[ros-users] reactive_grasp, compliant_close: not using the database

Tue Mar 8 15:27:37 UTC 2011

Dear Matei,

I switched to unstable and added the overlay you sent. I'm now getting the
pre / grasp posture in the ReactiveGrasp. I just need to modify my code to
use it now :) Thanks!

Cheers,

Ugo

On Tue, Mar 8, 2011 at 12:51 AM, Matei Ciocarlie <matei at willowgarage.com>wrote:

> Hi Ugo,
>
> We've added the pre-grasp and grasp posture to the ReactiveGrasp
> action goal, it will come out in the next release. However, we
> probably won't be able to release this for at least a few days. Can
> you get on to trunk? A rosinstall file you could use is:
>
>
> https://code.ros.org/svn/wg-ros-pkg/branches/trunk_cturtle/rosinstall_files/cturtle/pr2_manipulation-cturtle-pr2all-overlay-devel.rosinstall
>
> Matei
>
> On Fri, Mar 4, 2011 at 12:55 AM, Ugo Cupcic <ugo at shadowrobot.com> wrote:
> > Hi,
> >
> > Thanks for your answers.
> >
> > Having pre_grasp_posture and grasp_posture would in the
> ReactiveActionGoal
> > would be the best for me. I'm using unstable (and I'll be happy to make
> an
> > overlay if you want me to test one branches).
> >
> > Matei, I already implemented the first approach you described, but as a
> more
> > "static" approach: the approach is just checking against collisions when
> > computing the path it's going to take, then the hand is closing from
> > pre_graps_posture to grasp_posture and that's it. No going back if we
> have
> > some contact, etc... I was assuming that it was meant to be like this in
> > this case, so as to have an easy to use and relatively direct approach to
> > grasping an object. That's why I wanted to implement the reactive grasp /
> > approach separately, as I saw it in your packages.
> >
> > Cheers,
> >
> > Ugo
> >
> > On Thu, Mar 3, 2011 at 10:01 PM, Kaijen Hsiao <kaijenhsiao at gmail.com>
> wrote:
> >>
> >> Hi Ugo,
> >> Would it be sufficient for your purposes to add
> >> sensor_msgs/JointState pre_grasp_posture
> >> and
> >> sensor_msgs/JointState grasp_posture
> >> to the ReactiveActionGoal?
> >> (If you want, I can also make a new CompliantCloseAction that contains
> >> these two things, so you can parallel our code--I've meant to use such
> >> a thing for our code for awhile even, but there was never a need for
> >> it until now.  We are likely to want such a thing for future arm/hand
> >> ports, anyway.)
> >> Are you using the trunk or Diamondback or unstable version of our
> >> code, or something else?
> >>
> >> -Kaijen
> >>
> >>
> >> On Thu, Mar 3, 2011 at 9:41 AM, Matei Ciocarlie <matei at willowgarage.com
> >
> >> wrote:
> >> > Hi Ugo,
> >> >
> >> > There are two things that the hand needs to do: move from pre-grasp to
> >> > grasp, and then close the fingers. Our nomenclature is definitely less
> >> > than ideal, they are both referred to as "grasp" in parts of the
> >> > pipeline...
> >> >
> >> > Reactive grasping as defined by the ReactiveGrasp.action actually
> >> > combines both. It should be called "ReactiveApproachAndGrasp" or
> >> > something in the vicinity... The implementation we have is PR2
> >> > specific for both the approach and the finger closing part. You are
> >> > right, as a module that is (also) responsible for closing the fingers,
> >> > it should take in the grasp posture as well (not just the pose).
> >> >
> >> > When not using reactive grasping, we actually do split it into two.
> >> > First, open-loop inerpolated IK is done to get the hand from pre-grasp
> >> > to grasp. Then, a call to a GraspHandPostureExecution.action is made.
> >> > This call does contain all the info about the grasp .We have a PR2
> >> > implementation that simply closes the fingers in response to that call
> >> > in the
> >> > pr2_gripper_grasp_controller package.
> >> >
> >> > You could write a sh_gripper_grasp_controller package that responds to
> >> > GraspHandPostureExecution goals, either in a reactive or non-reactive
> >> > way. This would only refer to the finger closing part (not the
> >> > approach) but you could implement all the behaviors that you mentioned
> >> > in your email.
> >> >
> >> > Alternatively, if you prefer a "ReactiveApproachAndGrasp" all in one
> >> > shot, we would indeed need to modify the ReactiveGrasp call to contain
> >> > the grasp posture. That also seems like a reasonable thing to do.
> >> >
> >> > Best,
> >> > Matei
> >> >
> >> > On Thu, Mar 3, 2011 at 4:16 AM, Ugo Cupcic <ugo at shadowrobot.com>
> wrote:
> >> >> Hi,
> >> >>
> >> >> In the reactive_grasp, the compliant_close function is not using the
> >> >> grasp
> >> >> posture from the database. I understand that it can work for the
> >> >> gripper,
> >> >> but for a more complex hand such as ours, I believe it would be a
> good
> >> >> start
> >> >> to have access to this grasp posture here.
> >> >>
> >> >> What I wanted to do in the reactive grasp, was (as a first approach):
> >> >>  - interpolate between current posture of the hand and "closed
> posture"
> >> >> (read from the database), while checking for contacts.
> >> >>  - when I have a contact on one finger, I stop moving this finger.
> >> >>  - when all fingers are touching lightly the object, close until
> force
> >> >> > X
> >> >>
> >> >> Is it not the purpose of the reactive_grasp server? Should I do that
> in
> >> >> my
> >> >> standard static grasp? Do I need to query my databases in my
> >> >> reactive_grasp
> >> >> node to get the list of possible grasps, or would it be possible to
> >> >> extend
> >> >> the content of the ReactiveGraspGoal message, so as to include this
> >> >> information?
> >> >>
> >> >> I hope my questions make sense, otherwise feel free to ask me for
> more
> >> >> info!
> >> >>
> >> >> Cheers,
> >> >>
> >> >> Ugo
> >> >>
> >> >> --
> >> >> Ugo Cupcic | Shadow Robot Company | ugo at shadowrobot.com
> >> >> Software Engineer | 251 Liverpool Road |
> >> >> need a Hand? | London N1 1LX | +44 20 7700 2487
> >> >> http://www.shadowrobot.com/hand/ @shadowrobot
> >> >>
> >> >>
> >> >> _______________________________________________
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> >> >>
> >> >>
> >> >
> >> >
> >> >
> >> > --
> >> > Matei Ciocarlie
> >> > Research Scientist
> >> > Willow Garage Inc.
> >> > 650-475-9780
> >> > _______________________________________________
> >> > ros-users mailing list
> >> > ros-users at code.ros.org
> >> > https://code.ros.org/mailman/listinfo/ros-users
> >> >
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> >
> >
> >
> > --
> > Ugo Cupcic | Shadow Robot Company | ugo at shadowrobot.com
> > Software Engineer | 251 Liverpool Road |
> > need a Hand? | London N1 1LX | +44 20 7700 2487
> > http://www.shadowrobot.com/hand/ @shadowrobot
> >
> >
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> > ros-users at code.ros.org
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> >
> >
>
>
>
> --
> Matei Ciocarlie
> Research Scientist
> Willow Garage Inc.
> 650-475-9780
>

-- 
Ugo Cupcic | Shadow Robot Company | ugo at shadowrobot.com
Software Engineer | 251 Liverpool Road |
need a Hand? | London N1 1LX | +44 20 7700 2487
http://www.shadowrobot.com/hand/ @shadowrobot
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