# Curve Fitting to high order exponential function

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ANIL ALAN 2015 年 12 月 30 日
コメント済み: ANIL ALAN 2016 年 1 月 5 日
Hello everybody, this is my first question here.
What I was trying to do is to fit an exponential function to a data. I already tried Matlab's Curve Fitting Tool, however it only fits exponential functions up to 2nd order. My data is more complex than that unfortunately, therefore 2nd order fit doesn't give me good result. Do you know any other tools or methods that I can use in Matlab to make the exponential fitting higher than 2nd order ?
Anil
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John D'Errico 2015 年 12 月 30 日
I wish I could up-vote a comment. I would do so for dpb's comment were that possible.
ANIL ALAN 2016 年 1 月 4 日
Hello dpb
Thanks for the comment. Let me go a little deeper into the problem. I am going to design a controller for a physical system. Before going into to design phase, I would like to create a nice model. A part of this system is a BLDC (as actuator). I would like to create motors model by its response to a step input. I am using its own driver card and I see that when I first introduce the step position change command, driver pass the command through some kind of filter to smoothen harsh change. Eventually, I would like to model this pre-filter hoping to fit output to a linear system. Its output looks alike a linear filter of high order with most of the states zero. I attached the output data to comment.

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### 採用された回答

Rakesh Chavan 2016 年 1 月 5 日
Hi Alan,
Have you tried using the System Identification APP in MATLAB. It the App can be used for identifying linear models given data which I think you want to achieve. Documentation for the app can be found at the following link:
There are other functions like 'iddata' and 'ssest' where given data and order we can obtain a state space model for the plant. Kindly refer to the following link:
Hope this helps.
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ANIL ALAN 2016 年 1 月 5 日
Thank you, that is the answer I am looking for.

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