learn a little, myself!). I added an answer below that contains several links to documentation. There's relatively little information available on some of these properties so I wouldn't spend more than 10 minutes searching the internet before rolling up your sleeves and just trying stuff. Feel free to share what you've learned - I'd be interested in hearing what worked for you.

Answer 1

[Adam Danz]

Documentation on bode plots is a bit sparse but here's some ways to modify the plots programmatically.

Use getoptions() / setoption()

The handle output to h=bodeplot(sys) can be used to customize the plot by using the p=getoptions(h) to get the plot options handle and then setoptions(h,p) to apply the changed settings to the plot. See the setoptions link for an example.

Use the plot handle directly

The handle output to h=bodeplot(sys) can also be used to retreive and edit plot properties by using p=get(h). Here's a demo

% Produce bode plot
sys = rss(5);
h = bodeplot(sys);
p = get(h);
% Settings
p.CharacteristicManager(1).CharacteristicLabel = 'All Stability Margins';

Use bodeoptions()

Unlike the other use options above, this option allows you to specify bode plot properties before the plot is created rather than customizing the plot post hoc. opts=bodeoptions returns the default plot options for bode plots which can be customized and then applied to the bodeplot using bodeplot(..., opts). Alternatively, opts=bodeoptions('cstprefs') initializes the plot options according to the options you selected in the Control System and System Identification Toolbox Preferences Editor.

[Andrew Hunter]

I dont think this has the answer but your other comment does! Replace this answer with that one.

[Adam Danz]

The 2nd method "use the plot handle directly" is the approach in my previous comment. But I added the demo from my comment to make it more useful. The other two methods are to provide a more general summary of how to make changes to bode plots programmatically. Thanks for the suggestion.

Answer 2

[A Jenkins]

Adam Danz's method got me started, but didn't quite get me there, and I ended up using this one: (2019a)

sys = rss(5);
h = bodeplot(sys);
h.showCharacteristic('AllStabilityMargins')

Answer 3

[Erick Oberstar]

As of Matlab 2020b I can verify this works for both nyqistplot and bodeplot functions

Ts= 0.01
n = [0 0.3680 0.2640];
d = [1.0 -1.368 0.3680];
Gz = tf(n,d,Ts)
Gz.Variable = 'z^-1'
figure; h1=nyquistplot(Gz) 
axis([-1.5 1.5 -1.5 1.5]); grid on;
h1.showCharacteristic('AllStabilityMargins');
%zoomcp(h1);% Optional zoom in on critical point 
figure; h2 = bodeplot(Gz)
h2.showCharacteristic('AllStabilityMargins');

Note this doesn't work if you generate the plots via "bode" or "nyquist"