consider a system in its Fourier transform form:

1+j

***w***T/ (1+j

***w***T1) and its nonminimum phase counterpart: 1-j

***w***T/

(1+j

***w***T1) where 0

- posted
13 years ago

consider a system in its Fourier transform form:

1+j

(1+j

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- posted
13 years ago

There's a bug in Matlab's Bode plotter?

Have you tried doing it manually? I.e. get the frequency response into a vector, then plot the vector's amplitude and phase vs. frequency?

Have you tried doing it manually? I.e. get the frequency response into a vector, then plot the vector's amplitude and phase vs. frequency?

- posted
13 years ago

Although I haven't done it manually, I have a chart on the Modern
Control Engineering, 3rd Edition, Ogata. The illustration on it is
just what I stated in my last post. the nonminimum phase counterpart's
phase may also begin in approximately 0 deg and end at -180 deg. I do
not know why Matlab begin with 180.

- posted
13 years ago

is
(1-jwT)=3D> fourth quadrant =3D> 270 270-90

- posted
13 years ago

e is
> > > > the same in the bode plot, while the first system's phase curve is
> > > > within 0 =C2=A0to =C2=A0-90. Due to nonmininmum phase characteristi= cs of the
> > > > nonminimum phase sytem, the phase curve is 0 to -180. =C2=A0However= the
> > > > Matlab always draw the nonminimum phase sytem's phase curve within = 180
> > > > to 0. Why? we all know that nonmininmum phase system contains a lar= ge
> > > > scale of the phase lag, why does Matlab use this kind of fashion? >
> > > There's a bug in Matlab's Bode plotter?
>
> > > Have you tried doing it manually? =C2=A0I.e. get the frequency respon= se into a
> > > vector, then plot the vector's amplitude and phase vs. frequency? >
> > > --www.wescottdesign.com
>
> > Although I haven't done it manually, I have a chart on the Modern
> > Control Engineering, 3rd Edition, Ogata. The illustration on it is
> > just what I stated in my last post. the nonminimum phase counterpart's
> > phase may also begin in approximately 0 deg and end at -180 deg. I do
> > not know why Matlab begin with 180.
>
> (1-jwT)=3D> =C2=A0 =C2=A0fourth quadrant =3D> 270 0T=3D>
> (1-jwT)/(1+jwT1)=3D> 270-90

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