Shape a transferfunction to measurement data in Control System Designer

Hello everyone, For a self study assignment I have to create the transfer function of measurementdata to later shape a controller around. The data of the measurement is already analysed and I'm able to make bode plots out of it. The problem is that I can't find a way of fitting a magnitude plot with a known transfer function to the one of the measurements. I first tried using the MATLAB function 'tfest' but this didn't give coherent results (looks more like: as long as a lot of points are on the line, it must be correct).

I then tried to use the 'Control System Designer' app in MATLAB. This works great but comparing the output to the measurement plot is something I have to do by hand as of now. Does anyone know if it is possible to get the magnitude plot from the measurements into this app or is there a way to quickly get a visual feedback on whether or not both plots align?

Thanks in advance!

Answer 1

[Sebastian K]

Hi Joris,

Unless I am missing something, it sounds like what you are trying to do is a perfect example to use the System Identification App.

This is a graphical user interface that will let you:

• Import measured data
• Fit a model (transfer function, state space, etc.) to your data
• Tune the parameters of your fit
• Plot the response of your fitted model against your measured data

The link I copied above from our documentation contains many examples, including how to fit transfer functions and state-space models for linear systems.

I hope this helps.

Sebastian

[Joris]

That looks very promising! Thanks a lot