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Mathematcial Model & Parameter Identification

 
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stefanengelke



Joined: 03 Jan 2006
Posts: 59
Location: Stuttgart, Germany

PostPosted: Mon Jul 31, 2006 9:38 pm    Post subject: Mathematcial Model & Parameter Identification Reply with quote

Hi all,

I have finished the documentation of the mathematical model I'm working with:
http://www.openservo.com/moin.cgi/MathModel
The model is pretty much the same Zed is explaining in his document. I have also implemented it in Matlab, but I'm trying to port it to Octave now. My objective is to write some scripts for an easy identification of the model parameters.

If we have a identified model, my next objective will be the implementation of a new control strategy. My plan is as follows:

- Using an exact input-output linearization to compensate the friction
- Introducing the external torque caused by a load as a new state in the state-space-model
- Using a state estimator (=observer) to reconstruct servo velocity and external torque
- Using a state regulator (=state space controler) as control-loop

Yes I know, this is a comprehensive plan and will take some time to be implemented, but this strategy seems very promising for me.

Stefan
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ginge
Site Admin


Joined: 14 Jan 2006
Posts: 1029
Location: Manchester, UK

PostPosted: Tue Aug 01, 2006 12:03 am    Post subject: Reply with quote

Hey stefan, good to see you back!

The wiki entry is amazing. Very concise!

Thanks for this information, it will help me model my robot arm with some more accuracy.

Barry
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mpthompson



Joined: 02 Jan 2006
Posts: 650
Location: San Carlos, CA

PostPosted: Tue Aug 01, 2006 2:44 am    Post subject: Reply with quote

Hi Stefan, I also welcome you back. It's been a little quiet around here lately, but hopefully we'll get things going again.

-Mike
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stefanengelke



Joined: 03 Jan 2006
Posts: 59
Location: Stuttgart, Germany

PostPosted: Fri Sep 29, 2006 10:33 am    Post subject: Reply with quote

I've fixed a small mistake in the mathematical model. The friction moment depends on the sum of all other moments and not only on the motor torque.
Code:
F_friction = f(omega, M)

where omega is the angular velocity of the servo and M is the sum of moments. In our case M is the difference between the motor torque and the external load.
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