Getting the transfer function from the transient response
Getting the transfer function from the transient response
(OP)
Hello,
Is there a method to get the transfer function from its transient response. I have been researching for some time now and the only thing that I have found is this:
Control Theory
On page 41, the author states that it is possible using "Guillemin's technique" and referred me back to a book by Truxal but I am unable to find any information about the book or the method. does anyone have any references that I could possibly read?
Is there a method to get the transfer function from its transient response. I have been researching for some time now and the only thing that I have found is this:
Control Theory
On page 41, the author states that it is possible using "Guillemin's technique" and referred me back to a book by Truxal but I am unable to find any information about the book or the method. does anyone have any references that I could possibly read?





RE: Getting the transfer function from the transient response
TTFN
I can do absolutely anything. I'm an expert!
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers
RE: Getting the transfer function from the transient response
For starters look up "least squares fit"
Least squares is easy to implement but it only yields a transfer function in the z-domain
That is not the way to do it. With the least squares fit the driving function or control can be anything.
Good places to start.
http://www.mathworks.com/help/ident/ref/arx.html?r...
http://home.hit.no/~hansha/documents/control/theor...
The are more advanced ways of doing this. When serious then use system of differential equations and BFGS. Then it is possible to model non-linear systems.
I use system identification for auto tuning motion systems.
Here is an example of auto tuning a small motor.
I was really testing the Screenflow program that I used to record this video.
http://deltamotion.com/peter/Videos/AutoTuneTest2....
Auto tuning this motor is simple because it is just a gain and a time constant.
The gain and time constant was only briefly shown because I was really testing the screen capture software.
Hydraulic systems are much more difficult.
Peter Nachtwey
Delta Computer Systems
http://www.deltamotion.com
RE: Getting the transfer function from the transient response
http://deltamotion.com/peter/Mathcad/Mathcad%20-%2...
Column 0 is the time. Column 2 is the measured position in inches. Column 5 is the control voltage.
The I use the Minerr function to find the parameters of second order underdamped system with some dead time.
Then I use my model to plot estimated positions, velocities and acceleration and compare them to the measured.
On the bottom of page 2/4 I compare the measured velocity and the estimated velocity. One can see the effects of quantizing on the feed back positions. The estimated value from the model is much more realistic. The control signal is not an impulse but ramps. I use ramps that are just fast enough to excite any high frequency systems but not too fast to cause damage in a real application.
When auto tuning a hydraulic system with a 90 ton coil of steel on it generating an impulse is the fastest way to cause a big bang and get kicked out.
Peter Nachtwey
Delta Computer Systems
http://www.deltamotion.com
RE: Getting the transfer function from the transient response
Thanks for your replies. I have checked the documents, they have been really helpful. But the problem is that I only have the transient response "curve". Nothing else, while the second document that PNachtwey has attached assumes either I have a set of equations or a black-box system. Is there a way to extract the data from the curve alone to get a transfer function representation?
RE: Getting the transfer function from the transient response
TTFN
I can do absolutely anything. I'm an expert!
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers
RE: Getting the transfer function from the transient response
Peter Nachtwey
Delta Computer Systems
http://www.deltamotion.com