How to set the phase offset when using Margin Command

Hello,

I try to use the marging command, but the resulting curves has alwyas an offset.

I don't know how to make it start at "0".

When using the two command Bode, and bodeplot i can get the desired result.

Can any one help please ?

Thank you and have a nice day.

EL Mehdi

Answer 1

[Star Strider]

They appear to me to actually be the same. The difference is that margin appears to use the unwrap function, and bodeplot does not. The reason for that choice reflects what each function does.

[El Mehdi HARRAS]

First thank you form your reponse.

From mathematcical and physical point of view, yes it's exactly the same thing. I agree with you.

My problem here is, a would like to use the margin function and to get the same response as the bode or bodeplot function from graphical point of view (Which is figure 2).

Like you know, the margin functon calculate the phase & gain margin and to show them in the graphics. The bode or bodeplot do not have this fnctionality, i think (perhaps i am mistaking)

[Star Strider]

My pleasure!

The two functions simply present the same information in a slightly different graphical format. The margin function depicts the phase as it does because of the intended purpose of the function.

[El Mehdi HARRAS]

Another question please.

Does the margin function has a fonctionnality like PhaseWrapping & PhaseWrappingBranch ?

[Star Strider]

The margin function does not appear to have any options. If you want amplitude and phase information, you would have to use bodeplot with the appropriate outputs.

I have never used those (I usually just use the defaults), so I had to look it up in bodeoptions. I would assume it uses the unwrap function, although I have never specified that when I have used bodeplot. The PhaseWrappingBranch option simply defines the angle where it wraps the accumulated phase.

[El Mehdi HARRAS]

Ok, Thank you so much.

[Star Strider]

As always, my pleasure!