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Symbolic jacobian of an arm

asked 2016-06-05 05:52:15 -0500

gabri89 gravatar image

Hi all,

I've a 7 DOF arm described in .xacro format and I would like to extrapolate its jacobian in symbolic form (not numerical angle values in the matrix ).

I tried to use KDL for this scope, and I was able to obtain the jacobian of this arm but in a numerical form. That is, during a gazebo simulation, I could read the values of each angles, insert them in the jacobian matrix with a specific kdl command, and obtain the jacobian matrix on every gazebo step time.

That's ok, but if I have another target in which I need the symbolic for of this jacobian from which extrapolate other matrix (inertial, coriolis ecc..), I'm not able to do this. (For example if I want to control my arm in a particular way in which I need the dynamic expression of the system).

Has anyone every have this problem? Is there a method with kdl or another software that I can use?

Thank you!

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Hi Did you resolved your problem? I have almost the same problem as you I want to use Coriolis vector in my controller, do you have any suggestion for me? I have read many things in last days and I just got confused. I have tried to use DART library but till now it was not helpful, I really appreciate if you can help me. Thanks.

abbas gravatar imageabbas ( 2016-07-31 05:18:54 -0500 )edit

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answered 2016-06-08 07:07:10 -0500

mrslvgg gravatar image

If you need the symbolic Jacobian of your robot you should calculate it in symbolic form using Matlab for example. It allows symbolic calculation as exemplified in this page. Moreover, the Matlab Robotic Toolbox has a C code generator useful to directly output the calculated symbolic quantities in C format.

On the other hand, KDL library allows you to numerically compute the matrices of the robot dynamic model (e.g. Inertia, Coriolis, Gravity) starting from robot state (joint positions, velocities). You can find the detailed implementation here.

Hope this can help.

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Is it possible to use KDL library in each step in gazebo for example in designing controller?

abbas gravatar imageabbas ( 2016-07-31 04:58:07 -0500 )edit

Yes, you can write a plugin that uses KDL.

nkoenig gravatar imagenkoenig ( 2016-08-01 10:17:31 -0500 )edit

I would be happy to contribute to the writing of the KDL plugin

mrslvgg gravatar imagemrslvgg ( 2016-08-14 07:09:52 -0500 )edit

MarioSelvaggio, I really appreciate your intention, may I have your email, this is mine:

abbas gravatar imageabbas ( 2016-08-24 10:38:48 -0500 )edit

Sure. My email address is:

mrslvgg gravatar imagemrslvgg ( 2016-08-26 00:03:10 -0500 )edit

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Asked: 2016-06-05 05:52:15 -0500

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Last updated: Jun 08 '16