[ros-users] move_arm tutorial - Moving the arm to a pose goal

Tue May 18 08:50:52 UTC 2010

On Tue, May 18, 2010 at 10:41 AM, Sachin Chitta <sachinc at willowgarage.com>wrote:

> Hi Adolfo,
>
> The move_arm node relies on your controller to report back that the
> final goal was achieved within the desired limits specified in the
> goal message. The problems you are having on the robot could be due to
> a steady-state error in your controller that prevents it from
> converging to the goal. It could also be because you are setting the
> convergence
> limits too tight. Try and make them a little more lenient.
>
> The first message that says "goal constraint violated" just refers to
> the fact that you are at the starting point and not at the goal yet. I
> will modify it to something more meaningful soon.
>

Good to know I can ignore this one.

>
> I am surprised by the report that the controllers do not converge in
> simulation. I will check this out and let you know what's going on
> soon. Are you using the latest versions of the simulator or are you
> using the boxturtle versions?
>

I'm using boxturtle, so I'm probably missing out on the more recent
additions.

>
> Please keep me updated about your experiences with using the stack on
> a different robot. We are currently in the process of updating and
> adding more tutorials dealing with the collision map and collision
> space representations and features for the stack.
>

Sure thing. I've been updating the tutorials and documentation whenever I
see an inconsistency with the code. Only minor things so far :)

Adolfo.

> Best Regards,
> Sachin
>
> 2010/5/18 Adolfo Rodríguez Tsouroukdissian <
> adolfo.rodriguez at pal-robotics.com>:
> >
> >
> > On Tue, May 18, 2010 at 9:46 AM, Ben Rudder <b.rudder382 at gmail.com>
> wrote:
> >>
> >> Hi All
> >>
> >> With the move_arm tutorials, I am always getting warnings that the
> current
> >> position violates the goal constraints, which is pretty obvious, but it
> >> often also misses a success message, or more frequently actually errors
> once
> >> it has reached the goal (in each of the four functions) with 'trajectory
> >> controller reports error'. Does this happen to everyone or should I
> check my
> >> system for missing things?
> >
> > I have seen similar behavior as well on a PR2 simulation (as per the
> > tutorials), the more common error being that the robot performs a motion
> > that appears successful from visual inspection, but then waits in the
> goal
> > configuration until it times out. I've also seen the warnings that the
> > current position violates the goal constraints, but not on the PR2, but
> on
> > one of our robots (so the error may be on my side and not on the ROS
> side).
> > I'm still getting to grips with the internals of the arm_navigation stack
> > (and making it work with our robots), and I wasn't going to post on the
> list
> > until I had a more concise description of the problems I'm seeing, but
> now
> > that you bring this up, I can confirm some of your issues.
> > I'll get back to the list if I find out something meaningful.
> >
> > Best,
> >
> > Adolfo
> >
> >>
> >> I am using the C++ versions.
> >>
> >> Also, in an effort to find out what was going wrong, I tried using the
> >> CHOMP planner, which I still have not managed to make function at all
> for
> >> planning...
> >>
> >> Thanks in advance
> >> Ben
> >>
> >> On Tue, May 18, 2010 at 6:42 AM, Advait Jain <advait at cc.gatech.edu>
> wrote:
> >>>
> >>> Thanks Sachin.
> >>>
> >>> In case other people are also interested in using move_arm from
> >>> python, my python equivalent for the MoveArmPoseGoalComplex
> >>> tutorial is at -
> >>>
> >>>
> >>>
> http://code.google.com/p/gt-ros-pkg/source/browse/trunk/hrl/hrl_simple_arm_goals/src/hrl_simple_arm_goals/move_arm_pose_goal.py
> >>>
> >>> It does the same thing as the C++ tutorial (in simulation).
> >>>
> >>> Advait
> >>>
> >>>
> >>> On Mon, May 17, 2010 at 1:12 AM, Sachin Chitta <
> sachinc at willowgarage.com>
> >>> wrote:
> >>> > Hi Advait,
> >>> >
> >>> > Yes, the helper functions are only in C++ right now. You will be able
> >>> > to address the move_arm node directly from both C++ or python using
> >>> > the underlying action API. Have a look at this tutorial for how you
> >>> > can specify pose goals directly without needing the extra helper
> >>> > functions
> >>> > (http://www.ros.org/wiki/move_arm/Tutorials/MoveArmPoseGoalComplex)
> >>> >
> >>> >  I don't have python tutorials but you should be able to follow the
> >>> > python tutorials for actions
> >>> >
> >>> > (
> http://www.ros.org/wiki/actionlib_tutorials/Tutorials/Writing%20a%20Simple%20Action%20Client%20%28Python%29
> ).
> >>> >
> >>> > I will be happy to accept a python version of the helper functions
> >>> > though :-)
> >>> >
> >>> > Sachin
> >>> >
> >>> > On Sun, May 16, 2010 at 8:37 PM, Advait Jain <advait at cc.gatech.edu>
> >>> > wrote:
> >>> >> I am trying to replicate the functionality of this tutorial from a
> >>> >> python node -
> >>> >> http://www.ros.org/wiki/move_arm/Tutorials/MoveArmPoseGoal
> >>> >>
> >>> >> It isn't clear to me if there is a python equivalent for this
> >>> >> function:
> >>> >> move_arm_msgs::addGoalConstraintToMoveArmGoal(desired_pose,goalA);
> >>> >>
> >>> >> Am I missing something or do I need to write my own python
> >>> >> versions for addGoalConstraintToMoveArmGoal (C+ code in
> >>> >> move_arm_msgs/utils.h) and
> >>> >> poseConstraintToPositionOrientationConstraints
> >>> >> (motion_planning_msgs/convert_messages.h) to use the
> >>> >> move_arm package from python?
> >>> >>
> >>> >>
> >>> >> Advait
> >>> >> _______________________________________________
> >>> >> ros-users mailing list
> >>> >> ros-users at code.ros.org
> >>> >> https://code.ros.org/mailman/listinfo/ros-users
> >>> >>
> >>> >
> >>> >
> >>> >
> >>> > --
> >>> > Sachin Chitta
> >>> > Research Scientist
> >>> > Willow Garage
> >>> > _______________________________________________
> >>> > ros-users mailing list
> >>> > ros-users at code.ros.org
> >>> > https://code.ros.org/mailman/listinfo/ros-users
> >>> >
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> >>
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> >
> >
> >
> > --
> > Adolfo Rodríguez Tsouroukdissian, Ph. D.
> >
> > Robotics engineer
> > PAL ROBOTICS S.L
> > http://www.pal-robotics.com
> > Tel. +34.93.414.53.47
> > Fax.+34.93.209.11.09
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>
> --
> Sachin Chitta
> Research Scientist
> Willow Garage
>
>
>
> --
> Sachin Chitta
> Research Scientist
> Willow Garage
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