why draw the plot this way?


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
Reply to
workaholic
Loading thread data ...
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?
Reply to
Tim Wescott
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.
Reply to
workaholic
is
(1-jwT)=3D> fourth quadrant =3D> 270 270-90
Reply to
cpbas
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
Reply to
workaholic

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.