From Bode Plot to Root Locus
From Bode Plot to Root Locus
(OP)
I have software that generates the bode plot of a system. How can I get the poles and zeros of this system using the bode plot?
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RE: From Bode Plot to Root Locus
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm
RE: From Bode Plot to Root Locus
Peter Nachtwey
Delta Computer Systems
http://www.deltamotion.com
http://forum.deltamotion.com/
IFPE Hall of Fame Member
RE: From Bode Plot to Root Locus
RE: From Bode Plot to Root Locus
Peter Nachtwey
Delta Computer Systems
http://www.deltamotion.com
http://forum.deltamotion.com/
IFPE Hall of Fame Member
RE: From Bode Plot to Root Locus
A.
RE: From Bode Plot to Root Locus
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm
RE: From Bode Plot to Root Locus
But what data do you measure? You don't measure a Bode plot directly. We can and have done it to evaluate valves and perform system identification.
I bet your college professor never did it for a system in the wild.
We can do it but it is hard to do right. I have examples of using swept sine waves and other wave forms. Swept sine waves are difficult because in our case we run out of oil pretty quickly. We usually help test valves. We sell motion controllers, we are not a testing lab but we do help others.
1. get the data. It will be either position or velocity data as a function of time. A Bode plot
2. fit a transfer function to it. I use differential equations because they can handle non-linear systems.
3. If the differential equation for the transfer function is linear it is easy to find the eigenvalues ( poles ). Most systems don't have zeros.
4. if the system is non-linear the poles will move as function of amplitude. It is probably easiest just to compare amplitudes and phase between the input and the output but at least one has data instead of trying to read points off a plot with little resolution.
The motion controller can generate swept sine waves or any other pattern. In this case we were testing a Parker non-linear valve. The problem is that we run out of oil when doing swept sine waves so we can't test to high frequencies. The first .svg ( scalable vector graphics ) file shows how our system identification can find the transfer function for a non linear valve. The model matches the data very well.
https://deltamotion.com/peter/svg/Valve3Act&Es...
This plot shows the non-linearity of the gain, flow, as a function of the valve opening and what the motion controller must do to compensate.
https://deltamotion.com/peter/svg/Valve3Vel%20vs%2...
I use .svg files because .svg files are easier for the magazine editors to work with and they work well with browsers.
Peter Nachtwey
Delta Computer Systems
http://www.deltamotion.com
http://forum.deltamotion.com/
IFPE Hall of Fame Member
RE: From Bode Plot to Root Locus
He supposedly did; he consulted with quite a few companies in his day.
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm
RE: From Bode Plot to Root Locus
sky,
your question requires supporting data, as it make no sense by it self.