[ros-users] cartesian trajectories

Wed Jun 5 14:58:45 UTC 2013

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 <
adolfo.rodriguez at pal-robotics.com> wrote:

>
>
>
> On Wed, Jun 5, 2013 at 4:09 PM, Mrinal Kalakrishnan <kalakris at usc.edu>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
>> <adolfo.rodriguez at pal-robotics.com> wrote:
>> >
>> >
>> >
>> > On Wed, Jun 5, 2013 at 11:39 AM, Mrinal Kalakrishnan <kalakris at usc.edu>
>> > 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
>> >> <jonathan.bohren at gmail.com> wrote:
>> >> >
>> >> > On Tue, Jun 4, 2013 at 9:09 PM, Edwards, Shaun M. <sedwards at swri.org
>> >
>> >> > 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
>> >> >
>> >> >
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>> >
>> >
>> >
>> > --
>> > Adolfo Rodríguez Tsouroukdissian
>> > Senior robotics engineer
>> > adolfo.rodriguez at pal-robotics.com
>> > http://www.pal-robotics.com
>> >
>> > PAL ROBOTICS S.L
>> > c/ Pujades 77-79, 4º4ª
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-- 
Adolfo Rodríguez Tsouroukdissian
Senior robotics engineer
adolfo.rodriguez at pal-robotics.com
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
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