Re: [ros-users] cartesian trajectories

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Author: User discussions
Date:  
To: User discussions, ros-sig-robot-control
Subject: Re: [ros-users] cartesian trajectories
Putting the ros robot control sig back in the loop, as it got out of the
recipients list in the second thread message (missing messages here
https://code.ros.org/lurker/thread/20130605.144934.e1521581.en.html)


On Wed, Jun 5, 2013 at 4:49 PM, Adolfo Rodríguez Tsouroukdissian <
> wrote:

>
>
>
> On Wed, Jun 5, 2013 at 4:09 PM, Mrinal Kalakrishnan <>wrote:
>
>> Let me correct that. We actually don't use a specific
>> "CartesianTrajectory" msg any more. Instead, we have a generic
>> "Trajectory" msg, which has a list of dimension names and
>> TrajectoryPoints - which makes it very similar to a JointTrajectory
>> msg. We then agree upon a naming scheme, like "r_hand_cart_x",
>> "r_hand_cart_force_x", and "r_hand_cart_gain_x" and so on. This allows
>> us to synchronize the execution of cartesian positions, forces and
>> gains (impedances), on multiple end-effectors if needed. We can also
>> send joint trajectories (or null-space joint posture trajectories)
>> through the same interface.
>>
>> Maybe this is not how you want the CartesianTrajectory msg to look,
>> but I just thought I'd mention where we ended up after a few
>> iterations, to have all the functionality we needed.
>>
>
> Interesting that you bring this up. The JointTrajectory and JointTolerance
> messages are in fact applicable to non-joint data, albeit their name.
> Furthermore, the de facto consumer of these messages, the
> JointTrajectoryActionController is largely a spline interpolator, and joint
> specifics appear in very localized places such as when interfacing with its
> inputs/outputs, or to determine whether a joint is continuous (by reading
> the URDF).
>
> It makes a lot of sense in my mind to have a more generic interpolator
> message and code that leverages it. As an obvious non-joint usecase, we
> have some RGB led arrays, and it would be just great to reuse a generic nD
> trajectory interpolator to control them.
>
> @Mrinal, does your implementation provide a mechanism for specifying
> custom interpolation functions for certain fields?; for example one might
> want to interpolate orientation data represented by quaternions, whose
> components are best not interpolated independently, but using slerp.
>
> Cheers,
>
> Adolfo.
>
>
>> - Mrinal
>>
>> On Wed, Jun 5, 2013 at 11:56 AM, Adolfo Rodríguez Tsouroukdissian
>> <> wrote:
>> >
>> >
>> >
>> > On Wed, Jun 5, 2013 at 11:39 AM, Mrinal Kalakrishnan <>
>> > wrote:
>> >>
>> >> We use a simple Cartesian trajectory msg internally at USC. The one
>> >> additional thing we have is accelerations at each
>> >> CartesianTrajectoryPoint. This allows us to use quintic splines in
>> >> cartesian space, for continuous accelerations between segments
>> >> (similar to the JointTrajectory msg).
>> >
>> >
>> > +1 for accelerations in the message specification. Also, the more
>> > parallelisms we can make with the JointTrajectory msg the better. If
>> you're
>> > used to the look& feel of one, it should be straightforward to use the
>> > other.
>> >
>> > Adolfo.
>> >>
>> >>
>> >> - Mrinal
>> >>
>> >> On Wed, Jun 5, 2013 at 3:53 AM, Jonathan Bohren
>> >> <> wrote:
>> >> >
>> >> > On Tue, Jun 4, 2013 at 9:09 PM, Edwards, Shaun M. <
>> >
>> >> > wrote:
>> >> >>
>> >> >> Are you aware if anybody is currently using a cartesian trajectory
>> >> >> (this
>> >> >> definition or any other)?
>> >> >
>> >> >
>> >> > There's an old repository of Stu's here:
>> >> >
>> >> >
>> https://bitbucket.org/sglaser/pr2_controllers_exp/src/02aa61c12b4b/jt_traj_controller_msgs/msg
>> >> >
>> >> > I think at one point there was something similar in ros_control or
>> >> > moveit,
>> >> > too. I put together a minimal cartesian trajectory message which was
>> >> > just an
>> >> > array of Poses and Twists with associated durations, but I think it
>> >> > should
>> >> > have some of the features that the aforementioned review describes.
>> >> > Other
>> >> > than that I don't know.
>> >> >
>> >> > --
>> >> > Jonathan Bohren
>> >> > Laboratory for Computational Sensing and Robotics
>> >> > http://dscl.lcsr.jhu.edu/People/JonathanBohren
>> >> >
>> >> >
>> >> > _______________________________________________
>> >> > ros-users mailing list
>> >> >
>> >> > https://code.ros.org/mailman/listinfo/ros-users
>> >> >
>> >> _______________________________________________
>> >> ros-users mailing list
>> >>
>> >> https://code.ros.org/mailman/listinfo/ros-users
>> >
>> >
>> >
>> >
>> > --
>> > Adolfo Rodríguez Tsouroukdissian
>> > Senior robotics engineer
>> >
>> > http://www.pal-robotics.com
>> >
>> > PAL ROBOTICS S.L
>> > c/ Pujades 77-79, 4º4ª
>> > 08005 Barcelona, Spain.
>> > Tel. +34.93.414.53.47
>> > Fax.+34.93.209.11.09
>> > Skype: adolfo.pal-robotics
>> > Facebook - Twitter - PAL Robotics YouTube Channel
>> >
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>
>



--
Adolfo Rodríguez Tsouroukdissian
Senior robotics engineer

http://www.pal-robotics.com

PAL ROBOTICS S.L
c/ Pujades 77-79, 4º4ª
08005 Barcelona, Spain.
Tel. +34.93.414.53.47
Fax.+34.93.209.11.09
Skype: adolfo.pal-robotics
Facebook <http://www.facebook.com/palrobotics1> -
Twitter<http://twitter.com/#%21/palrobotics>- PAL
Robotics YouTube Channel <http://www.youtube.com/user/PALRobotics>

AVISO DE CONFIDENCIALIDAD: Este mensaje y sus documentos adjuntos, pueden
contener información privilegiada y/o confidencial que está dirigida
exclusivamente a su destinatario. Si usted recibe este mensaje y no es el
destinatario indicado, o el empleado encargado de su entrega a dicha
persona, por favor, notifíquelo inmediatamente y remita el mensaje original
a la dirección de correo electrónico indicada. Cualquier copia, uso o
distribución no autorizados de esta comunicación queda estrictamente
prohibida.

CONFIDENTIALITY NOTICE: This e-mail and the accompanying document(s) may
contain confidential information which is privileged and intended only for
the individual or entity to whom they are addressed. If you are not the
intended recipient, you are hereby notified that any disclosure, copying,
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