[ODE] How to obtain the torque of a joint

mango juice mangoj at hotmail.com
Thu Nov 30 09:27:56 MST 2006

Dear Ignacio,

Thank you very much for your reply.

I have checked the manual already but I got
incorrect results. I guess I do not understanding
how to use the functions properly? Please refer
to my previous posting titled
"How to measure the joint torque correctly".

To obtain the total force applied to a joint which
rotates about the x-axis, which way is correct:

dJointFeedback* feedback = dJointGetFeedback(joint);
1. feedback->f1[0]
2. feedback->f1[0] - feedbackf2[0]
3. sqrt(feedback->f1[0]^2 + feedback->f1[1]^2 + feedback->f1[2]^2)
4. open to suggestions

By the way, what does the dJointSetFeedback function has
to do with getting the force/torque information? Am I supposed
to call it before dJointGetFeedback? I don't quite understand
what the description in Sect 7.2 means. Maybe that is
the problem. Could you please give me an example?

Thank you very much in advance.


>From: Ignacio García Fernández <ignacio.garcia at uv.es>
>To: ode at q12.org
>Subject: Re: [ODE] How to obtain the torque of a joint
>Date: Thu, 30 Nov 2006 09:47:34 +0100
>Both for force and torque, you should look at Section 7.2 of the ODE
>manual, where it explains the functions
>void dJointSetFeedback (dJointID, dJointFeedback *);
>dJointFeedback *dJointGetFeedback (dJointID);
>and the structure dJointFeedback.
>El mié, 29-11-2006 a las 19:46 +0000, mango juice escribió:
> > Hello!
> >
> > I am having difficulty in obtaining the torque of a
> > joint correctly. Could anybody please give me an
> > example on how to do it?
> >
> > Thank you very much in advance.
> >
> >
> > ______________________________________________________________________
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>May the source be with you
>Ignacio García Fernández                  Instituto de Robótica
>ignacio.garcia_at_uv.es                 Universidad de Valencia
>http://robotica.uv.es/~ignacio/                Tlf. 96 354 3671

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